bluuebunny/crossref_metadata_2025_split huggingface dataset:
Poiseuille flow with variable physical properties — a simulation approach
Authors: Cheng S.C. , Birta L.G. , Kumar A. 
Published: March 2008

This paper investigates two computational approaches to the solution of a particular nonequilibrium fluid problem of Poiseuille flow. In the problem formula tion considered, the viscosity μ and the thermal con ductivity k are taken to be functions of temperature. By incorporating certain assumptions, the fundamental partial differential equations describing the phys ical situation can be simplified to a pair of non linear ordinary differential equations. The problem solution, however, is embedded in a two-point boundary value problem whose solution is complicated by an ill-behaved region at one end of the solution trajectory. Solutions to the problem are obtained using both an analog/hybrid computer and the S/360 CSMP package. The mechanisms provided in both these computational environments for handling logic signals provides the means for coping with the ill-behaved feature inher ent in the solution trajectory. The results obtained in both approaches compare favorably with previously reported results based on the Picard method. Each of the two approaches has its inherent advan tages and disadvantages in the context of the prob lem considered. With little doubt, the high "inter activity" of the analog/hybrid approach represented its most noteworthy asset, while the relative ease with which the basic problem dynamics could be pro grammed was the most advantageous feature of the CSMP approach. However, the relative difficulty in handling the two-point boundary value problem in the CSMP approach complicated the total programming effort required.
An Overview of Cornmod: a Dynamic Simulator of Corn Production
Authors: Baker Charles H. , Horrocks R.D. 
Published: March 2008

CORNMOD is a comprehensive mathematical model that not only simulates energy and gas ex change at the plant-air interface but also predicts the consequences of decisions (e.g., when to plant, when to irrigate). An extensive search of the litera ture revealed many models that antedate CORN MOD, and many of them were adequate for biological applications. However, the search also revealed many inadequacies in our understanding of the environment within the plant canopy. CORNMOD is a simulator of agricultural crop- production systems and it forms a basic framework for a model that will eventually be able to analyze more complex agricultural systems. At present the model is still being developed, and much work remains to be done.
Modeling demographic-employment interactions in an urban economy
Authors: Markland Robert E. , Grandstaff Peter J. 
Published: March 2008

This paper describes a simulation model of the economy of the St. Louis Standard Metropolitan Statistical Area. The model focuses on the opera tion of the area's labor market. It uses (a) an age-specific regimen for predicting changes in population and (b) the concept that the area's unemployment level is inversely related to the area's exports. The validity of the model is tested by setting its initial conditions to the 1960 values of the vari ables in the model and running it forward to 1970. The resultant errors are then analyzed and, with two exceptions, found to be small. The exceptions are analyzed and hypotheses to explain them are outlined. The authors conclude that the model should be useful in finding the key areas in the local economy and in experimenting with economic policies to assess the long-term impact of alternate policies on the local economy. A systematic simulation study is then designed, and approximately 100 runs are made. Analysis of these runs indicates (a) that the transportation-equipment industry is the key industry in the area and (b) that increasing its growth rate by 2 percent annually over the USA national average for that industry, combined with a 0.1 decrease in the relative cost ratio (compared to the national average) of labor in the durable-fabrication area, would have a very marked effect in reducing unem ployment in the St. Louis area.
An interactive digital simulation and optimization package: FORTRAN programs MINISIM and OPTSIM
Authors: Roach John R. , Chow Ee-Pan 
Published: March 2008

MINISIM is a general-purpose interactive digital simulation program which is written in FORTRAN and is suitable for both interactive and batch use. The program currently utilizes a fixed-step 4th-order Runge-Kutta integration algorithm. The program has proved to be suitable as a replacement for an analog computer in both teaching and research activities. OPTSIM is an extension of MINISIM that permits optimizing simulated systems automatically while making use of the MINISIM integration routines. The same problem-description subroutine (SUBROUTINE EQUATN ) may be used with either MINISIM or OPTSIM. Detailed examples are given of the simulation and optimization of a control system and also of the solution of a two-point boundary-value optimization problem.
Simulating the use of space in a hospital surgical suite
Authors: Kwak N.K. , Kuzdrall Paul J. , Schmitz Homer H. 
Published: March 2008

