Abstract:LoD (level of detail) is one of the most important techniques in creating real-time rendering of virtual environment. As a special mesh model, terrain surface model has important and wide-ranged application background in virtual reality. In this paper, the authors present an algorithm for real-time LoD reduction and display of high-complexity terrain surface data. The algorithm allows the generation and computation of appropriate level of detail dynamically by using the compact and efficient regular grid representation. Through analysis of the special requirement for rendering virtual terrain surface, they combine size and focus criteria to estimate the importance of detail of terrain surface and provide a screen-space threshold to bound the maximum error of the projected image. Besides, the whole dataset is constructed into a hierarchy of block-based representations with their error bound precalculated. As a result, a coarse level of simplification could be firstly performed to choose discrete level of detail for the surface mesh, and further simplification is operated on individual mesh vertices within a block. The algorithm has been implemented for approximating and rendering digital terrain models and the experimental results show its high efficiency.

Abstract:The generation of assembly precedence constraint is the key step of assembly planning and the most difficult one as well. In this paper, the implementations of some methods of generation of assembly precedence constraint are presented at first. The advantages and disadvantages of these methods are discussed as well. Then, one method which combines the knowledge of geometry and assembly experience is presented. By using the method, the assembly knowledge base and database are established. Several feasible solutions are provided at the same time. Finally, a conclusion is reached. The advantages of the method and suggestions on further research are provided as well.

Abstract:A systematic software development method named “Model-oriented Transformational Software Development Method” is proposed in this paper. In this method, data abstraction is enhanced to language abstraction; the specifying of some specific software is abstracted to language specifying; the implementation of the software becomes language reducing (transformation); the process of software development here could be described as “specification+transformation”. Following these ideas, a mechanism to abstract and encapsulate languages named Garment is designed. Relationships between languages, which are classified as inheritance, shielding and extension, are described with Garment. Taking a language knowledge base as its kernel, an environment named Garden (Garment development environment) is implemented to supports system development with Garment. Finally, the system structure of Garden and some development cases are described.

Abstract:The problem of polyhedron contact is concerned about in this paper. Based on geometric features of polyhedron, a method to speed up the contact of polyhedrons by translating the problem of polyhedron contact into the problem of calculating distance among a small number of points and polygons is presented. The algorithm presented here can be widely used in the fields of Graphics, Robot, Multimedia and CAD/CAM etc.

Abstract:MQI (multi-database query interface) is a client tool which the authors developed for querying with SQL on several different RDBMS (relational database management system) data sources. Its logical architecture and algorithm design are mainly discussed in this paper.

Abstract:PDAW (personal digital assistant window) is a window system specially used in PDA (personal digital assistant). Its most outstanding characteristic is that it can support developing application program with adaptive user interface. Adaptive user interface has many different types. Because PDAW provides merely mechanism supporting adaptive but rule and status deciding adaptive strategy, it does not limit the type of adaptive user interface. PDAW consists of interface look, window kernel, device interface and programming interface. Mechanism supporting adaptive is implemented in the window kernel.

Abstract:The optimal design of gear parameters in the movements of clocks and watches is a combinatorial optimization problem, which is too difficult to be solved optimally using traditional optimization methods. The GA(genetic algorithm) is a natural evolution-based heuristic searching method, which was recently introduced and has been successfully applied to a variety of problems. The difficulties in using this algorithm are how a particular problem is to be modeled to fit into the genetic algorithm framework, and how the operators (selection, crossover, mutation) work due to the code strings. The indexes of various gear parameters of transmission is presented in this paper as a string, and the optimal design of gear parameters is successfully solved. This method can be also applied to general mechanical designs. Through comparison, it can be seen that the parameters calculated in the GA are better than those in the expert system.

Abstract:In this paper, a method of fast searching I pictures in MPEG-2 system stream using long step and short step is presented. The method achieves higher speed performance comparing with the byte by byte searching method, and is applied in the design of the functions of MPEG-2 players, such as fast forward, fast backward and play backward. The implementation of these functions is described in detail. Moreover, this method can also be applied in VBR (variable bit rate) MPEG system stream, which is proposed based on CBR (constant bit rate) stream.

Abstract:The ODL (object description language) is one of the kernel parts of SCOP (software construction=object+process control) component software. Being language-neutral, ODL separate class specification form body implementation. Furthermore, with the help of the SCOP Object Management System (OMS), object class and their services could be shared across computers. That is, details about server location, the choice of implementation language and algorithm are transparent to programmers. The ODL compiler brings all such transparency into reality. Using C language as the target, the generated code is very portable. The authors outline the design of the ODL compiler and some key issues in implementing the compiler in this paper, including dynamic binding, auto-linking, quick-instantiation of template, language-mapping and implementation-skeleton etc.

Abstract:In this paper, a method to model the security semantic in object-oriented database system is presented. The method is based on multilevel data model, and defines several kinds of security constraint. A kind of diagram to illustrate application's security model is also introduced in this paper.

Abstract:In this paper, the checkpointing & rollback mechanism is studied deeply, and a new approach for SFT (software fault tolerance) is presented, which is based on the DFA (data flow analysis). The authors introduce the SFT technology at first, and point out that the peculiarity of data is the ultimate reason and also the final result of the software faults in control systems, so it is very necessary to adopt a powerful measure for data fault tolerance. Then, they discuss the applications of the DFA technique in the SFT in details, and give two theorems, one is for the minimal sufficient rollback point and another is for the checkpoint data set. Besides, they give the sufficient condition for the validation of the definition of a rollback block. They also use the telecommunication system as an example to illustrate the usage of this method. It is shown that only two checkpoints are needed to be maintained dynamically in their solution. The method presented in this paper can be used widely by extending simply.

Abstract:Some principles of layering and separation in the design of telecommunication software are introduced in this paper. By way of layering and separation, the complexity of telecommunication software can be reduced. Further more, the software architecture can be more clear, adaptive and easy to understand. They are a great help to the telecommunication software developers.

Abstract:In this paper, temporal problems and temporal relationships among multimedia dataflow are introduced, then related research is analyzed. Integrating with a multimedia data model, a synchronization model based on PETRI net is presented to represent temporal relationships among multimedia data. According to these two models, corresponding data structure is built and an algorithm for multimedia data retrieval is proposed.

Abstract:In this paper, a structural design of the knowledge network for the identification and classification fault diagnosis model is introduced together with the detailed reasoning algorithm and fault diagnosis algorithm. Reasoning with uncertainty is realized through the message propagation among the nodes, which makes it have the characteristic of a distributed system. In addition, the machine learning algorithm for the judgement function is also presented. This algorithm adopts the package wrapping algorithm to select the border points sets, which makes the speed of curve approach more quickly.