bluuebunny/crossref_metadata_2025 huggingface dataset:
Local Compilation: A Novel Paradigm for Multilanguage-Based and Reliable Distributed Computing over the Internet
Authors: Wong Allan K. Y. , Lin Wilfred W. K. , Dillon Tharam S.
Published: March 2008

The local compilation environment (LCE) supports object-based, multilanguage-based and reliable distrib uted computing over the Internet, which may include wireless connections. It also supports the notion of component software engineering (CSE), which means constructing programs from existing software mod ules or parts created by different domain experts and vendors. By nature, a CSE-based program is compos ite and would not work properly without support from local compilation, which employs dynamic compilation that differs from the Java JIT (just in time) compila tion approach. In the LCE, data interoperability among composite program objects is supported. The two LCE foundation constituents, the coordinator and the local compilation process, are discussed, and test data from the prototype is presented. In particular, the data for the LCE notion of reliability by object mobility will be discussed in more detail. Results from experiments indicate that the novel local compilation paradigm is indeed an effective solution.
Performance Analysis of a Multicast Protocol for Wireless Environments
Authors: Sadok Djamel F. H. , Cordeiro Carlos de M. , Kelner Judith
Published: March 2008

This paper presents a performance study, using both analytical modeling and simulation techniques, of a new end-to-end reliable multicast protocol for use in environments with wireless access. The proposed pro tocol, called the reliable mobile multicast protocol (RM2), divides a multicast tree into sub-trees where subcasting is applied within the relatively smaller regions using a hierarchical tree of retransmission servers (RSs). RM2 is receiver-oriented in that the transmitter does not need to know its receivers, hence offering better scalability. The Internet Group Management Protocol is used to manage group membership whereas the IETF's Mobile IP offers support to user mobility through a temporary IP address. Each RS has a retransmission subcast ad dress shared by its members which may be dynamically configured using allocation schemes such as the IETF's MADCAP. More important, RM2 uses a dynamic re transmission strategy to switch between multicast and unicast retransmission modes according to the amount of extra load generated in the network and in the wire less interfaces by packet retransmissions. It is shown through analytical modeling and simulation that RM2's dynamic adaptation is not only important but also necessary when considering mobile wireless access.
Buckling Analysis of a Building Stud-Spacer Assembly and Simulation of Spacer Punching Process
Authors: Guo J. , Narh K.A.
Published: March 2008

A computational finite element analysis (FEA) model was created for buckling analysis of the stud-spacer assembly used in the construction of building walls, using a commercial software. The numerical simulation results show that the number of spacers used in the stud assembly, as well as the materials used for the spacers, have little effect on the buckling load of the stud as sembly. Consequently, a low-value material such as recyclable plastic waste can be used as the connecting spacer for the stud frame. The effect of the geometrical shape of the stud cross-section on the buckling was also analyzed. The proposed punching process for assembling the stud and spacers was simulated by the available capabili ties of the software.
Using Expert Systems for Simulation Modeling of Patient Scheduling
Authors: Standridge Charles R. , Steward Duane
Published: March 2008

Modeling the scheduling of patient appointments is an important issue in simulating a health care delivery facility. A simulation model must in clude the control logic of appointment scheduling software and the explicit and implicit decision rules used by the human scheduler in selecting an appointment time. Expert systems provide one way of modeling such control logic and decision rules. We describe a structure for an expert sys tem that models patient appointment scheduling and the integration of such an expert system within a simulation model. An example expert system for a small animal veterinary clinic is presented.
Analysis of Dual-Bus Metropolitan Area Networks Using Distributed Quantitative Stochastic Simulation
Authors: Yau Victor , Pawlikowski Krzysztof
Published: March 2008

The Distributed Queue Dual Bus protocol (DQDB) has been adopted by IEEE and by the International Standard Organisation as a metropolitan area net work standard. DQDB is also a European Telecom munication Standard. Using distributed simulation, this paper analyzes the performance of standard DQDB networks, DQDB networks with slot band width reuse, as well as DQDB networks with slot preuse and reuse. The results suggest that although slot preuse is a conceptual mirror image of slot reuse, the maximum improvement in throughput of the networks, the causes of unfairness, and the stations which are unfairly favoured differ depending on the choice of bandwidth single-use, reuse, preuse, or pre-and-reuse. All quantitative performance measures were estimated to a specific precision using automated distributed stochastic simulation. The design of the DQDB simulators and practical implications of the results are also discussed.
A New Heuristic Optimization Algorithm: Harmony Search
Authors: Zong Woo Geem  , Joong Hoon Kim  , Loganathan G.V.
Published: March 2008

