bluuebunny/crossref_metadata_2025 huggingface dataset:
Modeling the mechanical behavior of railway ballast using artificial neural networks
Authors: Shahin Mohamed A , Indraratna Buddhima
Published: January 2007

Ballast is one of the most commonly used construction materials in railway tracks. Under heavy train loads, ballast is subjected to a high stress level that is always associated with significant track deformation. Consequently, an accurate prediction of the mechanical behavior of ballast under static and dynamic loading conditions is important for the stability of railway tracks. In this paper, the feasibility of using artificial neural networks (ANNs) for modeling the mechanical behavior of railway ballast under static loading is investigated. The database used for the development of the ANN model is obtained from selected literature and comprises a series of 29 large-scale drained triaxial compression tests conducted on three types of commonly used ballast (i.e., basalt, dolomite, and granite). Predictions from the ANN model are compared with the results of experimental tests and with those obtained from the hardening-soil constitutive model in PLAXIS finite-element code. The results indicate that the ANN model is able to accurately predict the stress–strain and volume change behavior of ballast. The plastic dilation and contraction of ballast at various confining pressures and the strain-hardening and postpeak strain-softening behavior of ballast are also well simulated.Key words: ballast, modeling, neural networks, prediction, railway, triaxial tests.
HOW SIZE OF TARGET AVALANCHES INFLUENCES PREDICTION EFFICIENCY
Authors: SHAPOVAL A. B. , SHNIRMAN M. G.
Published: January 2007

Bak, Tang, and Wiesenfeld [Phys. Rev. Lett.59, 381 (1987)] introduced their sand-pile (BTW sand-pile) as the cellular automata coming to their critical state without tuning any inner model parameters. The main model features deal with grains falling slowly onto the two-dimensional lattice and a quick deterministic transport of the superfluous grains to the boundary. The simplest modifications of the BTW sand-pile develop a random transport mechanism instead of a deterministic one. The model transportation of the grains generates avalanches. We find that before the big avalanches the height of the pile increases and the singular grains organize themselves in special clusters. These observations lead to the formal algorithm that predicts the big avalanches in advance with a certain efficiency. However the efficiency for the BTW sand-pile is worse than that for its stochastic modifications.
LOW-TEMPERATURE STUDY OF MAGNETIC BEHAVIOR OF EUROPIUM IN LEAD-BISMUTHATE GLASSES
Authors: POP L. , RISTOIU T. , DEMPSEY N. , CULEA M. , CULEA E.
Published: January 2007

Glasses of the x Eu 2 O 3(1-x)[3 Bi 2 O 3 PbO ] system with x=0–0.25 were prepared and studied using low-temperature magnetization measurements. The obtained data suggest the presence of both Eu 3+ and Eu 2+ ions in the host glass matrix. The determined fraction of the Eu 2+ ions/total number of europium ions was very small (2.1–3.4%). Magnetization data show that the europium ions exert superexchange interactions and show an important clustering tendency.
FUZZY VECTOR OBJECTIVE OPTIMIZATION ALGORITHM FOR IMAGE RECONSTRUCTION FROM INCOMPLETE PROJECTIONS
Authors: GAO XIN , WANG YUANMEI , ZHANG CISHEN
Published: January 2007

This paper deals with the problem of image reconstruction from incomplete projections. A novel fuzzy vector objective optimization model is developed by integrating the fuzzy set theory and vector objective optimization (multi-objective decision-making). The objective function is expressed as a membership function, and the minimum operator is taken as a fuzzy operator. Furthermore, a novel iterative method is proposed to resolve the fuzzy optimization problem. The images reconstructed from simulated noise projections and real projections obtained from an industrial scanner show that the new algorithm can provide higher resolution and better smoothness than the images reconstructed by the transformation method and the conventional iterative method, so it is more feasible for image reconstruction from incomplete projections.
COMPUTATION OF VESSELNESS IN CTA IMAGES FOR FAST AND INTERACTIVE VESSEL SEGMENTATION
Authors: CAI WENLI , HARRIS GORDON J. , YOSHIDA HIROYUKI
Published: January 2007

With the rapid development of multi-detector computed tomography (MDCT) that results in improving the temporal and spatial resolution of patient data, clinical use of computed tomographic angiography (CTA) is increasing. Vessel segmentation can be challenging in CTA, but is needed for isolation of vascular structures. In this paper, a novel method for computation of vesselness in CTA images is presented, including a CTA transfer function prior to the vesselness computation for reducing the artifacts caused by the false-positive responses of a Hessian-based line filter, as well as a hierarchical structure, called MIP-volume pyramid, for accelerating the computation of vesselness. Using the computed vesselness, we present an interactive segmentation method for each individual vessel by applying a vesselness speed function in a fast marching level set method. Our new method was shown to provide an effective and efficient way that allows vesselness to be applied to large CTA images. This method has been implemented successfully in CTA vessel segmentation and evaluation.
A multistrategy approach for digital text categorization from imbalanced documents
Authors: del Castillo M. Dolores , Serrano José Ignacio
Published: January 2007

