Showing papers in "CTIT technical reports series in 1995"

The discrete time ToolBus

Abstract: The notion of “time” plays an important role when coordinating large, heterogeneous, distributed software systems. We present a generic coordination architecture that supports relative and absolute, discrete time. First, we briefly sketch the ToolBus coordination architecture. Next, we give a major example of its use: a distributed auction. Finally, we present the theory underlying our notion of discrete time.

Empirical Edgeworth expansions for symmetric statistics

Abstract: In this paper the validity of a one-term Edgeworth expansion for Studentized symmetric statistics is proved. We propose jackknife estimates for the unknown constants appearing in the expansion and prove their consistency. As a result we obtain the second-order correctness of the empirical Edgeworth expansion for a very general class of statistics, including $U$-statistics, $L$-statistics and smooth functions of the sample mean. We illustrate the application of the bootstrap in the case of a $U$-statistic of degree two.

Error Estimation for Numerical Differential Equations

Abstract: Given a capable human being and a computer, it is possible to make an approximation to the solution of a nonlinear differential equation. However, under the (usually correct) assumption that the equation is analytically intractable, the result of the computation is not the exact solution; indeed it may be so far from the exact solution as to be completely useless. We are interested in the relationship between the effort expended by the human and the computer, and the duality of the computed approximation to a partial or ordinary differential equation. To be specific, we would like to think in terms of a cost-benefit analysis. The cost of the computation is a combination of the human effort and computer resources used to obtain the approximation. The benefit includes, of course, the computed approximation, but it also includes an estimate of the quality of the approximation, that is, an error estimate. It is our opinion that in computational science, as with the experimental sciences, results should always be presented with some estimate of their accuracy. In addition, however, there is another facet to error estimation: one cannot even attempt a cost-benefit analysis or efficiency comparison of methods without an error estimate to evaluate the results.

On a key sampling formula relating the Laplace and Z transforms

Abstract: This note provides a new, rigorous derivation of a key sampling formula for discretizing an analogue system. The required conditions are formulated in time-domain, and give a clear characterization of the classes of signals and systems to which the formula applies.

TransLog, an interactive tool for transformation of logic programs

Abstract: This report describes`TransLog', a prototype of a transformation tool for logic programs. The tool has been developed with the ASF+SDF Meta{environment, a programming environment generator tool based on algebraic speciication. TransLog supports the interactive transformation of (a part of) a program by means of buttons representing transformation rules. This report contains the complete annotated algebraic speciication of TransLog.

Calculation of the TeV prompt muon component in very high energy cosmic ray showers

Abstract: HEMAS-DPM is a Monte Carlo for the simulation of very high energy cosmic ray showers, which includes the DPMJET-II code based on the two component Dual Parton Model. DPMJET-II provides also charm production in agreement with data and, for p ⊥ exceeding 5 GeV/ c , with perturbative QCD results in proton-proton interactions. In this respect, a new scheme has been considered for the inclusive production of D mesons at large p ⊥ in hadronic collisions in the framework of perturbative fragmentation functions, allowing an analysis at the Next to Leading Order (NLO) level which goes beyond the fixed I ( α s 3 ) perturbative theory of open charm production. We have applied HEMAS-DPM to the calculation of the prompt muon component for E μ ≥ 1 TeV in air showers considering the two extreme cases of primary protons and Fe nuclei.

Special functions and q-commuting variables

Abstract: This paper is mostly a survey, with a few new results. The first part deals with functional equations for q-exponentials, q-binomials and q-logarithms in q-commuting variables and more generally under q-Heisenberg relations. The second part discusses translation invariance of Jackson integrals, q-Fourier transforms and the braided line.

