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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Engineering with computers 1 (1985), S. 27-37 
    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
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  • 2
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    Engineering with computers 1 (1986), S. 127-147 
    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 One of the major problems in developing computeraided design software is the establishment of effective man-machine communication. This paper describes a computer-aided plate girder design software package and its man-machine interface using natural language processing techniques. The natural language interpreter takes advantage of the user's communication and technical skills and accepts commands in the user's native language. The user can verify the correct interpretation of the commands from the responsive graphic display of the design.
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  • 3
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    Engineering with computers 1 (1986), S. 175-191 
    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 With the aid of the supercomputer we have performed three-dimensional simulations in practical cpu time. At the same time, though, huge amounts of output data must be treated automatically by post processors, so that only necessary information will be extracted and changes of models, mesh subdivisions, or boundary conditions will be taken into account. This type of information processing cannot be attained by conventional postprocessors, and a new concept of postprocessing and system must be developed in the sense of computer-aided engineering or computer diagnosis. We present a computer tomographic system COMTOS-BEM based on three-dimensional boundary element analysis; it houses its own geometric modeling and automatic mesh generation. Furthermore, it supports design feedback reactions to change modeling or meshing, make recalculations, and renew boundary conditions. In this paper, we state the basic concept of the proposed computer diagnosis system and present the necessary geometric modeling and processing and boundary element formulations. Some numerical examples illustrate the validity and effectiveness of our system in practice.
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  • 4
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    Engineering with computers 1 (1986), S. 205-215 
    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 computerized procedure for symbolic manipulations and FORTRAN code generation of elasto-plastic material matrix for finite element applications is presented. Special emphasis is placed on expression simplifications during intermediate derivations, optimal code generation, and interface with the main program. A systematic procedure is outlined to avoid redundant algebraic manipulations. Symbolic expressions of the derived material stiffness matrix are automatically converted to RATFOR code which is then translated into FORTRAN statements through a preprocessor. To minimize the interface problem with the main program, a template file is prepared so that the translated FORTRAN statements can be merged into the file to form a subroutine (or a submodule). Three constitutive models; namely, von Mises plasticity, the Drucker-Prager model, and a concrete plasticity model, are used as illustrative examples.
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  • 5
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    Engineering with computers 11 (1995), S. 94-102 
    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.
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  • 6
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    Engineering with computers 11 (1995), S. 145-156 
    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.
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  • 7
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    Engineering with computers 11 (1995), S. 167-172 
    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).
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  • 8
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    Engineering with computers 11 (1995), S. 227-245 
    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.
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  • 9
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    Engineering with computers 11 (1995), S. 213-226 
    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.
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  • 10
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    Engineering with computers 12 (1996), S. 46-61 
    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.
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  • 11
    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.
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  • 12
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    Engineering with computers 12 (1996), S. 94-106 
    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.
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  • 13
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    Engineering with computers 12 (1996), S. 120-141 
    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.
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  • 14
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    Engineering with computers 12 (1996), S. 144-154 
    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.
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  • 15
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    Engineering with computers 12 (1996), S. 178-185 
    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.
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  • 16
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    Engineering with computers 12 (1996), S. 186-210 
    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.
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  • 17
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    Engineering with computers 13 (1997), S. 48-64 
    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.
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  • 18
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    Engineering with computers 13 (1997), S. 65-86 
    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.
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  • 19
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    Engineering with computers 13 (1997), S. 99-111 
    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.
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  • 20
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    Engineering with computers 13 (1997), S. 134-152 
    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.
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  • 21
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    Engineering with computers 13 (1997), S. 165-174 
    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.
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  • 22
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    Engineering with computers 13 (1997), S. 185-196 
    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.
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  • 23
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    Engineering with computers 13 (1997), S. 211-221 
    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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  • 24
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    Engineering with computers 13 (1997), S. 235-243 
    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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  • 25
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    Engineering with computers 14 (1998), S. 14-22 
    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.
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  • 26
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    Engineering with computers 14 (1998), S. 36-47 
    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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    Engineering with computers 14 (1998), S. 59-72 
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    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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    Engineering with computers 14 (1998), S. 73-80 
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    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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    Engineering with computers 14 (1998), S. 81-92 
    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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    Engineering with computers 2 (1987), S. 167-183 
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    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 Computer modeling of mixed-mode crack propagation has rarely been attempted. This is because of the difficulty in updating the geometrical description to represent the changing crack geometry. The development of two interactive, graphical fracture propagation systems is described here. The Finite Element Fracture Analysis Program—Graphical (FEFAP-G) is a two-dimensional fracture propagation system. The BEM3D is a three-dimensional boundary element fracture propagation system. In addition, the implementation of the BEM3D analysis program in a configuration formed by an FPS-264 processor attached to a VAX-11/750 used as host computer is described. The results show that a realistic three-dimensional boundary element analysis of crack propagation is not only feasible with the aid of attached processors, but it can have its total time reduced by factors of the order of hundreds when compared to VAX alone statistics. In an example problem concerning fatigue crack propagation in a stiffened wing skin, both FEFAP-G and the BEM3D are employed to illustrate the utility of the fracture propagation systems.
