Numerical Analysis of Finite Source Markov Retrial System with Non-Reliable Server, Collision, and Impatient Customers

A retrial queuing system with a single server is investigated in this paper. The server is subject to random breakdowns. The number of customers is finite and collision may take place. A collision occurs when a customer arrives to the busy server. In case of a collision both customers involved in the collision are sent back to the orbit. From the orbit the customers retry their requests after a random waiting time. The server can be down due to a failure. During the failed period the arriving customers are sent to the orbit, as well. The novelty of this analysis is the impatient behaviour of the customers. A customer waiting in the orbit may leave it after a random waiting time. The requests of these customers will not be served. All the random variables included in the model construction are assumed to be exponentially distributed and independent from each other. The impatient property makes the model more complex, so the derivation of a direct algorithmic solution (which was provided for the non-impatient case) is difficult. For numerical calculations the MOSEL-2 tool can be used. This tool solves the Kolmogorov system equations, and from the resulting steady-state probabilities various system characteristics and performance measures can be calculated, i.e. mean response time, mean waiting time in the orbit, utilization of the server, probability of the unserved impatient requests. Principally the effect of the impatient property is investigated in these results, which are presented graphically, as well

A contribution to scheduling jobs submitted by finite-sources in computational clusters

Data science and data processing are very popular topics nowadays. Un- like a few years ago, everything is connected to data now and we have to handle these kinds of large data well. Therefore the distributed heterogeneous resources of networks e.g. the computational grid, have attracted great interest. It has become a challenge to schedule jobs in order to utilize the available resources effectively. The allocation of arriving jobs has a great impact on the efficiency and the energy consumption of the system. A generalized finite source model is presented in this paper. Our main goal is to build up models for the performance evaluation of scheduling computeintensive jobs with unknown service times in a computational cluster that consists of servers of different types. For this purpose we determine various performance measures for all combinations of three scheduling policies (two of them are the novelty of this paper: the MRT and the MRTHP policies) which can be used for assigning jobs to servers with three schemes for buffering arriving jobs. Furthermore, we investigate the effect of switching off idle servers on the energy consumption of the system under these combinations of scheduling policies and buffering schemes. Computational results obtained by simulation show that the choice of the scheduling policy and the buffering scheme plays an important role in ensuring the quality of service parameters such as the waiting time and the response time experienced in the case of arriving jobs. However, the energy consumption is only affected by the scheduling policy and the energy saving mode, while the buffering scheme does not have a significant impact

A contribution to scheduling jobs submitted by finite-sources in computational clusters

Data science and data processing are very popular topics nowadays. Un- like a few years ago, everything is connected to data now and we have to handle these kinds of large data well. Therefore the distributed heterogeneous resources of networks e.g. the computational grid, have attracted great interest. It has become a challenge to schedule jobs in order to utilize the available resources effectively. The allocation of arriving jobs has a great impact on the efficiency and the energy consumption of the system. A generalized finite source model is presented in this paper. Our main goal is to build up models for the performance evaluation of scheduling computeintensive jobs with unknown service times in a computational cluster that consists of servers of different types. For this purpose we determine various performance measures for all combinations of three scheduling policies (two of them are the novelty of this paper: the MRT and the MRTHP policies) which can be used for assigning jobs to servers with three schemes for buffering arriving jobs. Furthermore, we investigate the effect of switching off idle servers on the energy consumption of the system under these combinations of scheduling policies and buffering schemes. Computational results obtained by simulation show that the choice of the scheduling policy and the buffering scheme plays an important role in ensuring the quality of service parameters such as the waiting time and the response time experienced in the case of arriving jobs. However, the energy consumption is only affected by the scheduling policy and the energy saving mode, while the buffering scheme does not have a significant impact

In vitro comparative study of two Arundo donax L. ecotypes' selenium tolerance

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Numerical analysis of finite source Markov retrial system with non-reliable server, collision, and impatient customers

A retrial queuing system with a single server is investigated in this pa- per. The server is subject to random breakdowns. The number of customers is finite and collision may take place. A collision occurs when a customer arrives to the busy server. In case of a collision both customers involved in the collision are sent back to the orbit. From the orbit the customers retry their requests after a random waiting time. The server can be down due to a failure. During the failed period the arriving customers are sent to the orbit, as well. The novelty of this analysis is the impatient behaviour of the customers. A customer waiting in the orbit may leave it after a random waiting time. The requests of these customers will not be served. All the random variables included in the model construction are assumed to be exponentially distributed and independent from each other. The impatient property makes the model more complex, so the derivation of a direct algorithmic solution (which was provided for the non-impatient case) is difficult. For numerical calculations the MOSEL-2 tool can be used. This tool solves the Kolmogorov system equations, and from the resulting steady-state probabilities various system characteristics and performance measures can be calculated, i.e. mean response time, mean waiting time in the orbit, utilization of the server, probability of the unserved impatient requests. Principally the effect of the impatient property is investigated in these results, which are presented graphically, as well

