On the effective generation of set elements within specified ranges

A recursive functiong is augmenting ifg(n) n for alln. Ag-constructor for a setA is a Turing machine that on inputn outputs some element ofA betweenn andg(n), inclusive, if such an element exists. Ag-generator forA outputs all elements ofA betweenn andg(n). Ag-detector merely determines whether there exist any elements in the given range. Total constructors (generators, detectors) always halt, and indicate whether or not any elements exist in the set in the given range; partial machines need not halt in the event that no such elements exist.We characterize the classes of sets having each of these types of machines. We also establish that the problems of determining, for a given recursively enumerable setA and augmenting functiong, whetherA has a total or partialg-generator or a totalg-constructor or detector are all ₃-complete; and we determine, for fixedg, the relationships among the classes of sets having these different types of machines.Part of this work was done while the author was an AT&T Bell Labs Scholar at the Computer Science Department of the University of Rochester.     

Automated test case generation for programs specified by relationalalgebra queries

Black-box software testing requires test cases to be generated from specifications alone. However, it is impossible to automate the process completely for arbitrary specifications. Specifications are thus restricted to being written entirely in terms of relational algebra expressions. An automated test case generation method is developed for such specifications     

推进器饱和/故障下的无人艇固定时间指定性能容错控制

针对系统动态未知的无人艇(USV)在推进器故障与饱和约束下轨迹跟踪问题,本文提出一种基于固定时间扩张状态观测器的积分滑模容错控制方法.首先,构造固定时间扩张状态观测器,实现未知速度信息、集总未知非线性的准确估计.进而,通过引入一种新型设定时间性能函数,约束位姿跟踪误差,并利用误差转换函数将其转化为无约束误差动态系统.在此基础上,结合固定时间积分滑动模态与饱和补偿动态系统,设计固定时间控制策略,保证系统实际固定时间稳定且位姿跟踪误差严格位于指定范围内.最后,仿真验证所提出控制方法的有效性与优越性.     

Semantics of OCL specified with QVT

The Object Constraint Language (OCL) has been for many years formalized both in its syntax and semantics in the language standard. While the official definition of OCL’s syntax is already widely accepted and strictly supported by most OCL tools, there is no such agreement on OCL’s semantics, yet. In this paper, we propose an approach based on metamodeling and model transformations for formalizing the semantics of OCL. Similarly to OCL’s official semantics, our semantics formalizes the semantic domain of OCL, i.e. the possible values to which OCL expressions can evaluate, by a metamodel. Contrary to OCL’s official semantics, the evaluation of OCL expressions is formalized in our approach by model transformations written in QVT. Thanks to the chosen format, our semantics definition for OCL can be automatically transformed into a tool, which evaluates OCL expressions in a given context. Our work on the formalization of OCL’s semantics resulted also in the identification and better understanding of important semantic concepts, on which OCL relies. These insights are of great help when OCL has to be tailored as a constraint language of a given DSL. We show on an example, how the semantics of OCL has to be redefined in order to become a constraint language in a database domain.

Tool path generation for a surface model with defects

A 3-axis tool path generation algorithm for free-form surface models including defects, such as gaps and overlaps is presented in this paper. To avoid the difficulty of computing a complete cutter location (CL)-surface, the proposed approach generates a tool path by slicing CL-elements instead of a complete CL-surface. A key feature of the proposed approach is that it reduces the number of CL-elements to be sliced by utilizing the correspondence information between CL-elements and cutter contact (CC)-elements. This feature significantly improves the computational efficiency of the proposed algorithm. Empirical tests show that the proposed approach is robust to geometric defects of CAD models, gaps and overlaps, with a near O(n) time complexity, where n is the number of slicing planes.     

Constraint satisfaction with succinctly specified relations

The general intractability of the constraint satisfaction problem (CSP) has motivated the study of the complexity of restricted cases of this problem. Thus far, the literature has primarily considered the formulation of the CSP where constraint relations are given explicitly. We initiate the systematic study of CSP complexity with succinctly specified constraint relations.     

