Wyniki wyszukiwania - BazTech

1

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

|

2016

|

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

Analysis of an MMAP/PH1, PH2/N/∞ queueing system operating in a random environment

Kim C., Dudin A., Dudin S., Dudina O.

International Journal of Applied Mathematics and Computer Science

|

2014

|

Vol. 24, no. 3

485--501

EN

A multi-server queueing system with two types of customers and an infinite buffer operating in a random environment as a model of a contact center is investigated. The arrival flow of customers is described by a marked Markovian arrival process. Type 1 customers have a non-preemptive priority over type 2 customers and can leave the buffer due to a lack of service. The service times of different type customers have a phase-type distribution with different parameters. To facilitate the investigation of the system we use a generalized phase-type service time distribution. The criterion of ergodicity for a multi-dimensional Markov chain describing the behavior of the system and the algorithm for computation of its steady-state distribution are outlined. Some key performance measures are calculated. The Laplace–Stieltjes transforms of the sojourn and waiting time distributions of priority and non-priority customers are derived. A numerical example illustrating the importance of taking into account the correlation in the arrival process is presented.

3

ICP enhanced reactive magnetron sputtering system for synthesis of alumina coatings

Walkowicz J., Zykov A., Dudin S., Yakovin S., Brudnias R.

Tribologia

|

2006

|

nr 6

163-174

EN

The investigation results of the DC magnetron sputtering system for synthesis of high-quality aluminum oxide coatings are presented. In the system oxygen, activated by an independent Inductively-Coupled Plasma (ICP) source, was introduced into an aluminum sputtering chamber as an alternative to conventional reactive sputtering techniques employing the injection of ground state molecular oxygen O2. Behaviour of deposition process characteristics were investigated with and without the activation of the reactive species.

PL

W artykule przedstawione są wyniki badań stałoprądowego magnetronowego układu rozpylającego do osadzania powłok tlenku aluminium. W prezentowanym układzie, w odróżnieniu od standardowych magnetronowych układów osadzania wykorzystujących tlen cząsteczkowy w podstawowym stanie energetycznym, do komory procesowej dostarczany był tlen wzbudzany do wyższych poziomów energetycznych w niezależnym źródle z indukcyjnym wyładowaniem RF. Zbadane zostały zmiany charakterystyk procesu osadzania, ze wzbudzaniem i bez wzbudzania składników reaktywnych.