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Peixia Gao Sabine Wittevrongel Joris Walraevens Herwig Bruneel 《Mathematical Methods of Operations Research》2008,67(2):269-284
In this paper, we study the behavior of a discrete-time multiserver buffer system with infinite buffer size. Packets arrive
at the system according to a two-state Markovian arrival process. The service times of the packets are assumed to be constant,
equal to multiple slots. The behavior of the system is analyzed by means of an analytical technique based on probability generating
functions (PGF’s). Explicit expressions are obtained for the PGF’s of the system contents and the packet delay. From these,
the mean values, the variances and the tail distributions of the system contents and the packet delay are calculated. Numerical
examples are given to show the influence of various model parameters on the system behavior. 相似文献
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Dieter Fiems Stijn De Vuyst Sabine Wittevrongel Herwig Bruneel 《Annals of Operations Research》2009,170(1):113-131
In this contribution we investigate higher-order loss characteristics for M/G/1/N queueing systems. We focus on the lengths of the loss and non-loss periods as well as on the number of arrivals during these
periods. For the analysis, we extend the Markovian state of the queueing system with the time and number of admitted arrivals
since the instant where the last loss occurred. By combining transform and matrix techniques, expressions for the various
moments of these loss characteristics are found. The approach also yields expressions for the loss probability and the conditional
loss probability. Some numerical examples then illustrate our results. 相似文献
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Adsorption - Adsorbent monoliths are gaining increasing interest in gas phase separation processes, but have rarely been studied for liquid phase separations. In this work, we investigate an... 相似文献
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Stereo digital image correlation (stereo-DIC) is being accepted by the industry as a valid full-field measurement technique for measuring shape, motion and deformation, and it is therefore of utmost importance to provide uncertainties on the obtained measurements. However, the influences on a stereo-DIC measurement are not fully understood; indeed, stereo-DIC is a complex optical-numerical process and it is not always clear how errors are propagating throughout the measurement chain. In order to investigate the magnitude of the different error-sources a simulator for stereo-DIC is proposed. This simulator is able to generate realistic synthetic images as if they were made during a real set-up, so the error sources can be investigated separately and an optimal set-up can be chosen before any physical test is performed. We present in this paper the mathematical approach to the DIC simulator including details on how to convert FE displacement field results to stereo-DIC images. The simulator includes the ability to control the lighting and to create synthetic calibration images. The synthetic images are compared to simulations for a bulge test as a validation of the simulator. Synthetic calibration images are compared to experimental calibration studies to verify those. Finally a brief look at how the simulator could be used for looking at calibration quality is conducted. 相似文献
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In FE based global digital image correlation (DIC) a finite element mesh is used to describe the deformation of the region of interest (ROI). However, the identification of an optimal mesh is a difficult problem and is often obtained by using “mechanical” pre-knowledge of the solution. In Finite Element Analysis (FEA) an optimal mesh can be found without any pre-knowledge of the solution by using mesh adaptivity, where an initial (non optimal) mesh is refined until the optimal solution is obtained. Refinement of the mesh can be based on error and/or convergence estimators. Despite the fundamental differences between FEA and DIC, in the present article the convergence procedure is successfully used in a recently published global FE based DIC method. In the used global DIC method elements can receive higher order shape functions, also known as p-elements. Using the aforementioned algorithm, also called p-DIC, refinement to a non-uniform higher order mesh is possible. Using the non-uniform mesh, an optimal mesh can be obtained for each section of the ROI. The presented study shows that a convergence scheme can be used to automatically control the mesh refinement in a global DIC approach. The convergence boundary, in percentage, is a more intuitive boundary than the absolute error boundary used in the original p-DIC approach. The procedure is validated using numerical examples and the robustness to experimental variables is investigated. Finally, the complete procedure is tested against a wide range of practical examples. 相似文献
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Joris Walraevens Dieter Fiems Sabine Wittevrongel Herwig Bruneel 《European Journal of Operational Research》2009
In this paper, we analyze some output characteristics of a discrete-time two-class priority queue by means of probability generating functions. Therefore, we construct a Markov chain which – after analysis – provides a.o. the probability generating functions of the lengths of the busy periods of both classes. It is furthermore shown how performance measures, related to the output process, are calculated from these functions. The queueing model is kept fairly simple to explain the method of analysis of the busy periods and the output characteristics of priority queues as clearly as possible. 相似文献
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In this rejoinder, we respond to the comments and questions of three discussants of our paper on queueing models for the analysis of communication systems. Our responses are structured around two main topics: discrete-time modeling and further extensions of the presented queueing analysis. 相似文献