The goal of the research described here is to develop a multistrategy classifier system that can be used for document categorization. The system automatically discovers classification patterns by applying several empirical learning methods to different representations for preclassified documents belonging to an imbalanced sample. The learners work in a parallel manner, where each learner carries out its own feature selection based on evolutionary techniques and then obtains a classification model. In classifying documents, the system combines the predictions of the learners by applying evolutionary techniques as well. The system relies on a modular, flexible architecture that makes no assumptions about the design of learners or the number of learners available and guarantees the independence of the thematic domain.
Queueing analysis of finite buffer token networks
Authors: Ganz A. , Chlamtac I.
Published: January 2007

This paper introduces analytic models for evaluating demand assignment protocols in realistic finite buffer/finite station network configurations. We present a solution for implicit and explicit token passing systems enabling us to model local area networks, such as Token Bus. We provide, for the first time, a tractable approximate solution by using an approach based on restricted occupancy urn models. The presented approximation involves the solving of
linear
equations whose number is
linear
and equal only to the number of buffers in the system. It is demonstrated that in addition to its simplicity, the presented approximation is also highly accurate.
Performance modelling of a HSLAN slotted ring protocol
Authors: Zafirovic-Vukotic M. , Niemegeers I. G. M. M.
Published: January 2007

The slotted ring protocol which is evaluated in this paper is suitable for use at very large transmission rates. In terms of modelling it is a multiple cyclic server system. A few approximative analytical models of this protocol are presented and evaluated vs the simulation in this paper. The cyclic server model shows to be the most accurate and usable over a wide range of parameters. A performance analysis based on this model is presented.
Analytic derivation of processor potential utilization in straight line, ring, square mesh, and hypercube networks
Authors: Born R. G. , Kenevan J. R.
Published: January 2007

In multicomputer architectures, in which processors communicate through message-passing, the overhead encountered because of the need to relay messages can significantly affect performance. Based upon some simplifying assumptions including the rate at which a processor generates messages being proportional to its current potential utilization, processor utilizations are analytically derived in matrix form for a bidirectional straight line and square mesh. In addition, closed form derivations are provided for a unidirectional ring and an n-dimensional hypercube. Finally, the theoretical results are found to be in close agreement with discrete-event simulations of the four architectures.
Scheduling in multiprogrammed parallel systems
Authors: Majumdar S. , Eager D. L. , Bunt R. B.
Published: January 2007

Processor scheduling on multiprocessor systems that simultaneously run concurrent applications is currently not well-understood. This paper reports a preliminary investigation of a number of fundamental issues which are important in the context of scheduling concurrent jobs on multiprogrammed parallel systems. The major motivation for this research is to gain insight into system behaviour and understand the basic principles underlying the performance of scheduling strategies in such parallel systems. Based on abstract models of systems and scheduling disciplines, several high level issues that are important in this context have been analysed.
Performance analysis of multipath multistage interconnection networks
Authors: Kothari S. C. , Jhunjhunwala A. , Mukherjee A.
Published: January 2007

This paper closely examines the performance analysis for unbuffered multipath multistage interconnection networks. A critical discussion of commonly used analysis is provided to identify a basic flaw in the model. A new analysis based on the grouping of alternate links is proposed as an alternative to rectify the error. The results based on the new analysis and extensive simulation are presented for three representative networks. The simulation study strongly supports the results of the new analysis.
Sensitivity analysis of reliability and performability measures for multiprocessor systems
Authors: Blake J. T. , Reibman A. L. , Trivedi K. S.
Published: January 2007

Traditional evaluation techniques for multiprocessor systems use Markov chains and Markov reward models to compute measures such as mean time to failure, reliability, performance, and performability. In this paper, we discuss the extension of Markov models to include parametric sensitivity analysis. Using such analysis, we can guide system optimization, identify parts of a system model sensitive to error, and find system reliability and performability bottlenecks.

