#### Sample records for time queueing theoretic

1. Applied discrete-time queues

CERN Document Server

Alfa, Attahiru S

2016-01-01

This book introduces the theoretical fundamentals for modeling queues in discrete-time, and the basic procedures for developing queuing models in discrete-time. There is a focus on applications in modern telecommunication systems. It presents how most queueing models in discrete-time can be set up as discrete-time Markov chains. Techniques such as matrix-analytic methods (MAM) that can used to analyze the resulting Markov chains are included. This book covers single node systems, tandem system and queueing networks. It shows how queues with time-varying parameters can be analyzed, and illustrates numerical issues associated with computations for the discrete-time queueing systems. Optimal control of queues is also covered. Applied Discrete-Time Queues targets researchers, advanced-level students and analysts in the field of telecommunication networks. It is suitable as a reference book and can also be used as a secondary text book in computer engineering and computer science. Examples and exercises are includ...

2. Equilibrium Arrival Times to Queues

DEFF Research Database (Denmark)

Breinbjerg, Jesper; Østerdal, Lars Peter

We consider a non-cooperative queueing environment where a finite number of customers independently choose when to arrive at a queueing system that opens at a given point in time and serves customers on a last-come first-serve preemptive-resume (LCFS-PR) basis. Each customer has a service time...... requirement which is identically and independently distributed according to some general probability distribution, and they want to complete service as early as possible while minimizing the time spent in the queue. In this setting, we establish the existence of an arrival time strategy that constitutes...... a symmetric (mixed) Nash equilibrium, and show that there is at most one symmetric equilibrium. We provide a numerical method to compute this equilibrium and demonstrate by a numerical example that the social effciency can be lower than the effciency induced by a similar queueing system that serves customers...

3. The MX/G/1 queue with queue length dependent service times

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Bong Dae Choi

2001-01-01

Full Text Available We deal with the MX/G/1 queue where service times depend on the queue length at the service initiation. By using Markov renewal theory, we derive the queue length distribution at departure epochs. We also obtain the transient queue length distribution at time t and its limiting distribution and the virtual waiting time distribution. The numerical results for transient mean queue length and queue length distributions are given.

4. Influence of queue propagation and dissipation on route travel times

DEFF Research Database (Denmark)

Raovic, Nevena

into account (Bliemer, 2008). Yperman (2007) indicates that there is a significant difference in queue-propagation and queue-dissipation between the LTM and DQM. This results in different route travel times, and can further affect route choice. In this paper, different approaches to represent queue propagation...... and dissipation through the CTM, LTM and DQM are studied. A simple network allows to show how these approaches influence route travel time. Furthermore, the possibility of changing the existing DQM is considered in order to more realistically represent queue propagation and dissipation, which would lead to more...... accurate route travel times....

5. Queues with waiting time dependent service

DEFF Research Database (Denmark)

Bekker, R.; Koole, G. M.; Nielsen, Bo Friis

2011-01-01

Motivated by service levels in terms of the waiting-time distribution seen, for instance, in call centers, we consider two models for systems with a service discipline that depends on the waiting time. The first model deals with a single server that continuously adapts its service rate based...... derive steady-state waiting-time distributions for both models. The results are illustrated with numerical examples....... on the waiting time of the first customer in line. In the second model, one queue is served by a primary server which is supplemented by a secondary server when the waiting of the first customer in line exceeds a threshold. Using level crossings for the waiting-time process of the first customer in line, we...

6. On response time and cycle time distributions in a two-stage cyclic queue

NARCIS (Netherlands)

Boxma, O.J.; Donk, P.

1982-01-01

We consider a two-stage closed cyclic queueing model. For the case of an exponential server at each queue we derive the joint distribution of the successive response times of a custumer at both queues, using a reversibility argument. This joint distribution turns out to have a product form. The

7. The Remaining Service Time Upon Reaching a High Level in M/G/1 Queues

NARCIS (Netherlands)

de Boer, Pieter-Tjerk; Nicola, V.F.; van Ommeren, Jan C.W.

The distribution of the remaining service time upon reaching some target level in an M/G/1 queue is of theoretical as well as practical interest. In general, this distribution depends on the initial level as well as on the target level, say, B. Two initial levels are of particular interest, namely,

8. Waiting time distribution in M/D/1 queueing systems

DEFF Research Database (Denmark)

Iversen, Villy Bæk; Staalhagen, Lars

1999-01-01

The well-known formula for the waiting time distribution of M/D/1 queueing systems is numerically unsuitable when the load is close to 1.0 and/or the results for a large waiting time are required. An algorithm for any load and waiting time is presented, based on the state probabilities of M/D/1...

9. Sojourn-time approximations in queueing networks with feedback

NARCIS (Netherlands)

Gijsen, B.M.M.; van der Mei, R.D.; Engelberts, P.; van den Berg, J.L.; van Wingerden, K.M.C.

2006-01-01

This paper is motivated by the response-time analysis of distributed information systems, where transactions are handled by a sequence of front-end server and back-end server actions. We study sojourn times in an open queueing network with a single Processor Sharing (PS) node and an arbitrary number

10. Sojourn time approximations in queueing networks with feedback

NARCIS (Netherlands)

Gijsen, B.M.M.; Mei, R.D. van der; Engelberts, P.; Berg, J.L. van den; Wingerden, K.M.C. van

2006-01-01

This paper is motivated by the response-time analysis of distributed information systems, where transactions are handled by a sequence of front-end server and back-end server actions. We study sojourn times in an open queueing network with a single Processor Sharing (PS) node and an arbitrary number

11. Sojourn-time approximations in queueing networks with feedback

NARCIS (Netherlands)

Gijsen, B.M.M.; van der Mei, R.D.; van den Berg, Hans Leo; van Wingerden, K.M.C.

This paper is motivated by the response-time analysis of distributed information systems, where transactions are handled by a sequence of front-end server and back-end server actions. We study sojourn times in an open queueing network with a single Processor Sharing (PS) node and an arbitrary number

12. Sojourn time asymptotics in processor-sharing queues

NARCIS (Netherlands)

Borst, S.C.; Núñez Queija, R.; Zwart, B.

2006-01-01

Over the past few decades, the Processor-Sharing (PS) discipline has attracted a great deal of attention in the queueing literature. While the PS paradigm emerged in the sixties as an idealization of round-robin scheduling in time-shared computer systems, it has recently captured renewed interest as

13. Queueing theoretic analysis of labor and delivery : Understanding management styles and C-section rates.

Science.gov (United States)

Gombolay, Matthew; Golen, Toni; Shah, Neel; Shah, Julie

2017-09-04

Childbirth is a complex clinical service requiring the coordinated support of highly trained healthcare professionals as well as management of a finite set of critical resources (such as staff and beds) to provide safe care. The mode of delivery (vaginal delivery or cesarean section) has a significant effect on labor and delivery resource needs. Further, resource management decisions may impact the amount of time a physician or nurse is able to spend with any given patient. In this work, we employ queueing theory to model one year of transactional patient information at a tertiary care center in Boston, Massachusetts. First, we observe that the M/G/∞ model effectively predicts patient flow in an obstetrics department. This model captures the dynamics of labor and delivery where patients arrive randomly during the day, the duration of their stay is based on their individual acuity, and their labor progresses at some rate irrespective of whether they are given a bed. Second, using our queueing theoretic model, we show that reducing the rate of cesarean section - a current quality improvement goal in American obstetrics - may have important consequences with regard to the resource needs of a hospital. We also estimate the potential financial impact of these resource needs from the hospital perspective. Third, we report that application of our model to an analysis of potential patient coverage strategies supports the adoption of team-based care, in which attending physicians share responsibilities for patients.

14. Sojourn time tails in the single server queue with heavy-tailed service times

NARCIS (Netherlands)

Boxma, O.J.; Denisov, D.E.

2009-01-01

We consider the GI/GI/1 queue with regularly varying service requirement distribution of index -a. It is well known that, in the M/G/1 FCFS queue, the sojourn time distribution is also regularly varying, of index 1 - a, whereas in the case of LCFS or Processor Sharing, the sojourn time distribution

15. Sojourn time tails in the single server queue with heavy-tailed service times

NARCIS (Netherlands)

Boxma, O.J.; Denisov, D.E.

2011-01-01

We consider the GI/GI/1 queue with regularly varying service requirement distribution of index -a. It is well known that, in the M/G/1 FCFS queue, the sojourn time distribution is also regularly varying, of index 1-a, whereas in the case of LCFS or Processor Sharing, the sojourn time distribution is

16. Single server queueing networks with varying service times and renewal input

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Pierre Le Gall

2000-01-01

Full Text Available Using recent results in tandem queues and queueing networks with renewal input, when successive service times of the same customer are varying (and when the busy periods are frequently not broken up in large networks, the local queueing delay of a single server queueing network is evaluated utilizing new concepts of virtual and actual delays (respectively. It appears that because of an important property, due to the underlying tandem queue effect, the usual queueing standards (related to long queues cannot protect against significant overloads in the buffers due to some possible agglutination phenomenon (related to short queues. Usual network management methods and traffic simulation methods should be revised, and should monitor the partial traffic streams loads (and not only the server load.

17. A queueing system with queue length dependent service times, with applications to cell discarding in ATM networks

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Doo Il Choi

1999-01-01

Full Text Available A queueing system (M/G1,G2/1/K is considered in which the service time of a customer entering service depends on whether the queue length, N(t, is above or below a threshold L. The arrival process is Poisson, and the general service times S1 and S2 depend on whether the queue length at the time service is initiated is time of the customer currently in service. Exact solutions for the stationary probabilities are constructed for both infinite and finite capacity systems. Asymptotic approximations of the solutions are given, which yield simple formulas for performance measures such as loss rates and tail probabilities. The numerical accuracy of the asymptotic results is tested.

18. A Parallel Priority Queue with Constant Time Operations

DEFF Research Database (Denmark)

Brodal, Gerth Stølting; Träff, Jesper Larsson; Zaroliagis, Christos D.

1998-01-01

We present a parallel priority queue that supports the following operations in constant time:parallel insertionof a sequence of elements ordered according to key,parallel decrease keyfor a sequence of elements ordered according to key,deletion of the minimum key element, anddeletion of an arbitrary...... application is a parallel implementation of Dijkstra's algorithm for the single-source shortest path problem, which runs inO(n) time andO(mlogn) work on a CREW PRAM on graphs withnvertices andmedges. This is a logarithmic factor improvement in the running time compared with previous approaches....

19. Maintenance in Single-Server Queues: A Game-Theoretic Approach

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Najeeb Al-Matar

2009-01-01

examine a single-server queue with bulk input and secondary work during server's multiple vacations. When the buffer contents become exhausted the server leaves the system to perform some diagnostic service of a minimum of L jobs clustered in packets of random sizes (event A. The server is not supposed to stay longer than T units of time (event B. The server returns to the system when A or B occurs, whichever comes first. On the other hand, he may not break service of a packet in a middle even if A or B occurs. Furthermore, the server waits for batches of customers to arrive if upon his return the queue is still empty. We obtain a compact and explicit form functional for the queueing process in equilibrium.

20. Joint distribution of sojourn time and queue length in the M/G/1 queue with (in)finite capacity

NARCIS (Netherlands)

Boxma, O.J.

1984-01-01

For the M/G/1 queue we study the joint distribution of the number of customers x present immediately before an arrival epoch and of the residual service time ¿ of the customer in service at this epoch. The correlation coefficient (x, ¿) is shown to be positive (negative) when the service time

1. Time Is Not on Our Side: How Radiology Practices Should Manage Customer Queues.

Science.gov (United States)

Loving, Vilert A; Ellis, Richard L; Rippee, Robert; Steele, Joseph R; Schomer, Donald F; Shoemaker, Stowe

2017-11-01

2. Waiting-time approximations in multi-queue systems with cyclic service

NARCIS (Netherlands)

Boxma, O.J.; Meister, B.W.

1987-01-01

This study is devoted to mean waiting-time approximations in a single-server multi-queue model with cyclic service and zero switching times of the server between consecutive queues. Two different service disciplines are considered: exhaustive service and (ordinary cyclic) nonexhaustive service. For

3. Application of queueing models to multiprogrammed computer systems operating in a time-critical environment

Science.gov (United States)

Eckhardt, D. E., Jr.

1979-01-01

A model of a central processor (CPU) which services background applications in the presence of time critical activity is presented. The CPU is viewed as an M/M/1 queueing system subject to periodic interrupts by deterministic, time critical process. The Laplace transform of the distribution of service times for the background applications is developed. The use of state of the art queueing models for studying the background processing capability of time critical computer systems is discussed and the results of a model validation study which support this application of queueing models are presented.

4. Equilibrium arrival times to queues with general service times and non-linear utility functions

DEFF Research Database (Denmark)

Breinbjerg, Jesper

2017-01-01

by a general utility function which is decreasing in the waiting time and service completion time of each customer. Applications of such queueing games range from people choosing when to arrive at a grand opening sale to travellers choosing when to line up at the gate when boarding an airplane. We develop...

5. Sojourn time distributions in a Markovian G-queue with batch arrival and batch removal

Directory of Open Access Journals (Sweden)

Yang Woo Shin

1999-01-01

Full Text Available We consider a single server Markovian queue with two types of customers; positive and negative, where positive customers arrive in batches and arrivals of negative customers remove positive customers in batches. Only positive customers form a queue and negative customers just reduce the system congestion by removing positive ones upon their arrivals. We derive the LSTs of sojourn time distributions for a single server Markovian queue with positive customers and negative customers by using the first passage time arguments for Markov chains.

6. Sojourn times in the M/G/1 FB queue with light-tailed service times

NARCIS (Netherlands)

M.R.H. Mandjes (Michel); M. Nuyens

2004-01-01

textabstractThe asymptotic decay rate of the sojourn time of a customer in the stationary M/G/1 queue under the Foreground-Background (FB) service discipline is studied. The FB discipline gives service to those customers that have received the least service so far. We prove that for light-tailed

7. Sojourn times in the M/G/1 FB queue with light-tailed service times.

NARCIS (Netherlands)

Mandjes, M.R.H.; Nuijens, M.F.M.

2005-01-01

ABSTRACT The asymptotic decay rate of the sojourn time of a customer in the stationary M/G/1 queue under the Foreground-Background (FB) service discipline is studied. The FB discipline gives service to those customers that have received the least service so far. We prove that for lighttailed service

8. Asymptotic inference for waiting times and patiences in queues with abandonment

DEFF Research Database (Denmark)

Gorst-Rasmussen, Anders; Hansen, Martin Bøgsted

Motivated by applications in call center management, we propose a framework based on empirical process techniques for inference about the waiting time and patience distribution in multiserver queues with abandonment. The framework rigorises heuristics based on survival analysis of independent...

9. Asymptotic inference for waiting times and patiences in queues with abandonment

DEFF Research Database (Denmark)

Gorst-Rasmussen, Anders; Hansen, Martin Bøgsted

2009-01-01

Motivated by applications in call center management, we propose a framework based on empirical process techniques for inference about waiting time and patience distributions in multiserver queues with abandonment. The framework rigorises heuristics based on survival analysis of independent...

10. NPS and the methadone queue: Spillages of space and time.

Science.gov (United States)

Alexandrescu, Liviu

2017-02-01

Between 2008 and 2013, powder-stimulants sold by 'head shops' as novel psychoactive substances (NPS) or 'legal highs' have displaced heroin among groups of injecting substance users in Bucharest, Romania. Rising HIV-infection rates and other medical or social harms have been reported to follow this trend. The study builds on two sets of original (N=30) and existing (N=20) interview data and on observations collected mainly at the site of a methadone substitution treatment facility. By disentangling the space-time continuum of the methadone queue, this paper argues that injecting drug users' (IDUs) passage from opiates to amphetamine-type stimulants (ATS) can be understood as 'spillages' of space and time. IDUs thus 'spill' out of the disciplinary flows of methadone treatment in two ways. The first is that of space and materiality. Drawing on actor-network theory (ANT), ATS/NPS appear embedded in reconfigured practices and rituals of injecting use. Such spillages see the pleasure-seeking self being fluidised in forming connections with, or spilling into, nonhuman actants such as substances, settings or objects. The second dimension of spilling is that of time. In this sense, heroin use is a 'cryogenic strategy' of inhabiting history and facing the transition to the market society that Romanian opiate injectors spill out of, not able to appropriate choice and legitimate consumption. The phenomenological qualities of stimulants that seem to accelerate lived time and generalise desire thus present them with an opportunity to alleviate a form of what a post-communist moral imaginary of transition frames as debilitating nostalgia. ATS/NPS are revealed as fluid entities that do not only shape risk conditions but also alter shared meanings and contextual configurations of bodies, substances and disciplinary regimes in unpredictable ways. Copyright © 2016 Elsevier B.V. All rights reserved.

11. Mean time for the development of large workloads and large queue lengths in the GI/G/1 queue

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Charles Knessl

1996-01-01

Full Text Available We consider the GI/G/1 queue described by either the workload U(t (unfinished work or the number of customers N(t in the system. We compute the mean time until U(t reaches excess of the level K, and also the mean time until N(t reaches N0. For the M/G/1 and GI/M/1 models, we obtain exact contour integral representations for these mean first passage times. We then compute the mean times asymptotically, as K and N0→∞, by evaluating these contour integrals. For the general GI/G/1 model, we obtain asymptotic results by a singular perturbation analysis of the appropriate backward Kolmogorov equation(s. Numerical comparisons show that the asymptotic formulas are very accurate even for moderate values of K and N0.

12. A discrete-time queueing system with changes in the vacation times

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Atencia Ivan

2016-06-01

Full Text Available This paper considers a discrete-time queueing system in which an arriving customer can decide to follow a last come first served (LCFS service discipline or to become a negative customer that eliminates the one at service, if any. After service completion, the server can opt for a vacation time or it can remain on duty. Changes in the vacation times as well as their associated distribution are thoroughly studied. An extensive analysis of the system is carried out and, using a probability generating function approach, steady-state performance measures such as the first moments of the busy period of the queue content and of customers delay are obtained. Finally, some numerical examples to show the influence of the parameters on several performance characteristics are given.

13. Analysis of the asymmetric shortest queue problem : Part 1: theoretical analysis

NARCIS (Netherlands)

Adan, I.J.B.F.; Wessels, J.; Zijm, W.H.M.

1990-01-01

In this paper we study a system consisting of two parallel servers with different service rates. Jobs arrive according to a Poisson stream and generate an exponentially distributed workload. On arrival a job joins the shortest queue and in case both queues have equal lengths. be joins the first

14. Optimization of Signal Timing of Intersections by Internal Metering of Queue Time Ratio of Vehicles in Network Scale

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Mina Ghanbarikarekani

2016-06-01

Full Text Available Optimization of signal timing in urban network is usually done by minimizing the delay times or queue lengths. Sincethe effect of each intersection on the whole network is not considered in the mentioned methods, traffic congestion may occur in network links. Therefore, this paper has aimed to provide a timing optimization algorithm for traffic signals using internal timing policy based on balancing queue time ratio of vehicles in network links. In the proposed algorithm, the difference between the real queue time ratio and the optimum one for each link of intersection was minimized. To evaluate the efficiency of the proposed algorithm on traffic performance, the proposed algorithm was applied in a hypothetical network. By comparing the simulating software outputs, before and after implementing the algorithm, it was concluded that the queue time ratio algorithm has improved the traffic parameters by increasing the flow as well as reducing the delay time and density of the network.

15. A robust and high-performance queue management controller for large round trip time networks

Science.gov (United States)

2016-05-01

Congestion management for transmission control protocol is of utmost importance to prevent packet loss within a network. This necessitates strategies for active queue management. The most applied active queue management strategies have their inherent disadvantages which lead to suboptimal performance and even instability in the case of large round trip time and/or external disturbance. This paper presents an internal model control robust queue management scheme with two degrees of freedom in order to restrict the undesired effects of large and small round trip time and parameter variations in the queue management. Conventional approaches such as proportional integral and random early detection procedures lead to unstable behaviour due to large delay. Moreover, internal model control-Smith scheme suffers from large oscillations due to the large round trip time. On the other hand, other schemes such as internal model control-proportional integral and derivative show excessive sluggish performance for small round trip time values. To overcome these shortcomings, we introduce a system entailing two individual controllers for queue management and disturbance rejection, simultaneously. Simulation results based on Matlab/Simulink and also Network Simulator 2 (NS2) demonstrate the effectiveness of the procedure and verify the analytical approach.

16. A two-station queue with dependent preparation and service times

NARCIS (Netherlands)

Vlasiou, M.; Adan, I.J.B.F.; Boxma, O.J.

2009-01-01

We discuss a single-server multi-station alternating queue where the preparation times and the service times are auto- and cross-correlated. We examine two cases. In the first case, preparation and service times depend on a common discrete time Markov chain. In the second case, we assume that the

17. An MX/GI/1/N queue with close-down and vacation times

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Andreas Frey

1999-01-01

Full Text Available An MX/GI/1/N finite capacity queue with close-down time, vacation time and exhaustive service discipline is considered under the partial batch acceptance strategy as well as under the whole batch acceptance strategy. Applying the supplementary variable technique the queue length distribution at an arbitrary instant and at a departure epoch is obtained under both strategies, where no assumption on the batch size distribution is made. The loss probabilities and the Laplace-Stieltjes transforms of the waiting time distribution of the first customer and of an arbitrary customer of a batch are also given. Numerical examples give some insight into the behavior of the system.

18. Response times in a two-node queueing network with feedback

NARCIS (Netherlands)

van der Mei, R.D.; Gijsen, B.M.M.; in 't Veld, N.; van den Berg, J.L.

2002-01-01

The study presented in this paper is motivated by the performance analysis of response times in distributed information systems, where transactions are handled by iterative server and database actions. We model system response times as sojourn times in a two-node open queueing network with a

19. Response times in a two-node queueing network with feedback

NARCIS (Netherlands)

van der Mei, R.D.; Gijsen, B.M.M.; Gijsen, B.M.M.; in 't Veld, N.; van den Berg, Hans Leo

The study presented in this paper is motivated by the performance analysis of response times in distributed information systems, where transactions are handled by iterative server and database actions. We model system response times as sojourn times in a two-node open queueing network with a

20. The M/G/1 queue with heavy-tailed service time distribution

NARCIS (Netherlands)

Boxma, O.J.; Cohen, J.W.

1998-01-01

In modern teletraffic applications of queueing theory, service time distributions B(t) with a heavy tail occur, i.e., 1-B(t)~Ct-v for t¿8 with v>1. For such service time distributions, not much explicit information is available concerning the tail probabilities of the corresponding waiting time

1. A Novel Analytic Technique for the Service Station Reliability in a Discrete-Time Repairable Queue

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Renbin Liu

2013-01-01

Full Text Available This paper presents a decomposition technique for the service station reliability in a discrete-time repairable GeomX/G/1 queueing system, in which the server takes exhaustive service and multiple adaptive delayed vacation discipline. Using such a novel analytic technique, some important reliability indices and reliability relation equations of the service station are derived. Furthermore, the structures of the service station indices are also found. Finally, special cases and numerical examples validate the derived results and show that our analytic technique is applicable to reliability analysis of some complex discrete-time repairable bulk arrival queueing systems.

2. The M/M/1 queue with inventory, lost sale and general lead times

DEFF Research Database (Denmark)

Saffari, Mohammad; Asmussen, Søren; Haji, Rasoul

We consider an M/M/1 queueing system with inventory under the (r,Q) policy and with lost sales, in which demands occur according to a Poisson process and service times are exponentially distributed. All arriving customers during stockout are lost. We derive the stationary distributions of the joint...... queue length (number of customers in the system) and on-hand inventory when lead times are random variables and can take various distributions. The derived stationary distributions are used to formulate long-run average performance measures and cost functions in some numerical examples....

3. On the Discrete-Time GeoX/G/1 Queues under N-Policy with Single and Multiple Vacations

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Sung J. Kim

2013-01-01

Full Text Available We consider the discrete-time GeoX/G/1 queue under N-policy with single and multiple vacations. In this queueing system, the server takes multiple vacations and a single vacation whenever the system becomes empty and begins to serve customers only if the queue length is at least a predetermined threshold value N. Using the well-known property of stochastic decomposition, we derive the stationary queue-length distributions for both vacation models in a simple and unified manner. In addition, we derive their busy as well as idle-period distributions. Some classical vacation models are considered as special cases.

4. A bulk queueing system under N-policy with bilevel service delay discipline and start-up time

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David C. R. Muh

1993-01-01

Full Text Available The author studies the queueing process in a single-server, bulk arrival and batch service queueing system with a compound Poisson input, bilevel service delay discipline, start-up time, and a fixed accumulation level with control operating policy. It is assumed that when the queue length falls below a predefined level r(≥1, the system, with server capacity R, immediately stops service until the queue length reaches or exceeds the second predefined accumulation level N(≥r. Two cases, with N≤R and N≥R, are studied.

5. Group-Server Queues

OpenAIRE

Li, Quan-Lin; Ma, Jing-Yu; Xie, Mingzhou; Xia, Li

2017-01-01

By analyzing energy-efficient management of data centers, this paper proposes and develops a class of interesting {\\it Group-Server Queues}, and establishes two representative group-server queues through loss networks and impatient customers, respectively. Furthermore, such two group-server queues are given model descriptions and necessary interpretation. Also, simple mathematical discussion is provided, and simulations are made to study the expected queue lengths, the expected sojourn times ...

6. Sojourn time asymptotics in Processor Sharing queues with varying service rate

NARCIS (Netherlands)

Egorova, R.; Mandjes, M.R.H.; Zwart, B.

2007-01-01

Abstract This paper addresses the sojourn time asymptotics for a GI/GI/⋅ queue operating under the Processor Sharing (PS) discipline with stochastically varying service rate. Our focus is on the logarithmic estimates of the tail of sojourn-time distribution, under the assumption that the job-size

7. A numerical solution for the multi-server queue with hyper-exponential service times

NARCIS (Netherlands)

de Smit, J.H.A.

1983-01-01

In this paper we present a numerical method for the queue GI/H2/s, which is based on general results for GI/Hm/s. We give a complete description of the algorithm which yields exact results for the steady distributions of the actual waiting time, the virtual waiting time and the number of customers

8. Sojourn time asymptotics in the M/G/1 processor sharing queue

NARCIS (Netherlands)

A.P. Zwart (Bert); O.J. Boxma (Onno)

1998-01-01

textabstractWe show for the M/G/1 processor sharing queue that the service time distribution is regularly varying of index $-nu$, $nu$ non-integer, iff the sojourn time distribution is regularly varying of index $-nu$. This result is derived from a new expression for the Laplace-Stieltjes transform

9. Scaling and comparison of fluid limits of queues applied to call centers with time-varying parameters

NARCIS (Netherlands)

Jiménez, T.; Koole, G.M.

2004-01-01

Temporary overload situations in queues can be approximated by fluid queues. We strengthen earlier results on the comparison of multi-server tandem systems with their fluid limits. At the same time we give conditions under which economies of scale hold. We apply the results to call centers. ©

10. General bulk service queueing system with N-policy, multiplevacations, setup time and server breakdown without interruption

Science.gov (United States)

Sasikala, S.; Indhira, K.; Chandrasekaran, V. M.

2017-11-01

In this paper, we have considered an MX / (a,b) / 1 queueing system with server breakdown without interruption, multiple vacations, setup times and N-policy. After a batch of service, if the size of the queue is ξ (customers in the queue. After a vacation, if the server finds at least N customers waiting for service, then the server needs a setup time to start the service. After a batch of service, if the amount of waiting customers in the queue is ξ (≥ a) then the server serves a batch of min(ξ,b) customers, where b ≥ a. We derived the probability generating function of queue length at arbitrary time epoch. Further, we obtained some important performance measures.

11. An asymmetric shortest queue problem

NARCIS (Netherlands)

Adan, I.J.B.F.; Wessels, J.; Zijm, W.H.M.

