1978

Bibliography R.J. Mulholland, C.M. Gowdy and C.L. Cole: Modeling the effect of Atmospheric carbon dioxide on the global radiative heat balance. IEEE Transactions on Systems, Man and Cybernetics, Vol. SMC-7, 1977, November, pp. 803-805. H. Nasner and H.W. Partenscky: Modellversuche fur die Tide Elbe. Strombaumassnahmen nach 1962 und ihre Auswirkungen auf die Sturmflutwasscrstande. Mittleitungen des Franz&s-Instituts der Technischen Universitci’tHannover, Heft 45,1977, S. 37-178. C. Popeea and L. Lupas: Partial differential Riccati equation in designing adaptive optimal control systems. Advances in Computer Methods for Partial Differential Equations II (Ed. R. Vichnevetsky). Proceedings of the Second IMACS Symposium on Computer Methods for PDE, held at Lehigh University, Bethlehem, U.S.A., on June 22-24,1977; pp. 339344. The paper deals with the partial differential Riccatti type equation in designing separable adaptive control laws for linear systems with unknown parameters with respect to a quadratic performance cost. Special cases have been considered for illustrating the conditional stability of some classical integrating schemes. In designing adaptive optimal control laws for stochastic systems with unknown parameters significant simplications are possible under appropriate separability conditions which assure the independence of the covariance matrix from the observed data. Moreover, in the corresponding linearquadratic problem, a linear state feedback optimal control law is obtained and the optimal gain is determined as a function of the parameter estimates by means of a partial differential Riccati type equation. D.U. von Rosenberg, H.A. Thompson and F.Y. Tillery: Solution of the equations describing the dynamic response of a thick circular arch. Advances in Computer Methods for Partial Differential Equations II (Ed. R. Vichnevetsky). Proceedings of the Second IMACS Symposium on Computer Methods for PDE, Lehigh University, Bethlehem, U.S.A., June 22-24,1977;pp. 354-359. A set of three second order, non-linear, hyperbolic partial differential equations is used to describe the dynamic response of the thick circular arch. By the defintion of new variables, these equations are replaced by six first-order hyperbolic euquations. An efficient numerical solution of these equations is developed by the centered difference method.

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1978 A.A. Adamson, J .F. Kenney, A.L. Desell and L.L. Carver: Inclusion of inter-area transmission in production costing simulation. IEEE Transactions on Power Apparatus and Systems, Vol. PAS-97,1978, No. 5, September, pp. 1481-1488. Traditionally, production costing simulation programs have ignored intern area transmission restrictions which may, in actual daily system operation cause suboptimal system wide generating unit dispatch. With the advent of large scale pooling and operating agreements and concomitant pool wide economic dispatch, a need has arisen for system planners to be able te recognise transmission limitations in production costing studies. This paper presents a technique which allows such limitations to be considered. In addition, the paper outlines how this tool can be used to aid system planners in determining adequate inter-area transfer capacity and given relative system-wide transmission requirements for alternate generating unit siting strategies. G.C. Aers and A.D. Boardman: The optimum use of threedimensional computer-generated plots in the study of surface electromagnetic waves. Proceedings of the U.K.S.C. Conference on Computer Simulation, Chester, April 1978. IPC Science and Technology Press, G.B.; pp. 320-327. The dispersion curves of surface electromagnetic waves on conductors are usually investigated, theoretically, by assuming that frequency and wave number are entirely real. Experiments, on the other hand, use ATR (attenuared total reflection) systems in which frequency or angle of incidence of an electromanetic probe is scanned. This paper considers a freeelectron model of a metal in terms of computergenerated threedimensional plots of reflectance as functions of real frequency and angle. It will be shown that the perspective of the plots can be adjusted to give an optimum view of a ‘terrain’ detail once the broad features are revealed. Such plots can also reveal qualitative features of the complex frequency and/or complex angle solutions of the dispersion equation.

J. Steiner: Lagerhaltungsmodelle bei Variablem Periodendarf: Eine kritische Analyse und Erweiterungen praktisch eingesetzter Verfahren. Angewandte Informatik, Bd. 19, 1971, October, S. 415-421.

D. Al-Dabass and D.A. Rutherford: Simulation of a chain-line multiprocessor structure for continuous systems simulation. Proceedings of the U.K.S.C. Conference on Computer Simulation, Chester, April 1978, IPC Science and Technology Press; G.B., pp. 338-349. The computational requirements of the right-hand side of the general non-linear vector differential equation are examined, and a chain-like interconnection scheme for multiprocessors is developed. Special instructions are then proposed to speed up the organization of the solution and reduce data transfer times. Simulation at the machine state level is then carried out to test the chain control bus, the special instructions and the problem solution capability of the system. A 15th order room heating problem is used as an example.

W.J. Taylor: A dynamic satellite scheduling algorithm. Lincoln Lab., M.I.T., AD-A043636/0,1977, July, 20 pages.

A.C. Armstrong: Mathematical modelling opment in three dimensions. Proceedings

of landform develof the U.K.S.C.

64

Bibliography

Conference on Computer Simulation, Chester, April 1978. IPC Science and Technology Press, G.B.; pp. 328-337. The use of finite difference simulation techniques permits the modelling of the temporal sequence of landforms, where rates and directions of mass transport are a complex and spatially discontinuous function of the form of the land surface at any instant of time. Details of a model are briefly presented which models both the sequence of landforms and the development of the soil cover. Two sets of results are presented, under contrasting boundary conditions, which show that both the classic Davisian analysis and the more recent ‘dynamic equilibrium’ analysis of landforms are both special cases of a single more general model. A. Asthana: Design and control of a three-stage matrix in the presence of fan-out. IEEE Transactions on Computers, Vol. C-27, 1978, October, pp. 886-895. D.M. Auslander: A continuous-system simulation language designed for LSI economics. Mathematics and Computers in Simulation, Vol. XX, 1978, No. 4, December, pp. 308-313. As computing hardware gets cheaper, and labor gets more expensive, the economics of developing relatively limited distribution software such as continuous-system simulation languages for minicomputers (compared to Fortran and other system softwares) changes. A philosophy of low-cost software is propounded here, and an example of a language adhering to that philosophy is presented. It is an equationoriented language capable of solving differential or difference equations. It runs completely in memory (requires no mass storage device). Examples of its use are given, including a PHYSBE solution. P.W. Baker: A note on the second-order difference digital differential analysers. Digital Processes, Vol. 4, 1978, No. 2, pp. 163-170. L. Bakule: Two-level control generation of multiarea electric energy systems. Simulationof Control Systems (Ed. I. Troth). Proceedings of the IMACS Symposium, September 27-29, 1978, Technical University of Vienna; pp. 161-163. NorthHolland Publishing Company, Amsterdam, 1978. A new two-level feedback control algorithm is described. The design procedure is applied to the frequency and tie-line power control of multiarea electric energy system problem. The summary of the performed digital simulation is presented to illustrate the use of the design procedure. G. Bastin and M. Gevers: Joint use of space interpolation and optimization methods for steady-state aquifer modeling with scarce data. Modeling, Identificattion and Control of Environmental Systems (Ed. G. Vansteenkiste). Proceedings of the IFIP Working Conference, August 30-September 2, 1977, Ghent, Belgium; pp. 427-441. North-Holland Publishing Company, Amsterdam, 1978. G. Battermann: tal groundwater

Automatic calibration of a two layered digimodel. Modeling, Identification and Control

of Environmental Systems (Ed. G. Vansteenkiste). Proceedings of the IFIP Working Conference, August 30-September 2, 1977, Ghent, Belgium; pp. 443-456. North-Holland Publishing Company, Amsterdam, 1978. The calibration of a non steady-state groundwater model is divided into two steps. The first step is a steady-state calibration. An automatic procedure in form of a gradient method is used to adjust several sets of unknown parameters. The result shows similarity between measured and computed lines of equal groundwater head. The non-steady -state calibration is performed under the assumption of constant mean natural recharge in parts of the groundwater flow field. The uncertainties in the values of the determined parameters are discussed in an error analysis. M. Benahmed: Identification of the frictional slope in unsteady open channel flows using optimal control theory. Modeling, Identification and Control of Environmental Systems (Ed. G. Vansteenkiste). Proceedings of the IFIP Working Conference August 30-September 2, 1977, Ghent, Belgium; pp. 195-108. North-Holland Publishing Company, Amsterdam, 1978. E.W. Bergamini: The backward difference digital differential analyzer as a tool for signal processing. Proceedings of the U.K.S.C. Conference on Computer Simulation, Chester, April 1978. IPC Science and Technology Press, G.B.; pp. 350-359. With the advent of microprocessors and their matched, integrated peripheral devices, the digital implementation of complex algorithms, with different degrees of parallelism, has become attractive. The results presented in this paper can be used in real-time applications of microprocessors. The data were obtained with a class of backward difference digital differential analyzers - BDDDA’s based on multi-step predictor integration formulas. Optimized coefficient and transfer increment word lengths are given, in the sense that quantization and quadrature errors can be balanced. A register level organization of the integrating architecture is proposed with a natural ‘crescendo’ of complexity for higher orders of integration. A practical design example is discussed. J. Bernier and P. Lencioni: Un modele probabilistique multidimensionnel applicable a la description des processus hydrometeorologiques a l’echelle fine. La Houille Blanche, 1978, No. 6, pp. 401-410. S.I. Biryokov: Formalized schemata of making an economic plan IV. Computer simulation of economic planning schemata; Automatica i. Telemekhanika, 1978, No. 5, pp. 87-96 (in Russian). C.P. Bottura, Y. Burian Jr. and A.G. Palhares: Simulation of PID chopper control of a series motor. Simulation of Control Systems (Ed. I. Troth). Proceedings of the IMACS Symposium, September 27-29, 1978, Technical University of Vienna; pp. 157-158. North-Holland Publishing Company, Amsterdam, 1978.

