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  • Articles  (765)
  • Articles: DFG German National Licenses  (765)
  • Springer  (765)
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  • 1985-1989
  • 1993  (765)
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  • Articles  (765)
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  • 1
    Electronic Resource
    Electronic Resource
    A KBES for integrated engineering (1993)
    Springer
    Engineering with computers 9 (1993), S. 1-16 
    Details
    ISSN: 1435-5663
    Keywords: Blackboard ; Expert systems ; Industrial structures ; Integrated engineering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract The expert process of engineering involves application of knowledge fundamental to the engineering process at one end, and of compiled knowledge in the form of heuristics gained through many years of experience at the other. Developments in Artificial Intelligence have made the process of computer aided engineering richer by enabling the simulation of this human process of engineering, which until now has been difficult to capture. Knowledge Based Expert Systems (KBES) in engineering developed so far have addressed only narrow domains of the entire process of engineering. This paper discusses a KBES shell (IES) that integrates various AI technologies, which makes it possible to implement new problem-solving strategies required for efficient handling of the entire engineering process. Issues in the integrated process of engineering are discussed first, in order to evolve a specification for the shell. The blackboard architecture is shown to be the ideal backbone for such a shell. The details of inference techniques, the knowledge based backtracking mechanism and the DBMS used in the IES are presented. The application of the IES is demonstrated using the domain of integrated engineering of steel industrial structures as an example. This application encompasses the engineering activities of conceptual design, detailed design, documentation and construction planning.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01198249
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  • 2
    Electronic Resource
    Electronic Resource
    Structural synthesis under manufacturability constraints: A CAD system for the design of injection-molded product housings (1993)
    Springer
    Research in engineering design 5 (1993), S. 185-201 
    Details
    ISSN: 1435-6066
    Keywords: Computer-aided design ; Design for manufacture ; Injection molding ; Structural synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract We describe a computer-aided design system that automatically constructs the internal functional surface shapes of plastic injection molded product housings. Fundamental manufacturability constraints related to the geometry of injection mold parting and the solidification of molten plastic are identified. These constraints are embodied in structural synthesis operators that create the internal shapes given a set of functional requirements. An implementation, which is integrated with a system that automatically designs the external visible surface of the housing, is discussed. Algorithms for the structural synthesis operators are provided along with sample output demonstrating their operation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01608362
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  • 3
    Electronic Resource
    Electronic Resource
    A meta-model for mechanical products based upon the mechanical design process (1993)
    Springer
    Research in engineering design 5 (1993), S. 140-160 
    Details
    ISSN: 1435-6066
    Keywords: Design documentation ; Features ; Functional modeling ; Product modeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract This paper describes preliminary work toward the develoment of a framework and a system for modeling the “meta-physical” information of mechanical products. Meta-physical information is that information which describes the nature or reason for existence of objects in the physical product model. Such information includes product and feature functionality, design intent, relations, constraints and viewpoint-dependent definitions. This effort has resulted in an initial model structure and a prototype system. The product model consists of a meta-physical product model with attached physical product models containing, among other information, geometry, dimensions, tolerances, and features. The content and structure of the product model correspond directly to the information used and produced during the mechanical design process. The prototype system integrates a solid modeler, a feature modeler, a dimension and tolerance modeler, and a meta-physical modeler. This paper provides an overview of the meta-model structure, usage and potential.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01608360
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  • 4
    Electronic Resource
    Electronic Resource
    Announcements (1993)
    Springer
    Research in engineering design 5 (1993), S. 238-238 
    Details
    ISSN: 1435-6066
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01608365
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  • 5
    Electronic Resource
    Electronic Resource
    Constraint-based design using an operational approach (1993)
    Springer
    Research in engineering design 5 (1993), S. 202-217 
    Details
    ISSN: 1435-6066
    Keywords: Constraint-based design ; Feature modeling ; Geometric reasoning ; Graph grammar ; Knowledge-based inference
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Constraint-based design, which explicitly represents and operates upon constraints, has been recognized as a promising tool for achieving intelligent support of design, particularly the design of mechanical parts or assemblies. It is essential for a constraint-based system to realize the constraint-solving capability. This paper presents an operational approach to constraint solving using incremental feature operations. The approach is based on an operational interpretation of constraints, i.e. the constraint satisfaction is carried out in terms of operations incrementally. A grammatic formalism is used for operational modeling of constraints. Each graph production within a graph grammar corresponds to an operation or a sequence of operations designated for constraint satisfaction that is related to a rule or a procedure. Therefore, a constraint satisfaction process can be represented by a graph grammar parsing process. The operation sequence is planned by graph grammar parsing and invocation of the related rules or procedures. Constraints are then evaluated by invoking the sequenced operations. Features are introduced as higher-level abstractions into the geometric constraints network. This enables reasoning about design validation from topological and manufacturing views.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01608363
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  • 6
    Electronic Resource
    Electronic Resource
    Announcements (1993)
    Springer
    Research in engineering design 5 (1993), S. 240-240 
    Details
    ISSN: 1435-6066
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01608367
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  • 7
    Electronic Resource
    Electronic Resource
    A design environment for laminated fiber-reinforced thick composite materials (1993)
    Springer
    Engineering with computers 9 (1993), S. 36-48 
    Details
    ISSN: 1435-5663
    Keywords: Composite Materials ; Composites ; Computer-aided design ; Computer integrated manufacturing ; Database ; Design database ; Material property database
    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 research described herein concerns the integration of several components of engineering software using a relational database. More specifically, a conceptual finite element material preprocessing system for laminated fiber-reinforced thick composite materials is studied. In this computer-aided analysis (CAA) system, a materials database is integrated with several software components, including commercially available finite element analysis (FEA) programs and preprocessors, and tools for the design of laminated composite materials. The system focuses on assembling, manipulating and using composite materials data, resulting in the transfer of 2-D and 3-D composite materials property data into a finite element analysis program. The system is life-cycle in nature, supporting a composite through testing, analysis and design. it offers great versatility in its ability to use raw ply data from any source, design layups, and generate laminate properties and FEA materials data files. Despite the fact that such integrated systems are not new in many domains, they have not been successfully introduced to the redlm of composite materials analysis and design. This outcome is due largely to the nature of the materials themselves and the overhead they bring to the development of a successful life-cycle model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01198252
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  • 8
    Electronic Resource
    Electronic Resource
    Computational methods for blending surface approximation (1993)
    Springer
    Engineering with computers 9 (1993), S. 49-62 
    Details
    ISSN: 1435-5663
    Keywords: Approximation ; Data exchange ; Geometric modeling ; NURBS ; Surface blends
    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 Blending surfaces form a smooth transition between two distinct, intersecting surfaces or smoothly join two or more disconnected surfaces and are normally procedural surfaces which are difficult to exchange and to interrogate in a reliable and efficient manner. In this paper, an approximation method for blending surfaces which are curvature continuous to the underlying surfaces with a non-uniform rational B-spline (NURBS) surface is presented. The use of NURBS is important since it facilitates the exchange of geometric information between various computer aided design and manufacturing systems. In the method, linkage curves on the underlying surfaces are approximated to within a specified tolerance and cross-link curves are created using the linkage curves, a directional curve and the parametric partial derivatives of the underlying surfaces. Cross-link curves are lofted to form the blending surface and an adaptive sampling procedure is used to test the blending surface against specified tolerances. Cross-link curves are added, where necessary, and the surface relofted until the continuity conditions are satisfied to within specified tolerances. Examples illustrate the applicability of the method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01198253
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  • 9
    Electronic Resource
    Electronic Resource
    Arbitrary crack representation using solid modeling (1993)
    Springer
    Engineering with computers 9 (1993), S. 63-82 
    Details
    ISSN: 1435-5663
    Keywords: Computational fracture mechanics ; Crack propagation ; Three-dimensional fracture mechanics ; Topological data structure
    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 describes the fundamental modeling approaches adopted for crack nucleation and propagation in a software system that is specifically designed to simulate problems with evolutionary geometry. Only the topological and geometrical aspects of crack modeling, and how these aspects affect the database representation in the system, are addressed in the present discussion. The following are the innovative features of the present crack modeling approach: (a) crack simulation is done with a true geometric representation of the structure, via solid modeling; (b) crack modeling relies on the sophisticated, topology-based data structure of this system to support linkage to the solid model, fast interaction and accurate representation of evolving flaw shapes; (c) the system provides the ability to specify flaws of arbitrary shape (including non-planar flaws), size and orientation at arbitrary locations in the geometric model; (d) the flaw is specified at the desired location in the actual structure geometry, rather than at a location in the mesh; (e) the system uses all its automatic and local remeshing capabilities for the simulation of flaw initiation and growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01199046
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  • 10
    Electronic Resource
    Electronic Resource
    Announcement (1993)
    Springer
    Engineering with computers 9 (1993), S. 124-124 
    Details
    ISSN: 1435-5663
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01199050
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  • 11
    Electronic Resource
    Electronic Resource
    Agent-based framework for integrated facility engineering (1993)
    Springer
    Engineering with computers 9 (1993), S. 94-107 
    Details
    ISSN: 1435-5663
    Keywords: Communications standards ; Integrated design environments ; Software integration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract An agent-based framework for the development of integrated facility engineering environments in support of collaborative design is introduced. This framework aims at integrating design software by allowing better software interoperability. Within their framework, design agents represent various existing design and planning systems that communicate their design information and knowledge partially and incrementally using the Agent Communication Language (ACL). ACL is a formal language proposed as a communication standard for disparate software. It is based on a logic-based language called Knowledge Interchange Format (KIF) and a message protocol called Knowledge Query Manipulation Language (KQML). Design agents are linked and their communication of design information is coordinated via system programs called facilitators in a federation architecture. The federation architecture specifies the way design agents and facilitators communicate in an integrated software environment. In concert with pursuing fundamental research concepts, we have been developing an integrated design software environment that spans different phases of the facility life cycle. This environment serves to demonstrate the primary aspects of this research methodology. In this paper, we first discuss the integration problem and review related research projects. We then present the major aspects of agent-based software engineering methodology and its application to integrated facility engineering. A highlight of the current integrated design environment development is given to illustrate the advantages of this approach. Finally, we summarize and discuss some of the important research issues in light of previous research.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01199048
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  • 12
    Electronic Resource
    Electronic Resource
    An Object-Logic model for the representation and processing of design standards (1993)
    Springer
    Engineering with computers 9 (1993), S. 133-159 
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    ISSN: 1435-5663
    Keywords: Conformance checking ; Design standards ; Object-logic model ; Representation
    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 There are two distinct categories of knowledge in a design standard: (1) knowledge of the organization of design objects and (2) knowledge of the methods used in reasoning about the design objects. The object-oriented paradigm lends itself naturally to representing the organizational aspect of the design standard. The logic programming paradigm, on the other hand, is well suited to implementing the reasoning mechanisms for design and conformance checking. The object-oriented and logic programming paradigms are combined to provide a unified Object-Logic model for the representation of design codes and the processing of design standards. By storing the design provisions in a knowledge base, the model is capable of performing conformance checking and component design. To evaluate the feasibility and practicality of this model, a prototype system, HyperLRFD++, has been implemented for parts of the American Institute of Steel Construction (AISC) Load and Resistance Factor Design (LRFD) specification and tested on sample problems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01206345
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  • 13
    Electronic Resource
    Electronic Resource
    Development of the object-oriented finite element modeling system — MODIFY (1993)
    Springer
    Engineering with computers 9 (1993), S. 187-197 
    Details
    ISSN: 1435-5663
    Keywords: CAD ; FEM ; Mesh generation ; Modeling ; Object-Oriented programming