1989-01-01

In this paper we study a system consisting of two identical servers, each with exponentially distributed service times. Jobs arrive according to a Poisson stream. On arrival a job joins the shortest queue and in case both queues have equal length. he joins queue 1 say with probability q and queue 2

12. A Discrete-Time Geo/G/1 Retrial Queue with Two Different Types of Vacations

Directory of Open Access Journals (Sweden)

Feng Zhang

2015-01-01

Full Text Available We analyze a discrete-time Geo/G/1 retrial queue with two different types of vacations and general retrial times. Two different types of vacation policies are investigated in this model, one of which is nonexhaustive urgent vacation during serving and the other is normal exhaustive vacation. For this model, we give the steady-state analysis for the considered queueing system. Firstly, we obtain the generating functions of the number of customers in our model. Then, we obtain the closed-form expressions of some performance measures and also give a stochastic decomposition result for the system size. Moreover, the relationship between this discrete-time model and the corresponding continuous-time model is also investigated. Finally, some numerical results are provided to illustrate the effect of nonexhaustive urgent vacation on some performance characteristics of the system.

13. A Discrete-Time Queue with Balking, Reneging, and Working Vacations

Directory of Open Access Journals (Sweden)

Veena Goswami

2014-01-01

Full Text Available This paper presents an analysis of balking and reneging in finite-buffer discrete-time single server queue with single and multiple working vacations. An arriving customer may balk with a probability or renege after joining according to a geometric distribution. The server works with different service rates rather than completely stopping the service during a vacation period. The service times during a busy period, vacation period, and vacation times are assumed to be geometrically distributed. We find the explicit expressions for the stationary state probabilities. Various system performance measures and a cost model to determine the optimal service rates are presented. Moreover, some queueing models presented in the literature are derived as special cases of our model. Finally, the influence of various parameters on the performance characteristics is shown numerically.

14. A queueing network model to analyze the impact of parallelization of care on patient cycle time.

Science.gov (United States)

Jiang, Lixiang; Giachetti, Ronald E

2008-09-01

The total time a patient spends in an outpatient facility, called the patient cycle time, is a major contributor to overall patient satisfaction. A frequently recommended strategy to reduce the total time is to perform some activities in parallel thereby shortening patient cycle time. To analyze patient cycle time this paper extends and improves upon existing multi-class open queueing network model (MOQN) so that the patient flow in an urgent care center can be modeled. Results of the model are analyzed using data from an urgent care center contemplating greater parallelization of patient care activities. The results indicate that parallelization can reduce the cycle time for those patient classes which require more than one diagnostic and/ or treatment intervention. However, for many patient classes there would be little if any improvement, indicating the importance of tools to analyze business process reengineering rules. The paper makes contributions by implementing an approximation for fork/join queues in the network and by improving the approximation for multiple server queues in both low traffic and high traffic conditions. We demonstrate the accuracy of the MOQN results through comparisons to simulation results.

15. Application of Queueing Theory to the Analysis of Changes in Outpatients' Waiting Times in Hospitals Introducing EMR.

Science.gov (United States)

Cho, Kyoung Won; Kim, Seong Min; Chae, Young Moon; Song, Yong Uk

2017-01-01

This research used queueing theory to analyze changes in outpatients' waiting times before and after the introduction of Electronic Medical Record (EMR) systems. We focused on the exact drawing of two fundamental parameters for queueing analysis, arrival rate (λ) and service rate (µ), from digital data to apply queueing theory to the analysis of outpatients' waiting times. We used outpatients' reception times and consultation finish times to calculate the arrival and service rates, respectively. Using queueing theory, we could calculate waiting time excluding distorted values from the digital data and distortion factors, such as arrival before the hospital open time, which occurs frequently in the initial stage of a queueing system. We analyzed changes in outpatients' waiting times before and after the introduction of EMR using the methodology proposed in this paper, and found that the outpatients' waiting time decreases after the introduction of EMR. More specifically, the outpatients' waiting times in the target public hospitals have decreased by rates in the range between 44% and 78%. It is possible to analyze waiting times while minimizing input errors and limitations influencing consultation procedures if we use digital data and apply the queueing theory. Our results verify that the introduction of EMR contributes to the improvement of patient services by decreasing outpatients' waiting time, or by increasing efficiency. It is also expected that our methodology or its expansion could contribute to the improvement of hospital service by assisting the identification and resolution of bottlenecks in the outpatient consultation process.

16. Quo vadis? : persuasive computing using real time queue information

NARCIS (Netherlands)

Meys, Wouter; Groen, Maarten

2014-01-01

By presenting tourists with real-time information an increase in efficiency and satisfaction of their day planning can be achieved. At the same time, real-time information services can offer the municipality the opportunity to spread the tourists throughout the city centre. An important factor for

17. Fast meldable priority queues

DEFF Research Database (Denmark)

Brodal, Gerth Stølting

1995-01-01

We present priority queues that support the operations Find-Min, Insert, MakeQueue and Meld in worst case time O(1) and Delete and DeleteMin in worst case time O(log n). They can be implemented on the pointer machine and require linear space. The time bounds are optimal for all implementations wh...

18. Sojourn times in finite-capacity processor-sharing queues

NARCIS (Netherlands)

Borst, S.C.; Boxma, O.J.; Hegde, N.

2005-01-01

Motivated by the need to develop simple parsimonious models for evaluating the performance of wireless data systems, we consider finite-capacity processor-sharing systems. For such systems, we analyze the sojourn time distribution, which presents a useful measure for the transfer delay of documents

19. Flow time analysis of load management late arrival discrete time queueing system with dual service rate using hypo geometrical distribution

International Nuclear Information System (INIS)

Shah, S.A.; Shah, W.; Shaikh, F.K.

2012-01-01

Flow time analysis is a powerful concept to analyze the flow time of any arriving customer in any system at any instant. A load management mechanism can be employed very effectively in any queueing system by utilizing a system which provides probability of dual service rate. In this paper, we develop and demonstrate the flow and service processes transition diagram to determine the flow time of a customer in a load management late arrival state dependent finite discrete time queueing system with dual service rate where customers are hypo geometrically distributed. We compute the probability mass function of each starting state and total probability mass function. The obtained analytical results are validated with simulation results for varying values of arrival and service probabilities. (author)

20. The queue-length in GI/G/s queues

Directory of Open Access Journals (Sweden)

Le Gall Pierre

2000-01-01

Full Text Available The distribution of the queue-length in the stationary symmetrical GI/G/s queue is given with an application to the M/G/s queue, particularly in the case of the combination of several packet traffics, with various constant service times, to dimension the buffer capacity.

1. Discrete-time retrial queue with Bernoulli vacation, preemptive resume and feedback customers

Directory of Open Access Journals (Sweden)

Peishu Chen

2015-09-01

Full Text Available Purpose: We consider a discrete-time Geo/G/1 retrial queue where the retrial time follows a general distribution, the server subject to Bernoulli vacation policy and the customer has preemptive resume priority, Bernoulli feedback strategy. The main purpose of this paper is to derive the generating functions of the stationary distribution of the system state, the orbit size and some important performance measures. Design/methodology: Using probability generating function technique, some valuable and interesting performance measures of the system are obtained. We also investigate two stochastic decomposition laws and present some numerical results. Findings: We obtain the probability generating functions of the system state distribution as well as those of the orbit size and the system size distributions. We also obtain some analytical expressions for various performance measures such as idle and busy probabilities, mean orbit and system sizes. Originality/value: The analysis of discrete-time retrial queues with Bernoulli vacation, preemptive resume and feedback customers is interesting and to the best of our knowledge, no other scientific journal paper has dealt with this question. This fact gives the reason why efforts should be taken to plug this gap.

2. On a random area variable arising in discrete-time queues and compact directed percolation

International Nuclear Information System (INIS)

Kearney, Michael J

2004-01-01

A well-known discrete-time, single-server queueing system with mean arrival rate λ and mean departure rate μ is considered from the perspective of the area, A, swept out by the queue occupation process during a busy period. We determine the exact form of the tail of the distribution, Pr(A > x); in particular, we show that Pr(A > x) ∼ Cx -1/4 exp(-Dx 1/2 ) for all ρ ≠ 1, where ρ ≡ λ/μ, and expressions for C and D are given. For the critical case ρ = 1 we show that Pr(A > x) ∼ C'x -1/3 , with C' also given. A simple mapping, used in the derivation, establishes a connection with compact directed percolation on a square lattice. As a corollary, therefore, we are also able to specify the large-area asymptotic behaviour of this model at all points in the phase diagram. This extends previous scaling results, which are only valid close to the percolation threshold

3. Waiting time analysis for MX/G/1 priority queues with/without vacations under random order of service discipline

Directory of Open Access Journals (Sweden)

Norikazu Kawasaki

2000-01-01

Full Text Available We study MX/G/1 nonpreemptive and preemptive-resume priority queues with/without vacations under random order of service (ROS discipline within each class. By considering the conditional waiting times given the states of the system, which an arbitrary message observes upon arrival, we derive the Laplace-Stieltjes transforms of the waiting time distributions and explicitly obtain the first two moments. The relationship for the second moments under ROS and first-come first-served disciplines extends the one found previously by Takacs and Fuhrmann for non-priority single arrival queues.

4. A heavy-traffic theorem for the GI/G/1 queue with a Pareto-type service time distribution

NARCIS (Netherlands)

J.W. Cohen

1997-01-01

textabstractFor the $GI/G/1$-queueing model with traffic load $a<1$, service time distribution $B(t)$ and interarrival time distribution $A(t)$ holds, whenever for $t rightarrow infty$:  quad 1-B(t) sim frac{c{(t/ beta)^nu + {rm O ( {rm e^{-delta t ), quad c>0, quad 1< nu < 2, quad delta >

5. Approximations for the waiting time distribution in an M/G/c priority queue

NARCIS (Netherlands)

Al Hanbali, Ahmad; Alvarez, Elisa; van der Heijden, Matthijs C.

2013-01-01

We investigate the use of priority mechanisms when assigning service engineers to customers as a tool for service differentiation. To this end, we analyze a non-preemptive M/G/c priority queue with various customer classes. For this queue, we present various accurate and fast methods to estimate the

6. Insensitive bounds for the moments of the sojourn time distribution in the M/G/1 processor-sharing queue

NARCIS (Netherlands)

Cheung, S.K.; Berg, J.L. van den; Boucherie, R.J.

2006-01-01

This paper studies the M/G/1 processor-sharing (PS) queue, in particular the sojourn time distribution conditioned on the initial job size. Although several expressions for the Laplace-Stieltjes transform (LST) are known, these expressions are not suitable for computational purposes. This paper

7. Insensitive bounds for the moments of the sojourn time distribution in the M/G/1 processor-sharing queue

NARCIS (Netherlands)

Cheung, S.K.; van den Berg, Hans Leo; Boucherie, Richardus J.

2005-01-01

This paper studies the M/G/1 processor-sharing (PS) queue and the sojourn time distribution conditioned on the initial job size. Although several expressions for the Laplace-Stieltjes transform (LST) are known, these expressions are not applicable for computational purposes. This paper derives

8. A simple derivation of the waiting time distributions in a non-preemptive M/M/c queue with priorities

NARCIS (Netherlands)

van Vianen, Lars A.; Gabor, Adriana F.; van Ommeren, Jan C.W.

2014-01-01

In this article we give a new derivation for the waiting time distributions in an M=M=c queue with multiple priorities and a common service rate by using elementary lattice paths counting. An advantage of the approach is that it does not require inversion of the Laplace-Stieltjes transform.

9. A simple derivation of the waiting time distributions in a non-preemptive M/M/c queue with priorities

NARCIS (Netherlands)

L.A. van Vianen (Lars); A.F. Gabor (Adriana); J.C.W. van Ommeren (Jan-Kees)

2014-01-01

textabstractIn this article we give a new derivation for the waiting time distributions in an M/M/c queue with multiple priorities and a common service rate by using elementary lattice paths counting. An advantage of the approach is that it does not require inversion of the Laplace-Stieltjes

10. Insensitive bounds for the moments of the sojourn time distribution in the M/G/1 processor-sharing queue

NARCIS (Netherlands)

Cheung, S.K.; Cheung, S.K.; van den Berg, Hans Leo; Boucherie, Richardus J.

This paper studies the M/G/1 processor-sharing (PS) queue, in particular the sojourn time distribution conditioned on the initial job size. Although several expressions for the Laplace-Stieltjes transform (LST) are known, these expressions are not suitable for computational purposes. This paper

11. Weak Convergence and Fluid Limits in Optimal Time-to-Empty Queueing Control Problems

Energy Technology Data Exchange (ETDEWEB)

Day, Martin V., E-mail: day@math.vt.edu [Virginia Tech, Department of Mathematics (United States)

2011-12-15

We consider a class of controlled queue length processes, in which the control allocates each server's effort among the several classes of customers requiring its service. Served customers are routed through the network according to (prescribed) routing probabilities. In the fluid rescaling, X{sup n}(t) = 1/nX(nt) , we consider the optimal control problem of minimizing the integral of an undiscounted positive running cost until the first time that X{sup n}=0. Our main result uses weak convergence ideas to show that the optimal value functions V{sup n} of the stochastic control problems for X{sup n}(t) converge (as n{yields}{infinity}) to the optimal value V of a control problem for the limiting fluid process. This requires certain equicontinuity and boundedness hypotheses on (V{sup n}). We observe that these are essentially the same hypotheses that would be needed for the Barles-Perthame approach in terms of semicontinuous viscosity solutions. Sufficient conditions for these equicontinuity and boundedness properties are briefly discussed.

12. Optimal purely functional priority queues

DEFF Research Database (Denmark)

Brodal, Gerth Stølting; Okasaki, Chris

1996-01-01

Brodal recently introduced the first implementation of imperative priority queues to support findMin, insert and meld in O(1) worst-case time, and deleteMin in O(log n) worst-case time. These bounds are asymptotically optimal among all comparison-based priority queues. In this paper, we adapt...... Brodal's data structure to a purely functional setting. In doing so, we both simplify the data structure and clarify its relationship to the binomial queues of Vuillemin, which support all four operations in O(log n) time. Specifically, we derive our implementation from binomial queues in three steps......: first, we reduce the running time of insert to O(1) by eliminating the possibility of cascading links; second, we reduce the running time of findMin to O(1) by adding a global root to hold the minimum element; and finally, we reduce the running time of meld to O(1) by allowing priority queues to contain...

13. Queueing for healthcare.

Science.gov (United States)

Palvannan, R Kannapiran; Teow, Kiok Liang

2012-04-01

Patient queues are prevalent in healthcare and wait time is one measure of access to care. We illustrate Queueing Theory-an analytical tool that has provided many insights to service providers when designing new service systems and managing existing ones. This established theory helps us to quantify the appropriate service capacity to meet the patient demand, balancing system utilization and the patient's wait time. It considers four key factors that affect the patient's wait time: average patient demand, average service rate and the variation in both. We illustrate four basic insights that will be useful for managers and doctors who manage healthcare delivery systems, at hospital or department level. Two examples from local hospitals are shown where we have used queueing models to estimate the service capacity and analyze the impact of capacity configurations, while considering the inherent variation in healthcare.

14. A Survey on Priority Queues

DEFF Research Database (Denmark)

Brodal, Gerth Stølting

2013-01-01

Back in 1964 Williams introduced the binary heap as a basic priority queue data structure supporting the operations Insert and ExtractMin in logarithmic time. Since then numerous papers have been published on priority queues. This paper tries to list some of the directions research on priority qu...

15. Random queues and risk averse users

DEFF Research Database (Denmark)

de Palma, André; Fosgerau, Mogens

2013-01-01

We analyze Nash equilibrium in time of use of a congested facility. Users are risk averse with general concave utility. Queues are subject to varying degrees of random sorting, ranging from strict queue priority to a completely random queue. We define the key “no residual queue” property, which...

16. Analysis of the shortest queue problem

NARCIS (Netherlands)

Adan, I.J.B.F.; Wessels, J.; Zijm, W.H.M.

1989-01-01

In this paper we study a system consisting of two identical servers, each with exponentially distributed service times. Jobs arrive according to a Poisson stream. On arrival a job joins the shortest queue and in case both queues have equal length, he joins either queue with probability ½. We show

17. Analysis of the symmetric shortest queue problem

NARCIS (Netherlands)

Adan, I.J.B.F.; Wessels, J.; Zijm, W.H.M.

1990-01-01

In this paper we study a system consisting of two identical servers, each with exponentially distributed service times. Jobs arrive according to a Poisson stream. On· arrival a job joins the shortest queue and in case both queues have equal lengths, he joins either queue with probability ½. By using

18. Analysis of the symmetric shortest queue problem

NARCIS (Netherlands)

Adan, I.J.B.F.; Wessels, J.; Zijm, W.H.M.

1990-01-01

In this paper we study a system consisting of two identical servers, each with exponentially distributed service times. Jobs arrive according to a Poisson stream. On arrival a job joins the shortest queue and in case both queues have equal lengths, he joins either queue with probability 1/2. By

19. Strategic behavior and social outcomes in a bottleneck queue

DEFF Research Database (Denmark)

Breinbjerg, J.; Sebald, Alexander; Østerdal, L. P.

2016-01-01

the first-in-first-out (FIFO), last-in-first-out (LIFO), and service-in-random-order (SIRO) queue disciplines and compare these predictions to outcomes from a laboratory experiment. In line with our theoretical predictions, we find that people arrive with greater dispersion when participating under the LIFO......We theoretically and experimentally study the differential incentive effects of three well known queue disciplines in a strategic environment in which a bottleneck facility opens and impatient players decide when to arrive. For a class of three-player games, we derive equilibrium arrivals under...... discipline, whereas they tend to arrive immediately under FIFO and SIRO. As a consequence, shorter waiting times are obtained under LIFO as compared to FIFO and SIRO. However, while our theoretical predictions admit higher welfare under LIFO, this is not recovered experimentally as the queue disciplines...

20. Use of queue modelling in the analysis of elective patient treatment governed by a maximum waiting time policy

DEFF Research Database (Denmark)

Kozlowski, Dawid; Worthington, Dave

2015-01-01

chain and discrete event simulation models, to provide an insightful analysis of the public hospital performance under the policy rules. The aim of this paper is to support the enhancement of the quality of elective patient care, to be brought about by better understanding of the policy implications...... on the utilization of public hospital resources. This paper illustrates the use of a queue modelling approach in the analysis of elective patient treatment governed by the maximum waiting time policy. Drawing upon the combined strengths of analytic and simulation approaches we develop both continuous-time Markov...

1. A Hybrid Secure Scheme for Wireless Sensor Networks against Timing Attacks Using Continuous-Time Markov Chain and Queueing Model.

Science.gov (United States)

Meng, Tianhui; Li, Xiaofan; Zhang, Sha; Zhao, Yubin

2016-09-28

Wireless sensor networks (WSNs) have recently gained popularity for a wide spectrum of applications. Monitoring tasks can be performed in various environments. This may be beneficial in many scenarios, but it certainly exhibits new challenges in terms of security due to increased data transmission over the wireless channel with potentially unknown threats. Among possible security issues are timing attacks, which are not prevented by traditional cryptographic security. Moreover, the limited energy and memory resources prohibit the use of complex security mechanisms in such systems. Therefore, balancing between security and the associated energy consumption becomes a crucial challenge. This paper proposes a secure scheme for WSNs while maintaining the requirement of the security-performance tradeoff. In order to proceed to a quantitative treatment of this problem, a hybrid continuous-time Markov chain (CTMC) and queueing model are put forward, and the tradeoff analysis of the security and performance attributes is carried out. By extending and transforming this model, the mean time to security attributes failure is evaluated. Through tradeoff analysis, we show that our scheme can enhance the security of WSNs, and the optimal rekeying rate of the performance and security tradeoff can be obtained.

2. Managing patients' wait time in specialist out-patient clinic using real-time data from existing queue management and ADT systems.

Science.gov (United States)

Ju, John Chen; Gan, Soon Ann; Tan Siew Wee, Justine; Huang Yuchi, Peter; Mei Mei, Chan; Wong Mei Mei, Sharon; Fong, Kam Weng

2013-01-01

In major cancer centers, heavy patients load and multiple registration stations could cause significant wait time, and can be result in patient complains. Real-time patient journey data and visual display are useful tools in hospital patient queue management. This paper demonstrates how we capture patient queue data without deploying any tracing devices; and how to convert data into useful patient journey information to understand where interventions are likely to be most effective. During our system development, remarkable effort has been spent on resolving data discrepancy and balancing between accuracy and system performances. A web-based dashboard to display real-time information and a framework for data analysis were also developed to facilitate our clinics' operation. Result shows our system could eliminate more than 95% of data capturing errors and has improved patient wait time data accuracy since it was deployed.

3. On the Two-Moment Approximation of the Discrete-Time GI/G/1 Queue with a Single Vacation

Directory of Open Access Journals (Sweden)

Doo Ho Lee

2016-01-01

Full Text Available We consider a discrete-time GI/G/1 queue in which the server takes exactly one vacation each time the system becomes empty. The interarrival times of arriving customers, the service times, and the vacation times are all generic discrete random variables. Under our study, we derive an exact transform-free expression for the stationary system size distribution through the modified supplementary variable technique. Utilizing obtained results, we introduce a simple two-moment approximation for the system size distribution. From this, approximations for the mean system size along with the system size distribution could be obtained. Finally, some numerical examples are given to validate the proposed approximation method.

4. A queueing framework for routing problems with time-dependent travel times

NARCIS (Netherlands)

Woensel, van T.; Kerbache, L.; Peremans, H.; Vandaele, N.J.

2007-01-01

Assigning and scheduling vehicle routes in a dynamic environment is a crucial management problem. Despite numerous publications dealing with efficient scheduling methods for vehicle routing, very few addressed the inherent stochastic and dynamic nature of travel times. In this paper, a vehicle

5. Gender and socioeconomic status as determinants of waiting time for inpatient surgery in a system with implicit queue management.

Science.gov (United States)

Arnesen, Kjell E; Erikssen, Jan; Stavem, Knut

2002-12-01

6. An Erlang Loss Queue with Time-Phased Batch Arrivals as a Model for Traffic Control in Communication Networks

Directory of Open Access Journals (Sweden)

Moon Ho Lee

2008-01-01

Full Text Available A multiserver queueing model that does not have a buffer but has batch arrival of customers is considered. In contrast to the standard batch arrival, in which the entire batch arrives at the system during a single epoch, we assume that the customers of a batch (flow arrive individually in exponentially distributed times. The service time is exponentially distributed. Flows arrive according to a stationary Poisson arrival process. The flow size distribution is geometric. The number of flows that can be simultaneously admitted to the system is under control. The loss of any customer from an admitted flow, with a fixed probability, implies termination of the flow arrival. Analysis of the sojourn time and loss probability of an arbitrary flow is performed.

7. Approximations for the waiting-time distribution in an M/P H/c priority queue

NARCIS (Netherlands)

Al Hanbali, Ahmad; Alvarez, Elisa; van der Heijden, Matthijs C.

2015-01-01

We investigate the use of priority mechanisms when assigning service engineers to customers as a tool for service differentiation. To this end, we analyze a non-preemptive M/PH/c priority queue with various customer classes. For this queue, we present various accurate and fast methods to estimate

8. Analysis of queues methods and applications

CERN Document Server

Gautam, Natarajan

2012-01-01

Introduction Analysis of Queues: Where, What, and How?Systems Analysis: Key ResultsQueueing Fundamentals and Notations Psychology in Queueing Reference Notes Exercises Exponential Interarrival and Service Times: Closed-Form Expressions Solving Balance Equations via Arc CutsSolving Balance Equations Using Generating Functions Solving Balance Equations Using Reversibility Reference Notes ExercisesExponential Interarrival and Service Times: Numerical Techniques and Approximations Multidimensional Birth and Death ChainsMultidimensional Markov Chains Finite-State Markov ChainsReference Notes Exerci

9. Priority Queues Resilient to Memory Faults

DEFF Research Database (Denmark)

