bluuebunny/crossref_metadata_2025_split huggingface dataset:
Simulating oxygen transport in the microcirculation by Monte Carlo methods
Authors: Halberg Michael R. , Bruley Duane F. , Knisely Melvin H. 
Published: March 2008

Oxygen transport in the human cerebral cortex has been simulated previously by considering a single straight capillary and a concentric tissue cylinder as a representa tive sample (the Krogh tissue cylinder). The same geo metric model has been assumed for this study because of its probable accuracy and to allow comparison with previous calculations. Because of the nonlinear equilibrium relationship be tween dissolved and hemoglobin-bound oxygen (the oxy gen dissociation curve), a differential mass balance yields a nonlinear partial differential equation describing oxy gen transport in the capillary. In the tissue a constant consumption rate is assumed and a linear partial differ ential equation results. The tissue equation and the capillary equation are solved simultaneously, to account for capillary-tissue interaction, thus giving axial and radial oxygen partial pressure profiles for the total system. The Monte Carlo method has been employed to solve the resulting set of equations on a digital computer. This technique involves a numerical scheme wherein a process is simulated directly by a random walk phenomenon (Markov process). A particular advantage of this method is that solutions may be obtained for one point in space independently of all others. Therefore, an analysis of the transient response of the "lethal corner" is possible with out solving for the entire mesh. Computation time with the Monte Carlo method was considerably less than that with standard deterministic numerical calculation tech niques. Two models were considered. In the first model the oxygen dissociation curve was linearized, thus giving a linear partial differential equation describing oxygen transport in the capillary. The second model considered the nonlinear nature of the oxygen dissociation curve, and a nonlinear partial differential equation was ob tained. However, because of difficulties with the Monte Carlo method, it was necessary to solve the equations in a quasi-nonlinear manner. For both the linear and the quasi-nonlinear models, solutions were obtained for the steady state with normal conditions and for dynamic cases. Perturbations of ar terial-oxygen partial pressure and blood flow rate were forced, and the behavior of the system was determined. The pure diffusional model checked with previous de terministic calculations demonstrating very rapid re sponse with time constants in the order of 2 seconds. However, the shapes of the intracapillary and tissue oxy gen tension profiles differed somewhat and no allow ances were made for autoregulatory phenomena such as varying flow rates.
The simulation of shot processes
Authors: Daly K.C. , Thomas J.B. 
Published: March 2008

Shot processes may be used as models for a wide class of naturally occurring random processes ranging from non-Gaussian impulse processes to nearly Gaussian processes. This paper shows how shot processes with desired spectral properties may be simulated easily. Sev eral models are proposed for using shot processes as locally generated noise sources with statistical charac teristics which conform to many naturally occurring noise processes. More general models could be considered and the range of applicability can be extended beyond that men tioned in this paper. However, even the basic models treated can provide a much wider range of noise envi ronment than that usually considered in simulation tech niques.
The inverse modeling problem
Authors: Patten Bernard C. 
Published: March 2008

In simulation modeling of very large-scale systems, such as social and natural systems, reductions in scale must be so severe that state variables of the abstraction (model) often cannot be translated back to variables that have real-world significance. Model behavior may not much resemble anything that occurs naturally. If y is a real system and x a model of it, the two can be viewed as related by a set of homomorphic corres pondences M. Then, xMy means x "is a model of" y. Behavior of x pertains to that of y only as M is a valid model, and the relationship is implicit in an inverse model M-1, defined from the fact that xMy implies yM-1x (y "is modeled by" x). To make it explicit, that is to interpret model behavior in terms of real-world variables, means in some sense to be able to identify M-1. One approach to estimating it is suggested, but a definite solution is not reached.
A solid-state crossbar switch for automatic analog-computer patching by
Authors: Yagi A. 
Published: March 2008

An all-electronic crossbar switch consisting of FET series-shunt switches inside the feedback loops of operational amplifiers was designed and constructed. Time-shared solution of five different differential equations was obtained by using four integrators on ASTRAC II, with a new solution being generated 25C times per second. Crossbar switches for automatic patching Studies of practical automatic patching schemes for electronic analog computers indicate that it will be economical to employ sets of relatively simple crossbar switches somewhat in the manner of tele phone exchanges. This report describes the con struction and test of a small all-solid-state cross bar switch which permits very fast switching for analog-computer time-sharing, is suitable for integrated-circuit construction, and should be much more reliable than the relay instrumentation sug gested in Reference 1. The feedback multiplexer The new crossbar switch is based on the feedback
Analog simulation of particle trajectories in a cyclone separator
Authors: Cheng Shang-I. , Teller Aaron J. 
Published: March 2008