    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 present a new concept of FE modeling, based on the object-oriented principle, and develop the prototype program MODIFY (MODeling tool for Integrated Finite element analYsis). MODIFY has three novel features: (1) FE modeling by the part object concept, (2) a fully object-oriented data structure, and (3) a part-by-part fully automated mesh subdivision. When using MODIFY it is necessary to define and assemble part objects, which consist of geometry objects, analytical condition objects and relation objects, to describe the continuity between adjacent part objects. MODIFY automatically generates an appropriate FE model for each geometry object, satisfying continuity conditions with adjacent parts by referring to relation objects. If some part of the model is to be modified, the user needs only to change the corresponding part objects. Because of the object-oriented data structure, MODIFY also has a powerful capability for adaptive meshing. The existing version of MODIFY is applicable to FE models for3-D shell structures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01201899
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  • 14
    Electronic Resource
    Electronic Resource
    Low-degree approximation of high-degree B-spline surfaces (1993)
    Springer
    Engineering with computers 9 (1993), S. 198-209 
    Details
    ISSN: 1435-5663
    Keywords: Data exchange ; Surface approximation
    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, a method for approximate conversion of high degree Bezier and B-spline surfaces to lower degree representations is presented to facilitate the exchange of surface geometry between different geometric modeling systems. Building on previous work on curve approximation, the method uses adaptive sampling to compute approximation error and lofting of isoparametric curves to produce the approximating surface. In addition, a bound for the approximation accuracy is computed using convex hulls.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01201900
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  • 15
    Electronic Resource
    Electronic Resource
    An integrated NMT-based CAE environment — Part I: Boundary-based feature modeling utility (1993)
    Springer
    Engineering with computers 9 (1993), S. 210-219 
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    ISSN: 1435-5663
    Keywords: Features ; Geometry-Based reasoning ; Geometry modeling utility ; Non-Manifold 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 The integration of CAD, CAM and CAE is far from a commercial reality. Feature technology has been identified as a key element in bridging many of the integration gaps. This two-part paper emphasizes an integrated NMT-based environment that serves the needs of both geometry and feature-based applications. Part I describes a feature modeling utility that coexists with commercial CAD systems by providing external feature-based functionality and making it available to application programs. A non-manifold topologybased system, called TAGUS, is used to represent the model geometry and provide the foundation for features representation. The architecture of a feature-based analysis system is described and, finally, the automated design of the feed system for injection molds is presented as an example to illustrate the application of the feature modeling utility. A detailed description of this application is the focus of the companion paper (Part II).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01201901
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  • 16
    Electronic Resource
    Electronic Resource
    Computation of stationary points of distance functions (1993)
    Springer
    Engineering with computers 9 (1993), S. 231-246 
    Details
    ISSN: 1435-5663
    Keywords: CAD ; CAGD ; CAM ; interrogation ; geometric modeling ; solid modeling ; intersection ; distance computation ; symmetry transforms ; robotics
    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 an algorithm for computation of the stationary points of the squared distance functions between two point sets. One point set consists of a single space point, a rational B-spline curve, or a rational B-spline surface. The problem is reformulated in terms of solution of n polynomial equations with n variables expressed in the tensor product Bernstein basis. The solution method is based on subdivision relying on the convex hull property of the n-dimensional Bernstein basis and minimization techniques. We also cover classification of the stationary points of these distance functions, and include a method for tracing curves of stationary points in case the solution set is not zerodimensional. The distance computation problem is shown to be equivalent to the geometrically intuitive problem of computing collinear normal points. Finally, examples illustrate the applicability of the method
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01201903
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  • 17
    Electronic Resource
    Electronic Resource
    Robustness for time-varying systems (1993)
    Springer
    Mathematics of control, signals, and systems 6 (1993), S. 247-263 
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    ISSN: 1435-568X
    Keywords: Robustness ; Time-varying ; Coprime factorizations ; Operator balls ; Linear systems ; Stabilization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics , Technology
    Notes: Abstract We consider robust optimization for time-varying systems in terms of perturbations of fractional representations. Upper and lower bounds are given for the maximal radius of the operator ball around a given plant which can be stabilized by a single compensator. In the time-invariant case, these numbers are equal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01211622
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  • 18
    Electronic Resource
    Electronic Resource
    On the minimal number of trajectories determining a multidimensional system (1993)
    Springer
    Mathematics of control, signals, and systems 6 (1993), S. 264-288 
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    ISSN: 1435-568X
    Keywords: Multidimensional system ; System behavior ; Trajectory ; Exact modeling ; Inverse system ; Gröbner basis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics , Technology
    Notes: Abstract The minimal numberμ(S) of generators of a multidimensional systemS is constructively determined. Such anS is the solution space of a linear system of partial differential or difference equations with constant coefficients. The main theorem generalizes recent results of Heij and Zampieri who calculated the numberμ(S) in the one- (resp. two-) dimensional discrete case. There is also a direct connection with Macaulay's inverse systems in the multidimensional discrete situation, in particular with his principal systems characterized by the relationμ(S)⩽1. It is surprising that, for dimensions greater than one, very many “large” systems are principal in this sense.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01211623
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  • 19
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    On asymptotic model matching (1993)
    Springer
    Mathematics of control, signals, and systems 6 (1993), S. 322-340 
    Details
    ISSN: 1435-568X
    Keywords: Model matching ; Model reference adaptive control ; Nonlinear time-varying controllers ; Causality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics , Technology
    Notes: Abstract In this paper we consider the problem of asymptotic model matching, in which the objective is to force the plant to behave asymptotically like a reference model in response to an exogenous input. Conditions for solvability via a linear time-invariant controller are well known; here we prove that under a closed-loop causality constraint, moving to a nonlinear time-varying controller affords no reduction of these conditions. We explore the ramifications of this result to the (ideal) model reference adaptive control problem, demonstrating that (i) an upper bound on the plant relative degreemust be known, and (ii) the plant zeros in the closed right half-planemust lie in a finite set. We also derive a bound on the achievable asymptotic performance in the event that the solvability conditions fail to hold.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01211500
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  • 20
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    Differential periodic Riccati equations: Existence and uniqueness of nonnegative definite solutions (1993)
    Springer
    Mathematics of control, signals, and systems 6 (1993), S. 341-362 
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    ISSN: 1435-568X
    Keywords: Differential periodic Riccati equation ; Periodic nonnegative definite solutions ; Hamiltonian matrix method ; Special solutions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics , Technology
    Notes: Abstract In this paper we consider the differential periodic Riccati equation. All the periodic nonnegative definite solutions are characterized in the more general case, providing a method for constructing them. The method is obtained from the study of the invariant subspaces of the monodromy matrix of the associated Hamiltonian system, and from the relations between these invariant subspaces and the controllability and unobservability subspaces. Finally, the method is applied to obtain necessary and sufficient conditions for the existence of any periodic nonnegative definite solution and to study the existence and uniqueness of minimal, maximal, stabilizing, and strong solutions.
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    URL: http://dx.doi.org/10.1007/BF01211501
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  • 21
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    Reduced inverse for controlled systems (1993)
    Springer
    Mathematics of control, signals, and systems 6 (1993), S. 363-379 
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    ISSN: 1435-568X
    Keywords: Nonlinear systems ; Inversion ; Left-inverse system ; Observability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics , Technology
    Notes: Abstract The left-invertibility and the general construction of reduced inverse systems are studied and described in a unified vector-space approach for both linear and nonlinear systems. The order of reduced inverse systems is calculated by means of intrinsic invariants, which reflect some properties related to observability. The uniqueness of the reduced inverse is described by a factor space.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01211502
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  • 22
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    Nippondenso Co. Ltd: A case study of strategic product design (1993)
    Springer
    Research in engineering design 5 (1993), S. 1-20 
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    ISSN: 1435-6066
    Keywords: Product design ; Assembly automation ; Concurrent engineering ; Japanese manufacturing methods
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Nippondenso Co. Ltd (NDCL) is Japan's foremost manufacturer of automotive components. Over the past twenty-five years it has developed a variety of approaches to automating the assembly of products in order to meet the high-variety, just-in-time production requirements of its customers, notably Toyota. The approach evolved by NDCL is to design the product intelligently and to make massive use of the simplest automation technology possible consistent with the technical challenges of the product and its production strategy. The result is the capability to manufacture products with considerable model mix at high volume, with little or no changeover time between models. This is essentially a technological response to a business environment challenge. In pursuit of this strategy, NDCL has categorized the problems of assembly automation into distinct classes, identified applicable solutions for each class, and successively attacked and solved increasingly difficult problems. This paper describes this strategy, gives examples of its evolution, and indicates how NDCL has managed production technology, notably robots, as part of the overall attack. NDCL's approaches to concurrent engineering (CE) and new product risk management are also described. The paper is based both on seven personal visits to NDCL during the period 1974 to 1991, which included extensive interviews with NDCL engineers and managers and plant tours, and on papers published by NDCL and interviews with their authors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01608394
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  • 23
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    Conference announcements (1993)
    Springer
    Research in engineering design 5 (1993), S. 120-120 
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    ISSN: 1435-6066
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02032581
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  • 24
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    A framework for performance-based design (1993)
    Springer
    Research in engineering design 5 (1993), S. 105-118 
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    ISSN: 1435-6066
    Keywords: Axiomatic design ; Building design ; Decision-making ; Systems integration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract The international competitiveness of the US construction industry is linked to its strategic ability to design and build quality projects. This means delivering facilities that satisfy all the needs of the client. Correct decision-making during design and construction planning is the best means for assuring a quality project. Performance-based design is a framework that enables the project team to approach the project delivery process systematically and provides basic principles for evaluating and comparing alternative solutions. The principles of axiomatic design (as previously advanced by Suh) and the concept of an interface index are key elements of the framework. Axiomatic design provides an operational structure for the design process as well as a set of basic principles or axioms for guiding each decision-maker. The interface index complements the design axioms by quantifying the effort associated with integrating the contributions of multiple decision-makers into a total system. Elements of the framework are demonstrated through application to an actual facility.
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    Special issue: Advances in representation and reasoning for mechanical CAD (1993)
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    Research in engineering design 5 (1993), S. 123-124 
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    ISSN: 1435-6066
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
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    A serial version of the Pohlig-Hellman Algorithm for computing discrete logarithms (1993)
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    Applicable algebra in engineering, communication and computing 4 (1993), S. 77-80 
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    ISSN: 1432-0622
    Keywords: Cyclic group ; Discrete logarithm ; Mixed radix representation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics , Technology
    Notes: Abstract We describe a method for computing discrete logarithms in any nonsimple cyclic group, which may be considered as a serial version of the Pohlig-Hellman Algorithm. The complexity is the same as that of the P-H Algorithm, but does not need the Chinese Remainder Theorem.
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    On a signal processing algorithms based class of linear codes (1993)
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    Applicable algebra in engineering, communication and computing 4 (1993), S. 41-57 
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    ISSN: 1432-0622
    Keywords: Bilinear forms ; Aperiodic convolutions ; Computational complexity ; Algebraic coding theory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics , Technology
    Notes: Abstract In this work, the correspondence between linear (n,k,d) codes and aperiodic convolution algorithms for computing a systemφ ofk bilinear forms over GF(pm) is explored. A number of properties are established for the linear codes that can be obtained from a computational procedure of this type. A particular bilinear form is considered and a class of linear codes over GF(2m) is derived with varyingk andd parameters. The code lengthn is equal to the multiplicative complexity of the computation of an aperiodic convolution and an efficient computation thereof leads to the shortest codes possible using this approach, many of which are optimal or near-optimal. A new decoding procedure for this class of linear codes is presented which exploits the block structure of the generator matrix of the codes. Several interesting observations are made on the nature of the codes obtained as a result of such computations. Such a computation of bilinear forms can be generalized to include other bilinear forms and the related classes of codes.
