Abstracts of Selected Publications

CSE94e: Yao Zheng, Roland W. Lewis, David T. Gethin, Three-Dimensional Unstructured Mesh Generation: Part 1. Fundamental Aspects of Triangulation and Point Creation, Computer Methods in Applied Mechanics and Engineering, Vol. 134, No. 3/4, 249-268 (1996).; The present paper introduces an alternative approach for Delaunay triangulation, in which the triangulation is mapped from an equivalent convex hull in a higher dimension. Furthermore, some fundamental aspects of a point creation algorithm for unstructured mesh generation have been addressed based on numerical experiments. A point spacing tensor and point insertion criterion have been introduced aiming to deal with anisotropic meshes.
CSE94f: Yao Zheng, Roland W. Lewis, David T. Gethin, Three-Dimensional Unstructured Mesh Generation: Part 2. Surface Meshes, Computer Methods in Applied Mechanics and Engineering, Vol. 134, No. 3/4, 269-284 (1996).; This paper deals with surface patches and surface meshing. Triangular and quadrilateral patches in linear and quadratic forms, and Non-Uniform Rational B-Spline (NURBS) patch have been used to define surface geometry. From the real application point of view, data conversion between the mesh generator and some existing CAD packages has been considered. As a result of this study, converters from a graphics data standard and several CAD data formats have been implemented. The quality improvement of surface meshes has been discussed in terms of parametric plane stretching, diagonal swapping and smoothing procedures. Furthermore, a scheme of visual representation is introduced to utilize colour effect in validating the geometry and its surface meshes.
[Pictures: Triangular surface meshes]
CSE94g: Roland W. Lewis, Yao Zheng, David T. Gethin, Three-Dimensional Unstructured Mesh Generation: Part 3. Volume Meshes, Computer Methods in Applied Mechanics and Engineering, Vol. 134, No. 3/4, 285-310 (1996).; Volume meshes are generated through three-dimensional triangulation and interior point creation based on the surface meshes. To deal with non-convex geometries, boundary surface conformity is gained via edge swapping, boundary edge and surface recovery, and the robustness of the algorithm has been discussed in terms of the accuracy of geometric judgements. The performance of the mesh generator has been investigated by means of numerical experiments, and examples have been tested to validate the mesh generator. The possibility of extension of this mesh generator to incorporate with analysis programs, in terms of adaptive analysis, has been explored. This paper is also designed to briefly address mesh quality measures, quality statistics and mesh smoothing techniques. Using mesh quality metrics, visual quality assessment has been discussed. Furthermore, several general ways of visual representation of volume meshes have been introduced.
[Pictures: 3D tetrahedral meshes]
CSE94b: Roland W. Lewis, Yao Zheng and Asif S. Usmani, Aspects of Adaptive Mesh Generation Based on Domain Decomposition and Delaunay Triangulation, Finite Elements in Analysis and Design, Vol. 20, No. 1, 47-70 (1995).; The finite element method requires the generation of a mesh, based on an appropriate density distribution, so that the numerical analysis using it provides as optimal a result as possible with a reasonably low computational cost. The generation of inner points in a spatial domain of analysis may be accomplished via two types of quadtree decomposition for two-dimensional cases. The density formulations are quoted and analyses of their performance are given. Delaunay triangulation has been utilized within the mesh generator to connect the interior points. The robustness of this technique has been investigated. For real engineering applications, boundary recovery algorithms have been adopted in order to ensure the integrity of the boundary. A series of benchmark tests have been carried out on this work. Mesh quality improvement and the conversion from triangles to quadrilaterals has also been discussed.
[Pictures: 2D adaptive meshes]
CSE94c: Yao Zheng, Roland W. Lewis, David T. Gethin, FEView: An Interactive Visualization Tool for Finite Elements, Finite Elements in Analysis and Design, Vol. 19, No. 4, 261-294 (1995).; This paper presents a finite element visualization facility, FEView, which has been implemented based upon an object-oriented graphics library. The visualization tool works as an external module to an interactive program Geomview for viewing and manipulating geometric objects. The graphical user interface has been built on top of the Forms Library, a graphical user interface toolkit for Silicon Graphics workstations.; A finite element mesh can be considered as a collection of faces with edges, wire frame, or point cloud, and the corresponding numerical results gained through finite element analyses can be visualized via color shading and field icons (such as arrows) on the geometric shapes. Also, a scalar field can be represented as a weather map to highlight color shading domains with scalar values falling into the range of interest. Numerical results for two-dimensional cases can be shown with three-dimensional effects by using values of the scalar field. FEView provides animation control over single frame stepping and adjustable speed playing. It has been equipped with geometry operation functionality, in which a particular part of an object can be obtained by specifying material indices, element numbers, and cutting boxes. In local analysis mode, FEView is able to provide local information about finite element objects by picking up the position of interest via mouse manipulation.
[Pictures: FEView]
CSE02a: Yao Zheng, Nigel P. Weatherill and Edward A. Turner-Smith, An Interactive Geometry Utility Environment for Multi-Disciplinary Computational Engineering, International Journal for Numerical Methods in Engineering, Vol. 53, No. 6, 1277-1299 (2002).; A parallel simulation user environment (PSUE) has been developed for unstructured grid-based computational simulation. Arbitrary computer application software can be integrated into the environment to provide a multi-disciplinary engineering analysis capability within one unified computational framework. It provides an enhanced capability for complex and multiple problem definition, a graphics environment for guidance through the grid generation process with visual validation of each step, and robust and computationally efficient unstructured grid generation modules. This paper addresses an interactive geometry utility environment (IGUE), which is the primary part of the PSUE, providing sophisticated graphical user interfaces with geometric handling capability oriented to the unstructured grid technology. The IGUE is equipped with windowing functionality from the X-Window system, and its underpinning data structure is based on non-manifold topology.
[Pictures: PSUE][Pictures: IGUE]
CSEunb1: Yao Zheng, Nigel P. Weatherill and Edward A. Turner-Smith, A Paradigm of Interactive Geometry Utility Environments for Computational Science and Engineering: Part 1. Geometry Aspects, Submitted to Computing and Visualization in Science.; A Parallel Simulation User Environment (PSUE) has been developed for unstructured grid-based computational simulation. Arbitrary computer application software can be integrated into the environment to provide a multi-disciplinary engineering analysis capability within one unified computational framework. It provides an enhanced capability for complex and multiple problem definition, a graphics environment for guidance through the grid generation process with visual validation of each step, and robust and computationally efficient unstructured grid generation modules.; The primary part of the PSUE is an interactive geometry utility environment (IGUE), which provides sophisticated graphical user interfaces with geometric handling capability oriented to the unstructured grid technology. The IGUE is equipped with windowing functionality from the X-Window system (Motif), its underpinning data structure is based on Non-Manifold topology, and the 3-D graphics rendering library is OpenGL. This paper addresses the geometric fundamentals of the IGUE.