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    Engineering with computers 2 (1987), S. 199-208 
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    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract An expert consultant and teaching aid has been developed to aid users of the MSC/NASTRAN (MacNeal-Schwendler Corp, Los Angeles, CA, USA) finite element code in the modeling process with two-dimensional elements. Written in LISP and LOOPS, an object-oriented programming language, the system, known as PLASHTRAN, allows engineers to work in a natural environment to obtain modeling recommendations. The program performs efficiently, especially when iterations in design require changes in the finite element model. The easily expandable modeling framework allows the knowledge base to incorporate new information.
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    Engineering with computers 2 (1987), S. 219-238 
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    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract This paper presents a design strategy in which structural components are designed automatically by applying three types of knowledge: knowledge in a design standard; “textbook” knowledge of structural, material, and geometrical relationships; and knowledge representing designer-dependent design expertise. The design strategy selects from the designer-dependent knowledge source the behavior limitations—limit states of an object in a given stress state—to consider, translates the behavior limitations into a subset of corresponding standard requirements, generates a set of constraints from the requirements and the relations in the knowledge-base of “textbook” relationships, satisfies the constraints, and then checks the satisfaction of all remaining applicable requirements. By using this design strategy, it is possible to construct a knowledge-based design strategy that is standard independent, so that the same design process can be performed regardless of which design standard is explicitly represented. The design strategy described has been implemented in a prototype knowledge-based system, SPEX, which has a blackboard architecture similar to, but much simpler than, that of HEARSAY. The blackboard represents the level of abstraction through which a component design progresses. The knowledge-base in SPEX consists of several knowledge sources that perform portions of the component design task. Control of the design process knowledge sources in SPEX is rule-based.
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    Engineering with computers 3 (1987), S. 21-33 
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    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract This paper presents an analytical method for acoustic forced pulsations of reciprocating compressor pipeline systems have a treelike structure that consists of an arbitrary number of branchings with optional elements—pipes, volumes, orifices, and so on. The plane wave acoustic model is used to describe the method, and the solution works by using an extended Schmidt-Kuhlmann-type approach. On the basis of a graph and matrix interpretation of the structure, a generalized algorithm is developed for determining the actual terms that describe the transfer properties of the system and to help calculate the acoustic pressure and velocity pulsations. The algorithm makes it possible to mechanize programming in the case of both natural frequency and forced pulsation calculations. The program package developed here for the personal computer can be directly applied in the design practice with success. It is also applicable to other linear systems with treelike structures.
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    Engineering with computers 3 (1987), S. 69-86 
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    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract The development of an expert system for the postevent assessment of reinforced concrete structures subjected to severe loading environments, such as those that correspond to blast and shock effects, is presented and discussed. Initially, the observed behavioral aspects of the structures are presented, then a background discussion of the requirements from an expert system is given, and finally, the specific details for the present approach are examined. Examples of rules and of a typical run are presented, and the results are compared to information obtained from previous studies on the same structures.
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    Engineering with computers 3 (1987), S. 87-99 
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    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Extracting information about contact between two convex bodies from the measured force vector is a prerequisite for any fine compliant motion control strategy. Contact information contains the direction and orientation of the contact surface normal and its relative location and orientation with respect to the compliant reference frame system. A method for interpreting the contact force feedback during compliant robot motion control, using kinematic screws, is presented. Domain specific rules combined with partial a priori knowledge of mating parts geometry and interpreted force signals are used to reason and make inferences about the initial contact configuration. The likely contact surfaces are predicted and point(s) or line(s) of contact are fully defined. These surfaces are idealized and represented by quadratic equations or polyhedral surfaces. The geometric properties of surfaces at the contact location are used to select the contact configuration when multiple solutions exist. An algorithm for predicting the Expected Contact Configuration (ECC) has been developed and is illustrated here with examples. Experimental validation of the developed expert system prototype, using a 6R manipulator, a six-axis force sensor, and a host computer is described.
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    Engineering with computers 3 (1988), S. 121-136 
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    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract This paper reviews the most relevant literature dealing with the development of computer environments for the conceptual design of mechanical systems and assemblies. Selected literature is reviewed and discussed in relation to meeting the following requirements of such an environment: (1) representing and supporting top-down design, (2) representing and supporting multiple functional viewpoints, (3) representing functional knowledge, (4) representing spatial relationships and geometry, (5) maintaining consistency, and (6) providing analysis and other support. An appendix listing related readings is included.
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    Engineering with computers 3 (1988), S. 137-148 
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    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract The paper presents an expert system to assist in the field inspection of existing concrete dams within the context of a preliminary risk assessment. The paper describes the engineering knowledge and reasoning required to conduct a deterministic field evaluation of the structural stability of the dam. The symptoms and failure modes identified by the expert system along with the required knowledge and procedures are organized in a structured knowledge tree. The instantiation of the frames and firing of the rules for each consultation traces part of the inference tree contained in the structured knowledge tree. Interaction between nearly decomposable problems are executed with metaknowledge procedures, shared rule groups, and active values. Examples are provided.
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    Engineering with computers 3 (1988), S. 157-165 
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    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract The paper describes automated generation and editing schemes together with the development of computer-aided geometric models for general applications. For the construction of general finite element models of complex shapes, conventional approaches typical of wireframe, surface, or solid modeling cannot be effectively utilized for generating continuum solid models as well as discrete models simultaneously. In view of these facts, features to generate and model two-dimensional as well as threedimensional continuum and discrete models by isoparametric mapping/solid geometrical modeling techniques via a common interactive processor are described. The proposed scheme is demonstrated for modeling structural, thermal, or flow networks that are commonly encountered in engineering applications. In a research environment, the techniques addressed in this paper should prove to be very useful in providing flexibility and thereby significantly reducing the work load of frequent CAD users.