Many optimization problems in various fields have been solved using diverse optimization al gorithms. Traditional optimization techniques such as linear programming (LP), non-linear programming (NLP), and dynamic program ming (DP) have had major roles in solving these problems. However, their drawbacks generate demand for other types of algorithms, such as heuristic optimization approaches (simulated annealing, tabu search, and evolutionary algo rithms). However, there are still some possibili ties of devising new heuristic algorithms based on analogies with natural or artificial phenom ena. A new heuristic algorithm, mimicking the improvisation of music players, has been devel oped and named Harmony Search (HS). The performance of the algorithm is illustrated with a traveling salesman problem (TSP), a specific academic optimization problem, and a least-cost pipe network design problem.
Pricing and Managing a Maintenance Contract for a Fleet of Aircraft Engines
Authors: Bowman R. Alan , Schmee Josef
Published: March 2008

A large corporation wished to expand its role as a provider of maintenance and repair services for aircraft engines. These services were to be provided to airlines based on long-term contracts. The mag nitude and uncertainty of the costs involved (total costs for a typical contract would be in excess of a billion dollars) could expose the corporation to sig nificant financial risk. To help mitigate and man age this risk, a simulation model was developed to assess costs over the life of the contract. The pri mary objective was to establish a fair contract price. The simulation model also allowed opera tional issues and sensitivities to be examined.
A Simulation Study on the Performance Analysis of the Data Link Layer of IEC/ISA Fieldbus
Authors: Seung Ho Hong  , Seong Jun Ko
Published: March 2008

Fieldbus provides real-time data communication among field devices in the process control and fac tory automation systems. IEC and ISA recently approved the fieldbus standard for use in indus trial control systems. The data link layer of IEC/ ISA fieldbus provides token-passing and schedul ing services for data transmission. This paper ana lyzes the performance characteristics of the IEC/ ISA fieldbus, especially the capabilities of the real- time data transmission and priority mechanism. In this study, a discrete-event simulation model of the data link layer of IEC/ISA fieldbus is developed. Using the simulation model, this study identifies the network parameters that influence the perfor mance of the data link layer, and investigates the delay performance with respect to the change of the network parameters. Based on the simulation analy sis, this study draws essential conclusions that should be considered in the network system design and operation of IEC/ISA fieldbus.
Computer-aided Shaft Design and Selection of Rolling-contact Bearings Using an Expert System
Authors: Mendi F. , Taskesen A. , Kisioglu Y.
Published: March 2008

In this study, a computer program was developed using Q-Basic programming language to analyze the strength and deformation of a rotating circular stepped shaft. These shafts have a variety of power- transmitting mechanical elements (components), such as pairs of gears, and pulleys that are modeled in 3-D. In addition, force and moment analyses of these elements running on the shafts are examined. Notch sensitivity and stress concentration factors given graphically were formulated using the finite difference method. Furthermore, to select the best rolling-contact bearings, an expert system requiring the knowledge-based technique was employed. The knowledge of the expert system and data of the roll ing bearing catalogue were input into the program. To perform the expert system, the LEONARDO software technique was used.
Importance Sampling to Evaluate Real-time System Reliability: A Case Study
Authors: Durairaj G. , Koren I. , Krishna C.M.
Published: March 2008

Real-time distributed computers are often used in life- critical applications. However, the complexity of such systems calls for extensive simulation studies to validate their performance and reliability before a design can be accepted and a prototype constructed. A simulator testbed has been built to model a variety of such systems quickly from a few basic building blocks. Life-critical applications require reliability levels so high that brute-force simula tion to validate these levels would take weeks of computer time. In this paper, we present studies we have conducted into the use of importance sampling in simulating real- time systems. This paper presents a interesting case- study of the use of importance sampling in an increas ingly important branch of computer engineering. Impor tance sampling may not work for all cases and over all parameter ranges. In this paper, we are interested in finding out whether (and how well) this scheme works for the case of distributed real-time systems and also the range of failure bias values for which it works well. Specifically, we look at the implementation of two heuris tics called 'forcing' and failure biasing' in the testbed. This was validated by comparing the reliability estimates with that of normal (very long) simulation. The effect of the failure bias on the dynamics of the scheme is also investigated to provide readers with some guidance on choosing appropriate bias values.
Teaching Object-oriented Simulation in a Software Engineering Framework
Authors: Kornecki Andrew J.
Published: March 2008