Bibliography A chopper control system of a series motor on the traction mode, using a PID-PWM controller is studied through an analog-hybrid simulation, where some undesired phenomena are observed: chattering, subharmonic oscillations and pseudo-random oscillations. In addition, based on previous analytical results, a method of compensation to eliminate the periodic oscillation instabilities is proposed and implemented on the simulation. F. Bouille: Contribution to the simulation of data base access control. Simulation of Control Systems (Ed. I. Troth). Proceedings of the IMACS Symposium, September 27-29, 1978, Technical University of Vienna; pp. 107-l 12. NorthHolland Publishing Company, Amsterdam, 1978. A very large data bank model is a complex system which must be completely and carefully simulated before its effective implementation. The paper deals with some theoretical and practical aspects of the simulation of a general model which has been developed around the Hypergraph-Based Data Structure. This kernel is used to structure the data, to ensure the data bank system architecture and finally to design the simulation system. Other tools are simultaneously used, like the algorithmic language EXEL and some extended Petri nets named hyperschemas. The simulation and the implementation are written in SIMULA 67. No translation thus is necessary between the simulation and implementation steps. G. Braun: A water balance model for weighable lysimeters. Modeling, Identification and Control of Environmental systems (Ed. G. Vansteenkiste). Proceedings of the IFIP Working Conference August 30-September, 2, 1977, Ghent, Belgium; pp. 285-289. North-Holland Publishing Company, Amsterdam, 1978.

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meability both of which are linear, the system may be solved in one pass. When the permeability is a function of field strength an iterative solution is required. J.M. Chaiken: Transfer of emergency service displayment models to operating agencies.Management Science, Vol. 24, 1978, No. 7, March, pp. 719-731. T. Chambers: Some numerical techniques for use in a large digital simulator. Proceedings of the U.K.S.C. Conference on Computer Simulation, Chester, April 1978. IPC Science and Technology Press, G.B.; pp. 312-319. This paper describes some numerical techniques which are in use in the C.E.G.B. Advanced GasCooled Reactor Digital Simulator. This simulator is driven by a variable-step, variable-order stiff integration algorithm and the techniques described are part of the current attempt to provide real-time solutions to the differential equations describing the A.G.R. system. K. Chand and S.H. Charles: Approximate method for analyzing queueing network models of computing systems. Computing Surveys, Vol. 10, 1978, No. 3, September, pp. 281-310. I.F. Christie and R.W. Harbinson: Model tests of circular sewage sedimentation tanks. Proceedings of The Institute of Civil Engineering, Part 2, Vol. 65, 1978, pp. 71-84.

A.O. Brubakk and R. Aaslid: Use of a model for simulating individual aortic dynamics in man. Medical and Biological Engineering and Computing, Vol. 16, 1978, May,pp. 231242.

R.G. Coyle: Modelhng the future of mining groups. Proceedings of the 1978 U.K.S.C. Conference on Computer Simulation, Chester, April 1978. IPC Science and Technology Press, G.B.; pp. 235-246. The typical International Mining Company (IMC) is a cross between a merchant bank and a consulting firm and usually has only a minority equity stake in its operating companies, which are often large corporations themselves. The article shows how conflicts can arise between Head Office and subsidiaries and how what is good for the IMC is not necessarily good for the subsidiaries and vice versa. Traditionally, the mining industry has not engaged in corporate planning. The model shows that some obvious planning approaches may be harmful to the corporate entity.

P.E. Burke and J.D. Lavers: Resistance heating of circular billet - two simple analytic models. IEEE Transactions on Industry Applications, Vol. 14, 1978, No. 5, September/ October, pp. 433-437. Two simple models are presented for calculating the acdc resistance ratio and power factor of a resistance heated magnetic billet of circular cross section. The step-function magne_ tisation model yields a normalized acdc resistance ratio graph applicable to any homogeneous magnetic billet for which the magnetization characteristic is known. The coupled-circuit model yields a set of unidirectionally coupled algebraic equations that may be solved serially. For the case. of a billet of radially lnhomdgeneous conductivity and per-

R.G. Coyle: A corporate model for manufacturing company. Proceedings of the U.K.S.C. Conference on Computer Simulation, Chester, April 1978. IPC Science and Technology Press; pp. 247-262. Many corporate planning models either produce balance sheets or allocate investment over a time horizon on the assumption of price or demand forecasts. They are essentially static and do not trace out the interplay of corporate policy. This article, based on an actual project, discusses an alternative approach of building a dynamic, policy-design model. The model shows where policy conflicts can be expected and can be used to assess different managerial ‘styles’ for the firm.

The model simulates water movements in soil monoliths under consideration of special boundary conditions of lysimeters. The actual evapotranspiration for a grass cover is calculated as a function of a reduced Penman evaporation and the soil moisture tension in the root zone.

66

Bibliography

D. Danev and A. Kukleva: Transformation of control system mathematical models. Simulation of Control Systems (Ed. I. Troth). Proceedings of the IMACS Symposium, September 27-29, 1978, Technical University of Vienna; pp. 125-127. North-Holland Publishing Company, Amsterdam, 1978. A programme suite for transformation of the different forms of mathematical description for linear multivariable control systems is described. The main forms, from control theory point of view, rational polynomial matrix, polynomial system matrix, transfer function matrix and state space representation are transformed under strict system equivalence, system simularity into various special mathematical forms. D.P. de Graag: Plume hold-up calculations with the KSLA plume path model. Modeling, Identification and Control of Environmental Systems (Ed. G. Vansteenkoste). Proceedings of the IFIP Working Conference, August 30-September 2, 1977, Ghent, Belgium. pp. 393-399. North-Holland Publishing Company, Amsterdam, 1978. The KSLA plume path model, a procedure for calculation of the plume path of gasses emitted by a stack into an atmosphere with wind, has been extended with a method for calculating the hold-up of the air-pollutant mixture and the pollutant itself within two contours of specified concentrations. R. de Keyser and A.R. van Cauwenberge: Simulation and self-tuning control in a nuclear power plant. Simulation of Control Systems (Ed. I. Troth). Proceedings of the IMACS Symposium, September 27-29, 1978, Technical University of Vienna; pp. 187-195. North-Holland Publishing Company, Amsterdam, 1978. The paper describes the simulation and a control concept for the nuclear-thermal part of pressurized water reactor (PWR) power plant. A simplified model of the complex dynamics of a Belgian nuclear power plant is simulated on a hybrid computer. The control design is based on a rather simple mathematical lower-order model with unknown time-varying parameters, which are identified in real-time. A self-tuning controller was used and it is shown to have very interesting properties. G. Delory and H. Chestem: Programmed driving sequential machines by whole or fractional control. Simulation of Control Systems (Ed. I. Troth). Proceedings of the IMACS Symposium, September 27-29, 1978, Technical University of Vienna; pp. 139-141. North-Holland Publishing Company, Amsterdam, 1978. Nowaday’s automata remain based on old rules: the languages in use still demand that the sequential systems should be reduced to combinational equations, according to what was done on electromagnetic relays automatism schemes. These new products then are fruitless as regards studying automatisms, their only interest lies in their easy use due to absence of hard-wiring. The originality of this research consists in using a programming principle enabling to reduce the study of these systems to writing the specifications. The main idea was to use Petri nets not only for describing sequential

machines, but also for programming the system. The specifications can be described by two different ways: _ either by looking upon the global evolution of the system _ or by reducing the control to sub-controls. J.A.R. DOS Santos, H. Mokarzel and J.C.G. De Siqueira: Modelling of actual power station speed and voltage regulators for stability studies. Simulation of Control Systems (Ed. I. Troth). Proceedings of the IMACS Symposium, September 27-29, 1978, Technical University of Vienna, pp. 1655166. North-Holland Publishing Company, Amsterdam, 1978. The great interest that stability studies on interconnected power systems have for their operation and planning and the availability of computer programs that perform those studies using somewhat detailed system models make necessary the identification of the parameters of the actual power station regulators that are in operation. A method that could perform that identification without disturbing much the operation of the system even if having a poor accuracy would be very desirable. Such a method is discussed in this communication. A.A. Dickie and I.M. Ricketts: A comparison of thirteen numerical integration routines. Proceedings of the U.K.S.C. Conference, Chester, April 1978. IPC Science and Technology Press, G.B.; pp. 307-3 11. This paper is a report of work done in choosing a numerical integration method suitable for use in the minicomputer digital simulation language MIMESIS. G. Dieterich: A vector space approach to synchronous data transmission. Part I: Theory - leading to a learning receiver. Simulation of Control Systems (Ed. I. Troth). Proceedings of the IMACS Symposium, September 27-29, 1978, Technical Highschool of Vienna; pp. 99-101. North-Holland Publishing Company, Amsterdam, 1978. The fist part of the paper gives a new and consequent time domain description of some processes arizing within the field of fast synchronous data transmission. These processes are equalization and learning equalization, clock phase synchronization and learning clock phases synchronization. The consequent time domain description is based on functional analysis. It allows the theoretical design of a receiver that learns equalization and its own clock phase synchronization. If the concept of ergodicity is included in the theoretical design, the receiver learns even in the case of a disturbed data channel. M. Dosso and A. Carriere: Model for simulating the evolution of the chemical composition of a minerals-solution system and its application. Modeling, Identification and Control of Environmental Systems (Ed. G. Vansteenkiste). Proceedings of the IFIP Working Conference, August 30-September 2, 1977, Ghent, Belgium; pp. 253-268. North-Holland Publishing Company, Amsterdam, 1978. The model presented is based on the thermodynamic relationships which characterize the equilibrium relationships

