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Simulation Conference, 1990. Proceedings., Winter

Date 9-12 Dec. 1990

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Displaying Results 1 - 25 of 160
  • Proving temporal properties of hybrid systems

    Page(s): 250 - 256
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    A formal technique, DMOD, for modeling hybrid systems is presented. It is based on utilizing intuitions about the causality relation, and the logic of definite clauses with the SLD-resolution proof procedure. An algorithm to simulate with DMOD models is presented. Then, a general framework in which temporal properties of hybrid systems can be formulated and proved (given that those systems are modeled using DMOD) is outlined. These ideas are illustrated by proving a liveness property about a railroad crossing.<> View full abstract»

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  • Simulating dedicated UNIX PC-based application systems

    Page(s): 831 - 838
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    An event-driven simulation model was developed to estimate the balance the hardware resources needed to support dedicated UNIX PC-based application systems. The authors describe the simulation approach, the software package developed, and the tool used to generate the model and collect data from it. Novel elements of this research include (1) simulation of software that reacts to changes in its external environment and (2) a methodology for using UNIX tools to estimate system characterization parameters. Results obtained using the model were validated by comparing them with data collected from an actual system.<> View full abstract»

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  • 1990 Winter Simulation Conference Proceedings (Cat. No.90CH2926-4)

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    Freely Available from IEEE
  • A simulation analysis of the effects of transportation system parameters on inventory levels

    Page(s): 908 - 910
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    The author describes the investigation of various aspects of operation of a combined truck/trailer-railroad transportation system. The system involves shipment of manufactured parts from Mexico through the United States and into Canada. The objectives were to investigate the effect of a number of variables in the transportation system upon inventory level at the Canadian distribution warehouse and to determine the minimum number of trailers required to operate the system without introducing delays which would cause the warehouse inventory to fall below a predetermined minimum level. The model is coded in GPSS/H. The author describes some of the design features of the model including the use of the BSTORAGE block in GPSS/H to implement the changing capacities for trailers on the railway trains used. The simulation of transportation system variables, such as border crossing delays, train delays or crashes, and national holidays in all three countries, is also described. A summary of the results of the various test runs of the model is given View full abstract»

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  • System performance analysis with an Ada process model development

    Page(s): 846 - 850
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    The Command Center Processing and Display System-Replacement (CCPDS-R) Performance Model (CPM) has enjoyed an expanded role in the CCPDS-R project. The performance model has influenced not only the system design, but also system allocations of resources. CCPDS-R performance analysis and requirements compliance insight have been substantially enhanced over the early phase of development. The CCPDS-R program has maximized the use of an ADPE performance model during all phases of a systems design. It also provided an approach for its use in concert with the Ada process model. With the effective use of the CPM and the Ada process model, one can maximize the efficiency of both efforts. The CPM is a complementary tool in the Ada process model for building a computer system which meets its requirements View full abstract»

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  • A new algorithm for stochastic optimization

    Page(s): 364 - 366
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    Classical stochastic optimization algorithms have severe problems associated with them: they converge extremely slowly on problems where the objective function is very flat, and they often diverge when the objective function is steep. The author has developed a stochastic optimization algorithm that is more robust than the older algorithms in that it is guaranteed to converge on a larger class of problems. This algorithm is guaranteed to converge even when the iterates are not assumed a priori to be bounded. This algorithm is also observed to converge faster on a significant class of problems. As the parameters can be chosen so that the new algorithm behaves very much like the older algorithms (except that it converges on a larger class of problems), this algorithm should always be used in preference to the older algorithms View full abstract»

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  • A time warp implementation of Sharks World

    Page(s): 199 - 203
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    The authors discuss the TWOS (Time Warp Operating System) implementations of the Shark's World simulation, a simple simulation of sharks and fish swimming through a toroidal world. Shark's World was coded and debugged in two man-weeks; after the initial debugging and tuning, it ran all tests without modifications. Shark's World provides a good performance under TWOS. It has demonstrated speedups as high as 29.5, with efficiencies as high as 63.75%. With a sufficient number of sectors, TWOS provides a smooth speedup curve. If the number of sectors is close to the number of nodes, the speedup curve is likely to have a plateau between the points of two objects per node and one object per node. Shark's World provides a test example for lazy cancellation versus aggressive cancellation. Due to its nature, lazy cancellation should do very well with Shark's World, and does indeed do better than aggressive cancellation. The authors examine methods of improving TWOS performance on this application, and the possible effects of adding more complexity to the simulation View full abstract»