Jørgensen, Allan Grønlund; Moruz, Gabriel; Mølhave, Thomas

2007-01-01

In the faulty-memory RAM model, the content of memory cells can get corrupted at any time during the execution of an algorithm, and a constant number of uncorruptible registers are available. A resilient data structure in this model works correctly on the set of uncorrupted values. In this paper we...... introduce a resilient priority queue. The deletemin operation of a resilient priority queue returns either the minimum uncorrupted element or some corrupted element. Our resilient priority queue uses $O(n)$ space to store $n$ elements. Both insert and deletemin operations are performed in $O(\\log n...... queues storing only structural information in the uncorruptible registers between operations.... 10. A tandem queue with delayed server release NARCIS (Netherlands) Nawijn, W.M. 1997-01-01 We consider a tandem queue with two stations. The rst station is an s-server queue with Poisson arrivals and exponential service times. After terminating his service in the rst station, a customer enters the second station to require service at an exponential single server, while in the meantime he 11. A geometric process model for M/PH(M/PH)/1/K queue with new service machine procurement lead time Science.gov (United States) Yu, Miaomiao; Tang, Yinghui; Fu, Yonghong 2013-06-01 In this article, we consider a geometric process model for M/PH(M/PH)/1/K queue with new service machine procurement lead time. A maintenance policy (N - 1, N) based on the number of failures of the service machine is introduced into the system. Assuming that a failed service machine after repair will not be 'as good as new', and the spare service machine for replacement is only available by an order. More specifically, we suppose that the procurement lead time for delivering the spare service machine follows a phase-type (PH) distribution. Under such assumptions, we apply the matrix-analytic method to develop the steady state probabilities of the system, and then we obtain some system performance measures. Finally, employing an important Lemma, the explicit expression of the long-run average cost rate for the service machine is derived, and the direct search method is also implemented to determine the optimal value of N for minimising the average cost rate. 12. Priority Queues Resilient to Memory Faults DEFF Research Database (Denmark) Jørgensen, Allan Grønlund; Moruz, Gabriel; Mølhave, Thomas 2007-01-01 In the faulty-memory RAM model, the content of memory cells can get corrupted at any time during the execution of an algorithm, and a constant number of uncorruptible registers are available. A resilient data structure in this model works correctly on the set of uncorrupted values. In this paper we...... introduce a resilient priority queue. The deletemin operation of a resilient priority queue returns either the minimum uncorrupted element or some corrupted element. Our resilient priority queue uses$O(n)$space to store$n$elements. Both insert and deletemin operations are performed in$O(\\log n......+\\delta)$time amortized, where$\\delta$is the maximum amount of corruptions tolerated. Our priority queue matches the performance of classical optimal priority queues in the RAM model when the number of corruptions tolerated is$O(\\log n)$. We prove matching worst case lower bounds for resilient priority... 13. Queueing networks a fundamental approach CERN Document Server Dijk, Nico 2011-01-01 This handbook aims to highlight fundamental, methodological and computational aspects of networks of queues to provide insights and to unify results that can be applied in a more general manner. The handbook is organized into five parts: Part 1 considers exact analytical results such as of product form type. Topics include characterization of product forms by physical balance concepts and simple traffic flow equations, classes of service and queue disciplines that allow a product form, a unified description of product forms for discrete time queueing networks, insights for insensitivity, and aggregation and decomposition results that allow subnetworks to be aggregated into single nodes to reduce computational burden. Part 2 looks at monotonicity and comparison results such as for computational simplification by either of two approaches: stochastic monotonicity and ordering results based on the ordering of the proces generators, and comparison results and explicit error bounds based on an underlying Markov r... 14. Markov-modulated M/G/1-type queue in heavy traffic and its application to time-sharing disciplines NARCIS (Netherlands) H. Thorsdottir (Halldora); I.M. Verloop (Maaike) 2016-01-01 textabstractThis paper deals with a single-server queue with modulated arrivals, service requirements and service capacity. In our first result, we derive the mean of the total workload assuming generally distributed service requirements and any service discipline which does not depend on the 15. Designing of vague logic based multilevel feedback queue scheduler Directory of Open Access Journals (Sweden) Supriya Raheja 2016-03-01 Full Text Available Multilevel feedback queue scheduler suffers from major issues of scheduling such as starvation for long tasks, fixed number of queues, and static length of time quantum in each queue. These factors directly affect the performance of the scheduler. At many times impreciseness exists in attributes of tasks which make the performance even worse. In this paper, our intent is to improve the performance by providing a solution to these issues. We design a multilevel feedback queue scheduler using a vague set which we call as VMLFQ scheduler. VMLFQ scheduler intelligently handles the impreciseness and defines the optimum number of queues as well as the optimal size of time quantum for each queue. It also resolves the problem of starvation. This paper simulates and analyzes the performance of VMLFQ scheduler with the other multilevel feedback queue techniques using MatLab. 16. Queueing systems with constant service time and evaluation of M/D/1,k DEFF Research Database (Denmark) Iversen, Villy Bæk 1997-01-01 Systems with constant service times have the particular property that the customers leave the servers in the same order in which they areaccepted for service. Probabilitites of integral waiting times can be expressed by the state probabilities, and non-integral waiting timescan be expressed... 17. Priority queues CERN Document Server Jaiswal, N.K 1968-01-01 In this book, we study theoretical and practical aspects of computing methods for mathematical modelling of nonlinear systems. A number of computing techniques are considered, such as methods of operator approximation with any given accuracy; operator interpolation techniques including a non-Lagrange interpolation; methods of system representation subject to constraints associated with concepts of causality, memory and stationarity; methods of system representation with an accuracy that is the best within a given class of models; methods of covariance matrix estimation;methods for low-rank mat 18. discouraged by queue length Directory of Open Access Journals (Sweden) P. R. Parthasarathy 2001-01-01 Full Text Available The transient solution is obtained analytically using continued fractions for a state-dependent birth-death queue in which potential customers are discouraged by the queue length. This queueing system is then compared with the well-known infinite server queueing system which has the same steady state solution as the model under consideration, whereas their transient solutions are different. A natural measure of speed of convergence of the mean number in the system to its stationarity is also computed. 19. Real-Time Wait-Free Queues using Micro-Transactions OpenAIRE Meawad, Fadi; Iyer, Karthik; Schoeberl, Martin; Vitek, Jan 2011-01-01 This paper evaluates the applicability of transactional mem- ory to the implementation of dierent non-blocking data structures in the context of the Real-time Specication for Java. In particular, we argue that hardware support for micro-transaction allows us to implement eciently data structures that are often dicult to realize with the atomic operations provided by stock hardware. Our main imple- mentation platform is the Java Optimized Processor sys- tem. We report on the performance of dat... 20. Real-Time Wait-Free Queues using Micro-Transactions DEFF Research Database (Denmark) Meawad, Fadi; Iyer, Karthik; Schoeberl, Martin 2011-01-01 This paper evaluates the applicability of transactional mem- ory to the implementation of dierent non-blocking data structures in the context of the Real-time Specication for Java. In particular, we argue that hardware support for micro-transaction allows us to implement eciently data structures...... that are often dicult to realize with the atomic operations provided by stock hardware. Our main imple- mentation platform is the Java Optimized Processor sys- tem. We report on the performance of data structures imple- mented with locks, compare and swap and micro-transactions. Our results conrm... 1. On the single-server retrial queue Directory of Open Access Journals (Sweden) Djellab Natalia V. 2006-01-01 Full Text Available In this work, we review the stochastic decomposition for the number of customers in M/G/1 retrial queues with reliable server and server subjected to breakdowns which has been the subject of investigation in the literature. Using the decomposition property of M/G/1 retrial queues with breakdowns that holds under exponential assumption for retrial times as an approximation in the non-exponential case, we consider an approximate solution for the steady-state queue size distribution. 2. Concurrent array-based queue Science.gov (United States) Heidelberger, Philip; Steinmacher-Burow, Burkhard 2015-01-06 According to one embodiment, a method for implementing an array-based queue in memory of a memory system that includes a controller includes configuring, in the memory, metadata of the array-based queue. The configuring comprises defining, in metadata, an array start location in the memory for the array-based queue, defining, in the metadata, an array size for the array-based queue, defining, in the metadata, a queue top for the array-based queue and defining, in the metadata, a queue bottom for the array-based queue. The method also includes the controller serving a request for an operation on the queue, the request providing the location in the memory of the metadata of the queue. 3. Fundamentals of queueing theory CERN Document Server Gross, Donald; Thompson, James M; Harris, Carl M 2013-01-01 Praise for the Third Edition ""This is one of the best books available. Its excellent organizational structure allows quick reference to specific models and its clear presentation . . . solidifies the understanding of the concepts being presented.""-IIE Transactions on Operations Engineering Thoroughly revised and expanded to reflect the latest developments in the field, Fundamentals of Queueing Theory, Fourth Edition continues to present the basic statistical principles that are necessary to analyze the probabilistic nature of queues. Rather than pre 4. Implementation of shared queues OpenAIRE Motte, Nicolas 2012-01-01 The transactional framework used to develop Amadeus C++ applications is based on a mechanism of queues to manage the message exchanges between components. These structures are protected from concurrent access thanks to synchronization services provided by Linux. But theses services have a cost in term of performance and they bound the volume of messages transmitted by these queues. In a first step, I have to investigate on the state-of-the-art in term of management algorithms o... 5. Modelling M/G/1 queueing systems with server vacations using ... African Journals Online (AJOL) Simple numerical examples are also provided to illustrate the func- ... M/G/1/N queueing systems with server vacations under a limited service discipline ...... system contents in a discrete-time non-preemptive priority queue with general service. 6. The impact of reneging in processor sharing queues NARCIS (Netherlands) Gromoll, H.C.; Robert, Ph.; Zwart, B.; Bakker, R.F. 2006-01-01 We investigate an overloaded processor sharing queue with renewal arrivals and generally distributed service times. Impatient customers may abandon the queue, or renege, before completing service. The random time representing a customer’s patience has a general distribution and may be dependent on 7. The Completion of Non-Steady-State Queue Model on The Queue System in Dr. Yap Eye Hospital Yogyakarta Science.gov (United States) Helmi Manggala Putri, Arum; Subekti, Retno; Binatari, Nikenasih 2017-06-01 Dr Yap Eye Hospital Yogyakarta is one of the most popular reference eye hospitals in Yogyakarta. There are so many patients coming from other cities and many of them are BPJS (Badan Penyelenggara Jaminan Sosial, Social Security Administrative Bodies) patients. Therefore, it causes numerous BPJS patients were in long queue at counter C of the registration section so that it needs to be analysed using queue system. Queue system analysis aims to give queue model overview and determine its effectiveness measure. The data collecting technique used in this research are by interview and observation. After getting the arrival data and the service data of BPJS patients per 5 minutes, the next steps are investigating steady-state condition, examining the Poisson distribution, determining queue models, and counting the effectiveness measure. Based on the result of data observation on Tuesday, February 16th, 2016, it shows that the queue system at counter C has (M/M/1):(GD/∞/∞) queue model. The analysis result in counter C shows that the queue system is a non-steady-state condition. Three ways to cope a non-steady-state problem on queue system are proposed in this research such as bounding the capacity of queue system, adding the servers, and doing Monte Carlo simulation. The queue system in counter C will reach steady-state if the capacity of patients is not more than 52 BPJS patients or adding one more server. By using Monte Carlo simulation, it shows that the effectiveness measure of the average waiting time for BPJS patients in counter C is 36 minutes 65 seconds. In addition, the average queue length of BPJS patients is 11 patients. 8. Two Coupled Queues with Vastly Different Arrival Rates: Critical Loading Case Directory of Open Access Journals (Sweden) Charles Knessl 2011-01-01 Full Text Available We consider two coupled queues with a generalized processor sharing service discipline. The second queue has a much smaller Poisson arrival rate than the first queue, while the customer service times are of comparable magnitude. The processor sharing server devotes most of its resources to the first queue, except when it is empty. The fraction of resources devoted to the second queue is small, of the same order as the ratio of the arrival rates. We assume that the primary queue is heavily loaded and that the secondary queue is critically loaded. If we let the small arrival rate to the secondary queue be O(ε, where 0≤ε≪1, then in this asymptotic limit the number of customers in the first queue will be large, of order O(ε-1, while that in the second queue will be somewhat smaller, of order O(ε-1/2. We obtain a two-dimensional diffusion approximation for this model and explicitly solve for the joint steady state probability distribution of the numbers of customers in the two queues. This work complements that in (Morrison, 2010, which the second queue was assumed to be heavily or lightly loaded, leading to mean queue lengths that were O(ε-1 or O(1, respectively. 9. Interacting queues in heavy traffic NARCIS (Netherlands) J.A. Morrison; S.C. Borst (Sem) 2010-01-01 htmlabstractWe consider a system of parallel queues with Poisson arrivals and exponentially distributed service requirements. The various queues are coupled through their service rates, causing a complex dynamic interaction. Specifically, the system consists of one primary queue and several 10. The symmetric longest queue system NARCIS (Netherlands) van Houtum, Geert-Jan; Adan, Ivo; van der Wal, Jan 1997-01-01 We derive the performance of the exponential symmetric longest queue system from two variants: a longest queue system with Threshold Rejection of jobs and one with Threshold Addition of jobs. It is shown that these two systems provide lower and upper bounds for the performance of the longest queue 11. Note on a tandem queue with delayed server release NARCIS (Netherlands) Nawijn, W.M. 2000-01-01 We consider a tandem queue with two stations. The first station is an$s$-server queue with Poisson arrivals and exponential service times. After terminating his service in the first station, a customer enters the second station to require service at a single server, while in the meantime he is 12. Analysis of the asymmetrical shortest two-server queueing model NARCIS (Netherlands) J.W. Cohen 1995-01-01 textabstractThis study presents the analytic solution for the asymmetrical two-server queueing model with arriving customers joining the shorter queue for the case with Poisson arrivals and negative exponentially distributed service times. The bivariate generating function of the stationary joint 13. Performance analysis of tandem queues with small buffers NARCIS (Netherlands) Vuuren, van M.; Adan, I.J.B.F.; Papadopoulos, C.T. 2005-01-01 In this paper we present an approximation for the performance analysis of single-server tandem queues with small buffers and generally distributed service times. The approximation is based on decomposition of the tandem queue in subsystems, the parameters of which are determined by an iterative 14. Large Deviation Bounds for a Polling System with Two Queues and Multiple Servers OpenAIRE Wei, Fen 2004-01-01 In this paper, we present large deviation bounds for a discrete-time polling system consisting of two-par-allel queues and m servers. The arrival process in each queue is an arbitrary, and possibly correlated, stochastic process. Each server (serves) independently serves the two queues according to a Bernoulli service schedule. Using large deviation techniques, we analyze the tail behavior of the stationary distribution of the queue length processes, and derive upper and lower bounds of the b... 15. A tandem queue with delayed server release OpenAIRE Nawijn, W.M. 1997-01-01 We consider a tandem queue with two stations. The rst station is an s-server queue with Poisson arrivals and exponential service times. After terminating his service in the rst station, a customer enters the second station to require service at an exponential single server, while in the meantime he is blocking his server in station 1 until he completes service in station 2, whereupon the server in station 1 is released. An analysis of the generating function of the simultaneous probability di... 16. Bad Luck When Joining the Shortest Queue NARCIS (Netherlands) Blanc, J.P.C. 2008-01-01 A frequent observation in service systems with queues in parallel is that customers in other queues tend to be served faster than those in one’s own queue. This paper quantifies the probability that one’s service would have started earlier if one had joined another queue than the queue that was 17. Transient queue-size distribution in a finite-capacity queueing system with server breakdowns and Bernoulli feedback Science.gov (United States) Kempa, Wojciech M. 2017-12-01 A finite-capacity queueing system with server breakdowns is investigated, in which successive exponentially distributed failure-free times are followed by repair periods. After the processing a customer may either rejoin the queue (feedback) with probability q, or definitely leave the system with probability 1 - q. The system of integral equations for transient queue-size distribution, conditioned by the initial level of buffer saturation, is build. The solution of the corresponding system written for Laplace transforms is found using the linear algebraic approach. The considered queueing system can be successfully used in modelling production lines with machine failures, in which the parameter q may be considered as a typical fraction of items demanding corrections. Morever, this queueing model can be applied in the analysis of real TCP/IP performance, where q stands for the fraction of packets requiring retransmission. 18. Markovian inventory model with two parallel queues, jockeying and impatient customers Directory of Open Access Journals (Sweden) Jeganathan K. 2016-01-01 Full Text Available This article presents a perishable stochastic inventory system under continuous review at a service facility consisting of two parallel queues with jockeying. Each server has its own queue, and jockeying among the queues is permitted. The capacity of each queue is of finite size L. The inventory is replenished according to an (s; S inventory policy and the replenishing times are assumed to be exponentially distributed. The individual customer is issued a demanded item after a random service time, which is distributed as negative exponential. The life time of each item is assumed to be exponential. Customers arrive according to a Poisson process and on arrival; they join the shortest feasible queue. Moreover, if the inventory level is more than one and one queue is empty while in the other queue, more than one customer are waiting, then the customer who has to be received after the customer being served in that queue is transferred to the empty queue. This will prevent one server from being idle while the customers are waiting in the other queue. The waiting customer independently reneges the system after an exponentially distributed amount of time. The joint probability distribution of the inventory level, the number of customers in both queues, and the status of the server are obtained in the steady state. Some important system performance measures in the steady state are derived, so as the long-run total expected cost rate. 19. Buffer Overflow Period in a MAP Queue Directory of Open Access Journals (Sweden) Andrzej Chydzinski 2007-01-01 Full Text Available The buffer overflow period in a queue with Markovian arrival process (MAP and general service time distribution is investigated. The results include distribution of the overflow period in transient and stationary regimes and the distribution of the number of cells lost during the overflow interval. All theorems are illustrated via numerical calculations. 20. Semigroup Method on a MX/G/1 Queueing Model Directory of Open Access Journals (Sweden) Alim Mijit 2013-01-01 Full Text Available By using the Hille-Yosida theorem, Phillips theorem, and Fattorini theorem in functional analysis we prove that the MX/G/1 queueing model with vacation times has a unique nonnegative time-dependent solution. 1. The curse of the first-in-first-out queue discipline DEFF Research Database (Denmark) Platz, Trine Tornøe; Østerdal, Lars Peter Raahave 2017-01-01 We consider a game in which a large number of identical agents choose when to queue up at a single server after it opens. Agents are impatient for service and also incur a cost proportional to time spent in the queue. We show that the first-in–first-out queue discipline and the last......-in–first-out queue discipline both lead to a unique equilibrium arrival distribution. However, among all work-conserving queue disciplines, the first-in–first-out performs the worst in terms of equilibrium utility and welfare, while the last-in–first-out performs the best.... 2. Electromagnetic nuclear life time - theoretical context International Nuclear Information System (INIS) Niez, J.J. 2000-01-01 One describes here the theoretical tools which are needed for evaluating the nuclear lifetime of a nucleus dipped into electromagnetic surroundings which are composed of electrons and photons. The case where this environment is a material or a cavity will be treated in a following report. (Author) 3. QUEUEING DISCIPLINES BASED ON PRIORITY MATRIX Directory of Open Access Journals (Sweden) Taufik I. Aliev 2014-11-01 Full Text Available The paper deals with queueing disciplines for demands of general type in queueing systems with multivendor load. A priority matrix is proposed to be used for the purpose of mathematical description of such disciplines, which represents the priority type (preemptive priority, not preemptive priority or no priority between any two demands classes. Having an intuitive and simple way of priority assignment, such description gives mathematical dependencies of system operation characteristics on its parameters. Requirements for priority matrix construction are formulated and the notion of canonical priority matrix is given. It is shown that not every matrix, constructed in accordance with such requirements, is correct. The notion of incorrect priority matrix is illustrated by an example, and it is shown that such matrixes do not ensure any unambiguousness and determinacy in design of algorithm, which realizes corresponding queueing discipline. Rules governing construction of correct matrixes are given for canonical priority matrixes. Residence time for demands of different classes in system, which is the sum of waiting time and service time, is considered as one of the most important characteristics. By introducing extra event method Laplace transforms for these characteristics are obtained, and mathematical dependencies are derived on their basis for calculation of two first moments for corresponding characteristics of demands queueing 4. The ×-BMAP/G/1 Queueing Model: Queue Contents and Delay Analysis Directory of Open Access Journals (Sweden) Bart Steyaert 2011-01-01 Full Text Available We consider a single-server discrete-time queueing system with N sources, where each source is modelled as a correlated Markovian customer arrival process, and the customer service times are generally distributed. We focus on the analysis of the number of customers in the queue, the amount of work in the queue, and the customer delay. For each of these quantities, we will derive an expression for their steady-state probability generating function, and from these results, we derive closed-form expressions for key performance measures such as their mean value, variance, and tail distribution. A lot of emphasis is put on finding closed-form expressions for these quantities that reduce all numerical calculations to an absolute minimum. 5. A unifying property for distribution-sensitive priority queues DEFF Research Database (Denmark) Elmasry, Amr Ahmed Abd Elmoneim; Farzan, Arash; Iacono, John 2011-01-01 , before) the last access of x and are still in the priority queue at the time when the corresponding operation is performed. Our priority queue then has both the working-set and the queueish properties; and, more strongly, it satisfies these properties in the worst-case sense. We also argue...... that these bounds are the best possible with respect to the considered measures. Moreover, we modify our priority queue to satisfy a new unifying property - the time-finger property - which encapsulates both the working-set and the queueish properties. In addition, we prove that the working-set bound......We present a priority queue that supports the operations: insert in worst-case constant time, and delete, delete-min, find-min and decrease-key on an element x in worst-case O(lg(min{wx, qx} + 2)) time, where wx (respectively, qx) is the number of elements that were accessed after (respectively... 6. Age Replacement and Service Rate Control of Stochastically Degrading Queues National Research Council Canada - National Science Library Chapin, Patrick 2004-01-01 This thesis considers the problem of optimally selecting a periodic replacement time for a multiserver queueing system in which each server is subject to degradation as a function of the mean service... 7. A single-server queue with random accumulation level Directory of Open Access Journals (Sweden) Jewgeni H. Dshalalow 1991-01-01 The author establishes an ergodicity criterion for both the queueing process with continuous time parameter and the imbedded process. Under this criterion, the author obtains explicit formulas for the stationary distributions of both processes by using semi-regenerative techniques. 8. Lévy-driven queues NARCIS (Netherlands) Debicki, K.G.; Mandjes, M.R.H. 2012-01-01 This survey addresses the class of queues with Lévy input, which covers the classical M/G/1 queue and the reflected Brownian motion as special cases. First the stationary behavior is treated, with special attention to the case of the input process having one-sided jumps (i.e., spectrally one-sided 9. A diffusion model for two parallel queues with processor sharing: transient behavior and asymptotics Directory of Open Access Journals (Sweden) Charles Knessl 1999-01-01 Full Text Available We consider two identical, parallel M/M/1 queues. Both queues are fed by a Poisson arrival stream of rate λ and have service rates equal to μ. When both queues are non-empty, the two systems behave independently of each other. However, when one of the queues becomes empty, the corresponding server helps in the other queue. This is called head-of-the-line processor sharing. We study this model in the heavy traffic limit, where ρ=λ/μ→1. We formulate the heavy traffic diffusion approximation and explicitly compute the time-dependent probability of the diffusion approximation to the joint queue length process. We then evaluate the solution asymptotically for large values of space and/or time. This leads to simple expressions that show how the process achieves its stead state and other transient aspects. 10. Markov-modulated infinite-server queues driven by a common background process OpenAIRE Mandjes , Michel; De Turck , Koen 2016-01-01 International audience; This paper studies a system with multiple infinite-server queues which are modulated by a common background process. If this background process, being modeled as a finite-state continuous-time Markov chain, is in state j, then the arrival rate into the i-th queue is λi,j, whereas the service times of customers present in this queue are exponentially distributed with mean µ −1 i,j ; at each of the individual queues all customers present are served in parallel (thus refl... 11. On the busy period of discretized GI/GI/infinity queue International Nuclear Information System (INIS) Dvurecenskij, A.; Ososkov, G.A. 1982-01-01 The problem of determining the distribution of the busy period, i. e., of the time when at least one customer is served, of the discretized queueing system with infinitely many servers is investigated. Moreover, the idle period and the cycle of a queue are studied. The recurrent formulae are determined and in particular case of a queue with the geometric input the simpler recurrent formulae are given. Those problems arise in the discrete blob length determination in track chambers in high energy physics 12. Optimal control of two queues in series International Nuclear Information System (INIS) Moustafa, M.S.; Mohammed, R.M. 1994-08-01 In this paper we give a fairly complete survey of the available results on the control of arrival and service rates for both single queue and networks of queues. We also study two M/M/1 queues in series. At the first queue, the arrival and the service rates are chosen in pair from a finite set whenever the queue lengths at both queues change. Each choice has a switching cost depending on the chosen rates and the queue lengths. At the second queue, the arrival and the service rates are fixed. Our objective is to find a policy for dynamically choosing rates, based on the current rates and queues lengths that minimizes the expected total discounted cost over a finite horizon, numerical results are given. (author). 8 refs, 1 fig 13. Convolution Model of a Queueing System with the cFIFO Service Discipline Directory of Open Access Journals (Sweden) Sławomir Hanczewski 2016-01-01 Full Text Available This article presents an approximate convolution model of a multiservice queueing system with the continuous FIFO (cFIFO service discipline. The model makes it possible to service calls sequentially with variable bit rate, determined by unoccupied (free resources of the multiservice server. As compared to the FIFO discipline, the cFIFO queue utilizes the resources of a multiservice server more effectively. The assumption in the model is that the queueing system is offered a mixture of independent multiservice Bernoulli-Poisson-Pascal (BPP call streams. The article also discusses the results of modelling a number of queueing systems to which different, non-Poissonian, call streams are offered. To verify the accuracy of the model, the results of the analytical calculations are compared with the results of simulation experiments for a number of selected queueing systems. The study has confirmed the accuracy of all adopted theoretical assumptions for the proposed analytical model. 14. A single-server queue with batch arrivals and semi-Markov services NARCIS (Netherlands) Abhishek,; Boon, M.A.A.; Boxma, O.J.; Núñez-Queija, R. 2017-01-01 We investigate the transient and stationary queue length distributions of a class of service systems with correlated service times. The classical (Formula presented.) queue with semi-Markov service times is the most prominent example in this class and serves as a vehicle to display our results. The 15. Measurement-theoretic foundations of time discounting in economics OpenAIRE Conrad Heilmann 2008-01-01 In economics, the concept of time discounting introduces weights on future goods to make these less valuable. Yet, both the conceptual motivation for time discounting and its specic functional form remain contested. To address these problems, this paper provides a measurement-theoretic framework of representation for time discounting. The representation theorem characterises time discounting factors by representations of time dierences. This general result can be interpreted with existing the... 16. Queue-length balance equations in multiclass multiserver queues and their generalizations NARCIS (Netherlands) Boon, M.A.A.; Boxma, O.J.; Kella, O.; Miyazawa, M. 2017-01-01 A classical result for the steady-state queue-length distribution of single-class queueing systems is the following: The distribution of the queue length just before an arrival epoch equals the distribution of the queue length just after a departure epoch. The constraint for this result to be valid 17. Queue-length balance equations in multiclass multiserver queues and their generalizations NARCIS (Netherlands) Boon, M.; Boxma, O.J.; Kella, O.; Miyazawa, M. 2017-01-01 A classical result for the steady-state queue-length distribution of single-class queueing systems is the following: the distribution of the queue length just before an arrival epoch equals the distribution of the queue length just after a departure epoch. The constraint for this result to be valid 18. Decomposing the queue length distribution of processor-sharing models into queue lengths of permanent customer queues NARCIS (Netherlands) Cheung, S.K.; van den Berg, Hans Leo; Boucherie, Richardus J. 2005-01-01 We obtain a decomposition result for the steady state queue length distribution in egalitarian processor-sharing (PS) models. In particular, for an egalitarian PS queue with$K$customer classes, we show that the marginal queue length distribution for class$k$factorizes over the number of other 19. E-Queue Mobile Application Directory of Open Access Journals (Sweden) Khong Yeen Lai 2017-01-01 Full Text Available Waiting in line is a common experience in daily life, whether for a table at a popular restaurant or for the service at a bank. This experience is not always pleasant for most of people because they always have to wait for a long time to be serviced. The ability to interact with waiting customers is highly desirable because it allows businesses the opportunity to optimize their existing services and offer new services to waiting customers. However, interacting with individuals waiting in a queue has been inefficient and costly because employees must either talk with each waiting customer on an ongoing basis or the business must provide high tech devices that interact with each waiting customer. Agile methodology which will be used to develop this application, it incorporates the SDLC phases starting from the Planning phase up to the Maintenance phase. End of the research, we found that majority of respondents are prefer to use the proposed system compared with current method. 20. Optimal dispatching in a tandem queue NARCIS (Netherlands) van Leeuwen, D.; Núñez Queija, R. 2017-01-01 We investigate a Markovian tandem queueing model in which service to the first queue is provided in batches. The main goal is to choose the batch sizes so as to minimize a linear cost function of the mean queue lengths. This model can be formulated as a Markov Decision Process (MDP) for which the 1. Queue and stack sorting algorithm optimization and performance analysis Science.gov (United States) Qian, Mingzhu; Wang, Xiaobao 2018-04-01 Sorting algorithm is one of the basic operation of a variety of software development, in data structures course specializes in all kinds of sort algorithm. The performance of the sorting algorithm is directly related to the efficiency of the software. A lot of excellent scientific research queue is constantly optimizing algorithm, algorithm efficiency better as far as possible, the author here further research queue combined with stacks of sorting algorithms, the algorithm is mainly used for alternating operation queue and stack storage properties, Thus avoiding the need for a large number of exchange or mobile operations in the traditional sort. Before the existing basis to continue research, improvement and optimization, the focus on the optimization of the time complexity of the proposed optimization and improvement, The experimental results show that the improved effectively, at the same time and the time complexity and space complexity of the algorithm, the stability study corresponding research. The improvement and optimization algorithm, improves the practicability. 2. A course on queueing models CERN Document Server Jain, Joti Lal; Böhm, Walter 2006-01-01 The application of engineering principles in divergent fields such as management science and communications as well as the advancement of several approaches in theory and computation have led to growing interest in queueing models, creating the need for a comprehensive text. Emphasizing Markovian structures and the techniques that occur in different models, A Course on Queueing Models discusses recent developments in the field, different methodological tools - some of which are not available elsewhere - and computational techniques.While most books essentially address the classical methods of 3. Probability, statistics, and queueing theory CERN Document Server Allen, Arnold O 1990-01-01 This is a textbook on applied probability and statistics with computer science applications for students at the upper undergraduate level. It may also be used as a self study book for the practicing computer science professional. The successful first edition of this book proved extremely useful to students who need to use probability, statistics and queueing theory to solve problems in other fields, such as engineering, physics, operations research, and management science. The book has also been successfully used for courses in queueing theory for operations research students. This second edit 4. An M/G/1 queue with multiple types of feedback and gated vacations NARCIS (Netherlands) O.J. Boxma (Onno); U. Yechiali 1995-01-01 textabstractThis paper considers a single-server queue with Poisson arrivals and multiple customer feedbacks. If the first service attempt of a newly arriving customer is not successful, he returns to the end of the queue for another service attempt, with a different service time distribution. He 5. Slowdown in the$M/M/1$discriminatory processor-sharing queue NARCIS (Netherlands) Cheung, S.K.; Kim, Bara; Kim, Jeongsim 2008-01-01 We consider a queue with multiple K job classes, Poisson arrivals, and exponentially distributed required service times in which a single processor serves according to the discriminatory processor-sharing (DPS) discipline. For this queue, we obtain the first and second moments of the slowdown, which 6. Global and local asymptotics for the busy period of an M/G/1 queue NARCIS (Netherlands) Denisov, D.E.; Shneer, V. 2010-01-01 We consider an M/G/1 queue with subexponential service times. We give a simple derivation of the global and local asymptotics for the busy period. Our analysis relies on the explicit formula for the joint distribution for the number of customers and the length of the busy period of an M/G/1 queue. 7. Queue balancing of load and expedition service in a cement industry in Brazil Directory of Open Access Journals (Sweden) David Custódio de Sena 2013-11-01 Full Text Available The load and weight process in a cement industry is one of logistic step that shows the biggest time of occurrence, increasing the queues. This study aims to do a scenarios to solve this queue problem. This way, it pretends to find an better resources distribuition. 8. Transient Analysis of an M/M/1 queue with Multiple Exponential Vacation and N-Policy Directory of Open Access Journals (Sweden) Vijayashree KV 2015-12-01 Full Text Available A single server Markovian queueing model is considered. The arrivals are allowed to join the queue according to a Poisson distribution and the service takes place according to an exponential distribution. Whenever the system is empty, the server goes for a vacation and return back to the system after N or more customers are found in the system. If the number of customers in the system is less than ‘’ then the server takes another vacation. In this paper, we obtain explicit expressions for the time dependent system size probabilities of such a model using Laplace transform and generating function techniques. Numerical illustrations are added to support the theoretical results obtained. 9. New Approach for Finding Basic Performance Measures of Single Server Queue Directory of Open Access Journals (Sweden) Siew Khew Koh 2014-01-01 Full Text Available Consider the single server queue in which the system capacity is infinite and the customers are served on a first come, first served basis. Suppose the probability density function f(t and the cumulative distribution function F(t of the interarrival time are such that the rate f(t/1-F(t tends to a constant as t→∞, and the rate computed from the distribution of the service time tends to another constant. When the queue is in a stationary state, we derive a set of equations for the probabilities of the queue length and the states of the arrival and service processes. Solving the equations, we obtain approximate results for the stationary probabilities which can be used to obtain the stationary queue length distribution and waiting time distribution of a customer who arrives when the queue is in the stationary state. 10. The evaluation of a formalized queue management system for coronary angiography waiting lists. Science.gov (United States) Alter, D A; Newman, Alice M; Cohen, Eric A; Sykora, Kathy; Tu, Jack V 2005-11-01 Lengthy waiting lists for coronary angiography have been described in many health care systems worldwide. The extent to which formal queue management systems may improve the prioritization and survival of patients in the angiography queue is unknown. To prospectively evaluate the performance of a formal queue management system for patients awaiting coronary angiography in Ontario. The coronary angiography urgency scale, a formal queue management system developed in 1993 using a modified Delphi panel, allocates recommended maximum waiting times (RMWTs) in accordance with clinical necessity. By using a provincial clinical registry, 35,617 consecutive patients referred into the coronary angiography queue between April 1, 2001, and March 31, 2002, were prospectively tracked. Cox proportional hazards models were used to examined mortality risk across urgency after adjusting for additional clinical and comorbid factors. Good agreement was determined in urgency ratings between scores from the coronary angiography urgency scale and implicit physician judgement, which was obtained independently at the time of the index referral (weighted kappa = 0.49). The overall mortality in the queue was 0.3% (0.47%, 0.26% and 0.13% for urgent, semiurgent and elective patients, respectively). Urgency, as specified by the coronary angiography urgency scale, was the strongest predictor of death in the queue (Pqueue management system may decrease mortality in the coronary angiography queue. The authors recommend its implementation in health care systems where patients experience excessive waiting time delays for coronary angiography. 