| A Widely Deployable
Web-based Network Simulation Framework using CORBA IDL-based APIs
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|---|---|---|
| Arjun
Cholkar GTE Data Services Irving, TX 75038, USA. |
Philip
Koopman Department of Electrical and Computer Engineering & Institute for Complex Engineered Systems Carnegie Mellon University Pittsburgh, PA 15213, USA. | |
| ABSTRACT | ||
| Web-based network simulation frameworks are becom-ing highly portable and extensible. However, they still lack the degree of language and platform independence required for large-scale deployment on the World Wide Web. Our approach to enabling large-scale deployment uses a set of standard CORBA-IDL based programming interfaces, a publisher-subscriber model for communica-tion, and dynamic composition of all simulation entities (simulated network hosts and links). A prototype appli-cation for testing distributed computing policies demon-strates that the CORBA components not only provide language and platform-independence, but also provide the ability for simulationists to connect objects to a third party distributed simulation. By using a uniform mes-saging approach to all simulation events, objects can be reassigned to different simulation entities without re-quiring code modifications. Dynamic loading and un-loading of objects during a simulation run supports fault simulation, simulation entity polymorphism, and gen-eration of dynamic topologies. A link-scheduling exam-ple has demonstrated that our language and platform-independent network simulation framework attains extensibility and flexibility. | ||
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| The High Level
Architecture: Is There a Better Way? |
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|---|---|---|
| Wayne J.
Davis University of Illinois at Urbana–Champaign |
Gerald L.
Moeller U.S. Army Material Systems Analysis Activity | |
| ABSTRACT | ||
| This paper discusses the basic design approach adopted for the High level Architecture and the design goals that it addresses in the military simulation arena. Next, the limitations of this architecture are discussed with particular focus on the real-time information requirements needed to support its operation. Finally, the paper discusses HLA's inability to model complex systems with hierarchical command and control structures and the inherent limitations that this deficiency will impose upon the application of futuristic simulation technologies to military applications. | ||
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| ON-LINE DATA PROCESSING
IN SIMULATION MODELS: NEW APPROACHES AND POSSIBILITIES THROUGH HLA
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|---|---|---|
| Thomas
Schulze Steffen Straßburger Department of Computer Science Otto-von-Guericke University Magdeburg Universitätsplatz 2 39106 Magdeburg, Germany |
Ulrich
Klein Fraunhofer Institute for Factory Operation and Automation Sandtorstrasse 22 39106 Magdeburg, Germany | |
| ABSTRACT | ||
| The United States Department of Defense's High Level Architecture for Modeling and Simulation (HLA) provides a standardized interface for distributed simulations. The recent advent of HLA has greatly increased interest in the use of distributed, interoperable simulation model components. This paper focuses on how on-line data (i.e. data from real-time dependent processes) can be used in analytical simulation models and how the use of HLA based components can facilitate the integration of this kind of data into simulations. The paper also discusses the issue of cloning federates and federations and introduces some potential applications of cloning for a public transportation prototype example. | ||
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| OPTIMISTIC PARALLEL
SIMULATION OVER A NETWORK OF WORKSTATIONS
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|---|---|---|
| Reuben
Pasquini Vernon Rego Department of Computer Sciences Purdue University West Lafayette, IN 47907-1398, U.S.A. |
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| ABSTRACT | ||
| The low cost and scalability of a PC and ethernet-based network of workstations makes the NOW an attractive platform for parallel discrete event simulation. This paper discusses the demands a parallel simulation places upon a network that connects distributed workstations, and presents two approaches to managing inter-processor communication in PDES on a NOW. | ||
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| WEB-BASED PERFORMANCE
VISUALIZATION OF DISTRIBUTED DISCRETE EVENT SIMULATION |
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|---|---|---|
| Adel S.
Elmaghraby Sherif A. Elfayoumy Irfan S. Karachiwala James H. Graham Ahmed Z. Emam AlaaEldin M. Sleem Speed School, Computer Engineering and Computer Science Dept. University of Louisville Louisville, Kentucky 40292, U.S.A. |
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| ABSTRACT | ||
| This paper reports on an effort to adapt
an existing distributed simulation visualization system to become Web
accessible. The system was originally developed for performance
visualization and experimentation with parameters affecting PDES systems
using the Time Warp protocols. This paper presents a model for converting
legacy PDES systems to be Web accessible, and discusses the initial
results from the conversion effort on this specific application. After
finishing this work, we will be able to collect a wealth of data through
the Web for future data mining, and to create an intelligent agent for
performance tuning of Time Warp applications.
| ||
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| THE EFFECT OF
STATE-SAVING IN OPTIMISTIC SIMULATION ON A CACHE-COHERENT NON-UNIFORM
MEMORY ACCESS ARCHITECTURE |
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|---|---|---|
| Christopher D.