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  • A framework for reusability using graph-based models

    Page(s): 472 - 476
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    A framework for developing and managing reusable simulation components using graph-based models (GBMs) is presented. Graph-based models can be defined as those models in which communications between submodel components are represented with a directed graph. A system architecture which readily supports this approach is presented, and an example application domain is outlined. The potential application domains for GBM are wide-spread. By allowing the modeler to define a reusable library containing behavioral characteristics of model components, this system has a much greater level of flexibility than similar commercial packages which provide the modeler with a standard set of components that are tailorable at best View full abstract»

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  • AI: what simulationists really need to know

    Page(s): 204 - 209
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    The authors discuss aspects of the application of artificial intelligence (AI) to simulation. The topics covered are: the place of AI techniques and an AI philosophy for simulation; expanding the bounds of simulation; what simulationists need to know about their problems; AI and simulation-some lessons learned; and AI contributions to simulation View full abstract»

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  • Experiences in developing an object-oriented modeling environment for manufacturing systems

    Page(s): 477 - 481
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    The authors describe the research efforts in the Center for Computer Integrated Manufacturing at the Oklahoma State University to develop an object-oriented modeling environment. After providing the underlying motivation for the research effort, they describe some of the major research tasks. Highlights of this development effort consist of the following: physical and information/decision components are modeled separately; a set-theoretic formalism is provided; a model a specification language is critical; and a powerful graphical user interface is essential. Current status and future plans are described View full abstract»

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  • Overlapping batch statistics

    Page(s): 395 - 398
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    The authors discuss the extension of batching algorithms from sample means to more general estimators. They provide assumptions sufficient for unbiasedness and convergence and provide computationally efficient algorithms for variances and quantiles. Although the definitions, discussion, and examples generalize to general batching estimators, the authors consider only the completely overlapping version View full abstract»

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  • A five level hierarchy for the management of simulation models

    Page(s): 55 - 64
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    The goal-driven automated generation of models from a set of design specifications is described. A five-level hierarchy is introduced which supports the automated generation of both models and simulation experiments from an abstract description of an overall design, and from an abstract description of the goals of the simulation study. The aim is to be able to generate models and experiments in a top-down fashion from a description of static components and the couplings between these components by automating the stepwise refinement process. Detailed model descriptions are extracted from template files residing in model libraries. The authors emphasize problems encountered in the automatic generation of continuous-system models since the synthesis of these models is more involved than the synthesis of discrete-event models. It is shown how a particular implementation of an automatic model synthesis tool, the DEVS-Scheme modeling environment, can be used to tackle a number of important realistic application problems View full abstract»

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  • Toward real time simulation: prototyping of a large scale parallel ground target simulation

    Page(s): 870 - 877
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    The current implementation of the Dynamic Ground Target Simulator (DGTS), used at the Rome Air Development Center, is too slow, too small in area covered, and lacks some functionality necessary for long-term needs. An analysis of the simulation was conducted to look at the performance characteristics of the existing simulation. A need for three or more orders of magnitude greater computational performance was projected. Technologies were surveyed, and a design plan was developed which is expected to achieve the desired performance utilizing coarse grain shared memory parallel processing. In the technique chosen, groups of events of the same or nearly the same time are executed together as a set of parallel tasks. The state space management mechanism ensures determinism and task independence by handling state data changes as updates while maintaining a read-only reference copy of the state. This technique is appropriate to this simulation due to the large proportion of time-step-like event processing, as for movement, and the requirements of modeling a perception-rich environment in which efficient read access to information about one object by another is important View full abstract»

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  • A generalized reliability block diagram (RBD) simulation