11. Upper Bounds on Performance Measures of Heterogeneous // Queues Directory of Open Access Journals (Sweden) F. S. Q. Alves 2011-01-01 Full Text Available In many real-life queueing systems, the servers are often heterogeneous, namely they work at different rates. This paper provides a simple method to compute tight upper bounds on two important performance measures of single-class heterogeneous multi-server Markovian queueing systems, namely the average number in queue and the average waiting time in queue. This method is based on an expansion of the state space that is followed by an approximate reduction of the state space, only considering the most probable states. In most cases tested, we were able to approximate the actual behavior of the system with smaller errors than those obtained from traditional homogeneous multiserver Markovian queues, as shown by GPSS simulations. In addition, we have correlated the quality of the approximation with the degree of heterogeneity of the system, which was evaluated using its Gini index. Finally, we have shown that the bounds are robust and still useful, even considering quite different allocation strategies. A large number of simulation results show the accuracy of the proposed method that is better than that of classical homogeneous multiserver Markovian formulae in many situations. 12. Fluid queues and regular variation NARCIS (Netherlands) Boxma, O.J. 1996-01-01 This paper considers a fluid queueing system, fed by N independent sources that alternate between silence and activity periods. We assume that the distribution of the activity periods of one or more sources is a regularly varying function of index ¿. We show that its fat tail gives rise to an even 13. Fluid queues and regular variation NARCIS (Netherlands) O.J. Boxma (Onno) 1996-01-01 textabstractThis paper considers a fluid queueing system, fed by$N$independent sources that alternate between silence and activity periods. We assume that the distribution of the activity periods of one or more sources is a regularly varying function of index$zeta$. We show that its fat tail 14. Research into Queueing Network Theory. Science.gov (United States) 1977-09-01 and Zeigler, B. (1975) "Equilibrium properties of arbitrarily interconnected queueing netowrks ," Tech. Report 75-4, Computer and Communication...Associate. The project was extremely fortunate to secure the services of Dr. Wendel. Dr. Wendel was a project member for one month in the summer of 15. Vacation queueing models theory and applications CERN Document Server Tian, Naishuo 2006-01-01 A classical queueing model consists of three parts - arrival process, service process, and queue discipline. However, a vacation queueing model has an additional part - the vacation process which is governed by a vacation policy - that can be characterized by three aspects: 1) vacation start-up rule; 2) vacation termination rule, and 3) vacation duration distribution. Hence, vacation queueing models are an extension of classical queueing theory. Vacation Queueing Models: Theory and Applications discusses systematically and in detail the many variations of vacation policy. By allowing servers to take vacations makes the queueing models more realistic and flexible in studying real-world waiting line systems. Integrated in the book's discussion are a variety of typical vacation model applications that include call centers with multi-task employees, customized manufacturing, telecommunication networks, maintenance activities, etc. Finally, contents are presented in a "theorem and proof" format and it is invaluabl... 16. Energy confinement time and tokamak ignition - a theoretical viewpoint International Nuclear Information System (INIS) Sigmar, D.J.; Hsu, C.T. 1989-01-01 A rigorous approach developed earlier to obtain the global energy confinement time from theory based local thermal transport coefficients is applied to investigate the approach to thermonuclear fusion in the tokamak. Theory leads naturally to a generalized 'offset' form for the global energy confinement time. The limitations of the theoretical paradigm presented here are discussed and specific ignition contour results for a large 5 Tesla and 12 Tesla ignition experiment are given. (orig.) [de 17. Bulk input queues with quorum and multiple vacations Directory of Open Access Journals (Sweden) Dshalalow Jewgeni H. 1996-01-01 Full Text Available The authors study a single-server queueing system with bulk arrivals and batch service in accordance to the general quorum discipline: a batch taken for service is not less than r and not greater than R ( ≥ r . The server takes vacations each time the queue level falls below r ( ≥ 1 in accordance with the multiple vacation discipline. The input to the system is assumed to be a compound Poisson process. The analysis of the system is based on the theory of first excess processes developed by the first author. A preliminary analysis of such processes enabled the authors to obtain all major characteristics for the queueing process in an analytically tractable form. Some examples and applications are given. 18. Performance study of Active Queue Management methods: Adaptive GRED, REDD, and GRED-Linear analytical model Directory of Open Access Journals (Sweden) Hussein Abdel-jaber 2015-10-01 Full Text Available Congestion control is one of the hot research topics that helps maintain the performance of computer networks. This paper compares three Active Queue Management (AQM methods, namely, Adaptive Gentle Random Early Detection (Adaptive GRED, Random Early Dynamic Detection (REDD, and GRED Linear analytical model with respect to different performance measures. Adaptive GRED and REDD are implemented based on simulation, whereas GRED Linear is implemented as a discrete-time analytical model. Several performance measures are used to evaluate the effectiveness of the compared methods mainly mean queue length, throughput, average queueing delay, overflow packet loss probability, and packet dropping probability. The ultimate aim is to identify the method that offers the highest satisfactory performance in non-congestion or congestion scenarios. The first comparison results that are based on different packet arrival probability values show that GRED Linear provides better mean queue length; average queueing delay and packet overflow probability than Adaptive GRED and REDD methods in the presence of congestion. Further and using the same evaluation measures, Adaptive GRED offers a more satisfactory performance than REDD when heavy congestion is present. When the finite capacity of queue values varies the GRED Linear model provides the highest satisfactory performance with reference to mean queue length and average queueing delay and all the compared methods provide similar throughput performance. However, when the finite capacity value is large, the compared methods have similar results in regard to probabilities of both packet overflowing and packet dropping. 19. Study on the Queue-Length Distribution in Geo/G(MWV/1/N Queue with Working Vacations Directory of Open Access Journals (Sweden) Chuanyi Luo 2015-01-01 Full Text Available This paper analyzes a finite buffer size discrete-time Geo/G/1/N queue with multiple working vacations and different input rate. Using supplementary variable technique and embedded Markov chain method, the queue-length distribution solution in the form of formula at arbitrary epoch is obtained. Some performance measures associated with operating cost are also discussed based on the obtained queue-length distribution. Then, several numerical experiments follow to demonstrate the effectiveness of the obtained formulae. Finally, a state-dependent operating cost function is constructed to model an express logistics service center. Regarding the service rate during working vacation as a control variable, the optimization analysis on the cost function is carried out by using parabolic method. 20. Queue Length and Server Content Distribution in an Infinite-Buffer Batch-Service Queue with Batch-Size-Dependent Service Directory of Open Access Journals (Sweden) U. C. Gupta 2015-01-01 Full Text Available We analyze an infinite-buffer batch-size-dependent batch-service queue with Poisson arrival and arbitrarily distributed service time. Using supplementary variable technique, we derive a bivariate probability generating function from which the joint distribution of queue and server content at departure epoch of a batch is extracted and presented in terms of roots of the characteristic equation. We also obtain the joint distribution of queue and server content at arbitrary epoch. Finally, the utility of analytical results is demonstrated by the inclusion of some numerical examples which also includes the investigation of multiple zeros. 1. Dynamic server assignment in a two-queue model NARCIS (Netherlands) O.J. Boxma (Onno); D.G. Down 1995-01-01 textabstractWe consider a polling model of two$M/G/1$queues, served by a single server. The service policy for this polling model is of threshold type. Service at queue 1 is exhaustive. Service at queue 2 is exhaustive unless the size of queue 1 reaches some level$T$during a service at queue 2; 2. Dynamic server assignment in a two-queue model NARCIS (Netherlands) Boxma, O.J.; Down, D.G. 1997-01-01 We consider a polling model of two M/G/1 queues, served by a single server. The service policy for this polling model is of threshold type. Service at queue 1 is exhaustive. Service at queue 2 is exhaustive unless the size of queue 1 reaches some level T during a service at queue 2; in the latter 3. On the control of queueing systems with aging state information NARCIS (Netherlands) Onderwater, M.; Bhulai, S.; van der Mei, R.D. 2015-01-01 We investigate control of a queueing system in which a component of the state space is subject to aging. The controller can choose to forward incoming queries to the system (where it needs time for processing), or respond with a previously generated response (incurring a penalty for not providing a 4. Customer-oriented finite perturbation analysis for queueing networks NARCIS (Netherlands) Heidergott, B.F. 2000-01-01 We consider queueing networks for which the performance measureJ ( ) depends on a parameter , which can be a service time parameter or a buffer size, and we are interested in sensitivity analysis of J ( ) with respect to . We introduce a new method, called customer-oriented finite perturbation 5. Empirical Analysis of Priority on a FCFS Queue Discipline In ... African Journals Online (AJOL) Queues are virtually unavoidable phenomenon in Nigerian banking system. While banks stride to meet customers services' satisfaction, customers who do not go immediately into service must wait in line (if any). The queuing discipline in banks has been first-come-first-served (FCFS). What happen to the waiting time ... 6. Transient error approximation in a Lévy queue NARCIS (Netherlands) Mathijsen, B.; Zwart, A.P. 2017-01-01 Motivated by a capacity allocation problem within a finite planning period, we conduct a transient analysis of a single-server queue with Lévy input. From a cost minimization perspective, we investigate the error induced by using stationary congestion measures as opposed to time-dependent measures. 7. Integrated service resource reservation using queueing networks theory DEFF Research Database (Denmark) Brewka, Lukasz Jerzy; Iversen, Villy Bæk; Kardaras, Georgios 2014-01-01 This study analyses multi-server multi-service queueing networks with service protection. To guarantee each service a certain quality-of-service and at the same time ensure high utilisation of servers, a minimum capacity is reserved each service. In addition, all services share the remaining non... 8. Adaptive Mean Queue Size and Its Rate of Change: Queue Management with Random Dropping OpenAIRE Karmeshu; Patel, Sanjeev; Bhatnagar, Shalabh 2016-01-01 The Random early detection (RED) active queue management (AQM) scheme uses the average queue size to calculate the dropping probability in terms of minimum and maximum thresholds. The effect of heavy load enhances the frequency of crossing the maximum threshold value resulting in frequent dropping of the packets. An adaptive queue management with random dropping (AQMRD) algorithm is proposed which incorporates information not just about the average queue size but also the rate of change of th... 9. Departure Queue Prediction for Strategic and Tactical Surface Scheduler Integration Science.gov (United States) Zelinski, Shannon; Windhorst, Robert 2016-01-01 A departure metering concept to be demonstrated at Charlotte Douglas International Airport (CLT) will integrate strategic and tactical surface scheduling components to enable the respective collaborative decision making and improved efficiency benefits these two methods of scheduling provide. This study analyzes the effect of tactical scheduling on strategic scheduler predictability. Strategic queue predictions and target gate pushback times to achieve a desired queue length are compared between fast time simulations of CLT surface operations with and without tactical scheduling. The use of variable departure rates as a strategic scheduler input was shown to substantially improve queue predictions over static departure rates. With target queue length calibration, the strategic scheduler can be tuned to produce average delays within one minute of the tactical scheduler. However, root mean square differences between strategic and tactical delays were between 12 and 15 minutes due to the different methods the strategic and tactical schedulers use to predict takeoff times and generate gate pushback clearances. This demonstrates how difficult it is for the strategic scheduler to predict tactical scheduler assigned gate delays on an individual flight basis as the tactical scheduler adjusts departure sequence to accommodate arrival interactions. Strategic/tactical scheduler compatibility may be improved by providing more arrival information to the strategic scheduler and stabilizing tactical scheduler changes to runway sequence in response to arrivals. 10. Delay in a tandem queueing model with mobile queues: An analytical approximation NARCIS (Netherlands) Al Hanbali, Ahmad; de Haan, Roland; Boucherie, Richardus J.; van Ommeren, Jan C.W. In this paper, we analyze the end-to-end delay performance of a tandem queueing system with mobile queues. Due to state-space explosion, there is no hope for a numerical exact analysis for the joint-queue-length distribution. For this reason, we present an analytical approximation that is based on 11. Theoretical information measurement in nonrelativistic time-dependent approach Science.gov (United States) Najafizade, S. A.; Hassanabadi, H.; Zarrinkamar, S. 2018-02-01 The information-theoretic measures of time-dependent Schrödinger equation are investigated via the Shannon information entropy, variance and local Fisher quantities. In our calculations, we consider the two first states n = 0,1 and obtain the position Sx (t) and momentum Sp (t) Shannon entropies as well as Fisher information Ix (t) in position and momentum Ip (t) spaces. Using the Fourier transformed wave function, we obtain the results in momentum space. Some interesting features of the information entropy densities ρs (x,t) and γs (p,t), as well as the probability densities ρ (x,t) and γ (p,t) for time-dependent states are demonstrated. We establish a general relation between variance and Fisher's information. The Bialynicki-Birula-Mycielski inequality is tested and verified for the states n = 0,1. 12. The Supermarket Model with Bounded Queue Lengths in Equilibrium Science.gov (United States) Brightwell, Graham; Fairthorne, Marianne; Luczak, Malwina J. 2018-04-01 In the supermarket model, there are n queues, each with a single server. Customers arrive in a Poisson process with arrival rate λ n , where λ = λ (n) \\in (0,1) . Upon arrival, a customer selects d=d(n) servers uniformly at random, and joins the queue of a least-loaded server amongst those chosen. Service times are independent exponentially distributed random variables with mean 1. In this paper, we analyse the behaviour of the supermarket model in the regime where λ (n) = 1 - n^{-α } and d(n) = \\lfloor n^β \\rfloor , where α and β are fixed numbers in (0, 1]. For suitable pairs (α , β ) , our results imply that, in equilibrium, with probability tending to 1 as n → ∞, the proportion of queues with length equal to k = \\lceil α /β \\rceil is at least 1-2n^{-α + (k-1)β } , and there are no longer queues. We further show that the process is rapidly mixing when started in a good state, and give bounds on the speed of mixing for more general initial conditions. 13. Strategies for a centralized single product multiclass M/G/1 make-to-stock queue OpenAIRE Abouee-Mehrizi, Hossein; Balcıoğlu, Ahmet Barış; Balcioglu, Ahmet Baris; Baron, Opher 2012-01-01 Make-to-stock queues are typically investigated in the M/M/1 settings. For centralized single-item systems with backlogs, the multilevel rationing (MR) policy is established as optimal and the strict priority (SP) policy is a practical compromise, balancing cost and ease of implementation. However, the optimal policy is unknown when service time is general, i.e., for M/G/1 queues. Dynamic programming, the tool commonly used to investigate the MR policy in make-to-stock queues, is less practic... 14. A Taylor Series Approach for Service-Coupled Queueing Systems with Intermediate Load Directory of Open Access Journals (Sweden) Ekaterina Evdokimova 2017-01-01 Full Text Available This paper investigates the performance of a queueing model with multiple finite queues and a single server. Departures from the queues are synchronised or coupled which means that a service completion leads to a departure in every queue and that service is temporarily interrupted whenever any of the queues is empty. We focus on the numerical analysis of this queueing model in a Markovian setting: the arrivals in the different queues constitute Poisson processes and the service times are exponentially distributed. Taking into account the state space explosion problem associated with multidimensional Markov processes, we calculate the terms in the series expansion in the service rate of the stationary distribution of the Markov chain as well as various performance measures when the system is (i overloaded and (ii under intermediate load. Our numerical results reveal that, by calculating the series expansions of performance measures around a few service rates, we get accurate estimates of various performance measures once the load is above 40% to 50%. 15. GPS queues with heterogeneous traffic classes NARCIS (Netherlands) Borst, Sem; Mandjes, M.R.H.; van Uitert, Miranda 2002-01-01 We consider a queue fed by a mixture of light-tailed and heavy-tailed traffic. The two traffic classes are served in accordance with the generalized processor sharing (GPS) discipline. GPS-based scheduling algorithms, such as weighted fair queueing (WFQ), have emerged as an important mechanism for 16. Analysis of the asymmetric shortest queue problem NARCIS (Netherlands) Adan, I.J.B.F.; Wessels, J.; Zijm, W. H M 1991-01-01 In this paper we study a system consisting of two parallel servers with different service rates. Jobs arrive according to a Poisson stream and generate an exponentially distributed workload. On arrival a job joins the shortest queue and in case both queues have equal lengths, he joins the first 17. The WIYN Queue: Theory Meets Reality Science.gov (United States) Boroson, T. A.; Harmer, D. L.; Saha, A.; Smith, P. S.; Willmarth, D. W.; Silva, D. R. 1998-07-01 During the past two years NOAO has conducted a queue observing experiment with the 3.5 m WIYN telescope on Kitt Peak, Arizona. The WIYN telescope is ideally suited to queue-scheduled operation in terms of its performance and its instrument complement. The queue scheduling experiment on WIYN was designed to test a number of beliefs and hypotheses about gains in efficiency and scientific effectiveness due to queue scheduling. In addition, the experiment was a test of our implementation strategy and management of community expectations. The queue is run according, to a set of rules that guide decisions about which observation to do next. In practice, scientific rank, suitability of current conditions, and the desire to complete programs all enter into these decisions. As predicted by Monte Carlo simulations, the queue increases the overall efficiency of the telescope, particularly for observations requiring, rare conditions. Together with this improvement for typical programs, the queue enables synoptic, target-of-opportunity, and short programs that could not be scheduled classically. Despite this success, a number of sociological issues determine the community's perception of the WIYN queue. 18. Tandem queue with server slow-down NARCIS (Netherlands) Miretskiy, D.I.; Scheinhardt, W.R.W.; Mandjes, M.R.H. 2007-01-01 We study how rare events happen in the standard two-node tandem Jackson queue and in a generalization, the socalled slow-down network, see [2]. In the latter model the service rate of the first server depends on the number of jobs in the second queue: the first server slows down if the amount of 19. Analysis of the asymmetric shortest queue problem NARCIS (Netherlands) Adan, I.J.B.F.; Wessels, J.; Zijm, W.H.M. 1990-01-01 In this paper we study a system consisting of two parallel servers with different service rates. Jobs arrive according to a Poisson stream and generate an exponentially distributed workload. On arrival a job joins the shortest queue and in case both queues have equal lengths, he joins the first 20. On the dependence structure of Gaussian queues NARCIS (Netherlands) Es-Saghouani, A.; Mandjes, M.R.H. 2009-01-01 In this article we study Gaussian queues (that is, queues fed by Gaussian processes, such as fractional Brownian motion (fBm) and the integrated Ornstein-Uhlenbeck (iOU) process), with a focus on the dependence structure of the workload process. The main question is to what extent does the workload 1. Queues and Lévy Fluctuation Theory NARCIS (Netherlands) Dębicki, K.; Mandjes, M. 2015-01-01 The book provides an extensive introduction to queueing models driven by Lévy-processes as well as a systematic account of the literature on Lévy-driven queues. The objective is to make the reader familiar with the wide set of probabilistic techniques that have been developed over the past decades, 2. Survey on queueing models with standbys support Directory of Open Access Journals (Sweden) Kolledath Sreekanth 2018-01-01 Full Text Available This paper is a survey article on queueing models with standbys support. Due to many real life applications of queueing models, it has become an interesting area for researchers and a lot of research work has been exerted so far. It is worthwhile to examine the performance based analysis for queueing modelling system as it provides a valuable insight to the tractability of the system and accelerates its efficiency. The provision of standbys to the queueing modelling of a real system is needed for smooth functioning in the presence of its unavoidable failures. The present survey provides a dig into the research work done, and emphasis the sequential developments on queueing models with standbys support. 3. Notes on economic time series analysis system theoretic perspectives CERN Document Server Aoki, Masanao 1983-01-01 In seminars and graduate level courses I have had several opportunities to discuss modeling and analysis of time series with economists and economic graduate students during the past several years. These experiences made me aware of a gap between what economic graduate students are taught about vector-valued time series and what is available in recent system literature. Wishing to fill or narrow the gap that I suspect is more widely spread than my personal experiences indicate, I have written these notes to augment and reor­ ganize materials I have given in these courses and seminars. I have endeavored to present, in as much a self-contained way as practicable, a body of results and techniques in system theory that I judge to be relevant and useful to economists interested in using time series in their research. I have essentially acted as an intermediary and interpreter of system theoretic results and perspectives in time series by filtering out non-essential details, and presenting coherent accounts of wha... 4. Study on the Calculation Models of Bus Delay at Bays Using Queueing Theory and Markov Chain Directory of Open Access Journals (Sweden) Feng Sun 2015-01-01 Full Text Available Traffic congestion at bus bays has decreased the service efficiency of public transit seriously in China, so it is crucial to systematically study its theory and methods. However, the existing studies lack theoretical model on computing efficiency. Therefore, the calculation models of bus delay at bays are studied. Firstly, the process that buses are delayed at bays is analyzed, and it was found that the delay can be divided into entering delay and exiting delay. Secondly, the queueing models of bus bays are formed, and the equilibrium distribution functions are proposed by applying the embedded Markov chain to the traditional model of queuing theory in the steady state; then the calculation models of entering delay are derived at bays. Thirdly, the exiting delay is studied by using the queueing theory and the gap acceptance theory. Finally, the proposed models are validated using field-measured data, and then the influencing factors are discussed. With these models the delay is easily assessed knowing the characteristics of the dwell time distribution and traffic volume at the curb lane in different locations and different periods. It can provide basis for the efficiency evaluation of bus bays. 5. On applications of excess level processes to (N,D-policy bulk queueing systems Directory of Open Access Journals (Sweden) Jewgeni H. Dshalalow 1996-01-01 Full Text Available The paper deals with queueing systems in which N- and D-policies are combined into one. This means that an idle or vacationing server will resume his service if the queueing or workload process crosses some specified fixed level N or D, respectively. For the proposed (N,D-policy we study the queueing processes in models with and without server vacations, with compound Poisson input, and with generally distributed service and vacation periods. The analysis of the models is essentially based on fluctuation techniques for two-dimensional marked counting processes newly developed by the author. The results enable us to arrive at stationary distributions for the embedded and continuous time parameter queueing processes in closed analytic forms, enhancing the well-known Kendall formulas and their modifications. 6. The asymptotic variance of departures in critically loaded queues NARCIS (Netherlands) Al Hanbali, Ahmad; Mandjes, M.R.H.; Nazarathy, Y.; Whitt, W. 2011-01-01 We consider the asymptotic variance of the departure counting process D(t) of the GI/G/1 queue; D(t) denotes the number of departures up to time t. We focus on the case where the system load ϱ equals 1, and prove that the asymptotic variance rate satisfies limt→∞varD(t) / t = λ(1 - 2 / π)(ca2 + 7. Mathematical adventures in performance analysis from storage systems, through airplane boarding, to express line queues CERN Document Server Bachmat, Eitan 2014-01-01 This monograph describes problems in the field of performance analysis, primarily the study of storage systems and the diverse mathematical techniques that are required for solving such problems. Topics covered include best practices for scheduling I/O requests to a disk drive, how this problem is related to airplane boarding, and how both problems can be modeled using space-time geometry. The author also explains how Riemann's proof of the analytic continuation and functional equation of the Riemann zeta function can be used to analyze express-line queues in a minimarket. Overall, the book reveals the surprising applicability of abstract mathematical ideas that are not usually associated with applied topics. Advanced undergraduate students or graduate students with an interest in the applications of mathematics will find this book a useful resource. It will also be of interest to professional mathematicians who want exposure to the surprising ways that theoretical mathematics may be applied to engineering pr... 8. THEORETICAL EVOLUTION OF OPTICAL STRONG LINES ACROSS COSMIC TIME Energy Technology Data Exchange (ETDEWEB) Kewley, Lisa J.; Dopita, Michael A.; Sutherland, Ralph [Research School for Astronomy and Astrophysics, Mount Stromlo Observatory, Cotter Road, Weston, ACT 2611 (Australia); Leitherer, Claus [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Dave, Romeel [Department of Astronomy/Steward Observatory, 933 North Cherry Avenue, Tucson, AZ 85721-0065 (United States); Yuan, Tiantian [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Allen, Mark [Observatoire de Strasbourg, UMR 7550, Strasbourg 67000 (France); Groves, Brent, E-mail: kewley@mso.anu.edu.au [Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, D-69117 Heidelberg (Germany) 2013-09-10 We use the chemical evolution predictions of cosmological hydrodynamic simulations with our latest theoretical stellar population synthesis, photoionization, and shock models to predict the strong line evolution of ensembles of galaxies from z = 3 to the present day. In this paper, we focus on the brightest optical emission-line ratios, [N II]/H{alpha} and [O III]/H{beta}. We use the optical diagnostic Baldwin-Phillips-Terlevich (BPT) diagram as a tool for investigating the spectral properties of ensembles of active galaxies. We use four redshift windows chosen to exploit new near-infrared multi-object spectrographs. We predict how the BPT diagram will appear in these four redshift windows given different sets of assumptions. We show that the position of star-forming galaxies on the BPT diagram traces the interstellar medium conditions and radiation field in galaxies at a given redshift. Galaxies containing active galactic nucleus (AGN) form a mixing sequence with purely star-forming galaxies. This mixing sequence may change dramatically with cosmic time, due to the metallicity sensitivity of the optical emission-lines. Furthermore, the position of the mixing sequence may probe metallicity gradients in galaxies as a function of redshift, depending on the size of the AGN narrow-line region. We apply our latest slow shock models for gas shocked by galactic-scale winds. We show that at high redshift, galactic wind shocks are clearly separated from AGN in line ratio space. Instead, shocks from galactic winds mimic high metallicity starburst galaxies. We discuss our models in the context of future large near-infrared spectroscopic surveys. 9. Queues and Lévy fluctuation theory CERN Document Server Dębicki, Krzysztof 2015-01-01 The book provides an extensive introduction to queueing models driven by Lévy-processes as well as a systematic account of the literature on Lévy-driven queues. The objective is to make the reader familiar with the wide set of probabilistic techniques that have been developed over the past decades, including transform-based techniques, martingales, rate-conservation arguments, change-of-measure, importance sampling, and large deviations. On the application side, it demonstrates how Lévy traffic models arise when modelling current queueing-type systems (as communication networks) and includes applications to finance. Queues and Lévy Fluctuation Theory will appeal to graduate/postgraduate students and researchers in mathematics, computer science, and electrical engineering. Basic prerequisites are probability theory and stochastic processes. 10. Exclusive queueing model including the choice of service windows Science.gov (United States) Tanaka, Masahiro; Yanagisawa, Daichi; Nishinari, Katsuhiro 2018-01-01 In a queueing system involving multiple service windows, choice behavior is a significant concern. This paper incorporates the choice of service windows into a queueing model with a floor represented by discrete cells. We contrived a logit-based choice algorithm for agents considering the numbers of agents and the distances to all service windows. Simulations were conducted with various parameters of agent choice preference for these two elements and for different floor configurations, including the floor length and the number of service windows. We investigated the model from the viewpoint of transit times and entrance block rates. The influences of the parameters on these factors were surveyed in detail and we determined that there are optimum floor lengths that minimize the transit times. In addition, we observed that the transit times were determined almost entirely by the entrance block rates. The results of the presented model are relevant to understanding queueing systems including the choice of service windows and can be employed to optimize facility design and floor management. 11. Pricing Analysis in Geo/Geo/1 Queueing System Directory of Open Access Journals (Sweden) Yan Ma 2015-01-01 Full Text Available This paper studies the equilibrium behavior of customers and optimal pricing strategies of servers in a Geo/Geo/1 queueing system. Two common pricing mechanisms are considered. The first one is called ex-post payment (EPP scheme where the server collects tolls proportional to queue times, and the second one is called ex-ante payment (EAP scheme where the server charges a flat fee for the total service. The server sets the toll price to maximize its own profit. It is found that, under a customer’s choice equilibrium, the two toll mechanisms are equivalent from the economic point of view. Finally, we present several numerical experiments to investigate the effects of system parameters on the equilibrium customer joining rate and servers’ profits. 12. Preventing messaging queue deadlocks in a DMA environment Science.gov (United States) Blocksome, Michael A; Chen, Dong; Gooding, Thomas; Heidelberger, Philip; Parker, Jeff 2014-01-14 Embodiments of the invention may be used to manage message queues in a parallel computing environment to prevent message queue deadlock. A direct memory access controller of a compute node may determine when a messaging queue is full. In response, the DMA may generate and interrupt. An interrupt handler may stop the DMA and swap all descriptors from the full messaging queue into a larger queue (or enlarge the original queue). The interrupt handler then restarts the DMA. Alternatively, the interrupt handler stops the DMA, allocates a memory block to hold queue data, and then moves descriptors from the full messaging queue into the allocated memory block. The interrupt handler then restarts the DMA. During a normal messaging advance cycle, a messaging manager attempts to inject the descriptors in the memory block into other messaging queues until the descriptors have all been processed. 13. Queueing network model for obstetric patient flow in a hospital. Science.gov (United States) Takagi, Hideaki; Kanai, Yuta; Misue, Kazuo 2016-03-03 A queueing network is used to model the flow of patients in a hospital using the observed admission rate of patients and the histogram for the length of stay for patients in each ward. A complete log of orders for every movement of all patients from room to room covering two years was provided to us by the Medical Information Department of the University of Tsukuba Hospital in Japan. We focused on obstetric patients, who are generally hospitalized at random times throughout the year, and we analyzed the patient flow probabilistically. On admission, each obstetric patient is assigned to a bed in one of the two wards: one for normal delivery and the other for high-risk delivery. Then, the patient may be transferred between the two wards before discharge. We confirm Little's law of queueing theory for the patient flow in each ward. Next, we propose a new network model of M/G/ ∞ and M/M/ m queues to represent the flow of these patients, which is used to predict the probability distribution for the number of patients staying in each ward at the nightly census time. Although our model is a very rough and simplistic approximation of the real patient flow, the predicted probability distribution shows good agreement with the observed data. The proposed method can be used for capacity planning of hospital wards to predict future patient load in each ward. 14. The WorkQueue project - a task queue for the CMS workload management system Science.gov (United States) Ryu, S.; Wakefield, S. 2012-12-01 We present the development and first experience of a new component (termed WorkQueue) in the CMS workload management system. This component provides a link between a global request system (Request Manager) and agents (WMAgents) which process requests at compute and storage resources (known as sites). These requests typically consist of creation or processing of a data sample (possibly terabytes in size). Unlike the standard concept of a task queue, the WorkQueue does not contain fully resolved work units (known typically as jobs in HEP). This would require the WorkQueue to run computationally heavy algorithms that are better suited to run in the WMAgents. Instead the request specifies an algorithm that the WorkQueue uses to split the request into reasonable size chunks (known as elements). An advantage of performing lazy evaluation of an element is that expanding datasets can be accommodated by having job details resolved as late as possible. The WorkQueue architecture consists of a global WorkQueue which obtains requests from the request system, expands them and forms an element ordering based on the request priority. Each WMAgent contains a local WorkQueue which buffers work close to the agent, this overcomes temporary unavailability of the global WorkQueue and reduces latency for an agent to begin processing. Elements are pulled from the global WorkQueue to the local WorkQueue and into the WMAgent based on the estimate of the amount of work within the element and the resources available to the agent. WorkQueue is based on CouchDB, a document oriented NoSQL database. The WorkQueue uses the features of CouchDB (map/reduce views and bi-directional replication between distributed instances) to provide a scalable distributed system for managing large queues of work. The project described here represents an improvement over the old approach to workload management in CMS which involved individual operators feeding requests into agents. This new approach allows for a 15. The WorkQueue project - a task queue for the CMS workload management system International Nuclear Information System (INIS) Ryu, S; Wakefield, S 2012-01-01 We present the development and first experience of a new component (termed WorkQueue) in the CMS workload management system. This component provides a link between a global request system (Request Manager) and agents (WMAgents) which process requests at compute and storage resources (known as sites). These requests typically consist of creation or processing of a data sample (possibly terabytes in size). Unlike the standard concept of a task queue, the WorkQueue does not contain fully resolved work units (known typically as jobs in HEP). This would require the WorkQueue to run computationally heavy algorithms that are better suited to run in the WMAgents. Instead the request specifies an algorithm that the WorkQueue uses to split the request into reasonable size chunks (known as elements). An advantage of performing lazy evaluation of an element is that expanding datasets can be accommodated by having job details resolved as late as possible. The WorkQueue architecture consists of a global WorkQueue which obtains requests from the request system, expands them and forms an element ordering based on the request priority. Each WMAgent contains a local WorkQueue which buffers work close to the agent, this overcomes temporary unavailability of the global WorkQueue and reduces latency for an agent to begin processing. Elements are pulled from the global WorkQueue to the local WorkQueue and into the WMAgent based on the estimate of the amount of work within the element and the resources available to the agent. WorkQueue is based on CouchDB, a document oriented NoSQL database. The WorkQueue uses the features of CouchDB (map/reduce views and bi-directional replication between distributed instances) to provide a scalable distributed system for managing large queues of work. The project described here represents an improvement over the old approach to workload management in CMS which involved individual operators feeding requests into agents. This new approach allows for a 16. The WorkQueue project: A task queue for the CMS workload management system Energy Technology Data Exchange (ETDEWEB) Ryu, S. [Fermilab; Wakefield, Stuart [Imperial Coll., London 2012-01-01 We present the development and first experience of a new component (termed WorkQueue) in the CMS workload management system. This component provides a link between a global request system (Request Manager) and agents (WMAgents) which process requests at compute and storage resources (known as sites). These requests typically consist of creation or processing of a data sample (possibly terabytes in size). Unlike the standard concept of a task queue, the WorkQueue does not contain fully resolved work units (known typically as jobs in HEP). This would require the WorkQueue to run computationally heavy algorithms that are better suited to run in the WMAgents. Instead the request specifies an algorithm that the WorkQueue uses to split the request into reasonable size chunks (known as elements). An advantage of performing lazy evaluation of an element is that expanding datasets can be accommodated by having job details resolved as late as possible. The WorkQueue architecture consists of a global WorkQueue which obtains requests from the request system, expands them and forms an element ordering based on the request priority. Each WMAgent contains a local WorkQueue which buffers work close to the agent, this overcomes temporary unavailability of the global WorkQueue and reduces latency for an agent to begin processing. Elements are pulled from the global WorkQueue to the local WorkQueue and into the WMAgent based on the estimate of the amount of work within the element and the resources available to the agent. WorkQueue is based on CouchDB, a document oriented NoSQL database. The WorkQueue uses the features of CouchDB (map/reduce views and bi-directional replication between distributed instances) to provide a scalable distributed system for managing large queues of work. The project described here represents an improvement over the old approach to workload management in CMS which involved individual operators feeding requests into agents. This new approach allows for a 17. Queueing models for token and slotted ring networks. Thesis Science.gov (United States) Peden, Jeffery H. 1990-01-01 Currently the end-to-end delay characteristics of very high speed local area networks are not well understood. The transmission speed of computer networks is increasing, and local area networks especially are finding increasing use in real time systems. Ring networks operation is generally well understood for both token rings and slotted rings. There is, however, a severe lack of queueing models for high layer operation. There are several factors which contribute to the processing delay of a packet, as opposed to the transmission delay, e.g., packet priority, its length, the user load, the processor load, the use of priority preemption, the use of preemption at packet reception, the number of processors, the number of protocol processing layers, the speed of each processor, and queue length limitations. Currently existing medium access queueing models are extended by adding modeling techniques which will handle exhaustive limited service both with and without priority traffic, and modeling capabilities are extended into the upper layers of the OSI model. Some of the model are parameterized solution methods, since it is shown that certain models do not exist as parameterized solutions, but rather as solution methods. 