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    Structural properties and enumeration of quasi cyclic codes (1993)
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    Applicable algebra in engineering, communication and computing 4 (1993), S. 25-39 
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    ISSN: 1432-0622
    Keywords: Quasi cyclic block codes ; Structural properties ; Enumeration ; Algebraic dual characterisation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics , Technology
    Notes: Abstract Given any finite fieldF q , an (N, K) quasi cyclic code is defined as aK dimensional linear subspace ofF q N which is invariant underT n for some integern, 0 〈n ≦N, and whereT is the cyclic shift operator. Quasi cyclic codes are shown to be isomorphic to theF q [λ]-submodules ofF q N where the productμ(gl)·ν is naturally defined asμ 0 ν+μ 1νT n +...+μ m νT mn ifμ(λ)= μ 0 +μ 1 +...+μ m λ m .In the case where (N/n, q)=1, all quasi cyclic codes are shown to be decomposable into the direct sum of a fixed number of indecomposable components called irreducible cyclicF q [λ]-submodules providing for the complete characterisation and enumeration of some subclasses of quasi cyclic codes including the cyclic codes, the quasi cyclic codes with a cyclic basis, the maximal and the irreducible ones. Finally a general procedure is presented which allows for the determination and characterisation of the dual of any quasi cyclic code.
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    Cryptanalysis of Rédei- and Dickson permutations on arbitrary finite rings (1993)
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    Applicable algebra in engineering, communication and computing 4 (1993), S. 59-76 
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    ISSN: 1432-0622
    Keywords: Cryptography ; Public-key cryptosystem ; RSA ; Rational permutation ; Dickson polynomial ; Rédei function ; Fixedpoint ; Minimal and maximal cyclelength
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics , Technology
    Notes: Abstract In the RSA public-key cryptosystem the encryption function is a permutation on the residue class ringℤ/Nℤ induced by some polynomialX k ∈(ℤ/Nℤ) [X], whereN is the product of two large primes. Variants of the RSA-scheme can be obtained, if this permutation is replaced by different types of rational permutations onℤ/Nℤ. A more general approach is the use of arbitrary finite rings instead of residue class rings in cryptography. Since the message space is finite, in either case cryptanalysis can be effected by superenciphering. A serious weakness of those PKCs is the existence of a large number of fixedpoints. But even if there are only few fixedpoints in the message space, the elements of considerable small cyclelength are much inconvenient. Anyway an analysis of the minimal cyclelength, i.e. the minimum of cyclelengths of elements different from fixedpoints, is necessary. In this paper such an analysis will be carried out in the case of Rédei- and Dickson permutations on arbitrary finite rings. The results obtained provide a good basis to construct secure PKCs with best protection against superenciphering. Some of the problems and results in the special cases of finite fields and residue class rings have been stated earlier in the literature (see references).
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    A new efficient factorization algorithm for polynomials over small finite fields (1993)
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    Applicable algebra in engineering, communication and computing 4 (1993), S. 81-87 
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    ISSN: 1432-0622
    Keywords: Factorization of polynomials over finite fields ; Differential equations over rational function fields
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics , Technology
    Notes: Abstract We present a new deterministic factorization algorithm for polynomials over a finite prime fieldF p . As in other factorization algorithms for polynomials over finite fields such as the Berlekamp algorithm, the key step is the “linearization” of the factorization problem, i.e., the reduction of the problem to a system of linear equations. The theoretical justification for our algorithm is based on a study of the differential equationy (p −1)+y p =0 of orderp−1 in the rational function fieldF p(x). In the casep=2 the new algorithm is more efficient than the Berlekamp algorithm since there is no set-up cost for the coefficient matrix of the system of linear equations.
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    Almost perfect binary functions (1993)
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    Applicable algebra in engineering, communication and computing 4 (1993), S. 95-102 
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    ISSN: 1432-0622
    Keywords: Correlation ; Sequences ; Fourier transform
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics , Technology
    Notes: Abstract The almost perfect binary sequences have been defined in [6] as (−1, +1)-periodic sequences such that all their out-of-phase autocorrelation coefficients are zero except one. In the preceding paper, the study of the almost perfect binary sequences is done by means of the ringF 2[X]/(X n −1). Here, the arithmetic of cyclotomic fields enables us to solve open problems and questions like: structure and existence of these sequences.
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    Explicit factorization of $$x^{2^k }$$ + 1 overF p with primep≡3 mod 4 (1993)
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    Applicable algebra in engineering, communication and computing 4 (1993), S. 89-94 
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    ISSN: 1432-0622
    Keywords: Finite field ; Irreducible polynomial ; Primitive root of unity ; Fast Fourier Transform (FFT)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics , Technology
    Notes: Abstract In this note we give a complete explicit factorization of $$x^{2^k }$$ + 1 into irreducible polynomials overF p for a primep≡3 mod 4. As a result we can construct an irreducible polynomial overF p of degree of any power of 2. Some interesting properties of the coefficients of the irreducibles are noted. We also mention that our results may be useful in applying the Fast Fourier Transform over finite fields.
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    Gröbner bases of ideals defined by functionals with an application to ideals of projective points (1993)
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    Applicable algebra in engineering, communication and computing 4 (1993), S. 103-145 
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    ISSN: 1432-0622
    Keywords: Gröbner bases ; Polynomial ideals ; Dual bases ; Interpolation ; 0-dimensional schemes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics , Technology
    Notes: Abstract In this paper we study 0-dimensional polynomial ideals defined by a dual basis, i.e. as the set of polynomials which are in the kernel of a set of linear morphisms from the polynomial ring to the base field. For such ideals, we give polynomial complexity algorithms to compute a Gröbner basis, generalizing the Buchberger-Möller algorithm for computing a basis of an ideal vanishing at a set of points and the FGLM basis conversion algorithm. As an application to Algebraic Geometry, we show how to compute in polynomial time a minimal basis of an ideal of projective points.
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    Standard bases, critical tropisms and flatness (1993)
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    Applicable algebra in engineering, communication and computing 4 (1993), S. 197-215 
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    Keywords: Hironaka's division ; Standard bases ; Newton's polygon ; Critical tropisms ; Generic flatness
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract Using the standard basis notion, we adapt to the affine algebraic geometry the notion of the critical tropisms of Lejeune-Teissier and we give some effective criteria for testing geometrical properties for the generic projectionX=SpecK[t1,...,tm][x1,...,xn]/I ↦ y=SpecK[t1,...,tm].
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    An algorithm for computing a companion block diagonal form for a system of linear differential equations (1993)
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    Applicable algebra in engineering, communication and computing 4 (1993), S. 185-195 
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    ISSN: 1432-0622
    Keywords: Linear system of differential equations ; Cyclic vectors
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract In this paper we describe a new algorithm which reduces in a finite number of steps a linear system of differential equations to a companion block diagonal form. This form is particularly convenient if one wishes to compute invariants at singularities.
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    On decomposing systems of polynomial equations with finitely many solutions (1993)
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    Applicable algebra in engineering, communication and computing 4 (1993), S. 217-230 
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    ISSN: 1432-0622
    Keywords: Algebraic variety decomposition ; Gröbner bases ; Systems of nonlinear equations
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract This paper deals with systems ofm polynomial equations inn unknown, which have only finitely many solutions. A method is presented which decomposes the solution set into finitely many subsets, each of them given by a system of type $$f_1 \left( {x_1 } \right) = 0,f_2 \left( {x_1 ,x_2 } \right) = 0, \ldots ,f_n \left( {x_1 , \ldots ,x_n } \right) = 0$$ . The main tools for the decomposition are from ideal theory and use symbolical manipulations. For the ideal generated by the polynomials which describe the solution set, a lexicographical Gröbner basis is required. A particular element of this basis allows the decomposition of the solution set. By a recursive application of these decomposition techniques the triangular subsystems are finally obtained. The algorithm gives even for non-finite solution sets often also usable decompositions.
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    Lower bounds for arithmetic networks (1993)
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    Applicable algebra in engineering, communication and computing 4 (1993), S. 1-24 
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    ISSN: 1432-0622
    Keywords: Parallel complexity ; Algebraic complexity theory ; Arithmetic networks ; Constructible and semialgebraic sets ; Degree and connected components
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics , Technology
    Notes: Abstract We show lower bounds for depth of arithmetic networks over algebraically closed fields, real closed fields and the field of the rationals. The parameters used are either the degree or the number of connected components. These lower bounds allow us to show the inefficiency of arithmetic networks to parallelize several natural problems. For instance, we show a √n lower bound for parallel time of the Knapsack problem over the reals and also that the computation of the “integer part” is not well parallelizable by arithmetic networks. Over the rationals we obtain results of similar order and that the Knapsack has an √n lower bound for the parallel time measured by networks. A simply exponential lower bound for the parallel time of quantifier elimination is also shown. Finally, separations among classesP K andNC K are available for fieldsK in the above cases.
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    Conditional narrowing modulo a set of equations (1993)
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    Applicable algebra in engineering, communication and computing 4 (1993), S. 147-168 
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    Keywords: Conditional rewriting ; Conditional narrowing ; E-unification ; Constraint logic and functional programming
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract Narrowing is a universal unification procedure for equational theories given by a canonical term rewrite system. In this paper we introduce conditional narrowing modulo a set of conditional equations and give a full proof of its correctness and completeness for equational conditional rewrite systemsR, E without extravariables whereE is regular andR, E is Church-Rosser moduloE and decreasing moduloE. This result can be seen as the theoretical foundation of a special form of constraint logic and functional programming.
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    Symbolic homotopy construction (1993)
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    Applicable algebra in engineering, communication and computing 4 (1993), S. 169-183 
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    ISSN: 1432-0622
    Keywords: Bézout number ; BKK bound ; Homotopy continuation
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    Notes: Abstract The classical Theorem of Bézout yields an upper bound for the number of finite solutions to a given polynomial system, but is very often too large to be useful for the construction of a start system, for the solution of a polynomial system by means of homotopy continuation. The BKK bound gives a much lower upper bound for the number of solutions, but unfortunately, constructing a start system based on this bound seems as hard as solving the original given polynomial system. This paper presents a way for computing an upper bound together with the construction of a start system. The first computation is performed symbolically. Due to this symbolic computation, the constructed start system can be solved numerically more efficiently. The paper generalizes current approaches for homotopy construction towards the BKK bound.
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    The virtues of laziness: Complexity of the Tangent Cone Algorithm (1993)
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    Applicable algebra in engineering, communication and computing 4 (1993), S. 231-238 
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    ISSN: 1432-0622
    Keywords: Computational algebra ; Tangent cone ; Standard bases ; Algebraic complexity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics , Technology
    Notes: Abstract The Tangent Cone Algorithm is a variant of Buchberger Algorithm, to compute standard bases with respect to orderings which are not well-orderings, which is useful in computational local algebra. We show here that its complexity is the same as the one of Buchberger Algorithm.
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    Finding irreducible and primitive polynomials (1993)
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    Applicable algebra in engineering, communication and computing 4 (1993), S. 263-268 
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    Keywords: Algorithms in finite fields ; polynomials over finite fields
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    Notes: Abstract In the paper some new fast constructions of irreducible and primitive polynomials are presented. For instance, it is shown, that for anyQ large enough one can design a finite field $$\mathbb{F}$$ q withq=Q + o(Q) elements in polynomial time (log Q) o (1).