Bibliography between minerals and solutions. It calculates from the composition of a given water, the distribution of simple and complex ions and the degree of saturation of the solution in relation to a large number of minerals and salts. It simulates the dissolution reactions of one or several minerals as well as the evaporation of the solution. The main application is the construction of a model of simulation of saline soils or solids liable to become saline. W. Duechting: Modeling and simulation of disturbed cell renewal control systems. Modeling, Identification and Control of Environmental Systems (Ed. G. Vansteenkiste). Proceedings of the IFIP Working Conference, August 30-September 2, 1977, Ghent, Belgium. pp. 587-603. North-Holland Publishing Company, Amsterdam, 1978. The present paper is an attempt to interpret normal and malignant cell renewal systems with the aid of computer simulation. First a macromodel is set up step by step, which makes it possible to describe in general the time behaviour of cells of a compartment when various environmental perturbations arise. Disturbances of the blood-forming cell system, e.g. the erythroleukemia, are given as an example. Parameter changes and structural alterations are made in a enlarged multiloop control model. The dynamics of the cell systems are studied by means of the block-oriented simulation language ASIM. The above versions of the model, are, however, unsuitable for studying a single cell on its way through the different compartments, nor can it be eradicated at any desired moment. Therefore, it was a further step to prepare a refined generalized control-loop model without the above mentioned disadvantages. The gained results prove that the simulated unstable cell renewal processes have a great similarity as to their behaviour to the dynamics of the growth curves of malignant cell renewal systems. Therefore, an interpretation that cancer diseases are unstable control loops is close at hand and should be verified by special experiments. E. Economakos: Distribution system voltage studies using simulation techniques (summary). Proceedings offhe Institution of Electrical Engineers, Vol. 125, 1978, No. 2, February, pp. 151-152. A problem very familiar to power-distribution engineers, namely, the distribution system voltage studies and regulation, is dealt with in this paper, Simulation techniques are used and models of the system and its loading are formed. The statistics of the load variations are considered and practical way for using them is suggested. A method of checking the feasability of any voltage regulation program is developed. If a program is feasible on optimal area for the regulation operation is determined via an optimization procedure. L.W. Emark: Computational implementation of on-line loadflow. IEEE Transactions on Power Apparatus and Systems, Vol. PAS-97,1978, No. 5, September/October, pp. 15231537. This paper describes a straightforward building method of initializing internal and external network system bus voltage

61

and power injection operating levels for subsequent steadystate system security evaluation of planned and unplanned network contingency outages. Outages are of the tine, tieline, generator, or load loss type. The program can handle the opening of bus tie or jumper connections and the isolation of a bus or string of buses from the main part of the network. The routine’s main advantage is the automatic redistribution and makeup of tie-line P(MW) and Q(Mvar) flows from the external network. This algorithm has been implemented on the Iowa Illinois Gas and Electric Company real-time control system; it is now under test and evaluation, and preliminary results are most favorable. N.A. Esepkina, B.A. Kotov, Yu.A. Kotov, A.V. Mikhajlov, V.Y. Petrun’kin and S.V. Pruss-Zhukovsky: Systeme hybride optique-numerique pour l’analyse spectrale des radiosignaux, Avtomatrija, 1978, No. 3, pp. 50-54 (en russe). A.H. Evers: Optimal control and sensitivity analysis of a chemical process. Simulation of Control Systems (Ed. I. Troth). Proceedings of the IMACS Symposium, September 27-29, 1978, Technical University of Vienna; pp. 177-180. North-Holland Publishing Company, 1978. The formation of glycine from chloroacetic acid and ammonia is considered. The optimal temperature profile in the reactor is computed using the Pontryagin’s minimal principle. By applying sensitivity relations, which gives a considerable saving in computer time, a sensitivity analysis is made for the process variables. K.H. Faso1 and M. Gronau: Modelling and simulation of a chemical-process plant blast-supply system. Simulation of Control Systems (Ed. I. Troth). Proceedings of the IMACS Symposium, September 27-29,1978, Technical University of Vienna; pp. 167-172. North-Holland Publishing Company, Amsterdam, 1978. The modelling and analog simulation of a compressor-fed pipe system which supplies a chemical-process plant are considered. Main purpose of the investigation is to obtain some information concerning the design of both the plant under consideration, and of similar plants, to recognize critical operation cases, and to outline the control algorithms. The investigated systems as well as the essential operation cases are described. The fundamental strategies of model building are discussed, and, as examples, the modelhng of a pipe section and the modelling of the compressor are explained. Some block diagrams are shown and a comparison of measured and simulated behaviour of the compressor is presented. R.A. Feddes and H. Zaradny: Numerical model for transient water flow in non-homogeneous soil-root systems with groundwater influence. Modeling, Identification and Control of Environmental Systems. (Ed. G. Vansteenkiste). Proceedings of the IFIP Working Conference, August 30-September 2, 1977, Ghent, Belgium; pp. 291-308. North-Holland Publishing Company, Amsterdam, 1978.

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Bibliography

An implicit finite-difference model was developed that describe transient water flow in a non-homogeneous soil-root system under influence of groundwater. Water uptake by roots is represented by a sink term which depends on soil moisture pressure head, effective rooting depth and maximum possible transpiration. Data obtained from field water balance studies of red cabbage on clay soil were compared with computed results for the period June 21 to October 31,1967. The present model is an improved and extended version of a previous model. It yields satisfactory results in predicting both cumulative transpiration and distribution of soil moisture content with depth. M.H. Frere: Models for predicting water pollution from agricultural watersheds. Modeling, Identification and Control of Environmental Systems (Ed. G. Vansteenkiste). Proceedings of the IFIP Working Conference, August 30-September 2, 1977, Ghent, Belgium; pp. 501-509. North-Holland Publishing Company, Amsterdam, 1978. K.S. Fu: Application of pattern recognition to environmental data interpretation and modeling. Modeling, Identification and Control of Environmental Systems (Ed. G. Vansteenkiste). Proceedings of the IFIP Working Conference, August 30-September 2, 1977, Ghent, Belgium; pp. 33-49. NorthHolland Publishing Company, Amsterdam, 1978. This paper reviews some recent topics in pattern recognition applied to environmental data interpretation and modeling. In decision-theoretic pattern recognition, four topics are presented: per-field classifications, cluster analysis and sequential partitioning procedure, feature selection, and estimation of misclassification. The synthactic approach to pattern recognition is then introduced and its application illusttated. Problems for further research are discussed. L. Gagliardi: Notes on mathematical models valid for the study of coasts erosion. Modeling, Identification and Control of Environmental Systems (Ed. G. Vansteenkiste). Proceedings of the IFIP Working Conference, August 30-September 2, 1977, Ghent, Belgium; pp. 233-242. North-Holland Publishing Company, Amsterdam, 1978. In this paper the causes of coasts erosion are examined, taking into special account the effect of tides, of streams, of waves and wind. The effect that man can have on erosion phenomena is then considered. Finally, the possibility to represent such phenomena by means of mathematical models is examined, also taking into account the possible applications that such models can actually have. A.J. Gilchrist and 0. Marjasoo: Simulation of a specific class of packet switched computer network. Proceedings of the U.K.S.C. Conference on Computer Simulation, Chester, April 1978. IPC Science and Technology Press, G.B.; pp. 360-370. The authors are involved in a programme of research into a subset of computer communication networks. As part of this programme a network model has been constructed and a simulator developed. The simulator is to be used to study the

performance and reliability of the selected subset of This paper outlines significant features of packet computer networks and describes a network model. and link parts of the model are detailed. Some novel gramming features of the simulator are described.

network. switched Node pro-

W. Gitt and H. Herrmann: Determination of locus curves for model parameters and control lay-outs by digital simulation with optimization. Simulation of Control Systems (Ed. 1. Troth). Proceedings of the IMACS Symposium, September 27-29, 1978, Technical University of Vienna; pp. 129-130. North-Holland Publishing Company, Amsterdam, 1978. The steady increase in computerized control of physical, chemical, and technical processes has led to a continuously growing importance of control plant modelling. The parameters of a suitable control plant model being given, process algorithms - enabling an optimum ‘Driving style’ - can be developed. Complicated control loops can be ruled and analyzed by means of a specially developed simulation package. The special advantage of this digital simulation consists in the optimization possibility inherent in the system. L.A. Grinshpan: Modkle mathematique des cofits de systeme dans les complexes de calcul i plusieurs machines. Avtomat. vychislit., 1978, No. 4, pp. 76-80 (en russe). S.P. Hallam: Towards a portable simulation language - DSL 77. Proceedings of the U.K.S.C. Conference on Computer Simulation, Chester, April 1978. IPC Science and Technology Press, G.B.; pp. 215-222. Many users of Simulation Languages have neither the inclination nor the time to familiarise themselves with the complexities of modern computer operating systems. It is therefore desirable to provide, for the user of such a language, a degree of isolation from that operating system. Conflicting with this requirement is the need for implementing the same simulation language on diverse computers, in order that users in different establishments may exchange simulation models. This paper describes the language DSL 77 and the problems encountered in making the language available on different computers. K.F. Hanauer: A vector space approach to synchronous data transmission. Part 2: Simulation on a hybrid computer. Simulation of Control Systems (Ed. I. Troth). Proceedings of the IMACS Symposium, September 27-29,1978, Technical University of Vienna; pp. 103-105. North-Holland Publishing Company, Amsterdam, 1978. This second part of the paper describes a hybrid computer simulation of a synchronous data transmission system. The theoretical concept is given in part one. This simulation verifies two facts: (1) the theoretical concept is a realistic one in that sense that a technical system - e.g. a hybrid computer can work accordingly to it, (2) a hybrid computer is a tool that is just appropriate for solving problems in the field of synchronous data transmission.