18. Lack of sensitivity of staffing for 8-hour sessions to standard deviation in daily actual hours of operating room time used for surgeons with long queues. Science.gov (United States) Pandit, Jaideep J; Dexter, Franklin 2009-06-01 At multiple facilities including some in the United Kingdom's National Health Service, the following are features of many surgical-anesthetic teams: i) there is sufficient workload for each operating room (OR) list to almost always be fully scheduled; ii) the workdays are organized such that a single surgeon is assigned to each block of time (usually 8 h); iii) one team is assigned per block; and iv) hardly ever would a team "split" to do cases in more than one OR simultaneously. We used Monte-Carlo simulation using normal and Weibull distributions to estimate the times to complete lists of cases scheduled into such 8 h sessions. For each combination of mean and standard deviation, inefficiencies of use of OR time were determined for 10 h versus 8 h of staffing. When the mean actual hours of OR time used averages standard deviation and relative cost of over-run to under-run. When mean > or = 8 h 50 min, 10 h staffing has higher OR efficiency. For 8 h 25 min standard deviation of 60 min and relative cost of over-run to under-run of 2.0 versus (b) 8 h 48 min for normal, standard deviation of 0 min and relative cost ratio of 1.50. Although the simplest decision rule would be to staff for 8 h if the mean workload is standard deviation 60 min, and relative cost ratio of 2.00, the inefficiency of use of OR time would be 34% larger if staffing were planned for 8 h instead of 10 h. For surgical teams with 8 h sessions, use the following decision rule for anesthesiology and OR nurse staffing. If actual hours of OR time used averages or = 8 h 50 min, plan 10 h staffing. For averages in between, perform the full analysis of McIntosh et al. (Anesth Analg 2006;103:1499-516). 19. Operational behavior of the MAP/G/1 queue under N-policy with a single vacation and set-up Directory of Open Access Journals (Sweden) Ho Woo Lee 2002-01-01 Full Text Available This paper considers the MAP/G/1 queue under N-policy with a single vacation and set-up. We derive the vector generating functions of the queue length at an arbitrary time and at departures in decomposed forms. We also derive the Laplace-Stieltjes transform of the waiting time. Computation algorithms for mean performance measures are provided. 20. Cost Comparison of B-1B Non-Mission-Capable Drivers Using Finite Source Queueing with Spares Science.gov (United States) 2012-09-06 COMPARISON OF B-1B NON-MISSION-CAPABLE DRIVERS USING FINITE SOURCE QUEUEING WITH SPARES GRADUATE RESEARCH PAPER Presented to the Faculty...step into the lineup making large-number approximations unusable. Instead, a finite source queueing model including spares is incorporated...were reported as flying time accrued since last occurrence. Service time was given in both start-stop format and MX man-hours utilized. Service time was 1. Proposition of delay model for signalized intersections with queueing theory analytical models usage Directory of Open Access Journals (Sweden) Grzegorz SIERPIŃSKI 2007-01-01 Full Text Available Time delay on intersections is a very important transport problem. Thearticle includes a proposition of time delay model. Variance of service times is considered by used average waiting time in queue for queuing system with compressed queuing processes usage as a part of proposed time delays model. 2. Queueing in a spent fuel transportation system - preliminary analysis of implications for system design International Nuclear Information System (INIS) Cashwell, J.W.; Wood, T.W. 1985-01-01 Compliance with the Nuclear Waste Policy Act of 1982 (PL 97-425) will require the transportation of large volumes of spent fuel to a central receiving facility (either a geologic repository or a monitored retrievable storage facility). Decisions on the transport mode and technology will evolve over the next several years, in anticipation of the deployment of a receiving facility in the late 1990s. Regardless of the particular transportation mode or modes and the details of cask technology, the transport system from many diverse sources to a single point will generate an essentially random arrival pattern. This random arrival pattern will lead to the formation of queues at the receiving facility. As is normal in any queueing system, the waiting time distribution caused by this queueing will depend on the receiving facility input processing rate and the characteristics of the traffic. Since this is a cyclic system, there is also a reverse effect in which (for a given size cask fleet) average wait time affects traffic intensity. Both effects must be accounted for to properly represent the system. This paper develops a simple analytic queueing model which accounts for both of these effects simultaneously. Since both effects are determined by receiving facility input rates and cask fleet size and characteristics, two major sets of system design parameters are linked by the queueing process. The model is used with estimated traffic and service parameters to predict the severity of queueing under plausible reference system conditions, and to establish shadow prices for the trade off between larger cask fleets and more efficient receiving facilities. Since many of the parameter values used in this estimation are quite preliminary, these results are presented primarily in the context of demonstrating the utility of the queueing model for future trade off studies 3. Queueing in a spent fuel transportation system: a preliminary analysis of implications for system design International Nuclear Information System (INIS) Cashwell, J.W.; Wood, T.W. 1985-03-01 Compliance with the Nuclear Waste Policy Act of 1982 (PL 97-425) will require the transportation of large volumes of spent fuel to a central receiving facility (Either a geologic repository or a monitored retrievable storage facility). Decisions on the transport mode and technology will evolve over the next several years, in anticipation of the deployment of a receiving facility in the late 1990s. Regardless of the particular transportation mode or modes and the details of cask technology, the transport system from many diverse sources to a single point will generate an essentially random arrival pattern. This random arrival pattern will lead to the formation of queues at the receiving facility. As is normal in any queueing system, the waiting time distribution caused by this queueing will depend on the receiving facility input processing rate and the characteristics of the traffic. Since this is a cyclic system, there is also a reverse effect in which (for a given size cask fleet) average wait time affects traffic intensity. Both effects must be accounted for to properly represent the system. This paper develops a simple analytic queueing model which accounts for both of these effects simultaneously. Since both effects are determined by receiving facility input and cask fleet size characteristics, two major sets of system design parameters are linked by the queueing process. The model is used with estimated traffic and service parameters to predict the severity of queueing under plausible reference system conditions, and to establish ''shadow prices'' for the trade off between larger cask fleets and more efficient receiving facilities. Since many of the parameter values used in this estimation are quite preliminary, these results are presented primarily in the context of demonstrating the utility of the queueing model for future trade off studies. 5 refs., 5 figs., 2 tabs 4. Performance optimization of queueing systems with perturbation realization KAUST Repository Xia, Li; Cao, Xiren 2012-01-01 After the intensive studies of queueing theory in the past decades, many excellent results in performance analysis have been obtained, and successful examples abound. However, exploring special features of queueing systems directly in performance 5. Computing moving and intermittent queue propagation in highway work zones. Science.gov (United States) 2012-07-01 Drivers may experience intermittent congestion and moving queue conditions in work zones due to several reasons such as presence of lane closure, roadway geometric changes, higher demand, lower speed, and reduced capacity. The congestion and queue ha... 6. Stochastic network optimization with application to communication and queueing systems CERN Document Server Neely, Michael 2010-01-01 This text presents a modern theory of analysis, control, and optimization for dynamic networks. Mathematical techniques of Lyapunov drift and Lyapunov optimization are developed and shown to enable constrained optimization of time averages in general stochastic systems. The focus is on communication and queueing systems, including wireless networks with time-varying channels, mobility, and randomly arriving traffic. A simple drift-plus-penalty framework is used to optimize time averages such as throughput, throughput-utility, power, and distortion. Explicit performance-delay tradeoffs are prov 7. Some reflections on the Renewal-theory paradox in queueing theory Directory of Open Access Journals (Sweden) Robert B. Cooper 1998-01-01 Full Text Available The classical renewal-theory (waiting time, or inspection paradox states that the length of the renewal interval that covers a randomly-selected time epoch tends to be longer than an ordinary renewal interval. This paradox manifests itself in numerous interesting ways in queueing theory, a prime example being the celebrated Pollaczek-Khintchine formula for the mean waiting time in the M/G/1 queue. In this expository paper, we give intuitive arguments that explain why the renewal-theory paradox is ubiquitous in queueing theory, and why it sometimes produces anomalous results. In particular, we use these intuitive arguments to explain decomposition in vacation models, and to derive formulas that describe some recently-discovered counterintuitive results for polling models, such as the reduction of waiting times as a consequence of forcing the server to set up even when no work is waiting. 8. Experiences of Fast Queue health care users in primary health care facilities in eThekwini district, South AfricaExperiences of Fast Queue health care users in primary health care facilities in eThekwini district, South Africa Directory of Open Access Journals (Sweden) Dudu G. Sokhela 2013-07-01 Full Text Available Background: Comprehensive Primary Health Care (PHC, based on the principles of accessibility, availability, affordability, equity and acceptability, was introduced in South Africa to address inequalities in health service provision. Whilst the Fast Queue was instrumental in the promotion of access to health care, a major goal of the PHC approach, facilities were not prepared for the sudden influx of clients. Increased access resulted in long waiting times and queues contributing to dissatisfaction with the service which could lead to missed appointments and non-compliance with established treatment plans.Objectives: Firstly to describe the experiences of clients using the Fast Queue strategy to access routine healthcare services and secondly, to determine how the clients’ experiences led to satisfaction or dissatisfaction with the Fast Queue service.Method: A descriptive qualitative survey using content analysis explored the experiences of the Fast Queue users in a PHC setting. Setting was first identified based on greatest number using the Fast Queue and geographic diversity and then a convenience sample of health care users of the Fast Queue were sampled individually along with one focus group of users who accessed the Queue monthly for medication refills. The same interview guide questions were used for both individual interviews and the one focus group discussion. Five clinics with the highest number of attendees during a three month period and a total of 83 health care users of the Fast Queue were interviewed. The average participant was female, 31 years old, single and unemployed.Results: Two themes with sub-themes emerged: health care user flow and communication, which highlights both satisfaction and dissatisfaction with the fast queue and queue marshals, could assist in directing users to the respective queues, reduce waiting time and keep users satisfied with the use of sign posts where there is a lack of human resources 9. Australia: a matter of Queues and As Energy Technology Data Exchange (ETDEWEB) NONE 2007-05-15 Australia has been very much in the news recently, with ship queues at port terminals and storms hitting the Hunter Valley, flooding coal yards and rail links. In December 2006 a 'capacity balancing system' (CBS) introduced by Port Waratah Coal Services to solve queuing problems in Newcastle ports in mid-2004 was discontinued but then the queues started to grow again. A new CBS was introduced and was beginning to take effect when storms struck New South Wales. Port Dalrymple Coal Services has a queue management system but nevertheless there were 58 ships waiting in Dalrymple Bay and Hay Point in late June. A number of coal terminals are undergoing expansion in an attempt to solve the situation. 4 photos. 10. Near-optimal switching strategies for a tandem queue NARCIS (Netherlands) van Leeuwen, D.; Núñez-Queija, R.; Boucherie, R.J.; van Dijk, N.M. 2017-01-01 Motivated by various applications in logistics, road traffic and production management, we investigate two versions of a tandem queueing model in which the service rate of the first queue can be controlled. The objective is to keep the mean number of jobs in the second queue as low as possible, 11. Near-optimal switching strategies for a tandem queue NARCIS (Netherlands) D. van Leeuwen (Daphne); R. Núñez Queija (Rudesindo) 2017-01-01 textabstractMotivated by various applications in logistics, road traffic and production management, we investigate two versions of a tandem queueing model in which the service rate of the first queue can be controlled. The objective is to keep the mean number of jobs in the second queue as low as 12. State-dependent importance sampling for a slowdown tandem queue NARCIS (Netherlands) Miretskiy, D.I.; Scheinhardt, W.R.W.; Mandjes, M.R.H. 2011-01-01 In this paper we investigate an advanced variant of the classical (Jackson) tandem queue, viz. a two-node system with server slowdown. By this mechanism, the service speed of the upstream queue is reduced as soon as the number of jobs in the downstream queue reaches some pre-specified threshold. We 13. Discovering queues from event logs with varying levels of information NARCIS (Netherlands) Senderovich, A.; Leemans, S,J.J.; Harel, S.; Gal, A.; Mandelbaum, A.; van der Aalst, W.M.P.; Reichert, M.; Reijers, H.A. 2016-01-01 Detecting and measuring resource queues is central to business process optimization. Queue mining techniques allow for the identification of bottlenecks and other process inefficiencies, based on event data. This work focuses on the discovery of resource queues. In particular, we investigate the 14. Difference and differential equations with applications in queueing theory CERN Document Server Haghighi, Aliakbar Montazer 2013-01-01 A Useful Guide to the Interrelated Areas of Differential Equations, Difference Equations, and Queueing Models Difference and Differential Equations with Applications in Queueing Theory presents the unique connections between the methods and applications of differential equations, difference equations, and Markovian queues. Featuring a comprehensive collection of 15. Matrix-Geometric Method for Queueing Model with State-Dependent Arrival of an Unreliable Server and PH Service Directory of Open Access Journals (Sweden) M.ReniSagaya Raj 2016-03-01 Full Text Available In this paper, we consider a state-dependent queueing system in which the system is subject to random breakdowns. Customer arrive at the system randomly following a Poisson process with state-dependent rates. Service times follows PH distribution and repair times are exponentially distributed. The server may fail to service with probability depending on the number of customer completed since the last repair. The main result of this paper is the matrix-geometric solution of the steady-state queue length from which many performance measurements of this queueing system like the stationary queue length distribution, waiting time distribution and the distribution of regular busy period, system utilization are obtained. Numerical examples are presented for both cases. 16. The Timing of Sleep in Depression : Theoretical Considerations NARCIS (Netherlands) Beersma, Domien G.M.; Daan, Serge; Hoofdakker, Rutger H. van den 1985-01-01 Endogenously depressed subjects frequently show severe sleep problems. In this article sleep time in depression is discussed in relation to a recently developed model for sleep timing in healthy subjects. In terms of the model, two parameter sets survive a qualitative comparison with the empirical 17. MX/G/1 unreliable retrial queue with option of additional service and Bernoulli vacation Directory of Open Access Journals (Sweden) Charan Jeet Singh 2016-03-01 Full Text Available In this paper, retrial queue with unreliable server and bulk arrivals is investigated. The server is capable of providing m-optional services and any one of these available services, may be rendered to the customer after the first essential service if the customer opts for the same. It is assumed that the server may fail while rendering any phase of service and undergoes for the immediate repair. After the completion of the service of a customer, the server may either take a vacation for a random period or may continue to provide the service to the other customers waiting in the queue. The supplementary variables corresponding to service time, repair time and retrial time are incorporated to determine the queue size distribution. To examine the effect of different parameters on the performance measures of the system, the numerical illustration is given which is supported by numerical simulation and sensitivity analysis. 18. Experiences of Fast Queue health care users in primary health care facilities in eThekwini district, South Africa. Science.gov (United States) Sokhela, Dudu G; Makhanya, Nonhlanhla J; Sibiya, Nokuthula M; Nokes, Kathleen M 2013-07-05 Comprehensive Primary Health Care (PHC), based on the principles of accessibility, availability, affordability, equity and acceptability, was introduced in South Africa to address inequalities in health service provision. Whilst the Fast Queue was instrumental in the promotion of access to health care, a major goal of the PHC approach, facilities were not prepared for the sudden influx of clients. Increased access resulted in long waiting times and queues contributing to dissatisfaction with the service which could lead to missed appointments and non-compliance with established treatment plans. Firstly to describe the experiences of clients using the Fast Queue strategy to access routine healthcare services and secondly, to determine how the clients' experiences led to satisfaction or dissatisfaction with the Fast Queue service. A descriptive qualitative survey using content analysis explored the experiences of the Fast Queue users in a PHC setting. Setting was first identified based on greatest number using the Fast Queue and geographic diversity and then a convenience sample of health care users of the Fast Queue were sampled individually along with one focus group of users who accessed the Queue monthly for medication refills. The same interview guide questions were used for both individual interviews and the one focus group discussion. Five clinics with the highest number of attendees during a three month period and a total of 83 health care users of the Fast Queue were interviewed. The average participant was female, 31 years old, single and unemployed. Two themes with sub-themes emerged: health care user flow and communication, which highlights both satisfaction and dissatisfaction with the fast queue and queue marshals, could assist in directing users to the respective queues, reduce waiting time and keep users satisfied with the use of sign posts where there is a lack of human resources. Effective health communication strategies contribute to positive 19. Experiences of Fast Queue health care users in primary health care facilities in eThekwini district, South Africa Directory of Open Access Journals (Sweden) Dudu G. Sokhela 2013-07-01 Full Text Available Background: Comprehensive Primary Health Care (PHC, based on the principles of accessibility, availability, affordability, equity and acceptability, was introduced in South Africa to address inequalities in health service provision. Whilst the Fast Queue was instrumental in the promotion of access to health care, a major goal of the PHC approach, facilities were not prepared for the sudden influx of clients. Increased access resulted in long waiting times and queues contributing to dissatisfaction with the service which could lead to missed appointments and non-compliance with established treatment plans. Objectives: Firstly to describe the experiences of clients using the Fast Queue strategy to access routine healthcare services and secondly, to determine how the clients’ experiences led to satisfaction or dissatisfaction with the Fast Queue service. Method: A descriptive qualitative survey using content analysis explored the experiences of the Fast Queue users in a PHC setting. Setting was first identified based on greatest number using the Fast Queue and geographic diversity and then a convenience sample of health care users of the Fast Queue were sampled individually along with one focus group of users who accessed the Queue monthly for medication refills. The same interview guide questions were used for both individual interviews and the one focus group discussion. Five clinics with the highest number of attendees during a three month period and a total of 83 health care users of the Fast Queue were interviewed. The average participant was female, 31 years old, single and unemployed. Results: Two themes with sub-themes emerged: health care user flow and communication, which highlights both satisfaction and dissatisfaction with the fast queue and queue marshals, could assist in directing users to the respective queues, reduce waiting time and keep users satisfied with the use of sign posts where there is a lack of human resources 20. THEORETICAL REVIEW The Hippocampus, Time, and Memory Across Scales Science.gov (United States) Howard, Marc W.; Eichenbaum, Howard 2014-01-01 A wealth of experimental studies with animals have offered insights about how neural networks within the hippocampus support the temporal organization of memories. These studies have revealed the existence of “time cells” that encode moments in time, much as the well-known “place cells” map locations in space. Another line of work inspired by human behavioral studies suggests that episodic memories are mediated by a state of temporal context that changes gradually over long time scales, up to at least a few thousand seconds. In this view, the “mental time travel” hypothesized to support the experience of episodic memory corresponds to a “jump back in time” in which a previous state of temporal context is recovered. We suggest that these 2 sets of findings could be different facets of a representation of temporal history that maintains a record at the last few thousand seconds of experience. The ability to represent long time scales comes at the cost of discarding precise information about when a stimulus was experienced—this uncertainty becomes greater for events further in the past. We review recent computational work that describes a mechanism that could construct such a scale-invariant representation. Taken as a whole, this suggests the hippocampus plays its role in multiple aspects of cognition by representing events embedded in a general spatiotemporal context. The representation of internal time can be useful across nonhippocampal memory systems. PMID:23915126 1. Interevent time distribution in seismicity: A theoretical approach International Nuclear Information System (INIS) Molchan, G. 2004-09-01 This paper presents an analysis of the distribution of the time τ between two consecutive events in a stationary point process. The study is motivated by the discovery of unified scaling laws for τ for the case of seismic events. We demonstrate that these laws cannot exist simultaneously in a seismogenic area. Under very natural assumptions we show that if, after resealing to ensure Eτ = 1, the interevent time has a universal distribution F, then F must be exponential. In other words, Corral's unified scaling law cannot exist in the whole range of time. In the framework of a general cluster model we discuss the parameterization of an empirical unified law and the physical meaning of the parameters involved 2. Handbook of Time Series Analysis Recent Theoretical Developments and Applications CERN Document Server Schelter, Björn; Timmer, Jens 2006-01-01 This handbook provides an up-to-date survey of current research topics and applications of time series analysis methods written by leading experts in their fields. It covers recent developments in univariate as well as bivariate and multivariate time series analysis techniques ranging from physics' to life sciences' applications. Each chapter comprises both methodological aspects and applications to real world complex systems, such as the human brain or Earth's climate. Covering an exceptionally broad spectrum of topics, beginners, experts and practitioners who seek to understand the latest de 3. Queueing-Based Synchronization and Entrainment for Synthetic Gene Oscillators Science.gov (United States) Mather, William; Butzin, Nicholas; Hochendoner, Philip; Ogle, Curtis Synthetic gene oscillators have been a major focus of synthetic biology research since the beginning of the field 15 years ago. They have proven to be useful both for biotechnological applications as well as a testing ground to significantly develop our understanding of the design principles behind synthetic and native gene oscillators. In particular, the principles governing synchronization and entrainment of biological oscillators have been explored using a synthetic biology approach. Our work combines experimental and theoretical approaches to specifically investigate how a bottleneck for protein degradation, which is present in most if not all existing synthetic oscillators, can be leveraged to robustly synchronize and entrain biological oscillators. We use both the terminology and mathematical tools of queueing theory to intuitively explain the role of this bottleneck in both synchronization and entrainment, which extends prior work demonstrating the usefulness of queueing theory in synthetic and native gene circuits. We conclude with an investigation of how synchronization and entrainment may be sensitive to the presence of multiple proteolytic pathways in a cell that couple weakly through crosstalk. This work was supported by NSF Grant #1330180. 4. A discrete single server queue with Markovian arrivals and phase type group services Directory of Open Access Journals (Sweden) Attahiru Sule Alfa 1995-01-01 Full Text Available We consider a single-server discrete queueing system in which arrivals occur according to a Markovian arrival process. Service is provided in groups of size no more than M customers. The service times are assumed to follow a discrete phase type distribution, whose representation may depend on the group size. Under a probabilistic service rule, which depends on the number of customers waiting in the queue, this system is studied as a Markov process. This type of queueing system is encountered in the operations of an automatic storage retrieval system. The steady-state probability vector is shown to be of (modified matrix-geometric type. Efficient algorithmic procedures for the computation of the rate matrix, steady-state probability vector, and some important system performance measures are developed. The steady-state waiting time distribution is derived explicitly. Some numerical examples are presented. 5. ANALYSIS OF FUZZY QUEUES: PARAMETRIC PROGRAMMING APPROACH BASED ON RANDOMNESS - FUZZINESS CONSISTENCY PRINCIPLE Directory of Open Access Journals (Sweden) Dhruba Das 2015-04-01 Full Text Available In this article, based on Zadeh’s extension principle we have apply the parametric programming approach to construct the membership functions of the performance measures when the interarrival time and the service time are fuzzy numbers based on the Baruah’s Randomness- Fuzziness Consistency Principle. The Randomness-Fuzziness Consistency Principle leads to defining a normal law of fuzziness using two different laws of randomness. In this article, two fuzzy queues FM/M/1 and M/FM/1 has been studied and constructed their membership functions of the system characteristics based on the aforesaid principle. The former represents a queue with fuzzy exponential arrivals and exponential service rate while the latter represents a queue with exponential arrival rate and fuzzy exponential service rate. 6. Transient probabilities for queues with applications to hospital waiting list management. Science.gov (United States) Joy, Mark; Jones, Simon 2005-08-01 In this paper we study queuing systems within the NHS. Recently imposed government performance targets lead NHS executives to investigate and instigate alternative management strategies, thereby imposing structural changes on the queues. Under such circumstances, it is most unlikely that such systems are in equilibrium. It is crucial, in our opinion, to recognise this state of affairs in order to make a balanced assessment of the role of queue management in the modern NHS. From a mathematical perspective it should be emphasised that measures of the state of a queue based upon the assumption of statistical equilibrium (a pervasive methodology in the study of queues) are simply wrong in the above scenario. To base strategic decisions around such ideas is therefore highly questionable and it is one of the purposes of this paper to offer alternatives: we present some (recent) research whose results generate performance measures and measures of risk, for example, of waiting-times growing unacceptably large; we emphasise that these results concern the transient behaviour of the queueing model-there is no asssumption of statistical equilibrium. We also demonstrate that our results are computationally tractable. 7. A queueing model for error control of partial buffer sharing in ATM Directory of Open Access Journals (Sweden) Ahn Boo Yong 1999-01-01 Full Text Available We model the error control of the partial buffer sharing of ATM by a queueing system M 1 , M 2 / G / 1 / K + 1 with threshold and instantaneous Bernoulli feedback. We first derive the system equations and develop a recursive method to compute the loss probabilities at an arbitrary time epoch. We then build an approximation scheme to compute the mean waiting time of each class of cells. An algorithm is developed for finding the optimal threshold and queue capacity for a given quality of service. 8. The Application of The Double Queue Asymmetric Gated Service Polling Control Theory in Intelligent Traffic System Directory of Open Access Journals (Sweden) Zhao Yi Fan 2016-01-01 Full Text Available paper presents a new use of double queues asymmetric gated service polling system in the intelligent traffic light control system.Usually there are more vehicles in main road than minor road,so there are more green light time be needed in the main road.From the computer simulation and theory analysis,we can find that the application of double queues asymmetric gated service polling theory in intelligent traffic system can balance intersections load and set suitable passing time for vehicles to assure the roads open. 9. Adaptive Filtering Queueing for Improving Fairness Directory of Open Access Journals (Sweden) Jui-Pin Yang 2015-06-01 Full Text Available In this paper, we propose a scalable and efficient Active Queue Management (AQM scheme to provide fair bandwidth sharing when traffic is congested dubbed Adaptive Filtering Queueing (AFQ. First, AFQ identifies the filtering level of an arriving packet by comparing it with a flow label selected at random from the first level to an estimated level in the filtering level table. Based on the accepted traffic estimation and the previous fair filtering level, AFQ updates the fair filtering level. Next, AFQ uses a simple packet-dropping algorithm to determine whether arriving packets are accepted or discarded. To enhance AFQ’s feasibility in high-speed networks, we propose a two-layer mapping mechanism to effectively simplify the packet comparison operations. Simulation results demonstrate that AFQ achieves optimal fairness when compared with Rotating Preference Queues (RPQ, Core-Stateless Fair Queueing (CSFQ, CHOose and Keep for responsive flows, CHOose and Kill for unresponsive flows (CHOKe and First-In First-Out (FIFO schemes under a variety of traffic conditions. 10. Dobrushin's approach to queueing network theory Directory of Open Access Journals (Sweden) F. I. Karpelevich 1996-01-01 Full Text Available R.L. Dobrushin (1929-1995 made substantial contributions to Queueing Network Theory (QNT. A review of results from QNT which arose from his ideas or were connected to him in other ways is given. We also comment on various related open problems. 11. An Evaluation of Concurrent Priority Queue Algorithms Science.gov (United States) 1991-02-01 path pronlem are testedi A! -S7 ?o An Evaluation of Concurrent Priority Queue Algorithms bv Qin Huang BS. Uiversity - of Science andi Technology of China...who have always supported me through my entire career and made my life more enjoyable. This research was supported in part by the Advanced Research 12. Open problems in Gaussian fluid queueing theory NARCIS (Netherlands) Dȩbicki, K.; Mandjes, M. 2011-01-01 We present three challenging open problems that originate from the analysis of the asymptotic behavior of Gaussian fluid queueing models. In particular, we address the problem of characterizing the correlation structure of the stationary buffer content process, the speed of convergence to 13. Labour costs and queueing theory in retailing NARCIS (Netherlands) J.B.G. Frenk (Hans); A.R. Thurik (Roy); C.A. Bout 1991-01-01 textabstractIn this paper approximation results for the M/G/s queueing model are used to derive an empirically verified shop type dependent non-homogeneous relation between labour volume and sales in retail trade. Moreover, we formulate the retailer's labour management as a formal minimization 14. Markov-modulated and feedback fluid queues NARCIS (Netherlands) Scheinhardt, Willem R.W. 1998-01-01 In the last twenty years the field of Markov-modulated fluid queues has received considerable attention. In these models a fluid reservoir receives and/or releases fluid at rates which depend on the actual state of a background Markov chain. In the first chapter of this thesis we give a short 15. Adaptive Importance Sampling Simulation of Queueing Networks NARCIS (Netherlands) de Boer, Pieter-Tjerk; Nicola, V.F.; Rubinstein, N.; Rubinstein, Reuven Y. 2000-01-01 In this paper, a method is presented for the efficient estimation of rare-event (overflow) probabilities in Jackson queueing networks using importance sampling. The method differs in two ways from methods discussed in most earlier literature: the change of measure is state-dependent, i.e., it is a 16. Optimal control of arrival and service rates in tandem queues International Nuclear Information System (INIS) Moustafa, M.S. 1995-08-01 We consider n M/M/1 queues in series. At queue one the arrival and service rates are chosen in pair from a finite set whenever there are arrivals or service completions at any queue. Customers arriving to queue L (L=1,2,...,n-1) must go on to queue L+1 after finishing service at server L. Customers arriving to queue n leave the system after finishing service at the last server. At queues 2 to n arrival and service rates are fixed. The objective is to minimize the expected discounted cost of the system over finite and infinite horizons. We show that the optimal policy is of threshold type. In order to establish the result, we formulate the optimal control problem as a Linear Programming. (author). 9 refs 17. Mathematical Analysis of Queue with Phase Service: An Overview Directory of Open Access Journals (Sweden) Richa Sharma 2014-01-01 Full Text Available We discuss various aspects of phase service queueing models. A large number of models have been developed in the area of queueing theory incorporating the concept of phase service. These phase service queueing models have been investigated for resolving the congestion problems of many day-to-day as well as industrial scenarios. In this survey paper, an attempt has been made to review the work done by the prominent researchers on the phase service queues and their applications in several realistic queueing situations. The methodology used by several researchers for solving various phase service queueing models has also been described. We have classified the related literature based on modeling and methodological concepts. The main objective of present paper is to provide relevant information to the system analysts, managers, and industry people who are interested in using queueing theory to model congestion problems wherein the phase type services are prevalent. 18. Space and Time as Relations: The Theoretical Approach of Leibniz Directory of Open Access Journals (Sweden) Basil Evangelidis 2018-04-01 Full Text Available The epistemological rupture of Copernicus, the laws of planetary motions of Kepler, the comprehensive physical observations of Galileo and Huygens, the conception of relativity, and the physical theory of Newton were components of an extremely fertile and influential cognitive environment that prompted the restless Leibniz to shape an innovative theory of space and time. This theory expressed some of the concerns and intuitions of the scientific community of the seventeenth century, in particular the scientific group of the Academy of Sciences of Paris, but remained relatively unknown until the twentieth century. After Einstein, however, the relational theory of Leibniz gained wider respect and fame. The aim of this article is to explain how Leibniz foresaw relativity, through his critique of contemporary mechanistic philosophy. 19. On a first passage problem in general queueing systems with multiple vacations Directory of Open Access Journals (Sweden) Jewgeni H. Dshalalow 1992-01-01 Full Text Available The author studies a generalized single-server queueing system with bulk arrivals and batch service, where the server takes vacations each time the queue level falls below r(≥1 in accordance with the multiple vacation discipline. The input to the system is assumed to be a compound Poisson process modulated by the system and the service is assumed to be state dependent. One of the essential part in the analysis of the system is the employment of new techniques related to the first excess level processes. A preliminary analysis of such processes and recent results of the author on modulated processes enabled the author to obtain all major characteristics for the queueing process explicitly. Various examples and applications are discussed. 20. On the optimal use of a slow server in two-stage queueing systems Science.gov (United States) Papachristos, Ioannis; Pandelis, Dimitrios G. 2017-07-01 We consider two-stage tandem queueing systems with a dedicated server in each queue and a slower flexible server that can attend both queues. We assume Poisson arrivals and exponential service times, and linear holding costs for jobs present in the system. We study the optimal dynamic assignment of servers to jobs assuming that two servers cannot collaborate to work on the same job and preemptions are not allowed. We formulate the problem as a Markov decision process and derive properties of the optimal allocation for the dedicated (fast) servers. Specifically, we show that the one downstream should not idle, and the same is true for the one upstream when holding costs are larger there. The optimal allocation of the slow server is investigated through extensive numerical experiments that lead to conjectures on the structure of the optimal policy. 1. A GA-based PID active queue management control design for TCP/IP networks Energy Technology Data Exchange (ETDEWEB) Kuo, H-H; Chen, C-K; Liao, T-L [Department of Engineering Science, National Cheng Kung University, Tainan 701, Taiwan (China); Yan, J-J [Department of Computer and Communication, Shu-Te University, Kaohsiung 824, Taiwan (China)], E-mail: tlliao@mail.ncku.edu.tw 2008-02-15 In this paper, a genetic algorithm-based (GA-based) proportional-integral-derivative (PID) controller as an active queue manager for Internet routers is proposed to reduce packet loss and improve network utilization in TCP/IP networks. Based on the window-based nonlinear dynamics, the TCP network was modeled as a time-delayed system with a saturated input due to the limitations of packet-dropping probability and the effects of propagation delays in TCP networks. An improved genetic algorithm is employed to derive optimal or near optimal PID control gains such that a performance index of integrated-absolute error (IAE) in terms of the error between the router queue length and the desired queue length is minimized. The performance of the proposed control scheme was evaluated in various network scenarios via a series of numerical simulations. The simulation results confirm that the proposed scheme outperforms other AQM schemes. 2. A GA-based PID active queue management control design for TCP/IP networks International Nuclear Information System (INIS) Kuo, H-H; Chen, C-K; Liao, T-L; Yan, J-J 2008-01-01 In this paper, a genetic algorithm-based (GA-based) proportional-integral-derivative (PID) controller as an active queue manager for Internet routers is proposed to reduce packet loss and improve network utilization in TCP/IP networks. Based on the window-based nonlinear dynamics, the TCP network was modeled as a time-delayed system with a saturated input due to the limitations of packet-dropping probability and the effects of propagation delays in TCP networks. An improved genetic algorithm is employed to derive optimal or near optimal PID control gains such that a performance index of integrated-absolute error (IAE) in terms of the error between the router queue length and the desired queue length is minimized. The performance of the proposed control scheme was evaluated in various network scenarios via a series of numerical simulations. The simulation results confirm that the proposed scheme outperforms other AQM schemes 3. Transient analysis of an M/M/1 queue with multiple vacations Directory of Open Access Journals (Sweden) Kaliappan Kalidass 2014-05-01 Full Text Available In this paper, we have obtained explicit expressions for the time dependent probabilities of the M/M/1 queue with server vacations under a multiple vacation scheme. The corresponding steady state probabilities have been obtained. We also obtain the time dependent performance measures of the systems 4. Simple approximations for the batch-arrival MX/G/1 queue NARCIS (Netherlands) van Ommeren, Jan C.W. 1990-01-01 In this paper we consider the MX/G/I queueing system with batch arrivals. We give simple approximations for the waiting-time probabilities of individual customers. These approximations are checked numerically and they are found to perform very well for a wide variety of batch-size and service-timed 5. Heavy-traffic analysis for the GI/G/1 queue with heavy-tailed distributions NARCIS (Netherlands) O.J. Boxma (Onno); J.W. Cohen 1997-01-01 textabstractWe consider a$GI/G/1$queue in which the service time distribution and/or the interarrival time distribution has a heavy tail, i.e., a tail behaviour like$t^{-nu$with$1