Each year, object-oriented methodology (including its three main aspects—analysis, design, and programming) has been gaining more and more acceptance from the soft ware industry. This acceptance is preceded by multi-disci plinary research in the fields of simulation, artificial intel ligence, computer science, and software engineering. Year after year, new computer science and engineering pro grams produce graduates that join the ranks of software systems developers. Software industry representatives fre quently complain that the newcomers lack skills in practi cal aspects of software engineering. Another deficiency of undergraduate programs has been caused by traditional approach to teaching procedural programming. In the last few years, more programs started using C++ or Java for introductory computer science classes. However, in many cases, the teaching methodology did not change and the objects are introduced as an afterthought. This paper de scribes a junior-level course in an undergraduate com puter science program, designed to teach object-oriented design and coding, while introducing discrete modeling and computer simulation concepts. Additionally, the course provides a vehicle for development of small team class projects addressing critical aspects of the modern software development life cycle. The author's experience with teaching the course may serve as a model for similar offerings in other colleges and universities.
DEVS-Based Framework for Modeling/Simulation of Mobile Agent Systems
Authors: Kim Jae-Hyun , Tag Gon Kim
Published: March 2008

This paper presents a formal modeling and simulation framework for mobile agent sys tems. A Mobile Discrete Event System Specifi cation (MDEVS) formalism is proposed to rep resent the dynamics of mobile agent systems. The MDEVS formalism supports structural changes of the systems, which include the cre ation, addition, deletion, and migration of mod els and the dynamic changes of couplings be tween models. AgentSim is a software environ ment for the simulation and execution of mobile agent systems modeled by the MDEVS formalism. AgentSim is implemented as a li brary built on IBM's Aglets. The modeling and simulation of an e-commerce mobile agent sys tem is exemplified to demonstrate the effective ness of the proposed modeling framework and the associated simulation environment.
A Distributed Agent-based Simulation Environment for Interference Detection and Resolution
Authors: Ramaswamy S. , Srinivasan K. , Rajan P.K. , Krishnamurthy S. , MacFadzean R.
Published: March 2008

In this paper, a two-level architecture is developed and implemented for the interactive simulation and evaluation of a distributed agent-based simulation environment designed to detect and resolve interfer ence in naval radar units. The Java-based simulation is designed as a two level software architecture incor porating: (i) multiple radars on each ship controlled through a lower-level intra-ship interference control module, and (ii) multiple ships in a group coordi nated through a higher-level interference control module. Each ship's interference detection and reso lution mechanism, termed a control agent, is com posed of these two separate levels, which dynamically coordinate to detect and then resolve interference problems using three different coordination strate gies—a Master-Slave, a Locally Autonomous and a simple Negotiation mode.
Simulation-based SW/HW Architectural Design Configurations for Distributed Mission Training Systems
Authors: Sarjoughian Hessam S. , Hild Daryl R. , Xiaolin Hu  , Strini Robert A.
Published: March 2008

Distributed Mission Training (DMT) is a concept composed of promising technologies that support training in a variety of domains such as defense and medicine. To develop and deploy such systems, it is important to account concurrently for hardware and software requirements, given high demands for net work bandwidth, computing resources, and com plexity of software applications. In this paper, we present the application of a distributed co-design methodology (Discrete Event System Specification/ Distributed Object Computing) as applied to the Mission Training and Rehearsal System (MTRS), a DMT system. For an example, we show that the developed simulation models allow prediction of the network capacity below which messages cannot be sent and therefore incorrect behavior results. The key issues presented are (1) characterization of the DMT style architectures in DEVS/DOC, (2) prediction of DMT-like basic scalability traits via simulation, and (3) discussion on some open problems underlying the applicability of distributed co-design for systems containing "off-the-shelf' components.
Design and Development of Data Distribution Management Environment
Authors: Lee Jong S. , Zeigler Bernard P. , Venkatesan Shankar M.
Published: March 2008

This paper describes the design and development of the DEVS/GDDM environment, a layered simulation environment that supports data dis tribution management and allows us to study space-based quantization schemes. These schemes aim to achieve effective reduction of data commu nication in distributed simulation. After a brief review of the space-based quantization scheme and an HLA-Interface environment, we discuss the design issues of the DEVS/GDDM environ ment. We analyze system performance and scalability of the space-based quantization scheme, especially with predictive and multiplex ing extensions, and empirical results for a ballis tic missiles simulation executing on the DEVS/ GDDM environment on NT networking plat forms. The results indicate the DEVS/GDDM environment is very effective and scalable due to reduced local computation demands and ex tremely favorable communication data reduction.
Modeling Forest Landscapes: Parameter Estimation from Gap Models over Heterogeneous Terrain
Authors: Acevedo Miguel F. , Pamarti Siva , Ablan Magdiel , Urban Dean L. , Mikler Armin
Published: March 2008