Parallel generation of unstructured surface grids

In this paper, a new grid generation system is presented for the parallel generation of unstructured triangular surface grids. The object-oriented design and implementation of the system, the internal components and the parallel meshing process itself are described. Initially in a rasterisation stage, the geometry to be meshed is analysed and a smooth distribution of local element sizes in 3-D space is set up automatically and stored in a Cartesian mesh. This background mesh is used by the advancing front surface mesher as spacing definition for the triangle generation. Both the rasterisation and the meshing are MPI-parallelised. The underlying principles and strategies will be outlined together with the advantages and limitations of the approach. The paper will be concluded with examples demonstrating the capabilities of the presented approach.

The application of surface visibility and moldability to parting line generation

In molding, casting or forging processes, part surfaces are formed by the core, cavity and local tools in molding/casting or by the upper and lower dies and local tools in forging. In computer-aided design of dies and molds, automatic identification of surfaces molded/formed by these different tooling components is critical since the generation of parting lines depends on these surfaces, which would further influence the determination of parting surfaces, the creation of core and cavity blocks and the entire mold structure. In this paper, the surface partability and visibility are first proposed and its moldability is next presented. Considering the molding process as an instance, the concepts of core-, cavity- and the local tool-molded surfaces are defined. A methodology based on surface visibility and moldability to determine the potentially and actually moldable surfaces of these groups is developed. Since the generation of parting lines is a crucial preliminary design step in mold/die design life cycle, a new approach to determining the parting lines based on the proposed methodology is presented. A case study is used to test the methodology and approach, and to validate the efficiency in parting line generation of molded parts.     

PDE surface generation with combined closed and non-closed form solutions

Partial differential equations (PDEs) combined with suitably chosen boundary conditions are effective in creating free form surfaces. In this paper, a fourth order partial differential equation and boundary conditions up to tangential continuity are introduced. The general solution is divided into a closed form solution and a non-closed form one leading to a mixed solution to the PDE. The obtained solution is applied to a number of surface modelling examples including glass shape design, vase surface creation and arbitrary surface representation.     

Smooth anisotropic sources with application to three-dimensional surface mesh generation

Isotropic sources are extended to take anisotropy into account in order to obtain a smooth anisotropic sizing field for anisotropic mesh generation. Different types of anisotropic sources are described to represent boundary layers on surfaces and in volume that guarantee a smooth anisotropic field. This allows to us resolve multiple boundary layer intersections properly and naturally provides a smooth transition between the anisotropic boundary layer sizing and the isotropic region. Furthermore, the interaction between a smooth anisotropic sizing field and curvature is studied, and estimates of the tangential size spacing are provided for first and second order approximation of the geometry to ensure smoothness of the sizing field. It is also shown that, in order to get a smooth size variation, volumetric and surface meshing can not be decoupled. The filtering of the sources in order to obtain a computationally efficient method is described. Numerical examples demonstrate our method.     

Model following controller with specified sensitivity function

A design method for a model-following servo control system whose output sensitivity function is specified with a reference model is presented. Using this method, the plant output responses to reference input change and the output sensitivity function can be specified separately and directly     

Second order stochastic simulation with specified correlation

A previously reported procedure for the simulation of normal stochastic processes using a combination of linear segments is extended by the use of non-linear second order curves, for which the second derivative process has known correlation function. The correlation function of the simulated process is deduced as a function of specified parameters, which are then determined to fit (by least squares optimisation) a given correlation function. Accuracy of fit is improved in comparison with the linear simulation. The sum of the resulting quadratic curves through sets of three random points is then the simulated process. Individual points in the process can be simulated without the need to store the whole process and as process parameters are determined prior to simulation the procedure is fast. These features render it suitable for use on microcomputers and for the simulation of large numbers of processes, for example, to simulate outcrossing statistics for vector processes in reliability and quality and process control theory.     