[Pictures: PSUE][Pictures: IGUE]
CSEunb2: Nigel P. Weatherill and Yao Zheng, A Paradigm of Interactive Geometry Utility Environments for Computational Science and Engineering: Part 2. Graphical User Interface and Computational Applications, Submitted to Computing and Visualization in Science.; A Parallel Simulation User Environment (PSUE) has been developed for unstructured grid-based computational simulation. Arbitrary computer application software can be integrated into the environment to provide a multi-disciplinary engineering analysis capability within one unified computational framework. It provides an enhanced capability for complex and multiple problem definition, a graphics environment for guidance through the grid generation process with visual validation of each step, and robust and computationally efficient unstructured grid generation modules.; The primary part of the PSUE is an interactive geometry utility environment (IGUE), which provides sophisticated graphical user interfaces with geometric handling capability oriented to the unstructured grid technology. The IGUE is equipped with windowing functionality from the X-Window system (Motif), its underpinning data structure is based on Non-Manifold topology, and the 3-D graphics rendering library is OpenGL. This paper addresses the graphical user interface aspects of the IGUE, and demonstrates its computational applications.
[Pictures: IGUE]
CSE00a: Yao Zheng, Nigel P. Weatherill, Edward A. Turner-Smith, Michail I. Sotirakos, Michael J. Marchant and Obey Hassan, Visual Steering of Grid Generation in a Parallel Simulation User Environment, Chapter 27 in Enabling Technologies for Computational Science: Frameworks, Middleware and Environments, The Kluwer International Series in Engineering and Computer Science, Vol. 548, E. N. Houstis, J. R. Rice, E. Gallopoulos and R. Bramley, eds., Pages 339-349, Kluwer Academic Publishers, Boston, 2000, (ISBN 0-7923-7809-1).; The traditional cycle in grid generation is to prepare geometry data, to execute a grid generator and to analyse the resultant grids. However, more insight and a higher degree of productivity can be achieved if these activities can be carried out under the direct visual control of the user. This is the underlying philosophy of visual steering, where the user can change parameters, interactively manipulates geometries and generates grids in a more controllable and productive manner. The paper will describe an on-going research activity to develop a more flexible software environment for computational simulation, to reduce the time to generate grids and to make the grid generation process more effective in a design environment.
[Pictures: PSUE][Pictures: IGUE]
CSE01a: Yao Zheng, Nigel P. Weatherill and Obey Hassan, Topology Abstraction of Surface Models for Three-Dimensional Grid Generation, Engineering with Computers, Vol. 17, No. 1, 28-38 (2001).; Surface grid generation and the subsequent volume grid generation is the key to unstructured grid-based computational simulation. The baseline entities of the surface models under consideration for use with the proposed surface grid generator are curves and surfaces. There is a necessity to establish a topology relation between the curves and surfaces, prior to a surface gridding process. The present paper addresses issues related to this topology abstraction. Effort has also been made to generally discuss how to bridge the gap between CAD modelling and surface gridding. The proposed procedures have been incorporated into an Interactive Geometry Utility Environment (IGUE). The IGUE is a sub-environment of a Parallel Simulation User Environment (PSUE), which has been developed for unstructured grid-based computational simulation. Arbitrary computer application software can be integrated into the environment to provide a multi-disciplinary engineering analysis capability within one unified computational framework. Examples of computational applications have been included in the present paper, to demonstrate the use of the PSUE and geometry preparation procedure with an emphasis of topology abstraction.
[Pictures: IGUE]
CSE00b: Yao Zheng, Nigel P. Weatherill, An Interactive Geometry Utility Environment for Grid Generation, Presented at the 4th Asian Computational Fluid Dynamics Conference (Mianyang, Sichuan, China, September, 2000), Proceedings of the 4th Asian Computational Fluid Dynamics Conference, H. Zhang, ed., University of Electronic Science and Technology of China Press, Sichuan, China, 2000, 732-737, (ISBN 7-81065-470-5/Z.9).; An Interactive Geometry Utility Environment (IGUE) has been developed to provide sophisticated graphical user interfaces with geometric handling capability oriented to the unstructured grid technology. It is equipped with windowing functionality from the X-Window system (Motif), its underpinning data structure is based on Non-Manifold topology, and the 3-D graphics rendering library is OpenGL. The IGUE is a primary part of a Parallel Simulation User Environment (PSUE). Within the PSUE, arbitrary computer application software can be integrated to provide a multi-disciplinary engineering analysis capability in one unified computational framework.
[Pictures: IGUE]
CSE94d: Yao Zheng, Recent Advances in Computational Mechanics at Swansea (in Chinese), Selected Research Topics on Applied Mechanics in the UK, Tongxi Yu, Danong Dai, Ling Zhu, eds., Pages 167-181, Science Press, Beijing, China, 1996, (ISBN 7-03-005001-0/O.830).; In the present paper, an attempt has been made to address some recent advances in computational mechanics at the Department of Civil Engineering, University College of Swansea, which is a leading research center for numerical methods in engineering. Various topics of the theories and applications have been mentioned, with the inclusion of the following ten aspects: Adaptivity, Mesh Generation, Parallel Computing, Solid Mechanics, Structural Mechanics, Fluid Dynamics, Heat and Mass Transfer, Casting Process, Forming Process, and Geomechanics. This review is mainly based on the selected papers presented since the year 1990, the list of which is given in the bibliography.
CSE94a: Yao Zheng, Roland W. Lewis, and David T. Gethin, Some Aspects of Unstructured Mesh Generation, Proceedings of the 4th International Conference on Numerical Grid Generation in Computational Fluid Dynamics and Related Fields (Swansea, UK, April 1994), Numerical Grid Generation in Computational Fluid Dynamics and Related Fields, (eds. N. P. Weatherill, P. R. Eiseman, J. Hauser, J. F. Thompson), Pineridge Press, Swansea, UK, 1994, 765-778.; The first part of this paper introduces an alternative approach for Delaunay triangulation, in which the triangulation is converted from a corresponding convex hull. Furthermore, some robustness aspects of the triangulation and the associated boundary recovery have been discussed within the framework of Epsilon Geometry.
CSE93c: Yao Zheng, Roland W. Lewis, David T. Gethin, A Visualization Facility Built on Object-Oriented Graphics for Finite Elements, Presented at the 3rd International Conference on Computational Graphics and Visualization Techniques (Alvor, Algarve, Portugal, December, 1993), Combined Proceedings of EDUGRAPHICS'93 and COMPUGRAPHICS'93, H. P. Santo, ed., 283-290.; This paper presents a finite element visualization facility which has been implemented based on an object-oriented graphics approach. Finite element meshes can be considered as general geometry objects and the corresponding numerical results gained through finite element analysis can be visualized via colour shading on the objects mapped with element meshes. The visualization system developed consists mainly of two parts: a mesh viewing program FEMeshView and a contour viewing program FEContourView, which work as external modules to an interactive program Geomview for viewing and manipulating geometric objects. The graphical user interface has been built on the top of the Forms Library, a graphical user interface toolkit for Silicon Graphics workstations.