This paper describes a simulation procedure for determining the number of patients that the recovery room must accommodate in a hospital with a given number of operating rooms. The particular case simu- Zated was that of Deaconess Hospital in Saint Louis, which has 505 beds and 5 operating rooms. The statistics on the use of the operating rooms and the recovery room were collected from hospital records and incorporated in the simulation. They take into account the types of surgery performed, the number of patients receiving each type of surgical treatment, the patients' need for the recovery room, and the length of time patients need to stay in the recovery room (a statistical function of the type of surgery). The simulation uses Monte Carlo techniques. Its results closely duplicated the hospital's experience and were accepted by management as the basis for deciding the capacity of the recovery room that would be required after the hospital expanded its facilities. It was found that with 5 operating rooms this hospital required a recovery room with a capacity for 13 patients. The simulation is a general one that can be applied to other hospitals. This paper includes the principal results of the simulation of the operation of the Deaconess Hospital's surgical suite as it affects the number of patients served by the recovery room.
Simulation of an investment in convertible bonds
Authors: Roberts Darrell D. 
Published: March 2008

A general-purpose quantitative model of an investment in convertible bonds (corporation bonds which the holder may convert into stock) selling below par value (usually $ 1000) was developed using the GPSS simulation language. The simulation was written in such a way that all the variables are changeable as desired. The model assumes an investor who manages his own account and purchases convertible bonds, using an account in which monthly investments are accumulated. The computation assumes that the maximum allowable amount is borrowed from the brokerage firm for the purchase using the purchased bonds as security for the loan, and that the account maintains itself (i.e., the the interest on and capital gains from the converti ble bonds pay the brokerage firm's interest charges and the income taxes on capital gains and on the interest earned by the bonds). The results of the simulation runs, which cover a 20-year time period, give quantities for many items. An example of some of the quantitative values resulting from an exercise of the model are the following: the number of convertible bonds owned by the investor at the end of the time period, the amount of income from interest, the amount of interest paid on borrowed money, taxes paid on interest and capital-gains income, and many other quantities of interest when such an investment is undertaken.
Implicit integration for CSMP III and the problem of stiffness
Authors: Watson H.D.D. , Gourlay A.R. 
Published: March 2008

The phenomenon of stiffness in differential systems is described, and the problem of instability in the numerical integration of such systems is discussed. The need for implicit integration methods is demon strated together with the consequential requirement for the extensive use of sparse-matrix techniques. A specific implementation of an implicit stiff- system integration routine, STIFFX, based on Gear's algorithm and designed for use with the IBM continuous system simulation language CSMP III is described, and its efficiency is compared with that of the STIFF routine which is a part of CSMP III.
Applying simulation to highway intersection design
Authors: Varol Yaacov L. , Kaufman Arie A. , Hanani Michael Z. 
Published: March 2008

This paper describes a simulation model of driver- vehicle behaviour at an intersection and two versions (one batch, one interactive) of its implementation. The model offers the user considerable flexibility in specifying the intersection, the traffic control techniques, and the volume and other characteristics of the traffic. It incorporates some of the latest findings of human factors research concerning the driving task, and represents the driver's perceptual, decision-making, and response processes as the driver approaches, passes through, and leaves the intersec tion. Driver behaviour is based on various percep tual cues and on psychophysical judgements derived from them. We rejected gap-acceptance distribution as the basis for driver behaviour at the intersection because we formulated the model for intersection design. vali dation tests showed that the model created gap- acceptance data statistically equivalent to field data. Two implementations of the conceptual model have been built. They are modular in design and are programmed in FORTRAN because of its transportability and proven efficiency in use of CPU time and of memory for traffic simulation. The batch-mode version runs on any computer having a FORTRAN IV compiler; it has already been used successfully in the complete rede sign of an old intersection. The interactive version runs on a minicomputer with a graphics display; it is being considered for driver re-education.
Statistical estimation of feedback models
Authors: Senge Peter M. 
Published: March 2008

This paper considers the accuracy of conventional econometric techniques in estimating parameters in a feedback model. Evaluation of the estimation techni ques is accomplished by an experimental procedure in which a nonlinear feedback model generates synthetic data which is then used to estimate the parameters in the data-generating model. Comparison of the estimated and "true" parameter values provides a measure of the accuracy of the estimation technique. Experiments with ordinary and generalized least- squares estimation (OLS and GLS) show that the parameter estimates derived from these methods are highly sensitive to errors in data measurement, especially when a model's feedback structure is not completely known. Further tests of OLS and GLS with different feedback models, as well as experimental evaluations of other estimation techniques, should help to determine the proper role of statistical methods in modeling feedback systems.
Simulation of semiconductor devices
Authors: Akers Lex A. 
Published: March 2008