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    Rank formulas for certain products of matrices (1993)
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    Applicable algebra in engineering, communication and computing 4 (1993), S. 253-261 
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    Keywords: Communication complexity ; Sum-type functions ; Exponential rank quasi direct sum ; Quasi outer product ; Missing dimension
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract For two matrix operations, calledquasi-direct sum andquasi-outer product, we determine their deviations from multiplicative behaviour of the rank. The second operation arises in the determination of the function table for so-called sum-type functions such as the Hamming distance. A consequence of the corresponding rank formula is, that the frequently used log rank can be a very poor bound for two-way communication complexity. Instead, as was shown in [9], a certainexponential rank gives often excellent or even optimal bounds.
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    Construction of roadmaps in semi-algebraic sets (1993)
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    Applicable algebra in engineering, communication and computing 4 (1993), S. 239-252 
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    ISSN: 1432-0622
    Keywords: Roadmaps ; Semi-algebraic sets ; Critical values ; Connected components
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract In this paper we describe an algorithm of construction of a roadmap for a compact semi-algebraic setS ⊂ Rn, which is similar to the algorithm of [3], but which is simpler in the sense that it does not need the use of Whitney stratifications, and more general because it accepts as input any compact semi-algebraic set. The complexity of this algorithm is measured in terms of the numberk of polynomials definingS, their maximum degreed, and the number of variablesn. With respect to those measures, our algorithm runs in time $$\left( {kd} \right)^{O\left( {n^3 } \right)} $$ . The goal of this paper is not a strengthening of the previous results (similar bounds of complexity are obtained in [5] and [13], even for a non-compact set), but more a new approach, and we hope the efficiency of the algorithm.
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    Discovery of invariant equalities in programs over data fields (1993)
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    Applicable algebra in engineering, communication and computing 4 (1993), S. 269-286 
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    Keywords: Program ; Program analysis ; Invariant equality ; Polynomial ; Polynomial ideal
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    Notes: Abstract The problem of the automatic discovery of invariant polynomial equalities in program control points is considered. The class of programs with data algebras that are infinite fields is studied in the paper. The results obtained here may also be extended to infinite commutative integral domains. To solve the problem the approximation method is proposed. Four main problems connected with this method are formulated and proved to be decidable.
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    Nonequilibrium radiation from the CO2 band (1 B 2 —X 1σ g /+ ) in shock-heated flows (1993)
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    Shock waves 3 (1993), S. 11-17 
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    Keywords: Chemical shock tube ; Supersonic jet ; Dissociation ; Recombination ; Distribution function ; Optically active state
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics , Technology
    Notes: Abstract The processes of population and decay of the optically active state CO2(1 B 2) behind shock waves and in supersonic jets are investigated. It is shown that the vibrational distribution function of the electronically excited state1 B 2 is determined by the full energy of the colliding particles CO and O and, at temperatures above 3000 K, the branch of dissociation with the electronically excited O(1 D) atoms is essential.
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    Investigation of a hypersonic crossing shock wave/turbulent boundary layer interaction (1993)
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    Shock waves 3 (1993), S. 35-48 
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    Keywords: Crossing shock ; Turbulent boundary layer ; Interaction
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    Notes: Abstract A combined theoretical and experimental study is presented for the interaction between crossing shock waves generated by (10°, 10°) sharp fins and a flat plate turbulent boundary layer at Mach 8.3. The theoretical model is the full 3-D mean compressible Reynolds-averaged Navier-Stokes RANS) equations incorporating the algebraic turbulent eddy viscosity model of Baldwin and Lomax. A grid refinement study indicated that adequate resolution of the flowfield has been achieved. Computed results agree well with experiment for surface pressure and surface flow patterns and for pitot pressure and yaw angle profiles in the flowfield. The computations, however, significantly overpredict surface heat transfer. Analysis of the computed flowfield results indicates the formation of complex streamline and wave structures within the interaction region.
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    “Thermal layer” effect in MHD: Interaction of a parallel shock with a layer of decreased density (1993)
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    Shock waves 3 (1993), S. 73-78 
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    ISSN: 1432-2153
    Keywords: Computer simulation ; MHD ; “Thermal layer” effect
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract Interaction of a parallel fast MHD shock with a layer of decreased density is discussed using ideal MHD approach. This is an extrapolation of gas dynamic “thermal layer” effect on ideal MHD. Computer simulations show that a magnetic field of a moderate intensity (β ∼ 1) may change the character of the flow for intermediate Mach numbers (M ≤ 5) and a new “raking” regime may occur which is not observed in the absence of a magnetic field. Self similar precursor analogous to that in gas dynamics may develop in the case of highM and low density in the layer but magnetic forces essentially decrease its growth rate. This problem appears in connection with cosmical shock propagation where planetary magnetic tails play the role of the “thermal layer”, and it may also be observed in the laboratory when the shock is strong enough to heat the walls ahead of it.
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    Pressure measurements in chemically reacting powder mixtures with the Bauer piezoelectric polymer gauge (1993)
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    Shock waves 3 (1993), S. 79-82 
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    ISSN: 1432-2153
    Keywords: Piezoelectric polymer ; Porous solids ; Powders ; Pressure measurements ; PVDF gauge ; 5Ti+3Si ; Ni+Al ; TiO2
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics , Technology
    Notes: Abstract The response of highly porous powder compacts and powder mixtures to high pressure shock compression loading is of considerable interest for synthesis and processing of metals, ceramics and superhard materials. This technical note reports the first successful use of the Bauer piezoelectric polymer stress-rate gauge for measurements of shock wave velocity and stress-wave profiles in porous powder compacts. A powder mixture of 5Ti+3Si shows strong chemical reaction at a pressure of 2.5 GPa, while a powder mixture of 3Ni+Al shows no evidence for reaction at 4.7 GPa. A measurement of compaction of a powder compact of rutile at 5.5 GPa shows that it is not compacted to the solid density state. Although pressure increases due to chemical reaction products in condensed phases are modest and difficult to detect, shock wave velocities provide a sensitive measure of the existence of chemical reaction. The increase in shock speed can be described in terms of constant pressure processes which are descriptive of “ballotechnic” reactions, i.e. shock-induced reactions in heterogeneous material mixtures.
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    DSMC approach to nonstationary Mach reflection of strong incoming shock waves using a smoothing technique (1993)
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    Shock waves 3 (1993), S. 67-72 
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    ISSN: 1432-2153
    Keywords: Rarefied gas dynamics ; Mach reflection ; DSMC method ; Smoothing technique
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics , Technology
    Notes: Abstract The direct simulation Monte Carlo (DSMC) method is applied to simulation of nonstationary Mach reflection of strong shock waves. Normally the DSMC method is very time consuming in solving unsteady flow field problems especially for high Mach numbers, because of the necessity of iterative calculations to eliminate the inherent statistical fluctuation caused by a finite sample size. A central weighted smoothing technique is introduced to process the DSMC results, so that the iteration time can be significantly reduced. In spite of some relaxations of the shock wave structure, the smoothing technique is verified to be useful to estima te the flow fields qualitatively and even quantitatively by using a relatively small sample size. The comparison between the present approach and the kineticmodel approach (Xu et al. 1991a, 1991b) on the application to unsteady rarefied flow fields was also carried out.
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    Jump conditions across strong compaction waves in gas saturated rigid porous media (1993)
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    Shock waves 3 (1993), S. 105-111 
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    ISSN: 1432-2153
    Keywords: Porous media ; Shock compaction
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract Based on experimental results and some additional simplifying assumptions, the general macroscopic two phase equations governing the flow field which is developed in a gas saturated rigid porous medium domain were simplified to a form which enab led us to develop two analytical models for calculating the jump conditions across strong compaction waves. Predictions obtained by these two simplified analytical models are compared to the experimental results of Sandusky and Liddiard (1985) and to predictions of another more complicated model which was proposed by Powers et al. (1989). Fairly good to excelle nt agreements are evident.
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    Vibrational temperature measurements in a shock layer using laser induced predissociation fluorescence (1993)
    Springer
    Shock waves 3 (1993), S. 141-148 
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    ISSN: 1432-2153
    Keywords: Laser induced predissociation fluorescence ; Shock layer ; Vibrational temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics , Technology
    Notes: Abstract Single shot spatially and spectrally resolved laser induced predissociation fluorescence measurements in a shock layer around a cylinder in a pulsed supersonic free stream are presented. Fluoresence signals were produced using the tuned output of an argon fluoride excimer laser to excite a mixture of rovibrational transitions in molecular oxygen. The signals produced along a line inside the shock layer were focussed onto a two dimensional detector coupled to a spectrometer, thus allowing spectral and spatial resolution of the fluoresence. In this way, it was possible to detect two fluoresence signals from two different transitions simultaneously, allowing the determination of vibrational temperatures without the need for calibration. To minimize problems associated with low signal to noise ratios, background subtraction and spatial averaging was required.
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    On the compression process in a free-piston shock-tunnel (1993)
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    Shock waves 3 (1993), S. 19-23 
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    ISSN: 1432-2153
    Keywords: Compression process ; Free-piston shock-tunnel ; Hypersonic facility ; Diaphragm rupture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics , Technology
    Notes: Abstract Preliminary results in the Marseille free-piston shock-tunnel facility are presented. The compression of the driver gas by the piston is studied experimentally for two different geometries of the end of the compression tube. Peak pressures obtained with the end of the compression tube closed, and with bursting of the diaphragm separating the high pressure from the low pressure chamber, are compared with calculated values in the cases of N2 and He as driver gases. A phenomenon of accoustic resonance has been uncovered, generating strong pressure oscillations which, if not properly dealt with, could impair the quality of the useful flow in such a facility.
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    Absolute intensity measurements of impurity emissions in a shock tunnel and their consequences for laser-induced fluorescence experiments (1993)
    Springer
    Shock waves 3 (1993), S. 49-53 
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    ISSN: 1432-2153
    Keywords: Laser-induced predissociation fluorescence ; Shock tunnel impurities ; Absolute intensity measurements
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics , Technology
    Notes: Abstract Absolute intensity measurements of impurity emissions in a shock tunnel nozzle flow are presented. The impurity emission intensities were measured with a photomultiplier and optical multichannel analyser and calibrated against an intensity standard. The various metallic contaminants were identified and their intensities measured in the spectral regions 290 to 330 nm and 375 to 385 nm. A comparison with calculated fluorescence intensities for predissociated laser-induced fluorescence signals is made. It is found that the emission background is negligible for most fluorescence experiments.
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    Normal shock wave oscillations in supersonic diffusers (1993)
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    Shock waves 3 (1993), S. 25-33 
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    ISSN: 1432-2153
    Keywords: Compressible flow ; Fluctuation ; Interaction ; Shock oscillation ; Supersonic diffuser
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics , Technology
    Notes: Abstract The present paper describes experimental investigations for shock oscillations caused by normal shock wave/turbulent boundary layer interaction in a supersonic diffuser. An array of wall-mounted transducers and especially a line image sensor for the nonintrusive detection of shock displacements were employed to investigate the interactions at low supersonic speeds. The line image sensor was collimated with a conventional schlieren optical system and was a good indicative of capturing the shock oscillating motions in the present configuration. This study shows that the amplitude of the shock motions increases with approaching flow Mach number, and the cause of oscillation of the shock wave can, however, be independent of the Mach number. In addition, the present system employed to determine the shock wave positions and displacements can be effectively applied to a variety of practical problems.