As an example we consider three models of a 16 processor. 16 memory system. A network provides communication between the processors and the memories. Two crossbar-network models and the Omega network are considered. For these models, we examine the sensitivity of the mean time to failure, unreliability, and performability to changes in component failure rates. We use the sensitivities to identify bottlenecks in the three system models.
Monitoring and performance measuring distributed systems during operation
Authors: Wybranietz D. , Haban D.
Published: January 2007

This paper describes an integrated tool for monitoring distributed systems continuously during operation. A hybrid monitoring approach is used. As special hardware support a test and measurement processor (TMP) was designed, which is part of each node in an experimental multicomputer system. Each TMP runs local parts of the monitoring software for its node, while all the TMPs are connected to a central test station via a separate TMP interconnection network. The monitoring system is transparent to users. It permanently observes system behavior, measures system performance and records system information. The immense amount of information is graphically displayed in easy-to-read-charts and graphs in an application-oriented manner. The tools promote an improved understanding of run time behavior and performance measurements to derive qualitative and even quantitative assessments about distributed systems. A prototype of the monitoring facility is operational and currently experiments are being conducted in our distributed system consisting of several MC68000 microcomputers.
Feedback coupled resource allocation policies in the multiprogramming-multiprocessor computer system
Authors: Brice Richard S. , Browne J. C.
Published: January 2007

This paper presents model studies of some integrated feedback-driven scheduling systems for a multiprogrammed computer system.

This abstract can present only the conclusions of the studies and little of the supporting data and detail.

The basic format of the analysis is to fix a size for the local buffers and a total size for the collection buffers, to define a set of algorithms for the determination of the data removal quanta to the local buffers, the allocation of space in the collection buffers, and the look-ahead mechanism for input and then to evaluate the relative merits of the various strategies by the resulting CPU efficiency.

Three feedback algorithms are studied as examples in this work.
Develop your computer performance pattern
Authors: Noe J. D. , Runstein N. W.
Published: January 2007

Is the load on your computer shifting? Did that change to faster access disks really help? Would more core memory increase throughput appreciably, or would it be necessary to also increase central processor power? These are three quite different kinds of questions; one concerns detecting a long-term trend, another assessing the effects of a system change, and a third estimating effects of the decision to alter the configuration. Yet all of these require knowledge of current and past system performance, the type of knowledge that must be the result of long-term performance monitoring. This is not simple enough to be picked up overnight or in one series of experiments, nor can it be assessed by watching one or two parameters over a long period. One must have a thorough understanding of the pattern of performance by knowing the mean values of a number of measures and knowing something about the variations from these means.

This paper hardly needs to recommend that computer managers establish an understanding of performance pattern; they already are very conscious of the need. What it does is recount development of a method of doing so for the CDC 6400 at the University of Washington and of the selection of “Kiviat Graphs” as a means to present data in a synoptic form.

The remainder of this paper will give a brief account of the authors' experience in designing a measurement system for the CDC 6400 at the University of Washington Computer Center. This will include comments on the approach to deciding what to measure an d display for the synoptic view of the system, as well as how to provide more detailed data for backup. Examples of the use of Kiviat Graphs [4] to show the effects of load shift and of a system configuration change are included, and the effect of a change of operating system will be noted.
An adaptive policy driven scheduler
Authors: Sharp Joseph C. , Roberts James N.
Published: January 2007

The theory of policy driven schedulers (Ref. [1]) is extended to cover cases in which the scheduling parameters are allowed to adapt dynamically as the system's job load varies. The system under consideration offers batch, time sharing and limited real time services. Data from simulated and live loads are presented to evaluate both the static and the adaptive schedulers.

A policy driven scheduler makes its decisions with respect to a set of policy functions, f
i
(t). Each of the policy functions corresponds to a different type of user and specifies the amount of computing resources that the system will try to give a user in that group within a given total amount of elapsed time.

It is found that the policy functions must be set conservatively in order to avoid response problems during periods of heavy load, but that during more lightly loaded periods the conservative settings result in widely disparate rates of service to similar jobs. One solution is to vary the policy functions as the job load changes.

A dynamic algorithm is presented that maintains responsiveness during heavy loads and provides fairly uniform service rates at other times.
A Software Quality Improvement Program
Authors: Woodmancy Donald A.
Published: January 2007

In late 1976, the NCR Corporation undertook a large scale Quality Improvement Program for a major set of systems software. That software set included some 103 separate products totaling 1.3 million source lines. It included several operating systems, several compilers, peripheral software, data utilities and telecommunications handlers. This paper will describe that effort and its results. The research and planning that were done to define the program will be described. The means by which the program was implemented will be discussed in detail. Finally, some results of the program will be identified.
Toward models for probabilistic program correctness
Authors: Duran Joe W. , Wiorkowski John J.
Published: January 2007

