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  • 1
    Electronic Resource
    Electronic Resource
    OLYMPUS a standard control and utility package for initial-value FORTRAN programs
    Amsterdam : Elsevier
    Computer Physics Communications 7 (1974), S. 245-270 
    Details
    ISSN: 0010-4655
    Keywords: General purpose ; computation ; control ; framework ; initial-value problems ; kernel ; package ; simulation ; standard ; utility
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Computer Science , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0010-4655(74)90026-5
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  • 2
    Electronic Resource
    Electronic Resource
    A general purpose Monte-Carlo program
    Amsterdam : Elsevier
    Computer Physics Communications 9 (1975), S. 360-369 
    Details
    ISSN: 0010-4655
    Keywords: Monte-Carlo ; Nuclear ; high energy ; random ; simulation ; statistics
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Computer Science , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0010-4655(75)90016-8
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  • 3
    Electronic Resource
    Electronic Resource
    A program for the analytic simulation of extensive air showers
    Amsterdam : Elsevier
    Computer Physics Communications 7 (1974), S. 344-352 
    Details
    ISSN: 0010-4655
    Keywords: Astrophysics ; cosmic rays ; extensive air showers ; hadrons ; high energy ; nuclear ; nuclear cascade ; simulation
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Computer Science , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0010-4655(74)90032-0
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  • 4
    Electronic Resource
    Electronic Resource
    Algorithms for random sampling from single-variate distributions
    Amsterdam : Elsevier
    Computer Physics Communications 46 (1987), S. 427-436 
    Details
    ISSN: 0010-4655
    Keywords: Monte Carlo method ; acceptance-rejection method ; generation of random deviates ; random sampling ; simulation
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Computer Science , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0010-4655(87)90096-8
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  • 5
    Electronic Resource
    Electronic Resource
    A universal generator for discrete log-concave distributions (1994)
    Springer
    Computing 52 (1994), S. 89-96 
    Details
    ISSN: 1436-5057
    Keywords: 65C10 ; 68C25 ; Random number generation ; log-concave distributions ; rejection method ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Wir erklären einen Algorithmus, der Stichproben von beliebigen log-konkaven Verteilungen (z.B. Binomial- und Hypergeometrische Verteilung) erzeugt. Er basiert auf Verwerfung von einer diskreten dominierenden Verteilung, die aus Teilen der geometrischen Verteilung zusammengesetzt wird. Der Algorithmus is gleichmäßig schnell für alle diskreten log-konkaven Verteilungen und nicht viel langsamer als Algorithmen, die nur für eine bestimmte Verteilung verwendet werden können.
    Notes: Abstract We give an algorithm that can be used to sample from any discrete log-concave distribution (e.g. the binomial and hypergeometric distributions). It is based on rejection from a discrete dominating distribution that consists of parts of the geometric distribution. The algorithm is uniformly fast for all discrete log-concave distributions and not much slower than algorithms designed for a single distribution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02243398
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  • 6
    Electronic Resource
    Electronic Resource
    An alias method for sampling from the normal distribution (1989)
    Springer
    Computing 42 (1989), S. 159-170 
    Details
    ISSN: 1436-5057
    Keywords: Primary 65C10 ; Random numbers ; normal distribution ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Die effizientesten Algorithmen für Stichproben von der Standardnormalverteilung benötigen lange Listen von Konstanten. Die Größe dieser Tafeln wächst mit der verwendeten Präzision. Durch eine Anpassung der “Aliasmethode” von A.J. Walker an die Normalverteilung wird eine Stichprobenprozedur entwicklet, die nur drei feste Tafeln von je 128 Bytes braucht. Die neue Methode ist ebenso schnell wie ihre Konkurrenten und leichter zu implementieren.
    Notes: Abstract The most efficint algorithms for sampling from the standard normal distribution require long lists of constants. The size of these tables grows with the employed precision. By adapting A.J. Walker's “alias method” to the normal distribution a sampling procedure is developed which needs only three fixed tables of 128 bytes each. The new method is as fast as its competitors and easier to implement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02239745
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  • 7
    Electronic Resource
    Electronic Resource
    A simple algorithm for generating random variates with a log-concave density (1984)
    Springer
    Computing 33 (1984), S. 247-257 
    Details
    ISSN: 1436-5057
    Keywords: Random variate generation ; simulation ; log concavity ; inequalities
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Wir legen einen kurzen Algorithmus zur Erzeugung von Zufallsveränderlichen mit log-konkaver Dichtef aufR mit bekanntem Median-Wert vor. Die mittlere Anzahl der erforderlichen Operationen ist unabhängig vonf. Die log-konkaven Dichtefunktionen beschreiben u. a. die Normal-, Gamma-, Weibull-, Beta-, Potenzexponential- (alle mit Formparameter mindestens 1), Perks- und Extremwert-Verteilung.
    Notes: Abstract We present a short algorithm for generating random variates with log-concave densityf onR and known mode in average number of operations independent off. Included in this class are the normal, gamma, Weibull, beta and exponential power (all with shape parameters at least 1), logistic, hyperbolic secant and extreme value distributions. The algorithm merely requires the presence of a uniform [0, 1] random number generator and a subprogram for computingf. It can be implemented in about 10 lines of FORTRAN code.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02242271
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  • 8
    Electronic Resource
    Electronic Resource
    Uses and abuses of statistical simulation (1988)
    Springer
    Mathematical programming 42 (1988), S. 53-68 
    Details
    ISSN: 1436-4646
    Keywords: Design of experiments ; normal random variates ; pseudorandom ; simulation ; statistical inference
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract More and more problems are being tackled by simulation as large computing costs per hour approach those of mathematicians' time. Abuses of simulation arise from ignorance or careless use of little understood procedures, and some of the fundamental tools of the subject are much less well understood than commonly supposed. This is illustrated here by the saga of pseudorandom number generators, normal variate generators and the analysis of queueing system simulations. On the positive side, genuinely new uses of simulation are appearing, particularly in statistical inference. These are exemplified by recursive algorithms for simulating complex systems and simulation-based likelihood inference for point processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01589392
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  • 9
    Electronic Resource
    Electronic Resource
    Property preserving abstractions for the verification of concurrent systems (1995)
    Springer
    Formal methods in system design 6 (1995), S. 11-44 
    Details
    ISSN: 1572-8102
    Keywords: abstract interpretation ; simulation ; property preservation ; model-checking
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract We study property preserving transformations for reactive systems. The main idea is the use of simulations parameterized by Galois connections (α, γ), relating the lattices of properties of two systems. We propose and study a notion of preservation of properties expressed by formulas of a logic, by a function α mapping sets of states of a systemS into sets of states of a systemS'. We give results on the preservation of properties expressed in sublanguages of the branching time μ-calculus when two systemsS andS' are related via (α, γ)-simulations. They can be used to verify a property for a system by verifying the same property on a simpler system which is an abstraction of it. We show also under which conditions abstraction of concurrent systems can be computed from the abstraction of their components. This allows a compositional application of the proposed verification method. This is a revised version of the papers [2] and [16]; the results are fully developed in [28].
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01384313
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  • 10
    Electronic Resource
    Electronic Resource
    A central-limit-theorem version ofL=λw (1986)
    Springer
    Queueing systems 1 (1986), S. 191-215 
    Details
    ISSN: 1572-9443
    Keywords: Queueing theory ; conservation laws ; Little's law ; limit theorems ; statistical estimation ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Underlying the fundamental queueing formulaL=λW is a relation between cumulative processes in continuous time (the integral of the queue length process) and in discrete time (the sum of the waiting times of successive customers). Except for remainder terms which usually are asymptotically negligible, each cumulative process is a random time-transformation of the other. As a consequence, in addition to the familiar relation between the with-prob ability-one limits of the averages, roughly speaking, the customer-average wait obeys a central limit theorem if and only if the time-average queue length obeys a central limit theorem, in which case both averages, properly normalized, converge in distribution jointly, and the individual limiting distributions are simply related. This relation between the central limit theorems is conveniently expressed in terms of functional central limit theorems, using the continuous mapping theorem and related arguments. The central limit theorems can be applied to compare the asymptotic efficiency of different estimators of queueing parameters. For example, when the arrival rateλ is known and the interarrivai times and waiting times are negatively correlated, it is more asymptotically efficient to estimate the long-run time-average queue lengthL indirectly by the sample-average of the waiting times, invokingL=λW, than it is to estimate it by the sample-average of the queue length. This variance-reduction principle extends a corresponding result for the standard GI/G/s model established by Carson and Law [2].
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01536188
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  • 11
    Electronic Resource
    Electronic Resource
    Stationary waiting time derivatives (1992)
    Springer
    Queueing systems 12 (1992), S. 369-389 
    Details
    ISSN: 1572-9443
    Keywords: Perturbation analysis ; stability ; stochastic difference equations ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract We investigate the stability of waiting-time derivatives when inputs to a queueing system-service times and interarrival times-depend on a parameter. We give conditions under which the sequence of waiting-time derivatives admits a stationary distribution, and under which the derivatives converge to the stationary regime from all initial conditions. Further hypotheses ensure that the expectation of a stationary waiting-time derivative is, in fact, the derivative of the expected stationary waiting time. This validates the use of simulation-based infinitesimal perturbation analysis estimates with a variety of queueing processes. We examine waiting-time sequences satisfying recursive equations. Our basic assumption is that the input and its derivatives are stationary and ergodic. Under monotonicity conditions, the method of Loynes establishes the convergence of the derivatives. Even without such conditions, the derivatives obey a linear difference equation with random coefficients, and we exploit this fact to find stability conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01158809
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  • 12
    Electronic Resource
    Electronic Resource
    Reliable estimation via simulation (1995)
    Springer
    Queueing systems 19 (1995), S. 169-192 
    Details
    ISSN: 1572-9443
    Keywords: Continuity ; rates of convergence ; robust estimation ; queueing systems ; simulation ; regenerative processes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Leta ands denote the inter arrival times and service times in aGI/GI/1 queue. Let a(n), s(n) be the r.v.s. with distributions as the estimated distributions ofa ands from iid samples ofa ands of sizesn. Letw be a r.v. with the stationary distribution π of the waiting times of the queue with input(a,s). We consider the problem of estimatingE[w α], α〉 0 and α via simulations when (a (n),s(n)) are used as input. Conditions for the accuracy of the asymptotic estimate, continuity of the asymptotic variance and uniformity in the rate of convergence to the estimate are obtained. We also obtain rates of convergence for sample moments, the empirical process and the quantile process for the regenerative processes. Robust estimates are also obtained when an outlier contaminated sample ofa ands is provided. In the process we obtain consistency, continuity and asymptotic normality of M-estimators for stationary sequences. Some robustness results for Markov processes are included.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01148945
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  • 13
    Electronic Resource
    Electronic Resource
    Performance evaluation of scheduling control of queueing networks: Fluid model heuristics (1995)
    Springer
    Queueing systems 21 (1995), S. 391-413 
    Details
    ISSN: 1572-9443
    Keywords: Dynamic scheduling control ; queueing network ; fluid network ; queueing theory ; flow control ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Motivated by dynamic scheduling control for queueing networks, Chen and Yao [8] developed a systematic method to generate dynamic scheduling control policies for a fluid network, a simple and highly aggregated model that approximates the queueing network. This study addresses the question of how good these fluid policies are as heuristic scheduling policies for queueing networks. Using simulation on some examples these heuristic policies are compared with traditional simple scheduling rules. The results show that the heuristic policies perform at least comparably to classical priority rules, regardless of the assumptions made about the traffic intensities and the arrival and service time distributions. However, they are certainly not always the best and, even when they are, the improvement is seldom dramatic. The comparative advantage of these policies may lie in their application to nonstationary situations such as might occur with unreliable machines or nonstationary demand patterns.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01149168
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  • 14
    Electronic Resource
    Electronic Resource
    Scheduling arrivals to a stochastic service mechanism (1992)
    Springer
    Queueing systems 12 (1992), S. 257-272 
    Details
    ISSN: 1572-9443
    Keywords: Scheduling ; simulation ; perturbation analysis ; stochastic approximation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract We consider the problem of scheduling the arrivals of a fixed number of customers to a stochastic service mechanism to minimize an expected cost associated with operating the system. We consider the special case of exponentially distributed service times and the problems in general associated with obtaining exact analytic solutions. For general service time distributions we obtain approximate numerical solutions using a stochastic version of gradient search employing Infinitesimal Perturbation Analysis estimates of the objective function gradient obtained via simulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01158802
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  • 15
    Electronic Resource
    Electronic Resource
    Queueing models for police-fire merger analysis (1990)
    Springer
    Queueing systems 7 (1990), S. 101-124 
    Details
    ISSN: 1572-9443
    Keywords: Police ; fire ; queueing ; travel time ; simulation ; city government
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Cities with under 100,000 in population expend a significant portion of their budgets on emergency services. One option that a number of these cities have considered for improving service and cutting costs is training personnel to handle both police and fire roles. In this paper we describe a hierarchy of models that we have used to assess the performance viability of a merger as well as to design specific deployment plans. The modeling environment is more complex than a traditional police or fire system. We need to model the response pattern of four or more patrol units along with the simultaneous dispatch of fire equipment from one or more fire stations. The major contribution of the paper is the manner in which a series of models is linked together to forecast a wide range of performance measures under differing dispatch assumptions. We use a queueing model of police patrol to calculate steady state probabilities and expected delays without preemption. We then model two types of preemptive dispatch strategies utilized in responding initially to a major fire by superimposing a binomial distribution on the basic queueing model. There is also a travel time simulation model to calculate conditional expected response time statistics. The queueing models and the travel time simulation are then combined to estimate unconditional expected values. Lastly, we describe a simulation model used to address transient performance issues that are of concern during a major fire.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01158787