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    Numerical modelling of shocks in solids with elastic-plastic conditions (1993)
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    Shock waves 3 (1993), S. 55-66 
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    ISSN: 1432-2153
    Keywords: Numerical simulation ; Flux-corrected transport ; Shock in solids ; Elastic-plastic conditions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics , Technology
    Notes: Abstract Results are presented for a range of one- and two-dimensional shock-wave problems in elastic-plastic and hydrodynamic metals. These problems were solved numerically using the Flux-Corrected Transport (FCT) technique which achieves high resolution without non-physical oscillations, especially at shock fronts, and has not been used before in elastic-plastic solids. The two-dimensional problems were solved using both operator- and non-operator-split techniques to highlight the significant differences between these techniques when solving shock-wave problems in elastic-plastic solids. Comparisons of the elastic-plastic solutions with the hydrodynamic solutions are made and illustrate the importance of including elastic-plastic conditions when modelling the behaviour of solids. Also, the errors in these solutions that are due to the initial conditions are discussed in detail.
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    Propagation of blast waves with exponential heat release and internal heat conduction and thermal radiation (1993)
    Springer
    Shock waves 3 (1993), S. 95-104 
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    ISSN: 1432-2153
    Keywords: Chapman-Jouguet detonation ; Explosion ; Heat conduction ; Numerical results ; Reactive blast waves ; Thermal radiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics , Technology
    Notes: Abstract The problem of reactive blast waves in a combustible gas mixture, where the heat release at the detonation front decays exponentially with the distance from the center, is analyzed. The central theme of the paper is on the propagation of reactive blast into a uniform, quiescent, counterpressure atmosphere of a perfect gas with constant specific heats. The limiting cases of Chapman-Jouguet detonation waves are considered in the phenomenon of point explosion. In order to deal with this problem, the governing equations including thermal radiation and heat conduction were solved by the method of characteristics using a problem-specific grid and a series expansion as start solution. Numerical results for the distribution of the gas-dynamic parameters inside the flow field are shown and discussed.
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    An improved method to determine free stream conditions in hypersonic facilities (1993)
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    Shock waves 3 (1993), S. 129-139 
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    ISSN: 1432-2153
    Keywords: Free stream conditions ; Shock stand-off distance ; Stagnation point heat flux ; Tangential velocity gradient ; Theory of Fay and Riddell ; Total enthalpy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics , Technology
    Notes: Abstract For determing pressure coefficients and Stanton numbers from the measured surface pressures and heat fluxes at a model surface, the dynamic pressure, mass flux and the total enthalpy of the free stream have to be known. Usually these values are determined by computing the wind tunnel nozzle flow. But a lot of uncertainties enter the computation which may lead to unreliable results. Therefore, a simple method was developed which yields the desired free stream conditions with high accuracy. This could be achieved by using mainly values which are measured within the test section. The method requires the measurement of the Pilot pressure, the stagnation point heat flux on a sphere and the static pressure of the free stream. For the static pressure an estimated value can also be used, because it has no large influence on the result. Some simple considerations show that the derived method is also valid for nonequilibrium free stream conditions. With the procedure presented the accuracy of the pressure coefficients and Stanton numbers could be increased significantly. Further, it improved the repeatability of these test results. This is very important for fundamental research, for the design of hypersonic vehicles as well as for CFD-validation with experimental data. The application of the method presented is not limited to short duration facilities, it can also be used for continuously working wind tunnels.
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    Calculation of intense self-similar anisotropic explosions (1993)
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    Shock waves 3 (1993), S. 113-128 
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    ISSN: 1432-2153
    Keywords: Explosion ; Self-similar solution
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract This paper discusses intense explosions with cylindrical or plane symmetry in a perfect inviscid gas at rest. The energy is added by a power law of time, which leads to self-similarity. The system of partial differential equations with two variables is expressed in intrinsic coordinates as a function of a Lagrangian variable and the curvilinear abscissa on the paths. An original computation method solves two equations on a dual characteristic of the problem and the other two by a Telenin method. The computations on a test case show that the method is very fast and is suitable for cases where no internal shock appears in the flow.
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    Blast waves in inhomogeneous atmospheres with counterpressure and heat transfer effects (1993)
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    Shock waves 3 (1993), S. 83-94 
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    ISSN: 1432-2153
    Keywords: Blast waves ; Isothermal atmospheres ; Point explosion
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract The study on blast waves in cold exponential atmospheres by Bach, Kuhl, and Oppenheim is extended to provide a uniformly valid numerical solution of a point explosion problem in isothermal exponential atmospheres with finite temperature at the centre. This is achieved initially by solving the equations of motion with the help of a perturbation technique which takes into account thermal radiation and heat conduction. Whereas the extended perturbation solution for the strong shock regime (i.e. short times after initiation) serves as a starting solution for the numerical integration, the solution using the method of characteristics is valid for the whole flow field since counterpressure effects and energy losses at the front are not neglected.
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    Focusing of weak shock waves on a target in a parabolic chamber (1993)
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    Shock waves 3 (1993), S. 1-10 
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    ISSN: 1432-2153
    Keywords: Acoustic ; Weak shock ; Focusing ; Pressure ; Parabolic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics , Technology
    Notes: Abstract Theoretical study of a weak shock focusing process in a confined chamber filled with liquid is presented. The chamber has a form of a thin cylinder with a parabolic cross-section, planar bottom and an arbitrary, although slowly varying, upper bounding surface. Analytical, numerical and experimental studies of weak shock wave focusing have been previously performed in the elliptic and ellipsoidal cases with a shock wave generated at one of the foci by means of an electric discharge or a microexplosion. In the present case a planar shock, perpendicular to the axis of the parabolic cross-section, sent in the inner of the chamber will converge at the focus after the reflection off the chamber wall, thus offering a different technical realization of the shock generation. The problem is solved within the frame of the geometrical acoustics approximation and a relation between the form of the upper bounding surface of the chamber and the pressure distribution behind the converging wavefront is obtained. It is shown that a desired pressure distribution may be obtained by an appropriate choice of the upper bounding surface.
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    Spectroscopic investigation of the discharge for PA-CVD of TiN (1993)
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    Plasma chemistry and plasma processing 13 (1993), S. 93-101 
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    ISSN: 1572-8986
    Keywords: PA-CVD ; pulsed DC discharge ; TiN layers ; emission spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Investigations of the discharge for PA-CVD of TiN on steel substrates are carried out using optical emission spectroscopy. A great number of species could be identified in the discharge. The growth rate of dense layers shows a direct dependence on Ti+ intensities. The occurrence of TiN in the discharge leads to f aky, not compact layers, lowering the hardness of the layers.
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    Air microwave-induced plasma: Relation between ion density and atomic oxygen density (1993)
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    Plasma chemistry and plasma processing 13 (1993), S. 103-116 
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    ISSN: 1572-8986
    Keywords: Air microwave plasma ; ion density ; oxygen atom density
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Electron temperature and ion density are measured in an air microwave-induced plasma (2450 MHz) by means of a floating double probe. A 'cinetic scheme for ion formation and decay is set up, and a relationship between atomic oxygen and ion densities is obtained. From this relationship an order-of-magnitude of atomic oxygen concentration in the discharge is derived and compared with results obtained by optical actinometry in another work.
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    Steel surface processing by a continuous optical discharge plasma (1993)
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    Plasma chemistry and plasma processing 13 (1993), S. 133-140 
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    ISSN: 1572-8986
    Keywords: Laser plasma ; optical discharge ; metal surface processing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract The influence of a continuous optical discharge (COD) plasma generated in flowing argon and argon-nitrogen mixture on alloy and carbon steel surfaces has been investigated. Changes in the structure, element composition, and microhardness of steel surface layers under the action of a COD plasma and laser beam were observed. In the presence of a COD plasma the microhardness distribution in hardened zone reaches its maximum at the metal surface and is different from that measured for samples processed by laser beam only.
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    Catalytic effect of iron wires on the syntheses of ammonia and hydrazine in a radio-frequency discharge (1993)
    Springer
    Plasma chemistry and plasma processing 13 (1993), S. 117-131 
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    ISSN: 1572-8986
    Keywords: Ammonia synthesis ; hydrazine synthesis ; Fe catalyst ; rf discharge ; plasma catalysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract The catalytic effect of iron wires on plasma syntheses of ammonia and hydrazine has been studied in the nitrogen-hydrogen plasma prepared using rf discharge at a pressure of 650 Pa (5 Torr). The product was mainly ammonia including a small amount of hydrazine. When iron wires were placed in the plasma downstream of the gas flow, the yields of both products increased, about two times in ammonia and two orders of magnitude in hydrazine. The yields increased with increasing number of wires (the surface area of the catalyst). The dissociative adsorption of nitrogen molecules and/or molecular ions on the iron surface and the formation of NHx by the reaction with hydrogen in the plasma followed by the formation of NH3 or N2H4 are considered as a reaction scheme. This is supported by the identification of NH3 with XPS of the surface of iron wires.
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    Fluid boundary layer effects in atmospheric-pressure plasma diamond film deposition (1993)
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    Plasma chemistry and plasma processing 13 (1993), S. 169-187 
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    ISSN: 1572-8986
    Keywords: Thermal plasmas ; chemical vapor deposition ; diamond film ; impinging jet ; atomic carbon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Diamond films were deposited in an atmospheric-pressure radio frequency plasma reactor. Hydrogen and methane were injected coaxially into the plasma as a high-velocity jet which impinged on the molybdenum substrate. In some cases argon was added to the reactant jet to increase its momentum, thereby reducing the boundary layer thickness. In most cases argon addition substantially, improved diamond growth. A numerical model was developed, which calculated two-dimensional reactor temperature and velocity, distributions, and the chemical kinetics in the boundary layer. The calculations indicate that under the experimental conditions argon addition reduced the thickness of the hydrogen nonequilibrium boundary layer from 3.5 to 1.0 mm. In addition, the calculations suggest that monatomic carbon may be a key diamond growth species under thermal plasma conditions.
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    Pulverized coal plasma gasification (1993)
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    Plasma chemistry and plasma processing 13 (1993), S. 141-167 
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    ISSN: 1572-8986
    Keywords: Plasma gasification ; lower-grade coals ; electric-arc reactor ; mathematical model of plasma gasification of coals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract A number of experiments on the plasma-vapor gasification of brown coals of three types have been carried out using an experimental plant with an electric-arc reactor of the combined type. On the basis of the material and heat balances, process parameters have been obtained: the degree of carbon gasification (ζc), the level of sulfur conversion into the gas phase (ζs), the synthesis gas concentration (CO+Hz) in the gaseous products, and the specific power consumption for the gasification process. The degree of gasification was 90.5-95.0%, the concentration of the synthesis gas amounted to 84.7–85.7%, and the level of sulfur conversion into the gas phase was 94.3–96.7%. Numerical study of the process of plasma gasification of coals was carried out using a mathematical model of motion, heating, and gasification of polydisperse coal particles in an electric-arc reactor of the combined type with an internal heat source (arc). The initial conditions for a conjugate system of nonlinear differential equations of the gas dynamics and kinetics of a pulverized coal stream interacting with the electric arc and oxidizer (water vapor) agree with the initial conditions of the experiments. The computation results satisfactorily correlate with the experimental data. The mathematical model can be used for the determination of reagent residence time and geometrical dimensions of the plasma reactor for the gasification of coals.