Program testing remains the major way in which program designers convince themselves of the validity of their programs. Software reliability measures based on hardware reliability concepts have been proposed, but adequate models of software reliability have not yet been developed. Investigators have recently studied formal program testing concepts, with promising results, but have not seriously considered quantitative measures of the “degree of correctness” of a program. We present models for determining, via testing, such probabilistic measures of program correctness as the probability that a program will run correctly on randomly chosen input data, confidence intervals on the number of errors remaining in a program, and the probability that the program has been completely tested. We also introduce a procedure for enhancing correctness estimates by quantifying the error reducing performance of the methods used to develop and debug a program.
Are current approaches sufficient for measuring software quality?
Authors: Bowen John B.
Published: January 2007

Numerous software quality studies have been performed over the past three years-mostly sponsored by the Rome Air Development Center. It is proposed by the author that more emphasis should be placed on devising and validating quantitative metrics that are indicative of the quality of software when it is being designed and coded. Such measures could be applied effectively, as relative guidelines without formal validation. However for such measures to be predictive of the quality of the delivered software, they must be validated with actual operational error data or data gathered in a simulated operational environment. This paper includes a review of proposed metrics from the literature a report of a Hughes intramodule metric study, and recommendations for refining proposed software quality assurance criteria.
Responding to MIL-S-52779
Authors: Southworth Richard N.
Published: January 2007

The art and science of computer software development is still changing considerably from year to year, and therefore lacks the established control mechanisms of hardware production programs. Also, because most software is produced in a one-time development program it does not lend itself to the established discrepancy detection and correction techniques used in hardware production programs. Consequently, the software QA program must providethe methodology to detect a deficiency the first time it occurs and effect corrective action.

MIL-S-52779: “Software Quality Assurance Program Requirements,” has provided a much needed impetus for software development contractors to develop software QA techniques. But much remains to be done. As the state of the art advances MIL-S-52779 should be revised accordingly. In this paper the author responds to the present form of the specification, suggests some revisions and additions and briefly discusses a set of QA procedures that should be responsive (fully compliant) with MIL-S-52779.
Simulated execution of dataflow programs on processors having finite resources
Authors: Langan David D. , Shriver Bruce D.
Published: January 2007

Dataflow languages and processors are currently being extensively studied because they provide for the specification and realization of processes exhibiting a high degree of parallel and/or asynchronous activity [12, 8]. Several researchers have developed simulators for specific candidate dataflow architectures in which there are essentially an infinite number of resources available to the nost machine [9, 1]. This is done to study the degree of parallelism which is achievable with a given version of an algorithm. However, it is an equally important (and neglected) area to study the behavior of programs executing in candidate computer systems having a finite amount of resources. This paper presents results which have been obtained from such modeling. It is shown that in such a system certain “critical nodes” must be given priority of execution when competing with other nodes for the same resources in order to achieve the maximum system throughput. It is suggested that the abstract dataflow model be modified to accommodate such situations. Various design trade-offs associated with the implementation of the simulator are discussed along with a description of available features. A companion paper [6] describes the general dataflow simulation facility which provided the basis of this work.
An operating system implementation and simulation language (OASIS)
Authors: Unger Brian W. , Parker James R.
Published: January 2007

An approach to the implementation and simulation of system software for multicomputer architectures is described. OASIS, a variant of the SIMULA 67 language, provides tools for both hardware modelling and system software development. The latter includes an extensible module type with flexible intermodule access control. Hardware is characterized at the processor/memory level so that system software resource control and allocation policies can be implemented at a functional level. Concurrent module execution by multiple processors, with or without shared memory, can be simulated directly. The OASIS modules in such a simulation can closely parallel the structure of actual system software. Thus, once a design is shown viable by simulation, the implementation of actual software can be a simple translation of OASIS modules. A brief overview of OASIS features is presented followed by a simple example.
Models for specification and anaysis of parallel computing systems
Authors: Mattheyses R. M. , Conry S. E.
Published: January 2007

The problem of designing a properly functioning parallel hardware or software system is considerably more difficult than that of designing a similar sequential system. In this paper we formulate criteria which a design methodology for parallel systems should satisfy and explore the use of various models as the basis for such a design tool.
Performance evaluation of communicating processes
Authors: Gertner Ilya
Published: January 2007

This paper concerns the performance evaluation of an operating system based on communicating processes. Processes communicate via messages and there is no shared data.

Execution of a program is abstracted as a sequence of events to denote significant computational steps. A finite state machine model of computation is used for the specifications of abstract computational properties and, thereafter, for the selective analysis of measurement data.

A set of conventions is developed to characterize the performance of communicating processes. A hierarchical layering technique is used to concisely describe the characteristics of large systems.