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  • 16
    Electronic Resource
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    Maximal coupling and rare perturbation sensitivity analysis (1992)
    Springer
    Queueing systems 11 (1992), S. 307-333 
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    ISSN: 1572-9443
    Keywords: Sensitivity analysis ; perturbation analysis ; discrete event dynamical systems ; simulation ; likelihood ratio ; point processes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract In this article, we introduce a new method for obtaining the ersatz sample derivatives useful in sensitivity analysis: the maximal coupling RPA method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01163859
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  • 17
    Electronic Resource
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    Parallel simulation by multi-instruction, longest-path algorithms (1997)
    Springer
    Queueing systems 27 (1997), S. 37-54 
    Details
    ISSN: 1572-9443
    Keywords: massive parallel processing ; simulation ; MIMD and SIMD parallel computers ; scalable algorithm ; G/G/1 queue ; longest path ; queueing networks
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract This paper presents several basic algorithms for the parallel simulation of G/G/1 queueing systems and certain networks of such systems. The coverage includes systems subject to manufacturing or communication blocking, or to loss of customer due to capacity constraints. The key idea is that the customer departure times are represented by longest-path distance in directed graphs instead of by the usual recursive equations. This representation leads to scalable algorithms with a high degree of parallelism that can be implemented on either MIMD or SIMD parallel computers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019149712019
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  • 18
    Electronic Resource
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    Infinitesimal perturbation analysis for queueing networks with general service time distributions (1999)
    Springer
    Queueing systems 31 (1999), S. 43-58 
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    ISSN: 1572-9443
    Keywords: perturbation analysis ; sample path analysis ; queueing theory ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract We study infinitesimal perturbation analysis (IPA) for queueing networks with general service time distributions. By “general” we mean that the distributions may have discrete components. We show that in the presence of service time distributions with discrete components commuting condition (CC) is no longer sufficient for unbiasedness of IPA. To overcome this difficulty, we introduce the notion of separability of real‐valued random variables, and show that separability of service times together with (CC) establishes unbiasedness of IPA for queueing systems with general service time distributions. It turns out that the piecewise analyticity of service times is a sufficient condition for separability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019193711052
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  • 19
    Electronic Resource
    Electronic Resource
    Tandem behavior of a telecommunication system with finite buffers and repeated calls (1990)
    Springer
    Queueing systems 6 (1990), S. 89-108 
    Details
    ISSN: 1572-9443
    Keywords: Queueing network ; approximation ; retrials ; telecommunication ; simulation ; overflow process ; departure process ; superposition process
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract The tandem behavior of a telecommunication system with finite buffers and repeated calls is modeled by the performance of a finite capacityG/M/1 queueing system with general interarrival time distribution, exponentially distributed service time, the first-come-first-served queueing discipline and retrials. In this system a fraction of the units which on arrival at a node of the system find it busy, may retry to be processed, by merging with the incoming arrival units in that node, after a fixed delay time. The performance of this system in steady state is modeled by a queueing network and is approximated by a recursive algorithm based on the isolation method. The approximation outcomes are compared against those from a simulation study. Our numerical results indicate that in steady state the non-renewal superposition arrival process, the non-renewal overflow process, and the non-renewal departure process of the above system can be approximated with compatible renewal processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02411467
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  • 20
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    Consistency of infinitesimal perturbation analysis estimators with rates (1991)
    Springer
    Queueing systems 8 (1991), S. 265-277 
    Details
    ISSN: 1572-9443
    Keywords: GI/G/1 queue ; birth-death queue ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract We study a class of infinitesimal perturbation analysis (IPA) algorithms for queueing systems with load-dependent service and/or arrival rates. Such IPA algorithms were originally motivated by applications to large queueing systems in conjunction with aggregation algorithms. We prove strong consistency of these estimators through a type of birth and death queue.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02412255
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  • 21
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    Smoothed perturbation analysis for queues with finite buffers (1993)
    Springer
    Queueing systems 14 (1993), S. 57-78 
    Details
    ISSN: 1572-9443
    Keywords: Perturbation analysis ; sample path analysis ; finite buffer queues ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Applying the technique of smoothed perturbation analysis (SPA) to theGI/G/1/K queue, we derive gradient estimators for two performance measures: the mean steady-state system time of a served customer and the probability that an arriving customer is rejected. Unbiasedness of the estimators follows from results of a previous general framework on SPA estimators. However, in that framework, the estimators often require the simulation of numerous additional sample subpaths, possibly making the technique practically infeasible in applications. We exploit some of the special structure of theGI/G/1/K queue to come up with an estimator which requires at most the simulation of a single additional sample subpath. By establishing certain regenerative properties, we provide a strong consistency proof for the estimator.
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    URL: http://dx.doi.org/10.1007/BF01153526
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  • 22
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    Sensitivity analysis of regenerative queuing models (1995)
    Springer
    Queueing systems 19 (1995), S. 247-268 
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    ISSN: 1572-9443
    Keywords: Sensitivity coefficient ; score function ; driving sequence ; queuing model ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Queuing models described as regenerative processes driven by several sequences are under investigation. Occurrence times in these sequences are supposed to be asynchronous, in general. Sensitivity coefficients that are derivatives of some stationary performance measures with respect to definite parameters as well as derivatives of higher orders are derived for such queuing models. These sensitivity coefficients can be evaluated by simulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01150412
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  • 23
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    Analysis of a three node queueing network (1988)
    Springer
    Queueing systems 3 (1988), S. 53-72 
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    ISSN: 1572-9443
    Keywords: Queueing ; queueing network ; sojourn time ; Jackson network ; simulation ; bounds ; approximations ; randomization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract The three node Jackson queueing network is the simplest acyclic network in which in equilibrium the sojourn times of a customer at each of the nodes are dependent. We show that assuming the individual sojourn times are independent provides a good approximation to the total sojourn time. This is done by simulating the network and showing that the sojourn times generally pass a Kolmogorov-Smirnov test as having come from the approximating distribution. Since the sum of dependent random variables may have the same distribution as the sum of independent random variables with the same marginal distributions, it is conceivable that our approximation is exact. However, we numerically compute upper and lower bounds for the distribution of the total sojourn time; these bounds are so close that the approximating distribution lies outside of the bounds. Thus, the bounds are accurate enough to distinguish between the two distributions even though the Kolmogorov-Smirnov test generally cannot.
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    URL: http://dx.doi.org/10.1007/BF01159087
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  • 24
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    Buffer management based on return on consumption in a multi-query environment (1993)
    Springer
    The VLDB journal 2 (1993), S. 1-37 
    Details
    ISSN: 0949-877X
    Keywords: Buffer management ; query optimization ; simulated annealing ; join methods ; queueing model ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract In a multi-query environment, the marginal utilities of allocating additional buffer to the various queries can be vastly different. The conventional approach examines each query in isolation to determine the optimal access plan and the corresponding locality set. This can lead to performance that is far from optimal. As each query can have different access plans with dissimilar locality sets and sensitivities to memory requirement, we employ the concepts of memory consumption and return on consumption (ROC) as the basis for memory allocations. Memory consumption of a query is its space-time product, while ROC is a measure of the effectiveness of response-time reduction through additional memory consumption. A global optimization strategy using simulated annealing is developed, which minimizes the average response over all queries under the constraint that the total memory consumption rate has to be less than the buffer size. It selects the optimal join method and memory allocation for all query types simultaneously. By analyzing the way the optimal strategy makes memory allocations, a heuristic threshold strategy is then proposed. The threshold strategy is based on the concept of ROC. As the memory consumption rate by all queries is limited by the buffer size, the strategy tries to allocate the memory so as to make sure that a certain level of ROC is achieved. A simulation model is developed to demonstrate that the heuristic strategy yields performance that is very close to the optimal strategy and is far superior to the conventional allocation strategy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01231797
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  • 25
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    Disk cache architectures for transaction-like applications in parallel computers (1994)
    Springer
    Computing 53 (1994), S. 13-31 
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    ISSN: 1436-5057
    Keywords: Disk cache ; disk I/O ; I/O architecture ; parallel computers ; parallel I/O ; performance evaluation ; simulation ; transaction processing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Während sich die Rechenleistung heutiger Computersysteme beständig erhöht, entwickelt sich die Platten-Ein/Ausgabe zu einem Engpaß. Dies wird besonders in hochparallelen Maschinen deutlich, wo das Mißverhältnis zwischen Rechen- und Ein/Ausgabeleistung häufig besonders groß ist. Diese Situation kann—in Analogie zur Multiprozessortechnologie—durch Einführung paralleler Ein/Ausgabe-Systeme entschärft werden. Ausgehend von einer solchen verteilten Ein/Ausgabe-Architektur für Parallelrechner, schlagen wir die Benutzung von Plattencaches auf verschiedenen Architekturebenen vor. Diese Cachestrukturen haben wir durch Simulationen näher untersucht. Wir beschreiben zunächst den Ansatz zur Cachemodellierung und das Lastmodell der Ein/Ausgabe, das von Transaktionsverarbeitung und General-Purpose-Lasten abgeleitet ist. Dann diskutieren wir die Ergebnisse für den Fall von Caches, die sich auf jeweils einer einzigen Architekturebene befinden, und für solche auf mehreren Architekturebenen gleichzeitig. Es ergibt sich, daß große Caches auf den Ein/Ausgabeprozessoren in Verbindung mit kleineren auf den Verarbeitungselementen die optimale Struktur darstellen. Zusätzlich können Hardwarecaches auf Plattenebene zur weiteren Leistungssteigerung eingesetzt werden. Bezüglich der Schreiboperationen vom Cache auf die Platte ergibt sich ein verzögerter Schreibmodus (delayed write) als beste Strategie.
    Notes: Abstract I/O in computer systems is prone to become a bottleneck. This is a particular severe problem in highly parallel machines where some applications are fully I/O bound if only one or few conventional I/O paths exist. Similar to the use of multiprocessor technology for increasing processing performance, disk I/O performance can be substantially improved by employing parallel I/O schemes. Based on a distributed I/O architecture for parallel computers, we propose to use disk caches on several architectural levels, and confirm this by simulations of various structural options. In this paper, we describe the cache modelling approach and the I/O load model which has been derived from transaction-processing and general-purpose applications. Then we discuss the results for caches on single and multiple architecture levels. Large caches on I/O processors in combination with small caches on processing elements turn out to be the preferable structure. In addition, hardware caches can be employed at disk level for further performance improvement. For write operations, a delayed write strategy is shown to be superior to other modes.
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    URL: http://dx.doi.org/10.1007/BF02262106
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    A simulation tool for the performance evaluation of parallel branch and bound algorithms (1988)
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    Mathematical programming 42 (1988), S. 245-271 
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    ISSN: 1436-4646
    Keywords: 90C27 ; 68Q10 ; 68R05 ; Parallel computer ; MIMD ; branch and bound ; nondeterminism ; asynchronicity ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract Parallel computation offers a challenging opportunity to speed up the time consuming enumerative procedures that are necessary to solve hard combinatorial problems. Theoretical analysis of such a parallel branch and bound algorithm is very hard and empirical analysis is not straightforward because the performance of a parallel algorithm cannot be evaluated simply by executing the algorithm on a few parallel systems. Among the difficulties encountered are the noise produced by other users on the system, the limited variation in parallelism (the number of processors in the system is strictly bounded) and the waste of resources involved: most of the time, the outcomes of all computations are already known and the only issue of interest is when these outcomes are produced. We will describe a way to simulate the execution of parallel branch and bound algorithms on arbitrary parallel systems in such a way that the memory and cpu requirements are very reasonable. The use of simulation has only minor consequences for the formulation of the algorithm.
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    URL: http://dx.doi.org/10.1007/BF01589406
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    A mathematician's journey through operational research (1988)
    Springer
    Mathematical programming 42 (1988), S. 33-40 
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    ISSN: 1436-4646
    Keywords: Decision theory ; mathematical modelling ; operational research ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
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    URL: http://dx.doi.org/10.1007/BF01589390
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    Computer methods for sampling from gamma, beta, poisson and bionomial distributions (1974)
    Springer
    Computing 12 (1974), S. 223-246 
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    ISSN: 1436-5057
    Keywords: Random numbers ; pseudorandom ; normal distribution ; gamma distribution ; bei distribution ; Poisson distribution ; binomial distribution ; simulation ; numerical analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Zur Erzeugung nicht-gleichverteilter Zufallszahlen braucht man Methoden, die gleichverteilte Zufallszahlen in Größen der gegebenen Verteilung transformieren. Es werden Transformationen untersucht, die Gamma-, Beta-, Poisson- oder Binomial-verteilte Zufallszahlen produzieren. Approximative Verfahren werden nicht behandelt. Die bisher bekannten Algorithmen sind langsam, wenn die Parameter der Verteilungen groß sind. Daher werden neue Methoden eingeführt, die diesen Nachteil weitgehend vermeiden. In allen Verfahren dürfen die Parameter beliebig und jedesmal neu gewählt werden. Für manche Transformationen werden normalverteilte Zufallszahlen als Zwischenschritt benötigt; die hierfür verwendete Methode ist ebenfalls angegeben.
