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  • 1
    Electronic Resource
    Electronic Resource
    Information frameworks for conceptual engineering design (1994)
    Springer
    Engineering with computers 10 (1994), S. 22-32 
    Details
    ISSN: 1435-5663
    Keywords: Conceptual design ; Database ; Frameworks ; Information management
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract An information modeling approach is used to gain an understanding of the information and decision content of conceptual engineering design. Information frameworks are presented that attempt to represent the key decisions made during conceptual design. Elements of the frameworks are derived from results from design theory and methodology and decision theory. Using a number of products, the frameworks are demonstrated in simulated design situations. The models provide an explicit, generic and consistent perspective for identifying the information content of conceptual designs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01206537
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  • 2
    Electronic Resource
    Electronic Resource
    Aluminium electrolytic cells: A computer simulator for training and supervision (1994)
    Springer
    Engineering with computers 10 (1994), S. 12-21 
    Details
    ISSN: 1435-5663
    Keywords: Aluminium electrolysis ; Expert systems ; Modelling ; Simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract A workstation-based simulator of an aluminium electrolytic cell has been constructed. A mathematical model of the cell is integrated with a database and a knowledge base, and the simulator serves as a tool for the training of personnel and for research related to cell dynamics and cell control. When used in conjunction with an expert system, it provides a powerful decision-making tool or an efficient supervisory system. The mathematical model, the simulator itself, the user environment, the interactive simulation procedure as well as examples of the use of the simulator are presented in detail.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01206536
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  • 3
    Electronic Resource
    Electronic Resource
    A review of automatic dimensioning and tolerancing schemes (1994)
    Springer
    Engineering with computers 10 (1994), S. 63-80 
    Details
    ISSN: 1435-5663
    Keywords: Dimensioning ; Tolerancing ; Variational geometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Dimensioning and tolerancing are very important issues in product design and manufacture. This paper gives a survey and review of the current state-of-the-art solutions to the problem of finding a meaning for dimensions and tolerances. Dimensioning and tolerancing in current engineering practices and researches in these topics are also discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01200178
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  • 4
    Electronic Resource
    Electronic Resource
    A new programming paradigm for engineering design software (1994)
    Springer
    Engineering with computers 10 (1994), S. 95-111 
    Details
    ISSN: 1435-5663
    Keywords: Engineering design ; Formal ; Functional programming ; Object orientation ; Programming language
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Currently available programming and database systems are insufficient for engineering applications. The authors contend that a logical progression from a formal conceptual model of the engineering domain to a computational model will lead to new programming paradigms capable of directly supporting engineering applications in a rigorous, concise manner. A formal domain model devised by the authors, theHybrid Model (HM) of design information, is briefly introduced. It is an extension of axiomatic set theory and is discussed in detail elsewhere. HM forms the basis ofDesigner, a prototype-based object-oriented programming language supporting a signature-based canonical message-passing mechanism and multiple inheritance. Designer is implemented using the Scheme programming language. Because Designer satisfies a formal conceptual model, and because it is based on a formally specified language, its robustness and logical validity are superior to those of other languages not founded on formal principles. Designer combines concepts of functional and object-oriented programming to provide the formal rigor and flexibility to capture the complex and strongly interrelated information that designers use. Examples demonstrate how Designer represents design information. The results of the authors' research indicate that Designer can capture design information (including aspects of functional requirements and design intent) effectively and efficiently.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01200180
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  • 5
    Electronic Resource
    Electronic Resource
    Rule-based design of a material processing component (1994)
    Springer
    Engineering with computers 10 (1994), S. 81-94 
    Details
    ISSN: 1435-5663
    Keywords: Design ; Expert system ; Extension ; Material processing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract The main thrust of this research is in developing aknowledge-based system for the design of components for a material processing system. In particular, this paper concentrates on developing methodologies forinitial design andredesign in a quantitative and qualitative format. A die for plastic extrusion has been selected as the subject material processing component. A design algorithm using best first heuristic search and expert knowledge, both in procedural and declarative form, is the core of the scheme. Apart from this expert, the suggestedselection procedure for candidate design is also seen to accelerate the design scheme. The methodologies presented enableefficient design of the component. Some generality has been accomplished by the implementation of the techniques to dies of different cross-sectional shapes. The software is written inLisp within an object-oriented software package using analysis modules written in C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01200179
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  • 6
    Electronic Resource
    Electronic Resource
    Announcement (1994)
    Springer
    Engineering with computers 10 (1994), S. 124-124 
    Details
    ISSN: 1435-5663
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01200182
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  • 7
    Electronic Resource
    Electronic Resource
    A tandem architecture for cooperating knowledge-based concurrent engineering systems (1994)
    Springer
    Engineering with computers 10 (1994), S. 112-123 
    Details
    ISSN: 1435-5663
    Keywords: Agent-based framework ; Architecture ; Concurrent engineering ; Cooperating expert systems ; Tandem integration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract This paper proposes a tandem architecture for cooperating heterogeneous expert systems. Two levels of meta and working expert systems are involved. The working-level expert systems (W-ES), which may be implemented in their own computational environments and in private proof languages, are mainly for application computations. The meta-level expert systems (M-ES), using a common argument language, are mainly responsible for cooperation. The prototype AGENTS system is described for constructing M-ES. Interaction among W-ES has been transformed into two forms: communication between M-ES through ordinary AGENTS messages and communication between M-ES and the corresponding W-ES using the Deductive Inference Language (DIL). DIL predicates are provided for defining DIL: messages, actuators and converters for interpreting DIL queries and instantiating variables. By this approach, stand-alone capability of infividual systems is retained at the working-level and cooperation is achieved effectively with minimum embellishment at the meta-level.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01200181
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  • 8
    Electronic Resource
    Electronic Resource
    A proposed structure for a rule-based description of parametric forms (1994)
    Springer
    Engineering with computers 10 (1994), S. 155-161 
    Details
    ISSN: 1435-5663
    Keywords: Constrains ; Geometric ; Parametric ; Product form
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Much work has been carried out on the creation of protocols for the exchange of data between CAD systems, but very little on the transfer of knowledge. The knowledge behind the development of a product is vital if modifications and adaptations are to be made within a concurrent development environment. Current CAD systems only contain a limited level of product knowledge through user-defined parametric structures. It is the underlying relationships in these programs that need to be communicated between systems, rather than the form of their individual programming languages. A generic structure is proposed that is able to handle both the current level of parametric programming and is suited to the resolution of conflict through the use of constraint modelling procedures. The structure of a parametric description is described and decomposed into its fundamental components. These components are then re-formed within a truth maintenance structure to allow a transfer protocol to be created. The derived protocol structure is then demonstrated on a number of simple examples.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01198741
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  • 9
    Electronic Resource
    Electronic Resource
    Concurrent iterative design and the integration of finite element analysis results (1994)
    Springer
    Engineering with computers 10 (1994), S. 245-257 
    Details
    ISSN: 1435-5663
    Keywords: Design methodology ; Iterative design ; Concurrent design ; Features ; Form templates ; Finite element analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract To help foster concurrency in engineering design, methodologies are needed to support the interpretation and abstraction of numerical simulation results for design modification purposes. A methodology is presented in this paper for the integration of continuum-based numerical simulations into a computational system for concurrent design of mechanical components. The technique involves conversion of low-level numerical data, such as that obtained by finite element analysis, into high-level symbolic representations calledform templates. The form templates are based onrudimentary features which carry meaningful qualitative descriptions abstracted from either manufacturing and/or functional numerical simulations. The form templates are superimposed on the design's primary representation in the solid modeler to facilitate the cognitive mapping of concurrent destructive or constructive solid modeling features for design modifications. Examples are presented to demonstrate the methodology.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01202369
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  • 10
    Electronic Resource
    Electronic Resource
    Curves and surfaces for computer aided design usingC 2 rational cubic splines (1995)
    Springer
    Engineering with computers 11 (1995), S. 94-102 
    Details
    ISSN: 1435-5663
    Keywords: Rational cubic ; Bernstein-Bézier ; Shape control ; Tension
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract This paper is concerned with the problem of fitting curves and surfaces, for computer aided design (CAD), via an ordered set of control points, so that the result is satisfactory for the user's needs. Piecewise rational functions with cubic numerator and quadratic denominator are used in the construction of the scheme, in such a way that the descriptions of the parameters control the shape of the picture in the desired area. A general solution is obtained for points inN-space, although the scheme is only meaningful in the cases whereN=2 andN=3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01312203
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  • 11
    Electronic Resource
    Electronic Resource
    Data fusion for adaptive control in manufacturing: Impact on engineering information models (1995)
    Springer
    Engineering with computers 11 (1995), S. 145-156 
    Details
    ISSN: 1435-5663
    Keywords: Database ; Date fusson ; Date model ; Information architecture ; Information model ; Manufacturing ; Sensors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Data fusion is the integration and analysis of data from multiple sensors to develop a more accurate understanding of a situation and determine how to respond to it. Although data fusion can be applied in many situations, this paper focuses on its application to manufacturing and how it changes some of the more traditional, less adaptive information models that support the design and manufacturing functions. The paper consists of four parts. The first section explains what data fusion is and its impact on manufacturing. The second section describes what an information system architecture is and explains the natural language-based information modeling methodology used by this research project. The third section identifies the major design and manufacturing functions, reviews the information models required to support them, and then shows how these models must be extended to support data fusion. The fourth section discusses the future directions of this work.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01271280
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  • 12
    Electronic Resource
    Electronic Resource
    Modeling evolving product data for concurrent engineering (1995)
    Springer
    Engineering with computers 11 (1995), S. 167-172 
    Details
    ISSN: 1435-5663
    Keywords: Concurrent engineering ; Configuration management ; Data model ; Design Process ; Engineering data management ; Product data management
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract In order to make the traditional product structure tree representation amenable to concurrent engineering relationships likeperspective-of anddependent-on have to be added to the essentialpart-of relationship. Complex data can be held in proprietary formats, while simple data will be in a common representation for direct access by diverse disciplines. Coordination among team members in a project can be carried out using such a model. Besides, a virtually unified view of all the data is possible, though they may lie in distributed and heterogeneous data bases. A very necessary characteristic of such a model is that its time evolution should be easy to represent in order to reflect the dynamic nature of product development, where the model itself, and not merely the data values change. Managing versions is also facilitated by the comprehensive structure of the Unified Product Data Model (UPDM).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01271282
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  • 13
    Electronic Resource
    Electronic Resource
    Information management for integrated design environments (1995)
    Springer
    Engineering with computers 11 (1995), S. 227-245 
    Details
    ISSN: 1435-5663
    Keywords: Conceptual design ; Design process ; Design studies ; Engineering information systems ; Product data
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract This paper identifies requirements for an engineering design information management system. Future CAD systems must support a wide range of activities — such as definition, manipulation and analyses of complex product information models. These models represent not only conventional data associated with current CAD applications, but also design information characterizing the correlations between the requirements, functions, behaviors and physical form of the product. Such functionality is important for both the individual designer and the design organization, as the need to manage information as a corporate asset is becoming a critical component of business strategy. This paper explores these needs using two design studies. The first study illustrates some major concepts relative to non-routine design activities, while the second study focuses on the routine design activities relative to organization interactions. These studies were used to elicit high level requirements which serve as the basis for the development of prototype software systems. These prototypes are briefly introduced here.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01208816
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  • 14
    Electronic Resource
    Electronic Resource
    An object design framework for structural engineering (1995)
    Springer
    Engineering with computers 11 (1995), S. 213-226 
    Details
    ISSN: 1435-5663
    Keywords: Communication channel ; Communication path ; Data attribute ; Design object ; Method group ; Object-oriented ; Receiving interface ; Relationship ; Relationship attribute ; Sending method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Object-oriented principles have introduced several useful concepts for developing complex software systems. As a result, several methodologies have been suggested for the overall design of software systems based on these concepts. Methodologies and frameworks for designing objects that are to be part of the software systems are currently lacking. This paper proposes anobject design framework andmethodology, which utilizes the object-oriented concepts, for planning, organizing and designing structural engineering design objects. Design objects in an integrated structural engineering system are complex and often related to each other in various different ways. The paper also identifies several important relationships among structural engineering design objects. These relationships serve as communication channels through wich design objects send messages to and receive responses from each other. Several examples, drawn from reinforced concrete structures, will be presented to demonstrate the object design methodology and to illustrate how the framework is effective in reducing the complexity of design objects in an integrated structural engineering system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01208815
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  • 15
    Electronic Resource
    Electronic Resource
    Verification of an active control system using temporal process algebra (1996)
    Springer
    Engineering with computers 12 (1996), S. 46-61 
    Details
    ISSN: 1435-5663
    Keywords: Active structural control ; Calculus of communicating systems (CCS) ; Concurrency workbench ; Modechart ; Real-time systems ; Simulation ; Temporal CCS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract In this paper we describe complementary approaches that can be used to ensure the reliability of real-time systems, such as those used in active structural control systems. These approaches include both model-checking and simulation, and are based on a temporal process algebra. We combine these formal methods with a high-level, graphical modeling technique, Modechart, to specify an active structural control system consisting of several processors. Timing requirements on the system are specified and verified with a combination of process algebraic models and modal logic, and various simulation concepts are described for debugging models and for gaining insight into system behavior.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01200261
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  • 16
    Electronic Resource
    Electronic Resource
    Adaptive mesh refinement using piecewise-linear shape functions based on the blending function method (1996)
    Springer
    Engineering with computers 12 (1996), S. 84-93 
    Details
    ISSN: 1435-5663