Bibliography C.J. Harris: Minimum variance control, estimation and simulation of nonlinear models of wastewater-treatment systems. Proceedings of the Institution of Electrical Engineers, Vol. 125, 1978, No. 5, May, pp. 441-446. A problem of increasing importance is that of efficient regulation of wastewater-treatment systems. In the paper a set of model equations for the activated-sludge process are derived and shown to be nonlinear. They are It6 stochastic differential equations for which analytic solutions are not treatable. A fist-order simulation algorithm based on the properties of Itq calculus is used to validate the model equations and assess various control schemes. In particular, a minimum variance-control law is investigated: the structure of the controller is selected a priori on the basis of case of physical implementation and cost. The derived control is a statefeedback law. Implementation of the controls requires online knowledge of the system states and a new nonlinear discrete recursive state estimator based on the statistics of the system equations is introduced. Although the paper highlights the control of wastewater systems, the technique of simulation, minimum variance control and state estimation introduced are of very general applicability. T. Hasse: An iterative method for solving an exact initial value problem of the second order by a hybrid computer. Mathematics and Computers in Simulation, Vol. XX, 1978, No. 4, December, pp. 301-307. Many problems of engineering are described only by great non-linear systems of differential equations. Their equations often have a similar structure. Usually such problems cannot be solved by an analogue computer because the capacity of such a computer is too limited. In this paper an iterative method, based on the principle of the successive approximation, will be given which will enable the solution of non-linear systems of differential equations of any size by a hybrid computer under certain conditions. The method can be applied to initial value problems of the second order but modified for those of a higher order also. L. Hay: The portability of continuous simulation languages. Proceedings of the U.K.S.C. Conference, Chester, April 1978. IPC Science and Technology Press, G.B.; pp. 285-293. There are many problems associated with transferring programs from one machine to another. The paper discusses the problem of designing the ISIS interactive simulation language in a portable form and the difficulties encountered during implementation on various machines. The experience obtained also bears on the more general problem of writing portable FORTRAN software. A number of techniques are presented which assist in writing portable software and a future solution is suggested in the form of a new FORTRAN based portable language. A preprocessor technique is proposed as the means for converting the new language code to an appropriate FORTRAN dialect. P. Hebrard, P. Magre and G. CoIlin: Analyse et modelisation de l’ecoulement dans un foyer de turbomachine. La Recher-

the akrospatiale, 1978, No. 5, septembre/octobre, 249.

69 pp. 233-

A. Hoeld and D. Beraha: A non-linear digital simulator for BWR nuclear power plants within the scope of the application of optimal digital control methods. Simulation of Control Systems (Ed. I. Troth); Proceedings of the IMACS Symposium, September 27-29, 1978, Technical University of Vienna; pp. 181-186. North-Holland Publishing Company, Amsterdam, 1978. A non-linear digital simulator for BWR nuclear power plants and the digital code LIMBO based on this model will be derived. Comparative calculations to start-up tests at a large BWR nuclear power plant will demonstrate the efficiency of the code. Its application within the concept of linear optimal load-following control methods (with a quadratic performance index to be minimized) will be discussed and resulting transients of a load-following procedure for a realistic test case over a large operational range of the plant presented. W.M. Holmes: Large-scale air defense weapon simulation in the US Army’s advanced simulation center. Proceedings of the U.K.S.C. Conference on Computer Simulation, Chester, April 1978. IPC Science and Technology Press, G.B.; pp. 371-372. This paper describes three major areas of simulation development related activities in the US Army Missile Research and Development Command’s Advanced Simulation Center: (1) The simulation environment - State of technology environments for infrared (IR), eletrooptical (EO), and radio frequency sensors using hardware models; (2) Methodology of multiple large-scale, time-critical missile simulation development using a simulation language based approach; (3) Research results in establishing a ‘ Figure-of-Merit’ for validating simulating models using a sparse data base. P. Hopewell and C. Rix: An application of GPSS in a large simulation package. Proceedings of the 1978 U.K.S.C. Conference on Computer Simulation, Chester, April 1978. IPC Science and Technology Press, G.B.; pp. 229-234. It is widely acknowledged that the use of a specialist simulation language can substantially reduce development time when writing simulation programs, but that these savings may be more than offset by increased running costs when the program is intended to have widespread and frequent use. This paper describes an application of GPSS in a large simulation package. It discusses the factors leading to the original decision to use GPSS and considers, in retrospect, whether the decision was justified. A. Ichikawa: Prediction and simulation of river water quality by using G.M.D.H. Modeling, Identification and Control of Environmental Systems (Ed. G. Vansteenkiste). Proceedings of the IFIP Working Conference, August 30-September 2, 1977, Ghent, Belgium; pp. 79-87. North-Holland Publishing Company, Amsterdam, 1978.

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Bibliography

A number of methodologies are presented for the development of simulation models of water quality in river systems; models that describe the day to day variation and account for the inevitable uncertainties, such as extreme value just after the intense rainfall. The Tama river is central and vital to the densely populated area of Tokyo Metropolitan District. The discussion presented here deals with the simulation of water quality in Tama river by using the GMDH method. It is concluded that the GMDH method is the strong tool of the simulation for the river water quality, not only the index governed by physical models, but also the complex phenomena such as BOD (Bio-chemical oxygen demand) by some adjustment of model. H. Jaschek and M. Seiermann: Modelling and simulation of a nuclear power plant with a boling water reactor. Simulation of Control Systems (Ed. I. Troth). Proceedings of the IMACS Symposium, September 27-29, 1978, Technical University of Vienna; pp. 197-201. North-Holland Publishing Company, Amsterdam, 1978. In this paper a model for simulating the dynamic behaviour of nuclear power stations with single-loop boiling water reactors on analog computers is presented. After a description of the plant design the evaluation of the system equations is illustrated by the example of the nuclear subsystem. Some simulation results are presented and discussed. The validity of the model is demonstrated by comparison with measurement results from an actual power station. A.T. Johns and M.M.T. El-Kater: Developments in techniques for simulating faults in e.h.v. transmission systems. Proceedings of the Institution of Electrical Engineers, Vol. 125, 1978, No. 4, April, pp. 221-229. S.E. Jorgensen: Eutrophication models. Modeling, Identification and Control of Environmental Systems (Ed. G. Vansteenkiste). Proceedings of the IFIP Working Conference, August 30-September 2,1977, Ghent, Belgium; pp. 473500. North-Holland Publishing Company, Amsterdam, 1978. The eutrophication of lakes is controlled by a number of processes which involves that management of the water quality in lakes is possible only by application of models. Several different models have been applied for control of the eutrophication. All the referred models have the same structure. Mass balances are set up by means of several differential equations, however, they differ by the equations used for the description of the processes. The paper covers the following items: 1. Which processes have been included in eutrophication models? 2. Which equations have been used for description of these processes? 3. How were the models calibrated and validated? 4. Which processes need to be further investigated to be able to describe them sufficiently accurately for the eutrophication model. Based upon the review of the above mentioned four items, the following important question has been discussed: how is it possible to select a model which can be used to solve a specific eutrophication prob-

lem? Unfortunately,

only very few eutrophication

models

have been validated against observations obtained by changed nutrient loading of lakes. It seems necessary to get such information before an answer to the questions can be found, although it is possible with the present knowledge to give some indications. T.N. Keefer and H.E. Jobseon: River transport modelling for unsteady flows. Proceedings of the AXE, Journal of the Hydrological Division, Vol. 104, 1978, No. HYS, May, pp. 636647. M. Klenke: Simulation of groundwater level changes caused by time dependent boundary conditions. Modeling, Identification and Control of Environmental Systems (Ed. G. Vansteenkiste). Proceedings of the IFIP Working Conference, August 30-September 2, 1977, Ghent, Belgium; pp. 457469. North-Holland Publishing Company, Amsterdam, 1978. A hybrid computer model to calculate two dimensional groundwater flow is presented. The model can be applicable for both confined and unconfined aquifers. A finite element method is chosen to transform the PDE into a system of ODE’s, It is solved by analog integration using an iterative block method. To reduce the necessary iteration steps the difference of the solution functions between the n-th and the n+l-th step is weighted by an accelerating factor. Because of a resulting efficiently problems.

very good rate of convergence, the model can be applied to a wide class of dynamic groundwater

Y. Kobayashi, N. Ohkita and M. Inoue: Fractional power approximations of elliptic integrals and Bessel functions. Mathematics and Computers in Simulation, Vol. XX, 1918, No. 4, December, pp. 285-290. In previous papers, fractional powers were used to approximate elementary functions and their usefulness was proved with experimental results. In the present paper, some further investigations are reported. That is, elliptic integrals in Legendre’s canonical form and Bessel functions are approximated by fractional powers. As the fractional power approximation, f(x) = CO+ clx + czxp is discussed. When all coefficients ca cl, ~2, p are properly assigned, the accuracy of this approximation becomes comparable to that of the Chebyshev approximation using polynomials up to the third degree. J.G. Kretzschmar, G. de Baere and J. VanderVee: The immission frequency distribution model of the S.C.K./C.E.N. Mol, Belgium. Modeling, Identification and Control of Environmental Systems (Ed. G. Vansteenkiste). Proceedings of the IFIP Working Conference, August30-Sepember 2, 1977, Ghent, Belgium; pp. 379-391. North-Holland Publishing Company, Amsterdam, 1978. It is shown that the Immission Frequency Distribution Model is able to simulate the actual air pollution conflguration of sources of different kind and magnitude. Once the model has been validated it is possible to define the contribu-

