125 research outputs found

    Animation prototyping of formal specifications

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    At the present time one of the key issues relating to the design of real-time systems is the specification of software requirements. It is now clear that specification correctness is an essential factor for the design and implementation of high quality software. As a result considerable emphasis is placed on producing specifications which are not only correct, but provably so. This has led to the application of mathematically-based formal specification techniques in the software life-cycle model. Unfortunately, experience in safety-critical systems has shown that specification correctness is not, in itself, sufficient. Such specifications must also be comprehensible to all involved in the system development. The topic of this thesis—Animation Prototyping—is a methodology devised to make such specifications understandable and usable. Its primary objective is to demonstrate key properties of formal specifications to non-software specialists. This it does through the use of computer-animated pictures which respond to the dictates of the formal specification. [Continues.

    Development of a standard framework for manufacturing simulators

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    Discrete event simulation is now a well established modelling and experimental technique for the analysis of manufacturing systems. Since it was first employed as a technique, much of the research and commercial developments in the field have been concerned with improving the considerable task of model specification in order to improve productivity and reduce the level of modelling and programming expertise required. The main areas of research have been the development of modelling structures to bring modularity in program development, incorporating such structures in simulation software systems which would alleviate some of the programming burden, and the use of automatic programming systems to develop interfaces that would raise the model specification to a higher level of abstraction. A more recent development in the field has been the advent of a new generation of software, often referred to as manufacturing simulators, which have incorporated extensive manufacturing system domain knowledge in the model specification interface. Many manufacturing simulators are now commercially available, but their development has not been based on any common standard. This is evident in the differences that exist between their interfaces, internal data representation methods and modelling capabilities. The lack of a standard makes it impossible to reuse any part of a model when a user finds it necessary to move from one simulator to another. In such cases, not only a new modelling language has to be learnt but also the complete model has to be developed again requiring considerable time and effort. The motivation for the research was the need for the development of a standard that is necessary to improve reusability of models and is the first step towards interchangability of such models. A standard framework for manufacturing simulators has been developed. It consists of a data model that is independent of any simulator, and a translation module for converting model specification data into the internal data representation of manufacturing simulators; the translators are application specific, but the methodology is common and illustrated for three popular simulators. The data model provides for a minimum common model data specification which is based on an extensive analysis of existing simulators. It uses dialogues for interface and the frame knowledge representation method for modular storage of data. The translation methodology uses production rules for data mapping

    NASA/ASEE Summer Faculty Fellowship Program, 1990, Volume 1

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    The 1990 Johnson Space Center (JSC) NASA/American Society for Engineering Education (ASEE) Summer Faculty Fellowship Program was conducted by the University of Houston-University Park and JSC. A compilation of the final reports on the research projects are presented. The topics covered include: the Space Station; the Space Shuttle; exobiology; cell biology; culture techniques; control systems design; laser induced fluorescence; spacecraft reliability analysis; reduced gravity; biotechnology; microgravity applications; regenerative life support systems; imaging techniques; cardiovascular system; physiological effects; extravehicular mobility units; mathematical models; bioreactors; computerized simulation; microgravity simulation; and dynamic structural analysis

    User interfaces and discrete event simulation models.

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    A user interface is critical to the success of any computer-based system. Numerous studies have shown that interface design has a significant influence on factors such as learning time, performance speed, error rates, and user satisfaction. Computer-based simulation modelling is one of the domains that is particularly demanding in terms of user interfaces. It is also an area that often pioneers new technologies that are not necessarily previously researched in terms of human-computer interaction. The dissertation describes research into user interfaces for discrete event simulation. Issues that influence the 'usability' of such systems are examined. Several representative systems were investigated in order to generate some general assumptions with respect to those characteristics of user interfaces employed in simulation systems. A case study was carried out to gain practical experience and to identify possible problems that can be encountered in user interface development. There is a need for simulation systems that can support the developments of simulation models in many domains, which are not supported by contemporary simulation software. Many user interface deficiencies are discovered and reported. On the basis of findings in this research, proposals are made on how user interfaces for simulation systems can be enhanced to match better the needs specific to the domain of simulation modelling, and on how better to support users in simulation model developments. Such improvements in user interfaces that better support users in simulation model developments could achieve a reduction in the amount of time needed to learn simulation systems, support retention of learned concepts over time, reduce the number of errors during interaction, reduce the amount of time and effort needed for model development, and provide greater user satisfaction