A performance monitoring system was implemented and applied to the analysis of RIG, a message-based operating system.
Field performance aids for IBM GSD systems
Authors: Stroebel Gary
Published: January 2007

A series of field performance aids have been developed to assist IBM Systems Engineers evaluate the performance of System/3, System/34, and System/38 configurations. Use of those aids is appropriate at proposal time, for preinstallation design, for tuning, and for upgrade studies. This paper overviews some of the key features of these aids as they pertain to the user interface, workload characterization, and performance models.
XRAY
Authors: Blake Russ
Published: January 2007

XRAY presents a global view of the performance of hardware and software components on multiple, distributed computers. The set of components chosen for measurement can be changed at any time throughout a network of systems, and can be selected to minimize data collection time and measurement space. In the course of normal activities the operating system executes firmware which increments counters for the measured components. Periodically, the counters are recorded in an ordinary file by a process in each processor. An analysis program permits browsing through components and plotting counters in real time. Analysis focuses on detecting the distributed sources of excessive activity.
Methodology and empirical results of program behaviour measurements
Authors: Alanko Timo O. , Haikala Ilkka J. , Kutvonen Petri H.
Published: January 2007

Program behaviour characteristics were examined using data gathered from real program executions. Experiments were performed in a segmented virtual memory with a working set policy; the analyzing costs were kept low using an efficient data reduction method. Empirical results were obtained concerning the influence of the window size on program behaviour characteristics, the accuracy of some average working set size approximations and the sensitivity of program behaviour to the program's input data. These results show that some commonly used assumptions concerning program behaviour are inaccurate. Also there seem to exist “ill-behaving” programs, the behaviour of which does not correspond well with results obtained earlier. The effects of real-time delays during program execution were considered using a new simple method. As an additional experiment, segmenting and paging were compared using various performance statistics; the results seem to favour segmenting.
Near-complete decomposability of queueing networks with clusters of strongly interacting servers
Authors: Vantilborgh Hendrik T. , Garner Richard L. , Lazowska Edward D.
Published: January 2007

The near-complete decomposability of queueing network models of computer systems is generally supported by very large differences in the service rates of the servers. In this paper we show how such models may still be nearly completely decomposable if on the one hand these large differences can no longer be realistically assumed (as is the case, for example, in computer networks) but if on the other hand clusters of strongly interacting servers exist.

Our results may be viewed as a bridge between the approaches to the approximate analysis of queueing networks advanced by Courtois and by Chandy, Herzog and Woo, since we show circumstances under which the former approach leads to exactly the same method of analysis as the latter. In contrast to the Chandy, Herzog and Woo theorem, however, the theory of near-complete decomposability does not rely on the beneficent properties of queueing networks exhibiting product form solutions. Thus our results may point the way towards the theoretically sound application of simple and intuitively appealing approximate analysis techniques to non - product form networks.
On the existence of composite flow equivalent markovian servers
Authors: Stewart William J. , Zeiszler Gerald A.
Published: January 2007

Queueing networks have been used to model a large variety of complex systems. However, once a realistic model has been constructed it has generally been necessary to distort and modify it so that an analytic solution could be obtained. Unfortunately, the analytic solution often has little relation to the original queueing system and consequently often produces solutions with poor accuracy.

We begin with a brief introduction to the concepts of decomposition and aggregation. Application of these and other approximate methods to the analysis of computer systems are discussed by Chandy and Sauer [CHAN78].
Overallocation in a virtual circuit computer network
Authors: Kurinckx A. , Pujolle G.
Published: January 2007

In this paper, we study the end-to-end control through virtual circuits in a computer network built following the X.25 Recommendations. We develop a mathematical model to obtain the maximum overallocation of node buffers, in order for the probability of overflow not to exceed a given value.
Performance evaluation of a feedback data flow processor using simulation
Authors: Dhas C. Retna
Published: January 2007

This paper presents a method to estimate the performance of a feedback data flow processor using software simulation. A brief over view of a data flow language and a data flow processor along with the conceptual view of a software simulator are described. Numerical measurements of parallelism and resources requirements are obtained by translating high level language programs to data flow language and then executing them on the simulator.
Response time distributions for a multi-class queue with feedback
Authors: Lam Simon S. , Shankar A. Udaya
Published: January 2007

A single server queue with feedback and multiple customer classes is analyzed. Arrival processes are independent Poisson processes. Each round of service is exponentially distributed. After receiving a round of service, a customer may depart or rejoin the end of the queue for more service. The number of rounds of service required by a customer is a random variable with a general distribution. Our main contribution is characterization of response time distributions for the customer classes. Our results generalize in some respects previous analyses of processor-sharing models. They also represent initial efforts to understand response time behavior along paths with loops in local balanced queueing networks.
Aspects of software design analysis
Authors: Smith Connie , Browne J. C.
Published: January 2007