The trajectories of liquid droplets and dust parti cles in a wet cyclonic scrubber were studied via mathematical modeling on TR-20 analog computers. This simulation study was restricted (1) to two- dimensional flow and (2) by the assumption of Stokes' Law behavior. The penetration of spray droplets into the gas flow field and the time of effective contact with the gas field at high relative velocities were found to be critically dependent on the diameter of the spray droplet and on the angle of injection, in addition to the anticipated dependency on gas flow rate and on projection velocity of the spray particle. It was found that for small particles (<50μ) the drag forces were so high relative to the initial forces that only insignificant penetration of the vapor body occurred, even at a projection velocity of 200 feet per second. At an average rotational air velocity of 50 fps a maximum probability of effective interception and impaction of spray and entrained particles occurred in the region of a spray angle of 30° to the tangent.
A GASP simulation study of job-shop scheduling
Authors: Ashour Said , Vaswani S.D. 
Published: March 2008

The purpose of this paper is to report on a study which involves a simulation of a hypothetical job shop with several machines. The investigation employs GASP-II as a computer language. This simulation study is concerned with: (1) testing a new method of assign ing job due-dates and (2) comparing and evaluating the effect of different processing-time distributions on the performance of a number of scheduling rules. The most significant results of this study are: (1) The shortest-imminent-operation rule is superior to others in reducing job lateness and shop flow time (2) The procedure in which the due-date allowance is proportional to the number of operations and work content of the jobs has proved to be beneficial in the case of the non-due-date rules (3) The operation of a job shop using the shortest-imminent-operation and slack-per-remaining-number-of-operations rules is degraded when the processing-time distribution having Erlang parameter K equal to 4 or 8. However, per formance is better when K = 8 than when K = 4 (4) The GASP-II package works efficiently for large-size shop problems.
A comparative study of digital and hybrid simulation of production lines
Authors: Khalil T.M. , Valisalo P.E. 
Published: March 2008

This paper describes the application of digital and hybrid simulation to the problem of deliberate unba lancing of production lines to obtain shorter produc tion times. The paper demonstrates that hybrid simulation tech niques adequately match the accuracy of digital simulation of the same system. The hybrid provided more flexibility with a reduction in cost.
Digital/analog simulation of electromechanical devices on a graphics terminal
Authors: Sharma Satya P. , Roe C.D. 
Published: March 2008

Computer simulation of electromechanical devices by exercising a suitable mathematical model has advantages in studying the effects of parameter changes. As a specific example, an electromechan ical relay has been chosen for simulation in this investigation. A differential equation model of the relay 1 is developed and simulated on an IBM 1130/2250 graphics terminal using the 1130 Continuous System Modeling Program (CSMP). An optical displacement measuring system was used to measure the armature travel as a function of time while the relay was functioning. These mea sured characteristics were compared with the analogous characteristics of the simulated relay to evaluate the validity and accuracy of the mathematical model. It is concluded that the differential equation model is an adequate appro ximation provided the lumped parameters of the magnetic circuit are appropriately chosen. The influence on the dynamic response of the relay as various relay parameters are changed can easily be predicted from the simulated model in this study.
An ISL-8 and ISL-15 study of the physiological simulation benchmark experiment
Authors: Benham R.D. 
Published: March 2008

PHYSBE is an acroynm for PHYsiological Simulation Benchmark Experiment, and was introduced1 as a suggested standard for evaluating tools and tech niques available for physiological simulation. The mathematical model relates pressure, volume, flow, and resistance in a simplified cardiovascular system. PHYSBE is an excellent benchmark problem because it is not easy to obtain accurate results with an all-analog or all-digital simulation. The large differences in time-dependent constants (1.63 to 90.0) allow a good check of digital integration routines. Roundoff accumulation errors can be devastating to digital solutions. On the other hand the compliance generators (the driving func tions) are difficult to program with general- purpose diode function generators found on analog computers. Previous PHYSBE articles2,3,4 have discussed the amount of time it has taken to program with FORTRAN (on a CDC 3600 computer), MIMIC and DSL/90 (on an IBM 7090 computer), CSMP (on an IBM 1130 computer), and DARE I (on a PDP-9 computer). Very little attention has been focused on solution accuracy. Examination of published results for the all digital simulations of PHYSBE show serious accuracy problems. There appears to be a 5% to 10% difference in pressure and volume values that are published. There is good reason for the FORTRAN, MIMIC, and DSL/90 results to agree, but they do not. Also one would expect the CSMP and DARE I results to agree, but they do not. This ISL-8 simulation shows that good agreement was obtained with an IBM 1130 CSMP solution after an error was corrected in the CSMP program. Detailed accuracy comparisons with the other solu tions are complicated because not all of the same variables are reported in the same manner. There fore the documentation format suggested by McLeod2 is used here so that ISL-8 and CSMP solutions can be compared with future work with PHYSBE.
An optimal design of a soaking-pit rolling-mill system
Authors: Ashour Said , Bindingnavle S.G. 
Published: March 2008