Bibliography tion of each individual source, or each group and type of sources, as well as to simulate the effect of possible changes in that source configuration. As such the model becomes a powerful tool for urban planning and air polution abatment as well in the nuclear as the nonnuclear field. J.D. Lavers, P.P. Biringer and R.L. Quinn: Mathematical modeling in the design of large electric smelting furnaces. IEEE Transactions on Industry Applications, Vol. IA-14, 1978, No. 5, September/October, pp. 415-420. The problem of scaling a slag resistance electric smelting furnace from the pilot plant stage to a full size production unit is considered. Several of the existing scaling methods are discussed with a view to point out their limitations. It is shown that some are clearly inappropriate for the scaling process since they neglect significant factors that influence the furnace performance. Among these factors are the finite furnace geometry, the nonhomogeneous slag, and the slag/ alloy interface. Methods of including these factors in the analysis are described. In particular a finite difference simulation has been developed for the furnace. Such a model can be used to derive design parameters for the furnace and to indicate the manner in which such parameters vary with furnace geometry. J .D. Lavers, P.P. Biringer and R.L. Quinn: A mathematical model describing forces and circulation in an electric smelting furnace. IEEE Transactions on Industy Applications, Vol. IA-14, 1978, No. 5, September/October, pp. 421-426. Conditions in the slag bath of an electric smelting furnace are examined as are several existing models for such furnaces. A digital model that provides an improved simulation of the slag bath is described. The model is used to determine the electrical resistance between electrodes and can be used to examine the nature of the electromagnetic forces that exist near the electrode tips. The mechanism by which these forces produce bath circulation is described. J.D. Lavers: An efficient method of calculating parameters for induction and resistance heating installations with magnetic loads. IEEE Transactions on Industry Applications, Vol. IA-14, 1978, No. 5, September/October, pp. 427-432. An efficient method of solving one-dimensional linear or nonlinear induction and resistance heating problems is described. Previous methods have formulated these problems in terms of matrix equations that can require a considerable amount of computer storage during solution. The method described avoids the matrix formulation. Rather, the solution proceeds in a step-by-step fashion so that when fields are calculated, at a point within the conductor, the previously calculated fields at other points are utilized. In this sense, the solution requires only a minimum of storage capacity and is particularly appropriate for small desk calculators. The linear hollow cylinder problem has been programmed for the HP-25 calculator. S.T.Y. Lee and C. Deschamps: Mathematical model for economic evaluation of tidal power in the bay of Fundy. IEEE

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Transactions on Power Apparatus and Systems, Vol. PAS-97, 1978, No. 5, September/October, pp. 176991778. The mathematical models for the economic evaluation of tidal power development involving a primary and secondary markets are presented in the context of utilities generation expansion planning. The approach is to determine the economic benefits of tidal power by difference in the least-cost expansion plans with and without tidal development. The least-cost expansion plans are derived by a series of snapshot year simulation and generation mix optimization. The impact of storage devices ans transmission between market area are properly studied. These models have been successfully applied to the study of tidal power in the bay of Fundy. W.W. Lee, Y.Y. Kuo and H. Okuda: Numerical simulations of collisionless drift instablities for lowdensity plasmas. The Physics of Fluids,Vol. 21, 1978, No. 4, April, pp. 6177626. Nonlinear behavior of the collisionless drift instabilities are studied for the universal and current drives modes by means of electrostatic particles simulations in two-and-a-half dimensions. Realistic mass ratios of electrons to the ions are used in the simulations, where the guiding-center approximation for the electrons and the exact dynamics for the ions are employed. Several nonlinear effects including the quasi-linear diffusion of the particle density, the frequency shift due to the ambipolar field, the mode competition among the unstable waves, and the quasi-linear diffusion in the velocity space are found to be dominant mechanisms for the saturation. The stabilization of the collisionless drift instabilities by the magnetic shear has also been studied. M.E. Leesley and H.S. Pollicoff: Comparing CONCEPT and FLOWTRAN using a process simulator evaluator. Computeraided Design, Vol. 10, 1978, No. 5, September, pp. 289294. D.O. Lomen: A model of diffusion and convection of pollutants from a point source. Modeling, Identification and Con trol of Environmental Systems (Ed. G. Vansteenkiste). Proceedings of the IFIP Working Conference, August 30-September 2, 1977, Ghent, Belgium; pp. 361-378. North-Holland Publishing Company, Amsterdam, 1978. M. Mader and P. Wehrli: Modeling of a reservoir. Modeling, Identification and Control of Environmental Systems. (Ed. G. Vansteenkiste). Proceedings of the IFIP Working Conference, August 30-September 2, 1977, Ghent, Belgium; pp. 219-229. North-Holland Publishing Company, Amsterdam, 1978. For the dynamic behavior of the water level of a laboratory reservoir model built in the representative fraction of l/$00, a nonlinear mathematical model of second order is proposed. The unknown parameters of the differential equations are determined with the help of a powerful identification package which allows parallel model adjusting by an output error method. Measurements taken from the physical model are used as inputs to the programs. For the behavior of the system around a nominal water level a linear model is derived.

72

Bibliography

A. Malowski: Finite element concept in state identification of large scale distributed parameters systems. Modeling, ldentification and Control of Environmental Systems (Ed. G. Vansteenkiste). Proceedings of the IFIP Working Conference, August 30-September 2,1977, Ghent, Belgium; pp. 61-77. North-Holland Publishing Company, Amsterdam, 1978. This paper presents the problem of an appropriate state identification for linear space-distributed environmental systems in the case of incomplete information about the system. Formulation of the problem was based on the model of dynamics and observations of the systems in question as well as on the proposed identification quality index. Using finite elements concept minimization of the weighted squared index is transformed into large scale dynamic optimization problem in time domain. In the case of low dimensionality the sequential identification algorithm is generated by variational and invariant imbedding methods. In the case of very large dimensionality the problem is treated by multilevel optimization technique. R.E. Manley: The use of a hydrological model in water resources planning. Proceedings of the Institute of Civil Engineering, Part 2, Vol. 65, 1978, June, pp. 223-235. N.C.G. Markatos and D.G. Tatchell: Computer simulation of compressible, three-dimensional turbulent rocket-plumes. Proceedings of the U.K.S.C. Conference on Computer Simulation, Chester, April 1978. IPC Science and Technology Press, G.B.; p. 372. The flow of a jet issuing from the exhaust of a rocket, travelling at subsonic or supersonic speeds, into the surrounding atmosphere, is very complicated and involves, apart from gas dynamics and turbulence, many other processes as chemical reactions, particle behaviour and radiation. The present paper is concerned with the computational aspects of predicting such flows. Some preliminary solutions are presented. The results compare well with existing simple solutions and appear to be qualitatively correct. It is demonstrated that the calability now exists for calculating 30 flows of this type. However, further work is required, to test the physical realism of the solutions by making comparisons with experimental data. H. Markiewicz and Z. Wroblenski: Matematycznofizyczy model preziawodnosci stycznikow elektromagnetycznych pradu przemiemvego (Mathematical physical model of reliability of alternating current electromagnetic contactors. Archiwutn Elektrotechniki, Tome XXVII, 1978, No. 1, pp. 115-132. F. Masszi: Computer-aided design of MOS/LSI circuits device and functional models. Electrical Engineering, Vol. 22, 1978, No. 1,pp. 13-25. The computer-aided design of MOS/LSI circuits is very important for modern microprocessors. A MOS transistor model is introduced taking secondorder effects into consideration, and an example is given for functional macromodel-

ling. A MOS R-S flip-flop macromodel describing the inner functioning of the original flip-flop only at logical levels but equivalent to the original R-S circuit from the point of view of the outer circuit and having simpler circuitry than the original is presented. The models were integrated to the TRANSTRAN non linear circuit analysis program, and also sole results of LOS/L% circuit details transient analysis are shown. D. McLaughlin: Parameter estimation problems in water resource modeling. Modeling, Identification and Control of Environmental Systems. (Ed. G. Vansteenkiste). Proceedings of the IFIP Working Conference, August 30-September 2, 1977, Ghent, Belgium; pp. 137-151. North-Holland Publishing Company, Amsterdam, 1978. The problem of estimating unknown model coefficients from uncertain field measurements occurs in nearly any practical water resource modeling application. In this paper, a general stochastic model is used to describe and compare alternative parameter estimation technique. Statistical methods for dealing with questions of model complexity, parameter sensitivity and experimental design are also briefly examined. Several important concepts are illustrated with a practical hydrologic modeling example. R.K. Mehra: A survey of time series modeling and forecasting methodology. Modeling, Identification and Control of Environmental Systems (Ed. G. Vansteenkiste). Proceedings of the IFIP Working Conference, August 30-September 2, 1977, Ghent, Belgium, pp. 3-32. North-Holland Publishing Company 1978. This paper surveys some of the fundamental problems and approaches used in Time Series Analysis, System Identification, and Forecasting. In particular, the state vector models and their estimation are discussed. Other topics included are tests for nonstationarity, Kalman filters, and their extensions, model structure determination, for multiinput-multioutput linear systems, parameter estimation, and model validation. Certain application results on economic time series are presented to illustrate the state space modeling approach. B. Mellitt, C.J. Goodman and R.I.M. Arthurton: Simulator for studying operational and power-supply conditions in rapid-transit railways. Proceedings of the Institute of Electrical Engineers, Vol. 125, 1978, No. 4, April, pp. 298-303. The paper describes the development of a computer based simulator which may be used to study the relationships between tram movements and power-supply conditions in a 2-road rapid-transit railway. The work was specifically undertaken to enumerate the energy saving consequent on the introduction of copper-controlled traction-control equipment with regenerative-braking capacility. In the simulator, track topology and signaling constraints are represented by a sequential block structure which is analogous to the fixedblock signaling arrangements. Tractive characteristics of the traction equipment are represented by precessive linearized models and a complete power-network solution is obtained at