CSE93d: Yao Zheng, Asif S. Usmani, Roland W. Lewis, On the Point Generation for Adaptive Finite Elements Using Domain Decomposition, Presented at the 3rd International Conference on Computational Graphics and Visualization Techniques (Alvor, Algarve, Portugal, December, 1993), Combined Proceedings of EDUGRAPHICS'93 and COMPUGRAPHICS'93, H. P. Santo, ed., 323-330.; With the development of the finite element method, it is required that a mesh can be generated based on an appropriate density distribution to make the numerical analysis provide as good a result as possible with a reasonably low computational cost. To generate inner points of a domain, two types of quadtree decomposition are used for two-dimensional cases. The density formulations are given with investigations of their performance, and a series of benchmark tests have been carried out in this paper.
CSE93a: Roland W. Lewis, Yao Zheng and David T. Gethin, Interactive Specification of Three-Dimensional Multiblock Topologies, Advances in Engineering Software, Vol. 18, No. 2, 121-130 (1993).; A scheme is described in this paper to deal with the topological and geometrical data which must be specified for macro-block based mesh generators. The topological and geometrical data is inputted interactively with the aid of graphical facilities, which reduces the burden on users of editing such large data files. The corresponding mesh generator uses macro-blocks as geometrical primitives described by isoparametric hexahedral elements, each of twenty nodes, and subdivides them into required meshes.
[Pictures: 3D multiblock meshes]
CSE96a: M.J. Marchant, N.P. Weatherill, E. Turner-Smith, Y. Zheng, M. Sotirakos, A Parallel Simulation User Environment for Computational Engineering, Proceedings of the 5th International Conference on Numerical Grid Generation in Computational Field Simulations (Mississippi, USA, April, 1996), Numerical Grid Generation in Computational Field Simulations, (eds. B.K. Soni, J.F. Thompson, J. Haeuser, P. Eiseman), Mississippi State University, MS, USA, 1996, Vol. 1, 741-751.; A computer environment has been developed for computational engineering. The parallel simulation user environment (PSUE) provides an enhanced capability for complex and multiple problem definition. Developments aim at integrating CAD and grid generating capabilities, addressing end-user requirements and data formats. This will include the provision of tools to correct invalid geometries, a graphics environment for guidance through the grid generation process with visual validation of each step, and robust and computationally efficient unstructured grid generation modules. The environment also provides the functionality for arbitrary engineering software applications to be integrated and analysis modules executed on computer platforms, including parallel computers. The paper will describe the key software architectural features together with the functionality of the environment.
CSE96c: N.P. Weatherill, M.J. Marchant, E. Turner-Smith, Y. Zheng, M. Sotirakos, The Design of a Graphical User Environment for Multi-Disciplinary Computational Engineering, Proceedings of the 2nd ECCOMAS (the European Community on Computational Methods in Applied Sciences) Conference on Numerical Methods in Engineering (Paris, France, September, 1996), ECCOMAS'96: Numerical Methods in Engineering'96, (eds. J.-A. Desideri, P. Le Tallec, E. O'Nate, J. Periaux, E. Stein), John Wiley & Sons, Chichester, UK, 1996, 810-818 (ISBN 0-471-96692-4).; A computer software environment has been developed for pre and post-processing for unstructured grid-based computational simulation. Arbitrary computer application software can be integrated into the environment to provide a multi-disciplinary engineering analysis capability within one unified computational framework. Reeognising the computational demands of many application areas, the environment includes a set of parallel tools to help the user maximise the potential of high performance computers and networks. The paper will present details of the environment and include a discussion on the integration of application software.
CSE03a: Guiyi Wei, Yao Zheng, Jifa Zhang, Guanghua Song, An Engineering Computation Oriented Visual Grid Framework, Proceedings of the Second International Workshop on Grid and Cooperative Computing (GCC2003) (Shanghai, China, 2003), Grid and Cooperative Computing: Second International Workshop, GCC 2003, Part I, Lecture Notes in Computer Science, Vol. 3032, (eds. M. Li, et al), Springer-Verlag, Heidelberg, 2004, 51-58.; Grid computing technology is a focused field in high performance computing. This paper describes an engineering computation oriented visual grid framework VGrid, which is capable to bridge the gap between currently deployed grid services and the computational applications. Based on the Globus toolkit, and coupled with a client component, a services pool and a server component, VGrid visually performs resource discovery, task schedule, and result processing. VGrid improves the efficiency of utilization of resources by introducing a logical resource concept. VGrid applications of numerical simulations in engineering sciences are demonstrated.
CSE03b: Guiyi Wei, Yao Zheng, Jifa Zhang, Grid Service-Based Parallel Finite Element Analysis, Proceedings of the Second International Workshop on Grid and Cooperative Computing (GCC2003) (Shanghai, China, 2003), Grid and Cooperative Computing: Second International Workshop, GCC 2003, Part I, Lecture Notes in Computer Science, Vol. 3032, (eds. M. Li, et al), Springer-Verlag, Heidelberg, 2004, 123-130.; In this paper, we present our work on the integration of existing engineering applications using Grid Services. We address a visual grid framework that provides an integrated development environment for engineering computation applications. Furthermore, we demonstrate how such services can interact with each other. These interactions enable a level of integration that assists the scientific application architect in leveraging applications running in heterogeneous runtime environments. Our framework is implemented by using the existing infrastructures and middleware, the Globus Toolkit. We test our framework for computation solid mechanics applications that require large data transferring, interactive steering, using of multiple platforms, visualization, and access via a portal with graphic interface.
CSE03c: Changqin Huang, Yao Zheng, Deren Chen, A Scheduling Approach with Respect to Overlap of Computing and Data Transferring in Grid Computing, Proceedings of the Second International Workshop on Grid and Cooperative Computing (GCC2003) (Shanghai, China, 2003), Grid and Cooperative Computing: Second International Workshop, GCC 2003, Part II, Lecture Notes in Computer Science, Vol. 3033, (eds. M. Li, et al), Springer-Verlag, Heidelberg, 2004, 105-112.; In this paper, we present a two-level distributed schedule model, and propose a scheduling approach with respect to overlap of computing and data transferring. On the basis of network status, node load, and the relation between task execution and task data access, data transferring and computing can occur concurrently in the following three cases: a) A task is being executed on a part of its dataset when the other of its dataset is being replicated; b) A dataset of a scheduled task is being replicated to a node, at which another task is running; c) Data exchange happens when dependant subtasks are running at different nodes. Corresponding theoretical analysis and experimental results demonstrate that the scheduling approach improves execution performance and resource utilization.