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    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract This paper describes basic research issues and our experience in the development of an intelligent modeling environment for use with a large engineering analysis code. The intelligent environment, the Athena Aide, is a working prototype system that assists analysts in the preparation of models for the ATHENA thermal-hydraulics code. The paper includes the background and basis for our research and descriptions of the analysis code and the intelligent environment, and discusses research topics addressed during the development including design goals, general and specific design issues, information management and representation issues, and user acceptance issues related to the model construction task. Our research has shown that data management is a fundamental consideration during the model construction task and an intelligent environment is a valuable assistant to the analyst in that regard. Providing modeling advice commensurate with the general nature of the analysis code was found to be extremely difficult. For modeling tasks where specific heuristic knowledge has accumulated, useful modeling advice can be provided.
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    Engineering with computers 3 (1988), S. 207-223 
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    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract In recent years there has been an increasing interest in the integration of data base management systems (DBMSs) into the CAD environment. The motivation for this interest is discussed and several problems are identified that have to be solved in order to yield a genuine coupling of DBMSs and CAD systems. A solution to these problems is proposed in the form of a new architecture for a CAD-DBMS. Based on this, a preliminary implementation is outlined that follows a rapid prototype approach, and in wh ich an access as well as a transaction manager were realized for a software-based fileserver/workstation topology. Some directions for future work are described.
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    Engineering with computers 3 (1988), S. 183-199 
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    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract This article addresses the need for engineers to have a working knowledge of the fundamental structures of computer programming languages. In pursuit of this, it briefly looks at the history behind four of the more well-known programming languages. It then attempts to identify, and to look critically at, the attributes of programming languages that significantly affect the production of engineering software. The four “traditional” procedural programming languages chosen for review are those intended for scientific and general purpose programmin—FORTRAN-77, C, Pascal, and Modula-2. These languages are compared and some general observations are made. The emphasis of this article is on the attributes, characteristics, and components of programming languages that are important to software development and maintenance. Consequently, the comparison itself is of secondary importance, with the actual methodology of comparison given prominence in order that professional engineers who need to develop engineering software are able to make rational decisions about the choice of a programming language. Choosing an appropriate language can be a complex task and many factors must be considered. Therefore, in this article the fundamental structures, constructs, and attributes of programming languages are discussed, with very little attention given to the specific syntax of any particular language.
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    Engineering with computers 4 (1988), S. 3-10 
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    Notes: Abstract The opportunities of the information age present a real challenge to business management today. To meet this challenge, and to realize the true benefits of information technology, management must get involved and provide leadership in defining the business direction for an enterprise. It is through this involvement that the enterprise can apply technology to make the maximum impact on how business is conducted. Major information system development projects at General Dynamics Fort Worth will impact the way product definition data is managed and provide an example of how information technology can change the way we do business.
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    Engineering with computers 4 (1988), S. 19-26 
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    Notes: Abstract A general structural design procedure, including general development and maintenance steps, is outlined from a data requirements perspective. Within each phase of the design process, certain data is required for the undertaking and completion of each design step. As the various steps in the design process such as component and prototype testing and in-service experience generate new or additional data, that information should be incorporated into the data banks for use in current and future designs.
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    Engineering with computers 4 (1988), S. 53-63 
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    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract The integrated analysis capability (IAC) provides a computational environment that supports the unique needs of engineering analysis groups concerned with interdisciplinary problems. An essential part of IAS is the data management system, which is designed both to maximize computational efficiency and to support a full range of data query and manipulation. This paper described data management issues that we have found to be of critical importance in the IAC development. Because the computational environment of a system such as IAC has a strong influence on the software design trades and decisions, the paper also summarizes the overall system architecture and some of the developments relative to technical modules and data flow requirements. The information presented here is intended to aid potential users in evaluating and selecting an integrated capability, as well as software developers faced with the task of creating or expanding such a capability.
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    Notes: Abstract This paper presents a study and comparison of shape design sensitivity analysis algorithms that are based on the continuum adjoint variable method, the continuum direct differentiation method, and the finite difference method, implemented on a supermini computer with an attached array processor. The basic algorithms and their differences in evaluating shape design sensitivity coefficients are outlined. A solution method for solving a system of equations, using a general sparse storage technique, is used for numerical implementation of shape design sensitivity analysis. It is found that computing shape design sensitivity coefficients using the direct differentiation method is significantly more efficient than using the adjoint variable method or the finite difference method. A detailed performance evaluation of the methods, using an attached array processor, is presented. The performance of the attached array processor, compared to a supermini computer is shown to depend strongly on the type of computations to be carried out. When only parts of a program are running on an attached array processor, the CPU time distribution among the different subroutines of the program can change significantly, compared to using the host processor only.
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    Engineering with computers 3 (1988), S. 149-156 
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    Notes: Abstract An optical strain measurement system was developed that includes computer processing of stereoscopic picture data of marks painted on the specimen. This system allows us to measure large strains in specimens with curved surfaces as well as plane surfaces even at elevated temperatures. The results of a verification test performed on a bellows specimen at room temperature have shown that the strain error of this measurement system is allowable considering the limitation of the apparatus.