    Notes: Abstract Accurate computer methods are evaluated which transform uniformly distributed random numbers into quantities that follow gamma, beta, Poisson, binomial and negative-binomial distributions. All algorithms are designed for variable parameters. The known convenient methods are slow when the parameters are large. Therefore new procedures are introduced which can cope efficiently with parameters of all sizes. Some algorithms require sampling from the normal distribution as an intermediate step. In the reported computer experiments the normal deviates were obtained from a recent method which is also described.
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    URL: http://dx.doi.org/10.1007/BF02293108
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    Initializing algorithms: A note to the article “Computer methods for sampling from gamma, beta, poisson and binomial distributions” (1979)
    Springer
    Computing 22 (1979), S. 185-189 
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    ISSN: 1436-5057
    Keywords: Random numbers ; pseudorandom ; binomial distributions ; simulation ; algorithm interfaces ; programming methodology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Es wird ein allgemeines Initialisierungsprinzip vorgeschlagen, das die Effizienz von Algorithmen bezüglich der Rechenzeit erhöht. Seine Anwendung auf den Algorithmus NS aus [1] und die daraus resultierenden Verbesserungen werden vorgeführt. Außerdem wird auf einen Programmierfehler in der Originalversion von NS hingewiesen.
    Notes: Abstract A general initialization principle is presented that increases the efficiency of algorithms in terms of computation time. It is applied to the algorithm NS in [1] and results in significant performance improvements. In addition a programming bug is shown in the original version of NS.
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    URL: http://dx.doi.org/10.1007/BF02253129
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    A note on gamma variate generators with shape parameter less than unity (1983)
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    Computing 30 (1983), S. 185-188 
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    ISSN: 1436-5057
    Keywords: 62E30 ; 62E25 ; Random numbers ; simulation ; gamma distribution ; pseudo-random
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Es wird eine Modifikation des Algorithmus von Ahrens und Dieter [1] angegeben, welcher gammaverteilte Zufallsvariable mit einem Formparameter kleiner Eins erzeugt. Der modifizierte Algorithmus ist deutlich schneller, obwohl er kaum komplexer ist als der ursprüngliche.
    Notes: Abstract A modification is given for an algorithm of Ahrens and Dieter [1] which generates random Gamma variates with shape parameter less than unity. The modified algorithm is substantially faster, although hardly more complex than the original one.
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    URL: http://dx.doi.org/10.1007/BF02280789
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    CAD off-line programming for industrial machine vision (1991)
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    Journal of intelligent and robotic systems 4 (1991), S. 129-143 
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    ISSN: 1573-0409
    Keywords: CAD/CAM ; off-line programming ; industrial vision ; pattern recognition ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract CAD/CAM tools are essential components of the computer-integrated factory. Up to now, they have been used for tasks such as the simulation and path programming of numerically controlled machine tools, and sometimes industrial robots. The CAD-vision interconnection described here enables us to program parts learning on the workstation, to download piece features in the vision system for inspection on the production line, to simulate the recognition process on a set of parts stored in the computer, and to update vision files after modifications in the CAD system database.
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    URL: http://dx.doi.org/10.1007/BF00440416
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    Reducing Parallel Program Simulation Complexity by Static Analysis (2000)
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    The journal of supercomputing 17 (2000), S. 299-310 
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    ISSN: 1573-0484
    Keywords: parallel program analysis ; simulation ; performance analysis ; software reengineering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract In this paper we present a novel approach, based on the integration of static program analysis and simulation techniques, for the performance prediction of message passing programs. PS, a simulator of PVM applications developed in the last years by our research group, is fed with traces collected by executing the parallel program to be analyzed in quasi-concurrent mode on a single workstation. Since this process is typically a non negligible part of the simulation complexity, we have devised a technique based on static analysis and code restructuring for significantly speeding up the trace generation. We show how, by statically analyzing and restructuring the program, it is possible to obtain a simplified code (shrinked code) to be run for collecting a reduced version of the traces.
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    URL: http://dx.doi.org/10.1023/A:1026571525145
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    Graphical simulation for sensor based robot programming (1992)
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    Journal of intelligent and robotic systems 5 (1992), S. 49-62 
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    ISSN: 1573-0409
    Keywords: Off-line programming ; robot programming ; simulation ; computer graphics ; sensor programming ; sensor modeling ; robotics ; world modeling ; calibration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The programming of robots is slowly evolving from traditional teach pendant methods to graphical Off-Line Programming (OLP) methods. Graphical simulation tools, such as OLP, are very useful for developing and testing robot programs before they are run on real industrial equipment. OLP systems are also used to develop task level programs. Traditional OLP systems, however, suffer from the limitations of using only position control which does not account for inherent robot inaccuracies and dynamic environments. This paper describes our work on improving and supplementing traditional position control programming methods. A baseline OLP system was implemented at NIST's Automated Manufacturing Research Facility (AMRF). Experience gained in implementing this system showed that an effective OLP system must accurately simulate the real world and must support sensor programming to compensate for real-world changes that cannot be simulated. The developed OLP geometric world model is calibrated using robot mounted ultrasound ranging sensors. This measurement capability produces a baseline geometric model of relatively good static accuracy for off-line programming. The graphical environment must also provide representations of sensor features. For this specific application, force is simulated in order to include force based commands in our robot programs. These sensor based programs are able to run reliably and safely in an unpredictable industrial environment. The last portion of this paper extends OLP and describes the functionality of a complete system for programming complex robot tasks.
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    URL: http://dx.doi.org/10.1007/BF00357130
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    Hierarchical model-based diagnosis for high autonomy systems (1994)
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    Journal of intelligent and robotic systems 9 (1994), S. 193-207 
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    ISSN: 1573-0409
    Keywords: Model-based diagnosis ; robotics ; simulation ; DEVS ; high autonomy systems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Deep reasoning diagnostic procedures are model-based, inferring single or multiple faults from the knowledge of faulty behavior of component models and their causal structure. The overall goal of this paper is to develop a hierarchical diagnostic system that exploit knowledge of structure and behavior. To do this, we use a hierarchical architecture including local and global diagnosers. Such a diagnostic system for high autonomy systems has been implemented and tested on several examples in the domain of robot-managed fluid-handling laboratory.
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    URL: http://dx.doi.org/10.1007/BF01276498
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    Simulating parallel neighboring communications among square meshes and square toruses (1991)
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    The journal of supercomputing 5 (1991), S. 57-71 
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    ISSN: 1573-0484
    Keywords: Mesh ; torus ; neighboring communication ; simulation ; routing ; embedding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Given a d-dimensional square mesh or square torus G and a c-dimensional square mesh or square torus H such that G and H are of the same size but may differ in dimensions and shapes, we study the problem of simulating in H parallel neighboring communications in G. We assume that the nodes in H have only unit-size buffers associated with the links, and that packets can be sent and received simultaneously from all outbound links and inbound links of the nodes. For permutation-type parallel neighboring communications, for all the combinations of graph types and graph shapes of G and H, except for the case in which d 〈 c and c is not divisible by d, we show that H can simulate G either optimally or optimally up to a constant multiplicative factor for fixed values of d and c. For scatter-type parallel neighboring communications, for some special cases of G and H, we also show that H can optimally simulate G. All these simulation times are smaller than the diameter of H, the lower bound on the routing complexity to support general data permutations in H.
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    URL: http://dx.doi.org/10.1007/BF00155858
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    Trace-Based Abstract Interpretation of Operational Semantics (1998)
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    Higher-order and symbolic computation 10 (1998), S. 237-271 
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    ISSN: 1573-0557
    Keywords: abstract interpretation ; operational semantics ; collecting semantics ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract We present trace-based abstract interpretation, a unification of severallines of research on applying Cousot-Cousot-style abstract interpretation a.i. tooperational semantics definitions (such as flowchart, big-step, and small-step semantics)that express a program‘s semantics as a concrete computation tree of trace paths. Aprogram‘s trace-based a.i. is also a computation tree whose nodes contain abstractions ofstate and whose paths simulate the paths in the program‘s concrete computation tree.Using such computation trees, we provide a simple explanation of the central concept of collecting semantics, and we distinguish concrete from abstract collectingsemantics and state-based from path-based collecting semantics. We also expose therelationship between collecting semantics extraction and results garnered from flow-analytic and model-checking-based analysis techniques. We adapt concepts fromconcurrency theory to formalize “safe” and “live” a.i.‘s for computation trees; in particular, coinduction techniques help extend fundamental results to infinite computation trees. Problems specific to the various operational semantics methodologies are discussed: Big-step semantics cannot express divergence, so we employ a mixture of induction andcoinduction in response; small-step semantics generate sequences of programconfigurations unbounded in size, so we abstractly interpret source language syntax.Applications of trace-based a.i. to data-flow analysis, model checking, closure analysis,and concurrency theory are demonstrated.
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    URL: http://dx.doi.org/10.1023/A:1007734417713
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    Adventures in Improving the Scaling and Accuracy of a Parallel Molecular Dynamics Program (1997)
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    The journal of supercomputing 11 (1997), S. 255-278 
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    ISSN: 1573-0484
    Keywords: Ewald ; parallel ; T3E ; simulation ; electrostatic ; molecular dynamics ; PME
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract We report our work to parallelize the Particle Mesh Ewald (PME) method to compute the long-range electrostatic interactions in the molecular dynamics program AMBER and to extend the scalability of the PME method to hundreds of processors.
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    URL: http://dx.doi.org/10.1023/A:1007907925007
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    Intelligent control system simulation of an agricultural robot (1993)
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    Journal of intelligent and robotic systems 8 (1993), S. 267-284 
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    ISSN: 1573-0409
    Keywords: Intelligent control ; simulation ; agriculture ; robotics ; melon harvesting ; intelligent systems ; planning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract An intelligent control system for an agricultural robot which performs in an uncertain and unstructured environment was modelled as distributed, autonomous computing modules that communicate through globally accessible blackboard structures. The control architecture was implemented for a robotic harvester of melons. A CAD workstation was used to plan, model, simulate and evaluate the robot and gripper motions using 3-D, real-time animation. The intelligent control structure was verified by simulating the dynamic data flow scenarios of melon harvesting. Control algorithms were evaluated on measured melon locations. Picking time was reduced by 49% by applying the traveling salesman algorithm to define the picking sequence. Picking speeds can be increased by a continuous mode of operation. However, this decreases harvest efficiency. Therefore, an algorithm was developed to attain 100% harvest efficiency by varying the vehicle's forward speed. By comparing different motion control algorithms through animated visual simulation, the best was selected and thereby the performance improved.
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    URL: http://dx.doi.org/10.1007/BF01257998
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    CCD camera modeling and simulation (1996)
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    Journal of intelligent and robotic systems 17 (1996), S. 309-325 
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    ISSN: 1573-0409
    Keywords: modeling ; camera ; CCD ; subpixel ; simulation ; vision ; image ; diffusion ; CAD ; CIM ; bias
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract In this paper we propose a modeling of an acquisition line made up of a CCD camera, a lens and a frame grabber card. The purpose of this modeling is to simulate the acquisition process in order to obtain images of virtual objects. The response time has to be short enough to permit interactive simulation. All the stages are modelised: in the first phase, we present a geometric model which supplies a point to point transformation that provides, for a space point in the camera field, the corresponding point on the plane of the CCD sensor. The second phase consists of modeling the discrete space which implies passing from the continous known object view to a discrete image, in accordance with the different orgin of the contrast loss. In the third phase, the video signal is reconstituted in order to be sampled by the frame grabber card. The practical results are close to reality when compared to image processing. This tool makes it possible to obtain a short computation time simulation of a vision sensor. This enables interactivity either with the user or with software for the design/simulation of an industrial workshop equipped with a vision system. It makes testing possible and validates the choice of sensor placement and image processing and analysis. Thanks to this simulation tool, we can control perfectly the position of the object image placed under the camera and in this way, we can characterise the performance of subpixel accuracy determining methods for object positioning.