The simulation of semiconductor devices is a powerful means for optimizing the performance of semiconduc tor circuits and devices. various classes of semi conductor models exist, but accurate simulations re quire exact ("total") computer models. The exact models allow the use of arbitrary initial conditions and internal distributions and describe the device accurately over wide ranges of operation. This article discusses the leading numerical formula tions used to generate exact semiconductor models and describes the simulation of an NP junction, a bipolar transistor, and a MOS field effect transistor using exact models.
A GASP IV model of steel ingot processing
Authors: Surh Dae S. , Talavage Joseph J. 
Published: March 2008

This paper describes a GASP IV model of part of a steel mill. The processes modeled include pouring molten steel into molds, removing (stripping) the hot ingots from the molds, and sending them to the soaking pits and finally to the primary rolling mill. Molds move from a preparation area to the furnaces, thence to the stripping cranes, and back to the pre paration area. Rail trains transport ingots and molds. The major problem is how to dispatch a limited number of rail engines to pull trains so that materials and molds are at the right places at the right times for efficient operation. A set of 32 experiments (indi vidual simulation runs) was devised to find an opti mum combination of number of engines, number of transportation zones, and dispatching rules for a particular steel mill. The set of experiments showed (not surprisingly) that the use of a single transportation zone (so that all engines were able to go wherever they were needed) and a larger number of engines resulted in the greatest percentages of on-time deliveries and (somewhat surprisingly) that random and priority selection of engines worked equally well and were better than selecting the nearest engine, even when that choice was modified by a priority rule.
Shakespeare as Simulationist
Authors: Baker Dennis W. 
Published: March 2008

Dennis Baker first became involved with simulation in 1965 when he was at what is now the David W. Taylor Naval Ship Research and Development Center in Annapolis. There, as a co-op student from Drexel University, he met a TR-48 and spent his entire final work period teaching himself analog programming and developing a simple model of ship motion. Though Dennis was not one of the "thrice-filtered friends" I originally solicited, when he told me on the now-famous SCS Silver Anniversary "Crooze" of his research which led to the following contribution I thought it too important an historical note to be left out of this historical issue.
Using simulation in hospital planning
Authors: Alessandra Anthony J. , Grazman Ted E. 
Published: March 2008

A perplexing problem today in many hospital clinics is how to manage patient flow effectively. An example of poor management was found in the family planning clinic of a large Southeastern hospital. Employee workloads and patient service times both varied greatly, with periods of overwork and over crowding followed by periods of virtual inactivity. The hospital administrators wanted to correct the problem without disrupting personnel or patients and without spending money on capital improvements. (The entire clinic was soon to be relocated.) A computer model was developed to study how changes in staffing policies would affect the observed bottle necks. Current operating procedures along with seven alternatives were examined. Simulation allowed the study of these approaches without large capital expenditures or disturbances in normal operations. This study not only shows the solution to a particular problem in patient flow but also shows how sophisticat ed analytical techniques can be used in the rapidly expanding health delivery field.
A model of residential energy use
Authors: Hirst Eric 
Published: March 2008

A model of residential energy use was developed to simulate the period from 1970 to 2000. The model predicts annual energy use by fuel, end use, and type of housing, and also estimates annual equipment installations and ownership, equipment energy re quirements, structural heat retention, fuel expendi tures, equipment costs, and costs for improving heat retention in new and existing housing units. Thus the model provides considerable detail on residential energy uses and associated costs. These details are useful for evaluating the effects of alternative energy conservation policies, programs, and tech nologies during the next quarter century. The present version of the model handles four fuels, eight end uses, and three types of housing. Each of these 96 components of total energy use is calculated each year as a function of stocks of occupied housing units and new construction, equipment ownership by fuel and end use, heat retention of housing units, average unit energy requirements for each type of equipment, and usage factors that depend on household behavior. Simulation of energy use from 1960 to 1975 shows that the model accurately predicts historical data on aggregate energy use, energy use by fuel, energy use by end use, and market shares of ownership of equipment.
Using sensitivity analysis to simplify ecosystem models: a case study
Authors: Rose Michael R. , Harmsen R. 
Published: March 2008

Theoretical ecology requires simulation because real istic ecosystem models are too complex for mathemati cal analysis. In this paper we propose a way of moving from a complex simulation model based on the "mechanics" of an ecosystem to a much simpler model that exhibits behaviour similar to that of the origi nal model in its major features. The tool used to isolate the key characteristics of the original model is sensitivity analysis. It enables the investigator to identify the variables and parameters that deter mine the essential behaviour of the original model and to formulate a clear picture of that behaviour. With this information in hand, the investigator can devise a simplified model that exhibits the same essential behaviour. While the simplified model behaves like the original model, its inner workings only generally parallel those of the original. Its simplicity allows the investigator to test his intuitive ideas directly, clarifying understanding of the ecosystem originally modelled. Further, the investigator may be able to adapt the simplified model to other similar ecosystems. The methods outlined in this paper are illustrated by a case study of a forest infested by tent caterpillars.
A simulator for multilevel distribution systems
Authors: Blank Leland 
Published: March 2008