Parameter values of a forest landscape model (MO SAIC) are estimated from a terrain sensitive gap model (FACET) over a large number of terrain types. MOSAIC is a semi-Markov model with states defined by cover types. For each terrain type, gap-model output is fed to a program that counts transitions between each pair of states, and estimates the fixed lags and the parameters of the probability density functions of the distributed delays. The gap model and the parameter estimator are executed repetitively for many different steps in the gradients and many ter rain types, taking advantage of a computer cluster running a distributed launching system. The method is illustrated by its application to the H.J. Andrews Forest in the Oregon Cascades. Key transitions in cover type determine the variation of the landscape- model parameters over all terrain types. The method ology presented here provides an automated, consis tent and conceptually clear procedure for scaling up the tree level ecological detail represented by a gap model, to the level ofa patch state-transition model for heterogeneous environmental conditions across the landscape.
An Interactive Design, Visualization, and Analysis Tool for Information Flow Over a Tactical Data Network
Authors: Hill John M. D. , Surdu John R. , Carver Curtis A. , Vaglia James A. , Pooch Udo W.
Published: March 2008

The United States Army is embracing the use of new information technologies to achieve tactical advantage over potential adversaries. Existing and future informa tion systems place a significant load on the tactical data network, resulting in a bandwidth management crisis, yet there is no prioritization, allocation, planning, or manage ment tool available to simulate information flows over time for different communications configurations under different operational conditions. The development of such a tool requires the implementation of a communication network model and the supporting discrete-event simula tion system. Models for the information systems that induce flows, the command posts using the information systems, and the influence of operational conditions on the information flows are also required, as is a graphical user interface that allows the tactical planner to configure the system and set up data capture. The visual development techniques used in this tool make it easy for the planner to design and build communication networks to support operations, then interactively reconfigure the network, run "what-if" scenarios, and visualize the effects. The system can be used for training, design of experimental networks, and to support rapid decision-making.
Visualization and Simulation: Two Sides of the Same Coin?
Authors: Kuljis Jasna , Paul Ray J. , Chaomei Chen
Published: March 2008

Visual simulation is a stepping-stone towards the integration of simulation and visualization. The design and analysis of a visual simulation system CLINSIM, which models a clinic process in a hos pital is described. Analyzing such a system can lead to insights into the nature of the interrela tionship between simulation and visualization. In this article, this visual simulation example clari fies the nature of the difference between visualiza tion and simulation. Several possible roles of visu alization technology have been identified in order to strengthen the power of a simulation system. By incorporating visualization techniques into traditional simulation systems, one can expect that users and analysts will benefit from better- informed simulation models across the real and virtual worlds.
Performance Simulation of a Dependable Distributed System
Authors: Yinong Chen  , Mateer Roger
Published: March 2008

The aim of our research is to develop a distributed system platform that supports a variety of tasks. Currently, we are implementing Internet applica tions on the system, including a service redirector, firewall, and web applications. These applications have different levels of dependability requirements. Depending on their criticality, a single task may execute on one or more computer nodes. Software-implemented fault-tolerant proto cols are used to detect the disagreement among replicas. A reconfiguration protocol is used to identify faulty nodes according to the fault reports from other fault-tolerant protocols and to reallo cate their tasks to other working nodes. As a part of the project, this work focuses on the implemen tation and simulation of the system and the firewall application. Data transfer throughput of the system is measured and analyzed. The results are being used in supporting our development of the overall system.
Parallel Job Scheduling in Homogeneous Distributed Systems
Authors: Karatza Helen D. , Hilzer Ralph C.
Published: March 2008

The performance of parallel programs such as those involving fork-join instructions is significantly affected by the method used to schedule program tasks. This article studies parallel job scheduling in homogeneous distributed systems. A simulation model is used to address performance issues associated with scheduling. Various policies are employed to schedule parallel jobs over a variety of workloads. Fairness is required among competing jobs. The authors examine cases in which the distribution of the number of parallel tasks per job, as well as the distribution of task service demand, varies with time. They also examine the impact of overhead necessary to collect global system information about processor queues on performance. Simulated results indicate that although all scheduling methods have merit, one significantly improves the overall performance and guarantees fairness in terms of individual job execution.
Studying the Conditions for Learning Dynamic Bayesian Networks to Discover Genetic Regulatory Networks
Authors: van Berlo R. J. P. , van Someren E. P. , Reinders M. J. T.
Published: March 2008

Learning regulatory interactions between genes from microarray measurements presents one of the major challenges in functional genomics. This article studies the suitability of learning dynamic Bayesian networks under realistic experimental settings. Through extensive artificial-data experiments, it is investigated how the performance of discovering the true interactions depends on varying data conditions. These experiments show that the performance most strongly deteriorates when the connectivity of the original network increases, and more than a proportional increase in the number of samples is needed to compensate for this. Furthermore, it was found that a lower performance is achieved when the original network size becomes larger, but this decrease can be greatly reduced with increased computational effort. Finally, it is shown that the performance of the search algorithm benefits more from a larger number of restarts rather than from the use of more sophisticated search strategies.
Hybrid Techniques Applied To Optimization Problems
Authors: Witsenhausen Hans S.
Published: March 2008