On the design of observers with specified eigenvalues

This correspondence considers the problem of designing an observer with specified distinct eigenvalues to estimate a set of linear state functionals for a linear multivariable system. The conditions given for the design of anrth-order observer, wherer leq nu_{0} - 1(ν0is the observability index), represent an extension of the results of Murdoch [3] and Fortmann and Williamson [2]. The conditions are based on the assumption that the observer eigenvalues are distinct from those of the plant.     

The statistics of state-spaces

The state-space model is a general, powerful, and elegant representation of problem solving. Nevertheless, state-spaces have rarely been used to model realistic environments because conventional state-spaces are inherently deterministic, while the world is not. This paper extends the model toprobabilistic state-spaces (PSS), which elegantly capture many of the world's complexities by regarding state values as generated by random variables. These PSS models, when combined with decision analytic techniques for knowledge elicitation and encoding, should yield realistic representations. The first investigation of states based on random variables derived the expected-outcome model of two-player games, which led to some powerful results about game evaluators. Most of the work done on expected-outcome was quite general, and should extend easily beyond game-trees to arbitrary state-spaces. The second potential application domain, strategic planning for robot controllers in automated assembly plants, is currently under investigation.This research was supported in part by NSF grants IST-8513989 and IRI-8910173 and by the University of Southern California Faculty Research Initiation Fund.     

指定接收者的可公开验证签密方案

签密作为实现保密认证通信的一种新技术,具有高效的特点;然而,由于签密中被签密的消息在签名时同时也被加密,由此带来的公开验证问题是亟待解决的。基于密钥交换协议与HK签名方案,提出了一个带指定接收者的可公开验证签密方案。在该方案中,发送方可经由签密者为指定用户生成给定消息的签密密文,在遗嘱协议等的应用中有着积极意义。     

Programming with partially specified aggregates in Java

Various forms of data aggregates, e.g., arrays, lists, sets, etc., are usually provided by programming languages, either as primitive entities or as additional features made available by standard libraries. In conventional programming languages these data structures are usually specified by completely and precisely enumerating all their constituent elements. Conversely, in (constraint) logic programming languages it is common to deal with partially specified aggregates where either some elements or some parts of the aggregate are left unknown. In this paper we consider the case where partially specified aggregates can occur in a conventional O-O programming language. Specifically, we consider partially specified lists and sets as provided by the Java library JSetL. The definition of such data structures is strongly based on the notion of logical (or constrained) variable usually provided by languages and libraries to support constraint programming. We show through simple examples using Java and JSetL how partially specified lists and sets, along with a few basic constraints over them, can be conveniently exploited in a number of common programming problems.     

Construction of invariant polytopic sets with specified complexity

The problem of construction of controlled invariant polytopic sets with specified complexity, for linear systems subject to linear state and control constraints, is investigated. First, geometric conditions for the enlargement of a polytopic set by adding a new vertex, in order to produce a polytopic set of specified complexity, are established. Next, conditions for such an enlargement of controlled invariant sets to preserve the controlled invariance property are presented. The established theoretical results are used to develop methods for the construction of admissible controlled invariant sets with specified complexity. Two numerical examples show how these results can be used for the computation of monotonic sequences of admissible controlled invariant sets of specified complexity.     

NURBS边界曲面直接生成法

由于非均匀有理B样条(NURBS)曲面的复杂性,传统NURBS边界曲面的生成是先构造孔斯曲面,再由孔斯曲面向NURBS曲面转换得到,其操作过程比较烦琐。针对此问题,提出了NURBS边界曲面直接生成算法,该算法根据给定的四条NURBS边界曲线,结合孔斯曲面生成方法直接插值生成NURBS曲面,从而避免了通过孔斯曲面向NURBS曲面转换所带来的计算代价,因此同传统方法相比,具有较低的计算代价。实验结果表明:该算法简化了曲面生成步骤,减少了曲面转换过程的计算量,生成的曲面边界信息明确,且连续性好。