This article describes the use of simulation to de sign a multilevel distribution system which is supplied by one manufacturing plant and several local suppliers. The program is written in SIMSCRIPT. Each regional warehouse is assumed to obtain most of its product from one distribution center, which is in turn supplied by the manufacturer. The model generates forecasts at each level based on demand data which is randomized in accordance with empirical distributions. If the manufacturing capacities, which in the simula tion are user-specified, are too small to meet the demand, the model adjusts the distribution schedule. Each warehouse is provided the opportunity to pur chase some fraction of its demand for any item from a local independent supplier on a routine basis and on an extra-purchase basis when the manufacturer can not supply the item through his distribution centers. The article discusses model validation and an appli cation of the simulator to determine the optimum number and the locations of storage facilities and to improve inventory control.
Simulation of a shell-and-tube condenser
Authors: Saraf G.R. , Dhar P.L. 
Published: March 2008

This paper presents the computer simulation of a shell-and-tube condenser with a subcooler. It con siders the variation of the coefficient of condensa tion heat transfer along the tube in the condenser and the effects of the subcooler. A general computer program for the simulation of such condensers has been developed. The simulation has been validated by comparing the simulated performance of a typical industrial con denser with the condenser's rated performance as cited by the manufacturer. Close correspondence has been found between the two.
Load management strategies for electric utilities: a production cost simulation
Authors: Blair Peter D. 
Published: March 2008

This paper deals with the development and application of a simulation model for analyzing strategies for managing the residential loads of electric utilitities. The basic components of the model are (1) a produc tion-cost model, which simulates daily operation of an electric power system, (2) a load model, which disaggregates system loads into appliance loads and other loads, and (3) a comparison model, which com pares the production costs and energy consumption needed to meet a particular load profile to the cor responding costs and energy consumption required for another load profile. The profiles in each pair define alternative ways of meeting the same demand. A method for disaggregating load profiles into appliance components is discussed and several alter native strategies for residential load management for a typical northeastern electric utility are formulated. The method is based on an analysis of the composition of electric loads for a number of classes of residen tial customers in the model utility system. The effect of alternative load management strategies on the entire residential loadcurve is determined by predicting the effects of these strategies on the specific appliance components of the loadcurve. The results of using the model to analyze alternative strategies for residential load management suggest that load management strategies in the residential sector, if adopted by utilities whose operating and load characteristics are similar to those of the sys tem modeled here, must take into account a wide variety of appliances to achieve significant changes in the total load profile. Moreover, the results also suggest that it is not easy to reduce costs significantly through new strategies for managing residential loads only and that, to be worthwhile, cost-reducing strategies will have to encompass many kinds of appliances,
Simulation of a supercritical once-through boiler
Authors: Suzuki Yutaka , Sik Pyong , Uchida Yoshihisa 
Published: March 2008

The problem addressed is that of improving the control system of an existing supercritical once-through boiler. To do this, it was necessary to construct a dynamic mathematical model of it. This paper describes the model that was developed; it is based on the nonlinear partial differential equations which describe the physical phenomena in the boiler. These equations involve transfer functions that cannot be obtained directly; they were found by linearizing the equations and estimating the values of unknown parameters from the boiler's input-output operational records. The model includes both forward and back ward causalities in determining the water and steam flow. Simulation results indicate that the model is valid and that the control system requires modifica tion. The investigated boiler has a capacity of 450 MW and is presently operating at Kainan Thermal Power Station of Kansai Electric Power Company.
The simulation of Coulomb friction in mechanical systems
Authors: Bernard James E. 
Published: March 2008

Coulomb or dry friction occurs in mechanical systems when nonlubricated surfaces come into sliding contact. The force resulting from Coulomb friction has a magnitude dependent on the contact force and a direc tion opposite to the relative velocity. If the re lative velocity is zero, the Coulomb friction assumes the value, within bounds, to maintain zero velocity. This, of course, presents the opportunity for a variety of equilibrium configurations. This paper presents an overview of the common tech niques for the digital simulation of Coulomb fric tion. All these techniques use the relative velocity to determine the friction force and are therefore flawed since they cannot predict multiple equilibrium positions. By means of an example, this paper shows that modeling Coulomb friction as a function of posi tion rather than of velocity allows multiple equili bria and offers features that are useful in modeling high-friction, low-mass systems.