CSE03d: Haolin Feng, Guanghua Song, Yao Zheng, Jun Xia, A Deadline and Budget Constrained Cost-Time Optimization Algorithm for Scheduling Dependent Tasks in Grid Computing, Proceedings of the Second International Workshop on Grid and Cooperative Computing (GCC2003) (Shanghai, China, 2003), Grid and Cooperative Computing: Second International Workshop, GCC 2003, Part II, Lecture Notes in Computer Science, Vol. 3033, (eds. M. Li, et al), Springer-Verlag, Heidelberg, 2004, 113-120.; Computational grid has a promising future in large-scale computing, because it enables the sharing of widely distributed computing resources. Good managements with excellent scheduling algorithms are in great demand to take full advantage of it. Many scheduling algorithms in grid computing are for independent tasks. However, communications are very common in scientific computing programs. In this paper, we will propose an easy-implemented algorithm to schedule the tasks with some communications. Our algorithm is suitable for a large proportion of scientific computing programs, and is based on Binary Integer Programming. It is able to meet the users¡¯ quality of service (QoS) requirements, and to minimize the combination of costs and time consumed by the users¡¯ programs. We will give an example of scheduling a typical scientific computing task to show the power of our algorithm. In our experiment, the grid resource consists of an SGI Onyx 3900 supercomputer, four SGI Octane workstations, four Intel P4-2.0GHz PCs and four Intel P4-1.8GHz PCs.
CSE04a: Changqin Huang, Deren Chen, Yao Zheng, and Hualiang Hu, Performance-Driven Task and Data Co-Scheduling Algorithms for Data-Intensive Applications in Grid Computing, Proceedings of the Sixth Asia Pacific Web Conference (APWEB'04) (Hangzhou, China, 2004), Advanced Web Technologies and Applications, APWeb 2004, Lecture Notes in Computer Science, Vol. 3007, (eds. J.X. Yu, X. Lin, H. Lu, Y. Zhang), Springer-Verlag, Berlin, Heidelberg, 2004, 331-340.; To gain higher performance under many constraints, effective scheduling is a key concern in data-intensive grid computing. Based on a Dual-Component and Dual-Queue Distributed Schedule Model (DCDQDSM), we present task and data co-scheduling algorithms, by which the waiting time to access datasets for the scheduled task will reduce. Firstly data replication and elimination schedule are processed by an independent approach. Secondly, if a task is divisible, the task and its dataset are divided into subtasks and their necessary data subsets. Task scheduling adopts a general approach. Finally, when a scheduled task/subtask doesn¡¯t hit its dataset, associated data transferring is bound to this task. On the basis of relation between task execution and data access, data replication and computing may proceed concurrently in one scheduled task with divisible dataset or between scheduled tasks. Corresponding theoretic analysis and experimental results suggest that the scheduling algorithms improve execution performance and resource utilization.
CSE04b: Changqin Huang, Guanghua Song, Yao Zheng, Deren Chen, An Authorization Architecture Oriented to Engineering and Scientific Computation in Grid Environments, Proceedings of the Ninth Asia-Pacific Computer Systems Architecture Conference (ACSAC 2004) (Beijing, China, 2004), Advances in Computer Systems Architecture, Lecture Notes in Computer Science, Vol. 3189, (eds. P.-C. Yew and J. Xue), Springer-Verlag, Berlin, Heidelberg, 2004, 461-472.
Large-scale scientific and engineering computation is normally accomplished through the interaction of collaborating groups and diverse heterogeneous resources. Grid computing is emerging as an applicable paradigm, whilst, there is a critical challenge of authorization in the grid infrastructure. This paper proposes a Parallelized Subtask-level Authorization Service architecture (PSAS) based on the least privilege principle, and presents a contextaware authorization approach and a flexible task management mechanism. The minimization of the privileges is conducted by decomposing the parallelizable task and re-allotting the privileges required for each subtask. The dynamic authorization is carried out by constructing a multi-value community policy and adaptively transiting the mapping. Besides applying a relevant management policy, a delegation mechanism collaboratively performs the authorization delegation for task management. In the enforcement mechanisms involved, the authors have extended the RSL specification and the proxy certificate, and have modified the Globus gatekeeper, jobmanager and the GASS library to allow authorization callouts. Therefore the authorization requirement of an application is effectively met in the presented architecture.
CSE04c: Guiyi Wei, Guanghua Song, Yao Zheng, Cuiju Luan, Chaoyan Zhu, Wei Wang, MASSIVE: A Multidisciplinary Applications-Oriented Simulation and Visualization Environment, Proceedings of the 2004 IEEE International Conference on Services Computing, SCC 2004 (Shanghai, China, 2004) (eds. Liang-Jie Zhang, Minglu Li, Amit P. Sheth, Keith G. Jeffery), IEEE Computer Society, Los Alamitos, California, 2004, 583-587.
The objective of the MASSIVE project is to build a Grid platform to enable large-scale and distributed scientific and engineering computations. Its focus is numerical simulation and visualization. This paper addresses a prototype Grid utilizing resources at the Center for Engineering and Scientific Computation (CESC) in Zhejiang University (ZJU). This Grid is capable of taking a model geometry generated by CAD systems, transferring it to an SGI Onyx 3900 supercomputer where it is meshed. The meshed geometry is then transferred to a Dawning PC cluster where it is used to solve computational fluid dynamics and computational solid mechanics problems and it is finally visualized showing numerical results.
CSE04d: Changqing Huang, Guanghua Song, Yao Zheng, Quality-of-Service Driven Visual Scheduling in Grid Computing, Proceedings of the GCC 2004 International Workshops, IGKG, SGT, GISS, AAC-GEVO, and VVS, (Wuhan, China, 2004), Grid and Cooperative Computing - GCC 2004 Workshops, Lecture Notes in Computer Science, Vol. 3252, (eds. Hai Jin, Yi Pan, Nong Xiao, and Jianhua Sun), Springer-Verlag, Berlin, Heidelberg, 2004, 744-752.
To make full use of grid resources and to meet users¡¯ requirements, efficient scheduling is a key concern in grid environments. Aiming at gridbased engineering computation applications, this paper proposes a Quality of Service (QoS) driven user-centric scheduling strategy. Firstly, degree of credit and degree of guarantee are defined, and aggregate utility ratio is modeled as a composite QoS; Secondly, for different types of grid users, two scheduling methods and steering-enabled visual interfaces are presented, respectively; Thirdly, four performance metrics and aggregate utility ratio are visualized to facilitate the user¡¯s interaction with scheduling; Finally, corresponding postscheduling mechanisms are designed to cope with scenarios where scheduled tasks could not obtain expected QoS. This study is part of a grid project, MASSIVE, and the experiments show that the visual scheduling strategy presented is suitable for computational grids.
CSE04e: Lijun Xie, Yao Zheng, Jifa Zhang, Xin Huang, Zhengge Huang, EEMAS: An Enabling Environment for Multidisciplinary Application Simulations, Proceedings of the GCC 2004 International Workshops, IGKG, SGT, GISS, AAC-GEVO, and VVS, (Wuhan, China, 2004), Grid and Cooperative Computing - GCC 2004 Workshops, Lecture Notes in Computer Science, Vol. 3252, (eds. Hai Jin, Yi Pan, Nong Xiao, and Jianhua Sun), Springer-Verlag, Berlin, Heidelberg, 2004, 681-688.