    Keywords: Adaptive mesh refinement ; Finite element method ; Mesh generation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Use of quadrilateral elements for finite element mesh refinement can lead either to so-called ‘irregular’ meshes or the necessity of adjustments between finer and coarser parts of the mesh necessary. In the case of ‘irregular’ meshes, constraints have to be introduced in order to maintain continuity of the displacements. Introduction of finite elements based on blending function interpolation shape functions using piecewise boundary interpolation avoids these problems. This paper introduces an adaptive refinement procedure for these types of elements. The refinement is anh-method. Error estimation is performed using the Zienkiewicz-Zhu method. The refinement is controlled by a switching function representation. The method is applied to the plane stress problem. Numerical examples are given to show the efficiency of the methodology.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01299394
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  • 17
    Electronic Resource
    Electronic Resource
    Parallel three-dimensional mesh generation on distributed memory MIMD computers (1996)
    Springer
    Engineering with computers 12 (1996), S. 94-106 
    Details
    ISSN: 1435-5663
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract This paper discusses the development of an automatic mesh generation technique designed to operate effectively on multiple instruction multiple data (MIMD) parallel computers. The meshing approach is hierarchical, that is, model entities are meshed after their boundaries have been meshed. Focus is on the region meshing step. An octree is constructed to serve as a localization tool and for efficiency. The tree is also key to the efficient parallelization of the meshing process since it supports the distribution of load to processors. The parallel mesh generation procedure repartitions the domain to be meshed and applies on processor face removals until all face removals with local data have been performed. The portion of the domain to be meshed remaining is dynamically repartitioned at the octant level using an Inertial Recursive Bisection method and local face removals are reperformed. Migration of a terminal octant involves migration of the octant data and the octant's mesh faces and/or mesh regions. Results show relatively good speed-ups for parallel face removals on small numbers of processors. Once the three-dimensional mesh has been generated, mesh regions may be scattered across processors. Therefore, a final dynamic repartitioning step is applied at the region level to produce a partition ready for finite element analysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01299395
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  • 18
    Electronic Resource
    Electronic Resource
    Adaptive finite element procedures in elasticity and plasticity (1996)
    Springer
    Engineering with computers 12 (1996), S. 120-141 
    Details
    ISSN: 1435-5663
    Keywords: Discontinuous Galerkin ; Error estimation adaptivity ; Postprocessing ; Superconvergence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract The paper discusses error estimation and h-adaptive finite element procedures for elasticity and plasticity problems. For the spatial discretization error, an enhanced Superconvergent Patch Recovery (SPR) technique which improves the error estimation by including fulfillment of equilibrium and boundary conditions in the smoothing procedure is discussed. It is known that an accurate error estimation on an early stage of analysis results in a more rapid and optimal adaptive process. It is shown that node patches and element patches give similar quality of the postprocessed solution. For dynamic problems, a postprocessed type of error estimate and an adaptive procedure for the semidiscrete finite element method are discussed. It is shown that the procedure is able to update the spatial mesh and the time step size so that both spatial and time discretization errors are controlled within specified tolerances. A time-discontinuous Galerkin method for solving the second-order ordinary differential equations in structural dynamics is also presented. Many advantages of the new approach such as high order accuracy, possibility to filter effects of spurious modes and convenience to apply adaptive analysis are observed. For plasticity problems, some recent work that improved plastic strains and plastic localization is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01299397
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  • 19
    Electronic Resource
    Electronic Resource
    Two and three-quarter dimensional meshing facilitators (1996)
    Springer
    Engineering with computers 12 (1996), S. 144-154 
    Details
    ISSN: 1435-5663
    Keywords: Automatic mesh generation ; Mesh control ; Mapped meshing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract This paper presents generated enhancements for robust ‘two and three-quarter dimensional meshing’, including: (1) automated interval assignment by integer programming for submapped surfaces and volumes, (2) surface submapping, and (3) volume submapping. An introduction to the simplex method, an optimization technique of integer programming, is presented. Simplification of complex geometry is required for the formulation of the integer programming problem. A method of ‘i-j unfolding’ is defined which explains how irregular geometry can be realigned into a simplified form that is suitable for submap interval assignment solutions. Also presented is the processes by which submapping eliminates the decomposition of surface geometry, through a pseudodecomposition process, producing suitable mapped meshes. The process of submapping involves the creation of ‘interpolated virtual edges’, user defined ‘vertex types’ and ‘i-j-k space’ traversals. The creation of ‘interpolated virtual edges’ is the method by which submapping automatically subdivides surface geometry. The ‘interpolated virtual edge’ is formulated according to an interpolation scheme using the node discretization of curves on the surface. User defined ‘vertex types’ allow direct user control of surface decomposition and interval assignment by modifying ‘i-j-k space’ traversals. Volume submapping takes the geometry decomposition to a higher level by using ‘mapped virtual surfaces’ to eliminate decomposition of complex volumes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01198730
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  • 20
    Electronic Resource
    Electronic Resource
    Automatic, parallel and fault tolerant mesh generation from CAD (1996)
    Springer
    Engineering with computers 12 (1996), S. 178-185 
    Details
    ISSN: 1435-5663
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract HEXAR, a new software product developed at Cray Research, Inc., automatically generates good quality meshes directly from surface data produced by computeraided design (CAD) packages. The HEXAR automatic mesh generator is based on a proprietary and parallel algorithm that relies on pattern recognition, local mesh refinement and coarsening, and variational mesh smoothing techniques to create all-hexahedral volume meshes. HEXAR generates grids two to three orders of magnitude faster than current manual approaches. Although approximate by design, the resulting meshes have qualities acceptable by many commercial structural and CFD (computational fluid dynamics) software. HEXAR turns mesh generation into an automatic process for most commercial engineering applications.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01198733
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  • 21
    Electronic Resource
    Electronic Resource
    Progress in grid generation via the advancing front technique (1996)
    Springer
    Engineering with computers 12 (1996), S. 186-210 
    Details
    ISSN: 1435-5663
    Keywords: Finite elements ; Grid generation ; Tetrahedra ; Unstructured grids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract We describe recent extensions and improvements to the advancing front grid generation technique. These improvements target a range of applicability, speed and user friendliness. The range of applicability is enlarged by the ability to produce volumetric grids around thin surfaces (such as shells, membranes, fabrics or surfaces with cusps), the generation of high aspect ratio grids for Navier-Stokes applications, the generation of higher order triangular and tetrahedral elements, and the generation of quadrilateral and hexahedral elements. Speed improvements are the result of reduced search overheads, as well as vectorization and parallelization. User friendliness is enhanced by the ability to grid directly discrete data and simpler ways of specifying the desired element size and shape in space. Numerous examples are included that demonstrate the versatility and maturity that advancing front grid generators have achieved.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01198734
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  • 22
    Electronic Resource
    Electronic Resource
    Development of an information model for composites design data (1997)
    Springer
    Engineering with computers 13 (1997), S. 48-64 
    Details
    ISSN: 1435-5663
    Keywords: Composite materials ; Conceptual modeling ; Database design ; Fiber-reinforced plastics ; information modeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Material properties data, particularly those of advanced composite materials such as fiber-reinforced plastics, provides a very complex domain which is difficult to computerize. As a foundational activity supporting the development of material property databases, we have examined and modeled the data contained within this large, diverse, and intricate domain. Our primary objective was to gain a better understanding of the data involved in this system and their transformation and use. We examined the life cycle of a fiber-reinforced composite material, from a raw material to a manufactured product, focusing on the various applications which require and/or supply materials data and the types of materials data which must be included. A high-level information model was created to illustrate the overall picture of composite materials data which emerged from this analysis. This model provides a global view of the data encompassed in the domain of composite materials, and forms the basis of a formal conceptual model from which databases may be developed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01201860
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    A data management model for collaborative design in a CAD environment (1997)
    Springer
    Engineering with computers 13 (1997), S. 65-86 
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    ISSN: 1435-5663
    Keywords: Collaborative design ; Version control ; Configuration scheme ; Change management
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract This paper presents a data management model to support collaborative design. More specifically, it addresses the storing and managing of changes among designers in a multidisciplinary design project. We propose a three-layered model ofversions, assemblies, andconfigurations. Versions maintain evolving descriptions of primitive entities within a single discipline.Assemblies integrate component instances to describe more complex entities, as well as designs within individual disciplines.Configurations provide a framework to represent an overall project design which is composed of designs from the participating disciplines. We apply a concept ofequivalent operations for developing operators that store, detect and manage changes among versions of a primitive design entity. The close coupling of the version, assembly, and configuration layers enables computed version changes to be recursively combined to characterize changes at the assembly and configuration levels. This applies for both project coordination throughasynchronous communication of changes among designers, and project monitoring through systematic tracking of evolving project descriptions. This paper also presents an implementation of the data management model in a CAD paradigm. We use a simple multidisciplinary facility design example to demonstrate the change management capabilities of the proposed model. This example has been tested on a prototype implementation in an AUTOCAD environment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01350751
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    Using objects to handle complexity in finite element software (1997)
    Springer
    Engineering with computers 13 (1997), S. 99-111 
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    ISSN: 1435-5663
    Keywords: Finite elements ; Object oriented methods
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Engineering software is becoming ever more complex. Finite element programs have sophisticated graphical input and output facilities, and are increasingly required to be linked to other software such as CAD or databases. The paper shows how an object oriented approach to finite element programming can be used to handle this complexity. This requires an approach that is very different from that adopted in more traditional programming. A foundation finite element class system is developed. This represents the essential data structure of the main finite element classes. It is then shown how this system can be used in a graphical model of two dimensional structures. The finite element system imposed no constraints on the development of the graphical model, yet could still be used easily. An important feature is that the nodes and elements are distributed around the graphical model, rather than being held centrally. For instance nodes may belong to points or lines of the graphical model. This means that the data structure used in the program more closely matches the way that the user of the program is likely to think.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01350753
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    Elimination of the adverse effects of small model features by the local modification of automatically generated meshes (1997)
    Springer
    Engineering with computers 13 (1997), S. 134-152 
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    ISSN: 1435-5663
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Issues related to the automated identification and elimination of the adverse influence of small geometric model features on the quality of automatically generated meshes, using local mesh modification operators, are addressed. The definition of mesh validity with respect to the geometric model is extended to include multiple mesh entity classifications. Checks based on mesh topology are used to ensure no dimensional reductions in the locally modified mesh. Example geometric models of varied complexity containing small geometric features are used to demonstrate the ability of presented procedures to improve mesh quality in terms of aspect ratio and small angle metrics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01221211
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    Local refinement of three-dimensional finite element meshes (1997)
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    Engineering with computers 13 (1997), S. 165-174 
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    ISSN: 1435-5663
    Keywords: Mesh refinement ; Mixed element meshes ; Unstructured meshes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Mesh refinement is an important tool for editing finite element meshes in order to increase the accuracy of the solution. Refinement is performed in an iterative procedure in which a solution is found, error estimates are calculated, and elements in regions of high error are refined. This process is repeated until the desired accuracy is obtained. Much research has been done on mesh refinement. Research has been focused on two-dimensional meshes and three-dimensional tetrahedral meshes ([1] Ning et al. (1993) Finite Elements in Analysis and Design, 13, 299–318; [2] Rivara, M. (1991) Journal of Computational and Applied Mathematics 36, 79–89; [3] Kallinderis; Vijayar (1993) AIAA Journal,31, 8, 1440–1447; [4] Finite Element Meshes in Analysis and Design,20, 47–70). Some research has been done on three-dimensional hexahedral meshes ([5] Schneiders; Debye (1995) Proceedings IMA Workshop on Modelling, Mesh Generation and Adaptive Numerical Methods for Partial Differential Equations). However, little if any research has been conducted on a refinement algorithm that is general enough to be used with a mesh composed of any three-dimensional element (hexahedra, wedges, pyramids, and/or retrahedra) or any combination of three-dimensional elements (for example, a mesh composed of part hexahedra and part wedges). This paper presents an algorithm for refinement of three-dimensional finite element meshes that is general enough to refine a mesh composed of any combination of the standard three-dimensional element types.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01221213
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    A simple genetic algorithm for the design of reinforced concrete beams (1997)
    Springer
    Engineering with computers 13 (1997), S. 185-196 
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    ISSN: 1435-5663
    Keywords: Artificial intelligence ; Design optimization ; Genetic algorithms ; Structural optimization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract We present an optimization model for the design of rectangular reinforced concrete beams subject to a specified set of constraints. Our model is more realistic than previously published models because it minimizes the cost of the beam on strength design procedures, while also considering the costs of concrete, steel and shuttering. Thus our method leads to very practical designs. As there is an infinite number of possible beam dimensions and reinforcement ratios that yield the same moment of resistance, an efficient search technique is preferred over the more traditional iterative methods. We employ a simple genetic algorithm as the search engine, and we compare our results with those obtained via geometric programming. Since the adjustment of parameters in a genetic algorithm (e.g., population size, crossover and mutation rates, and maximum number of generations) is a significant problem for any application, we present our own methodology to deal with this problem. A prototype of this system is currently being tested in México, in order to evaluate its potential as a reliable design tool for real world applications.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01200046
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    Object-oriented analysis of spatial multibody systems based on graph theory (1997)
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    Engineering with computers 13 (1997), S. 211-221 
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    ISSN: 1435-5663
    Keywords: Graph theory ; Joint coordinate method ; Linked lists of objects ; Object oriented hierarchy ; System matrices
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract The purpose of this paper is to illustrate the implementation of efficient methods in the analysis of general multibody systems. The main goal is a total general purpose program which is able to handle the analysis of open as well as closed loop systems. The development of a general purpose program necessitates considerations concerning storing of code and data access facilities of the analysis code. Many of the building blocks for the analysis are supposed to solve the same problems although this is obtained in different ways depending on the specific type of block. These considerations lead to the creation of an object oriented structure of the analysis code. The development of the analysis algorithms is based on the kinematics of the system. The implementation of these schemes is based on graph theory and is presented through an example by the end of the paper.