Carothers Department of Computer Science Rensselaer Polytechnic Institute 110 8th Street Troy, New York U.S.A. 12180-3590 |
Kalyan S.
Perumalla Richard M. Fujimoto College of Computing Georgia Institute of Technology Atlanta, GA 30332-0280 | |
| ABSTRACT | ||
| State-saving and reverse computation are
two different approaches by which rollback is realized in Time Warp-based
parallel simulation systems. Of the two approaches, state-saving is, in
general, more memory-intensive than reverse computation. When executed on
a state-of-the-art commercial CC-NUMA (Cache Coherent Non-Uniform Memory
Architecture) multiprocessor, our Time Warp system runs almost 6 times
slower if state-saving is used than if reverse computation is used. The
focus of this paper is to understand why state-saving yields such poor
performance when compared to reverse computation on a CC-NUMA
multiprocessor. To address this question, we examined the low level machine performance statistics, especially those that relate to memory system performance, such as caching, and translation look-aside buffer (TLB) misses. The outcome of the performance study suggests that TLB misses are the primary culprit for state-saving's performance degradation. | ||
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| DECISION SUPPORT
FOR CALL CENTER MANAGEMENT USING SIMULATION
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|---|---|---|
| Rupesh
Chokshi AT&T Labs 200 Laurel Ave Middletown, NJ 07748, U.S.A. |
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| ABSTRACT | ||
| In an era of rapidly growing information
and communications, call centers are becoming an integral part for a
majority of corporations. Corporations are migrating their customer care
operations to the Internet, investing in electronic care, sales automation
tools, etc. A significant amount of human and computer systems investment
is placed on call center setup. Moreover managing call centers has become
a very complex task, as substantial resources and business impact is at
stake. Consequently, it calls for practicing scientific decision-making
methodologies and tools for strategic management. This paper discusses how
simulation has added value as a decision support tool, during a major
Reengineering Initiative at AT&T. | ||
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Wintersim |
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| CALL CENTER SIMULATION
IN BELL CANADA |
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|---|---|---|
| Oryal
Tanir Bell Canada 2nd floor 1050 Beaver Hall Montreal, QC H2Z 1S4 CANADA |
|
Richard J.
Booth Bell Canada 5th floor North 483 Bay Street Toronto, ON M5G 2E1 CANADA |
| ABSTRACT | ||
| Call centers have relied historically,
on Erlang-C based estimation formulas to help determine number of agent
positions and queue parameters. These estimators have worked fairly well
in traditional call centers, however recent trends such as skill-based
routing, electronic channels and interactive call handling demand more
sophisticated techniques (see Cleveland and Mayben 1997). Discrete event
simulation provides the necessary techniques to gain insight into these
new trends, and helping to shape their current and future designs. This
paper relates the experiences of designing call center simulations in Bell
Canada. We the experience of constructing, executing and analysing a large
call center model. Problems that we faced are identified and potential
solutions are given. The examples are taken from large and small call
centers alike in the attempt to bring forth some common problems that a
simulationist will face. | ||
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Wintersim |
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| SIMULATION OF A CLAIMS
CALL CENTER: A SUCCESS AND A FAILURE |
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|---|---|---|
| Roger
Klungle AAA Michigan Business Operations Analysis 1 Auto Club Drive Dearborn, Michigan 48126. U.S.A. |
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| ABSTRACT | ||
| This paper addresses the call center
management process and the role of simulation in this process. Strengths
and weaknesses of workforce management systems and the Erlang-C model are
reviewed and the role of discrete event simulation is highlighted. An
application in an insurance claims call center is utilized to show the
effectiveness of simulation in evaluating call center designs and also the
difficulties in selling selected results to management. The paper
concludes with some lessons learned about the call center process,
discrete event simulation, workforce management systems, and the specific
claims application. | ||
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Wintersim |
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| COMPUTING THE
DISTRIBUTION FUNCTION OF A CONDITIONAL EXPECTATION VIA MONTE CARLO:
DISCRETE CONDITIONING SPACES |
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|---|---|---|
| Shing-Hoi
Lee Fixed-Income Research Group Morgan Stanley Dean Witter & Co. 1585 Broadway Manhattan, NY 10036, U.S.A. |
Peter W.
