bluuebunny/crossref_metadata_2025_split huggingface dataset:
Minimum altitude visibility diagram —MAVD
Authors: Shannon Robert E. , Ignizio James P. 
Published: March 2008

An essential part of almost all air-defense computer simulation models is the visibility subroutine. This subroutine performs the necessary computations and provides the data required to determine whether enemy aircraft or missiles may be detected by stationary ground-based air-defense system sensors- that is, whether they are within sensor range and whether their visibility is obstructed by terrain irregularities and/or the curvature of the earth. This paper presents a new approach to the visibility subroutine, entitled MAVD (Minimum Altitude Visibi Zi ty Diagram). MAVD provides a visibility subroutine which could be incorporated into existing models relatively easily. The authors believe that it would result in a more realistic simulation and provide a significant reduction in computer time, in comparison with other simulation methods with which the authors are familiar.
Library policy structure: an industrial dynamics study
Authors: Nance Richard E. , Baker Norman R. 
Published: March 2008

An industrial dynamics model of a university library, developed originally to investigate the effect of library control policies, is described. The model is used to analyze the effect of two policies pro posed by the Physics Library at Purdue University. After having operated under extremely crowded con ditions for the past several years, the Physics Library will move in 1971 into new, more spacious quarters. The policies for loans from the library collection have been rather free, control over the collection has been lax, and penalties for users failing to comply with library policies have been mild. The reasoning behind these policies was that if all loaned materials were returned, sufficient shelf space was unavailable. With the space limitations removed in the new quarters, the Physics Librarian can adopt one of two general policies: Policy 1 - Closer control over the library collection, more restrictive loan policies, more staff, and longer operating hours Policy 2 - Less control over the collection with more extended loan policies and increased purchases of multiple copies. Analysis of the two policies shows that Policy 1 effects a reduction in delays in return of loaned material at the expense of incurring user dissatis faction with the library and that Policy 2 results in even higher user satisfaction than is presently experienced.
OLDAS: An On-Line Digital Analog Simulator
Authors: Cullen Richard P. , Green Daniel T. 
Published: March 2008

OLDAS is a conversational system that provides a user with the means to construct, modify, and run programs written in the continuous simulation language MIMIC. OLDAS operates in a multiprogrammed mode on an IBM 360/40 computer. The user terminal consists of an IBM 2250 CRT display with a light pen and alphanumeric keyboard. An IBM 2311 disk pack drive is utilized for storage of user programs and data. MIMIC source programs are entered via the alpha numeric keyboard, displayed on the CRT, and stored on the disk in the form of pages, of which there are three types: Parameter, Program, and Arbitrary Function. To facilitate manipulation and reuse of a program, several versions of it may be stored in the some file on the disk. The principal form of output is a graphical display of results which the user monitors during execution. The user can halt execution at any time, change pro gram parameters and integration options, and specify new results to be plotted. Options which allow a user to display results digitally and to print on- line are available. Results can also be saved on the disk for processing by off-line programs.
On the analog simulation of a pure time delay
Authors: Davies W.D.T. 
Published: March 2008

In the investigation of many physical systems, it becomes necessary to simulate the time-delay phenomenon on the computer. This phenomenon arises in such investigations as shock waves in mechanical systems, sound waves in acoustical systems, and more generally in connection with the flow of materials in chemical processes and heat exchangers. Since information about such systems is not available until a finite time after certain actions have been performed, it is essential to represent this time-delay phenomenon adequately. Various methods have been used to do this, depend ing on the value of the time delay involved and the frequencies contained in the variable quantity passing through the delay. This paper discusses the application of operational amplifiers to form time-delay approximations for those applications where the delay is more or less constant. A number of such approaches are discussed and the resulting approximations are brought into a common form and scale, so that comparisons between the different approximations may be easily accomplished.
HYBRID—a user-developed hybrid interpretive language
Authors: Holst Per A. 
Published: March 2008

An interpretive hybrid programming language, HYBRID, has been developed by The Foxboro Company, for use in a small hybrid computer system. The TELETYPE* oriented language comprises a command structure resembling FOCAL and offers hybrid instructions similar to HOI. It provides features seldom found in software for small (mini) computers with limited core, such as computed (variable) part and step numbers in go-to instructions, foreground- background operational modes, monitor functions, and a full assortment of hybrid and interrupt handling capabilities. The HYBRID program occupies approximately 4K of core in a PDP-7t 18-bit computer and includes routines for drum (disc) and paper tape input- output of source and data files. It permits the use of assembly (machine) language routines to be called by source program commands. The variable list (Symbol Table) is referenced in a binary search mode, which results in fast execution speed as well as efficient running of the source program. The language contains a number of error-checking and source-program protection provisions to make it as user-friendly and fault-tolerant as possible .
Modifications to a digital simulation program to facilitate automatic patching
Authors: Rigas H.B. , Coombs D.J. 
Published: March 2008