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    URL: http://dx.doi.org/10.1007/BF00339666
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    Coordination and Control of Multi-fingered Robot Hands with Rolling and Sliding Contacts (1999)
    Springer
    Journal of intelligent and robotic systems 24 (1999), S. 125-149 
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    ISSN: 1573-0409
    Keywords: planning ; control ; multi-fingered robot hand ; optimization ; internal force ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract In this paper, the problem of controlling multi-fingered robot hands with rolling and sliding contacts is addressed. Several issues are explored. These issues involve the kinematic analysis and modeling, the dynamic analysis and control, and the coordination of a multi-fingered robot hand system. Based on a hand-object system in which the contacts are allowed to both roll and slide, a kinematic model is derived and analyzed. Also, the dynamic model of the hand-object system with relative motion contacts is studied. A control law is proposed to guarantee the asymptotic tracking of the object trajectory together with the desired rolling and/or sliding motions along the surface of the object. A planning approach is then introduced to minimize the contact forces so that the desired motion of the object and the relative motions between the fingers and the object can be achieved. Simulation results which support the theoretical development are presented.
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    URL: http://dx.doi.org/10.1023/A:1008097528538
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    On the Tradeoff Between Computational Simplicity and Asymptotic Properties in Multivariate Probit (1999)
    Springer
    Computational economics 13 (1999), S. 93-101 
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    ISSN: 1572-9974
    Keywords: efficiency ; multivariate probit ; quasi maximum likelihood ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Economics
    Notes: Abstract This paper discusses the most efficient estimator among Quasi Maximum Likelihood Estimators using at most two levels of numerical integration, for the multivariate probit model. Simulations show that this estimator is more efficient but not more costly than the second-best alternative. However, its added efficiency depends on the correlation structure.
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    URL: http://dx.doi.org/10.1023/A:1008649923740
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    Visualisation in the Simulation and Control of Economic Models (1997)
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    Computational economics 10 (1997), S. 107-118 
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    ISSN: 1572-9974
    Keywords: visualisation ; simulation ; linear quadratic control ; observer ; Kalmanfilter
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Economics
    Notes: Abstract Simulation of economic models is frequently used in the investigation of economic policy. Yet one of the problems with simulation is that it can be difficult to appreciate the model properties due to the nature of the simulation process. Stochastic simulation, for example, can produce large quantities of output which can be difficult to comprehend. Further, when mathematically sophisticated techniques such as the use of optimal control and Kalman Filtering are applied to models, the simulation process can become even more complex. Visualisation techniques in model building, simulation, and analysis of simulation output can help reduce the complexity. This is especially the case with interactive simulation. In this paper we investigate the use of visualisation in simulation by examining the application of optimal control techniques to a stochastic forward looking analytic economic model. We also use interactive object oriented simulation software where objects, such as components of models or graphs of outputs, can be visually manipulated to form simulation systems. We find that the use of visualisation can make the investigation of policy analysis issues with such models more comprehensible.
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    URL: http://dx.doi.org/10.1023/A:1008631912069
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    An application of program unification to priority queue vectorization (1992)
    Springer
    International journal of parallel programming 21 (1992), S. 193-224 
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    ISSN: 1573-7640
    Keywords: Program unification ; priority queue ; parallel ; vector ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract In this experimental study, we apply the technique of program unification to priority queues. We examine the performance of a variety of unified priority queue implementations on a Cray Y-MP. The scope of the study is restricted to determining if different implementations of priority queues exhibit markedly different performance characteristics under program unification. We found this to be true. In a larger view, this result has interesting consequences in the application of program unification to discrete event simulations on vector or SIMD machines. We find the heap to be a promising data structure in the program unification paradigm.
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    URL: http://dx.doi.org/10.1007/BF01408555
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    Stability of traffic patterns in broadband networks (1995)
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    Journal of network and systems management 3 (1995), S. 371-380 
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    ISSN: 1573-7705
    Keywords: Telephone traffic ; network management ; control theory ; dynamic flows ; stability ; routing algorithms ; broadband networks ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract The control of telephony traffic is the task of network management and routing algorithms. In this paper, a study of two trunk groups carrying telephony traffic is used to show that instabilities can arise if there is a delay in getting feedback information for a network controller. The network controller seeks to balance the traffic in the two trunk groups, which may represent two paths from a source to a destination. An analysis shows how factors such as holding time, controller gain and feedback delay influence stability. Simulation of a two service case is also carried out to show that the same instabilities can arise.
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    URL: http://dx.doi.org/10.1007/BF02139530
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    File evaluation in auxiliary storage (1975)
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    International journal of parallel programming 4 (1975), S. 197-204 
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    ISSN: 1573-7640
    Keywords: Information retrieval ; hierarchial storage ; throughput time ; storage management ; linear objective function ; exogenous variables ; simulation ; evaluation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract This paper investigates, in detail, the evaluation of files in auxiliary storage. We are seeking an evaluation procedure whereby those files most critical to throughput time minimization are exposed. Such a procedure can then be used by a storage management routine to move data so that throughput time is improved. The linear objective function defined here considers parameters not only for the file under evaluation but also for the jobs that reference the file and the overall system needs. Exogenous variables in the evaluation function make it an attractive tool for managers. This particular evaluation function is incorporated in the Dynamic File Management model and significant time savings have been realized under simulation.
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    URL: http://dx.doi.org/10.1007/BF01007758
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    Information Systems that Really Support Decision-Making (2000)
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    Journal of intelligent information systems 14 (2000), S. 85-94 
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    ISSN: 1573-7675
    Keywords: decision-support ; information systems ; simulation ; prediction ; interfaces
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Decision makers are expected to make decisions which have a positive effect on the future of their enterprises. We expect that intelligent information systems support their activities. Today, databases and web-based resources, accessed through effective communications, make information about the past rapidly available. To project the future the decision makers either have to use intuition or employ tool for prediction, and initialize such tools with information obtained from an information system to such tools. An effective information system should integrate forecasting the future, and because there choices have been made, such a system must also support the comparative assessment of the effects of alternate decisions. The complexity of an information system handling the past, and multiple futures will be great, and must be modularized with effective interfaces. We recommend the use of an SQL-like interface language to access existing tools to assess the future, as spreadsheets and simulations. Making results of simulations accessible as another contribution to integrated information systems has the potential of greatly augmenting their effectiveness and really support decision-making.
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    URL: http://dx.doi.org/10.1023/A:1008775517030
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    Flying Together: Modelling Air Mission Teams (1998)
    Springer
    Applied intelligence 8 (1998), S. 195-218 
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    ISSN: 1573-7497
    Keywords: modelling ; simulation ; teams ; coordination ; organizations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract The problem of modelling air missions is part of a larger problem—simulating possible war-like scenarios in the air, sea, and on land. In modelling such military systems one is required to model the behaviour of various actors and the resources that are available to them. One aspect of this problem is the modelling of a group of actors as a team and then modelling the coordinated behaviour of such a team to achieve a joint goal. In the domain of air mission modelling the actors are pilots who control aircraft and their behaviour is referred to as tactics. In this paper we present the approach we adopted in modelling teams and team tactics as part of the development of the Smart Whole AiR Mission Model (SWARMM) for the Air Operations Division of the Australian Defence Science and Technology Organization. In our approach teams are composed of sub-teams and adopt organizational structures. Such structures define the responsibilities of the sub-teams towards the mission to be achieved as well as towards the control and coordination of the sub-teams. We also describe how communication is used when adopting a variety of control and coordination strategies and how one could reason about the choice of organizational structures for a given mission and situation.
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    URL: http://dx.doi.org/10.1023/A:1008271016283
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    A computational framework for simulation of Underwater Robotic Vehicle systems (1996)
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    Autonomous robots 3 (1996), S. 253-268 
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    ISSN: 1573-7527
    Keywords: underwater robotics ; hydrodynamics ; simulation ; articulated mechanisms ; tree topologies ; object-oriented design
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract This paper presents a computational framework for efficiently simulating the dynamics and hydrodynamics of Underwater Robotic Vehicle (URV) systems. Through the use of object-oriented mechanisms, a very general yet efficient version of the Articulated-Body (AB) algorithm has been implemented. An efficient solution to branching within chains is developed in the paper so that the algorithm can be used to compute the dynamics for the entire class of open-chain, tree-structured mechanisms. By including compliant contacts with the environment, most closed-chain systems can also be modeled. URV systems with an extended set of topologies can be simulated including proposed underwater walking machines with intra-body powered articulations. Using the encapsulation inherent in C++, the hydrodynamics code has been confined to a single class, thereby explicitly defining this framework and providing an environment for readily implementing desired hydrodynamics algorithms. Resulting simulations are very efficient and can be used in a number of applications both in the development and use of URV systems.
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    URL: http://dx.doi.org/10.1007/BF00141158
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    Repeatability of Real World Training Experiments: A Case Study (1999)
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    Autonomous robots 6 (1999), S. 281-292 
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    ISSN: 1573-7527
    Keywords: mobile robotics ; reinforcement learning ; artificial neural networks ; simulation ; real world
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract We present a case study of reinforcement learning on a real robot that learns how to back up a trailer and discuss the lessons learned about the importance of proper experimental procedure and design. We identify areas of particular concern to the experimental robotics community at large. In particular, we address concerns pertinent to robotics simulation research, implementing learning algorithms on real robotic hardware, and the difficulties involved with transferring research between the two.
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    URL: http://dx.doi.org/10.1023/A:1008984312527
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    Pseudosimulation: An algorithm for distributed simulation with limited memory (1986)
    Springer
    International journal of parallel programming 15 (1986), S. 413-456 
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    ISSN: 1573-7640
    Keywords: Distributed systems ; simulation ; concurrent processes ; message communicating processes ; deadlock detection and recovery
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract In this paper we present a new algorithm for the distributed simulation of systems that may be modeled as a network of processes which exchange event messages (e.g., computer networks, telephone systems). We focus upon the case of fully distributed processes with limited memory available to simulate each process. The synchronization algorithm employed is a blocking algorithm. The simulation of different processes is allowed to proceed in parallel until deadlock occurs, at which time a deadlock-breaking algorithm is invoked as in the Chandy/Misra scheme.(1) A central controller is emploled to detect and aid in the efficient resolution of deadlocks. We solve some problems which were not clearly addressed in the Chandy/Misra scheme. Our deadlock-breaking algorithm, christened Pseudosimulation, is a “look-ahead” algorithm, which undertakes to fill empty buffers with future event messages. Correctness and termination of the algorithm are proven. An analysis of the memory requirements and running time is performed. A lower bound on the memory requirements is also established which simplifies the deadlock-breaking algorithm.
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    URL: http://dx.doi.org/10.1007/BF01414465
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    A simple model of human foveal ganglion cell responses to hyperacuity stimuli (1996)
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    Journal of computational neuroscience 3 (1996), S. 73-82 
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    ISSN: 1573-6873
    Keywords: primate retina ; simulation ; ganglion cells ; spatial vision ; hyperacuity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Medicine , Physics
    Notes: Abstract We developed a physiologically plausible model of the first steps of spatial visual information processing in the fovea of the human retina. With the predictions of this model we could support the hypothesis that, for moderate contrasts (≤ 40%), hyperacuity is mediated by the magnocellular (MC-) pathway. Despite the lower sampling density in the MC pathway, as compared to the parvocellular (PC-) pathway, the information that is transferred by the MC ganglion cells is sufficient to achieve thresholds comparable to those of human subjects in psychophysical tasks. This is a result of the much higher signal-to-noise ratio of the MC pathway cell signals. The PC pathway cells do not transfer enough information for hyperacuity thresholds.
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    URL: http://dx.doi.org/10.1007/BF00158338
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    Distributed processing on the basis of parallel and antagonistic pathways simulation of the femur-tibia control system in the stick insect (1996)
    Springer
    Journal of computational neuroscience 3 (1996), S. 179-198 
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    ISSN: 1573-6873
    Keywords: reflex pathway ; neuronal network ; simulation ; parliamentary principle ; neural basis of behavior
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Medicine , Physics
    Notes: Abstract In inactive stick insects, sensory information from the femoral chordotonal organ (fCO) about position and movement of the femur-tibia joint is transferred via local nonspiking interneurons onto extensor and flexor tibiae motoneurons. Information is processed by the interaction of antagonistic parallel pathways at two levels: (1) at the input side of the nonspiking interneurons and (2) at the input side of the motoneurons. We tested by a combination of physiological experiments and computer simulation whether the known network topology and the properties of its elements are sufficient to explain the generation of the motor output in response to passive joint movements, that is resistance reflexes. In reinvestigating the quantitative characteristics of interneuronal pathways we identified 10 distinct types of nonspiking interneurons. Synaptic inputs from fCO afferents onto these interneurons are direct excitatory and indirect inhibitory. These connections were investigated with respect to position and velocity signals from the fCO. The results were introduced in the network simulation. The motor output of the simulation has the same characteristics as the real system, even when particular types of interneurons were removed in the simulation and the real system.
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    URL: http://dx.doi.org/10.1007/BF00161131
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    Modeling Hermissenda: I. Differential contributions of I A and I C to type-B cell plasticity (1996)
    Springer
    Journal of computational neuroscience 3 (1996), S. 137-153 
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    ISSN: 1573-6873
    Keywords: potassium ; compartmental ; learning ; plasticity ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Medicine , Physics
    Notes: Abstract We developed a multicompartmental Hodgkin-Huxley model of the Hermissenda type-B photoreceptor and used it to address the relative contributions of reductions of two K+ currents, I a and I C, to changes in cellular excitability and synaptic strength that occur in these cells after associative learning. We found that reductions of gC, the peak conductance of I C, substantially increased the firing frequency of the type-B cell during the plateau phase of a simulated light response, whereas reductions of gA had only a modest contribution to the plateau frequency. This can be understood at least in part by the contributions of these currents to the light-induced (nonspiking) generator potential, the plateau of which was enhanced by gC reductions, but not by gA reductions. In contrast, however, reductions of gA broadened the type-B cell action potential, increased Ca2+ influx, and increased the size of the postsynaptic potential produced in a type-A cell, whereas similar reductions of gC had only negligible contributions to these measures. These results suggest that reductions of I A and I C play important but different roles in type-B cell plasticity.