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    Numerical simulations of argon plasma jets flowing into cold air (1993)
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    Plasma chemistry and plasma processing 13 (1993), S. 189-209 
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    ISSN: 1572-8986
    Keywords: Turbulent plasma jets ; argon-air plasmas
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Computational results and comparisons with experimental data are presented for simulations of axisymmetric turbulent argon plasma jets flowing into a cold air environment. The calculations were performed using the LAVA code [J. D. Rarnshaw and C. H. Chang,Plasma Chem. Plasma Process. 12, 299 (1992)], and were designed to simulate experiments performed by Brossa and Pfender (Plasma Chem. Plasma Process. 8, 75 (1988)) (BP) and by Finckeet al (private communication, 1992] (FSH). To our knowledge, these are the first such simulations in which multicomponent diffusion and interactions between dissociation and ionization of different species are consistently, accounted for. Turbulence effects were represented by a standardκ-ɛ model, both with and without an axisymmetric jet correction term and for several different choices of the turbulent Prandil and Schmidt numbers Prt and Scl. Simulations were performed for one FSH experiment and two BP experiments at different values of torch powerP and argon flow rateW. The inflow profiles in the FSH simulations were adjusted to matchP,W, and the experimental data slightly downstream of the torch exit as closely as possible. The same profile shapes were then used to matchP andW for the BP simulations, for which data near the torch exit were not available. Swirl was neglected except in one of the FSH calculations, where it was found to have negligible effect, as expected. Best results were obtained with the axisymmetric jet correction term omitted and with Prt = Scl = 0.7. Agreement with the experimental data was then lair overall, but still showed systematic deviations and cannot be regarded as fully satisfactory. Possible reasons for the discrepancies are discussed.
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    Mass transfer in the gas phase during top-blowing with plasma jets (1993)
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    Plasma chemistry and plasma processing 13 (1993), S. 211-222 
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    ISSN: 1572-8986
    Keywords: Mass transfer ; top-blowing ; thermal plasmas ; nontransferred arc
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Deoxidation of copper melts by hydrogen has been investigated experimentally by top-blowing with argon-hydrogen plasma jets. The course of the deoxidation process has been described mathematically using kinetic laws. The overall divided course of the process can be examined in live partial steps, which are hydrogen transport within the gas phase, hydrogen transport within the melt, oxygen transport within the melt, reaction between hydrogen and oxygen, and H2O transport within the gas phase. Based on these five elementary processes, an equation for the velocity of deoxidation has been derived. The values of the rate of deoxidation resulting from this equation, in combination with the mass-transter coefficients valid for this process, have been compared to the experimental data. The results of this study verify those of former investigations on vaporization of elements out of copper melts. The mass-transfer coefficients are the same, when the local activity differences are used as the driving force for mass transport in a system. This means that the surface-renewal theory is valid, when mass-transfer coefficients are defined in this way. This is the case, at least, when metallic melts are subjected to top-blowing by plasma jets.
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    Electron scattering and dissociative attachment by SF6 and its electrical-discharge by-products (1993)
    Springer
    Plasma chemistry and plasma processing 13 (1993), S. 1-16 
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    ISSN: 1572-8986
    Keywords: Attachment rates ; cross section ; dissociative attachment ; electron scattering ; SF6, SF4, SO2, SOF2, SOF4, SO2F2
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Discrete electron-molecule processes relevant to SF6 etching plasmas are examined. Absolute, total scattering cross sections for 0.2–12-eV electrons on SF6, SO2, SOF2, SO2F2, SOF4, and SF4, as well as cross sections for negative-ion formation by attachment of electrons, have been measured. These are used to calculate dissociative-attachment rate coefficients as a function ofE/N for SF6 by-products in SF6.
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    Laser studies of the reactivity of SiO with the surface of a depositing film (1993)
    Springer
    Plasma chemistry and plasma processing 13 (1993), S. 61-76 
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    ISSN: 1572-8986
    Keywords: Gas-surface reactions ; IRIS technique ; SiO plasma film deposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract The reactivity of SiO produced in a SiCl4/O2 plasma with the surface of a depositing silicon oxide film has been measured to be near zero for surface temperatures of 25–500 °C using the IRIS technique (imaging of radicals interacting with surfaces). This method combines spatially resolved laser-induced fluorescence with molecular beam techniques. The SiO desorbs from the surface with a spatial distribution consistent with a cosine angular distribution.
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    Negative ion formation in compounds relevant to SF6 decomposition in electrical discharges (1993)
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    Plasma chemistry and plasma processing 13 (1993), S. 17-35 
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    ISSN: 1572-8986
    Keywords: Negative ions ; electron attachment ; dissociative electron attachment ; negative ion lifetimes ; time-of-flight mass spectrometry ; SF6 decomposition products ; SF6, SF4 SOF2, SO2F2, SOF4, SO2, SiF4
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Dissociative and nondissociative electron attachment in the electron impact energy range 0–14 eV are reported for SOF2 SOF4, SO2F2, SF4, SO2, and SiF4 compounds which can be formed by electrical discharges in SF6. The electron energy dependences of the mass-identified negative ions were determined in a time-of-flight mass spectrometer. The ions studied include F− and SOF 2 −* from SOF2; SOF 3 − and F− from SOF4; SO2F 2 −* , SO2F−, F 2 − , and F− from SO2F2; SF 4 −* and F− from SF4; O−, SO−, and S− from SO2; and SiF 3 − and F− from SiF4. Thermochemical data have been determined from the threshold energies of some of the fragment negative ions. Lifetimes of the anions SOF 2 −* , SO2F 2 −* , and SF 4 −* are also reported.
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    URL: http://dx.doi.org/10.1007/BF01447168
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    Mechanisms of surface processes in silicon etching (1993)
    Springer
    Plasma chemistry and plasma processing 13 (1993), S. 37-59 
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    ISSN: 1572-8986
    Keywords: Silicon etching ; surface processes ; mechanism ; silicon fluoride
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract A unified view on the mechanism allowing one to explain the experimental features governing spontaneous silicon etching by atomic fluorine is presented. Analysis of the phenomenological equation of adsorption shows a significant difference between etching mechanisms at high and low heat of adsorption on the surface being etched. As follows from the parameter estimates, one or another case can be realized under different experimental conditions. At steady-state the etching is argued to be determined only by the processes taking place on the SiF. film surface. To describe the process, it is necessary to understand the mechanism of overcoming the surface barrier for fluorine penetration into the film. At low heat of fluorine adsorption the barrier is overcome by thermal activation. In the opposite case the etching mechanism includes electron tunneling from silicon to adatoms and creation of a surface electric field. The field lowers the high energetic barrier for fluorine penetration. Based on the kinetic equations describing the electronic and atomic processes on the surface, the equation of the field strength is obtained. This equation is analyzed in different limit cases. The observed features are shown to be reproduced at some conditions on the parameters. Definite predictions on the temperature dependence of the etch rate are made.
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    URL: http://dx.doi.org/10.1007/BF01447169
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    Application of a rotating high-pressure glow discharge for the dissociation of hydrogen sulfide (1993)
    Springer
    Plasma chemistry and plasma processing 13 (1993), S. 77-91 
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    ISSN: 1572-8986
    Keywords: Hydrogen sulfide ; glow discharge ; atmospheric pressure ; magnetic field ; plasma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract The dissociation of hydrogen sulfide has been studied in an atmospheric-pressure glow discharge rotating between concentric electrodes in an axial magnetic field. Though the electrodes were heated to remove the sulfur formed in the discharge, stable operation was possible. The characteristics of the discharge and the influence of experimental parameters on the conversion of hydrogen sulfide and the energy efficiency are reported.
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    URL: http://dx.doi.org/10.1007/BF01447171
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    Modeling and experimental study of a transferred arc stabilized with argon and flowing in a controlled-atmosphere chamber filled with argon at atmospheric pressure (1993)
    Springer
    Plasma chemistry and plasma processing 13 (1993), S. 399-432 
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    ISSN: 1572-8986
    Keywords: Transferred arc ; controlled atmosphere ; experiment and modeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract For a transferred arc with a flat anode working at atmospheric pressure in an argon atmosphere, the influence of the gas injector design close to the cathode tip has been systematically studied for arc currents below 300 A, gas flowrates between 5 and 60 slm, and anode-cathode distances between 10 and 46 mm. Two types of injector configurations hare been studied: a cylindrical one with its wall parallel to the cathode axis and a conical one with the same cone angle as that of the cathode tip. The arc temperature was measured using flit, absolute intensity of ArI and ArII lines. Beside the roltagc and arc current, the losses at the cathode and at the anode were continuously recorded. An elliptic model was used to calculate the flow velocity, the temperature, and the current density close to the cathode and in the arc column. This model was either laminar or turbulent (K - ɛ), with the empirical constants being functions of the Reynolds nunther of turbulence. A cathode sheath with nonequilibrium conditions was used to obtain accurate cathode boundary conditions. Experiments and modeling hart shown the benefits of using conical injectors which constrict drasfically the plasma_ flow and enhance the gas velocity and the current density, thus increasing the heat flux to the anode. With the cylindrical injector, recirculations close to the cathode lip modify deeply its heating and reduce the plasma jet constriction: velocities and temperatures are lower when the recirculation velocity is higher. This results in lower heat fluxes to the anode compared to the conical injector.
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    URL: http://dx.doi.org/10.1007/BF01465873
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    Thermal plasma decomposition of chlorofluorocarbons (1993)
    Springer
    Plasma chemistry and plasma processing 13 (1993), S. 463-478 
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    ISSN: 1572-8986
    Keywords: Thermal plasma ; chlorofluorocarbon ; decomposition ; quenching ; hydrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Dichlorodifluoromethane was decomposed by a thermal argon plasma generated by a DC are discharge. The experiments and the kinetic calculations showed that the complete decomposition of the chlorofluorocarbon proceeded with the simultaneous additions of hydrogen and oxygen. Both the expertimental and calculated results confirmed that it is favorable, for the decomposition, not to quench the products but to add an excess of hydrogen over the stoichiometric amount, which leads to a reduction in chlorine formation.
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    URL: http://dx.doi.org/10.1007/BF01465876
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    Light paraffin oxidative conversion in a silent electric discharge (1993)
    Springer
    Plasma chemistry and plasma processing 13 (1993), S. 479-488 
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    ISSN: 1572-8986
    Keywords: Silent discharge ; oxidation of light paraffins ; experimental ; methanol ; ethanol ; formaldehyde ; acetaldehyde
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Methane, ethane, and their mixtures with oxygen have been passed through the silent electric discharge at various operating conditions Beside.carbon oxides and water, formaldehyde and methane, and acetaldehyde and ethanol from ethane were the other major products. The effect of temperature, pressure, discharge voltage, contact time, and oxygen concentration have been examined. The rate of oxygen consumption is almost independent of oxygen concentration and depends mainly on the discharge voltage. The selectivities of methanol formation from methane and ethanol/formation from ethane were 20 and 15%, respectively.
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    URL: http://dx.doi.org/10.1007/BF01465877
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    Ambipolar diffusion in two-temperature multicomponent plasmas (1993)
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    Plasma chemistry and plasma processing 13 (1993), S. 489-498 
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    ISSN: 1572-8986
    Keywords: Diffusion ; ambipolar ; two-temperature plasmas
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract A recent formulation of multicomponent diffusion in multitemperature gas mixtures [J. D. Ramshaw, J. Non-equilib. Thermodyn. 18. 121 (1993)] is applied to ambipolar diffusion in two-temperature multicomponent plasmas in zero magnetic field. Simplifications chic to the small electron muss are systematically exploited. A general expression is derived for the ambipolar electric field E. In the special case where the electron and heavy-particle temperatures are equal, this expression reduces to a result previously obtained using a self-consistent effective binary diffusion (SCEBD) approximation [J. D. Ramshaw and C. H. Chang,Plasma Chem. Plasma Process.11. 395 (1991)]. When thermal diffusion due to electrons is neglected, the heavy particles are shown to diffuse precisely as they would in the same E field if the electrons were entirely removed from the system. Finally, the SCEBD approximation for ambipolar diffusion in multicomponent plasmas is generalized to the case, of unequal electron and heavy-particle temperatures.