EEMAS environment is a problem-solving environment for multidisciplinary application simulations. Within the EEMAS, there are four categories of modules involved, namely pre-processing module, computing module, postprocessing module, and platform control module. The EEMAS is developed for complex and large-scale simulations to take advantage of powerful parallel and distributed computing technologies. All the modules are coupled through a software bus, which maintains the share memory and makes the modules integrated seamlessly. In the present paper, detailed design principles and applications of the EEMAS are addressed.
CSE04f: Yao Zheng, Guanghua Song, Jifa Zhang, Jianjun Chen, An Enabling Environment for Distributed Simulation and Visualization, Proceedings of the 5th IEEE/ACM International Workshop on Grid Computing (Grid 2004) (Pittsburgh, USA, 2004), (ed. R. Buyya), IEEE Computer Society, Los Alamitos, California, 2004, 26-33.
In this paper we present the MASSIVE project that aims to use Grid technology to establish an enabling environment for distributed simulation and visualization of large-scale scientific and engineering research. The project focuses on collaborative numerical simulation and visualization in grid environments. Furthermore, the project is also to develop Grid-enabled capability and products for use by the wider community. The current status of the MASSIVE project is reported and a prototype Grid utilizing resources at the Center for Engineering and Scientific Computation (CESC) in ZheJiang University (ZJU) is discussed. This Grid gets a model geometry generated by CAD systems and transfers it to an SGI Onyx 3900 supercomputer where it is meshed. The meshed geometry is then transferred to a DAWNING PC Cluster where it is used to solve computational fluid dynamics and computational solid mechanics problems and it is finally visualized showing numerical results.
CSE04g: Yao Zheng, Mesh Generation and Visual Steering in Engineering and Scientific Computation (Keynote Lecture), Computational Mechanics, Proceedings of the Sixth World Congress on Computational Mechanics (WCCM VI) in conjunction with the Second Asian-Pacific Congress on Computational Mechanics (APCOM'04) (Beijing, China, 2004), (eds. Z. H. Yao, M. W. Yuan, W. X. Zhong), Tsinghua University Press & Springer-Verlag, Beijing, 2004, 782-787, (ISBN 7-302-09343-1).
This paper addresses current technologies of mesh generation and visual steering of computing procedures, and the future directions of research towards this end. Mesh generation continues to be the pacing technology for a practical numerical analysis. Composite structured mesh schemes and unstructured mesh schemes currently are the two mainstream approaches. A method that properly employs a hybrid of structured and unstructured meshes may prove to be fruitful. As computational analysis techniques have matured, their use has spread rapidly beyond the research environment into industry. The need to distribute both the data and computational effort amongst multiple processors, or computers, becomes evident. In an attempt to make numerical simulation more efficient, a visual steering environment is required for engineering and scientific computation.
CSE04h: Jifa Zhang, Yao Zheng, Parallel Meshfree Computation for Finite-Strain Elasto-Plastic Problems with Cam-Clay Model, Computational Mechanics (Abstracts), Vol. 2, Abstracts of the Papers Presented at the Regular Sessions of the Sixth World Congress on Computational Mechanics (WCCM VI) in conjunction with the Second Asian-Pacific Congress on Computational Mechanics (APCOM'04) (Beijing, China, 2004), (eds. Z. H. Yao, M. W. Yuan, W. X. Zhong), Tsinghua University Press & Springer-Verlag, Beijing, 2004, Page 65, (ISBN 7-302-09342-3).
Owing to severe mesh distortion, standard finite element approaches are still ineffective in handling extreme material deformation, such as large deformations and moving discontinuities. In order to improve the effectivity, meshfree methods have been developed. Among these methods, Reproducing Kernel Particle Methods (RKPM) have demonstrated their greater suitability for structural analysis. After a review of meshfree methods and an introduction to the RKPM, applications of the RKPM to finite-strain elasto-plastic problems are presented. As an illustrative case, a slope stability problem with the finite-strain Cam-clay model for geomaterials is analyzed. Being different from using the classical additive decomposition, this finite-strain Cam-clay model is presented by using multiplicative elasto-plastic decomposition of the deformation gradients. The numerical simulations are carried out on an SGI Onyx 3900 supercomputer with 1, 4, 8, 16, 24 and 32 processors utilized, respectively. Under the same condition, the RKPM and the FEM are compared. The comparison shows that the RKPM is more suitable for the problems where there exists extreme large strain such as the slope sliding.

Civil Engineering (Geotechnical Engineering; Structural Engineering; Engineering Optimization)

CE94b: Yao Zheng, Roland W. Lewis, Several Algorithms of Global Optimal Search, Advances in Engineering Software, Vol. 21, No. 2, 87-98 (1994).; A randomized global optimization algorithm called Multi-Stage Monte-Carlo Optimization (MSMCO) is presented based on the concept of neighbourhood search. The MSMCO consists of several stages, and in each of them there are several substages of random walks. Every stage starts with a favourable initial point from the previous stage so that it is possible to consider the overall structure of the objective function and to lead to a global optimum. The favourable initial point for every stage is determined by means of a statistical analysis. The performance of the algorithm is investigated in numerical examples.; After an introduction to simulated annealing, a quasi simulated annealing (QSA) scheme is put forward, which is based on the frame of the MSMCO, and benefited from some features of simulated annealing method. Numerical experiments shown demonstrate the effectiveness of this algorithm.
CE9293a: Yao Zheng and Roland W. Lewis, On the Optimization Concept of Grey Systems, Applied Mathematical Modelling, Vol. 17, No. 7, 388-392 (1993).; A system containing known values and uncertain unknown ones is called a grey system, and its mathematical model contains known quantities and uncertain unknown ones (termed grey quantities). An optimization analysis of such a grey system is, conceptually, such a problem in which both the objective function and constraint condition include grey quantities. In this paper, an optimization concept of grey systems is put forward, and the problem of grey optimization is changed into a general optimization problem in the common sense. By means of the theoretical analysis and numerical examples, it is demonstrated that the proposed concept is reasonable and meaningful.
CE92a: R. W. Lewis, Y. Zheng, Coarse Optimization for Complex Systems: An Application of Orthogonal Experiments, Computer Methods in Applied Mechanics and Engineering, Vol. 94, No. 1, 63-92 (1992).; In optimization problems, if the objective function together with (or without) the constraint conditions is so complicated that it is very time consuming to calculate the function values, the system is termed a complex system. In the present paper, partial derivative values are not required, and the optimization procedure is unconstrained. The aim is to find a method of dealing with the coarse optimization of a complex system. This requires fewer function values which will result in favourable points in the context of coarse optimization.; The proposed method is an orthogonal experiment, which is based on an orthogonal table (in combinatorial mathematics) which satisfies the principle of orthogonality, i.e. uniform scatterance and orderly comparability. The method is described in detail, an orthogonal table generator ORTHTAB which generates ordinary orthogonal tables is provided, and a comparison with a standard simplex optimization method is given in the numerical results. The numerical examples demonstrate that the proposed method is effective, and can reduce the frequency of evaluating function values (compared with a simplex method). Also, the solution is characterized as being optimal within the overall context.