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    URL: http://dx.doi.org/10.1007/BF01200048
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    Design of multi-component structural systems for optimal layout topology and joint locations (1997)
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    Engineering with computers 13 (1997), S. 235-243 
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    ISSN: 1435-5663
    Keywords: Structural connections ; Structural optimization ; Topology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Present day topology optimization techniques for continuum structures consider the design of single structural components, while most real life engineering design problems involve multiple components or structures. It is therefore necessary to have a methodology that can address the design of multi-component systems and generate designs for the optimal layouts of individual structures and locations for interconnections. The interconnections include supports provided by the ground, joints and rigid connections like rivets, bolts and welds between components. While topology optimization of structures has been extensively researched, relatively little work has been done on optimizing the locations of the interconnections. In this research, a method to model and define domains for the interconnections has been developed. The optimization process redistributes material in the component design domains and locates the connections optimally based on an energy criterion. Some practical design examples are used to illustrate the capability of this method.
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    URL: http://dx.doi.org/10.1007/BF01200050
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    Self-intersections of offsets of quadratic surfaces: Part II, implicit surfaces (1998)
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    Engineering with computers 14 (1998), S. 14-22 
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    ISSN: 1435-5663
    Keywords: NC machining ; Offset surfaces ; Self-intersections ; Trimmed offset
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract The paper investigates self-intersections of offsets of implicit quadratic surfaces. The quadratic surfaces are the simplest curved objects, referred to as quadrics, and are widely used in mechanical design. In an earlier paper, we have investigated the self-intersections of offsets of explicit quadratic surfaces, such as elliptic paraboloid, hyperbolic paraboloid and parabolic cylinder, since not only are they used in mechanical design, but also any regular surface can be locally approximated by such explicit quadratic surfaces. In this paper, we investigate the rest of the quadrics whose offsets may degenerate, i.e. the implicit quadratic-surfaces (ellipsoid, hyperboloid, elliptic cone, elliptic cylinder and hyperbolic cylinder). We found that self-intersection curves of offsets of all the implicit quadratic surfaces are planar implicit conics and their corresponding curve on the progenitor surface can be expressed as the intersection curve between an ellipsoid, whose semi-axes are proportional to the offset distance, and the implicit quadratic surfaces themselves.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01198971
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    Analysis and verification of the boundary surfaces of solid objects (1998)
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    Engineering with computers 14 (1998), S. 36-47 
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    ISSN: 1435-5663
    Keywords: Discretised surfaces ; Intersections ; Mesh generation ; Solid objects ; Topology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Triangulation of complex three-dimensional objects is a time-consuming process, and the boundary surfaces of the object have to be checked very carefully to ensure no crror is made. With the increased use of computer graphics in the generation of complicated object shapes, such as aircraft, space vessels, machine parts, physical models, etc., visual inspection alone is not good enough to affirm the validity of the object, and a thorough verification of the output from a CAD system is necessary to ensure that the object is well defined and complies with the input requirements of the mesh generator. This paper describes such a data verification procedure for general curved surfaces and objects defined by the boundary surface modelling technique. The quality of individual elements, the overall topological structures, and geometrical correctness in terms of intersections, close touches and sharp angles will all be studied and verified. Several engineering objects are analysed to illustrate the practical applications of the procedure.
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    URL: http://dx.doi.org/10.1007/BF01198973
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    Distributed finite element computations using object-oriented techniques (1998)
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    Engineering with computers 14 (1998), S. 59-72 
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    ISSN: 1435-5663
    Keywords: Distributed computing ; Finite element analysis ; Object-oriented analysis/design ; Parallel processing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract An object-oriented parallel finite element framework has been developed to facilitate rapid prototyping of a wide variety of parallel finite element computations. Parallel computing and object-oriented technologies are integrated to achieve efficiency in both computation and software development. The paper presents various reusable and extensible components that constitute the parallel finite element architecture.
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    URL: http://dx.doi.org/10.1007/BF01198975
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    Seed specification for displaying a streamline in an irregular volume (1998)
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    Engineering with computers 14 (1998), S. 73-80 
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    ISSN: 1435-5663
    Keywords: Critical point ; Data interpolation ; Finite element method ; Irregular volume ; Scientific visualisation ; Spatial point location ; Volume visualisation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Two techniques are presented for specifying seed points, which are the starting points for streamlines, in an irregular volume. One is an interactive seed specification technique, in which efficient data probing is achieved by traversing the adjacency graph of the volume. The other is an automatic seed specification technique. A seed point is placed near a critical point, where the velocity vector is zero. Efficient algorithms are given for finding and classifying the critical point by using a tetrahedral cell. A successful application of these techniques to a problem in a clean room is also described.
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    URL: http://dx.doi.org/10.1007/BF01198976
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    High-level operations dedicated to the integration of mechanical analysis within a design process (1998)
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    Engineering with computers 14 (1998), S. 81-92 
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    ISSN: 1435-5663
    Keywords: Mechanical analysis ; Design process ; Geometric modelling ; Multi-representations ; Integration ; Object-oriented approach
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Here we present the high-level operators of the Mechanical Analysis Module, which is a software architecture dedicated to a better integration of the structural analysis phase within an integrated Computer-Aided Design environment. This generic module is independent of the mechanical analysis method used, and takes place in a distributed software architecture of an integrated design environment. The paper shows that the mechanical operators defined are split among geometric and mechanical treatments in order to enforce this distributed architecture. Thus, the interface between the geometric treatments and the mechanical analysis environment shows the adequacy of the boolean operators when used with mechanical analysis treatments. However, this is demonstrated for a restricted domain of the mechanical analysis, and open ended questions still exist as to when the geometry of the models is diversified. Also, requirements for new geometric treatments and extensions of the current geometric representation are listed.
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    URL: http://dx.doi.org/10.1007/BF01198977
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    Symbolic analysis of linear polyhedra (1990)
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    Engineering with computers 6 (1990), S. 17-29 
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    ISSN: 1435-5663
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract This paper concerns several analytical problems related to linear polyhedra in euclidean three-dimensional-space. Symbolic formulas for line, surface, and volume integration are given, and it is shown that domain integrals are computable in polynomial time. In particular, it is shown that mass, first and second moments, and products of inertia are computable inO(E) time, whereE is the number of edges of the boundary. Simple symbolic expressions for the normal derivatives of domain integrals are also derived. In particular, it is shown that they are closely linked to the topology of the integration domain, as well as that they are expressible as combinations of domain integrals over lower-order domains (faces, edges, and vertices). The symbolic results presented in this paper may lead to an easy incorporation of integral constraints, for example, concerning mass and inertia, in the engineering designing process of solid objects.
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    URL: http://dx.doi.org/10.1007/BF01200201
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    Management of complex structural engineering objects in a relational framework (1990)
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    Engineering with computers 6 (1990), S. 81-92 
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    ISSN: 1435-5663
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract To structure the development of an integrated building design environment, the global representation of the design data may best be organized in terms of hierarchies of objects. In structural engineering design we deal with large sets of independent but interrelated objects. These objects are specified by data. For an engineering design data base the system must be able to model the objects composing the design as well as to manage effectively the design data. The data base management system therefore needs to have some knowledge of the intended use of the data, and must provide an abstraction mechanism to represent and manipulate objects. Much recent research in engineering data bases focuses on object management for specific tasks but gives little attention to the shareability of the underlying information. This paper describes an architecture for the management of complex engineering objects in a sharable, relational framework. Potential application of this approach to object management for structural engineering analysis and design is discussed.
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    URL: http://dx.doi.org/10.1007/BF01200240
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    Toward a unified representation of mechanical assemblies (1990)
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    Engineering with computers 6 (1990), S. 103-112 
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    ISSN: 1435-5663
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Current solid modeling systems are suitable for modeling individual mechanical parts but they do not capture therelationships and/ordependencies among the geometric features of parts in an assembly. Research in the area of “part and assembly modeling” focuses on capturing this missing information. This paper surveys feature-based models for mechanical assemblies and methods for deriving the actual part positions from the part relationships. We have attempted to extract from the literature the essential requirements for a unified feature-based assembly model. Three levels of representation are envisaged—representation of part positions in terms of their spatial coordinates, representation of geometric (feature) relations between individual parts, and representation of the assembly hierarchy. The actual relative positions can be derived from the hierarchical assembly model. Possible areas of application are tolerance analysis and synthesis, automatic generation of assembly sequences, and kinematic analysis and synthesis.
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    URL: http://dx.doi.org/10.1007/BF01200242
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    Representation of assemblies for automatic tolerance chain generation (1990)
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    Engineering with computers 6 (1990), S. 121-126 
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    ISSN: 1435-5663
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract A scheme of representing assemblies and an algorithm for the tolerance chain generation are developed so that tolerance chains of assemblies can be generated automatically to accommodate tolerance analysis at the assembly level. In the hierarchical data structure representing an assembly the connectivity information is carried by the instances of components and subassemblies, and the mating relations between each pair of mating entities are described by mating links, mating paths, mating conditions, and mating features. Mating graphs are derived from the mating links before they are searched for the generation of tolerance chains. The scheme has been implemented in a prototype interactive package that allows the user to model assemblies directly without detailed object modeling. Several examples of various complexity have been tested with success.
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    URL: http://dx.doi.org/10.1007/BF01200244
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    Distributed concurrent engineering computation on a network of microcomputers (1990)
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    Engineering with computers 6 (1990), S. 145-152 
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    ISSN: 1435-5663
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract A programming method that facilitates interworkstation communications on a local area network (LAN) of microcomputers has been developed. Communications are managed using a set of common access status and data files, which are writen to and read from the file server hard disk. Use of this programming method permits the work load associated with large computational problems to be distributed to various workstations connected to a LAN for concurrent processing, and has resulted in substantial solution time savings in problems that have been run. Test problems have been programmed in IBM Compiled BASIC [1] and are continuing with further programs in BASIC and IBM Professional FORTRAN [2]. Applications to actual computational engineering problems are presently being investigated and are briefly discussed. This paper describes the basic principles underlying the distributed processing technique that was developed and presents several example problems that were run to test the technique and develop benchmark results for a particular LAN configuration.
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    URL: http://dx.doi.org/10.1007/BF01200312
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    An intelligent specifications extraction interface for structural design (1990)
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    Engineering with computers 6 (1990), S. 153-165 
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    ISSN: 1435-5663
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Many descriptions of the design process do not include the specifications as part of the process, but rather as an input to the design. Once the specifications are considered to be the input, the assumption is made that they are in a form that is suitable for the design process to proceed. The need for a design always starts with ill-defined objectives. The process by which this information is transformed into well-defined design objectives is called the design specification extraction process. An attempt to expose the underlying structure of the first step in the design process—the design specifications—is presented in this paper. The extraction of specifications is divided into four major tasks—diagnosis or information gathering, interpretation and assessment, classification and decomposition, and information patching. The conceptual framework for the design specification extraction and synthesis is implemented in the expert system program SEISD (specification extraction interface for structural design) developed in the LISP programming language. A few examples are presented to demonstrate the implementation strategies. These examples are drawn from the specific problem of a beam design.
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    URL: http://dx.doi.org/10.1007/BF01200313
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    A formal approach to automating conceptual structural design, part II: Application to floor framing generation (1991)
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    Engineering with computers 7 (1991), S. 91-107 
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    ISSN: 1435-5663
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract The function of the structural system in a building is to transfer gravity as well as lateral loads from their points of origin to the ground. Floor framing generation involves providing a path to transfer the gravity loads to the ground through various structural elements in an architectural plan while meeting the requirements imposed by other entities, such as the architect, the mechanical engineer, and the contractor, involved in the design/construct process. In this paper a formal approach for generating floor framing plans for steel office buildings is presented. We describe the knowledge and the reasoning behind a computer system, FFG (floor framing generator), which generates floor framing schemes for steel office buildings that are rectangular in plan and have a single service core. Constraints arising from structural as well as exogenous considerations are enumerated and their effect on framing schemes is identified. We also elaborate on the evaluation mechanism for ranking alternative schemes, in addition to providing details of the computer implementation.