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    Engineering with computers 3 (1988), S. 181-181 
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    Engineering with computers 3 (1988), S. 201-205 
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    Notes: Abstract Often a computer-aided design system acts merely as a storehouse for a collection of graphical entities. It has no knowledge of how these interrelate or what the purpose is of the design that they represent. The work described is an initial attempt to enable the user of a system interactively to provide information of this type. This is done in terms of constraints upon the geometric entities that are defined, along with these entities themselves, in a user interface language.
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    Engineering with computers 3 (1988), S. 225-241 
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    Notes: Abstract A brief review is made of the fundamental concepts and basic issues of parallel processing. Discussion focuses on mechanisms for parallel processing, construction and implementation of parallel numerical algorithms, performance evaluation of parallel processing machines and numerical algorithms, and parallelism in finite element computations. A novel partitioning strategy is outlined for maximizing the degree of parallelism on computers with a small number of powerful processors.
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    Engineering with computers 4 (1988), S. 1-1 
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    Engineering with computers 4 (1988), S. 11-17 
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    Notes: Abstract Implementers of engineering data base management systems inherit a legacy of existing software and data that must be integrated into the new system with minimum disruption of ongoing activities. Some critical issues addressed here include changes in software engineering practices, impact on user training and procedures, and problems connected with traditional or parochial interests. The material covered describes some experiences in coping with these “legacy factors” during the recent McDonnell Aircraft Company (MCAIR) integrated data base implementation.
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    Engineering with computers 4 (1988), S. 27-37 
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    Notes: Abstract The integrated design support system (IDS) is a concept for capturing the “critical” technical engineering information necessary to perform the functions of maintenance, modification, repair, and reprocurement of Air Force weapon systems. The program will first construct an architecture to define the required information. Next, IDS will construct prototype software to acquire, store, distribute, and perform configuration management on the data. The program will conclude with software simulation of the full-scale IDS system operating in a production environment to determine performance characteristics together with development and operatonal costs for the system.
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    Engineering with computers 4 (1988), S. 39-52 
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    Notes: Abstract Effective management of engineering information is critically needed for the design of future complex engineering systems. Yet engineers are not trained in engineering data base management concepts. To help address this issue, a prototype integrated design system has been developed for the Air Force to aide research and instruction on key integration concepts, including (1) the use of a shared data base to eliminate redundancies and inconsistencies; (2) the use of a relational data base management system to store, locate, and retrieve data from the shared data base; (3) the development of interfacing programs to act as interpreters between the application programs and the common data base; and (4) the role of executive software to manage the integrated system. Key software used includes a computer-aided design system, a structural analysis program, various graphics packages, and a relational data base management system. To assess system flexibility, additional programs were added to the system. The design of the data base proved to be an important step in this implementation. Several methodologies useful in the design of the data base were investigated and subsequently used to organize the data base for the integrated design system. Results discussed include system development, and applications, as well as the effectiveness of the integrated system's configuration.
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    Engineering with computers 4 (1988), S. 75-85 
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    Notes: Abstract The explosion of interest in computerized material property data bases and intelligent knowledge systems for flexible manufacturing processes has resulted in two significant developments in the last couple of years: the incorporation of the National Materials Property Data Network, Inc. (MPD Network), and the formation of ASTM Committee E-49 on Computerization of Material Property Data. The MPD Network has the mission of providing engineers and scientists with easy on-line access to worldwide sources of reliable, well-documented material property data. The status of its pilot network and plans for the future are outlined herein. ASTM Committee E-49 has the mission of developing and providing guidelines and standards to aid the builders, maintainers, and suppliers of data bases in meeting the needs of industry and in establishing compatible and consistent sources capable of sharing data. Also reported in this paper is the early progress of the Technical Committee of the MPD Network in establishing guidelines for the evaluation of data, recognizing that there are a number of aspects of data source building and management requiring audit as well as the data itself. It is important that sources of material performance data are well characterized, and that the nature and reliability of the information is conveyed to the user. The further development of guidelines and standard practices in this area will also be dealt with by ASTM Committee E-49. A brief overview of other major material property data base building activities in the United States is also provided.
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    Engineering with computers 4 (1988), S. 99-105 
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    Notes: Abstract This paper describes the content and logical structure of an engineering data base, to be constructed from direct technical information, for use with input-output (IO) models of the national economy. These models, which until now have relied almost exclusively on accounting information describing past economic transactions, can now be extended to analyze the future prospects for the U.S. economy and its individual sectors in terms of detailed technical decisions taken at the sites of production. The basic IO data base describes each sector's input in terms of its use of given amounts of goods and services produced in all sectors, per unit of its output. The new data base will distinguish the individual activities carried out within a sector, specify the important technical alternatives for each activity, and describe each alternative in terms of inputs of the required goods and services. The structure of the new data base accommodates the quantification of both production and “overhead” activities and their integration, and its implementation in stages is facilitated by the fact that it is a generalization of the structure of existing IO data bases.
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    Engineering with computers 5 (1989), S. 39-46 
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    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 construction of offset curves is an important problem encountered often in design processes and in interrogation of geometric models. In this paper the problem of construction of offsets of curves lying on the same parametric surface is addressed. A novel algorithm is introduced, whose main feature is the use of geodesic paths to determine points of the offset. The offset is then approximated in the underlying surface parameter space by B-splines interpolating data points obtained by traveling a known distance along the geodesics departing from corresponding points of the progenitor in a direction perpendicular to the latter. A comprehensive error checking scheme has been devised allowing adaptive improvement of the approximation of the offset. The applicability of the algorithm is demonstrated by number of numerical examples.