CE8687a: Zupei Yuan, Yao Zheng, The Collapse Load of Orthotropic Plates (in Chinese), Journal of Harbin Institute of Technology, No. 4, 8-16 (1987).; Based on the yield criterion suggested by R. Hill, an analysis of the carrying capacity of orthotropic plates is presented. A formula used to calculate the moment acting on the section where the yield hinge lies is given with an example of a rectangular plate simply supported in the boundary and subjected to the uniform load.

Mechanical Engineering (Casting; Welding; Heat Transfer)

ME93a: Rajesh S. Ransing, Yao Zheng, Roland W. Lewis, Potential Applications of Intelligent Preprocessing in the Numerical Simulation of Castings, Proceedings of the 8th International Conference on Numerical Methods in Thermal Problems (Swansea, UK, July 1993), Numerical Methods in Thermal Problems, Vol. VIII, (ed. R. W. Lewis), Pineridge Press, Swansea, UK, 1993, Part 1, 361-375.; The areas of integration between the numerical simulation of castings and artificial intelligence (AI) techniques are discussed at the pre-processing stage. The major areas of possible integration which are identified are firstly, the interfacial boundary conditions and secondly, in the determination of density points in the mesh generation. It has been observed experimentally that for pure aluminium castings, depending upon the various process, material and geometrical parameters, the interfacial heat transfer coefficient can vary in the range of 2000 - 16000 W/m²K. A scheme based on heuristics is discussed for the quantitative estimation of the interfacial heat transfer coefficient values with the simultaneous consideration of various influencing parameters. Also, the scope of AI techniques in the mesh generation for thermal problems has been reviewed.
ME90a: Yao Zheng, On the J Integral for Regional Heterogeneous Welded Joints with Cracks (in Chinese), Transactions of the China Welding Institution, Vol. 11, No. 4, 245-250 (1990).; Proposing a counter example, it is proved that J integral is not conservative in regional heterogeneous media. Noticing the discontinuity of stress and strain components somewhere, J* integral is presented to modify J integral. The path-independence and physical meaning of the J* integral, and the energy expression J*=-(1/B)(dU/da) are verified simply. The concept and the constitution approach of interface elements are put forward for regional heterogeneous media in elastoplastic FEM analysis.
ME00a: Shyy Woei Chang, Lo May Su, Yao Zheng, Reciprocating Impingement Jet Heat Transfer with Surface Ribs, Experimental Heat Transfer, Vol. 13, No. 4, 275-297 (2000).; This article presents the experimental heat transfer results of an impinging jet onto a flat surface with discrete ribs in a reciprocating confinement. The test flows were systemically varied from static to reciprocating conditions with oscillating frequencies of 0.83, 1.25, and 1.67 Hz. Parametric ranges of tests in terms of Reynolds, pulsating, and buoyancy numbers were 10,000-25,000, 0-0.15, and 0-4.12x10^-7, respectively. It was found that the nonreciprocating heat transfer close to and away from the stagnation point was respectively reduced and improved from the smooth-walled values, which led to the more spatially uniform heat transfer distribution. An empirical correlation was developed to permit the evaluation of nonreciprocating local Nusselt numbers. Under reciprocating environment with relatively weak pulsating force effects, a tendency of heat transfer deterioration from static reference developed, which trend could lead to about 20% of heat transfer reduction. Further increase of pulsating force ratio caused the subsequent heat transfer recovery, and the local reciprocating Nusselt number could be enhanced to a level about 240% of the equivalent static value at a pulsating number of 0.014. Considerable influence of reciprocating buoyancy interaction on heat transfer was detected to impede local heat transfer. As the present flow system in a reciprocating confinement could result in higher and more spatially uniform heat transfer rates in general, it could be an applicable cooling method for pistons.
ME02a: Shyy Woei Chang, Yao Zheng, Enhanced Heat Transfer with Swirl Duct under Rolling and Pitching Environment, Journal of Ship Research, Vol. 46, No. 3, 149-166 (2002).; A detailed experimental investigation of heat transfer in a square duct fitted with twisted tape under a rolling and pitching environment is described, with particular reference to the heat transfer augmentation of shipping machinery. This study focuses on the development of an experimental procedure and methods for data processing, the parametric analysis and a selection of measurements that illustrate the manner by which the swinging forces and buoyancy interactively affect the local heat transfer. The swinging Coriolis force and buoyancy influence to a considerable extent the forced convection heat transfer in the swirl duct. Although enhancing the buoyancy level increases the heat transfer as the swirl duct rolls or pitches, the swinging Nusselt number is initially reduced relative to the stationary condition at the weak swinging oscillation, but tends to recover as the swinging force increases. The synergistic effects of harmonic and nonharmonic rolling and pitching oscillations reduce the heat transfer. Hot spots could develop in a swirl duct due to the slow rolling and/or pitching motions if the effect of the swinging oscillations on the heat transfer is not adequately considered. An empirical correlation has been developed for both single-axis and compound swinging conditions which permits the interactive effect of swinging Coriolis and buoyancy forces on forced convection to be quantified and which provides an evaluation of the local heat transfer in a swinging swirl duct.

Aerospace Engineering (Computational Fluid Dynamics; Propulsion Systems; Turbomachinery)

AE99a: Yao Zheng, Meng-Sing Liou, Kestutis C. Civinskas, Development of Three-Dimensional DRAGON Grid Technology, NASA Technical Memorandum, NASA TM---1999-209458, NASA, USA, November 1999, (41 Pages).; For a typical three dimensional flow in a practical engineering device, the time spent in grid generation can take 70% of the total analysis effort, resulting in a serious bottleneck in the design/analysis cycle. The present research attempts to develop a procedure that can considerably reduce the grid generation effort.; The DRAGON grid, as a hybrid grid, is created by means of a Direct Replacement of Arbitrary Grid Overlapping by Nonstructured grid. The DRAGON grid scheme is an adaptation to the Chimera thinking. The Chimera grid is a composite structured grid, composing a set of overlapped structured grids, which are independently generated and body-fitted. The grid is of high quality and amenable for efficient solution schemes. However, the interpolation used in the overlapped region between grids introduces error, especially when a sharp-gradient region is encountered. The DRAGON grid scheme is capable of completely eliminating the interpolation and preserving the conservation property. It maximizes the advantages of the Chimera scheme and adapts the strengths of the unstructured grid while at the same time keeping its weaknesses minimal.; In the present paper, we describe the progress towards extending the DRAGON grid technology into three dimensions. Essential and programming aspects of the extension, and new challenges for the three-dimensional cases, are addressed.