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    URL: http://dx.doi.org/10.1007/BF01195563
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    Announcement (1991)
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    Engineering with computers 7 (1991), S. 129-129 
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    ISSN: 1435-5663
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01195566
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    Design of an optimal damper to minimize the vibration of machine tool structures subject to random excitation (1991)
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    Engineering with computers 7 (1991), S. 199-208 
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    ISSN: 1435-5663
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract The vibration of machine tools during machining adversely affects machining accuracy and tool life, and therefore must be minimized. The cutting forces for stable turning are generally known to be random, and hence excite all the resonance modes. Of all these modes, those that generate relative motions between a cutting tool and a workpiece are of concern. This paper presents a new approach for designing an optimal damper to minimize the relative vibration between the cutting tool and workpiece during stable machining. An approximate normal mode method is employed to calculate the response of a machine tool system with nonproportional damping subject to random excitation. The major advantage of this method is that it reduces the amount of computation greatly for higher-order systems when responses have to be calculated repeatedly in the process of optimization. An optimal design procedure is presented based on a representative lumped parameter model that can be constructed by using existing experimental or analytical techniques. The two-step optimization procedure based on the modified pattern search and univariate search effectively leads the numerical solution to the global minimun irrespectively of initial values even under the existence of many local minima.
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    URL: http://dx.doi.org/10.1007/BF01206362
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    Toward the integration of knowledge for engineering modeling and computation (1991)
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    Engineering with computers 7 (1991), S. 209-224 
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    ISSN: 1435-5663
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Recent developments in computer science, especially in the area of artificial intelligence (AI), have made possible the representation of knowledge in symbolic terms. This, in turn, has made it possible to represent and integrate a broader range of engineering knowledge so as to provide new kinds of computer support for both analysis and design. This paper presents a typology of engineering knowledge to provide a conceptual basis for its computational integration. A review of the roles of numerical, geometric, and symbolic representations is also given within the context of the knowledge typology. Illustrations are provided from the domain of structural engineering.
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    URL: http://dx.doi.org/10.1007/BF01206363
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    Localization of rational B-spline surfaces (1991)
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    Engineering with computers 7 (1991), S. 237-252 
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    ISSN: 1435-5663
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Localization of curved surfaces is an important problem in the manufacturing and inspection of mechanical elements and in the simulation of manufacturing processes. The objective of this paper is to provide an efficient method for accurate localization of a single free-form surface of the rational B-spline form. Our approach is based on the following components—first, representation of position tolerances in terms of a ball offset tolerance region around the ideal rational spline surface; to facilitate interrogation and data exchange, this is followed by approximation of the bounding surfaces of the tolerance region with rational B-splines; next, optimal positioning of the target surface with respect to the ideal surface by minimizing a distance-based norm; finally, verification of compliance with position tolerance constraints. Examples illustrate our technique.
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    URL: http://dx.doi.org/10.1007/BF01206365
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    Supporting engineering applications by new data base processing concepts—An experience report (1992)
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    Engineering with computers 8 (1992), S. 31-49 
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    ISSN: 1435-5663
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Data base management systems for nonstandard applications (nonstandard data base systems, NDBS), in particular for engineering applications, nowadays constitute one of the most important challenges in the area of data base research. Some major obstacles are concerned with problems of modeling and processing complex engineering objects. Some new system architectures have been proposed, and appropriate concepts for handling the new types of application objects have been developed over the past few years. Based on PRIMA, an NDBS-kernel prototype implementation, we motivate a workstation-oriented architecture for NDBS application systems. We explain a prototypical application system in the environment of VLSI-chip design, which serves as a practical examples in handling complex objects. Analyzing the weaknesses of this initial approach, we derive general concepts for application linkage, discussing, in particular, key issues for an efficient object processing and language binding.
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    URL: http://dx.doi.org/10.1007/BF01206335
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    Feature-based modeling for automatic mesh generation (1992)
    Springer
    Engineering with computers 8 (1992), S. 1-12 
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    ISSN: 1435-5663
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Automatic meshing algorithms for finite element analysis are based on a computer understanding of the geometry of the part to be discretized. Current mesh generators understand the part as either a boundary representation, an octree, or a point set. A higher-level understanding of the part can be achieved by associating engineering significance and engineering data, such as loading and boundary conditions, with generic shapes in the part. This technique, called feature-based modeling, is a popular approach to integrating computer-aided design (CAD) and computer-aided manufacturing through the use of machinable shapes in the CAD model. It would seem that feature-based design also could aid in the finite element mesh generation process by making engineering information explicit in the model. This paper describes an approach to feature-based mesh generation. The feature representation of a fully functioning feature-based system that does automatic process planning and inspection was extended to include finite element mesh generation. This approach is based on a single feature representation that can be used for design, finite element analysis, process planning, and inspection of prismatic parts. The paper describes several advantages that features provide to the meshing process, such as improved point sets and a convenient method of simplifying the geometry of the model. Also discussed are possible extensions to features to enhance the finite element meshing process.
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    URL: http://dx.doi.org/10.1007/BF01206333
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    Approaches to AI methodology in reinforced concrete structures: a case study (1992)
    Springer
    Engineering with computers 8 (1992), S. 93-100 
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    ISSN: 1435-5663
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract A system developed earlier for reinforced concrete halls layout is studied and justified from different aspects. Also, updates of both capabilities and limitations, which were recently incorporated in the system, are emphasized. Some of the original aspects of the system were reviewed and modified, to overcome some of the drawbacks in the earlier presentation. The system's organization remains almost the same. Some suggestions for further improvements to the system are presented as well. Finally the function of the system is illustrated by a sample run of the system.
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    URL: http://dx.doi.org/10.1007/BF01200105
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    Construction of a hybrid sweep-CSG modeler—The sweep-CSG representation (1992)
    Springer
    Engineering with computers 8 (1992), S. 101-119 
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    ISSN: 1435-5663
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Applying sweep operations on 2-D closed contours is a well known method for modelling 3-D solid objects. This paper deals with the implementation of a solid modeler with sweep as the basic representational scheme. In the modeler, a solid is defined by sweeping a planar polygon along a linear or curved trajectory. A sculptured solid may also be defined by using a beta-spline curve for the sweep polygon and a cubic B-spline curve for the sweep trajectory. By incorporating Boolean operations, a hybrid sweep-CSG solid modeler is implemented. The current implementation allows translational, rotational, and twisted sweep operations on a planar polygon composited of lines and arcs. In addition, a solid primitive can also be created by sweeping a planar closed beta-spline curve along a cubic B-spline curve.
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    URL: http://dx.doi.org/10.1007/BF01200106
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    An automatic coarse and fine surface mesh generation scheme based on medial axis transform: Part i algorithms (1992)
    Springer
    Engineering with computers 8 (1992), S. 121-137 
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    ISSN: 1435-5663
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract We present an algorithm for the generation of coarse and fine finite element (FE) meshes on multiply connected surfaces, based on the medial axis transform (MAT). The MAT is employed to automatically decompose a complex shape into topologically simple subdomains, and to extract important shape characteristics and their length scales. Using this technique, we can create a coarse subdivision of a complex surface and select local element size to generate fine triangular meshes within those subregions in an automated manner. Therefore, this approach can lead to integration of fully automatic FE mesh generation functionality into FE preprocessing systems.
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    URL: http://dx.doi.org/10.1007/BF01200364
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    The complementary roles of expert systems and database management systems in a design for manufacture environment (1992)
    Springer
    Engineering with computers 8 (1992), S. 139-149 
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    ISSN: 1435-5663
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Effective product design that satisfies functional requirements and can be manufactured easily requires vast amounts of knowledge on the part of the design engineer. This paper focuses on the complementary roles of expert systems and database management systems as they relate to the Intelligent Design System (IDS) in a Design for Manufacture (DFM) environment. Each technology complements the other in its strengths and abilities. The database management system provides during the design process. The expert system provides a reasoning mechanism for identifying manufacturing violations and generating meaningful recommendations. These components work cooperatively with a CAD interface to form a unified, intelligent design environment. An information flow analysis of the Intelligent Design System resulted in the development of three distinct classifications of information within the database: CAD data, a design catalog, and a knowledge base. The CAD data tables employ an, object oriented approach to store specific information about the physical contains cost, weight, and strength characteristics of the standard parts and fasteners used within the system. The knowledge base contains rules and heuristics concerning design and manufacturing methodologies. The placement of the expert system rules in the database represents an innovation. As a result, the expansion and updating of the materials, fasteners, standard parts, or manufacturing processes used by the Intelligent Design System is facilitated without increased due to the efficient management of the knowledge base by the database management system. This allows the designer to modify the knowledge and help the system to learn without the need for a knowledge engineer.
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    URL: http://dx.doi.org/10.1007/BF01200365
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    An axiomatic theory of engineering design information (1992)
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    Engineering with computers 8 (1992), S. 197-211 
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    ISSN: 1435-5663
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Recent research in design theory has sought to formalize the engineering design process without particular concern for the paradigm used to model design information. The authors propose that no correct formalization of the design process can be achieved without first formalizing the semantics of the information used in the process. To this end, the authors present a new formal theory of design information. The theory, called the hybrid model (HM), is an extended form of axiomatic set theory, and relies on it for consistency and logical rigor. The theory is stated as a collection of axioms, using a standard logic notation. Design entities are modeled by formal units calledobjects. Generalized functions and relations are used to formalize important ordering schemes and abstraction mechanisms relevant to design, including classification by structure and by function, aggregation, specialization, and generalization. The hybrid model is meant not only to aid in the study of the design process itself, but also to improve communications between designers, assist standardization of design specifications, and develop new, powerful software tools to aid the designer in his work.
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    URL: http://dx.doi.org/10.1007/BF01194322
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    A transaction management framework for collaborative engineering (1992)
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    Engineering with computers 8 (1992), S. 213-232 
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    ISSN: 1435-5663
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract This paper discusses the various novel functionalities of a transaction management system for collaborative engineering applications. These features include grouped and shared transactions, dynamic database partitioning, communicative locking, dependency maintenance, update notification schemes, and version management of data configurations. It also establishes protocols for data consistency maintenance on the basis of application semantics and encapsulation of nonserializable data sharing in local databases rather than by the notion of global database consistency. Finally, it presents strategies for implementing these features using a commercial object oriented database management system (OODBMS) environment (ONTOS).
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    URL: http://dx.doi.org/10.1007/BF01194323
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    Engineering materials information systems (1992)
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    Engineering with computers 8 (1992), S. 243-252 
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    ISSN: 1435-5663
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Materials properties information systems are poorly understood. Many databases of materials properties and designations have been produced but, except in the most modest of cases, they have been less successful than their creators had hoped Knowledge based systems (KBS) are subject to exactly the same problems as data based materials information systems and it is important to realize what these are before the special character of KBSs can be used to alleviate them. This paper surveys the unusual and difficult aspects of engineering materials information that must be handled by any organizing methodology, whether manual or computerized, data based or knowledge based, handling information which is stored or inferred.
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    URL: http://dx.doi.org/10.1007/BF01194325
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    A KBES for integrated engineering (1993)
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    Engineering with computers 9 (1993), S. 1-16 
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    ISSN: 1435-5663
    Keywords: Blackboard ; Expert systems ; Industrial structures ; Integrated engineering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract The expert process of engineering involves application of knowledge fundamental to the engineering process at one end, and of compiled knowledge in the form of heuristics gained through many years of experience at the other. Developments in Artificial Intelligence have made the process of computer aided engineering richer by enabling the simulation of this human process of engineering, which until now has been difficult to capture. Knowledge Based Expert Systems (KBES) in engineering developed so far have addressed only narrow domains of the entire process of engineering. This paper discusses a KBES shell (IES) that integrates various AI technologies, which makes it possible to implement new problem-solving strategies required for efficient handling of the entire engineering process. Issues in the integrated process of engineering are discussed first, in order to evolve a specification for the shell. The blackboard architecture is shown to be the ideal backbone for such a shell. The details of inference techniques, the knowledge based backtracking mechanism and the DBMS used in the IES are presented. The application of the IES is demonstrated using the domain of integrated engineering of steel industrial structures as an example. This application encompasses the engineering activities of conceptual design, detailed design, documentation and construction planning.
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    URL: http://dx.doi.org/10.1007/BF01198249
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    A comparative study of etching enamel by acid and laser (1995)
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    Lasers in medical science 10 (1995), S. 37-42 
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    ISSN: 1435-604X
    Keywords: Enamel ; Etch ; Laser ; Acid ; Nd-YAG
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract Acid etching is regarded as one of the main means of providing additional retention in aesthetic dentistry. Alternative methods of achieving bonding to tooth tissue which have been proposed include laser etching. Conflicting results on bond strength to enamel have been reported for laser etching. Here the tensile bond strength of composite resin to acid- and laser-etched enamel was measured and the topographical differences between the surfaces were evaluated using the scanning electron microscope. The laser used was a pulsed Nd-YAG laser at 10 pulses per second with a pulse length of 150μs, 80mJ pulse−1, 1.064μm wavelength. The results obtained indicate that the bond strength of laser-etched enamel was significantly lower than that of acid-etched enamel. In this study the difference may be attributable to the chromophore used. Variations in the rate of traverse of the laser tip across the surface did not appear to produce significant alterations in the bond strength.