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    A self-consistent one-dimensional model for He nonequilibrium kinetics in RF discharges (1993)
    Springer
    Plasma chemistry and plasma processing 13 (1993), S. 499-519 
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    ISSN: 1572-8986
    Keywords: Boltzmann equation ; master equations ; fluid model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract A self-consistent one-dimensional model for nonequilibrium kinetics in RF discharges has been elaborated it which connects two different RF discharge modeling viewpoints: a microscopic vienpoint (Boltzmann equation for the electron energy distribution function, master equation for the electronic states of He) and a macroscopic one (fluid model). Ac results show the role of excited states in affecting the macroscopic properties (electron density, electron temperature. electric field) of the system. The reliability of the model is assessed by comparing the results obtained by it with existing experimental results. In general. a satisfactory agreement is obtained.
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    URL: http://dx.doi.org/10.1007/BF01465879
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    Low-temperature plasma etching of GaAs, AlGaAs, and AlAs (1993)
    Springer
    Plasma chemistry and plasma processing 13 (1993), S. 521-537 
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    ISSN: 1572-8986
    Keywords: Reactive ion etching ; loading ; uniformity ; anisotropy ; triode pattern transfer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Dry etching of compound semiconductors is becoming increasingly important as design ruler shrink for electronic devices. For photonic device applications, dry or plasma etching is used fin- device isolation, fine-line pattern transfer, and fabrication of optical quality interfaces. As has been well established for Si and W. plasma etching at reduced temperatures can provide superior critical dimension control and obviate the need for operating at high bias voltages that produce excessively energetic ion bombardment t. In this work, we explore low-temperature (−60 C to +60 C) etching of the compound semiconductors GaAs, AlGaAs, and AlAs, In addition to improving etch anisotropy, which provides critical dimension control, rye find thut processing at lower temperatures improves microuniformity and reduces loading effects. At high lemperaturcs, where larger samples are observed to etch more slowly than smaller pieces (loading effect), etching rates appear limited bv reactant transport to the wafer. In this regime, both microuniformity and macrouniformity arc poor. As the temperature is reduced, the etching rate becomes limited by surfitce processes us a residue containing the semiconductor elements, etchant gases, and residual background gases forms on the surface. hi this regime, the etch rare becomes independent of surface area and uniformity is improved.
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    Spectroscopic study of the reaction of tetramethyldisiloxane with a cold remote nitrogen plasma. Effect of dioxygen addition in the reactive mixture (1993)
    Springer
    Plasma chemistry and plasma processing 13 (1993), S. 539-554 
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    ISSN: 1572-8986
    Keywords: Cold remote nitrogen plasma ; siloxane ; plasma polymerization ; emission spectroscopy ; Si1 O1
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract The interaction of 1,1,3,3-tetramethyldisiloxane with a cold remote nitrogen plasma is studied by visible ultraviolet emission spectroscopy. Evolutions of emissions when dioxygen is added in the remote plasma region are correlated with the previously studied main characteristics of the polymeric deposition. The role of the energy vectors is discussed. New emissions are attributed to the triatomic Si O Si molecule.
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    URL: http://dx.doi.org/10.1007/BF01465881
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    Clusters in expanding plasma (1993)
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    Plasma chemistry and plasma processing 13 (1993), S. 673-684 
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    ISSN: 1572-8986
    Keywords: Clusters ; recombination ; condensation ; coagulation ; laser plasma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract An analysis is given of processes in a weakly ionized vapor expanding in a space and condensing on ions as nuclei of condensation. Processes including the growth and evaporation of clusters, mutual neutralization of clusters of different charges and coagulation are considered. Evolution of a laser plasma resulting from irradiation of a copper surface is analyzed. In the end a vapor of the plasma is transformed to charged clusters.
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    URL: http://dx.doi.org/10.1007/BF01570137
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    Simplified and complex modeling of self-sustained discharge-pumped, Ne-buffered XeCl laser kinetics (1993)
    Springer
    Plasma chemistry and plasma processing 13 (1993), S. 685-700 
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    ISSN: 1572-8986
    Keywords: Theoretical modeling ; XeCl laser ; vibrational kinetics ; electron energy distribution function
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Two simple kinetic models of a Ne-buffered XeCl laser discharge are presented based on different simplifications of the chemical kinetics of a complex model that recently appeared in the literature. When applied to the study of a small-volume XeCl laser, the results of both simple and complex models are in satisfactory agreement with the experiments. Shifting to a larger-volume laser, both models show problems due to loss of stability of the discharge. A one-dimensional modelling is performed, and it is found that different assumptions on the kinetics of the NeXe+ ion in the discharge lead to completely different results as regards the effect of a preionization-triggered instability.
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    URL: http://dx.doi.org/10.1007/BF01570138
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    Investigations concerning the work function of doped graphite (1993)
    Springer
    Plasma chemistry and plasma processing 13 (1993), S. 223-235 
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    ISSN: 1572-8986
    Keywords: Burning off of electrodes ; work function ; doped graphite electrodes ; Richardson equation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract In order to reduce the burning off of electrodes in electric arc furnaces, it is necesary to decrease the specific thermal load at the tip in the arc attachment area. This can be achieved by minimizing the work function of the electrode materials, whereby the peak temperature is reduced. The work function of doped graphite electrodes was investigated under conditions prevailing during standard industrial practice in order to achieve transferrable results. The measurement equipment developed to meet this requirement is based on a design first proposed by Bade and Yos. By measuring the peak temperature of the electrode and its current density, the value of the work function of the material was calculated with a modified Richardson equation. Starting from materials with well-known values of the work function, to verify, the accuracy of the experimental method and the mathematical model, those of pure and dopedgraphites were determined. The additives, oxides as a rule, result in a significant reduction in electron work function in the case of magnesium, calcium and cerium oxides.
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    Modeling of the cathode jet of a high-power transferred arc (1993)
    Springer
    Plasma chemistry and plasma processing 13 (1993), S. 237-271 
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    ISSN: 1572-8986
    Keywords: High-power transferred arc ; air plasma ; turbulence ; radiative transfer ; modeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract A physical model of two zones (constricted arc and cathode jet) of a 1-MW transferred arc in air is presented. It is based on the solution al conservation equations by a finite-differenee method. Turbulence is treated with Prandtl's approximation, whereas radiative transfer is solved considering a nonhontogeneous medium, with the hypothesis of gray spectral bands. The in of radiative transfer on the temperature field is illustrated using two-band and four-band radiation models. We also show the influence of several parameters on plasma jet properties: current intensity between 500 and 1500 A; gas mass /low rate between 10 and 90g/s, vortex injection. The arc characteristics are analyzed in accordance with physical mechanisms such as heat conduction, radiation, turbulence, convection, and miring of cold gas.
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    Study of a hollow cathode arc discharge in the presence of chromium oxide (1993)
    Springer
    Plasma chemistry and plasma processing 13 (1993), S. 273-287 
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    ISSN: 1572-8986
    Keywords: Hollow cathode arc discharge ; heterophase processes ; chromium oxide ; plasma diagnostics ; self-absorption method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract A hollow cathode arc discharge in hydrogen has been used for the purpose of chromium oxide reduction, the solid oxide being placed inside the anode. Mass transport from the oxide to the gas phase and excitation conditions in the plasma have been investigated. The results show that a substantial amount of oxide is transferred to the gas phase with subsequent reduction and deposition inside the cathode cavity, in the form of a pure metal. The residual part condenses on the discharge chamber wall as an amorphous substance, containing 50–60% of Cr metal, and on the anode surface under the form of a mixture of chromium oxide and metal crystals (10%). From spectroscopic investigations it follows that, inside the anode zone, total Cr concentration in the gas phase is of the order of 1014 cm−3, the excitation temperature of the atoms and ions being 4500 and 5500 K, respectively, and the ionization temperature being about 6000 K.
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    On mass- and emission spectroscopic CVD process monitoring of organometallics/O2 discharges (1993)
    Springer
    Plasma chemistry and plasma processing 13 (1993), S. 289-309 
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    ISSN: 1572-8986
    Keywords: Chemical vapor deposition ; organometallics ; mass spectroscopy ; optical emission spectroscopy ; process control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Mass spectroscopic analysis of neutrals and ions from a deposition plasma shows that the decomposition of the organometallic precursor compounds [La(thd)3, Cu(acac)2, and Al isopropoxide] in the plasma .starts with the abstraction of complete ligands. The mass spectra of plasma ions sensitively indicate the incomplete oxidation of the organic fragments with increasing organometallic partial pressure. The concentration of carbon-rich ions in the oxygen-based deposition plasma correlates with the carbon content of the deposited oxide films. Specific emissions of the precursor compounds (e.g., Cu atomic lines and LaO bands) can be used to monitor the precursor partial pressure; however, there is some interference with sputter emission from the deposited films. During La2O3 deposition, optical emission of oxidation products (e.g., OH, CO, CO2 bands) was used to regulate the precursor partial pressure in the discharge with a closed-loop control circuit.
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    Dry etching characteristics of III–V semiconductors in microwave BCl3 discharges (1993)
    Springer
    Plasma chemistry and plasma processing 13 (1993), S. 311-332 
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    ISSN: 1572-8986
    Keywords: Plasma etching ; electron cyclotron resonance ; discharges in BCl3 ; additional RF biasing ; selectivities
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Electron cyclotron resonance (ECR) BCl3 discharges with additional rf biasing of the sample position have been used to etch a variety of III–V semiconductors. GaAs and AlxGa1−xAs (x = 0−1) etch at equal rates in BCl3 or BCl3/Ar discharges, whereas SF6 addition produces high selectivities for etching GaAs over AlGaAs. These selectivities are in excess of 600 for dc biases of ≤−150 V, and fall to ≤6 for biases of −300 V. If the dc biases are kept to ≤ − 100 V, there is no measurable degradation of the optical properties of the GaAs and AlGaAs. The AlF3 formed on the AlGaAs surface during exposure to BCl3/SF6 plasmas can be removed by sequential rinsing in dilute NH4OH and water. In-based materials (InP, InAs, InSb, InGaAs) etch at slow rates with relatively rough morphologies in BCl3 plasmas.
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    Characteristics of vinyl iodide microwave plasma etching of GaAs/AlGaAs and InP/InGaAs heterostructures (1993)
    Springer
    Plasma chemistry and plasma processing 13 (1993), S. 333-350 
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    ISSN: 1572-8986
    Keywords: Plasma etching ; microwave discharges ; electron spectroscopy for chemical analysis ; addition of H2 and Ar
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Vinyl iodide (C2H3I) microwave discharges with additions of H2 and Ar are found to provide faster etch rates than conventional CH4/H2/Ar discharges for InP, InGaAs, GaAs, and AlGaAs. This is a result of the relatively high volatilities of indium, gallium, and aluminum iodide species. The etched features are smooth and anisotropic over a wide range of do self-biases (−150 to −350 V), process pressures (1–20mTorr), and microwave powers (150–500 W). The polymer that forms on the mask during the plasma exposure can be readily removed in O2 discharges. Electron spectroscopy for chemical analysis (ESCA) showed that the etched surfaces are slightly deficient in the group V elements under most conditions, but changes to the optical properties of the semiconductors are minimal. No defects are visible by transmission electron microscopy (TEM) in GaAs or InP samples etched at dc biases ≤ −250 V.
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    Air microwave-induced plasma: Detection of NO in the post-discharge using an ArF laser (1993)
    Springer
    Plasma chemistry and plasma processing 13 (1993), S. 351-364 
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    ISSN: 1572-8986
    Keywords: Air microwave plasma ; laser-induced fluorescence ; temperature ; nitrogen monoxide density
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract ArF laser-induced fluorescence (LIF) spectroscopy was applied to the investigation of the density of NO achieved in the post-discharge of an N2-O2 microwave-induced plasma (2450 MHz). The fluorescence spectrum provides a determination of NO vibrational temperature downstream the discharge. Absolute concentration profiles were determined in the low-temperature region of the post-discharge.