Efficient simulation of consecutive cell loss in ATM networks

Abstract: In some B-ISDN applications running on ATM networks (e.g., for audio/video connections), the occasional loss of a single ATM cell may not affect the user’s perceived QoS requirement. However, the QoS may be degraded due to the loss of a multiple (consecutive) ATM cells. As the event of consecutive cell loss is (typically) rare, its probability cannot be estimated efficiently using standard simulation. In this paper we propose a fast simulation method, based on importance sampling, to efficiently estimate the probability of a rare consecutive-cell-loss event. As an example, we consider a queueing model of the Leaky Bucket source policing algorithm, operating in a bursty traffic environment. We present empirical results to demonstrate the validity and effectiveness of our fast simulation method.

Basic proof skills for computer science students

Abstract: Computer science students need mathematical proof skills. At our University, these skills are being taught as part of various mathematics and computer science courses. To test the skills of our students, we have asked them to work out a number of exercises. We found that our students are not as well trained in basic proof skills as we would have hoped. The main reason is that proof skills are not emphasized enough. Our findings are the result of a small experiment using a longitudinal measurement of skills. This method gives better insight in the skills of students than more traditional exam-based testing methods. Longitudinal measurement does not allow the students to specifically prepare themselves for particular questions. The measurements thus relate to skills that are retained for a longer period of time.

Lithium Ion Aqueous Cells.

Abstract: : Lithium ion aqueous cells were investigated using lithium intercalating compounds as anodes and cathodes. The aqueous electrolyte consisted of 4 to 5 molar solutions of either lithium perchlorate or lithium nitrate which contained lithium hydroxide in millimolar amounts to make the solutions slightly basic with a pH of about 8.5. Several electrode combinations were evaluated using lithium intercalating compounds such as lithium cobalt oxide and lithium manganese oxide as cathodes and lithium vanadium oxide, lithium manganese oxide, titanium disulfide, and molybdenum dioxide as the anodes. The cell employing manganese oxide as both the anode and cathode exhibited good charge-discharge characteristics with an open circuit potential of about one volt. jg

Nonparametric deconvolution for decreasing kernels

Abstract: A selection of these reports is available in PostScript form at the Faculty's anonymous ftp-Abstract A new nonparametric estimation procedure is introduced for a class of deconvolution problems where the convolution kernel is decreasing on 0; 1). The estimator is shown to be consistent and its cube root asymptotic distribution theory is established.

Generalized cross validation for wavelet thresholding

Abstract: Noisy data are often fitted using a smoothing parameter, controlling the importance of two objectives that are opposite to a certain extent. One of these two is smoothness and the other is closeness to the input data. The optimal value of this paramater minimizes the error of the result (as compared to the unknown, exact data), usually expressed in the L2 norm. This optimum cannot be found exactly, simply because the exact data are unknown. In spline theory, the generalized cross validation (GCV) technique has proved to be an effective (though rather slow) statistical way for estimating this optimum. On the other hand, wavelet theory is well suited for signal and image processing. This paper investigates the possibility of using GCV in a noise reduction algorithm, based on wavelet-thresholding, where the threshold can be seen as a kind of smoothing parameter. The GCV method thus allows choosing the (nearly) optimal threshold, without knowing the noise variance. Both an original theoretical argument and practical experiments are used to show this successful combination.

Analysis and Synthesis of Environmental Sounds

Abstract: This technical report describes steps toward synthesis of environmental sounds like impact, bouncing, breaking, scraping and other impact sounds.

An annotated bibliography of human factors literature in intelligent transportation systems

Abstract: This document is an annotated bibliography of the human factors literature related to Intelligent Transportation Systems (ITS). It contains over 500 references and includes a keyword index.

Assertional verification of a connection management protocol

Abstract: This paper deals with the verification of a connection management protocol which uses timestamps and network-wide synchronized clocks for the reliable opening and closing of connections. We prove the correctness of the protocol over an unreliable, bounded-delay network for the cases when (i) timestamps are unbounded; (ii) timestamps are from a finite modulo-N space. We determine the minimal safe value of N as a function of real-time parameters such as maximum packet lifetime, clock skew and maximum connection duration.