This paper extends previous work on development of a methodology for the prediction of the performance of computer software systems from design level specifications and continuing through implementation. The effects of synchronized behavior, such as results from data reservation in multi-thread executions of data base systems, and competition for host system resources are incorporated. The previous methodology uses hierarchical graphs to represent the execution of software on some host computer system (or on some abstract machine). Performance metrics such as response time were obtained from analysis of these graphs assuming execution of a single copy on a dedicated host. This paper discusses the mapping of these execution graphs upon queueing network models of the host computing environment to yield performance metric estimates for more complex and realistic processing environments.
On the relationships among three software metrics
Authors: Henry Sallie , Kafura Dennis , Harris Kathy
Published: January 2007

Automatable metrics of software quality appear to have numerous advantages in the design, construction and maintenance of software systems. While numerous such metrics have been defined, and several of them have been validated on actual systems, significant work remains to be done to establish the relationships among these metrics. This paper reports the results of correlation studies made among three complexity metrics which were applied to the same software system. The three complexity metrics used were Halstead's effort, McCabe's cyclomatic complexity and Henry and Kafura's information flow complexity. The common software system was the UNIX operating system. The primary result of this study is that Halstead's and McCabe's metrics are highly correlated while the information flow metric appears to be an independent measure of complexity.
Predicting numbers of errors using software science
Authors: Ottenstein Linda
Published: January 2007

An earlier paper presented a model based on software science metrics to give quantitative estimate of the number of bugs in a programming project at the time validation of the project begins. In this paper, we report the results from an attempt to expand the model to estimate the total number of bugs to expect during the total project development. This new hypothesis has been tested using the data currently available in the literature along with data from student projects. The model fits the published data reasonably well, however, the results obtained using the student data are not conclusive.
A software study using Halstead metrics
Authors: Bailey C. T. , Dingee W. L.
Published: January 2007

This paper describes an application of Maurice Halstead's software theory to a real time switching system. The Halstead metrics and the software tool developed for computing them are discussed. Analysis of the metric data indicates that the level of the switching language was not constant across algorithma and that software error data was not a linear function of volume.
SCAT
Authors: Neuse D. , Chandy K.
Published: January 2007

This paper presents a new algorithm for the approximate analysis of closed product-form queueing networks with fixed-rate, delay (infinite-server), and load-dependent queues. This algorithm has the accuracy, speed, small memory requirements, and simplicity necessary for inclusion in a general network analysis package. The algorithm allows networks with large numbers of queues, job classes, and populations to be analyzed interactively even on microcomputers with very limited memory.
Aggregation of stations in queueing network models of multiprogrammed computers
Authors: Thomasian Alexander , Nadji Behzad
Published: January 2007

In queueing network models the complexity of the model can be reduced by aggregating stations. This amounts to obtaining the throughput of the flow-equivalent station for the subnetwork of stations to be aggregated. When the subnetwork has a separable solution, aggregation can be carried out using the Chandy-Herzog-Woo theorem. The throughput of the subnetwork can be expressed explicitly in terms of its parameters when the stations are balanced (have equal utilizations). This expression for throughput can be used as an approximation when the stations are relatively unbalanced. The basic expression can be modified to increase the accuracy of the approximation. A generating function approach was used to obtain upper bounds on the relative error due to the basic approximation and its modifications. Provided that the relative error bound is tolerable, a set of unbalanced stations can be replaced by a single aggregate station or a set of balanced stations. Finally, we propose a methodology to simplify the queueing network model of a large-scale multiprogrammed computer, which makes use of the previous aggregation results.
The effects of solid state paging devices in a large time-sharing system
Authors: Sanguinetti John
Published: January 2007

This paper reports the results of some measurements taken on the effects two new solid state paging devices, the STC 4305 and the Intel 3805, have on paging performance in the Michigan Terminal System at the University of Michigan. The measurements were taken with a software monitor using various configurations of the two solid state devices and the fixed head disk, which they replace. Measurements were taken both during regular production and using an artificial load created to exercise the paging subsystem. The results confirmed the expectation that the solid state paging devices provide shorter page-in waiting times than the fixed-head disk, and also pointed up some of the effects which their differing architectures have on the system.
Performance of cache-based multiprocessors
Authors: Briggs Fayé A. , Dubois Michel
Published: January 2007