A function dependent on the solution of a set of dif ferential equations containing adjustable parameters, can be minimized by systematic search procedures in parameter space. Such procedures can be imple mented by a hybrid system consisting of a general purpose analog computer and a digital expansion providing parallel logic building blocks. Program ming of such a system is illustrated for a simple search procedure in n parameters.
Development of Memory Core
Authors: Jury Stanley H.
Published: March 2008

Using this memory unit, an analog computer can operate in the same way as a digital computer. Computer size no longer limits the size of the problem which can be handled
Theoretical Foundations for the Computer-Aided Design System
Authors: Ross Douglas T. , Rodriguez Jorge E.
Published: March 2008

This work has been made possible through the support extended to the Massachusetts Institute of Technology, Electronic Systems Laboratory, by the Manufacturing Technology Laboratory, ASD, Wright-Patterson Air Force Base, under Contract No. AF-33(600)- 42859. It is published for technical information only and does not necessarily represent the recommendations or conclusions of the sponsoring agency.
Simulation of Infrared Systems
Authors: Meissinger H.F.
Published: March 2008

This material was first published as a result of work performed by the author while on the technical staff of Hughes Aircraft Company, Culver City, California.
Examples of Analog Computer Applications in Nuclear Processes
Authors: Cameron W.D. , Taylor G.R.
Published: March 2008

The purpose of this report is to outline and explain the various methods used in simulating atomic re actors and processes, particularly the types used at the Hanford plant. This report describes the newer as well as the standard techniques used in reactor simulation. Applications are described by examples. The techniques used in a complete atomic reactor plant simulator are described.

Chemical processing simulations are discussed using specific examples.
Simulation of a Biological System On an Analog Computer
Authors: DeLand E.C.
Published: March 2008

The purpose of this paper is to discuss a method for the construction of a mathematical model of a large biological system. This method, based on Gibbs' free energy hypothesis, uses the format of mathematical programming, while the actual computation is ac complished by the method of steepest descent. The biological system chosen to exemplify the mathe matical method was the respiratory function of the blood in the human lung. This method is based on the postulate that chemical mixtures tend toward a reaction equilibrium which minimizes the potential, or free energy, of the system. We may thus write down the classical Gibbs free energy function for each chemical species, and require that total free energy relative to some standard state be minimized under the conditions of the experiment. The solution of the equilibrium problem consists of a set of mole numbers which minimizes the free energy function, subject to equations for conservation of mass and nonnegativity.

The analog computer solution of the respiration model was undertaken not only to give fast, sensitive tests of the mathematical model and its assumptions, but also to obtain a simulation of the time depend ent system. Examples of the mechanization of the equations are presented in this paper, and also results are computed for the static equilibrium of a canoni cal model.
A Method of Generating Functions of Several Variables Using Analog Diode Logic
Authors: Wilkinson R.H.
Published: March 2008

A diode-resistor network technique for simulating functions of any number of variables is described. The function is approximated by a polyhedron, or its N-dimensional equivalent, and this polyhedral model is generated directly by the circuit. The circuit is formed of two cascaded sections: the first, using resistive networks, generates voltages representing each of the faces of the polyhedron; the second section, using analog diode logic, selects the appro priate voltage as the output.

The analog diode logic uses basic circuits similar to those used in digital logic. It is shown that the analog logic can be described by a distributive lattice, closely related to Boolean algebra. Methods of logic synthesis are developed. Circuit design is discussed, and it is shown how the effect on the logic section of the finite source impedance of the resistive net works which feed it can be turned to practical ad vantage.

The specific example of the multiplication of two variables is studied in some detail, providing a basis of comparison with the known techniques such as the quarter-square and log-antilog methods. Finally, test results on a simple three-variable function gen erator are given.

The method is not incremental in nature, and differs from current techniques in this regard. Thus the setting up of a function on a generator is simpli fied, owing to the noninteraction between segments. Also, the area of the input space to be covered is adjustable to correspond with the input domain of the function.
A Simulation of a Generalized Thermal Radiating Fin
Authors: Janicke M.T. , Just L.C.
Published: March 2008

The purpose of this paper is to provide a method for designing radiator fins with maximum heat removal capability per pound of construction material. This problem becomes important when radiators are designed for space applications, since all of the heat from the thermodynamic cycle must be removed by means of radiation. Moreover, space transportation vehicles are seriously limited as to payload, so that weight must be saved in all parts of a power plant. An increase in the output of a space power plant does not change the reactor, turbine, and generator as much as the radiator, with the result that, for megawatt electrical systems, the radiator is the dominant weight contributing component.