    Page(s): 551 - 556
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    The authors demonstrate a computer simulation yielding reliability and maintainability information for any system based on the failure and repair distributions of the individual components. The information needed to link the various components together is taken directly from the reliability block diagram (RBD), thereby negating the need for writing specialized programs. Final results display 90% confidence intervals for four key endogenous variables: system availability, first failure time, mean time between failures, and mean time to repair. Techniques for reducing computer memory requirements are discussed. It is demonstrated how connections between process blocks can be generalized and linked together during program execution. This method results in more useful programs that solve a broader range of problems View full abstract»

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  • ALSS II: The Advanced Assembly Line System Simulator

    Page(s): 625 - 631
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    Introduces ALSS II, the Advanced Assembly Line System Simulator, a special-purpose simulator used to model and analyze assembly line systems. The ALSS II model constructs are introduced. An assembly line system example is modeled and selected results are presented. ALSS II has proven to be an effective tool for rapidly analyzing complex assembly line systems. Because it is SIMAN IV based, if a particular system cannot be adequately modeled using ALSS II, a more detailed model can be developed in SIMAN IV View full abstract»

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  • Distributed simulation: No special tools required

    Page(s): 423 - 427
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    A toolkit of C language functions that can be linked with SIMSCRIPT programs to provide the data communication primitives necessary for distributed simulation is presented. This toolkit can be used to develop distributed simulation applications without having to invest in new environments or training. The toolkit is composed of 650 lines of C code and requires about 50 lines of additional SIMSCRIPT code per server/receiver pair to be added to the simulation model. The user need only be concerned with three C function calls and two SIMSCRIPT routines; thus the complexity of the simulation program is no significantly affected. The use of these tools is most likely to be beneficial in models that can be decomposed into components in which information flow among processors is not cyclic View full abstract»

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  • Object oriented programming languages for developing simulation-related software

    Page(s): 482 - 485
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    A comparative study has been done in which a portion of an icon-based simulation program generator is implemented in each of four object-oriented programming languages that are available for MS-DOS and PC-DOS based personal computers. The languages studied are MODSIM II, Objective-C 4.0, Smalltalk/V 286, and Zoretch C++. These languages and versions of older languages produce code that runs much more quickly than code produced by earlier object-oriented programming languages, thereby eliminating much of the execution speed penalty commonly associated with object-oriented programming. The choice of which object-oriented language to use is dependent on the syntax one feels most comfortable with, the appropriateness to the job at hand of the classes in the libraries provided with the language, and the quality of support given by the programming environment supplied with the language View full abstract»

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  • The role of polymorphism in class evolution in the DEVS-Scheme environment

    Page(s): 401 - 406
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    The DEVS-Scheme environment is a realization of the DEVS (discrete event system specification) formalism in a Lisp-based object-oriented environment which supports specification of discrete event models in a hierarchical, modular fashion. The author describes how polymorphism can be exploited in the development of model classes within the DEVS-Scheme environment. The development of subclasses of the class `coupled-models' in DEVS-Scheme, which are suited for simulation modeling for parallel computer systems, is described to show the role of polymorphism View full abstract»

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  • A simulation for combat systems development and acceptance testing

    Page(s): 210 - 213
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    The Combat Direction System (CDS) subsystem performs command and control of the combat system aboard ship. To perform this function, sensor information from radars, sonars and communication data links is required. A coordinated picture, based on these sensor inputs, is presented for proper decision making on what ordnance should be placed on each threat. Development of CDS programs necessitates actual or reasonable simulation of the various sensor, data link, and weapon system interfaces, for proper stimulus during the latter stages of development and subsequent testing. The author describes the US Navy's Integrated Combat Systems Test Facility involvement in the development of a real-time simulation program used by program developers and testers. The Combat System Simulation (CSS) provides a coordinated environment of vehicular targets and ownship motion. CSS also provides control linkages between itself and the SATSIMs (satellite simulations) to allow for specific operator or scenario control of the different SATSIMs. Events such as missile launch are fed back to the CSS for vehicular track generation View full abstract»

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  • Some optimal simulation designs for estimating quadratic response surface functions