One factor of importance in a complete auto matic analog-computer patching system is a software package to provide the actual patching information for a model described in a high-level language. Several approaches to this problem have been proposed. One such program, PATCH, differs from the others in that it not only uses a continuous simulation language as a means of describing the model to be patched, but also actually uses the simulation processor as an integral part of the patching program. The simulator which was used for the imple mentation of the patching program is S/360 CSMP. Since PATCH was first described in the literature, many have inquired about the possibility of using another simulator such as CSSL or MIMIC in the same way. We will attempt here to outline the modifi cations made to CSMP and their purpose so that one intimately familiar with another simulator could make similar alterations to that program. PATCH itself is a subroutine written in FORTRAN IV and could readily be modified to accept input from other simulators.
Hybrid simulation of multicomponent chemical reactions in multifunctional catalyst systems
Authors: Buis J.P. 
Published: March 2008

At the Laboratory of Chemical Technology of the Delft University of Technology, research work is carried out on problems in which multicomponent chemical reactions in a bifunctional catalyst environment are a principal element. Study of the interrelated effects of the many system parameters, as well as the search for possible opti maZ catalyst compositions to maximize output and yield, has made it desirable to have at hand a fast simulation of the reaction system. Hybrid computation appeared to be the logical way to meet the needs of the above Laboratory for easy man- machine interaction and high computation speed. In this report are presented the development and imple mentation of the hybrid simulation together with some of its results as realized at the Delft University Computation Centre. The hybrid model at present simulates a five-component reaction using a bifunc tional catalyst. Much effort has been invested to obtain both easy input/output and the highest possible speed of solution using an Applied Dynamics AD4, an IBM 1800, and interface equipment. How this was done is described in some detail.
Business games off the shelf
Authors: Eiloart Tim , Searle Nigel 
Published: March 2008

Computer-based modelling and simulation techniques are now enjoying widespread application. Computer programs for corporate financial planning and invest ment appraisal could provide the breakthrough in gaining acceptance for computers in the business world as machines capable of more than routine clerical work. The computer time-sharing services are in the forefront in providing these programs to the user. At present the models are being used to answer clear- cut "What if...?" questions (gut-feeling and experi ence are still needed in marginal cases). As yet, models capable of generating "optimum" solutions are still only in the research stage. Most commercial packages, however, do include sophisticated fore casting techniques, allowing the user to answer problems such as "What level of sales and monthly growth rate would be needed to double sales in three years?" All told, the arrival of routine models for business simulation is becoming the first tentative step in delegating social decision-making to machines--per haps the real beginnings of providing computer power for the public generally.
Digital and hybrid computer simulation of power systems
Authors: Carroll Dennis P. 
Published: March 2008

In order to meet the increasing demand for reliable design and expansion of power networks, the use of system simulation must play a leading role in the power industry's future R & D programs. Digital com puters are already widely used in the analysis and design of large power networks. Hybrid computers offer a convenient alternative, especially where fast and accurate simulation of complex nonlinearities is required. In this article, general principles are presented for the computer simulation of interconnected power systems. The technique discussed is directly applicable to an all-digital simulation, but emphasis is also placed on a hybrid implementation in which the transmission por tion of the system is represented digitally, while the integration and nonlinearities associated with termi nal apparatus are represented on the analog. Example studies are performed to illustrate the technique. Results include voltage waveforms for a three-phase line energization, and the modification of switching transients by surge arresters in a single-phase system.
Smooth
Authors: Sigal C. Elliott , Pritsker A. Alan B. 
Published: March 2008

SMOOTH is a packaged network simulation language written in FORTRAN. It is based on the GASP TV and GERT IIIZ simulation languages and is capable of representing and analyzing models which include both continuous variables and discrete events. As a net work language, SMOOTH consists of a set of graphical symbols, users' input instructions, and a computer program. The basic symbols are nodes and branches: nodes perform specified functions on system varia bzes, while branches indicate precedence or function aZ relations between nodes. In using SMOOTH, the user models the system he wishes to study as a pair of interrelated networks and then describes the net works to the computer by means of the SMOOTH lan guage's input instructions. The SMOOTH computer pro gram analyzes the netzoork using simulation. No com puter programming or sophisticated mathematical tech nique is required on the part of the user. This paper discusses the concepts and symbols of SMOOTH and includes as an example a SMOOTH model of a lake ecosystem. SMOOTH has been used to study biological systems, environmental pollution by trace metals and insecticides, and problems in systems dy namics. It is the first network simulation language capable of analyzing models of a combined continuous discrete nature.
Modified Merson's integration algorithm which saves two evaluations at each step
Authors: Chai Augustine S. 
Published: March 2008