Bibliography each update period. The simulator is written in extended Fortran IV and is reasonably efficient in computer processing time; e.g. running 1 h service at 90 s headway on a 5 km section of track typically requires 4 min of central processor time on an ICL 1906 A. Simulating 20 km of double track, with up to 100 trains per track, typically requires 36 Kwds of core. Although the simulator was developed specifically for energyconsumption calculations, the methods of representation are quite general. The simulator may thus be used to study other problems of interest in train performance and signailing studies. B. Mellitt, C.J. Goodman and R.I.M. Arthurton: Simulation studies of energy saving with chopper control on the Jubilee line. Proceedings of the Institution of Electrical Engineers, Vol. 125, 1978,No. 4, pp. 304-310. The paper describes energy-consumption studies undertaken for the operation of rapid-transit services on London Transport’s new Jubilee line. The object of the studies was to provide comparative figures for the energy consumption of a chopper-controlled fleet and a conventionally equiped rheostically-controlled fleet. The work was undertaken using a digital computer simulator in which train movement and power-network calculations are interdependent. The approach permits the evaluation of system constraints when regenerative breaking is used in conjunction with the usual, plain diode, noninverting type of substation. Detailed figures are provided for various services operating on a short 5 km isolated power block section of the line and also for a peak and off-peak services on the whole line. Sensitivity experiments on this 5 km section demonstrate the dependence of energy reduction on the opportunities to transfer energy between trains, on the line voltage limit and on the traction equipment specification. These figures reflect the use of a low characteristic traction motor and the moderate proportion of breaking energy available for potential regeneration (52% of total breaking effort for an average loaded tram).

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K. Nadesalingam and D.R. Towill: Frequency domain fault detection and diagnosis in hybrid control systems: a feasible study. IEEE Transactions on Instrumentation and Measurement, Vol. IM-27, 1978, June, pp. 193-199. M. Nanard, A.M. Massotte and J.R. Galea: Un modele d’evaluation de performances prenant en compte l’agencement des entrees-sorties. RAIRO, Informatique - Computer Science, Vol. 12, 1978,No. 1, pp. 3-14. Cet article resume les principes et rappelle les experiences de validation d’un modele original d‘cvaluation de pcrformantes des systemes d’exploitation. 11 pcrmet de prendre en compte I’influencc des methodes d’E/S et plus particulercment l’influence des tampons d’E/S, sur le comportement des systemcs, en traduisant le recouvrement mutuel des activi& de calcul et d’E/S au sein d’un m&me programme. Les modeles usuels i r&au de file d’attente ne prenncnt pas en comptc ce phenomene. Ce mod&e considere indepcndamment les appels superviseurs de demande d’E/S (EXCP) et de test de realisation d’E/S (WAIT) et determine le taux d’utilisation dc l’unite centralc en fonction des proprietes chronologiques moyennes de ces appels. B.E. Okah-Avae: Analogue computer simulation of a rotor system containing a transverse crack. Simulation, Vol. 3 1, 1978, No. 6, December, pp. 193-198. This paper describes the analogue computer simulation of a complete rotor and bearing system. The physical equations of motion of the rotor with its shaft are derived in rotating coordinates and those of the bearings in stationary coordinates. The system is modelled to have four degrees of freedom, taking into consideration the flexibility, damping, and cross-coupling of the hydrodynamic bearings. The model can be reduced to two degrees of freedom by assuming that the rotor is rigidly supported. The simulation of a transverse fatigue crack in the rotor shaft is presented and its effect on the dynamic response of the system is breafly examined.

R. Mezencev and R. Lepeix: Hybrid simulation of a non linear hydropneumatic damper for ships. Simulation of Control Systems (Ed. I. Troth). Proceedings of the IMACS Symposium, September 27-29, 1978, Technical University of Vienna; pp. 135-137. North-Holland Publishing Company, Amsterdam, 1978. It is proposed to reduce the amplitude of vibrations produced by the propeller in ships structures by means of a hydropneumatic damper. These vibrations are of variable frequency depending of the velocity. The damper is automatically tuned by means of a pump which modifies its resonance frequency. The simulation must make easy the choice of the dimensions of the damper components. A general hybrid software offers many facilities for this simulation.

T.I. Oren: A personal view on the future of simulation languages. Proceedings of the U.K.S.C. Conference, Chester, April 1978. IPC Science and Technology Press, G.B.; pp. 294-306. After a brief review of the broad scope of simulation, some simulation concepts are clarified and features of simulation languages are discussed. Apparent and/or desirable possibilities for the future of simulation languages are then outlined under the following categories: Language definition, implementation, computational environment, modelling formalism, modelling, algorithmic handling of models, experimentation, integration, optimization, algorithmic manipulation of experimentation specifications, displaying the results, and challenges.

A. Morse and W. Kilmer: A neural net capable of competitive and cooperative computation, Biological Cybernetics, Vol. 30,1978, No. 1, pp. l-6.

V.V. Osipov and D.D. Nedosekin: Principe de controle fonctionnel d’un calculateur hybride i temps reparti. Izvest. vyssh. uchebn. Zaved. Elektromekh, 1978, No. 4, pp. 441444 (en russe).

74

Bibliography

N. Paldor, A. Nir and S. Lewis: Use of simulation as an aid in parameter identification of a lake ecosystem. Modeling, Identification and Control of Environmental Systems (Ed. G. Vansteenkiste). Proceedings of the IFIP Working Conference, August 30-September 2, 1977, Ghent, Belgium; pp. 183193. North-Holland Publishing Company, Amsterdam, 1978. Lake ecosystem models usually include several unknown parameters. Their identification is an essential step in the application of these models. The models are, however, nonlinear in system variables and parameters which leads to nonuniqueness of parameter determinations using the existing search algorithms. We examine this problem through simulation of the behavior of several models with initial parameter values selected randomly in the expected range of the true values. We investigate the uniqueness of the identification and the dependance of the mean and variance of the parameters obtained on the quantity and quality (error) of the simulated data and on the error in the initial values of the search procedure. Possible criteria for acceptance of a true identification or rejection of a false one include convergence of initial value to itself, independance on the sequence in the identification algorithm and robustness to noise in data. N.L. Paliwal, J. Nanda and P.S. Satsangi: State-space modelling of a series compensated long distance transmission system through graph-theoretic approach. IEEE Transactions on Power Apparatusand Systems, Vol. PAS-97, 1978, No. 5, September/October, pp. 1646-1655. The paper demonstrates a powerful application of graphtheoretic approach in developing a linearized state-model for a typical hydropower system effectively and systematically. The linearized d-q state models of basic components of power system as generator, transformer, transmission line are formulated (conceptually in isolation) in a synchronously rotating frame which permit ease of interconnection without involving any intermediary or axis transformations. The formulation of model in general, is applicable to multimachine system and is easily amenable to digital simulation. It is hoped that the system state-model formulation through graph theoretic approach would strongly appeal to power system engineers engaged in large scale comprehensive dynamical system studies. L. Panattoni and E. Todini: Finite differences over non regular fields. Modeling, Identification and Control of Environmental Systems (Ed. G. Vansteenkiste). Proceedings of the IFIP Working Conference August 30-September 2, 1977, Ghent, Belgium; pp. 347-352. North-Holland Publishing Company, Amsterdam, 1978. A new technique for the numerical solution of partial differential equations, which extends the capability of the finite difference methods to the handling of two dimensional non regular fields, was recently presented by Gallati and Panattoni. (1977). Its basic concept refers to the computation of the gradient of the function fix, y) in a given point by means of the

values the function assumes in the point itself and in the surrounding ones. In the previous paper only a first order approach was considered; in this paper a second order scheme is discussed and tested over a simple case study, for which the theoretical solution is known. The results are compared also with the fist order ones. J.-F. Peyrucat: Sachez selectionner votre convertisseur numerique-analogique. Electronique et applications industrielles, 1978, No. 253, 15 mai, pp. 21-27. H.S. Price: cal model Computer 47, AFIPS

The development of application of a mathematiof enhanced oil recovery. AFIPS 1978 National Conference, Anaheim, Ca., June 5-8, 1978, Vol. Press, Montivale NJ, 1978, pp. 53-62.