    Page(s): 337 - 343
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    Presents some experimental design strategies for simulation studies involving the estimation of quadratic response surfaces. Optimal design plans are developed in four common second-order design classes (central composite, Box-Behnken, three-level factorial, and small composite designs) using a criterion which incorporates both the bias and variance of the predicted response variable. Three methods of assigning pseudorandom number streams to design points are considered: independent streams, common streams, and the simultaneous use of common and antithetic streams in an orthogonally blockable experimental design. Each method uses independent streams for replications of design points. The findings indicate that carefully planned experimental designs can substantially improve the estimation of quadratic response surface models View full abstract»

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  • Introduction to the General Simulation System GSS and its application to communication systems

    Page(s): 162 - 167
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    The GSS provides a complete environment for modeling discrete event simulation and for analyzing complex dynamic systems. This system has been used to build models, run simulations, and analyze both radio and switched communications systems for the US Government and commercial communications companies. These tools provide significant time and cost savings when building large-scale models and simulations. Features include typing in hundreds of data sets containing thousands of sample points for scenario input files and data collection output files. Also included are automated facilities for parametric and sensitivity analysis, and optimizations. Additional capabilities include the multi-computer option to run a simulation on more than one computer and the real-time option to run a simulation in real-time. Graphics facilities provide for model development and documentation, run-time animation of the network and mechanisms of interest, and graphic representation of statistical results View full abstract»

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  • Special purpose simulator development

    Page(s): 67 - 71
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    Seven years of experience at developing special-purpose simulators using standard simulation languages is reviewed. These simulators were designed to be used by manufacturing engineers or managers with little or no simulation modeling experience. These simulators have used Lotus worksheets or model development programs to provide the system data to be simulated. The results are available by either screen displays during the simulation or via data files which can be converted to Lotus graphs or viewed using data analysis programs. The common strategies and procedures used to develop the special purpose simulators are outlined. The simulation language features used to develop the special purpose simulators are discussed, and input model data concerns are reviewed. The output options for the special purpose simulators are also discussed View full abstract»

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  • Effects of distributed database modeling on evaluation of transaction rollbacks

    Page(s): 839 - 845
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    The effect of the distributed database transaction models on the computational complexity and accuracy of the rollback statistics in a partitioned database is investigated. The author develops six probabilistic models and gives expressions for the number of rollbacks under each of these models. Essentially, the models differ in terms of the available system information. The analytical results are compared to results from simulation. It is concluded that most of the probabilistic models yield overly conservative estimates of the number of rollbacks. The effect of transaction commutativity on system throughput is also grossly undermined when such models are used View full abstract»

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  • An evaluation technique for a protocol in development

    Page(s): 884 - 887
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    Existing local area network protocol evaluation techniques are found to be inefficient in the evaluation of a protocol in development. A protocol evaluation process is formulated to help quickly assess if the Xpress Transfer Protocol (XTP) meets the real-time data communications requirements of the US Navy. The evaluation technique combines a detailed analysis of the XTP specification with attempts to implement selected parts of the protocol. Special attention is given to those aspects of the protocol that affect real-time tactical data communications. It is found that the protocol evaluation process is appropriate for evaluating XTP and that a number of areas of the originally proposed protocol are not sufficiently specified or fail to meet the military needs of the Navy. Timely feedback to the protocol developers enables them to implement changes that solve the problems found View full abstract»

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  • Electronic manufacturing cell design using PC-based modeling and simulation tools

    Page(s): 559 - 563
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    The authors describe the design of a high volume circuit board manufacturing cell using a set of PC-based modeling and simulation tools. The approach allowed design, modeling, and evaluation of the cell in a short time frame. The analysis consisted of six different steps. Rough cut analysis narrowed down the range of important decision variables in the operations of the cell. The analysis was performed using MANUPLAN II, a rapid modeling tool based on queuing theory. This tool was also used to perform a sensitivity analysis of the effect of breakdown factors. Simulation of the critical areas of the cell made it possible to fine-tune the buffer sizes and the number of machines. The simulation was performed using SIMAN, different layout alternatives were generated with MAC DRAW, and cost analysis was performed with EXCEL. Multiattribute variate analysis was used to rate qualitative and quantitative factors to compare different alternatives View full abstract»

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