Glynn Department of Engineering-Economic Systems and Operations Research Stanford University Stanford, CA 94305-4023, U.S.A. | |
| ABSTRACT | ||
| We examine different ways of numerically computing the distribution function of conditional expectations where the conditioning element takes values in a finite or countably infinite outcome space. Both the conditional expectation and the distribution function itself are computed via Monte Carlo simulation. Given a limited (and fixed) computer budget, the quality of the estimator is gauged by the inverse of its mean square error. It is a function of the fraction of the budget allocated to estimating the conditional expectation versus the amount of sampling done relative to the "conditioning variable". We will present the asymptotically optimal rates of convergence for different estimators and resolve the trade-off between the bias and variance of the estimators. Moreover, central limit theorems are established for some of the estimators proposed. We will also provide algorithms for the practical implementation of the estimators and illustrate how confidence intervals can be formed in some cases. Major potential application areas include calculation of Value at Risk (VaR) in the field of mathematical finance and Bayesian performance analysis. | ||
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Wintersim |
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| THE PHANTOM SPA METHOD:
AN INVENTORY PROBLEM REVISITED |
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|---|---|---|
| Felisa J.
Vázquez-Abad Manuel Cepeda-Jûneman Department of Computer Science and Operations Research University of Montreal Montreal, H3C 3J7, CANADA |
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| ABSTRACT | ||
| It is widely accepted today that the Infinitesimal Perturbation Analysis (IPA) method for estimating sensitivities is the preferred method, when it is applicable. The major problem with IPA is handling certain kinds of discontinuities, such as thresholds. The Smoothed Perturbation Analysis (SPA) method was conceived applying a conditional expectation to a dynamic system, similar to the Filtered Monte Carlo Simulation. Conditioning smoothes out the discontinuities and then IPA can be applied to the conditional estimator. Since this alternative estimator has been partly integrated through the conditioning, some knowledge about the underlying distribution is required. When this is not available, SPA estimators require additional estimation. Traditionally, this has been implemented via off-line simulations that produce independent replications of a difference process. We propose here to bypass this operation by using parallel phantom systems: replicas of the original system that are conditional to the critical events of interest yet use common random numbers instead of independent replications. We show how the efficiency can dramatically improve from the gain in correlation (variance reduction) as well as the gain in computational effort (random variables are generated once and used for all parallel phantoms). | ||
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Wintersim |
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| ESTIMATING AMBULANCE
REQUIREMENTS IN AUCKLAND NEW ZEALAND |
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|---|---|---|
| Shane G.
Henderson Andrew Mason Department of Engineering Science University of Auckland Private Bag 92019 Auckland, New Zealand |
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| ABSTRACT | ||
| The St. John Ambulance Service (Auckland
Region) in New Zealand (St Johns) supplies ambulance services to Crown
Health Enterprises. Current and future contracts specify several minimum
performance targets that St Johns must achieve. As the city of Auckland
grows, roads become congested, and population demographics change. These
changes mean that St. Johns faces a very difficult problem: how many
ambulances are needed, and where should they be placed in order to meet
the service targets efficiently. A preliminary study using queueing theory established that more ambulances were needed and suggested placements. However, the assumptions required in the queueing model were such that a more realistic modelling approach was deemed necessary to verify and refine the queueing model results. We discuss a simulation and analysis software tool BartSim developed by the authors, that is currently being used to address the issues St. Johns faces. The results obtained from BartSim are used to drive changes to the rostering process for staff at St. Johns. | ||
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Wintersim |
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| SIMULATING THE ECONOMIC
VIABILITY OF CRAWFISH PRODUCTION: A TWO-STAGE APPROACH
|
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|---|---|---|
| Amy C.
Hasegawa University of Delaware Department of Food and Resource Economics Townsend Hall Newark, DE 19717, U.S.A. |
|
Conrado M.
Gempesaw University of Delaware Office of the Vice Provost for Academic Programs and Planning 234 Hullihen Hall Newark, DE 19716, U.S.A. |
| William H.