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    URL: http://dx.doi.org/10.1007/BF02133162
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    Laserthermia kills acidotic cancer cells more effectively than conventional hyperthermia (1995)
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    Lasers in medical science 10 (1995), S. 31-36 
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    ISSN: 1435-604X
    Keywords: Embryonal carcinoma ; F9 cells ; Laser ; Hyperthermia ; Nigericin ; Acidosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract The aim of this study was to investigate how acidosis affects the sensitivity of F9 embryonal carcinoma cells to conventionally induced hyperthermia and Nd-YAG laser-induced laserthermia. Nigericin, a polyether ionophore, was used to reduce the intracellular pH to 6.8, while the control cells were maintained at a physiological pH of 7.4. Acidosis increased the heat sensitivity significantly. After the water bath only 75% of the acidotic F9S1 cells were viable, whereas all of the control cells at pH 7.4 survived. When the laser was used, the difference was even more pronounced. Only 9% of the acidotic cells were viable after a 2-min treatment and 0.2% after a 4-min treatment. At physiological pH a 2-min treatment left 41% of the cells viable and a 4-min treatment 2%. This study showed that laserthermia is significantly more effective in killing cells with low intracellular pH than it is in killing cells with normal intracellular pH. The core of a tumour is often acidotic and thus radioresistant. It is suggested that laserthermia could be a good choice when treating acidotic radioresistant cancer cells, and its effect as an adjuvant to radiation therapy should be investigated.
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    Diode lasers: Experimental and clinical review (1995)
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    Lasers in medical science 10 (1995), S. 157-163 
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    ISSN: 1435-604X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract Diode lasers are now capable of delivering up to 60 W of power down thin optical fibres, and their medical applications have increased considerably over the past 5 years. Most of the recent experimental and clinical work has been performed using the 805 nm diode laser wavelength, which is more heavily absorbed and is less penetrating than the 1064 nm Nd-YAG wavelength in most tissues. In contact and non-contact mode, the overall tissue effects from the diode laser are similar to the Nd-YAG laser, but with interstitial therapy the 805 nm wavelength produces significantly greater necrosis than the 1064 nm wavelength. Experimental work has established the effectiveness of the diode laser and clinical work has confirmed its suitability for a wide variety of procedures. Diode lasers have the major advantages of being small, compact, portable, efficient, easy to use and virtually maintenance free; they are likely to replace more cumbersome lasers for many medical applications.
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    URL: http://dx.doi.org/10.1007/BF02133326
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    Transmyocardial revascularization (1995)
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    Lasers in medical science 10 (1995), S. 83-91 
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    ISSN: 1435-604X
    Keywords: Transmyocardial revascularization ; Lasers ; Coronary artery disease ; Ischaemia ; Tissue hibernation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract Transmyocardial revascularization (TMR) is a puncture technique proposed as a solution for patients with coronary artery disease who cannot be efficiently treated with the standard revascularization procedures such as bypass surgery or percutaneous transluminal coronary angioplasty (PTCA). The studies presented in this review have investigated the use of lasers to revascularize ischaemic myocardium. Needle puncture methods are also briefly described. The results from experimental studies are not conclusive but the encouraging clinical reports raise further questions about the mechanism of angina relief.
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    URL: http://dx.doi.org/10.1007/BF02150845
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    The effect of the illumination time when treating port-wine stains (1995)
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    Lasers in medical science 10 (1995), S. 93-104 
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    ISSN: 1435-604X
    Keywords: Copper vapour laser ; Electron microscopy ; Illumination time ; Numerical modelling ; Optimal treatment ; Port-wine stain
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract This paper reports the electron microscopy results obtained from two patients who were treated with 5 W of yellow (578 nm) light from a copper vapour laser with an illumination time of 3.6 ms and a 0.3 mm spot diameter. The endpoint of treatment was transient blanching. Following treatment, erythema was observed. There was minimal damage to the epidermis and non-vascular tissue such as the nerve fibres. There was severe damage to the endothelial cells of the ectatic vessels. Twenty-four hours after treatment, platelet activation and collagen were present, indicating that these vessels were no longer viable. Theoretical calculations are used to determine the flow of heat within and away from a 50μm diameter vessel. From this, heating of the entire vessel is shown to occur with illumination times of 4 ms, with minimal heating of the non-vascular tissue. Shorter illuminations do not heat the entire vessel, while the use of longer illumination times will cause excessive damage to the surrounding non-vascular tissue. Illumination times close to 4 ms must be regarded as optimal.
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    URL: http://dx.doi.org/10.1007/BF02150846
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    Photodynamic therapy to the oral cavity, tongue and larynx: a canine normal tissue tolerance study (1995)
    Springer
    Lasers in medical science 10 (1995), S. 13-18 
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    ISSN: 1435-604X
    Keywords: Photodynamic therapy ; Larynx ; Oval cavity ; Light dose rates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract Photodynamic therapy (PDT) has the potential to treat early carcinomas of the oral cavity and larynx while preserving normal tissue. However, normal tissues retain the photosensitizing agents and may be activated by high light fluence and dose rates resulting in normal tissue necrosis. The effects of varying dose rates of light delivery on various tissues in the upper aerodigestive tract have not been evaluated to date and are necessary to determine a ‘therapeutic light dose range’ that will result in selective tumour necrosis. Thirty adult mongrel dogs received intravenous Photofrin, 2 mg kg−1, 48 h prior to PDT treatment. Photodynamic therapy was administered to the tongue, buccal mucosa and larynx with a microlens fibre and implantable cylindrical diffuser at various dose rates from 20 to 125 J cm−2 at 150 mW cm−2. At the same dose rate of light delivery, the tongue was the most sensitive organ, followed by the buccal mucosa, and last by the larynx. The differential tissue effect of identical dose rates of therapy must be taken into account when administering PDT so that selective tumour necrosis with normal tissue preservation may be achieved. This study indicates the need to perform evaluations of the effect of PDT on other tissue types in an animal model with each new photosensitizer prior to administering PDT to those areas in humans.
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    The relevance of pulse repetition rate and radiant exposure to the neurophysiological effects of low-intensity laser (820 nm/pulsed wave) irradiation upon skin temperature and antidromic conduction latencies in the human median nerve (1995)
    Springer
    Lasers in medical science 10 (1995), S. 253-259 
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    ISSN: 1435-604X
    Keywords: Nerve conduction ; Laser therapy ; Skin temperature ; Biostimulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract The effects of low-intensity near-infra-red laser irradiation (820 nm; 1.5 and 9.0 J cm−2; pulsed at 12 Hz, 73 Hz and 5 kHz) upon peripheral neurophysiology and skin temperature were investigated using antidromic conduction studies in the human median nerve in vivo. Healthy human volunteers (n = 90) were recruited and allocated randomly to either a control group (n=10) or one of eight experimental groups (two radiant exposures, 1.5 J cm−2 and 9.0 J cm−2 at one of three pulse repetition rates, 12 Hz, 73 Hz or 5 kHz, in addition to a placebo group for each radiant exposure;n = 10 all groups). Analysis of variance (ANOVA) demonstrated a significant (p≤0.05) decrease in skin temperature following irradiation at the lowest radiant exposure (1.5 J cm−2) combined with pulse repetition rates of 73 Hz and 5 kHz, with the greatest effect at 73 Hz. These changes in skin temperature were coupled with increases in negative peak latency (NPL); ie changes in NPL were inversely related to changes in skin temperature. However, in contrast to the authors' previous findings using continuous wave (CW) laser irradiation, differences in NPL were not found to be significant. These findings, therefore, provide little evidence of the neuro-physiological effects of low-intensity infra-red irradiation at the dosage levels and pulse repetition rates used here.
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    Vascular and other non-tumour applications of photodynamic therapy (1996)
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    Lasers in medical science 11 (1996), S. 3-10 
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    ISSN: 1435-604X
    Keywords: Photodynamic therapy ; Non-tumour ; Arteries ; Fibrocellular intimal hyperplasia ; Aminolaevulinic acid ; Phthalocyanine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract Photodynamic therapy is being investigated as a cancer therapy. As a cytotoxic treatment, it may also have therapeutic benefits in certain non-tumour conditions. The mechanism of photodynamic therapy is discussed in relation to its cancer therapy. The literature on non-tumour applications of photodynamic therapy is subsequently reviewed, highlighting its vascular applications in particular. Arterial angioplasty restenosis has proved resistant to all treatments tried thus far. Because fibrocellular intimal hyperplasia arising from the proliferation of vascular medial smooth muscle cells forms the pathological basis of restenosis, photodynamic therapy has been considered in its prevention. The literature on two second-generation photosensitizers (5-aminolaevulinic acid and phthalocyanine) which are likely to achieve clinical application are reviewed with regard to their photodynamic effects on fibrocellular intimal hyperplasia. This review concludes that photodynamic therapy shows enough promise for the inhibition of fibrocellular intimal hyperplasia for large animal studies to be pursued.
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    Meeting reports (1996)
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    Lasers in medical science 11 (1996), S. 59-60 
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    ISSN: 1435-604X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
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    URL: http://dx.doi.org/10.1007/BF02161294
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    Uvulopalatopharyngoplasty with CO2, contact ND-YAG or combined CO2 and ND-YAG laser beams (1996)
    Springer
    Lasers in medical science 11 (1996), S. 53-58 
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    ISSN: 1435-604X
    Keywords: CO2 laser ; Contact Nd-YAG laser ; Combined CO2 and Nd-YAG laser ; Uvulopalatopharyngoplasty ; Sleep apnoea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract Three different surgical lasers, ie CO2, contact Nd-YAG and Combolaser (combined simultaneous and co-axial CO2+Nd-YAG laser beam), were used for 76 uvulopalatopharyngoplasty (UPPP) operations. The effects of different lasers on intra-operative bleeding, operation time and post-operative pain were compared. Sixty patients with obstructive sleep apnoea syndrome (OSAS) and 16 patients with socially disturbing snoring were operated on. The CO2 laser was used in 24 patients, contact Nd-YAG was used in 27 patients and Combolaser was used in 25 patients. The Combolaser was associated with significantly less intra-operative bleeding and a shorter operation time. During the immediate recovery period, post-operative pain was most mild after operations with the CO2 laser when graded according to need for analgesics, or by the patients' subjective evaluation. Concerning possible post-operative complaints or overall outcome of the UPPP operation, no differences were found between the lasers.
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    A study of the radiological use of laser angioplasty in Britain (1996)
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    Lasers in medical science 11 (1996), S. 79-95 
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    ISSN: 1435-604X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract Laser recanalization was introduced and developed in Britain in the 1980s in an attempt to deal with the limitations associated with the conventional technique of percutaneous transluminal angioplasty (PTA). Since then, the use of this technique has decreased. This paper reports the findings of a comprehensive literature survey and interviews with a representative sample of British interventional radiologists on the reasons for this decline, and suggests the likely future direction for this technology. It has been determined that the main reasons for the decline are improvements in conventional guidewire and catheter technology, the high cost of the laser system, and the lack of evidence of any improvement in results compared with conventional PTA. However, despite current disenchantment, the majority of radiologists questioned felt that lasers could have a future role to play and that development of these systems should continue.
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    URL: http://dx.doi.org/10.1007/BF02133205
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    Laser Doppler velocimetry in retinal arteries of infants (1995)
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    Lasers in medical science 10 (1995), S. 267-272 
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    ISSN: 1435-604X
    Keywords: Blood flow pulsatility ; Human infants ; Laser Doppler velocimetry ; Retinal blood flow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract The present study was conducted to assess the feasibility of laser Doppler velocimetry in young infants, as a prelude to ultimately undertaking such measurements in premature infants. A portable, unidirectional laser Doppler velocimeter was developed based on a Kowa RC-2 hand-held fundus camera. Six infants between 1 and 21 weeks of age were studied. Relative red blood cell velocity (δfmax) at the centre of retinal arteries was measured over approximately 10 heart cycles. A pulsatility parameter (P=1−δfmax.dia/δfmax.sys), a summary index of vascular status, was determined from the average diastolic and systolic values of δfmax. Velocity waveforms were obtained in four of the six infants. Arterial pulsatility for the group was 0.63±0.13. Precise non-invasive measurement of arterial red blood cell velocity waveforms in young infants was achieved. The high signal-to-noise ratio and temporal resolution of this data suggest that relative measurements of retinal blood flow may permit assessment of haemodynamic changes in premature infants.
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    Sensitization and photodynamic therapy of normal pancreas, duodenum and bile ducts in the hamster using 5-aminolaevulinic acid (1996)
    Springer
    Lasers in medical science 11 (1996), S. 11-21 
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    ISSN: 1435-604X
    Keywords: Photodynamic therapy ; 5-Aminolaevulinic acid ; Pancreas ; Bile duct ; Duodenum ; Fluorescence microscopy ; Light dosimetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract Photodynamic therapy (PDT) using 5-aminolaevulinic-acid-(ALA)-induced protoporphyrin IX (PPIX) increases survival in hamsters with pancreatic cancer. However, experiments with other photosensitizers on this model show a high risk of duodenal perforation. In this paper, the pharmacokinetics and PDT effects of ALA on normal tissues in the pancreatobiliary region are presented. Using quantitative fluorescence microscopy, maximum PPIX fluorescence was seen in the bile ducts, less in the duodenal mucosa and least in the muscularis propria and pancreas. For PDT, light was delivered either using a bare fibre touching the tissue (single-point illumination), or irradiating a 1.5 cm diameter circular area. Single-point PDT (50 J) produced only localized reversible damage without perforation. Surface irradiation of the whole periampullary region (50 J cm−2) caused extensive damage, sometimes with perforation. Before PDT can be used safely to treat tumours of the pancreas and bile duct, further studies are necessary to understand its effect on larger areas of normal tissue.