K.K. Raabtsev: M&moire-tampon pour l’adaptation d’un canal analogique-numerique avec un ordinateur. Izuest. vyssh. uchebn. Zaved., Elektromekh., 1978, No. 6, pp. 592-594 (en russe). W. Ravenscroft and J.M. Sordaan: Model studies for the Swakopoort dam. International Water Power and Dam Construction, Vol. 30, 1978, No. 12 December, pp. 48-49. G. Renner: Computer simulation of the temperature and electromagnetic field in an inductively heated semiconductor. Mathematics and Computers in Simulation, Vol. XX, 1978, No. 1, March, pp. 28-36. The electromagnetic and temperature fields in an inductively heated semiconductor interact with each other in a sophisticated way through the heat dependence of the material parameters and the heat source density determined by the eddy currents. The paper deals with a computer analysis of the interacting fields taking into account the nonlinear temperature dependence of the material parameters. The basic electromagnetic and heat conduction equations are discussed, and a transformation will be introduced for the calculation of electromagnetic field outside the material. The nonlinear equation system resulting from discretization is solved by an iterative method, whose relaxation factor is optimized during the iteration. Experiences gained in the course of numerical calculations are reported, and results of calculation performed with specific physical data are described. C.J. Richards: What’s wrong with my model. Proceedings of the U.K.S.C. Conference on Computer Simulation, Chester, April 1978. IPC Science and Technology Press, G.B.; pp. 223-228. An important practical problem, rarely mentioned in the literature is that of ‘debugging’ a digital computer simulation model. When dealing with relatively small models the causes of particular behaviour can often be deduced from the original mathematical formulation or the code used to implement the model. For larger models the problems are formidable. This paper describes some relatively simple techniques developed at the CEGB Computing Centre to aid the user in

Bibliography

debugging a model. Not only do these reveal errors made in coding of the model but also enable faults in the original mathematical formulation to be discovered. J.R. Rogers: Simulation of groundwater withdrawal effect upon urban subsidence and flooding. Modeling, Identification and Control of Environmental Systems (Ed. G. Vansteenkiste), Proceedings of the IFIP Working Conference, August 30-September 2,1977, Ghent, Belgium; pp. 243-252. North-Holland Publishing Company, Amsterdam, 1978. D.I. Saletan: Shell development hosts Southwestern Simulation Council. Simulation, Vol. 31, 1978, No. 6, December, p. 199. G.M. Scheider: A modelling package for simulation of computer networks. Simulation, Vol. 31, 1978, No. 6, December, pp. 181-192. The VANS (Value Added Network Simulator) system represents a new approach to the simulation of distributed resource-sharing computer networks. It allows the network designer either to manipulate the structure of the protocols (sets of rules) that govern the handling of communications in different types of networks or to investigate the effect of changing the parameters of networks operating under a fixed set of protocols. This paper describes the VANS system and its use in conducting a wide range of experiments in the network design. While a number of simulation programs permit experimenting with network parameters, VANS is the first to permit both that type of experimentation with the protocols that control the operation of a computer network. U. Scholer: Simulation as an instrument for energy planning. Proceedings of the U.K.S.C. Conference on Computer Simulation, Chester, April 1978. IPS Science and Technology Press, G.B.; pp. 263-272. On behalf of the European Communities the system analysis group of the Kernforschungsanlage Jillich has developed a dynamic energy model which can be used as a common instrument for energy planning for the countries of the European Communities. In this paper the characteristic elements and the overall structure of this simulation model are described. Furthermore some examples of applications of the model are given for the Federal Republic of Germany as a pilot country. P. Schroeder: Problems in the modelling of groundwater basins with a generalised Darcy law. Modeling, Identification and Control of Environmental Systems (Ed. G. Vansteenkiste), Proceedings of the HIP Working Conference, August 30%September 2,1977, Ghent, Belgium; pp. 413-426. North-Holland Publishing Company, Amsterdam, 1978. G.M. Seidel and P.S. Chandhoke: Spatially discrete models of counter-current mass transport for application to the kidney. Mathematics and Computers in Simulation, Vol. XX, 1978, No. 4, December, pp. 259-270.

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Within the kidney the transport of many solute species and water is accomplished by the parallel operation of several counter-current transport systems. The simulation of these processes requires the solution of a nonlinear, two-point boundary value problem with many simultaneous equations. Standard formulations of the problem involve the solution of a set of onedimensional, plug-transport equations. Rather than seek an accurate solution of this spatially continuous model, which is only an approximation to the real system, we investigate spatially discrete analogs. The motivation for use of spatially discrete models is to simulate with much more efficiency the detailed simultaneous transport processes of many solutes and water. The membrane flux equations of these models describe solvent drag as well as passive and active transport of solutes. In this study we investigated a perfectly mixed compartment model and an improved Euler (semidiscretiaed) model. The solutions of these models were compared to the numerical solution of a standard spatially continuous model. For efficient numerical solution of the continuous model, the equations were arranged to yield a band matrix structure and a triangular decomposition procedure was applied. The model solutions were compared for convergence, efficiency, and accuracy for a variety of parameter values. With membrane parameter values typical of tubule segments of the rat kidney, a spatial step size as large as 1 mm (roughly one-seventh the length of the renal medulla of the rat) was found to be suitable for both discrete models. M. Shima, I:. Delebecque and N. Adachi: A dynamic model of quality of river water with consideration of nitrification process. Modeling, Identification and Control of Environmental Systems (Ed. G. Vansteenkiste). Proceedings of the IFIP Working Conference, August 30-September 2, 1977, Ghent, Belgium; pp. 5 11-526. North-Holland Publishing Company, Amsterdam, 1978. A dynamic model of water quality of river, in which nitrification processes are taken into account, is presented. The behaviour of the model is investigated numerically and discussed with reference to the experimental results by Edeline and Lambert. It is shown that high DO deficit is caused by nitrification for the wide ranges of parameters in the model. T.M. Simundich: Application of pattern recognition to water resource modeling. Modeling, ldentication and Control of Environmental Systems (Ed. G. Vansteenkiste). Proceedings of the IFIP Working Conference August 30-September 2, 1977, Ghent, Belgium; pp. 5 l-60. North-Holland Publishing Company, Amsterdam, 1978. M.W.A. Smith and A.P. Roberts: A Kalman filter type of extension to a deterministic gradient technique for parameter estimation. Mathematics and Computers in Simulation, Vol. XX, 1978, No.4, December,pp.291-300. It is shown that a method for the identification of deterministic systems derived from the Kalman filter is related to a gradient technique of parameter estimation and that the range of problems to which the gradient method may be

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Bibliography

applied is thereby extended. Various versions of the discretetime algorithm are compared from theoretical and computational points of view and also contrasted with the continuous time algorithm. An important outcome is that the system containing unknown parameters and the identification algorithm may be formulated with one in discrete time and the other in continuous-time. L. Socha and J. Skrzypek: Application of open loop control to the determination of optimal temperature profiles for reversible reactions. Simulation of Control Systems (Ed. I. Troth). Proceedings of the IMACS Symposium, September 27-29, 1978, Technical University of Vienna; pp. 173-175. North-Holland Publishing Company, Amsterdam, 1978. In the paper a method of the determination of the optimal temperature profile in the chemical reactor for reversible reaction which is described by stochastic differential equation is presented. G.H. Sockut: A performance model for computer data-base reorganisation performed concurrently with usage. Operations Research, Vol. 26,1978, No. 5, September, pp. 789804. W.D. Stirling: The use of a procedure-oriented language for processoriented simulation. Software - Practice and Experience, Vol. 8,1978, No. 2,pp. 137-148. W. Stpeniewski and K. Grabowiecki: A bond graph approach to the automated generation of equations of motion of lumped parameter systems. Simulation of Control Systems (Ed. I. Trocj). Proceedings of the IMACS Symposium, September 27-29, 1978, Technical University of Vienna; pp. 121-123. North-Holland Publishing Company, Amsterdam, 1978. The bond graph technique has been adopted to develop a new digital computer program GEM for the automatic generation of nonlinear state space equations. A general structure of the program is presented and an example of bond graph topological data required by the program for a typical pumping unit of a realistic gas turbine control system is given. H. Tamura and T. Mochizuki: Nonstationary statistical system identification method for river quality modeling. Modeling, Identification and Control of Environmental Systems (Ed. G. Vansteenkiste). Proceedings of the IFIP Working Conference, August 30-September 2, 1977, Ghent, Belgium; pp. 17 1- 182. North-Holland Publishing Company, Amsterdam, 1978. This paper deals with statistical system identification for river quality modeling using nonstationary time series of BOD-DO observations and the amount of effluent discharge in each reach of the river. For this purpose a nonstationary statistical system identification method is newly developed. This method can estimate both the order and the parameters of the distributed-lag model for river quality systems. The criterion used for estimating the order of the model is AlIen’s PSS (Prediction sum of squares) which has been used for

variable selection in the stepwise multiple regression analysis. A numerical example for the Yomo river in Japan is included by using synthetic data. H. Theuerkauf: Digital simulation of convertor-fed AC drives using modular models. Simulation of Control Systems (Ed. I. Troth). Proceedings of the IMACS Symposium, September 27-29,1978, Technical University of Vienna; pp. 151-156. North-Holland Publishing Company, Amsterdam, 1978. In view of the complicated circuitry of a AC drive employing static power convertors it becomes increasingly difficult to make predictions of the dynamic behaviour and the electrical stresses of individual sections and components. In such cases it is of interest to perform a digital simulation using a mathematical model prior to experimental development work. Using a modular structure of the simulation program it is possible to exchange parts of the models to create new configurations of drives. This ensures that the mathematical model is easily adaptable during the development process. As an illustration of this method some simulation results of convertorfed asynchronous motor drives are shown compared to measurements at an experimental setup. P. Till and G. Tsamis: Computer simulation of thermal systems by network-analysis programs. Simulation of Control Systems (Ed. I. Troth). Proceedings of the IMACS Symposium, September 27-29, 1978, Technical University of Vienna; pp. 131-133. North-Holland Publishing Company, Amsterdam, 1978. Network-analysis programs generally are developed for the analysis of electric and electronic circuits considering small signal response. This programs (e.g. ASTAP, SYSCAP) also successfully may be used for the simulation of the large signal response of power electronic circuits of thermal systems. Mainly the authors applicate the network-analysis programs to the simulation of twodimensional transient temperature distributions. R. Tomkins: A system dynamics model of the U.K. Economy, Proceedings of the U.K.S.C. Conference on Computer Simulation, Chester, April 1978. IPC Science and Technology Press, G.B.; pp. 273-284. We are currently developing a system dynamics model of the UK economy. The paper describes the feedback structure of a nine subsystem model. The model’s dynamic processes arise from disequilibrium conditions; the adjustment mechanisms have been formulated from an analysis of behavioural processes. Preliminary simulation results are discussed briefly. Yih-0 Tu: Calculation of demagnetizing field by means of FFT. Mathematics and Computers in Simulation, Vol. XX, 1978, No. 4, December, 271-284. The demagnetizing field due to magnetization prescribed on a set of Cartesian mesh points in a flat film is solved by means of the Fast Fourier Transform (FFT), the magnetization and the magnetostatic potential are Fourier transformed over planes parallel to the film. Integration of the boundary