    SIMULATION OF A MULTIPROCESSOR COMPUTER SYSTEM

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    The introduction of computers and software engineering in telephone switching systems has dictated the need for powerful design aids for such complex systems. Among these design aids simulators - real-time environment simulators and flat-level simulators - have been found particularly useful in stored program controlled switching systems design and evaluation. However, both types of simulators suffer from certain disadvantages. An alternative methodology to the simulation of stored program controlled switching systems is proposed in this research. The methodology is based on the development of a process-based multilevel hierarchically structured software simulator. This methodology eliminates the disadvantages of environment and flat-level simulators. It enables the modelling of the system in a 1 to 1 transformation process retaining the sub-systems interfaces and, hence, making it easier to see the resemblance between the model and modelled system and to incorporate design modifications and/or additions in the simulator. This methodology has been applied in building a simulation package for the System X family of exchanges. The Processor Utility Sub-system used to control the exchanges is first simulated, verified and validated. The application sub-systems models are then added one level higher_, resulting in an open-ended simulator having sub-systems models at different levels of detail and capable of simulating any member of the System X family of exchanges. The viability of the methodology is demonstrated by conducting experiments to tune the real-time operating system and by simulating a particular exchange - The Digital Main Network Switching Centre - in order to determine its performance characteristics.The General Electric Company Ltd, GEC Hirst Research Cent, Wemble

    Formalising the description of process based simulation models

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    Systems model for dynamic human error during accident sequences

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    Statement of responsibility on title page reads: Y. Huang, N. Siu, D. Lanning, J. Carroll, and V. Dang"December 1991."Includes bibliographical references (pages 153-155)Final report: "A systems model for dynamic human error during accident sequences"This report describes a systems-based operating crew model designed to simulate the behavior of an nuclear power plant control room crew during an accident scenario. This model can lead to an improved treatment of potential operator-induced multiple failures, since it deals directly with the causal factors underlying individual and group behavior. It is intended that the model, or more advanced developments of the model, will be used in the human reliability analysis portion of a probabilistic risk assessment study, where careful treatment of multiple, dependent failures is required. The model treats the members of the control room crew as separate, reasoning entities. These entities receive information from the plant and each other, process that information, perform actions that affect the plant, and provide information to the other crew members.The information retrieval, processing, and output activities are affected by the characteristics of the individual operator (e.g., his technical ability) and his relationship (measured in terms of "confidence level") with his fellow operators. Group behavior is modeled as the implicit result of individual operator behavior and the interactions between operators. The model is applied towards the analysis of steam generator tube rupture (SGTR) accidents at a non-U.S. pressurized water reactor, using the SIMSCRIPT 11.5 programming language. Benchmark runs, comparing the model predictions with videotaped observations of the performances of three different crews during SGTR training exercises, are performed to tune a small number of model parameters. The tuned model is then applied in a blind test analysis of a fourth crew. In both the benchmarking and blind test runs, the model performs quite well in predicting the occurrence, ordering, and timing of key events.The model is also employed in a number of sensitivity analyses that demonstrate the robustness of the model (it generates plausible results even when the model parameters are assigned values not representative of observed crews) and the model's usefulness in investigating key issues (e.g., the effect of stress buildup on crew performance). iSupported by the Office of Nuclear Regulatory Research, United States Nuclear Regulatory Commission: NRC-04-89-35

    Communication Processes in the Design and Implementation of Models, Simulations and Simulation-Games: A Selective Review and Analysis, From the Vantage Point of Computerized Conferencing