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    URL: http://dx.doi.org/10.1007/BF02161288
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    Editorial (1996)
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    Lasers in medical science 11 (1996), S. 217-217 
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    ISSN: 1435-604X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02134910
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    Tetra(m-hydroxyphenyl)chlorin clinical photodynamic therapy of early bronchial and oesophageal cancers (1996)
    Springer
    Lasers in medical science 11 (1996), S. 227-235 
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    ISSN: 1435-604X
    Keywords: Photodynamic therapy ; PDT ; mTHPC ; Early cancer ; Squamous cell carcinoma ; Oesophagus ; Bronchi ; Photosensitizer ; Light dosimetry ; Clinical
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract There have been few studies to date of clinical photodynamic therapy (PDT) with tetra(m-hydroxyphenyl)chlorin (mTHPC). This paper describes the results of the authors' experience with this second-generation photosensitizer, used in the treatment of 40 early cancers of the oesophagus and the bronchi. Surface illumination of the tumour was performed, in most cases, 4 days after intravenous injection of 0.15 mg kg−1 of mTHPC, using 652 nm or 514 nm continuous wave laser light. Endoscopic follow-up with biopsies and brushings was possible for 35 tumours: 27 (77%) showed no recurrence after disease-free follow-ups that ranged from 3 to 38 months. Major complications, all of which were after red light illumination, included one bronchial stenosis, one oesophagotracheal fistula and two probable occult perforations of the oesophagus. Photodynamic therapy with green light renders such perforations of the oesophageal wall essentially impossible at the applied conditions, and appears not to reduce the efficacy of the treatment. Skin photosensitization, which was never observed later than the first week after injection, occurred in 12 patients. Hence, PDT with mTHPC is a safe and effective treatment for early carcinomas of the oesophagus and the tracheobronchial tree.
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    URL: http://dx.doi.org/10.1007/BF02134913
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    Photodynamic therapy of 168 early stage cancers of the lung and oesophagus: a japanese multi-centre study (1996)
    Springer
    Lasers in medical science 11 (1996), S. 255-259 
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    ISSN: 1435-604X
    Keywords: Photodynamic therapy ; Early stage lung cancer ; Superficial oesophageal cancer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract In 1994, the Ministry of Health and Welfare of Japan approved photodynamic therapy (PDT) for the treatment of early stage lung cancer (T0 and T1), superficial oesophageal cancer, superficial early stage gastric cancer and carcinoma in situ and/or dysplasia of the cervix. The decision to do so was based on studies carried out by the PDT Research Group of the Ministry, including PDT treatment of 168 early stage central lung cancers (123 superficial lesions and 45 nodular lesions) and 32 superficial oesophageal cancers. The results presented in this article were analysed according to the extent of the lesion. Of the 123 superficial lung cancers, complete remission (CR) was obtained in 93% of 89 lesions less than 1.0 cm in diameter. Larger lesions responded less well. Complete remission was obtained in 97% of the 33 superficial oesophageal cancers, although three of six patients with lesions over 3.0 cm in diameter later died of metastatic disease. The authors believe PDT to be a suitable and effective treatment for early stage lung and oesophageal cancers.
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    Human tissue levels and plasma pharmacokinetics of temoporfin (Foscan®, mTHPC) (1996)
    Springer
    Lasers in medical science 11 (1996), S. 267-272 
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    ISSN: 1435-604X
    Keywords: Photosensitizer ; Photodynamic therapy ; mTHPC ; Temoporfin ; Pharmacokinetics ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract A Phase I photodynamic therapy (PDT) clinical trial was carried out with Temoporfin (Foscan®, mTHPC) at the Departments of Otolaryngology at Orebro Medical Center (OMC) and Long Island Jewish Medical Center (LIJMC). A range of drug doses, consisting of 0.3, 0.15, 0.075 and 0.0375 mg kg−1, were utilized. Light treatment was performed on the sixth day after injection of the photosensitizer mTHPC. Photodynamic therapy was done on prostate cancer (six cases), bronchial cancer (one case), nasopharyngeal cancer (three cases), laryngeal cancer (eight cases), mesothelioma (one case), laryngeal papilloma (five cases) and basal cell nevus syndrome (one case). A number of patients were treated more than once. Plasma was collected and analysed at 1, 24, 48, 72, 96, 120 and 144 h and at 2 weeks post-injection, to follow the loading and clearance rate of the photosensitizer. Normal and malignant tissues were collected immediately prior to PDT, chemically extracted, and analysed for drug content spectrofluorometrically. Plasma drug levels were proportional to the dose. The half-life of the drug was 45.4 h across the entire dose range. The ratio of the drug in the tumour compared to normal adjacent mucosa was in the range of 2–3. There were no significant adverse effects. These data establish the basis for full clinical trials.
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    Quantification of polydimethylsiloxane concentration in turbid samples using raman spectroscopy and the method of partial least squares (1998)
    Springer
    Lasers in medical science 13 (1998), S. 32-41 
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    ISSN: 1435-604X
    Keywords: Biomedical diagnostics ; Breast implant leakage ; Optical spectroscopy ; Partial least squares ; Polydimethylsiloxane (PDMS) ; Raman spectroscopy ; Silicone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract This paper presents a preliminary application of Raman spectroscopy in conjunction with the chemometric method of partial least squares to predict silicone concentrations in homogenous turbid samples. The chemometric technique is applied to Raman spectra to develop an empirical, linear model relating sample spectra to polydimethylsiloxane (silicone) concentration. This is done using a training set of samples having optical properties and known concentrations representative of those unknown samples to be predicted. Partial least squares, performed via cross-validation, was able to predict silicone concentrations in good agreement with true values. The detection limit obtained for this preliminary investigation is similar to that reported in the magnetic resonance spectroscopy literature. The data acquisition time for this Raman-based method is 200 s which compares favourably with the 17 h acquisition required for magnetic resonance spectroscopy to obtain a similar sensitivity. The combination of Raman spectroscopy and chemometrics shows promise as a tool for quantification of silicone concentrations from turbid samples.
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    Measurement of radiometric surface temperature and integrated backscattered light intensity during feedback-controlled laser-assisted cartilage reshaping (1998)
    Springer
    Lasers in medical science 13 (1998), S. 66-72 
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    ISSN: 1435-604X
    Keywords: Cartilage ; Laser-induced reshaping ; Nd:YAG laser ; Plastic surgery ; Reconstructive surgery ; Stress relaxation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract Cartilage undergoes characteristic mechanical stress relaxation following laser irradiation below the ablation threshold. Porcine auricular cartilage (1–2 mm thickness) was irradiated with a Nd:YAG laser (λ=1.32 μm) at two power levels (W/cm2). Surface temperature (S c (t) (°C)) (monitored using a single element HgCdTe infrared detector, 10-14 μm spectral range), and integrated back scattered light intensityI(t) were measured during laser irradiation. A HeNe laser beam (λ=632.8 nm) was incident on the back surface of the cartilage specimen and fractional integrated backscattered light intensity was measured using an integrating sphere anda silicon photodiode. Laser irradiation (5.83 W/cm2, 50 Hz pulse repetition rate (PRR)) continued until surface temperature reached approximately 70°C, during which cartilage mechanical stress relaxation was observed. Integrated back scattered light intensity reached a plateau at about 70°C). At higher laser power (39.45 W/cm2, 50 Hz PRR), a feedback-controlled cryogen spray was used to maintain surface temperature below 50°C. A similar plateau response was noted in integrated backscattered light intensity. This signal may be used to optimise the process of stress relaxation in laser cartilage reshaping. Several clinical applications involving reconstructive surgery are proposed.
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    Laser therapy of varicosities with the flashlamp-pumped pulsed dye laser (1996)
    Springer
    Lasers in medical science 11 (1996), S. 193-197 
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    ISSN: 1435-604X
    Keywords: Varicosities ; Pulsed dye laser
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract The flashlamp-pumped pulsed dye laser with an output wavelength of 585 nm and a pulse duration of 450μm was used to treat 102 areas of blue and red varicosities in the lower limbs of female patients. Varicosities could be divided into two groups, early red varicosities and more developed blue varicosities. Forty-two areas of blue varicosities were treated with a single pulse, and only 20% of these were eliminated. Blue varicosities were then treated in three treatment sessions, 3 weeks apart, and none of them could be occluded. Red varicosities responded better; all of the varicosities treated were occluded in three treatment sessions separated by 3 weeks. The use of two consecutive pulses with only 6.5 Jcm−2 in a single treatment session resulted in only 54% of the varicosities being eliminated. Finally, seven areas of red varicosities were treated in a single treatment with an argon laser at 2 W; only 10–20% of these lesions responded. The pulsed dye laser is therefore of most use in treating red varicosities.
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    Guest editorial (1996)
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    Lasers in medical science 11 (1996), S. 219-219 
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    ISSN: 1435-604X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
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    URL: http://dx.doi.org/10.1007/BF02134911
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    Time-resolved confocal fluorescence microscopy of porphyrins for phototherapy (1996)
    Springer
    Lasers in medical science 11 (1996), S. 237-246 
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    ISSN: 1435-604X
    Keywords: Fluorescence ; Time-resolved confocal microscopy ; Porphyrins ; Fluorescence polarization ; Photodynamic therapy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract The application of a novel time-resolved confocal fluorescence microspectrometer to studies of the distribution and speciation of porphyrin photosensitizers in rat C6 cerebral glioma cells is described. The instrument combines a mode-locked argon ion laser excitation source with time-correlated single photon counting fluorescence detection and has sub-micron spatial and sub-nanosecond temporal resolution. The porphyrins studied were haematoporphyrin derivative (HpD), haematoporphyrin IX (HP), porphyrinc (Pc) and the tetrakiscarborane carboxylate ester of 2,4-(α,β-dihydroxyethyl) deuteroporphyrin IX (BOPP). From the heterogeneous emission observed in vitro, assignments and spatial location of various porphyrin species are proposed.
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    New laser literature (1996)
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    Lasers in medical science 11 (1996), S. 273-275 
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    ISSN: 1435-604X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02134919
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    Optical spectroscopy for the early diagnosis of gastrointestinal malignancy (1998)
    Springer
    Lasers in medical science 13 (1998), S. 3-13 
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    ISSN: 1435-604X
    Keywords: Biopsy ; Fluorescence ; Optical ; Raman ; Spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract The early diagnosis of gastrointestinal malignancy will allow eradication of the disease prior to invasive cancer. At present, fluorescence spectroscopy offers the most realistic prospect of an early clinical system and is currently under evaluation. Optical coherence tomography can differentiate the layers of the oesophageal wall and has greater reolution than ultrasound. Although complicated, Raman spectroscopy offers the greatest information with possible development of a molecular endoscope.
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    Design and Characterisation of a Tissue Phantom System for Optical Diagnostics (1998)
    Springer
    Lasers in medical science 13 (1998), S. 160-171 
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    ISSN: 1435-604X
    Keywords: Keywords: Absorption; Fluorescence; Integrating sphere; Optical tissue phantom; Scattering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: We present an optical phantom system especially suited to investigating the generation and transport of laser-induced fluorescence in biological tissues. The phantom system consists of micrometre-sized particles of aluminium oxide, iron and coloured resin dispersed in a solid, transparent host (polyorganosiloxane), from which mechanically stable samples can be made. Mie theory is applied to predict the radiation transport parameters from the optical properties of the isolated components. The predictions are in good agreement with the results of integrating sphere measurements. The radiation transport parameters of the samples are reproducible and temporally stable.
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    Photosensitisation of red blood cell haemolysis by photodynamic agents (1998)
    Springer
    Lasers in medical science 13 (1998), S. 42-54 
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    ISSN: 1435-604X
    Keywords: Erythrocyte membranes ; Hemolysis ; Photosensitising agent
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract Photosensitised haemolysis of red blood cells (RBC) by sodium hypericin, haematoporphyrin, protoporphyrin, Photofrin® and benzoporphyrin derivative monoacid ring A were investigated for broad spectrum near-ultraviolet (UVA)-visible light and monochromatic 630 nm irradiations. The delayed photohaemolysis rate (1/t 50) increased with the approximate square of the incident light dose, wheret 50 is the dark incubation time required for 50% haemolysis. The power dependence of 1/t 50 on the sensitiser concentration varied with the specific sensitiser and the irradiation conditions. Energy calculations for protoporphyrin show that the quantum efficiency of delayed photohaemolysis at 630 run is independent of the sensitiser concentration at constantt 50 and increases witht 50 The protective effects of water-soluble singlet oxygen quenchers are indicative of a Type II photosensitisation pathway for these agents. Pretreatment of RBC with hydrogen peroxide suppressed photosensitisation by protoporphyrin accompanied by lipid peroxidation and oxidation of haemoglobin. The photohaemolysis curves are analysed with a target theory model which postulates that haemolysis requires thermal activation of photochemical damage. The model calculations indicate that photosensitised haemolysis requires two photochemical hits and a highly cooperative thermal process.