While attention in the iron and steel industry has been focused on the study and analysis of the flow of materials through the main productive units (blast furnaces, steel works, and rolling mills), the analysis of this flow through the nonproductive units (the mixer and soaking pits) is generally over looked. These two units would create serious bottle necks in production if their capacities were not properly determined before being installed. This paper considers the soaking-pit/rolling-mill complex as a queueing system in which the soaking pits are viewed as units circulating a cyclic queue, and the rolling mill as the service station. A simulation model representing the pit-mill system is developed: (1) To predict the improvement in the capacity of the system through adding more pits (2) To predict the effect of breakdowns and mainte nance or the shutdown of a pit. Several criteria, including their economic aspects, are used to measure the performance of the system. The optimal capacity of the system is determined such that an economic balance between the cost of service and the cost of waiting for that service is achieved.
Application of Computer Simulation To Research in the Life Sciences
Authors: Garfinkel David , McLeod John , Pring Martin , DiToro Dominic 
Published: March 2008

The paper summarizes guidelines for applying computer simulation to life sciences research. It provides brief answers to the following questions: To what extent can problems be rigorously solved by simu lation—especially complicated problems—and how is this to be done? What can a given simulation study be expected to accomplish, and when can it be considered complete? Of what value are the properties of a model in understanding the living system under study? What should be the proper interaction between simulationists and subject-matter experts in a collaboration? What constitutes ethical conduct for a simulationist? To what extent should the same person do both experiments and simu lation? How should simulationists be trained?
Mass transfer in a packed bed of fibers
Authors: Burley R. , Flower J.R. , Rattee I.D. 
Published: March 2008

Commencing with a simple but realistic mathemati cal model of dispersion, absorption, and desorp tion of dye within a cylindrical packed bed of fibers, a finite difference scheme of equations was developed capable of analog solution. By varying the main kinetic and mass-transfer pa rameters, the dynamic response of the system was determined and preferred changes of operating values were indicated. We suggest that these methods could be widely ap plied in the study of systems involving mass trans fer and reaction; to determine the individual effect of descriptive physical parameters on a pro cess without recourse to complex mathematical procedures.
The simulation of the neutron diffusion equations over many decades
Authors: Morehouse N.F. , Carter J.C. , Bryant L.T. 
Published: March 2008

This paper describes the simulation of a nuclear re actor system using the neutron diffusion equations coupled to the thermodynamic and mechanical equations. In this coupling, representation of the diffusion equation presents considerable difficulty when large power excursions are being simulated. This difficul ty arises from the diverse response times (from 10-8 to 10-1 second) of the coupled equations of the system. In this paper a transformation of the dif fusion equations is developed which permits coupling them to mechanical and thermodynamic equations of much slower response times, thus eliminating the difficulties previously encountered in simulating these coupled sets of equations. In the transformation, time is the continuous vari able and energy and space are made discrete. The reactor core is divided into concentric cylindrical regions and the energy is divided into bands. The transformtion involves using natural logarithm of the neutron flux in the center region as a refer ence and determining the change in the ratio of the natural logarithm of the neutron fluxes in the other regions to that in the center region as a result of a regional variation in neutron produc tion. The transformation permits a simulation to cover many decades of continuous change in neutron flux. It also gives directly the deviation from the steady-state neutron flux distribution.
Simulation of speech by time-ordered wave function sets
Authors: Carey Bernard J. 
Published: March 2008

A simulation of human speech is normally performed to represent the acoustic signal in a form from which meaningful features of interest in the time and frequency domains may be identified and used in attempting to solve research and applications prob- Zems. Frequency-domain simulations related to vocal tract modeling have been the most popular techniques used to date. However, approaches have been investi gated which, for the limited case of voiced sounds, simulate human speech in the time domain by time- ordered time-based wavefunction sets. This paper discusses the use of a new technique for an accurate, complete simulation of any human speech by the family of Hanning Cosine Modulated (HCM) wavefunctions. The previous research on wavefunction simulations of speech are first discussed and then, through illus trative examples, it is demonstrated that HCM wave functions may accurately simulate the behavior of speech in either the time or frequency domain. The actual parameters of the wavefunctions which re present filtered speech may be measured by an auto matic digital signal analysis technique. These parameters then form a data base which, in conjunc tion with the HCM model, provide a closed-form solution in the time or frequency domain for analyzing and synthesizing speech, and they permit a convenient determination of a wide variety of speech features of interest.
The daughter of Celia, the French flag, and the firing squad
Authors: Herman G.T. , Liu W.H. 
Published: March 2008