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    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Intelligent computer-aided design (CAD) emulates the human activity of design so that production planning, decision making, and inventive design can be performed by computers. Based on the history of human experience in engineering design, a formalized and systematic approach to design should include procedures from (1) conceptual design, (2) layout design, and (3) numerical optimization. The highest level within such a system should be responsible for specifying and symbolically optimizing skeleton structures of generic (nonspecific) elements within the design process that are eventually to be specified uniquely (pinned down) and ultimately optimized numerically. Planning plays a key role in such a system. Planning has been utilized as a tool for process organization within the knowledge domains of chemical engineering, electrical engineering, manufacturing, as well as for general problem formulation and solution. State estimation, subtask scheduling, and constraint propagation have been found to be factors of prime importance in this type of problem. Problems associated with the implementation of a planning strategy within a knowledge-based system for mechanical engineering design optimization are discussed. A hypothesis for planning is put forth and examined within the context of a model of the mechanical design optimization process. An example that demonstrates the applicability of this approach to mechanical power transmission design is considered.
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    Engineering with computers 4 (1988), S. 197-203 
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    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract An approach to structural analysis is presented in which object-oriented data structures make it possible to arrange computational tasks in a unique fashion. A general matrix-free solution algorithm for use with arbitrary assemblages of linearly connected objects is presented, followed by an overview of a prototype structural analysis program built entirely on such an object-oriented data structure. The principal result is due to the flexibility inherent in this type of data structure, which makes it possible to analyze structural models incrementally as they are developed. Although certainly useful in traditional contexts, the parallel nature of the scheme could be particularly powerful in a multiprocessor environment.
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    Engineering with computers 5 (1989), S. 79-89 
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    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract This paper introduces a strategy for the construction of object-oriented knowledge frameworks. Global control programs, which are traditionally used for manipulating structured representations, have been replaced by domain-specific resources. This new approach offers increased efficiency and simplified development of knowledge-based expert systems for problem domains that deal with a variety of complex structured information. A theoretical foundation is laid for the representation of knowledge, starting with the adoption of a simple schema for structuring stereotypical information. Data and method abstraction is achieved by installing knowledge frames into part of an object-oriented class system that supports procedural attachment and object communication. This allows frame specialization using domain-specific resources and subsequent construction of modular systems with these specialist frames. Editors are introduced for the alteration of data primitives used in declarative representation. Algorithms, which operate on these data primitives, are given for frame instantiation, data access, and user-directed inference. Examples from structural engineering are used throughout the paper to illustrate the practical application of object-oriented knowledge frameworks.
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    Engineering with computers 4 (1988), S. 239-249 
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    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract The needs of engineers in their interaction with engineering data bases are very different from those of their counter-parts in the business world. Business data base management system interfaces typically provide only a single mode of textual communication, usually a structured query language. However, in an idealengineering data base interface, an engineer would be able to define constraints, give examples, point at parts of pictures, and (sometimes) use several modes of communication simultaneously. The paper presents an example from an engineering design application to show how a traditional query language can be enhanced to accommodate the engineering needs. The paper further describes a conceptual approach for multimodal engineering data base interface combining multipurpose graphics, an engineering query language, and other interface methodologies in an engineering workstation environment.
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    Engineering with computers 5 (1989), S. 13-22 
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    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract The problem of optimum structural design by passive control is stated in a nonlinear programming form. A solution procedure, based on a successive selection of design and control variables, is presented. Neglecting the implicit analysis equations, the solution becomes independent of the control variables and a lower bound (LB) on the optimum can easily be obtained. The control variables are then selected to satisfy all constraints. If this cannot be achieved, the LB constraints are modified and the control variables are chosen for the revised optimal design. These two steps are repeated until the final optimum is reached. Employing the proposed procedure on various structural systems subjected to static loads showed that the final optimum has been achieved after a very small number of iteration cycles. The numerical examples illustrate a solution with two types of control devices: a linear spring device and a limited displacement device. It has been found that the final optimum is often identical or close to the initial LB solution. Savings of 14 to 63 percent in weight, compared with conventional optima without control, have been demonstrated for some common structures.
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    Engineering with computers 5 (1989), S. 23-38 
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    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract This paper covers in more detail the material that was introduced in Ref. [1] and describes the final engineering reasoning and knowledge used for an expert system to assist during the field inspection of existing concrete dams. The knowledge base of this expert system was created by combining the traditional expert system approach with the reasoning procedures of qualitative physics. The traditional expert system approach was used to identify the shallow knowledge pertaining to the problem, and qualitative physics was used to identify the deep knowledge. The deep knowledge structured and organized the identification and representation of the shallow knowledge. The expert system uses shallow knowledge to combine a qualitative expert reasoning with a quantitative procedural evaluation of the stability of a dam. The present paper concentrates on the description of the engineering knowledge and Ref. [2] will concentrate on the artificial intelligence issues associated with the knowledge acquisition and representation associated with this expert system. The validation process compared results obtained by the expert system with those obtained by independent field inspection experts. Some of the results are presented here.
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    Engineering with computers 5 (1989), S. 205-219 
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    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract An expert system, ETUDES—Expert Time integration control Using Deep and Surface Knowledge System, which addresses the determination of the timestep for time integration of linear structural dynamic equations is described. This time-step may also be applicable for a moderately nonlinear simulation of the same structure. The program also determines whether an explicit or implicit method is most efficient for the particular simulation. A production rule programming system written in OPS5 is used for the implementation of this prototype expert system. Issues relating to the expert system architecture for this application, such as knowledge representation and structure, as well as domain knowledge are discussed. The prototype is evaluated by measuring it's performance in various benchmark model problems.