Bibliography value problem for the potential in the transform functional space is then carried out across the thickness faciliatated by a recurrence formula. Finally, the demagnetizing field may be Fourier represented. G. Vohr: Simulation of a system that is described by a statistical nonlinear differential equation. Simulation of Control Systems (Ed. I. Troth). Proceedings of the IMACS Symposium, September 27-29, 1978, Technical Highschool of Vienna; pp. 113- 115. North-Holland Publishing Company, Amsterdam, 1978. This paper describes a method to reduce the mean timedelay in a digital communication system that works with serial bit and byte data transfer. Because of the mathematic complexity in treating such a data link, the proposed method was simulated in a hybrid combination of a microprocessor and an analogue computer. The given results show the possible improvement, when this data coding is compared with the common coding technique. C. Weisang and H. Jaschek: Multiconductor transmission line macromodelling to simulate the behaviour of a high tension DC line unit. Simulation of Control Systems (Ed. I. Troth). Proceedings of the IMACS Symposium, September 27-29, 1978, Technical University of Vienna; pp. 145-150. NorthHolland Publishing Company, Amsterdam, 1978. The following paper described the development of a multiconductor transmission line macromodel for the simulation of high tension DC line units. A mathematical formalism is given to describe the behaviour of a line with a non perfect earth connection by a set of independent modes. The model parameters and the element values of the equivalent network are evaluated by a separate computer program. A special celladdressing procedure enables the timedelay storage and allows the handling of up to five transmission lines with and without initial values. A macromodelling procedure is also used to simulate the behaviour of the converters in the transforming plant. The computer runs are carried out with the well known SCEPTRE network and system analysis program. This approach allows a flexible description of different physical structures connected with the high tension DC line unit. The simulation example of the switching on of a complex power system demonstrates clearly that the proposed approach provides accurate results in a reasonable solution time. A. Wexler: Implementation of finite element methodology to the solution of boundary integral equations. Modeling, Identification and Control of Environmental Systems (Ed. G. Vansteenkiste). Proceedings of the IFIP Working Conference August 30-September 2,1977, Ghent, Belgium; pp. 353359. North-Holland Publishing Company, Amsterdam, 1978. This paper describes the application of the isoparametric finiteelement method to the solution of boundary integral equations. The method is an extension of an efficient procedure used in the solution of partial differential equations. The technique permits high-order description of boundary

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shapes and surfaces variables (e.g., potential, its normal derivatives, etc.). The boundary integral method has always been considered to produce dense matrices unless approximations of an ad hoc nature are made. It is shown that this is not the case and that sparse matrices can be generated. In addition, the paper describes an algorithm for mixing partialdifferential and boundary-integral equation approaches. F.D. Whisler: Problem dependent soil water flow models. Modeling, Identification and Control of Environmental Systems (Ed. G. Vansteenkiste). Proceedings of the IFIP Working Conference, August 30-September 2, 1977, Ghent, Belgium; pp. 309-3 16. North-Holland Publishing Company, Amsterdam, 1977. The flow problem dictates the level of sophistication necessary in the model development. For models that only need the amounts of water entering or leaving the soil profile but which are used to simulate years of real time, algebraic types of equations are used. For more complicated models where the water content within the profile or plant root zone is needed, but one year of plant growth is to be economically simulated, a Darcy flow water balance equation can be used. For detailed analysis of specific flow systems numerical solution of the Richards’ equation is required. PG. Whitehead: Modeling and planning of environmental studies. Modeling, Identification and Control of Environmental Systems (Ed. G. Vansteenkiste). Proceedings of the IFIP Working Conference, August 30-September 1, 1977, Ghent, Belgium; pp. 527-556. North-Holland Publishing Company, Amsterdam, 1978. The techniques of systems provide a broad integrative approach to the planning and management of environmental studies. Dynamic stochastic models of environmental systems offer a concise description of data and the discipline of developing simple robust models can aid in defining study objectives, determining important control variables, establishing data collection and analysis procedures and the testing of management and control strategies. Systems analysis is discussed in the paper with reference to the problems of modeling estuarine systems, with a particular application in Western Port Bay, and to an ongoing study of water quality and eutrophication processes in the Murrutiidgee-Burrinjuck Lake system near Camberra. B. Wiegele: Computer assisted learning of methods and problem solving in control engineering. Simulation of Control Systems (Ed. I. Troth). Proceedings of the IMACS Symposium, September 27-29, 1978,Technical University of Vienna; pp. 117-119. North-Holland Publishing Company, Amsterdam, 1978. A concept for introduction, training and assistance to the methodology of analysis, synthesis and system simulation in control engineering by means of a computer is presented. The concept, established in some program modules on a general purpose computer consists of libraries with dialogue programs, exercices, information and graphic routines for the

Bibliography

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solution of control engineering problems. It allows an utilization by unexperienced users for learning and training as well as by experienced users mainly for assistance in problem solving. Such control engineering methods become better accessible to a large class of applicants than is presently the case. B.W. Williams: State-space computer triac model. Proceedings of the Institution of Electrical Engineers, Vol. 125, 1918, No. 5, May, pp.413-415. The paper presents a state-space dynamic model for a bidimensional silicon controlled rectifier (the triac). The model exhibits programmable and controlable static and dynamic properties for a triac in all four modes of electrical operation. Computer-simulated transient electrical results of a pulse width modulated arc chopper are in excellent agreement with results obtained experimentally. .I. Wisniewski and J. Branowski: Zmiennopradowy model zastepczy wzmacniacza operacyjnego (Alternating current equivalent model of the operational amplifier). Archiwum Elektrotechniki Tome XXVII, 1978, No. 103, pp. 101-114. P. Young: General theory of modelling for badly defined systems. Modeling, Identification and Control of Environmental Systems (Ed. G. Vansteenkiste). Proceedings of the IFIP Con ference, August 30-September 2, 1977, Ghent, Belgium; pp. 103-135. North-Holland Publishing Company, Amsterdam, 1978. M. Zeiner, W. Jentsch and W.Jud: ASIM 3 - ein System zur digitalen Simulation Kontinuierlicher Systeme. Wiss. Ber. AEG-Telefunken, Bd 21,1978,Nr. 1, S. 15-24.

1979 L. Blank: A simulator for multilevel distribution systems. Simulation, Vol. 32, 1979, No. 2, February, pp. 54-62. This article describes the use of simulation to design 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 forecast at each level based on demand data which is randomized in accordance with empirical distributions. In the manufacturing capacities, which in the simulation are userspecified, are too small to meet the demand, the model adjusts the distribution schedule. Each warehouse is provided the opportunity to purchase some fraction of its demand for any item from a local independent supplier on a routing basis and on an extra-purchase basis when the manufacturer cannot supply the item through his distribution centers. The article discusses model validation and an application of the simulator to determine the optimum number and the locations of storage facilities and to improve inventory control.

B. Chaumontet: Calculateur analogique a traitement numerique applique i l’exploitation en temps reel des rcsultats d’experiences. Application de l’operateur rapide AM 9511 associe i un 8080 pour l’etude de diagrammes de compresseurs, la visualisation de la pression intraventriculaire, la simulation d’un turbomoteur. Electronique et Applications industrielles, 1979, No. 268, mai, pp. 55-57. R. Eising: Low-order realizations for 2-D Transfer Functions. Proceedings of the IEEE, Vol. 61,1979, No. 5, May, pp. 866-868. In this note, a realization result for casual 2-D transfer functions with separable numerator or separable denominator is generalized. A possible dimension of the local state space will be determined and system matrices will be given. J.M. Geist: Computer generation of correlated Gaussian random variables. Proceedings of the IEEE, Vol. 61, 1919, No. 5, May, pp. 862-863. This paper presents a means of generating a set of N correlated Gaussian random variables from N or fewer independent Gaussian random variables. In computer generation of pseudorandom variables, this technique sometimes has computational advantages over the more straightforward inverse Gram-Schmidt procedure. As an example, application of the technique in simulation of a pulse frequency modulation (PFM) receiver is discussed. H.J. Halin: Integration across discontinuities in ordinary differential equations using power series. Simulation, Vol. 32, 1979, No. 2, February, pp. 33-44. Numerical integration of ordinary differential equations containing nonanalytical functions is error-prone and timeconsuming. Because of this problem, the simulation of the hydraulic servo drive of a machine tool produced unsatisfactory results. However, applying power-series expansion provided fast and accurate solutions. Due to its piecewise semianalytic character, this method is particularly suited to handling discontinuities. Although it requires the calculation of higher derivatives by means of recursion formulas. A simulation package for this purpose is currently under development. Two examples compare its performance with that of RungeKutta-Merson integration . S.W. Lang and J.H. McClellan: A simple proof of stability for all-pole linear prediction models. Proceedings of the IEEE, Vol. 67,1979, No. 5,May, pp. 860-861. A simple method of proof is presented for the minimumphase property of the all-pole model obtained in the autocorrelation method of linear prediction. The proof does not require knowledge of Levinson’s recursion and extends easily to some special cases of the covariance method of linear prediction. A.B. Langdon: Analysis of the time integration in plasma simulation. Journal of Computational Physics, Vol. 30, 1919, No. 2, February, pp. 202-221.