Wyniki wyszukiwania - BazTech

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Optimization of the service strategy in a queueing system with energy harvesting and customers’ impatience

Dudin A., Lee M. H., Dudin S.

International Journal of Applied Mathematics and Computer Science

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2016

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Vol. 26, no. 2

367--378

EN

A single-server queueing system with an infinite buffer is considered. The service of a customer is possible only in the presence of at least one unit of energy, and during the service the number of available units decreases by one. New units of energy arrive in the system at random instants of time if the finite buffer for maintenance of energy is not full. Customers are impatient and leave the system without service after a random amount of waiting time. Such a queueing system describes, e.g., the operation of a sensor node which harvests energy necessary for information transmission from the environment. Aiming to minimize the loss of customers due to their impatience (and maximize the throughput of the system), a new strategy of control by providing service is proposed. This strategy suggests that service temporarily stops if the number of customers or units of energy in the system becomes zero. The server is switched off (is in sleep mode) for some time. This time finishes (the server wakes up) if both the number of customers in the buffer and the number of energy units reach some fixed threshold values or when the number of energy units reaches some threshold value and there are customers in the buffer. Arrival flows of customers and energy units are assumed to be described by an independent Markovian arrival process. The service time has a phase-type distribution. The system behavior is described by a multi-dimensional Markov chain. The generator of this Markov chain is derived. The ergodicity condition is presented. Expressions for key performance measures are given. Numerical results illustrating the dependence of a customer’s loss probability on the thresholds defining the discipline of waking up the server are provided. The importance of the account of correlation in arrival processes is numerically illustrated.

2

CO Oxidation Properties Of Selective Dissoluted Metallic Glass Composites

Kim S. Y., Lee M. H., Kim T. S., Kim B. S.

Archives of Metallurgy and Materials

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2015

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Vol. 60, iss. 2B

1227--1229

EN

Porous metallic materials have been widely used in many fields including aerospace, atomic energy, electro chemistry and environmental protection. Their unique structures make them very useful as lightweight structural materials, fluid filters, porous electrodes and catalyst supports. In this study, we fabricated Ni-based porous metallic glasses having uniformly dispersed micro meter pores by the sequential processes of ball-milling and chemical dissolution method. We investigated the application of our porous metal supported for Pt catalyst. The oxidation test was performed in an atmosphere of 1% CO and 3% O2. Microstructure observation was performed by using a scanning electron microscope. Oxidation properties and BET (Brunauer, Emmett, and Teller) were analyzed to understand porous structure developments. The results indicated that CO Oxidation reaction was dependent on the specific surface area.

3

Mobile Commerce System Integrated with Augmented Reality and Interactive Multimedia

Liu S. F., Lee M. H.

Przegląd Elektrotechniczny

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2012

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R. 88, nr 9b

100-103

EN

This study takes mobile devices as platforms, developing a mobile commerce display system of integrated augmented reality (AR) and interactive multimedia. Through AR technology, virtual products are added to real life of users. The experiment constructed two operation procedures of mobile commerce systems, General type and AR type respectively, as experiment samples which is only different in AR application. After operating the systems, a questionnaire is given to participants.

PL

Przedstawiono eksperyment dwóch mobilnych sieci sprzedaży wykorzystujących technologię AR (augmented reality).