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    Engineering with computers 5 (1989), S. 221-234 
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    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract In this paper we introduce techniques that allow us to define a posteriori error estimators via well-known recovery techniques. These allow us to construct a posteriori error estimators for relatively general problems. Further, we introduce new adaptive procedures that make use of these estimators and, in particular, describe anh-p procedure that is simple to implement and that, as numerical experiments have shown, attains an accelerated rate of convergence expected from theh-p version.
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    Engineering with computers 5 (1989), S. 259-259 
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    Engineering with computers 5 (1989), S. 177-193 
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    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract This paper presents an algorithm for the generation of Delaunay triangulations for general nonmanifold geometric models. Octree concepts are used for point placement and providing the linear, with respect to the number of elements, growth rate of the algorithm. Compatibility and classification procedures are used in conjunction with point injection procedures to ensure that the final Delaunay triangulation is a geometric triangulation of the domain of interest.
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    Engineering with computers 5 (1989), S. 161-175 
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    Notes: Abstract This paper describes a method for generating tetrahedral meshes. The algorithm, based on the Delaunay triangulation, can treat objects of essentially arbitrary complexity. In order to preserve the surface triangulation of solid objects, it is necessary to override the Delaunay property and redefine the triangulation when points are introduced that are close to solid boundaries. Details of this constrained Delaunay algorithm are presented and an efficient implementation of the triangulation method is described. Techniques for controlling the distribution of mesh points and tetrahedron quality are also discussed.
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    Engineering with computers 5 (1989), S. 195-204 
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    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract This paper shows that control logic may be separated from analysis software and that a knowledge-based expert system can use this logic to perform interactive computation. Heuristics that control a simple interactive finite element analysis program are represented using a rule-based format and are used by a goal-driven logic processor to invoke analysis activity. Traditional algorithm-oriented control and the proposed knowledge-based control are compared in a simple displacement computation scenario to identify the advantages/disadvantages of the two approaches. General activities and constraints, practical methods of reasoning and representation, and knowledge-based expert systems are discussed with emphasis on applications to interactive finite element analysis. An analysis control expert system has been developed for use in the numerical analysis of two-dimensional linear problems in solid and structural mechanics. An example problem is used to clarify the methods used to direct activity and to identify the problems associated with conditional task processing for interactive analysis. The main difference between the analysis program described in this paper and conventional analysis programs is related to the control architecture. The general conclusion of this paper is that knowledge-based control is more effective and flexible than algorithm-oriented control.
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    Engineering with computers 5 (1989), S. 235-247 
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    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract This paper discusses an automatic, adaptive finite element modeling system consisting of mesh generation, finite element analysis, and error estimation. The individual components interact with one another and efficiently reduce the finite element error to within an acceptable value and perform only a minimum number of finite element analyses. One of the necessary components in the automated system is a multiple-level local remeshing algorithm. Givenh-refinement information provided by an a posteriori error estimator, and adjacency information available in the mesh data structures, the local remeshing algorithm grades the refinement toward areas requesting refinement. It is shown that the optimal asymptotic convergence rate is achieved, demonstrating the effectiveness of the intelligent multiple-level localh-refinement.
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    Lasers in medical science 1 (1986), S. 3-3 
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    Lasers in medical science 1 (1986), S. 19-24 
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    Keywords: Neodymium-YAG laser ; Optical microsurgery ; Optical breakdown ; Resonators
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    Topics: Medicine , Physics , Technology
    Notes: Abstract We report the development of an efficient and compact neodymium-doped yttrium aluminium garnet (Nd-YAG) laser for eye microsurgery. High efficiency and excellent multimode beam quality were obtained by use of a reflecting close-coupled cavity. Stable and unstable resonator configurations were compared. Some experiments performed with this laser are presented and discussed.
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    Lasers in medical science 1 (1986), S. 5-12 
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    Keywords: Photosensitization ; Porphyrins ; Cancer therapy ; Membrane damage
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    Topics: Medicine , Physics , Technology
    Notes: Abstract When mammalian cells are exposed to light in the presence of photosensitizers, such as porphyrins, a number of reactions takes place. The most important photoproduct is singlet oxygen, which reacts with and degrades a variety of biomolecules. This species can travel only about 0.1μm in a cell during its lifetime. Therefore, the structures most exposed to photodamage are those containing high concentrations of sensitizer. For porphyrins, membranes and mitochondria are such structures. Photosensitized damage to mitochondria and membranes has been observed by several techniques. The incubation time with sensitizers is critical since the rates of accumulation of sensitizer are different at different cellular locations. Several other aspects of the action of photosensitizers are reviewed: Have sublethal doses any effect on proliferation and DNA? How can photodynamic treatment act selectively on tumour tissue? Should photodynamic cancer treatment be combined with other therapies? Does photodynamic therapy work under low oxygen concentrations?