6. Positive Harris recurrence and diffusion scale analysis of a push pull queueing network

NARCIS (Netherlands)

Nazarathy, J.; Weiss, G.

2010-01-01

We consider a push pull queueing network with two servers and two types of job which are processed by the two servers in opposite order, with stochastic generally distributed processing times. This push pull network was introduced by Kopzon and Weiss, who assumed exponential processing times. It is

7. A finite-buffer queue with a single vacation policy: An analytical study with evolutionary positioning

Directory of Open Access Journals (Sweden)

Woźniak Marcin

2014-12-01

Full Text Available In this paper, application of an evolutionary strategy to positioning a GI/M/1/N-type finite-buffer queueing system with exhaustive service and a single vacation policy is presented. The examined object is modeled by a conditional joint transform of the first busy period, the first idle time and the number of packets completely served during the first busy period. A mathematical model is defined recursively by means of input distributions. In the paper, an analytical study and numerical experiments are presented. A cost optimization problem is solved using an evolutionary strategy for a class of queueing systems described by exponential and Erlang distributions.

8. An M/M/2 Queueing System with Heterogeneous Servers Including One with Working Vacation

Directory of Open Access Journals (Sweden)

A. Krishnamoorthy

2012-01-01

Full Text Available This paper analyzes an M/M/2 queueing system with two heterogeneous servers, one of which is always available but the other goes on vacation in the absence of customers waiting for service. The vacationing server, however, returns to serve at a low rate as an arrival finds the other server busy. The system is analyzed in the steady state using matrix geometric method. Busy period of the system is analyzed and mean waiting time in the stationary regime computed. Conditional stochastic decomposition of stationary queue length is obtained. An illustrative example is also provided.

9. The Geo/Geo/1+1 Queueing System with Negative Customers

OpenAIRE

Ma, Zhanyou; Guo, Yalin; Wang, Pengcheng; Hou, Yumei

2013-01-01

We study a Geo/Geo/1+1 queueing system with geometrical arrivals of both positive and negative customers in which killing strategies considered are removal of customers at the head (RCH) and removal of customers at the end (RCE). Using quasi-birth-death (QBD) process and matrix-geometric solution method, we obtain the stationary distribution of the queue length, the average waiting time of a new arrival customer, and the probabilities of servers in busy or idle period, respectively. Finally, ...

10. A two-queue model with alternating limited service and state-dependent setups

NARCIS (Netherlands)

2005-01-01

We consider a two-queue model with state-dependent setups, in which a single server alternately serves the two queues. The high-priority queue is served exhaustively, whereas the low-priority queue is served according to the k-limited strategy. We obtain the transforms of the queue length and

11. Simple and efficient importance sampling scheme for a tandem queue with server slow-down

NARCIS (Netherlands)

Miretskiy, D.I.; Scheinhardt, W.R.W.; Mandjes, M.R.H.

2008-01-01

This paper considers importance sampling as a tool for rare-event simulation. The system at hand is a so-called tandem queue with slow-down, which essentially means that the server of the first queue (or: upstream queue) switches to a lower speed when the second queue (downstream queue) exceeds some

12. Care on demand in nursing homes: a queueing theoretic approach

NARCIS (Netherlands)

Van Eeden, K.; Moeke, D.; Bekker, R.

2014-01-01

Nursing homes face ever-tightening healthcare budgets and are searching for ways to increase the efficiency of their healthcare processes without losing sight of the needs of their residents. Optimizing the allocation of care workers plays a key role in this search as care workers are responsible

13. Two parallel finite queues with simultaneous services and Markovian arrivals

Directory of Open Access Journals (Sweden)

S. R. Chakravarthy

1997-01-01

Full Text Available In this paper, we consider a finite capacity single server queueing model with two buffers, A and B, of sizes K and N respectively. Messages arrive one at a time according to a Markovian arrival process. Messages that arrive at buffer A are of a different type from the messages that arrive at buffer B. Messages are processed according to the following rules: 1. When buffer A(B has a message and buffer B(A is empty, then one message from A(B is processed by the server. 2. When both buffers, A and B, have messages, then two messages, one from A and one from B, are processed simultaneously by the server. The service times are assumed to be exponentially distributed with parameters that may depend on the type of service. This queueing model is studied as a Markov process with a large state space and efficient algorithmic procedures for computing various system performance measures are given. Some numerical examples are discussed.

14. On the Control of a Queueing System with Aging State Information

NARCIS (Netherlands)

M. Onderwater (Martijn); S. Bhulai (Sandjai); R.D. van der Mei (Rob)

2015-01-01

htmlabstractWe investigate control of a queueing system in which a component of the state space is subject to aging. The controller can choose to forward incoming queries to the system (where it needs time for processing), or respond with a previously generated response (incurring a penalty for not

15. The M/G/1 queue with quasi-restricted accessibility

NARCIS (Netherlands)

Boxma, O.J.; Perry, D.; Stadje, W.; Zacks, S.

2009-01-01

We consider single-server queues of the M/G/1 kind with a special kind of partial customer rejection called quasi-restricted accessibility (QRA). Under QRA, the actual service time assigned to an arriving customer depends on his service requirement, say x, the current workload, say w, and a

16. Simulation-based computation of the workload correlation function in a Lévy-driven queue

NARCIS (Netherlands)

Glynn, P.W.; Mandjes, M.

2011-01-01

In this paper we consider a single-server queue with Lévy input, and, in particular, its workload process (Qt)t≥0, focusing on its correlation structure. With the correlation function defined as r(t):= cov(Q0, Qt) / varQ0 (assuming that the workload process is in stationarity at time 0), we first

17. Simulation-based computation of the workload correlation function in a Levy-driven queue

NARCIS (Netherlands)

P. Glynn; M.R.H. Mandjes (Michel)

2009-01-01

htmlabstractIn this paper we consider a single-server queue with Levy input, and in particular its workload process (Q_t), focusing on its correlation structure. With the correlation function defined as r(t) := Cov(Q_0, Q_t)/Var Q_0 (assuming the workload process is in stationarity at time 0), we

18. Simulation-based computation of the workload correlation function in a Lévy-driven queue

NARCIS (Netherlands)

P. Glynn; M.R.H. Mandjes (Michel)

2010-01-01

htmlabstractIn this paper we consider a single-server queue with Levy input, and in particular its workload process (Q_t), focusing on its correlation structure. With the correlation function defined as r(t) := Cov(Q_0,Q_t)/Var(Q_0) (assuming the workload process is in stationarity at time 0), we

19. Waiting as Part of the Fun: Interactive Gaming in Theme Park Queues

NARCIS (Netherlands)

Heger, Chris; Offermans, S.A.M.; Frens, J.W.; Wouters, I.H.C.; Kimman, F.P.F.; Tieben, R.; Offermans, S.A.M.; Nagtzaam, H.A.H.

2009-01-01

People visiting theme parks intend to have a day of fun. Yet a larger part of the time is spent queuing for rides rather than in the actual rides, which does not contribute to the intended fun experience. Current efforts therefore either make the queue as bearable as possible or try to get rid of it

20. Self-organization of critical behavior in controlled general queueing models

International Nuclear Information System (INIS)

Blanchard, Ph.; Hongler, M.-O.

2004-01-01

We consider general queueing models of the (G/G/1) type with service times controlled by the busy period. For feedback control mechanisms driving the system to very high traffic load, it is shown the busy period probability density exhibits a generic -((3)/(2)) power law which is a typical mean field behavior of SOC models

1. Self-organization of critical behavior in controlled general queueing models

Science.gov (United States)

Blanchard, Ph.; Hongler, M.-O.

2004-03-01

We consider general queueing models of the (G/G/1) type with service times controlled by the busy period. For feedback control mechanisms driving the system to very high traffic load, it is shown the busy period probability density exhibits a generic - {3}/{2} power law which is a typical mean field behavior of SOC models.

2. Self-Interested Routing in Queueing Networks

OpenAIRE

Ali K. Parlaktürk; Sunil Kumar

2004-01-01

We study self-interested routing in stochastic networks, taking into account the discrete stochastic dynamics of such networks. We analyze a two-station multiclass queueing network in which the system manager chooses the scheduling rule and individual customers choose routes in a self-interested manner. We show that this network can be unstable in Nash equilibrium under some scheduling rules. We also design a nontrivial scheduling rule that negates the performance degradation resulting from s...

3. Multiserver Queue with Guard Channel for Priority and Retrial Customers

Directory of Open Access Journals (Sweden)

Kazuki Kajiwara

2016-01-01

Full Text Available This paper considers a retrial queueing model where a group of guard channels is reserved for priority and retrial customers. Priority and normal customers arrive at the system according to two distinct Poisson processes. Priority customers are accepted if there is an idle channel upon arrival while normal customers are accepted if and only if the number of idle channels is larger than the number of guard channels. Blocked customers (priority or normal join a virtual orbit and repeat their attempts in a later time. Customers from the orbit (retrial customers are accepted if there is an idle channel available upon arrival. We formulate the queueing system using a level dependent quasi-birth-and-death (QBD process. We obtain a Taylor series expansion for the nonzero elements of the rate matrices of the level dependent QBD process. Using the expansion results, we obtain an asymptotic upper bound for the joint stationary distribution of the number of busy channels and that of customers in the orbit. Furthermore, we develop an efficient numerical algorithm to calculate the joint stationary distribution.

4. Chimpanzee females queue but males compete for social status

Science.gov (United States)

Foerster, Steffen; Franz, Mathias; Murray, Carson M.; Gilby, Ian C.; Feldblum, Joseph T.; Walker, Kara K.; Pusey, Anne E.