A possible design alternative to improve the performance of a multiprocessor system is to insert a private cache between each processor and the shared memory. The caches act as high-speed buffers, reducing the memory access time, and affect the delays caused by memory conflicts. In this paper, we study the performance of a multiprocessor system with caches. The shared memory is pipelined and interleaved to improve the block transfer rate, and assumes an L-M organization, previously studied under random word access. An approximate model is developed to estimate the processor utilization and the speedup improvement provided by the caches. These two parameters are essential to a cost-effective design. An example of a design is treated to illustrate the usefulness of this investigation.
Modular expansion in a class of homogeneous networks
Authors: Mink Alan , Silio Charles B.
Published: January 2007

We consider a special class of homogeneous computer network comprising several essentially identical but independent computing systems (ICSs) sharing a single resource. Of interest here are the effects of modularly expanding the network by adding ICSs. We use a previously presented approximate queueing network model to analyze modular expansion in this class of network. The performance measure used in this analysis is the mean cycle time, which is the mean time between successive requests for service by the same job at the CPU of an ICS. In this analysis we derive an intuitively satisfying mathematical relation between the addition of ICSs and the incremental increase in the service rate of the shared resource required to maintain the existing level of system performance.
Network performance reporting
Authors: Terplan K.
Published: January 2007

Managing networks using Network Administration Centers is increasingly considered. After introducing the information demand for operational, tactical and strategic network management the paper is dealing with the investigation of the applicability of tools and techniques for these areas. Network monitors and software problem determination tools are investigated in greater detail. Also implementation details for a multihost-multinode network including software and hardware tools combined by SAS are discussed.
Questions for Local Area Network panelists
Authors: Spiegel Mitchell G.
Published: January 2007

Much has been written and spoken about the capabilities of emerging designs for Local Area Networks (LAN's). The objective for this panel session was to gather together companies and agencies that have brought LAN's into operation. Questions about the performance of LANs have piqued the curiosity of the computer/communications community.

Each member of the panel briefly described his or her LAN installation and workload as a means of introduction to the audience. Questions about performance were arranged into a sequence by performance attributes. Those attributes thought to be of greatest important were discussed first. Discussion on the remainder of the attributes continued as time and audience interaction permitted.
Toward a parametric approach for modeling local area network performance
Authors: Mager Peter S.
Published: January 2007

The task of modeling the performance of a single computer (host) with associated peripheral devices is now well understood [Computer 80]. In fact, highly usable tools based on analytical modeling techniques are commercially available and in widespread use throughout the industry. [Buzen 78] [Buzen 81] [Won 81] These tools provide a mechanism for describing computerized environments and the workloads to be placed on them in a highly parameterized manner. This is important because it allows users to describe their computer environments in a structured way that avoids unnecessary complexity. It also is helpful in facilitating intuitive interpretations of modeling results and applying them to capacity planning decisions.

A first step toward building a modeling tool and associated network specification language that allows straightforward, inexpensive, and interpretable modeling of multi-computer network performance is to identify the set of characteristics (parameters) that most heavily influence that performance. The result of such a study for the communication aspects of local area networks is the subject of this paper.
Score '82 - a summary (at IBM systems research institute, 3/23-3/24/82)
Authors: Gaffney John E.
Published: January 2007

“Score '82”, the first workshop on software counting rules, was attended by practitioners who are working with “software metrics”. The concern was with methodologies for counting such software measurables as the number of “operators”, “operands” or the number of lines of code in a program. A “metric” can be a directly countable “measurable” or a quantity computable from one or several such “measureables”. “Metrics” quantify attributes of the software development process, the software itself, or some aspect of the interaction of the software with the processor that hosts it. In general, a “metric” should be useful in the development of software and in measuring its quality. It should have some theory to support its existence, and it should be based on actual software data. This workshop was concerned principally with the data aspects of “metrics”, especially with the rules underlying the collection of the data from which they are computed.
Hankel matrices and computer algebra
Authors: Sendra Juan R.
Published: January 2007

In this paper we show some results concerning symbolic manipulation of Hankel matrices, as well as some applications of these matrices to Computer Algebra. We present algorithmic approaches, based on Hankel matrices, to the calculation of multivariate polynomial resultants, to polynomial
gcd
computations including the extended polynomial
gcd
problem, to modular factorization and to the determination of the number of distinct real roots of a real polynomial. The computing time analysis shows that the three first applications have the same asymptotic complexity as the currently fastest algorithm for these problems, and that the last one runs in
O
(
n
5
log
2
L
) where
n
is the degree of the polynomial, and
L
its norm.
Table of special function integrals
Authors: Pigquette Jean C.
Published: January 2007