[Pictures: DRAGON Grids] [Link to download the paper]
AE00a: Yao Zheng, Meng-Sing Liou, Three-Dimensional DRAGON Grid Methodology: an Approach of Hybrid Grid Schemes, Presented at the 4th Asian Computational Fluid Dynamics Conference (Mianyang, Sichuan, China, September, 2000), Proceedings of the 4th Asian Computational Fluid Dynamics Conference, H. Zhang, ed., University of Electronic Science and Technology of China Press, Sichuan, China, 2000, 523-529, (ISBN 7-81065-470-5/Z.9).; The DRAGON grid, as a hybrid grid, is created by means of a Direct Replacement of Arbitrary Grid Overlapping by Nonstructured grid. The DRAGON grid scheme is an adaptation to the Chimera thinking, and is capable of completely eliminating the interpolation and preserving the conservation property. It maximizes the advantages of the Chimera scheme and adapts the strengths of the unstructured grid while at the same time keeping its weaknesses minimal. In the present paper, we describe the progress towards extending the DRAGON grid technology into three dimensions, and demonstrate the capability of generating computational grids and performing 3D flow calculations for multi-components complex configurations.
[Pictures: DRAGON Grids] [Pictures: Inviscid Flow around a Linear Cascade] [Pictures: Viscous Flow through an Annular Cascade]
AE01a: Yao Zheng, Meng-Sing Liou, Progress in the Three-Dimensional DRAGON Grid Scheme, To be presented at the 15th AIAA Computational Fluid Dynamics Conference (California, USA, June, 2001), 11 Pages, AIAA Paper 2001-2540.; We propose a novel approach of three-dimensional hybrid grid methodology, the DRAGON grid method in the three-dimensional space. The DRAGON grid is created by means of a Direct Replacement of Arbitrary Grid Overlapping by Nonstructured grid, and is structured-grid dominated with unstructured grids in small regions. The DRAGON grid scheme is an adaptation to the Chimera thinking. It is capable of preserving the advantageous features of both the structured and unstructured grids, and eliminates/minimizes their shortcomings. In the present paper, we address progress in the development and applications of the three-dimensional DRAGON grid scheme.
AE02a: Meng-Sing Liou, Yao Zheng, A Flow Solver for Three-Dimensional DRAGON Grids, NASA Technical Memorandum, NASA TM---2002-211512, NASA, USA, May 2002, (48 Pages).; DRAGONFLOW is a flow solver devoted to the Computational Fluid Dynamics (CFD) simulation using the three-dimensional DRAGON grid technology. DRAGONFLOW is a program suite adopted and redesigned from two existing successful flow solvers OVERFLOW and USM3D. OVERFLOW is a Navier-Stokes code working with Chimera grid, and is used here to solve flow problems on the domain occupied by composite structured grids of a DRAGON grid. USM3D is characteristic-based scheme for steady solutions to the Euler/Navier-Stokes equations on unstructured tetrahedral grid, and is employed to pursue flow simulation over a collection of unstructured grids of a DRAGON grid.; DRAGON grid is contructed to be a combination of a Chimera grid and a collection of unstructured grids. In the DRAGONFLOW suite, both OVERFLOW and USM3D are presented in form of module libraries, and a master module controls the invoking of these individual modules. The alternating invoking of these solvers in each time step, and the immediate data exchange on the DRAGON grid interfaces, leads to a seamless coupling of these two solvers. This report includes essential aspects, programming structures, benchmark tests and numerical simulations.
[Pictures: 2D Supersonic Flow in a Symmetric Convergent Channel] [Pictures: 3D Supersonic Flow in a Convergent Duct] [Pictures: Subsonic Flow through a Wavy-Wall Duct] [Pictures: Inviscid Flow around a Linear Cascade] [Pictures: Viscous Flow through an Annular Cascade] [Link to download the paper]
AE03a: Yao Zheng, Meng-Sing Liou, A Novel Approach of Three-Dimensional Hybrid Grid Methodology: Part 1. Grid Generation, Computer Methods in Applied Mechanics and Engineering, Vol. 192, No. 37/38, 4147-4171 (2003).; We propose a novel approach of three-dimensional hybrid grid methodology, the DRAGON grid method in the three-dimensional space. The DRAGON grid is created by means of a Direct Replacement of Arbitrary Grid Overlapping by Nonstructured grid, and is structured-grid dominated with unstructured grids in small regions. The DRAGON grid scheme is an adaptation to the Chimera thinking. It is capable of preserving the advantageous features of both the structured and unstructured grids, and eliminates/minimizes their shortcomings. In the present paper, we describe essential and programming aspects, and challenges of the three-dimensional DRAGON grid method, with respect to grid generation. We demonstrate the capability of generating computational grids for multi-components complex configurations.
[Pictures: DRAGON Grids]
AE03b: Meng-Sing Liou, Yao Zheng, A Novel Approach of Three-Dimensional Hybrid Grid Methodology: Part 2. Flow Solution, Computer Methods in Applied Mechanics and Engineering, Vol. 192, No. 37/38, 4173-4193 (2003).; Following the previous paper of this series, which addresses the generation approach of three-dimensional DRAGON grids, we demonstrate the capability of effectively performing three-dimensional flow calculations for multi-components complex configurations. The flow solution is conducted by means of using a seamlessly integrated package made up of two well-validated NASA solvers, which are structured- and unstructured-grid codes, respectively.
[Pictures: 2D Supersonic Flow in a Symmetric Convergent Channel] [Pictures: 3D Supersonic Flow in a Convergent Duct] [Pictures: Subsonic Flow through a Wavy-Wall Duct] [Pictures: Inviscid Flow around a Linear Cascade] [Pictures: Viscous Flow through an Annular Cascade]
AE04a: Yao Zheng, Wenpu Zhang, Jifa Zhang, Principles and Design of a Platform for Parallel Simulation and Visualization (in Chinese), Research Advances in Computational Fluid Mechanics, Proceedings of the 12th Chinese National Symposium on Computational Fluid Mechanics (Xian, China, 2004), 702-707.
The present paper is to address common problems and challenges of large-scale computer simulation and visualization in CFD computation. Areas covered include parallel computation, three-dimensional mesh generation, enabling technologies for multidicipliary application simulations, parallel and distributed visualization, and numerical simutations of complex flow fields. Morever, the paper is to outline our on-going project aiming to study and develop a Platform for Parallel Simulation and Visualization (PPSV), which is oriented to CFD computation.
AE04b: Yao Zheng, Applications of Computing Technology in Aerospace Engineering (Keynote Lecture) (in Chinese), Proceedings of the First National Symposium on Mechanics Problems in Aerospace Fields (Sichuan, China, 2004), Vol. 2, 353-356.