Performance Modeling of Finite-Source Cognitive Radio Networks

This paper deals with performance modeling aspects of radio frequency licensing. The utilization of mobile cellular networks can be increased by the idea of the cognitive radio. Licensed users (Primary Users - PUs) and normál users (Secondary Users - SUs) are considered. The main idea is, that the SUs are able to access to the available non-licensed radio frequencies. A finite-source retrial queueing model with two non independent frequency bands (considered as service units) is proposed for the performance evaluation of the system. A service unit with a priority queue and another service unit with an orbit are assigned to the PUs and SUs, respectively. The users are classified into two classes: the PUs have got a licensed frequency, while the SUs have got a frequency band, too but it suffers from the overloading. We assume that during the service of the non-overloaded band the PUs have preemptive priority over SUs. The involved inter-event times are supposed to be independent and exponentially distributed random variables. The novelty of this work lies in the fact that we consider the effect of retrial phenomenon of SUs in performance modeling of radio frequency licensing by using a finite-source queueing model which takes the unreliability of radio transmission into account for the first time. In the literature, most work studied the performance of cognitive radio networks under a mixed spectrum environment of licensed and unlicensed bands where the blocked SUs and the preempted SUs are forced to leave the system forever when there are no idle channels in the system. But in practical situation, the blocked SUs and the preempted SUs may do not leave the system forever and try to continue their services after random amount of time. By the help of an appropriate continuous time Markov chain using MOSEL (MOdeling Specification and Evaluation Language) tool several numerical examples are provided showing the effects of different input parameters on the main performance measures of the cognitive radio networks. Our primary focus is to determine an optimal number of SUs, where at the secondary band the gained utilization, that is when switching to the cognitive radio, has a maximum value

A nanoszelén kiegészítés hatása a vörös árnyékhal (Sciaenops ocellatus) termelési paramétereire és nyomelem felvételére

The selenium is an essential trace element with antioxidant effect, constituent of many enzymes, natural component of the body of the animals. The addition to the fish feed as micro element supplementation is generally accepted. Numerous animal experiments veryfied, that the antioxidant effect of the nanoselenium is higher than other selenium forms. But no much information is available of the usuage at fish. In the experiment were investigated the effects of the nanoselenium supplementation of a commercial fish feed were investigated to the production parameters and the body tissue composition. The correlation between the accumulated selenium content of the body and the treatment, and the feed conversation was also statistically analyzed beside the production parameters. Furthermore we were curious, if can be toxic the nanoselenium in higher doses. The experimental stock was placed into 12 plastic tanks (each 70 l water vol.) in a recirculation system for larval rearing. The salinity and the water temperature was constant during the 8 week long experiment. The feeding was ad libitum, 4 times a day. Beside the control five (1, 1.5, 2.5, 5.5, 10.5 mg Se kg-1) duplicated treatment were set. According to the results, from the production parameters only at the value of FCR and the survival was found significant difference (p<0.05) between the groups. However strong correlation (r=0.752–0.780, p<0.01) was determined between the treatment and the accumulated selenium levels. To analyzed the free fatty acid contentof the fish, we realized, that the selenium uptake significanly enhanced this level at all treatments. The greatest change was found in case of the type n-3 fatty acids. Established by the results, the higher intake than 0.5 mg Se kg-1 was not changed significantly the production parameters, nevertheless to increase the selenium content of commercial feeds to 1.5 mg Se kg-1 could be rewarding on the rearing of red drum

Ecotoxicology of Copper in Horticultural Soils: a Review

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Production of nano-size elemental selenium particles and its investigation in the soil-plant-animal system

Kidolgoztam a szelenittel dúsított MRS tápközegben inkubált Lactobacillus casei tejsavbaktérium által előállított, 250 nm átmérőjű vörös elemi szeléngömbök kinyerését és tisztítását, illetve a laboratóriumi célokra felhasználható NanoSel szol előállítását. A nanoméretű elemiszelén-részecskék vizes közegben való viselkedését vizsgálva felállítottam egy modellt, mely bemutatja az elemi szelén szelenitté és szeleniddé való feltételezett átalakulását, amely az elemi szelén felé erősen eltolt, igen hosszú idő alatt beálló egyensúlyi folyamat. Megvizsgáltam továbbá a nanoszelén viselkedését a talaj-növény-állat rendszerben.We developed a method to produce a purified sol for experimental use, called NanoSel, which contains 250 nm sized red elemental selenium nanospheres produced by fermentation with Lactobacillus casei in selenite enriched MRS broth. Investigating the separated nano-sized elemental selenium particles in aqueous media we constructed a model that demonstrates the disproportionation of elemental selenium to selenite and hydrogen-selenide, a slow equilibratory conversion process skewed toward the elemental form. We also examined the behaviour of the nano-sized elemental selenium particles in soil, plant and animal experiments.d