In earlier work we have reported on CELIA, a program for simulating the behavior of linear iterative arrays of cells. The action of a cell is influenced by both its neighbors. Our main application area was biology, where the program can be used to test hypotheses about the developmental rules for organisms. More recently we have been applying our program to test proposed solutions to some fairly complicated biozogically-based problems. We have investigated whether one can achieve regulative global polarity in organisms without polarity in individual cells, by solving the French flag problem of Wolpert, using only symmetric elements. In our attempted simulation of pigmentation patterns on the shells of sea-snails, we have found it necessary to find a solution to a generalized version of the firing squad synchronization problem, in which the firing squad is growing while it is trying to synchronize itself. We found that our original program CELIA was some what awkward for simulating such complicated situa tions. A new program has been devised in which the state of the individual ceZZs is described by a set of attributes and each attribute itself may be a list structure. The present paper reports on these changes and ex plains how they turn out to be useful in the appli cations mentioned above.
The construction of a robot investor
Authors: Krolak Patrick D. , Lindahl C.E. , Herndon J.M. 
Published: March 2008

The ROBOT INVESTOR is an integrated system of computer heuristics based in part on human experience and port folio management theory. It is designed to receive information about the state of the current stock mar ket and the investor's existing portfolio and to translate this information into actions that will provide a reasonable and stable rate of return. This paper is the next logical step in the process. The robot forecasts the future price behavior of, and estimates risks of, individual stocks. This informa tion is passed to a decision model, which is designed to meet the dynamic real-world problem of continuous portfolio management. The Robot Investor includes a forecaster, a decision model, an accounting section, and an adaptive control section. The robot has been tested on a randomly selected list chosen from 740 major corporations traded on the New York and American Stock Exchanges and over the counter, using the monthly prices from January 1960 to December 1967. The results are competitive with those of mutual funds over the same period. An advanced model based on this study has significantly improved the performance of an investment club.
Debugging aids for hybrid- computer programmers
Authors: Lew Art 
Published: March 2008

We discuss here proposals for two new debugging aids for hybrid-computer programmers. For digital programs, "relevant" post-mortem dumps have long been advocated .1 We propose extending this philoso phy to analog dumps. We describe means of making selective dumps via analysis of the topological structure of analog programs. We also propose a novel analog static-check procedure which takes advantage of the greater computational facilities afforded by a digital computer to solve algebraic equations. The analog-dump and static-check methods recommended here, at worst, help hybrid programmers with their debugging efforts by automating certain common tac tics. Many errors can thereby be automatically detected and precisely located. In conclusion, we suggest how correction of these errors can be auto mated to some extent.
Some time-saving methods for the digital simulation of highway vehicles
Authors: Bernard James E. 
Published: March 2008

Simulation has been used extensively as a tool for the solution of vehicle-dynamics problems. To handle nonlinear simulations of increasing size and complexity, both digital and hybrid methods have been used. As might be expected, purely digital simulation often proves to be more convenient, while hybrid proves to be more economical. Methods have been developed to provide substantial economies in the digital simulations. Savings by roughly a factor of five may be realized by trans forming the wheel-spin integrations into a solvable set of algebraic equations and by making use of some well-known mechanical characteristics of vehicles to simplify the integration procedure.
A work game for social services
Authors: Algie Jimmy , Hall Anthony S. 
Published: March 2008

This paper describes a work game which the authors developed for the National Institute of Social Work (Training), Britain's professional social work train ing institution. Though intended primarily as a training and decision-making device for use by So cial Service managers, it is capable of modification for various planning groups, for example, a British LocaZ Government management group or an American in ter-agency welfare planning committee. It is parti cularly relevant in situations where diverse services are integrated under a new unified structure. The game focuses on the interplay between rational decision-making and political bargaining which takes place when allocating scarce resources within an integrated social services agency. It comprises a series of rounds, each representing a complete financial year in the life of one such agency. Eight role-players representing key decision- makers negotiate and bargain for policies which they believe the agency should follow. Outcomes of discussions and negotiations are observed by the "God system," four people who represent all aspects of the agency system not otherwise simulated. They make periodic pronouncements as to how agency policy seems to be evolving and how this affects the influence each role-player may exert in subse quent rounds. After several rounds, the experience of the game is discussed in an extensive debriefing session which centres on strategies and tactics employed, the decision-making processes, and the reality reflected in the simulation.