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    132-hydroxy-bacteriopheophorbidea-methylester pharmacokinetics in mice bearing Lewis lung carcinoma (1998)
    Springer
    Lasers in medical science 13 (1998), S. 78-81 
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    ISSN: 1435-604X
    Keywords: Lewis lung carcinoma ; Pharmacokinetics ; Spectroscopy ; 132-hydroxy bacteriopheophorbidea-methylester (132-OH-BPME)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract The photosensitiser 132-hydroxy bacteriopheophorbide a-methylester (132-OH-BPME) is characterised by a high absorption coefficient at the far red wavelength 750 nm and a good singlet oxygen quantum yield. The pharmacokinetics of 132-OH-BPME was studied on the Lewis lung carcinoma in mice after i.v. administration of 5 mg/kg body weight at different incubation intervals. The accumulation dye was chemically extracted from selected tissues and the concentrations were measured by absorption spectroscopy. The parenchymatous organs, liver, spleen and kidney, showed maximum 132-OH-BPME concentrations after 2 h incubation (liver, spleen) and 4 h postinjection (kidney). A high uptake was detected in the lung with the maximum concentration at 2 h. The malignant tissue accumulated high 132-OH-BPME concentrations at 2–12 h postinjection with peaking at 8 h. The 132-OH-BPME concentrations in muscle tissue, representing the normal tumour surroundings, and in the skin were very low. The results of our study suggest that photodynamic therapy (PDT) using 132-OH-BPME could be effective at an incubation time of about 8 h postsensitiser injection, when the tumour 132-OH-BPME concentration has reached its maximum and the muscle and skin concentrations are at a minimum.
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    Temperature Feedback and Collagen Cross-Linking in Argon Laser Vascular Welding (1998)
    Springer
    Lasers in medical science 13 (1998), S. 98-105 
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    ISSN: 1435-604X
    Keywords: Keywords: Collagen; Infrared thermometry; Radiometry; Temperature; Tissue fusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract. A preliminary single-animal study of in vivo argon laser vascular welding was conducted using a canine model. The effects of temperature feedback control and saline drip cooling on patency and collagen cross-linking were investigated. The surface temperature at the centre of the laser spot was monitored using a two-colour infrared thermometer. The surface temperature was limited by either a saline drip or feedback control of the laser. Acute patency was evaluated and collagen cross-link assays were performed. Though both protocols yielded successful tissue fusion, welds maintained at a surface temperature of 50°C using feedback control had an elevated cross-link count compared to controls, whereas tissues irradiated without feedback control experienced a cross-link decrease. Simulations using the LATIS (LAser-TISsue) computer code suggest that drip-cooled procedures achieve significantly higher temperatures beneath the tissue surface than temperature feedback-controlled procedures. Differences between the volumetric heating associated with drip-cooled and feedback-controlled protocols may account for the different effects on collagen cross-links. Covalent mechanisms may play a role in argon laser vascular fusion.
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    Photodynamic Therapy (PDT) of Gastrointestinal Tumours: A New Light Delivery System (1998)
    Springer
    Lasers in medical science 13 (1998), S. 137-142 
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    ISSN: 1435-604X
    Keywords: Keywords: Colorectum; Intraluminal probe; Non-laser light source; Oesophagus; Paterson lamp; Photodynamic therapy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract. The Paterson lamp is a convenient, low cost, portable, alternative light source to lasers for photodynamic therapy (PDT). A multiwavelength capability enables the clinician to vary the photosensitiser used. The Paterson lamp has been applied in the field of dermatology using a liquid light guide with distal optics for surface application. We now describe distal optics suitable for use with this light guide for intraluminal applications in the oesophagus and colorectum. The geometry of the site (oesophagus and colorectum) requires distal optics such as a cylindrical diffuser or a side-fire diffuser. We have designed new probes that diffuse light radially from the guide axis (cylindrical diffusion). The tips have a frosted glass surface that scatters and effectively couples light radially into the tissue. An acrylic spacer is placed over the diffuser to position the tissue at a constant diameter from the probe. This is held in position by a silicone sheath placed over the distal one metre. For use in the oesophagus, a channel, to facilitate intubation over a guide wire, is included. The diameter of the entire probe is 8.4 mm and the power output can be adjusted from 0–500 mW. Pilot PDT of tubulovillous adenomas of the rectum and Barrett's oesophagus using this light delivery system is currently underway and has shown good early response in the treated area.
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    Real-Time Monitoring of Blood–Brain Barrier Disruption Induced by Ultraviolet Laser Irradiation (1998)
    Springer
    Lasers in medical science 13 (1998), S. 172-180 
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    ISSN: 1435-604X
    Keywords: Keywords: Argon laser; Blood–brain barrier; Brain; Evans blue; Guinea-pig; Vasodilation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Ultraviolet laser light of sufficient power can induce focal œdema in the brain. The formation of ultraviolet-induced vasogenic \kdema was monitored by observing real-time changes in the integrity of the blood–brain barrier. The brain surface of guinea-pigs injected with Evans blue was exposed to light from a continuous wave argon laser at 351 nm, delivered via an optical fibre. The integrity of the blood–brain barrier was evaluated by measuring surface reflectance using a separate probing light. The brain was then sectioned and examined using light and electron microscopy. Extravasation of Evans blue following vasodilatation was observed when the irradiation intensity was greater than 0.64 W/cm2. The extent of glial and vascular damage could be correlated with the laser power. Irradiated vascular endothelium exhibited lipping at the tight junction, vacuolation and mitichondrial swelling. These results suggest that disruption of the blood–brain barrier induced by ultraviolet light is preceded by vasodilatation.
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    Carbon Dioxide Laser Resurfacing of Rhytides and Photodamaged Skin (1998)
    Springer
    Lasers in medical science 13 (1998), S. 232-241 
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    ISSN: 1435-604X
    Keywords: Keywords: CO2 laser, Laser treatment; Rhytides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract. Carbon dioxide (CO2) laser resurfacing has been used as a method to treat rhytides and photodamaged skin. This laser offers several advantages over previously utilised modalities but its use has several inherent risks. This article will review important aspects of CO2 laser resurfacing including laser-skin interactions, patient selection, effective pre- and post-operative regimens and potential complications.
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    Helium-Neon (He-Ne) Laser Irradiation Increases the Incidence of Unreduced Bovine Oocytes During the First Meiotic Division In Vitro (1998)
    Springer
    Lasers in medical science 13 (1998), S. 260-264 
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    ISSN: 1435-604X
    Keywords: Keywords: Bovine; Cell proliferation; He-Ne laser; Oocyte; Photobiology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract. Low power He-Ne laser irradiation was applied to immature bovine oocytes to investigate the incidence of unreduced oocytes (diploid oocytes) during the first meiotic division in vitro. Immature bovine oocytes from cows killed at a slaughterhouse were irradiated with He-Ne laser irradiation at 0.05 and 0.25 J/cm2 exposures. An oocyte group was left untreated serving as the control group. All oocytes were matured in TCM-199 medium supplemented with 10% fetal calf serum (FCS). Unreduced oocyte percentages obtained in the irradiated oocytes group were significantly higher (p〈0.01 and p〈0.001, respectively) than those of the control group. Furthermore, the laser-treated oocytes showed a degeneration rate significantly higher (p〈0.01 and p〈0.001, respectively) than those observed in the control group. It is concluded that the application of He-Ne laser irradiation at 0.05 and 0.25 J/cm2 exposures increased the incidence of unreduced oocytes and the percentage of degenerated oocytes during the in vitro meiosis process of immature bovine oocytes.
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    Review and Classification of Corneal Topographers (1999)
    Springer
    Lasers in medical science 14 (1999), S. 2-19 
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    ISSN: 1435-604X
    Keywords: Keywords: Corneal topography; Fluorescence; Holography; Interferometry; Moiré; Partial coherence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract. Corneal topography has, due to developments in refractive surgery and contact lens fitting, become a widely used diagnostic tool. Many types of topographers have been introduced, but there is some confusion on classification and subsequent principal possibilities of the various devices offered to the practitioner. The purpose of the study reported here was to make an inventory of developed devices, analyse the basic principles and create a classification based on optical principles. A literature search was done using Medline, the IBM Patent Server, and references found in articles and patents. This search resulted in a variety of descriptions that could be classified into 12 groups according to their use of light source and light-matter interaction of which four groups have representatives on the commercial market. This classification can be used by researchers and practitioners to gain insight into the possibilities of a given device in relation to the desired application.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s101030050015
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  • 89
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    Diffusing Fibre Tip for the Minimally Invasive Treatment of Liver Tumours by Interstitial Laser Coagulation (ILC): An Experimental Ex Vivo Study (1999)
    Springer
    Lasers in medical science 14 (1999), S. 32-39 
    Details
    ISSN: 1435-604X
    Keywords: Keywords: Interstitial laser coagulation; Laser applicator; Laser induced thermotherapy; Liver tumours; Nd-YAG laser
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract. A newly developed diffusing laser applicator was examined for interstitial laser coagulation (ILC) of liver tumours. The applicator consisted of a matted quartz core and a quartz glass dome, also matted on its inner surface and sealed to the fibre. The applicator provided a homogeneous light intensity distribution over an active length of about 20 mm. Lesions were created in an ex-vivo porcine liver model using a Nd-YAG laser comparing the new diffusing tip with a Ringmode®-ITT applicator in order to find optimal laser parameters and damage thresholds. The lesions were investigated using macroscopic size measurement, volume calculation and histological examination (H&E, NADPH-dehydrogenase). The damage threshold of the diffusing tip was 6 W at 14 min exposure time whereas the Ringmode®-ITT applicator had its limit at 5 W and 12 min exposure. Comparing various exposure times showed that treatment over a time of more than 840 s did not significantly increase the lesion volume. At 5 W and 720 s the mean lesion volume was 6.9±1.1 cm3 with the diffusing tip and 6.3±0.6 cm3 with the Ringmode®-ITT applicator, both having a slight ellipsoidal shape. Hence, the created lesions were not significantly different for both applicators when the same laser parameters were applied. On the other hand, the new diffusing tip had a higher damage threshold and was therefore capable of producing maximal coagulation volumes of up to 7.9±0.5 cm3 at 5 W and 20 min. The experiments showed that lesions with a dimension of 31×22 mm can be achieved with the diffusing applicator which seem suitably sized for treating small human liver metastases in a single laser session.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s101030050018
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  • 90
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    Laser Myringotomy (L-Myringotomy) and Ventilating Tubes: A Preliminary Comparative Study (1999)
    Springer
    Lasers in medical science 14 (1999), S. 62-66 
    Details
    ISSN: 1435-604X
    Keywords: Keywords: Laser myringotomy; Otitis media with effusion; Tympanic membrane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract. A prospective comparative study was done to assess the validity of laser myringotomy (L-myringotomy) when compared to the insertion of ventilating tubes (VT). In 23 children with chronic otitis media with effusion, a VT was inserted in the left ear while a laser myringotomy was performed in the right ear by using the CO2 Sharplan 1030 laser. After a six month follow-up conducted during the winter months, the results with the laser myringotomy were equal to those in the left ear with the VT. During the follow-up period, three ears required additional laser myringotomy either for early closure or because of otitis media and the accumulation of effusion in the middle ear cavity. Nevertheless, the use of laser has the advantage that there is no foreign body in the ear, the tympanic membrane is closed after four to seven weeks, and since the procedure is very short, the time for anaesthesia is minimal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s101030050022
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  • 91
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    Photodynamic Therapy of Malignant Ovarian Tumours Cultivated on CAM (1999)
    Springer
    Lasers in medical science 14 (1999), S. 91-96 
    Details
    ISSN: 1435-604X
    Keywords: Keywords: Chorioallantoic membrane (CAM); Liposomes; Methylene blue; Ovarian cancer; Photodynamic therapy; Photosensitiser
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract. The disappointing results with either surgery alone and/or chemotherapy in the treatment of malignant ovarian tumours have led to an increased interest in additional treatment schedules. Photodynamic therapy (PDT), a modality involving the use of a photosensitising drug and activating light, is being used increasingly as a local treatment for neoplastic lesions. The synthesis and evaluation of new photosensitisers for the treatment of gynaecological lesions and malignancies continues to be an active area of investigation for proper application of the photodynamic process in the gynaecological field. The effect of PDT using methylene blue (free and combined with liposomes) as a photosensitiser for treating human ovarian malignant tumours cultivated on the chorioallantoic membrane was evaluated. Two days after PDT, the treated implanted tumours were markedly decreased in size. Areas of necrosis with black coloration, dryness and eschar formation were observed. Five days after PDT, tumour remission was clearly observed in all the treated tumours. Photodynamic therapy using methylene blue (aqueous and coupled with liposomes) is effective for treating the ovarian malignancies and it will be capable of achieving complete eradication of visible tumours in patients with superficial lesions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s101030050028
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  • 92
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    The Monitoring of ALA-Induced Protoporphyrin IX Accumulation and Clearance in Patients with Skin Lesions by In Vivo Surface-Detected Fluorescence Spectroscopy (1999)
    Springer
    Lasers in medical science 14 (1999), S. 112-122 
    Details
    ISSN: 1435-604X
    Keywords: Keywords: Aminolaevulinic acid; Dermatology; Photodynamic therapy; Photosensitisation; Protoporphyrin IX; Skin lesions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract. The method of surface-detected fluorescence has been used to monitor the emission intensity from 5-aminolaevulinic acid (ALA)-induced protoporphyrin IX (PpIX) in lesions and corresponding adjacent normal skin. Three types of lesions were examined: psoriatic plaques, actinic keratosis and basal cell carcinoma. This study included a total of 14 human volunteers on whom ALA-induced PpIX formation and clearance was monitored for a total of 48 h post-ALA application. Both an ALA dose-ranging study, as well as a comparison of results between normal and lesional tissue at a fixed ALA dose, were carried out. For the dose range examined (10–30%), there was no ALA dose dependency of the PpIX fluorescence for any of the lesions tested. Although all three lesions tested did show enhanced PpIX fluorescence as compared with normal skin, there was considerable lesion-to-lesion variability. Thick psoriatic plaques seem to give longer PpIX retention times than those of thin lesions. Limitations of the surface-detected fluorescence methodology are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s101030050032
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  • 93
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    Changes in Local Hepatic Blood Perfusion During Interstitial Laser-Induced Thermotherapy of Normal Rat Liver Measured by Interstitial Laser Doppler Flowmetry (1999)
    Springer
    Lasers in medical science 14 (1999), S. 143-149 
    Details
    ISSN: 1435-604X
    Keywords: Keywords: Interstitial laser therapy; Liver; Perfusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract. Interstitial laser Doppler flowmetry was used to measure the effect of interstitial laser-induced thermotherapy on local blood perfusion in normal rat liver in the peripheral treatment region elevated to hyperthermic temperatures. The Nd:YAG laser emitting at 1064 nm was utilised as heat generation source. The plane-cut tip of an optical fibre was placed in the middle of the exteriorised left liver lobe. Blood perfusion and temperature were measured in the liver parenchyma 4 mm from the laser fibre. The temperature at the location of the liver temperature sensor was maintained at 41 or 44°C during 30 min by regulating the power of the heating laser. The laser Doppler signal was recorded during and after heat treatment, for a total time of 60 min. At 41°C, a significant increase in perfusion up to 1.3 times the initial value was observed 2–16 min after start of treatment. At 44°C, perfusion decreased continuously during and after treatment, and was significantly different from control 40 min after start of treatment. The results may be valuable in assessing the thermal response of tissues surrounding the target in interstitial laser-induced thermotherapy of liver tumours during conditions of normal blood flow.