2016-01-01

Dominance hierarchies are widespread in animal social groups and often have measureable effects on individual health and reproductive success. Dominance ranks are not static individual attributes, however, but instead are influenced by two independent processes: 1) changes in hierarchy membership and 2) successful challenges of higher-ranking individuals. Understanding which of these processes dominates the dynamics of rank trajectories can provide insights into fitness benefits of within-sex competition. This question has yet to be examined systematically in a wide range of taxa due to the scarcity of long-term data and a lack of appropriate methodologies for distinguishing between alternative causes of rank changes over time. Here, we expand on recent work and develop a new likelihood-based Elo rating method that facilitates the systematic assessment of rank dynamics in animal social groups, even when interaction data are sparse. We apply this method to characterize long-term rank trajectories in wild eastern chimpanzees (Pan troglodytes schweinfurthii) and find remarkable sex differences in rank dynamics, indicating that females queue for social status while males actively challenge each other to rise in rank. Further, our results suggest that natal females obtain a head start in the rank queue if they avoid dispersal, with potential fitness benefits. PMID:27739527

5. Proposal for optimal placement platform of bikes using queueing networks.

Science.gov (United States)

Mizuno, Shinya; Iwamoto, Shogo; Seki, Mutsumi; Yamaki, Naokazu

2016-01-01

In recent social experiments, rental motorbikes and rental bicycles have been arranged at nodes, and environments where users can ride these bikes have been improved. When people borrow bikes, they return them to nearby nodes. Some experiments have been conducted using the models of Hamachari of Yokohama, the Niigata Rental Cycle, and Bicing. However, from these experiments, the effectiveness of distributing bikes was unclear, and many models were discontinued midway. Thus, we need to consider whether these models are effectively designed to represent the distribution system. Therefore, we construct a model to arrange the nodes for distributing bikes using a queueing network. To adopt realistic values for our model, we use the Google Maps application program interface. Thus, we can easily obtain values of distance and transit time between nodes in various places in the world. Moreover, we apply the distribution of a population to a gravity model and we compute the effective transition probability for this queueing network. If the arrangement of the nodes and number of bikes at each node is known, we can precisely design the system. We illustrate our system using convenience stores as nodes and optimize the node configuration. As a result, we can optimize simultaneously the number of nodes, node places, and number of bikes for each node, and we can construct a base for a rental cycle business to use our system.

6. An Approach to Active Queue Management in Computer Network

OpenAIRE

Asimkiran Dandapat

2016-01-01

Active queue management is a key technique for reducing the packet drop rate in the internet. This packet dropping mechanism is used in a router to minimize congestion when the packets are dropped before queue gets full. In this paper a new framework of Active queue management namely MYRED is proposed. The goal of this new scheme is to improve the performance of AQM by keeping router queue length optimized. In RED packets are marked or dropped with a statistical probability before packet buff...

7. Fokker-Planck description for the queue dynamics of large tick stocks

Science.gov (United States)

Garèche, A.; Disdier, G.; Kockelkoren, J.; Bouchaud, J.-P.

2013-09-01

Motivated by empirical data, we develop a statistical description of the queue dynamics for large tick assets based on a two-dimensional Fokker-Planck (diffusion) equation. Our description explicitly includes state dependence, i.e., the fact that the drift and diffusion depend on the volume present on both sides of the spread. “Jump” events, corresponding to sudden changes of the best limit price, must also be included as birth-death terms in the Fokker-Planck equation. All quantities involved in the equation can be calibrated using high-frequency data on the best quotes. One of our central findings is that the dynamical process is approximately scale invariant, i.e., the only relevant variable is the ratio of the current volume in the queue to its average value. While the latter shows intraday seasonalities and strong variability across stocks and time periods, the dynamics of the rescaled volumes is universal. In terms of rescaled volumes, we found that the drift has a complex two-dimensional structure, which is a sum of a gradient contribution and a rotational contribution, both stable across stocks and time. This drift term is entirely responsible for the dynamical correlations between the ask queue and the bid queue.

8. Efficient priority queueing routing strategy on networks of mobile agents

Science.gov (United States)

Wu, Gan-Hua; Yang, Hui-Jie; Pan, Jia-Hui

2018-03-01

As a consequence of their practical implications for communications networks, traffic dynamics on complex networks have recently captivated researchers. Previous routing strategies for improving transport efficiency have paid little attention to the orders in which the packets should be forwarded, just simply used first-in-first-out queue discipline. Here, we apply a priority queuing discipline and propose a shortest-distance-first routing strategy on networks of mobile agents. Numerical experiments reveal that the proposed scheme remarkably improves both the network throughput and the packet arrival rate and reduces both the average traveling time and the rate of waiting time to traveling time. Moreover, we find that the network capacity increases with an increase in both the communication radius and the number of agents. Our work may be helpful for the design of routing strategies on networks of mobile agents.

9. GEOM/GEOM[a]/1/ queue with late arrival system with delayed access and delayed multiple working vacations

Directory of Open Access Journals (Sweden)

Cheng Jiang

2014-01-01

Full Text Available This paper considers a discrete-time bulk-service queue with infinite buffer space and delay multiple working vacations. Considering a late arrival system with delayed access (LAS-AD, it is assumed that the inter-arrival times, service times, vacation times are all geometrically distributed. The server does not take a vacation immediately at service complete epoch but keeps idle period. According to a bulk-service rule, at least one customer is needed to start a service with a maximum serving capacity 'a'. Using probability analysis method and displacement operator method, the queue length and the probability generating function of waiting time at pre-arrival epochs are obtained. Furthermore, the outside observer’s observation epoch queue length distributions are given. Finally, computational examples with numerical results in the form of graphs and tables are discussed.

10. On the calculation of steady-state loss probabilities in the GI/G/2/0 queue

Directory of Open Access Journals (Sweden)

Igor N. Kovalenko

1994-01-01

Full Text Available This paper considers methods for calculating the steady-state loss probability in the GI/G/2/0 queue. A previous study analyzed this queue in discrete time and this led to an efficient, numerical approximation scheme for continuous-time systems. The primary aim of the present work is to provide an alternative approach by analyzing the GI/ME/2/0 queue; i.e., assuming that the service time can be represented by a matrix-exponential distribution. An efficient computational scheme based on this method is developed and some numerical examples are studied. Some comparisons are made with the discrete-time approach, and the two methods are seen to be complementary.

11. Film traffic queueing model for the DUMC radiology department

International Nuclear Information System (INIS)

Humphrey, L.M.; Ravin, C.E.

1988-01-01

This paper discusses the radiology department traffic model for Duke University Medical Center (DUMC) which simulates the flow of film through the department, and then incorporates the effect of introducing a PACS-type system into present operations. Each Radiology Section is considered separately for queuing of two types of film: old film (from previous exams) and new film (from the present exam). The amount of film in each queue at any time is controlled by controlling hours of operation, service times, delay, and arrival rates. The model also takes into account the use of film in each major radiology area. This gives some idea of the load on a device in that area as well as the amount of storage needed to adequately handle its daily load is local storage at the display device is desired

12. Quasi-stationary analysis for queues with temporary overload

NARCIS (Netherlands)

Cheung, S.K.; Boucherie, Richardus J.; Núñez-Queija, R.

2010-01-01

Motivated by the high variation in transmission rates for document transfer in the Internet and file down loads from web servers, we study the buffer content in a queue with a fluctuating service rate. The fluctuations are assumed to be driven by an independent stochastic process. We allow the queue

13. The M/G/1 queue with permanent customers

NARCIS (Netherlands)

Boxma, O.J.; Cohen, J.W.

1991-01-01

The authors examine an M/G/1 FCFS (first come, first served) queue with two types of customers: ordinary customers, who arrive according to a Poisson process, and permanent customers, who immediately return to the end of the queue after having received a service. The influence of the permanent

14. Adaptive optimization for active queue management supporting TCP flows

NARCIS (Netherlands)

Baldi, S.; Kosmatopoulos, Elias B.; Pitsillides, Andreas; Lestas, Marios; Ioannou, Petros A.; Wan, Y.; Chiu, George; Johnson, Katie; Abramovitch, Danny

2016-01-01

An adaptive decentralized strategy for active queue management of TCP flows over communication networks is presented. The proposed strategy solves locally, at each link, an optimal control problem, minimizing a cost composed of residual capacity and buffer queue size. The solution of the optimal

15. A tandem queue with server slow-down and blocking

NARCIS (Netherlands)

van Foreest, N.D.; van Ommeren, Jan C.W.; Mandjes, M.R.H.; Scheinhardt, Willem R.W.

2005-01-01

We consider two variants of a two-station tandem network with blocking. In both variants the first server ceases to work when the queue length at the second station hits a 'blocking threshold.' In addition, in variant 2 the first server decreases its service rate when the second queue exceeds a

16. A tandem queue with server slow-down and blocking.

NARCIS (Netherlands)

van Foreest, N.; van Ommeren, J.C.; Mandjes, M.R.H.; Scheinhardt, W.

2005-01-01

We consider two variants of a two-station tandem network with blocking. In both variants the first server ceases to work when the queue length at the second station hits a 'blocking threshold.' In addition, in variant 2 the first server decreases its service rate when the second queue exceeds a

17. A fixed-size batch service queue with vacations

Directory of Open Access Journals (Sweden)

Ho Woo Lee

1996-01-01

Full Text Available The paper deals with batch service queues with vacations in which customers arrive according to a Poisson process. Decomposition method is used to derive the queue length distributions both for single and multiple vacation cases. The authors look at other decomposition techniques and discuss some related open problems.

18. Decomposability queueing and computer system applications

CERN Document Server

Courtois, P J

1977-01-01

Decomposability: Queueing and Computer System Applications presents a set of powerful methods for systems analysis. This 10-chapter text covers the theory of nearly completely decomposable systems upon which specific analytic methods are based.The first chapters deal with some of the basic elements of a theory of nearly completely decomposable stochastic matrices, including the Simon-Ando theorems and the perturbation theory. The succeeding chapters are devoted to the analysis of stochastic queuing networks that appear as a type of key model. These chapters also discuss congestion problems in

19. E-Queue Mobile Application

OpenAIRE

Khong Yeen Lai; Ooi Bee Chen; Tan Kok Eng; Binti Ibrahim Salizatul Aizah; Tee Peck Ling

2017-01-01

Waiting in line is a common experience in daily life, whether for a table at a popular restaurant or for the service at a bank. This experience is not always pleasant for most of people because they always have to wait for a long time to be serviced. The ability to interact with waiting customers is highly desirable because it allows businesses the opportunity to optimize their existing services and offer new services to waiting customers. However, interacting with individuals waiting in a qu...

20. A finite capacity queue with Markovian arrivals and two servers with group services

Directory of Open Access Journals (Sweden)

S. Chakravarthy

1994-01-01

Full Text Available In this paper we consider a finite capacity queuing system in which arrivals are governed by a Markovian arrival process. The system is attended by two exponential servers, who offer services in groups of varying sizes. The service rates may depend on the number of customers in service. Using Markov theory, we study this finite capacity queuing model in detail by obtaining numerically stable expressions for (a the steady-state queue length densities at arrivals and at arbitrary time points; (b the Laplace-Stieltjes transform of the stationary waiting time distribution of an admitted customer at points of arrivals. The stationary waiting time distribution is shown to be of phase type when the interarrival times are of phase type. Efficient algorithmic procedures for computing the steady-state queue length densities and other system performance measures are discussed. A conjecture on the nature of the mean waiting time is proposed. Some illustrative numerical examples are presented.

1. Analysis of a multi-server queueing model of ABR

Directory of Open Access Journals (Sweden)

R. Núñez-Queija

1998-01-01

Full Text Available In this paper we present a queueing model for the performance analysis of Available Bit Rate (ABR traffic in Asynchronous Transfer Mode (ATM networks. We consider a multi-channel service station with two types of customers, denoted by high priority and low priority customers. In principle, high priority customers have preemptive priority over low priority customers, except on a fixed number of channels that are reserved for low priority traffic. The arrivals occur according to two independent Poisson processes, and service times are assumed to be exponentially distributed. Each high priority customer requires a single server, whereas low priority customers are served in processor sharing fashion. We derive the joint distribution of the numbers of customers (of both types in the system in steady state. Numerical results illustrate the effect of high priority traffic on the service performance of low priority traffic.

2. Field-theoretic approach to gravity in the flat space-time

Energy Technology Data Exchange (ETDEWEB)

Cavalleri, G [Centro Informazioni Studi Esperienze, Milan (Italy); Milan Univ. (Italy). Ist. di Fisica); Spinelli, G [Istituto di Matematica del Politecnico di Milano, Milano (Italy)

1980-01-01

In this paper it is discussed how the field-theoretical approach to gravity starting from the flat space-time is wider than the Einstein approach. The flat approach is able to predict the structure of the observable space as a consequence of the behaviour of the particle proper masses. The field equations are formally equal to Einstein's equations without the cosmological term.

3. Consciousness induced restoration of time symmetry (CIRTS): a psychophysical theoretical perspective

NARCIS (Netherlands)

Bierman, D.J.

2010-01-01

A theoretical framework is proposed that starts from the assumption that information processing by a brain, while it is sustaining consciousness, is restoring the break in time symmetry in physics. No specifics are given with regard to which physical formalism, either quantum or classical, is the

4. Theoretical and Numerical Properties of a Gyrokinetic Plasma: Issues Related to Transport Time Scale Simulation

International Nuclear Information System (INIS)

Lee, W.W.

2003-01-01

Particle simulation has played an important role for the recent investigations on turbulence in magnetically confined plasmas. In this paper, theoretical and numerical properties of a gyrokinetic plasma as well as its relationship with magnetohydrodynamics (MHD) are discussed with the ultimate aim of simulating microturbulence in transport time scale using massively parallel computers

5. A game-theoretic approach to real-time system testing

DEFF Research Database (Denmark)

David, Alexandre; Larsen, Kim Guldstrand; Li, Shuhao

2008-01-01

This paper presents a game-theoretic approach to the testing of uncontrollable real-time systems. By modelling the systems with Timed I/O Game Automata and specifying the test purposes as Timed CTL formulas, we employ a recently developed timed game solver UPPAAL-TIGA to synthesize winning...... strategies, and then use these strategies to conduct black-box conformance testing of the systems. The testing process is proved to be sound and complete with respect to the given test purposes. Case study and preliminary experimental results indicate that this is a viable approach to uncontrollable timed...... system testing....

6. A spectral theory approach for extreme value analysis in a tandem of fluid queues

NARCIS (Netherlands)

J.W. Bosman (Joost); R. Núñez Queija (Rudesindo)

2014-01-01

htmlabstractWe consider a model to evaluate performance of streaming media over an unreliable network. Our model consists of a tandem of two fluid queues. The first fluid queue is a Markov modulated fluid queue that models the network congestion, and the second queue represents the play-out buffer.

7. Transient solution of an M/M/1 vacation queue with a waiting server and impatient customers

Directory of Open Access Journals (Sweden)

Sherif I. Ammar

2017-07-01

Full Text Available Recently, Ammar [1] has discussed the transient behavior of a multiple vacations queue with impatient customers. In this paper, a similar technique is used to derive a new elegant explicit solution for an M/M/1 vacation queue with impatient customers and a waiting server, where the server is allowed to take a vacation whenever the system is empty after waiting for a random period of time. If the server does not return from the vacation before the expiry of the customer impatience time, the customer abandons the system forever. Moreover, the formulas of mean and variance expressed in terms of the obtained possibilities for this model.

8. Analysis of MAP/PH(1, PH(2/2 Queue with Bernoulli Vacations

Directory of Open Access Journals (Sweden)

V. Thangaraj

2008-12-01

Full Text Available We consider a two-heterogeneous-server queueing system with Bernoulli vacation in which customers arrive according to a Markovian arrival process (MAP. Servers returning from vacation immediately take another vacation if no customer is waiting. Using matrix-geometric method, the steady-state probability of the number of customers in the system is investigated. Some important performance measures are obtained. The waiting time distribution and the mean waiting time are also discussed. Finally, some numerical illustrations are provided.

9. ANALYSIS OF FUZZY QUEUES: PARAMETRIC PROGRAMMING APPROACH BASED ON RANDOMNESS - FUZZINESS CONSISTENCY PRINCIPLE

OpenAIRE

Dhruba Das; Hemanta K. Baruah

2015-01-01

In this article, based on Zadeh’s extension principle we have apply the parametric programming approach to construct the membership functions of the performance measures when the interarrival time and the service time are fuzzy numbers based on the Baruah’s Randomness- Fuzziness Consistency Principle. The Randomness-Fuzziness Consistency Principle leads to defining a normal law of fuzziness using two different laws of randomness. In this article, two fuzzy queues FM...

10. Performance optimization of queueing systems with perturbation realization

KAUST Repository

Xia, Li

2012-04-01

After the intensive studies of queueing theory in the past decades, many excellent results in performance analysis have been obtained, and successful examples abound. However, exploring special features of queueing systems directly in performance optimization still seems to be a territory not very well cultivated. Recent progresses of perturbation analysis (PA) and sensitivity-based optimization provide a new perspective of performance optimization of queueing systems. PA utilizes the structural information of queueing systems to efficiently extract the performance sensitivity information from a sample path of system. This paper gives a brief review of PA and performance optimization of queueing systems, focusing on a fundamental concept called perturbation realization factors, which captures the special dynamic feature of a queueing system. With the perturbation realization factors as building blocks, the performance derivative formula and performance difference formula can be obtained. With performance derivatives, gradient-based optimization can be derived, while with performance difference, policy iteration and optimality equations can be derived. These two fundamental formulas provide a foundation for performance optimization of queueing systems from a sensitivity-based point of view. We hope this survey may provide some inspirations on this promising research topic. © 2011 Elsevier B.V. All rights reserved.

11. The analysis of time-resolved optically stimulated luminescence: I. Theoretical considerations

International Nuclear Information System (INIS)

Chithambo, M L

2007-01-01

This is the first of two linked papers on the analysis of time-resolved optically stimulated luminescence. This paper focusses on a theoretical basis of analytical methods and on methods for interpretation of time-resolved luminescence spectra and calculation of luminescence throughput. Using a comparative analysis of the principal features of time-resolved luminescence and relevant analogues from steady state optical stimulation, formulae for configuring a measurement system for optimum performance are presented. We also examine the possible use of stretched-exponential functions for analysis of time-resolved optically stimulated luminescence spectra

12. Aging of systems: theoretical investigations on system and components time behaviour

International Nuclear Information System (INIS)

Eid, M.; Coudray, R.

1995-01-01

Being a direct indicator of aging, the systems time-dependent failure rates need to be evaluated using qualified methodologies and starting from basic components time-dependent failure data. Basic component time-dependent failure data are not often available. Components failure data used in the paper are issued from some theoretical considerations rather than from field statistical observations. Four academic cases are presented and their results are discussed. Evaluations result in, very often, systems time-dependent failure rates that require understanding and careful interpretation. Kinetic trends of systems and of components may sometimes be different. (authors). 4 figs., 3 tabs., 3 refs., 1 appendix

13. Manajemen Bandwidth Simple Queue dan Queue Tree pada PT. Endorsindo Makmur Selaras

OpenAIRE

Budiman, Arif

2015-01-01

The purpose of this study is to analyze and optimize the bandwidth management at PT. Endorsindo Makmur Selaras, with the expectation that the distribution of bandwidth can be evenly distributed to each employee so that the employee can improve performance and quality of the company. Research methods used include analysis methods (survey and interview system that runs directly on the user) and to optimize bandwidth management method to configure the proxy using the Queue Tree. The re...

14. Comparison of holographic and field theoretic complexities for time dependent thermofield double states

Science.gov (United States)

Yang, Run-Qiu; Niu, Chao; Zhang, Cheng-Yong; Kim, Keun-Young

2018-02-01

We compute the time-dependent complexity of the thermofield double states by four different proposals: two holographic proposals based on the "complexity-action" (CA) conjecture and "complexity-volume" (CV) conjecture, and two quantum field theoretic proposals based on the Fubini-Study metric (FS) and Finsler geometry (FG). We find that four different proposals yield both similarities and differences, which will be useful to deepen our understanding on the complexity and sharpen its definition. In particular, at early time the complexity linearly increase in the CV and FG proposals, linearly decreases in the FS proposal, and does not change in the CA proposal. In the late time limit, the CA, CV and FG proposals all show that the growth rate is 2 E/(πℏ) saturating the Lloyd's bound, while the FS proposal shows the growth rate is zero. It seems that the holographic CV conjecture and the field theoretic FG method are more correlated.

15. Complete analysis of MAP/G/1/N queue with single (multiple vacation(s under limited service discipline

Directory of Open Access Journals (Sweden)

U. C. Gupta

2005-01-01

Full Text Available We consider a finite-buffer single-server queue with Markovian arrival process (MAP where the server serves a limited number of customers, and when the limit is reached it goes on vacation. Both single- and multiple-vacation policies are analyzed and the queue length distributions at various epochs, such as pre-arrival, arbitrary, departure, have been obtained. The effect of certain model parameters on some important performance measures, like probability of loss, mean queue lengths, mean waiting time, is discussed. The model can be applied in computer communication and networking, for example, performance analysis of token passing ring of LAN and SVC (switched virtual connection of ATM.

16. An energy-efficient MAC protocol using dynamic queue management for delay-tolerant mobile sensor networks.

Science.gov (United States)

Li, Jie; Li, Qiyue; Qu, Yugui; Zhao, Baohua

2011-01-01

Conventional MAC protocols for wireless sensor network perform poorly when faced with a delay-tolerant mobile network environment. Characterized by a highly dynamic and sparse topology, poor network connectivity as well as data delay-tolerance, delay-tolerant mobile sensor networks exacerbate the severe power constraints and memory limitations of nodes. This paper proposes an energy-efficient MAC protocol using dynamic queue management (EQ-MAC) for power saving and data queue management. Via data transfers initiated by the target sink and the use of a dynamic queue management strategy based on priority, EQ-MAC effectively avoids untargeted transfers, increases the chance of successful data transmission, and makes useful data reach the target terminal in a timely manner. Experimental results show that EQ-MAC has high energy efficiency in comparison with a conventional MAC protocol. It also achieves a 46% decrease in packet drop probability, 79% increase in system throughput, and 25% decrease in mean packet delay.

17. On finite capacity queueing systems with a general vacation policy

Directory of Open Access Journals (Sweden)

Jacqueline Loris-Teghem

2000-01-01

Full Text Available We consider a Poisson arrival queueing system with finite capacity and a general vacation policy as described in Loris-Teghem [Queueing Systems 3 (1988, 41-52]. From our previous results regarding the stationary queue length distributions immediately after a departure and at an arbitrary epoch, we derive a relation between both distributions which extends a result given in Frey and Takahashi [Operations Research Letters 21 (1997, 95-100] for the particular case of an exhaustive service multiple vacation policy.

18. Optimal Control of a Queue With High-Low Delay Announcements: The Significance of the Queue

Directory of Open Access Journals (Sweden)

Alexandra Koshman-Kaz

2015-02-01

Full Text Available This article deals with strategic control of information in a single-server model. It considers an M/M/1 system with identical customers. There is a single cut-off number, and the level of congestion is said to be low (high if the queue length is less than (at least this value. The firm can dynamically change the admission fee according to the level of congestion. Arriving customers cannot observe the queue length, but they are informed about the current level of congestion and the admission fee. The article deals with finding the profit maximizing admission fee, using analytical and numerical methods. We observe that such a pricing regime can be used to increase the profit and the proportion of the increase relative to the single price unobservable queue is unbounded. We observe that the profit maximizing threshold is usually quite small and therefore raise a question whether there is a significant difference in profit when rather than being informed about the congestion level, customers only join the system when the server is idle. We also investigate this question considering the classical observable model.

19. Modeling an Application's Theoretical Minimum and Average Transactional Response Times

Energy Technology Data Exchange (ETDEWEB)

Paiz, Mary Rose [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

2015-04-01

The theoretical minimum transactional response time of an application serves as a ba- sis for the expected response time. The lower threshold for the minimum response time represents the minimum amount of time that the application should take to complete a transaction. Knowing the lower threshold is beneficial in detecting anomalies that are re- sults of unsuccessful transactions. On the converse, when an application's response time falls above an upper threshold, there is likely an anomaly in the application that is causing unusual performance issues in the transaction. This report explains how the non-stationary Generalized Extreme Value distribution is used to estimate the lower threshold of an ap- plication's daily minimum transactional response time. It also explains how the seasonal Autoregressive Integrated Moving Average time series model is used to estimate the upper threshold for an application's average transactional response time.

20. Analysis of queueing system with discrete autoregressive arrivals having DML as marginal distribution

Directory of Open Access Journals (Sweden)

Bindu Abraham

2014-05-01

Full Text Available In this paper we analyze DAR(1/D/s Queue with Discrete Mittag-Leffler [DML(α] as marginal distribution. Simulation study of the sample path of the arrival process is conducted. For this queueing system, the stationary distribution of the system size and the waiting time distribution of an arbitrary packet is obtained with the help of matrix analytic methods and Markov regenerative theory. The quantitative effect of the stationary distribution on system size, waiting time and  the autocorrelation function as well as the parameters of the input traffic is illustrated empirically. The model is applied to a real data on the passenger arrivals at a subway bus terminal in Santiago de Chile and is established that the model well suits this data.

1. On buffer overflow duration in a finite-capacity queueing system with multiple vacation policy

Science.gov (United States)

Kempa, Wojciech M.

2017-12-01

A finite-buffer queueing system with Poisson arrivals and generally distributed processing times, operating under multiple vacation policy, is considered. Each time when the system becomes empty, the service station takes successive independent and identically distributed vacation periods, until, at the completion epoch of one of them, at least one job waiting for service is detected in the buffer. Applying analytical approach based on the idea of embedded Markov chain, integral equations and linear algebra, the compact-form representation for the cumulative distribution function (CDF for short) of the first buffer overflow duration is found. Hence, the formula for the CDF of next such periods is obtained. Moreover, probability distributions of the number of job losses in successive buffer overflow periods are found. The considered queueing system can be efficienly applied in modelling energy saving mechanisms in wireless network communication.

2. Fast distributed strategic learning for global optima in queueing access games

KAUST Repository

Tembine, Hamidou

2014-08-24

In this paper we examine combined fully distributed payoff and strategy learning (CODIPAS) in a queue-aware access game over a graph. The classical strategic learning analysis relies on vanishing or small learning rate and uses stochastic approximation tool to derive steady states and invariant sets of the underlying learning process. Here, the stochastic approximation framework does not apply due to non-vanishing learning rate. We propose a direct proof of convergence of the process. Interestingly, the convergence time to one of the global optima is almost surely finite and we explicitly characterize the convergence time. We show that pursuit-based CODIPAS learning is much faster than the classical learning algorithms in games. We extend the methodology to coalitional learning and proves a very fast formation of coalitions for queue-aware access games where the action space is dynamically changing depending on the location of the user over a graph.

3. The MAP, M/G1,G2/1 queue with preemptive priority

Directory of Open Access Journals (Sweden)

Bong Dae Choi

1997-01-01

Full Text Available We consider the MAP, M/G1,G2/1 queue with preemptive resume priority, where low priority customers arrive to the system according to a Markovian arrival process (MAP and high priority customers according to a Poisson process. The service time density function of low (respectively: high priority customers is g1(x (respectively: g2(x. We use the supplementary variable method with Extended Laplace Transforms to obtain the joint transform of the number of customers in each priority queue, as well as the remaining service time for the customer in service in the steady state. We also derive the probability generating function for the number of customers of low (respectively, high priority in the system just after the service completion epochs for customers of low (respectively, high priority.

4. Transient analysis of a queue with queue-length dependent MAP and its application to SS7 network

Directory of Open Access Journals (Sweden)

Bong Dae Choi

1999-01-01

Full Text Available We analyze the transient behavior of a Markovian arrival queue with congestion control based on a double of thresholds, where the arrival process is a queue-length dependent Markovian arrival process. We consider Markov chain embedded at arrival epochs and derive the one-step transition probabilities. From these results, we obtain the mean delay and the loss probability of the nth arrival packet. Before we study this complex model, first we give a transient analysis of an MAP/M/1 queueing system without congestion control at arrival epochs. We apply our result to a signaling system No. 7 network with a congestion control based on thresholds.