Daniels Bernard R. Petrosky Delaware State University Department of Agriculture and Natural Resources 1200 North Dupont Highway Dover, DE 19901, U.S.A. |
||
| ABSTRACT | ||
| The purpose of this study is to
determine if raising eastern white river crawfish (Procambarus acutus
acutus) in the Mid-Atlantic region year-round is economically
feasible. The possibility for economic success, or even survival, will be
examined with the use of a two-stage dynamic-stochastic simulation
modeling framework. Six simulation models were created in ProModel 4.0 to
mimic crawfish farms with different components. Information collected from
the ProModel experiments were then used in @Risk, a Microsoft Excel
add-in, in order to determine the economic viability of crawfish farms
using capital budgeting methods. Preliminary results suggest that crawfish
farming in the Mid-Atlantic region can be feasible, assuming the consumer
demand exists. | ||
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Wintersim |
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| A SIMULATION APPROACH
FOR IMPROVING THE EFFICIENCY OF THE DEPARTMENT OF MOTOR VEHICLES
|
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|---|---|---|
| Yasser
Dessouky Department of Computer, Information, and Systems Engineering San Jose State University San Jose, CA 95192-0180, U.S.A. |
|
Brian
Senkandwa Department of Computer, Information, and Systems Engineering San Jose State University San Jose, CA 95192-0180, U.S.A. |
| ABSTRACT | ||
| Simulation as a primary tool was used to
evaluate the effectiveness of the Santa Teresa Department of Motor
Vehicles, California. The Department of Motor Vehicles was analyzed to
determine improvement methods that would curtail the long customer lines
or queues that are prevalent. A 23 factorial experimental design was
performed to improve overall system effectiveness as measured by time in
the system. With the above tools, a more efficient model of the Santa
Teresa Department of Motor Vehicles was developed and proposed. This paper
describes the developed model used and provides details on the analysis
performed. | ||
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Wintersim |
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| ENHANCING SIMULATION
MODELS FOR EMERGENCY ROOMS USING VBA |
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|---|---|---|
| Adriana M.
Alvarez Martha A. Centeno Department of Industrial and Systems Engineering Florida International University Miami, Florida 33199 |
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| ABSTRACT | ||
| Increased pressure to control costs and
increased competition has prompted health care managers to look for tools
to effectively operate their institutions. Managers are increasingly using
simulation modeling to understand their processes. A simulation model of
an ER has been enhanced with VBA routines, so that it can use real world
data. The simulation model has been complemented with a series of
decision-making routines. These routines use a hierarchical approach to
organize the various scenarios under which the model may run and to
partially reconfigure the ARENA model at run time.
| ||
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Wintersim |
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| CASE STUDY: SIMULATION
OF THE CALL CENTER ENVIRONMENT FOR COMPARING COMPETING CALL ROUTING
TECHNOLOGIES FOR BUSINESS CASE ROI PROJECTION
|
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|---|---|---|
| Katherine
Miller IIT Research Institute 8100 Corporate Drive, Suite 400 Lanham, MD 20785, U.S.A. |
|
Vivek
Bapat Systems Modeling Corporation 504 Beaver Street Sewickly, PA 15143, U.S.A. |
| ABSTRACT | ||
| This paper describes how simulation was
used for business case benefits and return on investment (ROI) projection
for the procurement and rollout of a new call routing technology to 25
call centers. With investment costs of about 17 million dollars and annual
operating costs of about 8 million for the new technology, we needed to
determine if the technology would provide enough cost savings and cost
avoidance (through reduced trunk costs, increased agent productivity, and
ability to service more calls) to warrant its nationwide
implementation. We constructed a model of the existing call center environment consisting of 25 call centers where calls were distributed to the sites based on a system of percentage allocation routing; for example, the telephone network provider directs calls to each site based on the number of agents scheduled. We then modeled the same call system dynamics and intricacies under the new call routing system where calls are distributed based on longest available agent. Subsequently, we conducted average day simulations with light and heavy volumes and other "what if" laboratory analyses and experiments to facilitate planning decisions required to be documented and substantiated in the business case. | ||
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| THREE SOURCES OF
SIMULATION INACCURACY (AND HOW TO OVERCOME THEM)
|
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|---|---|---|
| Stewart
Robinson Operational Research and Systems Group Warwick Business School University of Warwick Coventry, CV4 7AL UNITED KINGDOM |
||
| ABSTRACT | ||
| There is much interest in how to ensure
that the results obtained from a simulation model are accurate. This paper
considers this from the perspective of three main sources of inaccuracy:
the modelling, the data and the experimentation. For each of these sources
the causes of inaccuracy are discussed and some advice is given on how to
overcome them. An illustrative model is used to quantify some of the
effects of inaccuracies in the data and the experimentation.
| ||
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