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    Lasers in medical science 1 (1986), S. 25-31 
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    Keywords: Laser laparoscopy ; CO2 laser ; Endometriosis ; Adhesions ; Infertility
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    Topics: Medicine , Physics , Technology
    Notes: Abstract Adhesions and endometriosis are commonly encountered among patients presenting with pelvic or lower abdominal pain and also in a significant proportion of infertile patients. Laparoscopic investigation is usual in patients with these problems, and it has been possible to perform endoscopic surgery with special scissors and electrodiathermy. These methods can cause troublesome bleeding, and the diathermy produces high temperatures which can be hazardous if used in the vicinity of the bowel. The carbon dioxide laser can be used endoscopically to vaporize deposits of endometriosis and adhesions with great precision and virtually no bleeding. One hundred consecutive patients with endometriosis or adhesions were treated with the CO2 laser laparoscope and followed up for at least a year. Seventy-five per cent of patients with pain due to endometriosis were cured, and 68% of patients were better after laser laparoscopic adhesiolysis. Pregnancy rate in the previously infertile group with endometriosis was 64%. There were no complications due to the intra-abdominal use of CO2 laser energy under endoscopic control, although there is a need for a controlled trial. It appears that in the hands of an experienced laparoscopist this technique is safe and effective.
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    Lasers in medical science 1 (1986), S. 33-39 
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    Keywords: Haematoporphyrin derivative ; 580 nm emission ; Time-resolved fluorescence microscopy
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    Topics: Medicine , Physics , Technology
    Notes: Abstract Continuous wave and time-resolved fluorescence microscopy have been extensively used to characterize the behaviour of haematoporphyrin derivative (HPD) both in solution and in single cells. In this work, we report experimental evidence for the presence of a 580 nm-emitting species, occurring as a consequence of modifications in HPD induced by the cellular microenvironment. The fact that the formation of this ‘modified’ species seems to be favoured in tumour cells might increase sensitivity in the diagnostic use of HPD for the localization of early-stage tumours.
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    Lasers in medical science 1 (1986), S. 81-84 
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    Lasers in medical science 1 (1986), S. 85-86 
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  • 77
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    Keywords: Argon dye laser ; Photodynamic therapy ; Gastric cancer ; Adenocarcinomas
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    Topics: Medicine , Physics , Technology
    Notes: Abstract Twenty-eight patients with gastric cancer were treated by photodynamic therapy. Haematoporphyrin derivative was used as a photosensitizer and an argon dye laser as a light source. Histologically, all tumours were adenocarcinomas. On the basis of endoscopy, 17 cases were categorized as early-stage cancer and were classified as type IIc (10 lesions), Ha (three lesions), combined type IIc and type III (three lesions) and type I (two lesions). In 11 patients with advanced-stage cancer, endoscopy showed one case of Borrmann I, three of Borrmann II, six of Borrmann III and a single case of Borrmann IV. In the 17 patients with early-stage cancers (18 lesions), complete remission was obtained in 10 patients (11 lesions). Of 13 resected cancers complete remission was confirmed in six lesions on the basis of detailed histological examination of resected specimens. In the advanced stage tumours all 11 patients showed incomplete remissions. It is considered that an incomplete response in the early-stage cancers is due to insufficient light dosage because of the wide area of tumour, because the site of the lesion is anatomically difficult to photoradiate and because the invasion extends to the muscular layer and serosa.
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  • 78
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    Keywords: Laser angioplasty ; Excimer laser ; Photoablation ; Haemolysis
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    Topics: Medicine , Physics , Technology
    Notes: Abstract The effects of three ultraviolet excimer laser wavelengths on normal and atheromatous human cadaver aortic wall are presented. Ultraviolet radiation successfully ablates vessel wall; the dose response is greatest at 249 nm followed by 193 nm and 351 nm, where the effect is negligible for the equivalent energy dose. Wavelengths 249 and 193 nm have a selective effect on fibrous atheroma; ablation proceeds at a higher rate in this tissue. Non-linear effects observed at 249 nm may be due to thermal as well as photoablative mechanisms. In addition, blood samples were exposed to all three wavelengths and potassium concentrations were measured; the dose of energy required to produce tissue ablation may also produce significant haemolysis and hyperkalaemia at 249 and 193 nm but not with 351 nm. This finding may be important for coronary angioplasty but less so for peripheral work. The wavelength that produces the strongest dose response is 249 nm; this is the wavelength for which a fibre-optic delivery system should be developed.
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  • 79
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    Keywords: Argon laser ; Superficial venular dilatation lower limb ; Arborizing telangiectasia
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    Topics: Medicine , Physics , Technology
    Notes: Abstract The response of vascular dilatation of the lower limb to treatment with the argon laser was found to correlate with clinical diagnosis. Nine patients with superficial venular dilatation of the lower limb associated with varicose veins were treated with the argon laser and the results were uniformly poor. However, two patients with the clinically distinct condition of arborizing telangiectasia (or essential progressive telangiectasia) of the legs responded well to treatment. No other satisfactory treatment is available for this cosmetically distressing condition, so that argon laser therapy appears to be the treatment of choice.
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  • 80
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    Keywords: Neodymium-YAG laser ; Meningioma ; Microsurgery ; Micromanipulator
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract The coagulation and tumour-shrinking properties of the Nd-YAG laser make it a useful tool in the treatment of vascular intracranial tumours, in particular meningiomas. The resection of many tumours such as base-of-skull meningiomas inevitably involves limited access, making precision work with the hand-held laser difficult. This paper presents the use of a special micromanipulator which allows coupling of the OPMILas YAG laser to the Zeiss OPMI operating microscope. The laser can be used in focused or defocused mode, with better precision than that obtained in the hand-held position. A built-in filter makes the instrument safe for the surgeon to use without goggles.
