有限精度时间自动机的可达性检测

为了缓解状态空间爆炸问题,减小模型检测过程中生成的状态空间,加快模型检测速度,引入有限精度时间自动机(finite precision timed automata,简称FPTA)作为实时系统的形式模型,并提出了一种数据结构SDS(series of delay sequence)符号化表示状态空间中的状态集.FPTA只记录时钟变量的整数值及时钟变化的先后次序,从而减小生成的状态空间.在一定的时间约束下,Alur与Dill提出的时间自动机的可达性检测可简化为FPTA的可达性检测.举例描述了状态空间的生成过程和表示方法.最后,列出部分初步的实验结果,分析了SDS的特点及不足.     

Confocal surface profiling utilizing chromatic aberration

A new method for surface profiling in the confocal microscope utilizing chromatic aberration is presented. An expression for the integrated spectral intensity in the new profilometer is derived and chromatic aberration in the confocal microscope is explained. Estimates of the minimum resolvable depth and the maximum depth that can be profiled are given utilizing a ratiometric signal detection scheme. Examples of ratio images illustrating the new surface profiling technique are presented, showing the scheme to be both simple to implement and effective.     

A model management systems approach to manufacturing systems design

Manufacturing systems design involves the solution of a complex series of interrelated problems. This complexity will increase in the future as manufacturing practices change to meet increased global competition. Research within manufacturing systems design has mainly been focused on finding improved models for solving particular problems, or extending existing modeling techniques. This has resulted in numerous modeling tools being available to support manufacturing systems design. However, little research work has been carried out into consolidating the existing theories and models. As a result, a large body of this work has not been applied in industry.Model management has evolved as a research area which investigates methods for storing, modifying, and manipulating models. This article describes a prototype model management system for manufacturing systems design. The objective here is not to develop another decision support system for manufacturing design, but to illustrate, through the development of a prototype system, a number of key ideas of how concepts from the area of model management systems can be used to support manufacturing systems design. The prototype model management system utilizes the structured modeling framework and uses an extended version of the structured modeling language. An important aspect of the prototype model management system is the incorporation of the model development task, thus allowing the system to be easily updated and adapted. The prototype system was evaluated using a range of queueing network models for manufacturing systems design.     

The one-way quantum computer--a non-network model of quantum computation

A one-way quantum computer (QC _C ) works by performing a sequence of one-qubit measurements on a particular entangled multi-qubit state, the cluster state. No non-local operations are required in the process of computation. Any quantum logic network can be simulated on the QC _C . On the other hand, the network model of quantum computation cannot explain all ways of processing quantum information possible with the QC _C . In this paper, two examples of the non-network character of the QC _C are given. First, circuits in the Clifford group can be performed in a single time step. Second, the QC _C -realization of a particular circuit—the bit-reversal gate—has no network interpretation.     

Representation and extrapolation in multilayer perceptrons

To give an adequate explanation of cognition and perform certain practical tasks, connectionist systems must be able to extrapolate. This work explores the relationship between input representation and extrapolation, using simulations of multilayer perceptrons trained to model the identity function. It has been discovered that representation has a marked effect on extrapolation.     

Videoendoscopic diagnosis of esophageal motility disorders

PURPOSE: Looking for a valid, reliable, and feasible method to collect data on the performances of practicing family physicians, the authors compare the measurement characteristics of a multiple-station examination (MSE) using standardized patients with those of a video assessment of regular consultations in daily practice (practice video assessment, PVA). METHOD: In a cross-sectional study, consultations of 90 family physicians were videotaped both in an MSE and in their daily practices. Peer-observers used a validated instrument (MAAS-Global) to assess the physicians' communication with patients and their medical performances. The physicians were randomly divided into two groups, comparable for demographic characteristics, and half underwent the assessments in reverse order to test for time-order effects. Content validity, criterion validity, reliability, and feasibility of the two methods were compared. RESULTS: Content validity of the PVA was superior to that of the MSE, since the domain of general family practice care was better covered. Observed participants judged the videotaped practice consultations to be "natural," whereas hardly any family physician, after reviewing the videotaped consultations of the MSE, recognized his or her usual working style. Specific criteria made it possible to standardize real practice. Concerning criterion validity, only the medical-performance components of the two methods correlated. No correlation was found for the communication components. Real-practice performance proved to be less influenced by observation than was performance during the MSE. The reliabilities of the two methods, expected to be better in the controlled MSE, were comparable. The administration of the PVA was more flexible, less costly, and better accepted by the family physicians than was that of the MSE. CONCLUSION: Assessment for quality improvement of family physicians' practices by video observation in daily practice is superior to video assessment in a simulated setting using standardized patients.