This paper discusses a modified version of Merson's integration algorithm which can save two evaluations of the system at each step. For a complex system the saving in computing time may come to 40%. If you now use the ordinary Merson algorithm, you will find it easy to switch to the modified algorithm. The flow chart appended to this paper shows that switching to the modified algorithm involves adding on four blocks to Merson's method.
A mathematical model for the growth of giant kelp
Authors: Anderson Nick 
Published: March 2008

A computer model in FORTRAN for the growth of the giant kelp, Macrocystis, which inhabits the coastal waters of southern California, has been developed. The present model considers only physical factors, water temperature and submarine light, as the factors that control the growth of single fronds in large kelp beds. The model has been used to examine two aspects of kelp growth in water of 20 meters depth. The opti mum time of the year for the start of new growth of fronds arising from the bottom in an established kelp bed was found to be early June. The optimum time of the year for regrowth of harvested canopy was found to be early July. In each case, the optimum time is interpreted as providing the shortest time for the frond to reach "maturity" (a length of 40 meters). The penetration of sunlight into the hydrosphere is adversely affected by particulate matter in the water such as results from the introduction of sewage ef fluent. The simulation identifies the critical values for turbidity which will prevent new growth from occurring. At a depth of 20 meters, light absorbency of 18% per meter reduces the possible growing time by only 20%. But when absorbency is increased to only 24%, the growing time becomes zero. Simulation runs for other kelp-bed water depths revealed similar critical values of absorbency resulting in the restric tion of growth to shallower waters. This type of analysis to resource-management efforts is obvious. The paper concludes with suggestions for modifying the integration techniques used and for incorporating additional quantifiable values to refine the model.
Comparison of three methods for developing models of resource demand
Authors: Olver Leon A. , Burwell Brian H. , Brewer John W. 
Published: March 2008

This paper compares a new rather general modeling procedure with "static" and "dynamic" econometric procedures. The resulting models can all be used to make projections of demand for natural resources. If such models are combined with supply models, one can estimate the Long-term impact of resource policy. The particular resource discussed in this paper is natural gas in the Pacific Gas and Electric (PG&E) service area of California (large portions of the north and central sections of the state). Of the three modeling procedures discussed, the most general is emphasized in this paper. This method, described in Section 3, is related to the modeling procedure proposed by Forrester10,11 combined with parameter identification.2,19,30 A precise state ment and critique of the method is provided by Mitchiner et al.19 The other two modeling proce dures, chosen for purposes of comparison, are stan dard econometric methods. The first of these is a modification of "static" (algebraic) linear regres sion modeling. The second is a "dynamic" linear regression procedure wherein a lagged value of demand is used as one of the input variables.1,3,5 The proposed general methodology was not inferior to the two "standard" procedures in any case investigated and was clearly superior in the analysis of firm in dustrial demand for natural gas. This result was expected because the standard procedures are special cases of the proposed methodology.
DARE P—a portable CSSL-type simulation language
Authors: Lucas John J. , Wait John V. 
Published: March 2008

This paper describes a batch-mode FORTRAN-based continuous-system simulation Language that retains the features of the DARE family of languages1,2,3 but is structured to facilitate implementation on a wide variety of computer systems. Except for a small set of necessarily system-dependent routines (for character packing and unpacking, job abortion, etc.) the system is coded entirely in FORTRAN IV. It is highly modular, and uses system-independent FORTRAN-based methods for writing and manipulating solution files on mass storage. The system has thus far been run on a CDC-6400 (requiring about 21,000 decimal words of core memory), and a DEC-10 (requiring about 17,000 words). This paper announces the availability of DARE P, which we plan to make available to interested users who would like to implement it on their particular system, without the usual high surcharge that often accompanies other similar software packages. Our DARE IIIB, 3 which was specifically coded for the CDC-6000 series computers (including a COMPASS assembly-language translator overlay), was not portable. It has, nevertheless, been distributed and successfully used at many installations around the world. DARE P (Differential Analyzer REplacement- Portable) has been developed in response to requests for a version that would run on other computers. It is easy for the user to modify, e.g., he can easily add new integration rules, run-time strategies, or special library subprograms. DARE P can accommo date problems with 100 parameters and 200 state or output variables. In DARE P problem equations are entered in a form close to ordinary mathematical notation; the associ ated procedural language is FORTRAN. User-chosen variable names in the problem description are accommo dated by a special translator overlay which translates DARE problem statements into FORTRAN IV subprograms and builds a communication file. Run-time data is entered via free-form data cards. A variety of out put options are provided, including line-printer listings and plots, and CalComp plotter displays. Complete simulation studies may be directed by a FORTRAN-coded logic block. Single- or multiple-run problems may be specified with storage files used for saving output data for subsequent cross-plotting, reentry into future runs, etc. DARE P includes an internal collection of library functions, and the user may add his own special functions written in FORTRAN and his own one- or two-variable table-lookup function- generators. DARE P provides a choice of several internal fixed- and variable-step integration routines.
Applications of optimal control to the modeling and management of ecosystems
Authors: Vincent Thomas L. , Lee Cho Seng , Pulliam H. Ronald , Everett Lorne G. 
Published: March 2008