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    Lasers in medical science 1 (1986), S. 221-224 
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    Keywords: Lasers ; Exposure time ; Calibration ; Safety
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    Topics: Medicine , Physics , Technology
    Notes: Abstract A hand-held unit has been constructed for routine measurement of exposure times of argon and krypton lasers. A small photodiode is used as the sensing element, and the measured exposure time in ms is observed on a liquid-crystal display. A series of measurements was made on a set of four lasers in use in ophthalmology departments in North Wales. Typically, the measured exposure times were observed to agree well with set values. Percentage errors were, however, often considerable at the shortest exposure settings. A small variation in values of exposure timings for a selected exposure time was found as a function of selected aiming-beam position. This presumably arises out of the design of the particular aiming-beam/shutter assembly. Although no serious shutter malfunction was detected, the ability to measure exposure times accurately was considered relevant to checking the delivered output of laser systems.
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    Lasers in medical science 1 (1986), S. 225-228 
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    Lasers in medical science 1 (1986), S. 229-230 
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    Lasers in medical science 1 (1986), S. 231-231 
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    Lasers in medical science 1 (1986), S. 232-232 
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    Lasers in medical science 1 (1986), S. 139-142 
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    Keywords: Capsulotomy ; Iridotomy ; Photodisruption ; Eye anterior segment ; Neodymium-YAG laser
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract Since the introduction of microsurgery by the neodymium-doped yttrium aluminium garnet (Nd-YAG) laser many conventional surgical procedures for the anterior segment of the eye have been superseded. We discuss the current indications, contraindications, techniques and complications encountered in pulsed Nd-YAG laser surgery of the anterior segment.
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    Keywords: Oesophageal cancer ; Gastric cancer ; Neodymium-YAG laser
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    Notes: Abstract For palliative treatment of tumours with the Nd-YAG laser, the non-contact method of applying laser energy has become established as a useful technique. However, it has certain disadvantages which include overdistension of the intestine, difficulty in calculating the amount of energy applied in each place, and the danger of destruction of the tip of the light guide if this makes contact with the tissue while the laser is being fired. The newly developed contact method of energy application by means of ceramic tips is free from such disadvantages. We report our results with the contact and the non-contact method in the treatment of stenosing inoperable tumours of the oesophagus and stomach. By the end of 1985 we had treated 76 patients with the non-contact method and 16 with the contact method. The relative advantages of the two methods in clinical use are discussed.
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    Lasers in medical science 1 (1986), S. 158-159 
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    Lasers in medical science 1 (1986), S. 147-151 
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    Keywords: Neodymium-YAG laser ; Splenic resection ; Cellular biostimulation ; Mast cells ; Splenic regeneration ; Pigs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Description / Table of Contents: Résumé Splénectomie partielle au laser YAG-Nd. Une série de 11 porcs (18–35 kg) subissent une splénectomie partielle à l'aide d'un laser YAG-Nd (80 W de puissance, 8° de divergence), après ligature de l'artère gastro-épiploique. On obtient une coupe et une hémostase simultanée rapide. La zone d'ischémie est limitée à 1 ou 2 mm d'épaisseur et se trouve rapidement remplacée par du tissue fibreux au 10e jour post-opératoire (J10). Aucune hémorragie secondaire n'est à déplorer. L'examen en microscopie semi-fine et électronique montre: à J 3 une activité macrophagique et polynucléaire intense dans la pulpe rouge à proximité de la coupe; à J 10 de nombreuses mitoses des cellules lymphoides de la pulpe blanche; à J 30 une forte densité de plasmocytes et de mastocytes répartis dans les centres germinaux situés à proximité de la fibrose de bordure. Les contrôles à J 180 et J 365 montrent une guérison totale du foyer de résection et une taille normale de la rate.
    Notes: Abstract Eleven pigs (18–35 kg) were submitted to partial splenic resection with an 8° divergent Nd-YAG laser beam (80 W). The gastroepiploic artery was ligated in 10 pigs. The laser provided both rapid cutting and haemostasis, and the ischaemic layer was limited to 1 or 2 mm in thickness. This was replaced by fibrous tissue by the tenth postoperative day and delayed bleeding was not observed. Semi-thin and electron microscopic examinations of the spleen on the third postoperative day showed intensive macrophage and polynuclear infiltration into the red pulp in the vicinity of the resection. At ten days mitotic figures of lymphoid cells and a few mast cells were present in the white pulp. By day 30 a large concentration of plasmocytes and mast cells were scattered in germinal centres underlying the new fibrotic capsule. Healing, with restoration of the size of the spleen, was found at six months and at twelve months postoperatively.
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  • 90
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    Lasers in medical science 10 (1995), S. 37-42 
    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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  • 91
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    Lasers in medical science 10 (1995), S. 31-36 
    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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  • 92
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    Lasers in medical science 10 (1995), S. 157-163 
    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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  • 93
    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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  • 94
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    Lasers in medical science 10 (1995), S. 93-104 
    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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  • 95
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    Lasers in medical science 10 (1995), S. 13-18 
    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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  • 96
    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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  • 97
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    Lasers in medical science 11 (1996), S. 3-10 
    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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    Lasers in medical science 11 (1996), S. 59-60 
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    Lasers in medical science 11 (1996), S. 53-58 
    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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    Lasers in medical science 11 (1996), S. 79-95 
    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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