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    Simulating posterior Gibbs distributions: a comparison of the Swendsen-Wang and Gibbs sampler methods (1994)
    Springer
    Statistics and computing 4 (1994), S. 189-201 
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    ISSN: 1573-1375
    Keywords: Markov random fields ; posterior Gibbs distributions ; simulation ; Swendsen-Wang algorithm ; Gibbs sampler ; restoration ; monitoring convergence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract We show in detail how the Swendsen-Wang algorithm, for simulating Potts models, may be used to simulate certain types of posterior Gibbs distribution, as a special case of Edwards and Sokal (1988), and we empirically compare the behaviour of the algorithm with that of the Gibbs sampler. Some marginal posterior mode and simulated annealing image restorations are also examined. Our results demonstrate the importance of the starting configuration. If this is inappropriate, the Swendsen-Wang method can suffer from critical slowing in moderately noise-free situations where the Gibbs sampler convergence is very fast, whereas the reverse is true when noise level is high.
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    URL: http://dx.doi.org/10.1007/BF00142571
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    Bayesian analysis of contingency tables: a simulation and graphics-based approach (1996)
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    Statistics and computing 6 (1996), S. 277-287 
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    ISSN: 1573-1375
    Keywords: Bayesian inference ; contingency tables ; Gibbs sampling ; graphical methods ; hypothesis testing ; independence ; intraclass tables ; model comparison ; predictive densities ; quasisymmetry ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract In this paper we present a simulation and graphics-based model checking and model comparison methodology for the Bayesian analysis of contingency tables. We illustrate the approach by testing the hypotheses of independence and symmetry on complete and incomplete simulated tables.
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    URL: http://dx.doi.org/10.1007/BF00140872
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    Design and Programming Tools for Time Critical Applications (1998)
    Springer
    Real-time systems 14 (1998), S. 251-267 
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    ISSN: 1573-1383
    Keywords: development environment ; real-time ; scheduling ; simulation ; design tool
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract The development of time critical applications needs specific tools able to cope with both functional and non-functional requirements. In this paper we describe a design and programming environment to assist the development of hard real-time applications. An interactive graphic interface is provided to facilitate the design of the application according to three hierarchical levels. The development model we propose is based on an iterative process in which the real-time scheduling support is considered from the beginning of the design phases. Our graphic environment integrates several tools to analyze, test, and simulate the real-time application under development. In particular, the tools we have implemented are: a Design Tool, to describe the structure of the application, a Schedulability Analyser Tool (SAT), to verify off-line the feasibility of the schedule of a critical task set, a Scheduling Simulator, to test the average behavior of the application, and a Maximum Execution Time (MET) estimator to bound the worst case duration of each task.
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    Teaching Respiratory Physiology: Clinical Correlation with a Human Patient Simulator (2000)
    Springer
    Journal of clinical monitoring and computing 16 (2000), S. 465-470 
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    ISSN: 1573-2614
    Keywords: respiratory physiology ; simulation ; education
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Medicine
    Notes: Abstract In recent years students have increasingly objected to laboratory exercises involving animal subjects. We have replaced the valuable animal experiments with demonstrations using a full-scale human patient simulator. In small groups first-year medical students observe realistic clinical situations such as opioid-induced hypoventilation, pneumothorax, and pulmonary edema. Students obtain information through physical examination, arterial blood gas analysis and chest radiography. They practice interventions such as providing supplemental oxygen and mask ventilation, monitor the results, and develop a basic differential diagnosis and treatment plan. We utilize the clinical context to review fundamental concepts of respiratory physiology including the alveolar air equation and oxyhemoglobin dissociation curve. The students give these laboratory exercises uniformly superior evaluations.
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    Problem-Based Learning in Residency Education: A Novel Implementation Using a Simulator (1999)
    Springer
    Journal of clinical monitoring and computing 15 (1999), S. 227-232 
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    ISSN: 1573-2614
    Keywords: simulation ; problem-based learning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Medicine
    Notes: Abstract Background. We developed a problem-based learning exercise with a full-scale human patient simulator to teach residents the emergency management and differential diagnosis of acute intraoperative hypotension. Methods.We developed the exercise through the following steps: clear definition of learning objectives, preparation of an appropriate case stem, development of clinically realistic scenarios to illustrate objectives, and an interactive instructor to stimulate discussion. Results. The exercise focused on the differential diagnosis of intraoperative hypotension, and the acute treatment of hypovolemia, cardiac tamponade, tension pneumothorax, and anaphylaxis. Conclusions. Exercises on a full-scale patient simulator are a natural extension of problem-based learning. Recent research in learning theory provides the rationale for this teaching modality's potential as a learning tool.
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    URL: http://dx.doi.org/10.1023/A:1009980500385
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    Autoregulation in a Simulator-Based Educational Model of Intracranial Physiology (1999)
    Springer
    Journal of clinical monitoring and computing 15 (1999), S. 481-491 
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    ISSN: 1573-2614
    Keywords: Cerebral blood flow ; cerebral vascular resistance ; cerebral perfusion pressure ; PaCO2 ; PaO2 ; cerebral metabolic rate of oxygen consumption ; educational model ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Medicine
    Notes: Abstract Objective.To implement a realistic autoregulation mechanism toenhance an existing educational brain model that displays in real-time thecerebral metabolic rate (CMRO2), cerebral blood flow (CBF),cerebral blood volume (CBV), intracranial pressure (ICP), and cerebralperfusion pressure (CPP). Methods.A dynamic cerebrovascular resistance(CVR) feedback loop adjusts automatically to maintain CBF within a range ofthe CPP and defines autoregulation. The model obtains physiologic parametersfrom a full-scale patient simulator. We assumed that oxygen demand andarterial partial pressure of carbon dioxide (CO2 responsivity) arethe two major factors involved in determining CBF. In addition, our brainmodel increases oxygen extraction up to 70% once CBF becomes insufficient tosupport CMRO2. The model was validated against data from theliterature. Results.The model's response varied less than 9%from the literature data. Similarly, based on correlation coefficients betweenthe brain model and experimental data, a good fit was obtained for curvesdescribing the relationship between CBF and PaCO2 at a meanarterial blood pressure of 150 mm Hg (R2 = 0.92) and 100 mm Hg(R2 = 0.70). Discussion.The autoregulated brain model, withincorporated CO2 responsivity and a variable oxygen extraction,automatically produces changes in CVR, CBF, CBV, and ICP consistent withliterature reports, when run concurrently with a METI full-scale patientsimulator (Medical Education Technologies, Inc., Sarasota, Florida). Once themodel is enhanced to include herniation, vasospasm, and drug effects, itsutility will be expanded beyond demonstrating only basic neuroanesthesiaconcepts.
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    Accuracy of Deadspace Free Ventilatory Measurements for Lung Function Testing in Ventilated Newborns: A Simulation Study (2000)
    Springer
    Journal of clinical monitoring and computing 16 (2000), S. 563-573 
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    ISSN: 1573-2614
    Keywords: Infant ; respiratory function testing ; lung mechanic ; simulation ; pneumotachography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Medicine
    Notes: Abstract Objective. A dead space free method based on simultaneous ventilatory measurements in the inspiratory and expiratory limb of the ventilator circuit was compared to the conventional endotracheal method where the flow is measured between ETT and Y-Piece. The aim of our study was to find out how the arrangement of this setup affects the measuring accuracy of 1) the ventilatory and 2) the lung mechanical parameters by means of a computer simulation. Method. The system consisting of ventilator tubes and lung was described in state space and the flow signals of endotracheal method, of dead space free method and the pressure at the Y-piece were simulated in the time domain. To investigate the influence of the position of the pneumotachographs (PNTs) in the ventilator circuit on measuring accuracy, the distance d0 of the PNT from the Y-piece was varied between 0 and 900mm. The respiratory compliance C, resistance R and inertance I were calculated by least square method using the simulated flow and pressure signals of both methods. Results. Compared to the endotracheal method, with increasing d0 the tidal volume measured with the deadspace free method rose linearly, depending on the ratio between the compliance of the ventilator tubes to the respiratory compliance. The differences of C and R for both methods were acceptable (〈 10%) if the distance between each PNT and the y-piece didn’t exceed 200mm and the shorter d0 the higher the measuring accuracy. The inertance could not be measured by this method with satisfactory accuracy if d0 was higher than 100 mm. Inconclusion, the dead space free method can be used for accurate ventilatory measurements during mechanical ventilation. However, for lung mechanic measurements in very low birth weight infants the position of the PNTs must be as short as possible.
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    An interactive computer simulator of the circulation for knowledge acquisition in cardio-anesthesia (1991)
    Springer
    Journal of clinical monitoring and computing 8 (1991), S. 151-158 
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    ISSN: 1573-2614
    Keywords: cardio-anesthesia ; cardio-vascular system ; decision support ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Medicine
    Notes: Abstract Knowledge-based decision support systems for use in cardio-anesthesia can provide online support to the anesthesiologist by generating intelligent alarms [13]. However, the acquisition and validation of a consistent knowledge base for this application bears problems related to the transfer of clinical experiences into a rule system. An interactive simulator of the human circulation is presented that supports the process of knowledge acquisition and testing. The simulator can be controlled in realtime by an anesthesiologist during the simulation run thus providing a basis for interdisciplinary discussion of routine as well as critical situations. The output data can be transfered to a knowledge-based system for test purposes. The simulator is currently being used for the development of the Anesthesia Expert Assist System AES-2 [14]. With regard to the special application a model of the heart-function was integrated which enables the simulation of heart insufficiency. Simulation runs under various conditions are presented and discussed. The simulator was implemented on an ATARI ST personal computer.
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    CINA: a software to Compose INfusion sheets for IV Anesthetic drugs (1991)
    Springer
    Journal of clinical monitoring and computing 8 (1991), S. 225-229 
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    ISSN: 1573-2614
    Keywords: anesthetics ; intravenous ; pharmacokinetics ; computers ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Medicine
    Notes: Summary CINA is a software which uses LOTUS 1-2-3 commands and macros and it runs on an IBM PC. It contains an extensive database of three sections. Section 1 includes a list of several models of commercialized infusion devices. Section 2 presents the available IV packagings for a list of IV drugs. Section 3 contains the record of IV standard infusion regimens for each drug. Any other new infusion device, drug, or standard infusion regimen can be added or modified. The software verifies the compatibility of the prescribed infusion device according to the available drug packaging contained in the database. Moreover, it converts the infusion steps into the flow-rate units of the selected infusion device according to the patient's weight and the chosen drug concentration. Finally, the software allows the storage of all the information on a disk file or outputting on a printer.
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    A bolus plus continuous infusion protocol for controlling neuromuscular blockade during anesthesia (1995)
    Springer
    Journal of clinical monitoring and computing 12 (1995), S. 89-95 
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    ISSN: 1573-2614
    Keywords: anesthesia ; atracurium ; closed-loop control ; drug delivery ; feedback control ; infusion protocol ; mivacurium ; neuromuscular blockade ; simulation ; vecuronium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Medicine
    Notes: Abstract Neuromuscular blockade is controlled during anesthesia by administering either bolus doses or a continuous infusion of a blocking agent. To test whether a constant infusion technique requires less attention and provides better control we used a computer to simulate neuromuscular blockade. Using the model we maintained 95% blockade with mivacurium, atracurium, and vecuronium. It required 1.2 changes per hour to maintain the blockade by continuous infusion; an average of 4.5 bolus per hour were required to maintain blockade by the bolus technique. When the bolus and continuous infusion techniques were combined, only 0.16 changes per hour were required. Atracurium was then given to ten patients during anesthesia, following the bolus plus continuous infusion protocol. After a bolus was given to obtain 100% twitch depression, for tracheal intubation, neuromuscular function was assessed by train-of-four stimulation of the ulnar or facial nerves by observing the resultant muscle movement. When the first twitch of the train-of-four returned, relaxation was maintained by continuous infusion. A bolus was given and the drug infusion rate was changed whenever the level of relaxation changed from the desired one twitch of the train-of-four. The infusion rate was adjusted only 1.12±0.79 times per hour. The desired level of muscle relaxation was easily controlled using the bolus plus continuous infusion protocol. The infusion scheme might be implemented in future drug infusion pumps.