Computing technology is exhibiting its increasing importance and great power in aerospace engi-neering. The present paper is to introduce research teams and computing resources, in relevant research organi-zations and manufacturers. Moreover, it is to address common problems and challenges of large-scale computer simulation and visualization in computational fluid dynamics. Areas covered include parallel computation, three-dimensional mesh generation, enabling technologies for multidicipliary application simulations, parallel and distributed visualization, and numerical simutations of complex flow fields. In a word, the paper is to stress the significance and values of large-scale high performance computing, and to emphasize potential importance and roles of high end computing technology in aerospace engineering, by means of giving examples of relevant organizations and computational technologies.
AE04c: Jian Yang, Yao Zheng, Weizhong Li, Direct Numerical Simulation of Micro-Fluids for MEMS with Particular Reference to Bioseparation (in Chinese), Proceedings of the 6th International Conference on Frontiers of Design and Manufacturing (Xian, China, 2004), (ed. Bingheng Lu), Science Press and Science Press USA, Beijing, 2004, 449-450 (ISBN 1-880132-95-8).
The micro-fluid characteristics for Micro-Electro-Mechanical Systems (MEMS) in Simulated Moving Beds (SMB) for bioseparation are simulated£¬by means of the Direct Simulation Monte-Carlo (DSMC) method with the Variable Hard Sphere£¨VHS£©molecular model and No Time Counter (NTC) collision scheme. The model geometry is a two-dimensional channel with constant height, and the channel is filled with microstructures of rectangular, circular and triangular sections, respectively. The micro-fluid characteristics and throughput are investigated in the flow regime ranging from free molecular to continuum.
AE04d: Jian Yang, Yao Zheng, Weizhong Li, Qingbiao Wu, A Study on Micro-Fluids for Bioseparation by Molecular Dynamics Simulation (in Chinese), Research Advances in Computational Fluid Mechanics, Proceedings of the 12th Chinese National Symposium on Computational Fluid Mechanics (Xian, China, 2004), 657-661.
For designing a novel structure for bioseparation, characteristics of micro-fluids in micro-channels are studied, by means of Molecular Dynamics simulation method. The biological molecular flows in nonequilibrium states and the effect of bioseparation in such a structure are presented. The results show that the method is fast and effective for predicting the geometry parameters of micro-channels and the effect of bioseparation, and it can be used effectively in development of new bioseparation reactors.

Nuclear Engineering (Nuclear Safety)

NPE9293a: Roland W. Lewis, Yao Zheng and David T. Gethin, An Adaptive Finite Element Model for the Behaviour of Uranium Hexafluoride Filled Container in a Fire, Nuclear Engineering and Design, Vol. 140, No. 2, 229-250 (1993).; A two-dimensional finite element approach using an adaptive meshing strategy has been used to model the thermal response of an Uranium Hexafluoride transport container under the conditions of the International Atomic Energy Agency (IAEA) fire test. The heat input has been treated as radiation from the surrounding fire with the absence of neglectable forced convection. The phase change and density variation characteristics of the Uranium Hexafluoride material have been rigorously included in the analysis. The effects of radiation in the ullage and convection in the liquid region were also incorporated into the calculations. The latent heat of melting was taken into account by means of the enthalpy method while the sublimation and vapourization influences were accounted for by the heat source method. The mechanism of solid core sinking was also included in the model with a remeshing technique being used to trace the solid/liquid interface and the liquid level.; The numerical results show that for standard fill procedures container pressurisation by hydraulic locking was unlikely to occur. However, the results indicate that the vapour pressure buildup in the container is significant and this coupled with the container temperature is likely to lead to a failure.
[Pictures: Numerical simulation of heat transfer]

Mechanics (Solid Mechanics; Structural Mechanics)

Me90a: Zu-pei Yuan, Yao Zheng, A Study on Yield and Flow of Orthotropic Materials, Applied Mathematics and Mechanics, Chinese Edition, Vol. 11, No. 3, 233-238 (1990); English Edition, Vol. 11, No. 3, 247-253 (1990).; On the assumption that the yield criterion of orthotropic materials is isomorphic with Huber-Mises Criterion of isotropic materials, we put forward a dimensionless stress yield criterion, and obtained the associated plastic flow law. Using experimental stress-strain curves in various simple stress states, generalized effective stress-strain formulae may be derived correspondingly in various forms.
Me90b: Zupei Yuan, Changhai Tian, Yao Zheng, Stress and Strain Fields near a Steady Growth Crack Tip in an Orthotropic Solid, (in Chinese), Chinese Journal of Applied Mechanics, Vol. 7, No. 4, 1-10 (1990).; By applying R. Hill yield criterion for orthotropic materials regarded as elastic perfectly-plastic, the foundation formulae of the steady growth crack of Mode I under the plane strain condition are deduced. On the assumption of incompressibility of the materials the relation of Poison ratios v₃₁ + v₃₂ = 1 is obtained, further it can be assumed that v₃₁ = G/(F+G) and v₃₂ = F/(F+G). Therefore, the problem can be solved analytically. The result shows that there is singularity of ln(A/r) for the strain field.
Me8689a: Yao Zheng, Tip Fields and Small-Scale Yielding Solution of a Mode III Static Crack in Orthotropic Elastic Perfectly-Plastic Materials (in Chinese), Acta Mechanica Sinica, Vol. 21, No. 3, 364-368 (1989).; In this paper, tip fields of a mode III static crack in orthotropic perfectly-plastic materials are presented by supposing the R. Hill's yield criterion. On the assumption of distortion energy yield criterion, a small-scale yielding solution in linear elastic perfectly-plastic materials is obtained by using affine transformation and complex function mapping, and the crack opening displacement is discussed as well.
Me88a: Yao Zheng, Zupei Yuan, The Mode-III Steadily-Expanded Crack Tip Field in Perfect Orthotropic Elastoplastic Material (in Chinese), Journal of Harbin Institute of Technology, No. 4, 15-23 (1988).; Based on R. Hill yield criterion, this paper studies all aspects of perfect orthotropic elastoplastic material from the starting point of the equation for the mode-III steadily-expanded crack. Then it works out the stress and strain expressions for each zone of the tip field of the crack, and gives formally the main terms of displacement, rln(R_o/r)² and rln(R_o/r).
Me00a: Yao Zheng, Shyy Woei Chang, Zupei Yuan, Path-Independent Integral for Heterogeneous Media with Respect to Field Discontinuities, Computational Materials Science, Vol. 18, No. 2, 212-224 (2000).; By means of counter-evidence, it is proved that the original J integral does not satisfy the conservation law for general heterogeneous media. In the present paper, a modified version J* is re-proposed, which is a path-independent integral. The modifier term is related to stress and strain discontinuities occurring in material interfaces, and possibly occurring in interfaces between elastic and plastic zones. The integral J* can be interpreted as an expression of energy release rate, therefore, there exists an integral fracture criterion correspondingly. With regard to computational aspects related to finite element analysis, interface elements have been proposed to deal with stress and strain discontinuities in the material interfaces. For a generic case, adaptive analysis is recommended to take into account the discontinuities in the material interfaces, and possible discontinuities in the interfaces between elastic and plastic zones around a crack tip, in an optimal manner.

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