A radiator could be built of coolant tubes alone, but this increases certain hazards. Meteor punctures can occur, so that the amount of area devoted to coolant tubes should be reduced as much as pos sible. Fins attached between the tubes can perform this function by extending the heat radiating surface. The extra weight of the fins is partly compensated for by a reduction in tubes and coolant. Extra savings can occur if the weight of the fin is minimized; optimum thickness, length, and cross section must be found. This paper studies the relationship between fin cross- section and radiating power.
The Simulation of Large Transients in Neutron Reactors
Authors: Just Louis C. , Morehouse Nye F.
Published: March 2008

The simulation of the reactor kinetics equations on an analog computer presents no difficulties in most applications. However, in situations where the reac tor is designed to give large bursts of neutrons, ana log computers do not have a great enough range. Fortunately, it is possible to transform the kinetics equations into a form in which the log of neutron flux instead of the flux is the dependent variable. This permits the simulation of pulsed reactors such as TREAT, or certain types of rocket motors.
A Wide-Band Computing Amplifier and A High-Speed Analogue Multiplier
Authors: Barber Derek L.A.
Published: March 2008

The design of an operational amplifier is discussed and theoretical values of stage gains for maximum bandwidth are deduced. A practical circuit is de scribed in which these theoretically desirable stage gains are achieved.

The result is an amplifier with a bandwidth about two orders greater than is commonly attained, which, furthermore, is the best performance that may reasonably be realized with the valves that are employed.

The amplifier, together with a high-speed multi plier, forms the basis of the Fast Analogue Com puting Equipment (FACE) developed at the National Physical Laboratory.
A Mathematical Model of Heart Rate Control by Sympathetic and Vagus Efferent Information
Authors: Warner Homer R. , Cox Albert
Published: March 2008

The effect on heart rate of stimulation of sympathetic and vagus efferent nerves to the heart has been described in a qualitative fashion by many investiga tors. However, except for the work of Rosenblueth and Simeone1 in 1934, no attempt has been made to analyze in a quantitative way the dynamic relation ship between heart rate and frequency of stimulation of these nerves. The present study was undertaken with the hope that such an analysis might yield useful information regarding a) the nature of the physical and chemical events involved in this transformation and b) the dynamic and steady-state parameters of this link of the heart rate control system.
Dynamic Programming and Hybrid Computation
Authors: Vichnevetsky R. , Waha J.P.
Published: March 2008

Dynamic programming finds its use in operations research, chem ical engineering, control systems, and other fields of applied mathematics; and is primarily concerned with the optimisation of multistage decision processes. Dynamic programming will split up the problem into a succession of N one-dimensional optimisation problems. The optimising action takes place at each discrete stage of the process.

The technique is based on the so-called principle, of opti mality, as expressed by Bellmann.

The paper describes the various techniques involved.

A hybrid analogue/digital computer will serve as an ideal tool, having the ability to integrate differential systems of equations, and also to perform the logical operations required in connec tion with the optimisation of the return function.
A survey of Digital Simulation: Digital Analog Simulator Programs
Authors: Brennan Robert D. , Linebarger Robert N.
Published: March 2008

This is the first of an intended series of articles on digital simulation. Digital simulation abounds in many fields and disciplines — analog simulators, cir cuit simulators, chemical process simulators, traffic simulators, systems simulators, business simulators. At this point in time, a general survey of digital simu lation is overdue. Its orderly development demands sufficient respite for a critical evaluation of its prog ress thus far and its goals for the future. just what is digital simulation? - where does it stand presently and how did it get there? — where does it seem to be going ? This series hopes merely to stimulate the tech nical conversations which will furnish these answers. This article restricts attention to digital-analog simulator programs-those programs which simulate the elements and organization of analog computers. It is intended to be both tutorial and documentary in its presentation. This topic was selected for the first article because this segment of digital simulation is of most general interest to analog users. In the opinion of the authors, the transcendence of digital computers for simulation is inevitable, and it is of paramount importance to capture the interest of analog users in order that their vast experience not be lost as simulation enters this new era..
Flood Simulator for the River Kitakami
Authors: Otoba Kotaro , Shibatini Kozi , Kuwata Hiroshi
Published: March 2008

Recent developments in electronic computers have resulted in the production of a variety of simulators. One of these is a hybrid computing system manu factured to perform analysis and prediction of floods on the river Kitakami. Having an analog computer as a main assembly, the system operates to indicate the water level and discharge at every moment in the main stream and each branch according to the volume of rainfall wen by means of punched paper tape. It is a novel large-scale special system which is in practical use. The introduction into the computer of volume of rainfall by means of a multiplex time- variable function generator and the use of transfer function representation for hydrographic data are the most conspicuous among many features.
Hybrid-Computer Techniques for Measuring Statistics from Quantized Data
Authors: Korn Granino A.
Published: March 2008