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    Mathematical modelling of ventilation mechanics (1995)
    Springer
    Journal of clinical monitoring and computing 12 (1995), S. 105-112 
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    ISSN: 1573-2614
    Keywords: modelling ; parameter estimation ; simulation ; ventilation mechanics ; data acquisition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Medicine
    Notes: Abstract Routine application of ‘rule of thumb’ parameter sets in clinical practice pushes model visions to the background, including the complete framework of assumptions, simplifications, suppositions and conditions. But: models can be a very strong tool, when applied selectively — that means, with a clear idea of destination, definition, parameter selection and verification. This article discusses universal issues of modelling — based on ventilation mechanics models in intensive care medicine.
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    Simulation of mechanical respiration using a multicompartment model for ventilation mechanics and gas exchange (1995)
    Springer
    Journal of clinical monitoring and computing 12 (1995), S. 231-239 
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    ISSN: 1573-2614
    Keywords: gas exchange ; mechanical respiration ; model ; simulation ; ventilation mechanics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Medicine
    Notes: Abstract The mechanical respiration of intubated patients is a process which is influenced by many parameters and, through its many interactions, is extremely complex. Taken by itself the logical analysis of this complexity is extraordinarily difficult and leads very often to false conclusions. For that reason computer simulation of complex systems by means of the computer is an important tool in the analysis of these processes. Required is a model which describes the actual behavior of the system. However, it should not be overlooked that a model always describes only a portion of reality. Models having exclusively to do with ventilation mechanics or with gas exchange cannot simulate the interactions between the two. To accomplish this purpose, an improved model is necessary, including both partial processes and thereby capturing the complexity of the system. Accordingly, both ventilation mechanics and gas exchange have been integrated equally into the newly developed model for the simulation program Simu Vent. The core of the program builds a functional multicompartment model of the lungs and considers the partial processes ventilation mechanics, gas transport, gas mixing and gas exchange. Further considered are the respirator, blood circulation and peripheral compartments. The program runs under a graphical user interface, allowing its easy use. Responsible for this ease is the user's ability to interact with the program while simulation is in progress and the specially designed graphic screen mask. Comparing measured with simulated values demonstrated that the measured curve can be simulated with minimal error. Furthermore, the multicompartment model describes disruptions in distribution. Simu Vent's application is especially well advised in the description and analysis of the theoretical fundamentals of mechanical respiration. This aspect is meaningful above all in education and research, rendering these two the model's main areas of use.
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    Twitcher: A Device to Simulate Thumb Twitch Response to Ulnar Nerve Stimulation (1998)
    Springer
    Journal of clinical monitoring and computing 14 (1998), S. 135-140 
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    ISSN: 1573-2614
    Keywords: simulation ; peripheral nerve stimulation ; neuromuscular blockade ; thumb adduction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Medicine
    Notes: Abstract Objective. To design and fabricate a device to simulate evoked thumb adduction in response to ulnar nerve stimulation. Methods. We implemented a computer-controlled, motorized thumb (TWITCHER) that responds to ulnar nerve stimulation by an unmodified peripheral nerve stimulator. Clinically realistic response patterns are generated for both depolarizing and non-depolarizing muscle relaxants and three modes of stimulation (single twitch, train-of-four, tetanus). Results. The device has been used in a full-scale patient simulator for the last six years. Discussion. TWITCHER has been well received by participants in simulation exercises including the use of neuromuscular blocking drugs.
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    A Simple Strategy for Faster Induction and More Cost-Effective Use of Anesthetic Vapor (1999)
    Springer
    Journal of clinical monitoring and computing 15 (1999), S. 17-21 
    Details
    ISSN: 1573-2614
    Keywords: Low flow anesthesia ; inhaled anesthetics ; anesthetic cost ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Medicine
    Notes: Abstract Introduction. Inducing general anesthesia often involves mask ventilation using high fresh gas flow (FGF) to administer anesthetic vapor prior to endotracheal intubation. A common practice is to turn the vaporizer off when the mask is removed from the patient's face to avoid room contamination (VAPOff). An alternative approach is to leave the vaporizer on and turn the FGF to minimum to reduce the amount of vapor laden gas that can enter the room (FGFOff). The objective of this study is to compare the relative induction times and vapor costs associated with each induction strategy. Methods. Each induction method was simulated using Gasman® (MedMan Simulations, Chestnut Hill, MA) for Windows assuming a 70 kg patient. To simulate a period of mask ventilation with anesthetic vapor prior to intubation, the FGF was set to 6 l/min and the isoflurane vapor concentration to 1.2% (1 MAC) for three minutes with an alveolar ventilation of 5 l/min and cardiac output of 5 l/min. For the first simulation of the intubation period (FGFOff), FGF was turned to 150 ml/min, minute ventilation was set to zero and the vaporizer setting unchanged for one minute. Initial settings were then restored and the rate of change of anesthetic vapor concentration in the circuit (Vckt) and alveolus (Valv) followed for 10 minutes along with the cost of delivered vapor (V$). For the second simulation (VAPOff), after the initial three minutes of vapor delivery, the vaporizer was set to zero, minute ventilation was set to zero and the FGF left unchanged for one minute. The initial settings were then restored and Vckt, Valv and V$ followed for ten minutes. The cost calculation was based upon a 100 ml bottle of Isoflurane at $72/bottle. Actual gas flow was measured at the y-piece of a circle system for fresh gas flows from 0.15 to 6 l/min. Results. At the end of the simulated intubation period (minute 4), Vckt was unchanged with the FGFOff method whereas it had fallen by more than half with the VAPOff method. Using VAPOff, it took until the 6-minute mark for Vckt to return to the same concentration that existed prior to intubation at minute three. Throughout the 10 minute simulated induction, Valv using FGFOff exceeded Valv using VAPOff although the difference became small at the end of the period. V$ was essentially identical at all time points. No flow into the room was measured at the minimum fresh gas flow whereas higher fresh gas flows resulted in a significant portion of the fresh gas flowing into the room. Conclusions. The strategy of turning the FGF to minimum and leaving the vaporizer on during intubation does not contaminate the room and speeds induction by fostering a greater alveolar concentration than the VAPOff method. Cost savings are derived using FGFOff since a higher alveolar concentration is achieved at the same vapor cost. Additional cost savings are demonstrated since a low flow technique is possible immediately after intubation when using FGFOff. The practice of turning off the vaporizer during endotracheal intubation while FGF remains high should be abandoned.
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    URL: http://dx.doi.org/10.1023/A:1009900605045
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    An application of ESL to a stochastic dynamic market model with free entry and exit (1992)
    Springer
    Computational economics 5 (1992), S. 105-118 
    Details
    ISSN: 1572-9974
    Keywords: Economic models ; simulation ; simulation language
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Economics
    Notes: Abstract The application of a new simulation language (ESL) is demonstrated through a stochastic dynamic market model with free entry and exit. Since ESL allows us to specify single economic units and to coordinate all their activities, the details of a microeconomic process can be described. The market model consists of different types of producers and consumers, whose actions can be simulated under changing structural conditions.
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    URL: http://dx.doi.org/10.1007/BF00436484
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    Random texture models for material structures (2000)
    Springer
    Statistics and computing 10 (2000), S. 121-132 
    Details
    ISSN: 1573-1375
    Keywords: random sets ; random structures ; Boolean model ; Boolean random functions ; dead leaves model ; simulation ; image analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract We consider the construction and properties of some basic random structure models (point processes, random sets and random function models) for the description and for the simulation of heterogeneous materials. They can be specialized to three dimensional Euclidean space. Their implementation requires the use of image analysis tools.
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    URL: http://dx.doi.org/10.1023/A:1008942325749
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    Estimating means when sampling gives probabilities as well as values or “Looking a gift horse in the mouth” (2000)
    Springer
    Statistics and computing 10 (2000), S. 245-252 
    Details
    ISSN: 1573-1375
    Keywords: estimation of means ; sample mean ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract Consider the random sampling of a discrete population. The observations, as they are collected one by one, are enhanced in that the probability mass associated with each observation is also observed. The goal is to estimate the population mean. Without this extra information about probability mass, the best general purpose estimator is the arithmetic average of the observations, XBAR. The issue is whether or not the extra information can be used to improve on XBAR. This paper examines the issues and offers four new estimators, each with its own strengths and liabilities. Some comparative performances of the four with XBAR are made. The motivating application is a Monte Carlo simulation that proceeds in two stages. The first stage independently samples n characteristics to obtain a “configuration” of some kind, together with a configuration probability p obtained, if desired, as a product of n individual probabilities. A relatively expensive calculation then determines an output X as a function of the configuration. A random sample of X could simply be averaged to estimate the mean output, but there are possibly more efficient estimators on account of the known configuration probabilities.
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    URL: http://dx.doi.org/10.1023/A:1008995628693
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    The stalactite plot for the detection of multivariate outliers (1993)
    Springer
    Statistics and computing 3 (1993), S. 27-35 
    Details
    ISSN: 1573-1375
    Keywords: elemental set ; Mahalanobis distance ; masking ; Monte Carlo testing ; normalized distance ; outliers ; simulation ; stalactite plot
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract Detection of multiple outliers in multivariate data using Mahalanobis distances requires robust estimates of the means and covariance of the data. We obtain this by sequential construction of an outlier free subset of the data, starting from a small random subset. The stalactite plot provides a cogent summary of suspected outliers as the subset size increases. The dependence on subset size can be virtually removed by a simulation-based normalization. Combined with probability plots and resampling procedures, the stalactite plot, particularly in its normalized form, leads to identification of multivariate outliers, even in the presence of appreciable masking.
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    URL: http://dx.doi.org/10.1007/BF00146951
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    An adaptive Student Centered Curriculum for an intelligent training system (1995)
    Springer
    User modeling and user adapted interaction 5 (1995), S. 67-86 
    Details
    ISSN: 1573-1391
    Keywords: Adaptive ; planning ; planning recognition ; simulation ; multi-agent ; multimedia ; tutoring ; artificial intelligence ; knowledge representation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract An intelligent tutoring system customizes its presentation of knowledge to the individual needs of each student based on a model of the student. Student models are more complex than other user models because the student is likely to have misconceptions. We have addressed several difficult issues in reasoning about a student's knowledge and skills within a real-time simulation-based training system. Our conceptual framework enables important aspects of the tutor's reasoning to be based upon simple, comprehensible representations that are the basis for a Student Centered Curriculum. We have built a system for teaching cardiac resuscitation techniques in which the decisions abouthow to teach are separated from the decisions aboutwhat to teach. The training context (i.e., choice of topics) is changed based on a tight interaction between student modeling techniques and simulation management. Although complex student models are still required to support detailed reasoning about how to teach, we argue that the decision about what to teach can be adequately supported by qualitatively simpler techniques, such as overlay models. This system was evaluated in formative studies involving medical school faculty and students. Construction of the student model involves monitoring student actions during a simulation and evaluating these actions in comparison with an expert model encoded as a multi-agent plan. The plan recognition techniques used in this system are novel and allow the expert knowledge to be expressed in a form that is natural for domain experts.
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    URL: http://dx.doi.org/10.1007/BF01101802
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    Applications of a general propagation algorithm for probabilistic expert systems (1992)
    Springer
    Statistics and computing 2 (1992), S. 25-36 
    Details
    ISSN: 1573-1375
    Keywords: Reasoning under uncertainty ; causal probabilistic network ; influence diagram ; belief network ; knowledge-based systems ; evidence ; fast retraction ; maxinlization ; explanation ; simulation ; junction tree ; charge ; potential function ; flow ; propagation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract A probabilistic expert system provides a graphical representation of a joint probability distribution which can be used to simplify and localize calculations. Jensenet al. (1990) introduced a ‘flow-propagation’ algorithm for calculating marginal and conditional distributions in such a system. This paper analyses that algorithm in detail, and shows how it can be modified to perform other tasks, including maximization of the joint density and simultaneous ‘fast retraction’ of evidence entered on several variables.
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    URL: http://dx.doi.org/10.1007/BF01890546
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    How to Implement a Safe Real-Time System:The OBSERV Implementation of the Production Cell Case Study (1998)
    Springer
    Real-time systems 15 (1998), S. 61-90 
    Details
    ISSN: 1573-1383
    Keywords: system design ; executable specifications ; class-based modeling ; simulation ; formal methods ; model checking
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract The Production Cell example was chosen by FZI (the Computer Science Research Center), in Karlsruhe. to examine the benefits of formal methods for industrial applications. This example was implemented in more than 30 formalisms. This paper describes the implementation of the Production Cell in OBSERV. The OBSERV methodology for software development is based on rapid construction of an executable specification, or prototype, of a system, which may be examined and modified repeatedly to achieve the desired functionality. The objectives of OBSERV also include facilitating a smooth transition to a target system, and providing means for reusing specification, design, and code of systems, particularly real-time reactive systems. In this paper we show how the methods used in the OBSERV implementation address the requirements imposed by reactive systems. We describe the OBSERV implementation of the Production cell, explain design decisions, with special emphasis on reusability and safety issues. We demonstrate how to take care of safety and liveness properties required for this example. These properties are checked by means of simulation and formally proved with a model checker.
