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1
Content available Modelling customers’ impatience with discouraged arrival and retention of reneging
Medhi Pallabi
Operations Research and Decisions
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2021
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Vol. 31, No. 3
67--88
EN
The paper presents stochastic modelling of a single server, finite buffer Markovian queueing system with discouraged arrivals, baulking, reneging, and retention of reneged customers. The Markov process is used to derive the steady-state solution of the model. Closed-form expressions using probability generating functions (PGFs) are derived and presented for both classical and novel performance measures. In addition, a sensitivity analysis is carried out to study the effect of the system parameters on performance measures. A numerical problem is also presented to demonstrate the derived results and some design aspects.
2
Content available remote Algorytm optymalizacji kolejności operacji w ramach modułowej linii produkcyjnej
Pietrowiak A., Ciszak O., Wiśniewski M., Peta K., Suszyński M.
Technologia i Automatyzacja Montażu
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2015
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nr 3
13--17
PL
W pracy poruszono zagadnienie wyboru najkorzystniejszej kolejności rozpoczynania operacji w środowisku modułowego Elastycznego Systemu Produkcyjnego (ESP). Przybliżono budowę i zasadę działania ESP, w którym zastosowano liczne elementy zwiększające łatwość jego adaptacji do różnych zadań, jak np. roboty przemysłowe, obrabiarki CNC lub czytniki RFID. Szczegółowo opisano zasadę działania algorytmu optymalizacji wraz z założeniami, jakie przyjęto przed rozpoczęciem jego konstruowania. Algorytm został wstępnie przetestowany w środowisku zewnętrznym, a następnie dostosowany i zaimplementowany w środowisku sterownika PLC S7-300, a jego obsługa możliwa jest dzięki wizualizacji za pomocą odpowiedniej maski na panelu HMI. Zbadano również wpływ obsługi algorytmu na spowolnienie pracy sterownika w czasie rzeczywistym.
EN
This paper deals with the selection of the optimal sequence of setting up operations in an environment Flexible Manufacturing System (ESP). Brought closer to the construction and operation of the ESP, which uses a number of features to increase ease of adaptation to different tasks like Industrial robots, CNC or RFID readers. Describes in detail the principle of the optimization algorithm, together with the assumptions that were adopted before the start of the construct. The algorithm was initially tested in the external environment, and then adapted and implemented in an PLC S7-300, and its operation is made possible by visualization using a suitable mask on the HMI. Also examined the impact of use of the algorithm to slow the operation of the controller in real time.
3
Content available remote Dynamic provisioning and resource management for multi-tier cloud based applications
Goswami V, Patra S S, Mund G B
Foundations of Computing and Decision Sciences
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2013
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Vol. 38, No. 3
175--191
EN
Dynamic capacity provisioning is a useful technique for handling the workload variations seen in cloud environment. In this paper, we propose a dynamic provisioning technique for multi-tier applications to allocate resources efficiently using queuing model. It dynamically increases the mean service rate of the virtual machines to avoid congestion in the multi-tier environments. An optimization model to minimize the total number of virtual machines for computing resources in each tier has been presented. Using the supplementary variable and the recursive techniques, we obtain the system-length distributions at pre-arrival and arbitrary epochs. Some important performance indicators such as blocking probability, request waiting time and number of tasks in the system and in the queue have also been investigated. Finally, computational results showing the effect of model parameters on key performance indicators are presented.
4
Content available Classical and non-classical processor sharing systems with non-homogeneous customers
Tikhonenko O.
Scientific Issues of Jan Długosz University in Częstochowa. Mathematics
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2009
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Vol. 14
133-150
EN
We discuss a processor sharing system with non-homogeneous customers. There are resources of two types for their service: 1) resource of the first type is discrete, there are N units (servers) of the resource; 2) resource of the second type (capacity) is not-necessary discrete. The type of a customer is defined by the amount of first type resource units which is used for the customer service. Each customer is also characterized by some random capacity or some amount of the second type resource which is also used for his service. The total capacity of customers present in the system is limited by some value V >0, which is called the memory volume of the system. The customer capacity and length (the work necessary for service) are generally dependent. The joint distribution of these random variables also depends on the customer type. For such systems we determine the stationary distribution of the number of customers of each type present in the system and stationary loss probabilities for each type of customers.
5
Content available remote Estimations of loss characterisics of single-server queueing systems with non-homogeneous customers
Tikhonenko O., Gola A., Ziółkowski M.
Scientific Issues of Jan Długosz University in Częstochowa. Mathematics
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2008
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Vol. 13
53-66
EN
A non-classical single-server queueing system with non-homogeneous customers having some random space requirement (capacity, volume) can be used as a model of a wide class of computer and communicating systems. We assume that the total customers capacity in the systems is limited by some constant value V > O that is called the value of memory capacity of the system. Service time of a customer generally depends on his capacity. For such systems we determine some estimators of stationary loss characteristics and compare the analitical results with ones obtained by simulation.
6
Content available remote Markov mesoscopic simulation model of overftow queues at multilane signalised intersections
Viti F., van Zuylen H. J.
Archives of Transport
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2008
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Vol. 20, iss. 1-2
133-146
EN
Lane flow distribution is one of the factors affecting the capacity of a road section operated by a traffic signal. It is common in practice to assume this distribution independent on the traffic conditions. This paper analyses the interdependency between the dynamics of queues at isolated signalised intersections and the lane-changing behaviour of vehicles. A queuing model, based on Markov Chain renewal theory, is combined with a lane-changing behaviour model in order to simulate the lane flow distribution in time. We applied this model to a two-lane intersection approach, showing how the dynamics of queues influence the lane changing behaviour of travellers at different congestion levels. Finally, we study the case including an exclusive turning lane, showing the effects of spilIbacks.
PL
Jednym z czynników wpływających na przepustowość (pojemność) fragmentu sieci drogowej z sygnalizacją świetlną jest rozkład przepływów na poszczególnych pasach ruchu. Często zakłada się, że rozkład ten jest niezależny od natężenia ruchu. Autorzy artykułu analizują zależności pomiędzy dynamiką kolejek na izolowanych skrzyżowaniach z sygnalizacją świetlną a wzorcami zachowań kierowców dotyczących zmian pasów ruchu. Autorzy wykorzystują kombinację modelu kolejkowego opartego na teorii łańcuchów Markowa i modelu zmian pasów ruchu w celu symulacji rozkładu przepływów w czasie na poszczególnych pasach ruchu. Zaproponowany model został zastosowany do skrzyżowania z dwoma pasami ruchu, pokazując, w jaki sposób dynamika kolejek wpływa na wzorce zachowania kierowców przy różnym natężeniu ruchu. Ponadto, przeanalizowany został przypadek pasa ruchu wydzielonego dla skrętu, na którym zademonstrowano efekt fal zwrotnych.
7
Content available remote General approach to determining the basic characteristics of queueing systems with finite total capacity
Tikhonenko O.
Scientific Issues of Jan Długosz University in Częstochowa. Mathematics
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2007
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Vol. 12
107-114
EN
We discuss a general view of solutions for characteristics of non-classical queueing systems with random capacity customers (demands), i.e. we suppose that each customer is characterized by some random capacity (volume) and the whole capacity (total volume) of customers present in the queueing system is bounded by a constant value V > 0. We determine the general view of the stationary number distribution and loss probability in the systems under consideration as compared with corresponding classical queueing systems. It's turned that in some cases we can write expressions for non-classical characteristics of finite total capacity queues if corresponding classical characteristics are known.
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