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    URL: http://dx.doi.org/10.1007/BF01466049
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    Temperature and density measurements in a recombining argon plasma with diluent (1993)
    Springer
    Plasma chemistry and plasma processing 13 (1993), S. 365-378 
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    ISSN: 1572-8986
    Keywords: Nonequilibrium ; plasma mixtures ; temperature measurements
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Spectroscopic and callorimetric measurements of temperature arid number density have been made using a 50-kW radio-frequency inductively coupled plasma (RFICP) torch operated at atmospheric pressure with maximum temperatures and electron densities near 8,1000 K and 2 x 1021 m3, respectively These measurements enabled the determination o/ the stale o/ equilibrium and of the corresponding applicability of rarious diagnostic techniques in hoth a recombining argon plasma and a recombining plasma with hydrogen or nitrogen. Results indicate that the Pure argon plasma is well described by u partial equilibrium model in which the free and bound-excited electrons are in mutual equilibrium irespective of possible departures from equilibrium with the ground state. The addition of just tenths of a percent of either atomic Hydrogen or nitrogen, however, disturbs this partial equilibrium hr argon plasmas with electron densities roughly less than 1021 m3 such that only diagnostic techniques which are independent o/ partial equilibrium assumptions can be reliably implemented.
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    Determination of the arc-root position in a DC plasma torch (1993)
    Springer
    Plasma chemistry and plasma processing 13 (1993), S. 379-397 
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    ISSN: 1572-8986
    Keywords: DC plasma torches ; anode arc root ; Steenbeck minimum ; principle ; analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract The behavior of an arc operated in the nontransferred mode with a conical-shaped cathode and a nozzle-shaped anode is studied by applying general tyro-dimensional conservation equations and auxiliary relations for the simulation of arc channel flows. The position of the arc-root attachment at the anode surface is determined by using Steenbeck's minimum principle, which postulates a minimum arc voltage for a given current and certain given boundary conditions. The overall effects of the anode-arc root on the plasma flow are, studied by comparing the results with those of the transferred mode of operation. Specific arc-channel diameters are chosen in the simulation in order to verify flit, numerical model through comparisons with experimental results. The results show that Steenbeck's minimum principle is useful for determining the position of the arc-root attachment at the anode surface. Application of this method for control of the arc-anode attachment may be valuable in the design and operation of plasma spray torches to avoid jet instabilities.
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    Synthesis of ultrafine SiC from rice hulls (husks): A plasma process (1993)
    Springer
    Plasma chemistry and plasma processing 13 (1993), S. 447-461 
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    ISSN: 1572-8986
    Keywords: Rice hulls ; thermal plasma synthesis: ultrafine SiC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Heat-treated rice hulls have been used as precursor material for synthesis of ultrafne SiC in a RF plasma reactor. Rice hulls containing finely distributed silica and active carbon act as a source for SiC formation. The plasma-synthesized powder contained ultrafnc β-SiC with excess carbon and some unreacted silica. Post-treatment processes such as oxidation and acid (HF) treatment appear to be effective in removing the excess carbon and silica.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01465875
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  • 93
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    Parametric study of atmospheric-pressure diamond synthesis with an inductively coupled plasma torch (1993)
    Springer
    Plasma chemistry and plasma processing 13 (1993), S. 433-446 
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    ISSN: 1572-8986
    Keywords: Diamond synthesis ; atmospheric pressure ; inductively coupled plasma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Polycrystalline diamond coatings have been deposited run molybdenum and silicon substrates using an inductively coupled, atmospheric-pressure plasma torch. Growth rates are on the order of 10 μ hr. The inductively coupled plasma reactor is found to produce a uniform, well-characterized growth environment for experimental and computational .study of the atmospheric-pressure diamond growth regime. Growth morphology is found to be sensitive to reactor conditions such as substrate surface temperature and methane-to-hydrogen feed ratio. An experimental parametric study of these variables is performed and the resultant growth analyzed by scanning electron microscopy, Raman spectroscopy, and X-ray diffraction Spectroscopic analysis of the gas phase is also performed. Results indicate that the, substrate temperature range over which diamond growth occurs shifts toward higher temperatures as the methane-to-hydrogen feed ratio is increased. The growth rate is observed to reach a maximum with varying methane-to-hydrogen feed ratio at constant substrate temperature. Raman analysis of the deposits indicates that higher-quality diamond is achieved at the highest limits of substrate temperature for a given methane-to-hydrogen ratio. Higher-quality diamond is also observed to be, formed at lower methane-to-hydrogen feed ratios.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01465874
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  • 94
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    Semiempirical method for extracting electron molecule cross sections from experimental data: CF4 as an example (1993)
    Springer
    Plasma chemistry and plasma processing 13 (1993), S. 655-671 
    Details
    ISSN: 1572-8986
    Keywords: Electron molecule interaction potential ; CF4 ; cross sections ; electron energy distribution function ; drift velocity ; characteristic energy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract A semiempirical method is described for calculating electron-molecule interaction potential, electron density, and elastic and vibrational inelastic cross sections using experimental data.CF 4 was considered as un example. Experimental data from IR and Raman spectra, molecular property calculations (dipole matrix elements, polarizability, distance between atoms in molecule), beam measurements of total, momentum transfer, and differential cross sections, and swarm data (diffusion and drift veolcity) are used for extracting the interaction potential, the molecule electron density, avid the differential cross sections. Electron energy distribution functions, drift velocity, and characteristic energy are calculated with the obtained differential e-CF 4 cross sections lierAr/CF 4 mixtures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01570136
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  • 95
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    Crazing dynamics in the swelling of thermally crosslinked poly(vinyl alcohol)-poly(acrylic acid) films (1993)
    Springer
    Journal of materials science 4 (1993), S. 5-11 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: A continuum kinetic model is used to describe the dynamics of crazing in a reticulated polymer film that is exposed to sudden hydration in order to form a hydrogel. The appearance of microfractures in a thermally crosslinked 80 wt% poly(vinyl alcohol)-20 wt% poly(acrylic acid) strip can be related to the internal strain of the polymer network and the thickness of the film. It is proposed that fractures are precipitated by the swelling of superficial layers of the polymeric matrix, which causes the drier middle layer to fail in tension when its yield stress is exceeded.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00122970
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  • 96
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    An investigation of the hardening process for several phosphate glass-containing cements (1993)
    Springer
    Journal of materials science 4 (1993), S. 111-116 
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    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: The hardening process for several phosphate glass-containing cements that have potential dental applications was investigated using both powder X-ray diffraction and Fourier-transform infrared spectral techniques. The investigated phosphate glasses contained various amounts of calcium, strontium and sodium ions. Crystalline brushite and amorphous phases whose concentrations and compositions depended on the compositions of the starting phases were formed during the hardening process for the cement. The study indicates that the use of phosphate glasses containing calcium and strontium ions in cement mixtures, rather than solid mixtures of the related metal oxides, sufficiently slows their hardening process so that commercially useful cements might be formed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00120379
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  • 97
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    Sintering behaviour and mechanical properties of hydroxyapatite and dicalcium phosphate (1993)
    Springer
    Journal of materials science 4 (1993), S. 150-158 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: The sintering behaviour of powders of two calcium phosphates, namely hydroxyapatite (HA) and dicalcium phosphate (DCP), were studied at various temperatures and in various environments. The density, flexural strength and Knoop hardness of HA sintered in air for 4 h initially increased with the sintering temperature, reaching maxima at around 1150°C, and then decreased due to decomposition of HA into tri- (TCP) and tetracalcium phosphates. Sintering in vacuum caused decomposition of HA at lower temperatures, and consequently the mechanical properties were poorer than those of HA sintered in air. The densification and mechanical properties of DCP sintered in air and vacuum showed similar behaviour to those of HA. In air DCP underwent phase transformation from γ- to β- and to α-phases. In vacuum DCP started to decompose into tricalcium phosphate at 1000°C. To reduce dehydroxylation, HA powder was sintered in moisture at various temperatures up to 1350°C and X-ray diffraction study did not indicate any decomposition at the highest sintering temperature. The density, flexural strength and hardness of HA sintered in moisture increased with the sintering temperature and eventually reached plateaux at about 1300°C, but below 1200°C they were lower than those of HA sintered in air at corresponding temperatures. Thus, it is seen that dehydroxylation did not hinder sintering of HA. On the other hand, decomposition obstructed sintering of both HA and DCP.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00120384
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  • 98
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    Influence of network characterisitics on diffusion in silicone elastomer (1993)
    Springer
    Journal of materials science 4 (1993), S. 175-178 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Owing to their excellent biocompatibility, silicone elastomers are very often studied to prepare controlled-release systems of therapeutic molecules. In order to produce a loaded matrix, the influence of the physical properties of elastomers on molecule diffusion has to be characterized. In this work the influence of the mesh size on progesterone diffusion was analysed. The results show a very important evolution of the diffusion coefficient, D, in the smallest meshes. On the other hand, in the largest meshes, an increase in the mesh size involves a very slight increase in D, approaching an asymptotic value. In addition to the size, the mesh form has a significant effect on molecule diffusion. Moreover, in the case of a mesh size dispersion the smallest meshes of the network have a fundamental action on the diffusion coefficient of the progesterone.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00120388
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  • 99
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    Experimental determination of short-term creep of femoral sheep bones and theoretical estimation of the dissipated energy during walking (1993)
    Springer
    Journal of materials science 4 (1993), S. 196-200 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: The short-term creep of ten fresh femoral sheep bones was determined through an analysis of their strain response in the time interval 10-2–103 s, under constant load corresponding to 100% body weight. The strain in the direction of minimum principal stress was measured by strain gauges attached at two points located on the ventral dorsal level at one-half and three-quarters of the bone's length, beginning from the knee joint. The experimental data were analysed using a three-parameter viscoelastic model consisting of a spring and a Kelvin element in series, and the material constants were calculated. The results indicate that the viscoelastic behaviour of femoral compact bone presents a transition phase with a time constant comparable with that of the normal walking period. Approximating the stress developed under walking conditions by a sinusoidal function, the corresponding strain time function and the dissipated energy due to viscoelastic mechanisms were estimated. According to our estimations the dissipated energy during normal walking conditions (speed 2.5 km h-1 and 60 steps min-1) was about 12%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00120392
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  • 100
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    Bone ingrowth behaviour of hydroxyapatite-coated, polyethylene-intruded and uncoated, sandblasted pure titanium implants in an infected implantation site: an experimental study in miniature pigs (1993)
    Springer
    Journal of materials science 4 (1993), S. 260-265 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: We studied the dynamics of bone tissue ingrowth into the pores of hydroxyapatite-coated (plasma-spraying technique) and uncoated wire meshes of pure Ti in an infected implantation site. Samples of the test materials were implanted into the femora of 15 adult Göttingen minipigs. Just before implantation they were contaminated with Staphylococcus aureus. The pigs were killed after 4, 8, 12 or 24 weeks. Undecalcified ground sections of bone tissue were prepared and stained with toluidine blue for comparative histological evaluation. The hydroxyapatite-coated implants already demonstrated advanced new bone formation after 4 weeks. By 12 weeks most of the implant pores were filled with newly formed bone although all samples showed macro- as well as microscopic signs of persistent infection. Comparable reactions of the uncoated implants could be observed only after 24 weeks. Signs of degradation of the hydroxyapatite coating were seen in contact with soft tissue. This was more extensive in the infected than in the uninfected site. The results and possible clinical consequences are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00122278
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