This paper is the result of a suggestion by B. F. Caviness [1] to publish a table of integrals obtained using the special function integration technique that has been described in detail elsewhere [2]-[8], since only a much abbreviated version of the table could be accommodated in [7]. This integration technique permits symbolic evaluation of integrals of the form[EQUATION]where f(x) is an essentially arbitrary function and IIR is a product of any of a very broad class of special functions including, but not limited to, Bessel functions, Legendre functions, Hermite functions, Laguerre functions, Chebychev polynomials, Jacobi polynomials, and Gegenbauer polynomials. In [7] is described a method which can be used to enhance the on-board integrator of a symbolic software system to include analytical symbolic evaluation of integrals of this type. The method is currently being evaluated for possible inclusion in the program
Mathematica
™ [9].
Recognition of Hurwitz polynomials
Authors: Trevisan Vilmar
Published: January 2007

An algorithm for recognizing Hurwitz polynomials is presented. It uses a recent result due to Beauzamy and the Euclidean algorithm. Some machine examples with timing are included.
Managing objects in a user interface system with ROBA
Authors: Hiraga Rumi , Lien Yeong-Chang
Published: January 2007

Relational OBject Architecture (ROBA) is a software architecture designed for efficient management of user interface objects in the Mugen system [LHMM89]. Mugen, created at IBM's Tokyo Research Laboratory, is a prototype system for an application development environment, which has the paradigm of generating new applications from provided existing integrated applications. Figure 1 shows a dialogue panel of a new application created in Mugen. There are three boxes for entry points of tasks. A user can dynamically change, add, or delete a task box through Mugen's user interface system, which has the following features: (1) the user interface is created in a WYSIWYG manner, and (2) the layout object can link to a task, which carries out a recorded sequence of a user's operations on applications. The system for building a user interface in Mugen is called the
user interface enabler
.
Stochastic traffic engineering for demand uncertainty and risk-aware network revenue management
Authors: Mitra Debasis
Published: January 2007

Stochastic traffic engineering for demand uncertainty and risk-aware network revenue management We present a stochastic traffic engineering framework for optimizing bandwidth provisioning and route selection in networks. Traffic demands are uncertain and specified by probability distributions, and the objective is to maximize a risk-adjusted measure of network revenue that is generated by serving demands. Considerable attention is given to the appropriate measure of risk in the network model. We also advance risk-mitigation strategies. The optimization model, which is based on mean-risk analysis, enables a service provider to maximize a combined measure of mean revenue and revenue risk. The framework is intended for off-line traffic engineering, which takes a centralized view of network topology, link capacity and demand. We obtain conditions under which the optimization problem is an instance of convex programming. We study the properties of the solution and show that it asymptotically meets the stochastic efficiency criterion.In our numerical investigations we illustrate the impact of demand uncertainty on various aspects of the optimally traffic engineered solutions. The service provider's tolerance to risk is shown to have a strong influence on the traffic engineering and revenue management decisions. We develop the efficient frontier, which is the set of Pareto optimal pairs of mean revenue and revenue risk, to aid the service provider in selecting its operating point.
Multi-dimensional storage virtualization
Authors: Huang Lan , Peng Gang , Chiueh Tzi-cker
Published: January 2007

Most state-of-the-art commercial storage virtualization systems focus only on one particular storage attribute, capacity. This paper describes the design, implementation and evaluation of a
multi-dimensional storage virtualization
system called Stonehenge, which is able to virtualize a cluster-based physical storage system along multiple dimensions, including bandwidth, capacity, and latency. As a result, Stonehenge is able to multiplex multiple virtual disks, each with a distinct bandwidth, capacity, and latency attribute, on a single physical storage system as if they are separate physical disks. A key enabling technology for Stonehenge is an efficiency-aware real-time disk scheduling algorithm called dual-queue disk scheduling, which maximizes disk utilization efficiency while providing Quality of Service (QoS) guarantees. To optimize disk utilization efficiency, Stonehenge exploits run-time measurements extensively, for admission control, computing latency-derived bandwidth requirement, and predicting disk service time.
On performance bounds for the integration of elastic and adaptive streaming flows
Authors: Bonald Thomas , Proutière Alexandre
Published: January 2007

We consider a network model where bandwidth is fairly shared by a dynamic number of elastic and adaptive streaming flows. Elastic flows correspond to data transfers while adaptive streaming flows correspond to audio/video applications with variable rate codecs. In particular, the former are characterized by a fixed size (in bits) while the latter are characterized by a fixed duration. This flow-level model turns out to be intractable in general. In this paper, we give performance bounds for both elastic and streaming traffic by means of sample-path arguments. These bounds present the practical interest of being insensitive to traffic characteristics like the distributions of elastic flow size and streaming flow duration.