A complete ecosystem analysis may be possible from the point of view of optimal control theory. Such an analysis has three parts: (1) Determination of model structure (2) Determination of coefficients for a given model (3) Determination of optimal management programs for the model obtained by (1) and (2). The methods of optimal control theory are suitable for examining these three parts separately. The essential ingredients for each part is an optimization concept. Only the second and third parts are examined in detail here. For concreteness, a specific model structure for a prey-predator system is used. It is then shown that certain coefficients of this model are determined directly, given that the predator feeds in such a way as to maximize his caloric intake. By adding man's external controls to the model, the system can then be managed in a fashion to minimize some cost criterion. To illustrate this latter point, the methods of optimal control theory are used to determine a manage ment program for controlling water quality in a natural lake at minimum cost. Man's control is re presented by the application of an algacide on the phytoplankton-zooplankton (prey-predator) system in the lake. The introduction of temperature dependence as a driving force in a simple dynamical model appears to be adequate for the determination of the optimal control program.
Hybrid simulation of a gas-transport system using the directional- difference method
Authors: Buis J. Paul 
Published: March 2008

This report describes a hybrid simulation developed at the Hybrid Computation Department of the Delft University of Technology Computation Center in response to an order of the Dutch blast-furnaces and steel-mills industry, Hoogovens IJmuiden B.V., at IJmuiden, the Netherlands. The system to be simu lated is the gas-transport system used to carry blast furnace exhaust gases into a neighboring thermal power plant where the gas is used for the generation of electricity. The simulation is based on the use of the directional-difference method, which is used to solve the hyperbolic partial differential equa tions describing tube flow. Some attention is also devoted to the analysis of boundary values, and the approach toward a solution for this particular flow problem is outlined. The hybrid model is based on the cell-multiplexed method. The simulation showed that the system as originally designed could be marginal in certain respects. Some design changes were therefore incorporated in the simulation and it was rerun until a satisfactory operational performance of the gas-transport system was reached. The Hybrid Computation Department facility used for the implementation of the simulation consists of an Applied Dynamics AD-4 analog/hybrid computer and an IBM-1800 digital computer.
NEEDS: Nuclear Energy Electrical Demand Simulation
Authors: Willke Theodore L. 
Published: March 2008

A computer model is presented called NEEDS — an acro nym for Nuclear Energy Electrical Demand Simulation- which can simuZate the nuclear sector of the United States electric power economy. The code can forecast the impact of various nuclear-reactor growth patterns over the next fifty years in terms of economics, resource utilization, and the requirements for a supporting fuel-cycle industry. NEEDS was developed for the Office of Energy Research and Development Policy of the National Science Foundation as a tool to help evaluate alternative fission reactor develop ment strategies involving advanced reactor concepts, including advanced high-temperature gas-cooled reac tor (HTGR) systems, the gas-cooled fast reactor (GCFR), the molten-salt breeder reactor (MSBR), the Zight-raater breeder reactor (LWBR), and the heavy- water reactor (HWR) . The objectives of the study were to calculate the impacts, benefits, and require ments of various nuclear growth patterns and to determine the sensitivity of these measures to input parameters which are dominating, uncertain, or sub ject to wide variations.The NEEDS model is currently being used to answer such questions as: What benefits would the United States realize by developing the MSBR, the GCFR, or the LWBR as alternatives to the LWR/HTGR/LMFBR power economy? What are the potential impacts on enrich ment requirements and uranium demand of changing per cent tails assay? How does a power economy based upon a thorium-U233 fuel cycle compare with a pluto nium economy? The model has been used to relate the research-and-development requirements for developing an advanced reactor concept to the availability of the reactor system and its impact on the nuclear economy.In summary, the NEEDS model was developed to study questions of national nuclear policy using a simple modeling approach and minimal input data requirements. The model can forecast the impact of nuclear power development under selected national policy options and potential growth scenarios.