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    URL: http://dx.doi.org/10.1023/A:1008074907254
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    Mixture separation for mixed-mode data (1996)
    Springer
    Statistics and computing 6 (1996), S. 85-92 
    Details
    ISSN: 1573-1375
    Keywords: Cluster analysis ; Conditional Gaussian distribution ; EM algorithm ; graphical modelling ; location model ; mixture maximum likelihood ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract One possible approach to cluster analysis is the mixture maximum likelihood method, in which the data to be clustered are assumed to come from a finite mixture of populations. The method has been well developed, and much used, for the case of multivariate normal populations. Practical applications, however, often involve mixtures of categorical and continuous variables. Everitt (1988) and Everitt and Merette (1990) recently extended the normal model to deal with such data by incorporating the use of thresholds for the categorical variables. The computations involved in this model are so extensive, however, that it is only feasible for data containing very few categorical variables. In the present paper we consider an alternative model, known as the homogeneous Conditional Gaussian model in graphical modelling and as the location model in discriminant analysis. We extend this model to the finite mixture situation, obtain maximum likelihood estimates for the population parameters, and show that computation is feasible for an arbitrary number of variables. Some data sets are clustered by this method, and a small simulation study demonstrates characteristics of its performance.
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    URL: http://dx.doi.org/10.1007/BF00161577
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    Evolving Neuro-Controllers for a Dynamic System Using Structured Genetic Algorithms (1998)
    Springer
    Applied intelligence 8 (1998), S. 113-121 
    Details
    ISSN: 1573-7497
    Keywords: genetic algorithms ; neural networks ; pole-cart system ; neuro-controller ; simulation ; gene activation ; multi-level chromosome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract This paper describes the application of the Structured Genetic Algorithm (sGA) to design neuro-controllers for an unstable physical system. In particular, the approach uses a single unified genetic process to automatically evolve complete neural nets (both architectures and their weights) for controlling a simulated pole-cart system. Experimental results demonstrate the effectiveness of the sGA-evolved neuro-controllers for the task—to keep the pole upright (within a specified vertical angle) and the cart within the limits of the given track.
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    URL: http://dx.doi.org/10.1023/A:1008291923124
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    Multiple Adaptive Agents for Tactical Driving (1998)
    Springer
    Applied intelligence 9 (1998), S. 7-23 
    Details
    ISSN: 1573-7497
    Keywords: intelligent vehicles ; evolutionary algorithms ; simulation ; distributed AI
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Recent research in automated highway systems has ranged from low-level vision-based controllers to high-level route-guidance software. However, there is currently no system for tactical-level reasoning. Such a system should address tasks such as passing cars, making exits on time, and merging into a traffic stream. Many previous approaches have attempted to hand construct large rule-based systems which capture the interactions between multiple input sensors, dynamic and potentially conflicting subgoals, and changing roadway conditions. However, these systems are extremely difficult to design due to the large number of rules, the manual tuning of parameters within the rules, and the complex interactions between the rules. Our approach to this intermediate-level planning is a system which consists of a collection of autonomous agents, each of which specializes in a particular aspect of tactical driving. Each agent examines a subset of the intelligent vehicle's sensors and independently recommends driving decisions based on their local assessment of the tactical situation. This distributed framework allows different reasoning agents to be implemented using different algorithms. When using a collection of agents to solve a single task, it is vital to carefully consider the interactions between the agents. Since each reasoning object contains several internal parameters, manually finding values for these parameters while accounting for the agents' possible interactions is a tedious and error-prone task. In our system, these parameters, and the system's overall dependence on each agent, is automatically tuned using a novel evolutionary optimization strategy, termed Population-Based Incremental Learning (PBIL). Our system, which employs multiple automatically trained agents, can competently drive a vehicle, both in terms of the user-defined evaluation metric, and as measured by their behavior on several driving situations culled from real-life experience. In this article, we describe a method for multiple agent integration which is applied to the automated highway system domain. However, it also generalizes to many complex robotics tasks where multiple interacting modules must simultaneously be configured without individual module feedback.
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    URL: http://dx.doi.org/10.1023/A:1008243013521
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    Dataflow query execution in a parallel main-memory environment (1993)
    Springer
    Distributed and parallel databases 1 (1993), S. 103-128 
    Details
    ISSN: 1573-7578
    Keywords: parallel query processing ; multi-join queries ; simulation ; analytical modeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract In this paper, the performance and characteristics of the execution of various join-trees on a parallel DBMS are studied. The results of this study are a step into the direction of the design of a query optimization strategy that is fit for parallel execution of complex queries. Among others, synchronization issues are identified to limit the performance gain from parallelism. A new hash-join algorithm is introduced that has fewer synchronization constraints than the known hash-join algorithms. Also, the behavior of individual join operations in a join-tree is studied in a simulation experiment. The results show that the introduced Pipelining hash-join algorithm yields a better performance for multi-join queries. The format of the optimal join-tree appears to depend on the size of the operands of the join: A multi-join between small operands performs best with a bushy schedule; larger operands are better off with a linear schedule. The results from the simulation study are confirmed with an analytic model for dataflow query execution.
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    Masthead (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 17 (1996) 
    Details
    ISSN: 0192-8651
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540170201
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    Theoretical and practical aspects of the convergence properties of the dynamically defined reaction path method (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 17 (1996), S. 289-297 
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    ISSN: 0192-8651
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: In spite of much work on path-following methods, a solid mathematical foundation (especially convergence conditions and their practical measures) are lacking in most cases. In our previous articles the general theory of a new global searching procedure, the dynamically defined reaction path (DDRP) method, its rigorous mathematical formulation, the algorithm, a practical computation program, and some applications to abstract mathematical functions and simple chemical examples have been presented. In this article we give a short theoretical description and some practical criteria and measures for the convergence of the method and illustrate the principles and uses by numerical mathematical and chemical examples. © 1996 by John Wiley & Sons, Inc.
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    An ab initio study of heterodienophiles addition to 2,3-diaza-1,3-butadiene: An example of endo-lone-pair effect on the reaction energy barrier (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 17 (1996), S. 298-305 
    Details
    ISSN: 0192-8651
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Transition states for the Diels-Alder reactions of 2,3-diaza-1,3-butadiene with ethylene, formaldehyde, formaldimine, cis- and trans- diazene, and nitrosyl hydride were located by ab initio molecular orbital calculations. The bond orders of the new forming bonds have been used to determine the asynchronicity of the reactions. Ab initio calculations show that the energy barrier for the hetero-Diels-Alder reactions is relatively high. The highest energy barrier of 34.76 kcal/mol calculated at the MP4/6-31G*//MP2/6-31G* level was found for the exo-cis-diazene addition to 2,3-diaza-1,3-butadiene. In all cases, when two diastereomeric transition structures are possible, the one with the endo hydrogen, exo lone pair was predicted to have a lower activation barrier. This behavior can be explained by the n-π and n-n loan pair repulsion interaction between the dienophile and diene heteroatoms in the corresponding transition state. The barrier is higher for those reactions which in the transition state have more lone electron pairs. Also, the barrier is higher when the lone pairs are endo oriented than when they are exo oriented in the transition state. © 1996 by John Wiley & Sons, Inc.
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    The 1:1 glycine zwitterion-water complex: An ab initio electronic structure study (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 17 (1996), S. 338-349 
    Details
    ISSN: 0192-8651
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: More than a dozen stationary points on the potential energy surface for the 1:1 glycine zwitterion - water complex have been investigated at Hartree-Fock or MP2 levels of theory with basis sets ranging from split valence (4-31G) to split valence plus polarization and diffuse function (6-31 + + G**) quality. Only one true minimum (GLYZWM, C1 symmetry) could be located on the potential energy surface. GLYZWM features a bridged water molecule acting as both a hydrogen bond acceptor and donor with the NH3- and CO2- units of the glycine zwitterion. The total hydrogen bond energy in GLYZWM is computed as 16 kcal/mol (MP2/6-31 ++ G** // 6-31 ++ G**, including corrections for basis set superpositions errors). The computed vibrational frequencies and normal mode forms of the GLYZWM complex resemble in many cases experimental assignments made for the glycine zwitterion in bulk water on the basis of Raman spectroscopy. © 1996 by John Wiley & Sons, Inc.
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    Optimization of the Lennard-Jones parameters for a combined ab initio quantum mechanical and molecular mechanical potential using the 3-21G basis set (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 17 (1996), S. 386-395 
    Details
    ISSN: 0192-8651
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A combined ab initio quantum mechanical and molecular mechanical (AI-QM/MM) potential for use in molecular modeling and simulation has been described. In this article, we summarize a procedure for deriving the empirical parameters embedded in a combined QM/MM model and suggest a set of Lennard-Jones parameters for the combined ab initio 3-21G and MM OPLS-TIP3P (AI-3/MM) potential. Interaction energies and geometrical parameters predicted with the AI-3/MM model for over 80 hydrogen-bonded complexes of organic compounds with water were found to be in good accord with ab initio 6-31G(d) results. We anticipate that the AI-3/MM potential should be reasonable for use in condensed phase simulations. © 1996 by John Wiley & Sons, Inc.
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    Potential derived charges using a geodesic point selection scheme (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 17 (1996), S. 1-18 
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    ISSN: 0192-8651
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Potential derived (PD) atomic charges, obtained by fitting to molecular electrostatic potentials, are widely used in molecular modeling and simulation calculations. These charges are known to depend on the sample of points chosen for the fit, on the particular point selection algorithm, on molecular translations and rotations in many instances, and even on molecular conformation. Following a critique of currently available methods, a novel point selection scheme is described which results in a highly isotropic array of points located on a series of fused-sphere van der Waals surfaces. The pattern of points is based on tesselations of the icosahedron, and these are discussed in some detail along with their connection with virus morphology, geodesic domes, and symmetric fullerene structures. Using methanol as a test case, it is shown that the new method leads to PD charges which are independent of translation and display minimal rotational dependence, and are hence far better suited to the determination of PD charges from electrostatic potentials obtained from both theory and experimental X-ray diffraction data. The conformation dependence of the newly derived PD charges for alanyl dipeptide is found to be substantially less than obtained earlier by Williams [Biopolymers 29, 1367 (1990)]. © 1996 by John Wiley & Sons, Inc.
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    Masthead (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 17 (1996) 
    Details
    ISSN: 0192-8651
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
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    URL: http://dx.doi.org/10.1002/jcc.540170401
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    Ab initio and density functional theory study of structures and energies for dimethoxymethane as a model for the anomeric effect (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 17 (1996), S. 757-766 
    Details
    ISSN: 0192-8651
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Ab initio molecular orbital theory and density functional theory calculations have been carried out on dimethoxymethane as a model for the anomeric effect. We optimized various conformations of dimethoxymethane using Gaussian 92 at the MP2/6-311 + + G**, MP2/DZP + Diffuse, MP2/6-31G**, and Becke3LYP/6-31G** levels of theory. These methods were evaluated based on their performance in reproducing structures and energies of dimethoxymethane when compared to experiment. This study also examined the structure and energy of dimethoxymethane as a function of dihedral angles for examining the anomeric effect at the MP2/6-31G** and Becke3LYP/6-31G** levels of theory. These calculations are qualitatively consistent with the anomeric effect observations in carbohydrates and with earlier calculations. Quantitative comparisons with earlier results reveal that dimethoxymethane has lower total energies, smaller rotational barriers, and shorter bond lengths than was previously determined. The Becke3LYP calculations were also compared to the MP2 results. The density functional theory findings show that the minimum energy structures correspond well with experimental and MP2 data. The total and relative energies from molecular orbital theory and density functional theory vary to some extent. Contour plots of the relative energies of dimethoxymethane were evaluated and compared to a relative energy contour plot determined by MM3. The contour plots were similar, showing slightly larger changes in energies for the MP2 results than for the Becke3LYP results, which in turn were slightly larger than the MM3 results. Density functional theory calculations are an excellent alternative method of calculation due to increased speed and reliable accuracy of the density functional calculations. These results will serve as a benchmark for modelling the anomeric effect in carbohydrates. © 1996 John Wiley & Sons, Inc.
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    The structure of 1-chlorosilatrane: An ab initio molecular orbital and a density functional theory study (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 17 (1996), S. 767-780 
    Details
    ISSN: 0192-8651
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The molecular geometries of the 1-chloro-, 1-fluoro-, 1-methyl-, and 1-hydrogenosilatranes were fully optimized by the restricted Hartree-Fock (HF) method supplemented with 3-21G, 3-21G(d), 6-31G(d), and CEP-31G(d) basis sets; by MP2 calculations using 6-31G(d) and CEP-31G(d) basis sets; and by GGA-DFT calculations using 6-31G(d5) basis set with the aim of locating the positions of the local minima on the energy hypersurface. The HF/6-31G(d) calculations predict long (〉254 pm) and the MP2/CEP calculations predicted short (∼225 pm) equilibrium Si(SINGLE BOND)N distances. The present GGA-DFT calculations reproduce the available gas phase experimental Si(SINGLE BOND)N distances correctly. The solid phase experimental results predict that the Si(SINGLE BOND)N distance is shorter in 1-chlorosilatrane than in 1-fluorosilatrane. In this respect the HF results show a strong basis set dependence, the MP2/CEP results contradict the experiment, and the GGA-DFT results in electrolytic medium agree with the experiment. The latter calculations predict that 1-chlorosilatrane is more polarizable than 1-fluorosilatrane and also support a general Si(SINGLE BOND)N distance shortening trend for silatranes during the transition from gas phase to polar liquid or solid phase. The calculations predict that the ethoxy links of the silatrane skeleton are flexible. Consequently, it is difficult to measure experimentally the related bond lengths and bond and torsion angles. This is the probable origin of the surprisingly large differences for the experimental structural parameters. On the basis of experimental analogies, ab initio calculations, and density functional theory (DFT) calculations, a gas phase equilibrium (re) geometry is predicted for 1-chlorosilatrane. The semiempirical methods predict a so-called exo minimum (at above 310 pm Si(SINGLE BOND)N distance); however, the ab initio and GGA-DFT calculations suggest that this form is nonexistent. The GGA-DFT geometry optima were characterized by frequency analysis. © 1996 by John Wiley & Sons, Inc.