Digital data processing necessarily involves quantization (roundoff) of input data. The statistical theory of amplitude quantization indicates that the effects of quantization on statistics are often negligible or can be approximately predicted and corrected, even with surprisingly coarse quantization. This tutorial paper reviews contributions to the theory made in England, the Netherlands, and Russia, as well as B. Widrow's original work in this country. Applications to remarkably inexpensive hybrid analog-digital averaging computers and correlators are also discussed. The theory can pay very handsome practical dividends: in many applications, 2- to 4-bit analog-to-digital converters and data-transmission channels can yield averages, mean squares, and correlation functions with 10- to 20-bit accuracy, and one-bit (polarity-coincidence) correlators are often practical.
Experiments Using Pseudo-Random Noise
Authors: Hampton Robert L.
Published: March 2008

This paper describes the results of experiments per formed with pseudo-random noise sequences. It is shown that Gaussian noise can be easily produced from such sequences. It is also demonstrated that the sequences themselves have a binomial proba bility distribution.

The correlation technique investigated, using pseudo-random noise, makes possible a continuous recording of a system's impulse response without the use of any sophisticated hardware. The impulse re sponse obtained from the cross-correlation experi ment can be approached from either the positive or negative direction, i.e., τ can be made not only a time delay, but also a time advance. This enables one to observe the trailing end of a waveform before viewing its leading end. It also permits a quick ex perimental verification of the correlation property that Rxy(τ) = Ry,r(—τ). Examples for a first- and sec ond-order system are given.
A Hybrid Analog-Digital Parameter Optimizer for ASTRAC II
Authors: Mitchell Baker Adams
Published: March 2008

A new automatic multiparameter optimizer for iter ative differential analyzers employs sequential ran dom parameter perturbation. The nominal parameter point changes whenever the random perturbations improve the system performance measure. Binary counters operate simple digital-to-analog converters to implement parameter storage, multiplication, and step-size changes. All-digital logic yields different types of random perturbations, viz., simple random walk, random walk with reflecting or absorbing bar riers, and various types of correlation over successive perturbations.
Hybrid computing: a user's view
Authors: Clancy John J. , Fineberg Mark S.
Published: March 2008

The analog computer section of the McDonnell Automation Center has been involved in hybrid com puting for some time now, leading us to think we can contribute to the dialogue now proceeding on the subject. In this article we first detail the only rational criteria for selecting a computing method, namely cost and capability, and then present the classes of problems that are prime candidates for hybrid solu tion. A brief description of our present facility is included, along with our views on selecting hybrid programmers.

Looking ahead, we have outlined requirements for a future hybrid system, placing a good deal of em phasis on software needs, especially a simple, parallel language based on MIDAS, DYSAC, etc. An exam ination of hardware costs and the characteristics of the new breed of digital computers suggests that, although hybrid computation can be done more efficiently with the new generation, there is a pos sibility that neither hybrid nor analog computation in their present forms can survive the onslaught of low-cost digital computing. The outlook is not as bleak as first appears, since we believe analog con cepts can be retained in future systems, but only if SIMULATION readers and other interested parties are willing to make an issue of it.
A fast 10v diode quarter square multiplier
Authors: Whigham Robert H.
Published: March 2008

This report describes the design and performance of a fast wideband quarter-square diode multiplier de signed to work with the ±10-v low-impedance com puting circuits of a high-speed iterative differential analyzer (ASTRAC II), or in other hybrid analog- digital computer systems. To reduce cost, the new multiplier employs absolute-value squaring circuits and does not require committed computer ampli fiers. Improved combination shunt-series switching circuits and low resistance values ensure wide band width (±0.5% of half-scale dynamic error at 10 Kc, <1 degree phase shift below 70 Kc). Temperature- compensating diodes in the bias networks reduce thermal drift below 0.7 mv/°C, so that the multiplier static accuracy of ±0.20% of half-scale is maintained from 15 to 40° C. A number of useful design hints are listed.
Modal simulation of unidirectional fluid dynamics (water hammer)
Authors: Childs Dara
Published: March 2008

This paper presents a general approach to analog simulation of "water-hammer" type phenomena. In brief, the simulation approach consists of obtaining a general Fourier-series time solution in terms of boundary variables (pressures or flowrates), retaining a finite number of terms in this series solution, and then obtaining the ordinary differential equations to which the terms correspond. One customarily "winces" when contemplating a series solution of any form, particularly when informed that the solu tion is to be subsequently approximated by retaining only a finite number of terms. Although the mathe matical manipulations contained in the paper may appear forbidding, they need be developed but once, and the final differential equations which result are quite simple. Truncation of the Fourier series solu tions happily results only in a truncation of the valid frequency range. Within this valid frequency range there is little or no loss in accuracy. These and other advantageous characteristics of the modal simula tion technique are developed by various analytical and numerical examples.
Hybrid computer Monte Carlo techniques
Authors: Korn Granino A.
Published: March 2008