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    URL: http://dx.doi.org/10.1007/s101030050036
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  • 94
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    Picosecond Laser Ablation of Dentine in Endodontics (1999)
    Springer
    Lasers in medical science 14 (1999), S. 168-174 
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    ISSN: 1435-604X
    Keywords: Keywords: Endodontics; Laser ablation; Nd:YAG laser; Picosecond laser; Root canal therapy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract . The interaction of picosecond laser radiation with human dental tissue was investigated in this study, in order to determine the ablation rates and the surface characteristics of the dentine by using scanning electron microscopy (SEM). Dentine ablation was performed by using tooth sections of different thicknesses (0.5–2.0 mm). Dental tissue samples were irradiated in air with the fundamental wavelength and first harmonic of a regenerative amplifier Nd:YAG laser system, at 1064 nm and 532 nm, respectively, with a pulse duration of 100 ps and a pulse repetition rate of 10 Hz. The results showed very clean craters surrounded by minimum melting of the surface of dentine when the 1064 nm pulses were used. In contrast, when the first harmonic 532 nm pulses were used, the SEM examinations revealed cracks and melting of dentine with irregular surface modification. Consequently, it seems that cleaning and shaping of the root canal walls during endodontic therapy with the picosecond Nd:YAG laser application may be possible in the future. The, as yet unexplored, field of the picosecond laser interaction with hard dental tissue is expected to be a potential alternative for powerful laser processing of biomedical structures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s101030050080
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  • 95
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    Photodynamic Inactivation of the Single Crayfish Nerve Cell: Dynamics of Electrophysiological Responses and Comparison of Photosensitisers (1999)
    Springer
    Lasers in medical science 14 (1999), S. 185-195 
    Details
    ISSN: 1435-604X
    Keywords: Keywords: Chlorins; Firing; Janus green B; Methylene blue; Neuron; Photodynamic effect; Photoheme; Photoporphyrin IX; Photosens; Photosensitisers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract . The study of single neuron response to photodynamic effect provides a means for the study of the dynamics of cytotoxic events leading to cell death and allows comparison of the phototoxicity of different photosensitisers. Isolated crayfish stretch receptor neurons were photosensitised for 30 min, then irradiated with a He-Ne laser (632.8 nm; 0.3 W/cm2) until irreversible firing cessation. The dynamics of neuron firing frequency were continuously recorded throughout. The following photosensitisers were studied: methylene blue, janus green B, protoporphyrin IX, chlorins e 6 and p 6, haematoporphyrin derivative (Photoheme) and sulphonated aluminium phthalocyanine (Photosens). Nerve cells were found to be insensitive to either He-Ne laser irradiation or photosensitisation alone, but very vulnerable to the photodynamic effect: neurons changed firing rate and died at nanomolar concentrations of photosensitisers. The dynamics of neuron responses was found to depend on photosensitiser type and concentration. The current approach provides a means of evaluation of initial threshold cell membrane alteration and cytotoxic events leading to cell death. The dependence of firing acceleration rate and neuron lifetime on photosensitiser concentration additionally allowed comparison of efficiencies of different photosensitisers. Photosens, Photoheme and chlorin p 6 were found to be the most potent photosensitisers: neurons responded to their photodynamic effects at concentrations as low as 1–5 nM.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s101030050083
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  • 96
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    Disinfection of the Optical Fibre of a Nd-YAP Laser Used in Dental Care (1999)
    Springer
    Lasers in medical science 14 (1999), S. 73-80 
    Details
    ISSN: 1435-604X
    Keywords: Keywords: Biocides; Disinfection; Laser; Optical fibre
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract. In order to set up a disinfection protocol, the tip of the optical fibre of an Nd-YAP laser, λ=1.34 μm, was contaminated in vitro with: Mycobacterium smegmatis (CIP 7326), Candida albicans (ATCC 2091), Bacillus stearothermophilus (ATCC 7953) or Streptococcus sanguis (ATCC 10556). It was then treated with various biocidal solutions, Septinol® V, glutaraldehyde 2%, ethanol 95° and NaOCl 6%, using one of two protocols: 10 s of contact, or 5 s of contact followed by 5 s of wiping. The latter technique proved to be the most effective. Whatever the biocidal solution used, all the bacteria adhering to the fibre were eliminated. The protocol was checked in vivo in the canals of 10 teeth presenting root canal infections. No bacteria withstood the treatment with Septinol® V. This treatment does not alter the qualities and performance of the fibre as far as light transmission is concerned.
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    URL: http://dx.doi.org/10.1007/s101030050024
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  • 97
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    Diode Laser Trabeculoplasty Versus Argon Laser Trabeculoplasty in the Control of Primary Open Angle Glaucoma (1999)
    Springer
    Lasers in medical science 14 (1999), S. 105-108 
    Details
    ISSN: 1435-604X
    Keywords: Keywords: Glaucoma, open angle; Intraocular pressure; Laser surgery; Trabecular meshwork; Trabeculoplasty
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract. A randomised prospective study was carried out to determine whether diode laser trabeculoplasty (DLT) is as effective as argon laser trabeculoplasty (ALT) in the control of primary open angle glaucoma (POAG). Forty eyes of 40 patients with uncontrolled intraocular pressure (IOP) despite maximum topical medication were entered into the study. Twenty eyes received DLT, spot size 100 μm, exposure time 0.2 s, mean power 1034 (±56.4) mW. Twenty eyes received ALT, spot size 50 μm, exposure time 0.2 s, mean power 528 (±44.7) mW. They were reviewed at 2 h, 2 and 8 weeks, and 3, 6, 12, 18 and 24 months after laser treatment. Two eyes were withdrawn from the DLT group and four from the ALT group because of uncontrolled IOP during follow-up. Of the remaining eyes in the trial, mean IOP reductions for DLT and ALT, respectively, were: 6 months 7.42 (±2.36) mmHg and 6.36 (±2.3) mmHg; 12 months 7.02 (±2.6) mmHg and 6.28 (±2.2) mmHg; 18 months 6.86 (±2.8) mmHg, 5.98 (±2.02) mmHg; 24 months 6.50 (±2.72) mmHg, 5.92 (±2.02) mmHg. There was a significant reduction in each laser group when IOP at each stage was compared with baseline (p〈0.001) (paired Student's t-test), but no significant difference between the two groups. In the ALT group peripheral anterior synechiae developed in four eyes and post laser pain in seven eyes. These complications were not noted following DLT. We conclude that DLT and ALT are equally effective in IOP control, but DLT is associated with less anterior segment inflammation.
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    URL: http://dx.doi.org/10.1007/s101030050030
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  • 98
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    Laser-Induced Thermotherapy (LITT) for Retreatment of Locally Advanced Recurrences of Breast Cancer (1999)
    Springer
    Lasers in medical science 14 (1999), S. 136-142 
    Details
    ISSN: 1435-604X
    Keywords: Keywords: Colour-coded duplex sonography; Laser induced thermotherapy; Minimal invasive therapy; Recurrent breast cancer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract. The effect of laser-induced thermotherapy (LITT) as a palliative method for treatment of patients with local recurrence of breast cancer is investigated. This report describes the use of interstitial laser photocoagulation to manage such lesions. The interstitial laser applications were performed in seven women with locally recurrent breast carcinoma on the chest wall after mastectomy. All patients had been heavily pretreated with conventional modes of therapy (radiotherapy, chemotherapy, hormonal therapy, surgical resection). A Nd:YAG laser with a wavelength of 1064 nm was used to heat the lesions. Heat expansion was controlled digitally and monitored by ultrasonography and colour-coded duplex sonography (CCDS). In five women this minimally invasive method enabled the precise coagulation of the subcutaneous tumour without destruction of the skin or ulceration, although these areas had been pretreated by irradiation up to 60 Gy. In two patients with extensive multiple metastases and with skin infiltration, secondary skin ulceration and delayed healing was observed. For palliative reasons, LITT under CCDS guide can aid in local control of chest wall recurrence following mastectomy in selected patients.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s101030050035
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  • 99
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    Killing of the Yeast and Hyphal Forms of Candida albicans Using a Light-Activated Antimicrobial Agent (1999)
    Springer
    Lasers in medical science 14 (1999), S. 150-157 
    Details
    ISSN: 1435-604X
    Keywords: Keywords:Candida albicansCandidosis; Hyphae; Lethal photosensitisation; Toluidine blue O; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract. Oral infections due to Candida albicans are a common occurrence in patients with acquired immunodeficiency syndrome (AIDS). The purpose of this investigation was to determine whether the yeast and hyphal forms of the organism could be killed using the light-activated antimicrobial agent toluidine blue O (TBO). Three variables were investigated: TBO concentration, laser light dose and pre-irradiation time (PIT). Irradiation with light from a helium neon (HeNe) gas laser used in conjunction with the photosensitiser TBO resulted in substantial kills of both the yeast and hyphal forms. Killing was light dose-dependent with 42 J being the most effective dose. The optimum PIT for the yeast form was 5 min, whereas killing of the hyphal form was not affected by PIT. The results of this study have shown that both forms of C. albicans are susceptible to lethal photosensitisation using TBO in conjunction with HeNe laser light, suggesting the possibility that this approach could be useful for eliminating the organism from diseased lesions in vivo.
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    URL: http://dx.doi.org/10.1007/s101030050037
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  • 100
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    Interstitial Laser Photocoagulation with Four Cylindrical Diffusing Fibre Tips: Importance of Mutual Fibre Distance (1999)
    Springer
    Lasers in medical science 14 (1999), S. 216-220 
    Details
    ISSN: 1435-604X
    Keywords: Keywords: Beamsplitter; Liver; Metastases; Nd:YAG; Tumour
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract . Simultaneous application of multiple fibres could increase the volume of coagulation produced with interstitial laser photocoagulation (ILP) for solid tumours. To take full advantage of the presumed synergistic thermal effect between the fibres, the optimal combination of laser power and distance between the fibres was investigated. Four fibres with a cylindrical diffusing tip of 2 cm length were used, coupled to an optical beamsplitter for Nd:YAG light (four channels, maximal variation 9.5%, transmission 〉85%). The distance between the fibres was 1, 1.5, 2, 2.5 , 3 or 4 cm with a power output of either 4, 5, 6 or 7 W/fibre; energy per fibre was constant at 1800 J by adjusting exposure time. After laser application, dimensions of the coagulated lesions were measured. The optimal mutual fibre distance was 2 cm ( p〈0.01) at all power levels. This resulted in lesions with a mean (SD) volume of 44.5 (2.1) cm3 and a largest diameter of 5.1 (0.4) cm at 7 W/fibre. Smaller distances between the fibres resulted in smaller lesions with central carbonisation, whereas larger distances resulted in four separate zones of coagulation. It was concluded that simultaneous application of four interstitial fibres may result in a considerable increase of volume of coagulation. Fibre position and mutual fibre distance determines whether synergism of the coagulative effect occurs.
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    URL: http://dx.doi.org/10.1007/s101030050087
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