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    Density functional Gaussian-type orbital approach in theoretical study of S2F2 isomerization (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 17 (1996), S. 835-840 
    Details
    ISSN: 0192-8651
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The structures of two isomers, difluorodisulfane (FSSF) and thiothionylfluoride(SSF2), and the corresponding transition structure were generated with density functional theory (DFT) methods. Three groups of DFT methods were used: local(Local Spin Density Approximation, LSDA), nonlocal (local with gradient corrections; BLYP and BP86), and hybrid methods that include a mixture of Hartree-Fock (HF) exchange with nonlocal correlation (Becke3BLYP, Becke3P86). An extended basis set [6-311 + + G(3df)] was used for all calculations, although satisfactory results can be obtained with the 6-311G(d) basis set. The geometries obtained were compared with both restricted Hartree-Fock (RHF) calculated and experimentally obtained values. The energy outcome and the activation barrier for the isomerization were evaluated. It was determined that excellent geometries can be obtained with the Becke3B86 hybrid method, whereas for reasonable energies MP2 single-point calculations on these geometries are necessary. © 1996 by John Wiley & Sons, Inc.
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    Molecular symmetry and ab initio calculations. II. Symmetry-matrix and symmetry-supermatrix in the Dirac-Fock method (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 17 (1996), S. 851-863 
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    ISSN: 0192-8651
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The concepts of symmetry-matrix and symmetry-supermatrix introduced in article I[J. Comput. Chem., 10, 957 (1989)] can be generalized to the Dirac-Fock method. By using the semidirect product decomposition of Oh and the linear vector space theory, the irreducible representation basis of Oh for any molecular system (Oh or its subgroups) can be deduced analytically in the nonorthonormal Cartesian Gaussian basis. This method is extended to discuss the double-valued representations of Oh* in the complex Cartesian Gaussian spinor basis. In the double-valued irreducible representation basis of D2*, the matrix of kinetic operator c(OVERLINE)σ(/OVERLINE)·(OVERLINE)p(/OVELINE) in the Dirac-Fock equation can be reduced into a real symmetric and can be grouped into classes under the operations in D3d. Therefore, the symmetry-matrix and symmetry-supermatrix can also be used in the Dirac-Fock method to reduce the storage of two electron integrals and calculations of Fock matrix during iterations by a factor of ca. g2 (g is the order of the molecular symmetry group). In addition, a method to deal with the nonorthonormal space is presented. © 1996 by John Wiley & Sons, Inc.
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    The location of transition states: A comparison of Cartesian, Z-matrix, and natural internal coordinates (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 17 (1996), S. 888-904 
    Details
    ISSN: 0192-8651
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A comparison is made between geometry optimization in Cartesian coordinates, in Z-matrix coordinates, and in natural internal coordinates for the location of transition states. In contrast to the situation with minima, where all three coordinate systems are of comparable efficiency if a reliable estimate of the Hessian matrix is available at the starting geometry, results for 25 different transition states covering a wide range of structural types demonstrate that in practice Z-matrix coordinates are generally superior. For Cartesian coordinates, the commonly used Hessian update schemes are unable to guarantee preservation of the necessary transition state eigenvalue structure, while current algorithms for generating natural internal coordinates may have difficulty handling the distorted geometries associated with transition states. The widely used Eigenvector Following (EF) algorithm is shown to be extremely efficient for optimizing transition states. © 1996 by John Wiley & Sons, Inc.
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    Ab initio study of the formation of C3H3+ from the reaction of CH3+ with acetylene (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 17 (1996), S. 905-909 
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    ISSN: 0192-8651
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Ab initio molecular orbital theory has been used to study the mechanism of the formation of C3H3+ from the reaction of CH3+ with acetylene. The highest level geometry optimizations and frequencies were computed at MP2-FC/6-31G**; single point energies of all the critical structures were computed to the MP4-FC/6-31G**//MP2-FC/6-31G** theory level. One of the three alternative transition structures leading to the formation of C3H3+ gives the cyclopropenyl cation and the other two the propargyl cation. The proportions of C3H2D+ and C3HD2+ obtained when CD3+ reacts with acetylene, and the composite nature of the metastable peak observed for the[C3H5]+→[C3H3]++ H2 fragmentation are explained by assuming a different degree of deuterium scrambling depending on the energy of the system. © 1996 by John Wiley & Sons, Inc.
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    Sum and density of states of polyatomic systems with hindered rotors (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 17 (1996), S. 954-961 
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    ISSN: 0192-8651
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The density or sum of states for a collection of independent oscillators, free rotors, and one-dimensional hindered rotors is obtained with good accuracy by numerical inversion of the corresponding total partition function by the method of steepest descents. The hindered-rotor partition functions are used in both classical and quantum forms, the latter in the approximation proposed by Truhlar [J. Comput. Chem., 12, 266 (1991)]. The numerical inversion compares well with analytical results obtained in a simple artificial case and also with an exact count of states in a large ethane-like system. Inversion of the hindered-rotor classical partition function is shown to lead to a somewhat different energy dependence of the sum or density of states, relative to the quantum counterpart, which is considered to be a more realistic representation. The routines presented are simple and fast enough to be of use in microcanonical rate calculations. © 1996 by John Wiley & Sons, Inc.
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    Theoretical calculations of extraction selectivity: Alkali cation complexes of calix[4]-bis-crown6 in pure water, chloroform, and at a water/chloroform interface (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 17 (1996), S. 1520-1531 
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    ISSN: 0192-8651
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: We report theoretical calculations of ion extraction selectivity by ionophores, based on molecular dynamics simulations coupled with the free energy perturbation technique. This method is applied to the Calix[4]-bis-crown6 (L) ionophore, which displays remarkable selectivity for Cs+ over Na+ extraction from an aqueous to a chloroform phase. Using a thermodynamic cycle, we model the cation extraction selectivity of L from water to chloroform and calculate a peak for Cs+, in agreement with the experiment. This high Cs+ ionophoricity is accounted for mostly by differential solvation effects, with standard 1-6-12 pairwise potentials without need of “special π interactions” with the ionophore. The effect of a picrate (Pic-) counterion on structures and selectivities is investigated. Finally, we report simulations on the L ionophore free and on the LCs+ and LCs+Pic- complexes at the water/chloroform interface. We find that all these species are “adsorbed” at the interface like surfactants instead of diffusing spontaneously to the organic phase. © 1996 by John Wiley & Sons, Inc.
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    Normalization of the Fox - Goodwin algorithm to calculate scattering matrices in an adiabatic basis at low and high collision energies (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 17 (1996), S. 1559-1563 
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    ISSN: 0192-8651
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Scattering matrices in an adiabatic basis were calculated for a model two-state atomic collision using a simple modification (normalization of the wave function) of the Fox - Goodwin three-point recurrence relation. Unlike the previous application of this method to scattering the present algorithm was able to precisely calculate the scattering matrix not only at low collision energies (eV), but also at high energies (keV). An analysis of the convergence of the modified Fox - Goodwin algorithm is also discussed for several angular momenta and for several energies where the results were compared to the renormalized Numerov method. © 1996 by John Wiley & Sons, Inc.
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    Peptide docking using dynamic programming (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 17 (1996), S. 418-428 
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    ISSN: 0192-8651
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: An extended dynamic programming algorithm is presented that is applicable to the fragment assembly phase of the site mapping fragment assembly approach to peptide docking. After constructing a free energy map of the receptor using each of the amino acids in the peptides to be docked, we apply the algorithm to two systems: HIV-1 protease complexed with a synthetic hexameric inhibitor, and MHC HLA-A2 complexed with a nonameric peptide. The all atom root mean square deviation between the predicted and crystal structures was 1.7 and 2.0 Å, respectively. While these results are reasonable considering the relatively coarse level of mapping, the more important result is that the structures are probably very close to the best obtainable by an exhaustive search through the entire data map, and yet are obtained with a reduction of 3-5 orders of magnitude in the number of computations. We also outline a prescription for an iterative procedure which finds the global minimum with increasing confidence. © 1996 by John Wiley & Sons, Inc.
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    Molecular dynamics for proteins: Performance evaluation on massively parallel computers based on mesh networks using a space decomposition approach (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 17 (1996), S. 469-475 
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    ISSN: 0192-8651
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Parallel computing seems to be the solution for molecular dynamics of large atomic systems, such as proteins in water environments, but the simulation time critically depends on the processor allocation strategy. A study of the optimal processor allocation based on a space decomposition algorithm for single instruction multiple data flow mesh computers is presented. A particular effort has been made to identify the best criterion according to which the atoms can be allocated to the processors using a spatial decomposition approach. The computing time depends on the granularity of the space decomposition among processing elements and on the ratio between the computation power of processing elements and the communication speed of the interprocessor network. © 1996 by John Wiley & Sons, Inc.
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    Superacidity of neutral Brönsted acids in gas phase (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 17 (1996), S. 30-41 
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    ISSN: 0192-8651
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Quantum chemical calculations of potentially superacidic neutral Brönsted acids were carried out using the PM3 method. It was shown that the PM3 method can be used to predict the gas phase acidities of acidic compounds only if empirical corrections are made. A strong acidifying effect is predicted for a new family of compounds in which an sp2 oxygen is substituted by an (DOUBLE BOND) NSO2CF3 group. So, for example, such replacement is expected to result in acid strengthening by 47.5 kcal/mol in the case of CH3CHO and by 22.7 kcal/mol in the case of CF3SO2OH. The acidities of such compounds are predicted to be increased further (nonadditively) by stepwise replacements of (DOUBLE BOND) O by (DOUBLE BOND) NSO2CF3. The geometries of known superacidic systems were reproduced quite well by PM3 method. The geometries of several superacidic systems were analyzed. © 1996 by John Wiley & Sons, Inc.
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    Semiempirical treatment of electrostatic potentials and partial charges in combined quantum mechanical and molecular mechanical approaches (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 17 (1996), S. 87-108 
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    ISSN: 0192-8651
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A semiempirical treatment of electrostatic potentials and partial charges is presented. These are the basic components needed for the evaluation of electrostatic interaction energies in combined quantum mechanical and molecular mechanical approaches. The procedure to compute electrostatic potentials uses AM1 and MNDO wave functions and is based on one previously suggested by Ford and Wang. It retains the NDDO approximation and is thus both easy to implement and computationally efficient. Partial atomic charges are derived from a semiempirical charge equilibration model, which is based on the principle of electronegativity equalization. Large sets of ab initio restricted Hartee-Fock (RHF/6-31G*) reference data have been used to calibrate the semiempirical models. Applying the final parameters (C, H, N, O), the ab initio electrostatic potentials are reproduced with an average accuracy of 20% (AM1) and 25% (MNDO), respectively, and the ab initio potential derived charges normally to within 0.1 e. In most cases our parameterized models are more accurate than the much more expensive quasi ab initio techniques, which employ deorthogonalized semiempirical wave functions and have generally been preferred in previous applications. © 1996 John Wiley & Sons, Inc.
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    Theoretical investigations on 1,2-ethanediol: The problem of intramolecular hydrogen bonds (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 17 (1996), S. 133-147 
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    ISSN: 0192-8651
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The conformational space of 1,2-ethanediol is studied on the basis of ab initio and semiempirical calculations. All possible conformers are treated. The relative energies of the conformers are systematically studied using various basis sets up to 6-311 + G(3df, 3pd) in order to perform calculations as accurate as possible within a reasonable amount of computer time. Electron correlation is included using Møller-Plesset perturbation theory. We propose two methods to evaluate the basis set superposition error associated with the intramolecular hydrogen bond appearing in some of the conformers. The results of semiempirical calculations are compared with these ab initio calculations. © 1996 by John Wiley & Sons, Inc.
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    Direct CI method in restricted configuration spaces (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 17 (1996), S. 178-184 
    Details
    ISSN: 0192-8651
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A configuration interaction (CI) method in restricted CI (RCI) space obtained by imposing inequality-type restrictions on the occupancies of groups of molecular orbitals (MOs) was studied. The direct CI approach in such space was analyzed, and some recommendations concerning practical implementation of the RCI method are given. The corresponding program has been written in FORTRAN 77 for an IBM 486 DX personal computer and has been used for electronic structure calculations on transition metal complexes using a valence MO basis with the INDO approximation. © 1996 by John Wiley & Sons, Inc.
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