This report introduces hybrid analog-digital com puter systems suitable for high-speed Monte-Carlo studies and suggests methods for further reducing the computing time, such as sequential estimation and a number of variance-reducing techniques. Shift- register-generated pseudo-random-noise is especially convenient for many hybrid analog-digital computa tions. Applications to the solution of partial differ ential equations and to random-search optimization are outlined.
Analog computer solution of a third-order Pontryagin optimum control system
Authors: Anderson M.D. , Gupta S.C.
Published: March 2008

Pontryagin's maximum principle is used to develop a method for solving several types of optimal control problems on the analog computer. In particular, this is applied to a third-order control system, and the results shown. The restrictions on the problem and the analog computer are shown, and a procedure for setting up and using the analog mechanization is given.
Digitalization of continuous control systems
Authors: Breuer M.A.
Published: March 2008

This paper deals with the development of methods for analysis, and derivation of computer programs, for digitalizing continuous control systems. More spe cifically, given a continuous control system, we wish to determine an "equivalent" computer program to take the place of some analog shaping network in the system. An equivalent program is one for which the response of the digital system approximates the response of the continuous system in the time do main. Time and frequency comparisons between the responses of continuous and digitalized systems to step inputs are given. Equivalent computer programs for various standard shaping networks are derived. Revised programs are determined, where use is made of prediction and extrapolation techniques to com pensate for digital computation delay time.

Finally, the feedback network in a missile control system containing an unstable aerodynamic airframe is digitalized, and the simulated system is run on an analog-digital hybrid computer system. Results are given, indicating system performance as a function of sampling rate, computation delay, and system gains.
Regions of asymptotic stability of dynamic systems by the combination of Lyapunov techniques and digital simulation
Authors: Fahidy Thomas Z.
Published: March 2008

The usefulness of the combination of the Lyapunov function technique and digital simulation for the stability analysis of dynamic systems is illustrated in two examples where the region of asymptotic sta bility is estimated by the analytical Lyapunov ap proach and established by a systematic search via digital simulation of the Lyapunov function. The ad vantage of the PACTOLUS simulator, with particular regard to man-to-machine interference, is empha sized.
An analysis of continuous parameter identification methods
Authors: Meissinger H.F. , Bekey G.A.
Published: March 2008

Some of the material in this paper was first presented at an International Symposium on Sensitivity Analysis in Dubrovnik, Yugoslavia, in September 1964
Digital realization of complex transfer functions
Authors: Fleischer Paul E.
Published: March 2008

The need for realizing an arbitrary complex transfer func tion often arises in digital or hybrid simulation. A method for the optimal design of the digital implementation (equiv alent to a tapped delay line) of such transfer functions is presented. This procedure finds application in both purely digital and closed-loop hybrid simulations. In the latter case, the digital computer extends the capability and ca pacity of the analog computer and provides an efficient realization of complex transfer functions.

Since the sampling frequencies for most simulations are run above the Nyquist rate, the procedure is designed to ignore the higher frequencies where signal energy is ab sent. In this fashion an optimum match to the desired characteristic can be achieved in the frequency band of interest. The procedure can fully compensate for degrada tions introduced by the hybrid sample-hold and recon struction method.
The application of the MIDAS digital simulator to the study of kinetic alternatives in a chemical reaction system
Authors: Fahidy T.Z. , Perlmutter D.D.
Published: March 2008

The frequency response of the platinum-catalyzed sulphur dioxide oxidation system was simulated for four alterna tive rate expressions suggested in the literature for the chemical kinetics in a nonflow stirred reactor. By compar ing the results of MIDAS digital simulation with experi mentally obtained frequency responses, it was established that the dynamic behavior of this reaction system is not affected significantly by the proposed reaction mecha nisms.
Analog computer simulation of abnormal periodic breathing
Authors: Milhorn Howard T. , Guyton Arthur C.
Published: March 2008

The human respiratory system is compared to a techno logical feedback control system. Oscillation of the tech nological system is discussed and related to abnormal oscillation of human respiration (Cheyne-Stokes breath ing). A mathematical model of the human respiratory control system, utilizing CO 2 control of respiration only, is derived and programmed on an analog computer. The resulting computer study has shown that, as in the tech nological system, an increase of open-loop gain and/or delay time around the open loop can cause the respiratory system to become unstable and oscillate in an abnormal manner.