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    Computerized conferencing is a new form of communication which permits a group of individuals, who could be separated in time as well as space, to engage in an interactive dialogue with each other through the convenience of their computer terminals. The software for a computerized conferencing system is designed to keep track of all messages communicated in the system, as well as insure that the various protocols for communication are observed by all. Our objectives in this report are to examine the communication processes found in the design and implementation of models, simulations and simulation-games, and to identify those areas where computerized conferencing, as a new form of communication, has the potential to impart a significant impact on the aforementioned disciplines. The theme which underlies this report is that computerized conferencing presents us with the capability to structure a communication process to satisfy a set of preformulated design objectives. In Part I, we introduce the reader to some basic terminology used to identify models, simulations and simulation-games. Part II attempts to enumerate the potential impacts computerized conferencing is expected to have on the model building process. A key component of this section is the author\u27s causal-loop model of the modeling process which seeks to capture the feedback relationships responsible for both the growth processes and limitations inherent in modeling, and the key role computerized conferencing is expected to play. Our attention next turns to the area of simulation-games. In Part III, we define a simulation-game as a gestalt communication process, and reiterate many of Richard Duke\u27s thoughts on the communication processes found in simulating-games. The next chapter examines the marriage of computerized conferencing and simulation-games, and identifies the numerous benefits to be achieved by this union. These benefits include not only logistic breakthroughs and the attainment of new degrees of verisimilitude to the object human interaction systems being modeled, but an opening up of the simulation-game as a research tool to gain theoretical insight into the sociological processes that take place in human interaction systems. In Part V, we present to the reader summaries of those major efforts relating to conferencing based simulation-games. These include the work of Lincoln Bloomfield and his associates at MIT (the CONEX simulation-games), the Polis system of R. Noel at the University of California at Santa Barbara, and the experiments conducted by the Institute for the Future with the CRISIS simulation-game. In Part VI, we explicity prescribe some methodologies by which a simulation-game designer can structure the communication processes found in simulation-games to satisfy certain design objectives. We refer to this as a constrained computerized conference (i.e., dynamic constraints are imposed on the communication process). A mathematical model is developed for the communication that takes place in the simulation-game. Design applications are then discussed as specific extensions of the mathematical model. The penultimate chapter presents a hypothetical language for describing the communication processes found in simulation-games and other group communication models. The language begins with the world view of SIMSCRIPT 11-5, acknowledged to be the most powerful discrete event simulation language, and builds in some powerful features designed to model and structure human communication processes. The language is illustrated with both a university fiscal crisis simulation-game and the SYNCON communication model. The final chapter synthesizes the ideas expressed in the preceding chapters by an analogy of models, simulations and simulation-games with the conceptual foundations of the scientific method, and sees computerized conferencing as a key aspect in making scientists out of systems scientists. It calls for a conferencing-based International Archives of models, simulations and simulation-games, both to aid in model scrutinization and confirmation as well as to provide a mutual pooling of resources from which users can draw as they please

    Simulation Modeling of Prehospital Trauma Care

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    Prehospital emergency care systems are complex and do not necessarily respond predictably to changes in management. A combined discrete-continuous simulation model focusing on trauma care was designed and implemented in SIMSCRIPT II.5 to allow prediction of the systems response to policy changes in terms of its effect on the system and on patient survival. The utility of the completed model was demonstrated by the results of experiments on triage and helicopter dispatching policies. Experiments on current and two alternate triage policies showed that helicopter utilization is significantly increased by more liberal triage to Level 1 trauma centers, which was expected, but that the waiting time for pending accidents tended to decrease, an unexpected consequence. Experiments on helicopter dispatch policy showed that liberalization of the dispatch policy would have much greater consequences than would changing the triage criteria. Again, this result was unexpected and has received little attention from system planners and administrators, especially with respect to the degree of discussion and controversy surrounding triage criteria

    Zero-gravity movement studies

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    The use of computer graphics to simulate the movement of articulated animals and mechanisms has a number of uses ranging over many fields. Human motion simulation systems can be useful in education, medicine, anatomy, physiology, and dance. In biomechanics, computer displays help to understand and analyze performance. Simulations can be used to help understand the effect of external or internal forces. Similarly, zero-gravity simulation systems should provide a means of designing and exploring the capabilities of hypothetical zero-gravity situations before actually carrying out such actions. The advantage of using a simulation of the motion is that one can experiment with variations of a maneuver before attempting to teach it to an individual. The zero-gravity motion simulation problem can be divided into two broad areas: human movement and behavior in zero-gravity, and simulation of articulated mechanisms
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