5. What money can't buy: allocations with priority lists, lotteries and queues

OpenAIRE

Daniele Condorelli

2009-01-01

I study the welfare optimal allocation of a number of identical and indivisible objects to a set of heterogeneous risk-neutral agents under the hypothesis that money is not available. Agents have independent private values, which represent the maximum time that they are will- ing to wait in line to obtain a good. A priority list, which ranks agents according to their expected values, is optimal when hazard rates of the distributions of values are increasing. Queues, which allocates the ob- je...

6. Report on dynamic speed harmonization and queue warning algorithm design.

Science.gov (United States)

2014-02-01

This report provides a detailed description of the algorithms that will be used to generate harmonized recommended speeds : and queue warning information in the proposed Intelligent Network Flow Optimization (INFLO) prototype. This document : describ...

7. A robust fractional-order PID controller design based on active queue management for TCP network

Science.gov (United States)

Hamidian, Hamideh; Beheshti, Mohammad T. H.

2018-01-01

In this paper, a robust fractional-order controller is designed to control the congestion in transmission control protocol (TCP) networks with time-varying parameters. Fractional controllers can increase the stability and robustness. Regardless of advantages of fractional controllers, they are still not common in congestion control in TCP networks. The network parameters are time-varying, so the robust stability is important in congestion controller design. Therefore, we focused on the robust controller design. The fractional PID controller is developed based on active queue management (AQM). D-partition technique is used. The most important property of designed controller is the robustness to the time-varying parameters of the TCP network. The vertex quasi-polynomials of the closed-loop characteristic equation are obtained, and the stability boundaries are calculated for each vertex quasi-polynomial. The intersection of all stability regions is insensitive to network parameter variations, and results in robust stability of TCP/AQM system. NS-2 simulations show that the proposed algorithm provides a stable queue length. Moreover, simulations show smaller oscillations of the queue length and less packet drop probability for FPID compared to PI and PID controllers. We can conclude from NS-2 simulations that the average packet loss probability variations are negligible when the network parameters change.

8. An asymptotic analysis of closed queueing networks with branching populations

OpenAIRE

Bayer, N.; Coffman, E.G.; Kogan, Y.A.

1995-01-01

textabstractClosed queueing networks have proven to be valuable tools for system performance analysis. In this paper, we broaden the applications of such networks by incorporating populations of {em branching customers: whenever a customer completes service at some node of the network, it is replaced by N>=0 customers, each routed independently to a next node, where N has a given, possibly node-dependent branching distribution. Applications of these branching and queueing networks focus on {e...

9. A Queueing Model for Supervisory Control of Unmanned Autonomous Vehicles

Science.gov (United States)

2013-09-01

Autonomous Vehicles Joseph DiVita, PhD Robert L. Morris Maria Olinda Rodas SSC Pacific Approved...298 (Rev. 8/98) Prescribed by ANSI Std. Z39.18 09–2013 Final A Queueing Model for Supervisory Control of Unmanned Autonomous Vehicles Joseph...Mission Area: Command and Control, Queueing Model; Supervisory Control; Unmanned Autonomous Vehicles M. O. Rodas U U U U 38 (619)

10. Data Model Approach And Markov Chain Based Analysis Of Multi-Level Queue Scheduling

Directory of Open Access Journals (Sweden)

Diwakar Shukla

2010-01-01

Full Text Available There are many CPU scheduling algorithms inliterature like FIFO, Round Robin, Shortest-Job-First and so on.The Multilevel-Queue-Scheduling is superior to these due to itsbetter management of a variety of processes. In this paper, aMarkov chain model is used for a general setup of Multilevelqueue-scheduling and the scheduler is assumed to performrandom movement on queue over the quantum of time.Performance of scheduling is examined through a rowdependent data model. It is found that with increasing value of αand d, the chance of system going over the waiting state reduces.At some of the interesting combinations of α and d, it diminishesto zero, thereby, provides us some clue regarding better choice ofqueues over others for high priority jobs. It is found that ifqueue priorities are added in the scheduling intelligently thenbetter performance could be obtained. Data model helpschoosing appropriate preferences.

11. Increasing available FIFO space to prevent messaging queue deadlocks in a DMA environment

Science.gov (United States)

Blocksome, Michael A [Rochester, MN; Chen, Dong [Croton On Hudson, NY; Gooding, Thomas [Rochester, MN; Heidelberger, Philip [Cortlandt Manor, NY; Parker, Jeff [Rochester, MN

2012-02-07

Embodiments of the invention may be used to manage message queues in a parallel computing environment to prevent message queue deadlock. A direct memory access controller of a compute node may determine when a messaging queue is full. In response, the DMA may generate an interrupt. An interrupt handler may stop the DMA and swap all descriptors from the full messaging queue into a larger queue (or enlarge the original queue). The interrupt handler then restarts the DMA. Alternatively, the interrupt handler stops the DMA, allocates a memory block to hold queue data, and then moves descriptors from the full messaging queue into the allocated memory block. The interrupt handler then restarts the DMA. During a normal messaging advance cycle, a messaging manager attempts to inject the descriptors in the memory block into other messaging queues until the descriptors have all been processed.

12. Tool supported modeling of sensor communication networks by using finite-source priority retrial queues

Directory of Open Access Journals (Sweden)

Tamas Berczes

2012-06-01

Full Text Available The main aim of the present paper is to draw the attention of the readers of this special issue to the modeling issues of sensor networks. The novelty of this investigation is the introduction of servers vacation combined with priority customers for finite-source retrial queues and its application to wireless sensor networks. In this paper we analyze a priority finite-source retrial queue with repeated vacations. Two types of priority customers are defined, customers with priority 1 (P1 go directly to an ordinary FIFO queue. However, if customers with priority 2 (P2 find the server in busy or unavailable state go to the orbit. These customers stay in the orbit and retry their request until find the server in idle and available state. We assume that P1 customers have non-preemptive priority over P2 customers. The server starts with a listening period and if no customer arrive during this period it will enter in the vacation mode. When the vacation period is terminated, then the node wakes up. If there is a P1 customer in the queue the server begin to serve it, and when there is no any P1 customer, the node will remain awake for exponentially distributed time period. If that period expires without arrivals the node will enter in the next sleeping period. All random variables involved in model construction are supposed to be independent and exponentially distributed ones. Our main interest is to give the main steady-state performance measures of the system computed by the help of the MOSEL tool. Several Figures illustrate the effect of input parameters on the mean response time.

13. Priority Queue Based Reactive Buffer Management Policy for Delay Tolerant Network under City Based Environments.

Directory of Open Access Journals (Sweden)

Qaisar Ayub

Full Text Available Delay Tolerant Network (DTN multi-copy routing protocols are privileged to create and transmit multiple copies of each message that causes congestion and some messages are dropped. This process is known as reactive drop because messages were dropped re-actively to overcome buffer overflows. The existing reactive buffer management policies apply a single metric to drop source, relay and destine messages. Hereby, selection to drop a message is dubious because each message as source, relay or destine may have consumed dissimilar magnitude of network resources. Similarly, DTN has included time to live (ttl parameter which defines lifetime of message. Hence, when ttl expires then message is automatically destroyed from relay nodes. However, time-to-live (ttl is not applicable on messages reached at their destinations. Moreover, nodes keep replicating messages till ttl expires even-though large number of messages has already been dispersed. In this paper, we have proposed Priority Queue Based Reactive Buffer Management Policy (PQB-R for DTN under City Based Environments. The PQB-R classifies buffered messages into source, relay and destine queues. Moreover, separate drop metric has been applied on individual queue. The experiment results prove that proposed PQB-R has reduced number of messages transmissions, message drop and increases delivery ratio.

14. Priority Queue Based Reactive Buffer Management Policy for Delay Tolerant Network under City Based Environments.

Science.gov (United States)

2018-01-01

Delay Tolerant Network (DTN) multi-copy routing protocols are privileged to create and transmit multiple copies of each message that causes congestion and some messages are dropped. This process is known as reactive drop because messages were dropped re-actively to overcome buffer overflows. The existing reactive buffer management policies apply a single metric to drop source, relay and destine messages. Hereby, selection to drop a message is dubious because each message as source, relay or destine may have consumed dissimilar magnitude of network resources. Similarly, DTN has included time to live (ttl) parameter which defines lifetime of message. Hence, when ttl expires then message is automatically destroyed from relay nodes. However, time-to-live (ttl) is not applicable on messages reached at their destinations. Moreover, nodes keep replicating messages till ttl expires even-though large number of messages has already been dispersed. In this paper, we have proposed Priority Queue Based Reactive Buffer Management Policy (PQB-R) for DTN under City Based Environments. The PQB-R classifies buffered messages into source, relay and destine queues. Moreover, separate drop metric has been applied on individual queue. The experiment results prove that proposed PQB-R has reduced number of messages transmissions, message drop and increases delivery ratio.

15. ANALYTICAL CHARACTERIZATION OF WLANS FOR QUALITY-OF-SERVICE WITH ACTIVE QUEUE MANAGEMENT

Directory of Open Access Journals (Sweden)

M. Usha

2014-09-01

Full Text Available Design of an Active Queue Management scheme at the Access Point to address the problem of congestion control, packet delay variation and packet loss rate is discussed. The proposed mechanism calculates and adjusts redundancy rate adaptively at the access point by considering both network traffic load and wireless channel condition. Real-time applications such as Mobile learning and smart learning need the special treatment and require differentiated QoS to satisfy the client who is ready to pay more than others. Maintaining the jitter value of the multimedia packets below the threshold is essential to guarantee the desirable quality of the video at the receiver. The work initially concentrates on minimizing the packet loss of such priority flows and they have to be given place in the queue even at the time of buffer overflow. Thus the proposed work uses push-out policy to provide differentiated services to the multimedia flow which achieves considerable improvement in the video quality at the receiver. The considerable decrease in packet loss rate and special treatment in the queue of the access point lowers the packet delay variation of the multimedia flow. The results show that the AQM used at the access point effectively achieves low packet loss, low jitter using differentiated FEC rate calculation without generating congestion in the wireless network.

16. Dynamic Performance Optimization for Cloud Computing Using M/M/m Queueing System

Directory of Open Access Journals (Sweden)

Lizheng Guo

2014-01-01

Full Text Available Successful development of cloud computing has attracted more and more people and enterprises to use it. On one hand, using cloud computing reduces the cost; on the other hand, using cloud computing improves the efficiency. As the users are largely concerned about the Quality of Services (QoS, performance optimization of the cloud computing has become critical to its successful application. In order to optimize the performance of multiple requesters and services in cloud computing, by means of queueing theory, we analyze and conduct the equation of each parameter of the services in the data center. Then, through analyzing the performance parameters of the queueing system, we propose the synthesis optimization mode, function, and strategy. Lastly, we set up the simulation based on the synthesis optimization mode; we also compare and analyze the simulation results to the classical optimization methods (short service time first and first in, first out method, which show that the proposed model can optimize the average wait time, average queue length, and the number of customer.

17. An exact solution for the state probabilities of the multi-class, multi-server queue with preemptive priorities

NARCIS (Netherlands)

Sleptchenko, Andrei; van Harten, Aart; van der Heijden, Matthijs C.

2005-01-01

We consider a multi-class, multi-server queueing system with preemptive priorities. We distinguish two groups of priority classes that consist of multiple customer types, each having their own arrival and service rate. We assume Poisson arrival processes and exponentially distributed service times.

18. Study of a Dynamic Cooperative Trading Queue Routing Control Scheme for Freeways and Facilities with Parallel Queues

OpenAIRE

Lloret-Batlle, Roger; Jayakrishnan, R.

2018-01-01

This article explores the coalitional stability of a new cooperative control policy for freeways and parallel queuing facilities with multiple servers. Based on predicted future delays per queue or lane, a VOT-heterogeneous population of agents can agree to switch lanes or queues and transfer payments to each other in order to minimize the total cost of the incoming platoon. The strategic interaction is captured by an n-level Stackelberg model with coalitions, while the cooperative structure ...

19. Perbandingan Metode Simple Queues Dan Queues Tree Untuk Optimasi Manajemen Bandwidth Jaringan Komputer Di STMIK PPKIA Pradnya Paramita Malang

OpenAIRE

Syaifuddin, Aris; Yunus, Mahmud; Sundari, Retno

2013-01-01

This research resulted in a comparison between the Simple Queues method and Queues Tree using Mikrotik router that takes a case study in STMIK PPKIA PRADNYA PARAMITA MALANG has been tested to determine which method is the most optimal deal of bandwidth sharing on computer networks. After finding out where the most optimal method will be applied in STMIK PPKIA PRADNYA PARAMITA MALANG to maximize network performance and bandwidth sharing in place, the results of the study lead to the conclusion...

20. An Elementary Derivation of Mean Wait Time in Polling Systems

OpenAIRE

2012-01-01

Polling systems are a well-established subject in queueing theory. However, their formal treatments generally rely heavily on relatively sophisticated theoretical tools, such as moment generating functions and Laplace transforms, and solutions often require the solution of large systems of equations. We show that, if you are willing to only have the average waiting of a system time rather than higher moments, it can found through an elementary derivation based only on algebra and some well-kn...

1. Modeling Message Queueing Services with Reliability Guarantee in Cloud Computing Environment Using Colored Petri Nets

Directory of Open Access Journals (Sweden)

Jing Li

2015-01-01

Full Text Available Motivated by the need for loosely coupled and asynchronous dissemination of information, message queues are widely used in large-scale application areas. With the advent of virtualization technology, cloud-based message queueing services (CMQSs with distributed computing and storage are widely adopted to improve availability, scalability, and reliability; however, a critical issue is its performance and the quality of service (QoS. While numerous approaches evaluating system performance are available, there is no modeling approach for estimating and analyzing the performance of CMQSs. In this paper, we employ both the analytical and simulation modeling to address the performance of CMQSs with reliability guarantee. We present a visibility-based modeling approach (VMA for simulation model using colored Petri nets (CPN. Our model incorporates the important features of message queueing services in the cloud such as replication, message consistency, resource virtualization, and especially the mechanism named visibility timeout which is adopted in the services to guarantee system reliability. Finally, we evaluate our model through different experiments under varied scenarios to obtain important performance metrics such as total message delivery time, waiting number, and components utilization. Our results reveal considerable insights into resource scheduling and system configuration for service providers to estimate and gain performance optimization.

2. State dependent arrival in bulk retrial queueing system with immediate Bernoulli feedback, multiple vacations and threshold

Science.gov (United States)

Niranjan, S. P.; Chandrasekaran, V. M.; Indhira, K.

2017-11-01

The objective of this paper is to analyse state dependent arrival in bulk retrial queueing system with immediate Bernoulli feedback, multiple vacations, threshold and constant retrial policy. Primary customers are arriving into the system in bulk with different arrival rates λ a and λ b . If arriving customers find the server is busy then the entire batch will join to orbit. Customer from orbit request service one by one with constant retrial rate γ. On the other hand if an arrival of customers finds the server is idle then customers will be served in batches according to general bulk service rule. After service completion, customers may request service again with probability δ as feedback or leave from the system with probability 1 - δ. In the service completion epoch, if the orbit size is zero then the server leaves for multiple vacations. The server continues the vacation until the orbit size reaches the value ‘N’ (N > b). At the vacation completion, if the orbit size is ‘N’ then the server becomes ready to provide service for customers from the main pool or from the orbit. For the designed queueing model, probability generating function of the queue size at an arbitrary time will be obtained by using supplementary variable technique. Various performance measures will be derived with suitable numerical illustrations.

3. A queueing theory description of fat-tailed price returns in imperfect financial markets

Science.gov (United States)

Lamba, H.

2010-09-01

In a financial market, for agents with long investment horizons or at times of severe market stress, it is often changes in the asset price that act as the trigger for transactions or shifts in investment position. This suggests the use of price thresholds to simulate agent behavior over much longer timescales than are currently used in models of order-books. We show that many phenomena, routinely ignored in efficient market theory, can be systematically introduced into an otherwise efficient market, resulting in models that robustly replicate the most important stylized facts. We then demonstrate a close link between such threshold models and queueing theory, with large price changes corresponding to the busy periods of a single-server queue. The distribution of the busy periods is known to have excess kurtosis and non-exponential decay under various assumptions on the queue parameters. Such an approach may prove useful in the development of mathematical models for rapid deleveraging and panics in financial markets, and the stress-testing of financial institutions.

4. Variable dead time counters. 1 - theoretical responses and the effects of neutron multiplication

International Nuclear Information System (INIS)

Lees, E.W.; Hooton, B.W.

1978-10-01

A theoretical expression is derived for calculating the response of any variable dead time counter (VDC) used in the passive assay of plutonium by neutron counting of the natural spontaneous fission activity. The effects of neutron multiplication in the sample arising from interactions of the original spontaneous fission neutrons is shown to modify the linear relationship between VDC signal and Pu mass. Numerical examples are shown for the Euratom VDC and a systematic investigation of the various factors affecting neutron multiplication is reported. Limited comparisons between the calculations and experimental data indicate provisional validity of the calculations. (author)

5. Decision theoretical justification of optimization criteria for near-real-time accountancy procedures

International Nuclear Information System (INIS)

Avenhaus, R.

1992-01-01

In the beginning of nuclear material safeguards, emphasis was placed on safe detection of diversion of nuclear material. Later, the aspect of timely detection became equally important. Since there is a trade-off between these two objectives, the question of an appropriate compromise was raised. In this paper, a decision theoretical framework is presented in which the objectives of the two players, inspector and inspectee, are expressed in terms of general utility functions. Within this framework, optimal safeguards strategies are defined, and furthermore, conditions are formulated under which the optimization criteria corresponding to the objectives mentioned above can be justified

6. Theoretical framework of the causes of construction time and cost overruns

Science.gov (United States)

Ullah, K.; Abdullah, A. H.; Nagapan, S.; Suhoo, S.; Khan, M. S.

2017-11-01

Any construction practitioner fundamental goal is to complete the projects within estimated duration and budgets, and expected quality targets. However, time and cost overruns are regular and universal phenomenon in construction projects and the construction projects in Malaysia has no exemption from the problems of time overrun and cost overrun. In order to accomplish the successful completion of construction projects on specified time and within planned cost, there are various factors that should be given serious attention so that issues such as time and cost overrun can be addressed. This paper aims to construct a framework for the causes of time overrun and cost overrun in construction projects of Malaysia. Based on the relevant literature review, causative factors of time overrun and cost overrun in Malaysian construction projects are summarized and the theoretical frameworks of the causes of construction time overrun and cost overrun is constructed. The developed frameworks for construction time and cost overruns based on the existing literature will assist the construction practitioners to plan the efficient approaches for achieving successful completion of the projects.

7. Ethics in radiology: wait lists queue jumping.

Science.gov (United States)

Cunningham, Natalie; Reid, Lynette; MacSwain, Sarah; Clarke, James R

2013-08-01

8. The transient M/G/1/0 queue: some bounds and approximations for light traffic with application to reliability

Directory of Open Access Journals (Sweden)

J. Ben Atkinson

1995-01-01

Full Text Available We consider the transient analysis of the M/G/1/0 queue, for which Pn(t denotes the probability that there are no customers in the system at time t, given that there are n(n=0,1 customers in the system at time 0. The analysis, which is based upon coupling theory, leads to simple bounds on Pn(t for the M/G/1/0 and M/PH/1/0 queues and improved bounds for the special case M/Er/1/0. Numerical results are presented for various values of the mean arrival rate λ to demonstrate the increasing accuracy of approximations based upon the above bounds in light traffic, i.e., as λ→0. An important area of application for the M/G/1/0 queue is as a reliability model for a single repairable component. Since most practical reliability problems have λ values that are small relative to the mean service rate, the approximations are potentially useful in that context. A duality relation between the M/G/1/0 and GI/M/1/0 queues is also described.

9. Time-dependent theoretical treatments of the dynamics of electrons and nuclei in molecular systems

International Nuclear Information System (INIS)

Deumens, E.; Diz, A.; Longo, R.; Oehrn, Y.

1994-01-01

An overview is presented of methods for time-dependent treatments of molecules as systems of electrons and nuclei. The theoretical details of these methods are reviewed and contrasted in the light of a recently developed time-dependent method called electron-nuclear dynamics. Electron-nuclear dynamics (END) is a formulation of the complete dynamics of electrons and nuclei of a molecular system that eliminates the necessity of constructing potential-energy surfaces. Because of its general formulation, it encompasses many aspects found in other formulations and can serve as a didactic device for clarifying many of the principles and approximations relevant in time-dependent treatments of molecular systems. The END equations are derived from the time-dependent variational principle applied to a chosen family of efficiently parametrized approximate state vectors. A detailed analysis of the END equations is given for the case of a single-determinantal state for the electrons and a classical treatment of the nuclei. The approach leads to a simple formulation of the fully nonlinear time-dependent Hartree-Fock theory including nuclear dynamics. The nonlinear END equations with the ab initio Coulomb Hamiltonian have been implemented at this level of theory in a computer program, ENDyne, and have been shown feasible for the study of small molecular systems. Implementation of the Austin Model 1 semiempirical Hamiltonian is discussed as a route to large molecular systems. The linearized END equations at this level of theory are shown to lead to the random-phase approximation for the coupled system of electrons and nuclei. The qualitative features of the general nonlinear solution are analyzed using the results of the linearized equations as a first approximation. Some specific applications of END are presented, and the comparison with experiment and other theoretical approaches is discussed

10. A game theoretic approach to a finite-time disturbance attenuation problem

Science.gov (United States)

Rhee, Ihnseok; Speyer, Jason L.

1991-01-01

A disturbance attenuation problem over a finite-time interval is considered by a game theoretic approach where the control, restricted to a function of the measurement history, plays against adversaries composed of the process and measurement disturbances, and the initial state. A zero-sum game, formulated as a quadratic cost criterion subject to linear time-varying dynamics and measurements, is solved by a calculus of variation technique. By first maximizing the quadratic cost criterion with respect to the process disturbance and initial state, a full information game between the control and the measurement residual subject to the estimator dynamics results. The resulting solution produces an n-dimensional compensator which expresses the controller as a linear combination of the measurement history. A disturbance attenuation problem is solved based on the results of the game problem. For time-invariant systems it is shown that under certain conditions the time-varying controller becomes time-invariant on the infinite-time interval. The resulting controller satisfies an H(infinity) norm bound.

11. Theoretical analysis of time-dependent neutron spectra in bulk assemblies

International Nuclear Information System (INIS)

Akimoto, Tadashi; Ogawa, Yuichi; Togawa, Orihiko.

1988-01-01

Time-dependent neutron spectra in an iron assembly and in a graphite assembly are obtained with the one-dimensional S N calculation, in order an attempt to investigate the availability of these spectra to the benchmark test by the LINAC-TOF method for evaluation of nuclear data and numerical methods. The group constants are taken from the JAERI FAST SET Version 1, 2 and the ABBN SET. It was demonstrated by a sensitivity test that the time-dependent neutron spectra are sensitive to changes in the inelastic scattering cross section data in the iron assembly and to changes in the elastic scattering cross section data in the graphite assembly. Moreover, it is shown that the time-dependent spectra in the graphite assembly are sensitive to the group structure. Because some information about the neutron transport phenomena which has not been obtained in the stationary spectra is observed in the time-dependent spectra, the availability of the benchmark test based on the time-dependent spectra is indicated from the theoretical analysis. (author)

12. An introduction to queueing theory modeling and analysis in applications

CERN Document Server

Bhat, U Narayan

2015-01-01

This introductory textbook is designed for a one-semester course on queueing theory that does not require a course on stochastic processes as a prerequisite. By integrating the necessary background on stochastic processes with the analysis of models, the work provides a sound foundational introduction to the modeling and analysis of queueing systems for a wide interdisciplinary audience of students in mathematics, statistics, and applied disciplines such as computer science, operations research, and engineering. This edition includes additional topics in methodology and applications. Key features: • An introductory chapter including a historical account of the growth of queueing theory in more than 100 years. • A modeling-based approach with emphasis on identification of models. • Rigorous treatment of the foundations of basic models commonly used in applications with appropriate references for advanced topics. • Applications in manufacturing and, computer and communication systems. • A chapter on ...

13. Parallel discrete-event simulation of FCFS stochastic queueing networks

Science.gov (United States)

Nicol, David M.

1988-01-01

Physical systems are inherently parallel. Intuition suggests that simulations of these systems may be amenable to parallel execution. The parallel execution of a discrete-event simulation requires careful synchronization of processes in order to ensure the execution's correctness; this synchronization can degrade performance. Largely negative results were recently reported in a study which used a well-known synchronization method on queueing network simulations. Discussed here is a synchronization method (appointments), which has proven itself to be effective on simulations of FCFS queueing networks. The key concept behind appointments is the provision of lookahead. Lookahead is a prediction on a processor's future behavior, based on an analysis of the processor's simulation state. It is shown how lookahead can be computed for FCFS queueing network simulations, give performance data that demonstrates the method's effectiveness under moderate to heavy loads, and discuss performance tradeoffs between the quality of lookahead, and the cost of computing lookahead.

14. Algorithm for queueing networks with multi-rate traffic

DEFF Research Database (Denmark)

Iversen, Villy Bæk; Ko, King-Tim

2011-01-01

the nodes behave as independent nodes. For closed queueing networks with multiple servers in every node and multi-rate services we may apply multidimensional convolution algorithm to aggregate the nodes so that we end up with two nodes, the aggregated node and a single node, for which we can calculate......In this paper we present a new algorithm for evaluating queueing networks with multi-rate traffic. The detailed state space of a node is evaluated by explicit formulæ. We consider reversible nodes with multi-rate traffic and find the state probabilities by taking advantage of local balance. Theory...... of queueing networks in general, presumes that we have product form between the nodes. Otherwise, we have the state space explosion. Even so, the detailed state space of each node may become very large because there is no product form between chains inside a node. A prerequisite for product form...

15. Algorithm for queueing networks with multi-rate traffic

DEFF Research Database (Denmark)

Iversen, Villy Bæk; King-Tim, Ko

2011-01-01

the nodes behave as independent nodes. For closed queueing networks with multiple servers in every node and multi-rate services we may apply multidimensional convolutions to aggregate the nodes so that we end up with two nodes, the aggregated node and a single node, for which we can calculate the detailed......In this paper we present a new algorithm for evaluating queueing networks with multi-rate traffic. The detailed state space of a node is evaluated by explicit formulæ. We consider reversible nodes with multi-rate traffic and find the state probabilities by taking advantage of local balance. Theory...... of queueing networks in general presumes that we have product form between the nodes. Other ways we have the state space explosion. Even so the detailed state space of each node may easily become very large because there is no product form between chains inside a node. A prerequisite for product form...

16. Performance analysis of parallel identical machines with a generalized shortest queue arrival mechanism

NARCIS (Netherlands)

van Houtum, Geert-Jan; Adan, I.J.B.F.; Wessels, J.; Zijm, Willem H.M.

In this paper we study a production system consisting of a group of parallel machines producing multiple job types. Each machine has its own queue and it can process a restricted set of job types only. On arrival a job joins the shortest queue among all queues capable of serving that job. Under the

17. Theoretical analysis and real time implementation of a classical controller with intelligent properties

Directory of Open Access Journals (Sweden)

Essam Hendawi

2018-05-01

Full Text Available This paper presents theoretical analysis and experimental implementation of a classical controller with intelligent properties. The controller has constant parameters, but it performs as an intelligent controller. The controller design mimics the fuzzy logic controller in a classical form and combines the advantages of classical controllers and properties of intelligent controllers. The designed controller parameters force the controlled variable to behave such as a first order system with a desired time constant. DC motor practical system is used to demonstrate the effectiveness of the presented controller. Root locus and frequency response using Bode diagram are used to help the design of the controller parameters. Simulation and experimental results verify the high performance of the presented controller. Keywords: Classical controller, DC motor, Root locus, Frequency response, Arduino microcontroller

18. A Game-Theoretic Approach to Branching Time Abstract-Check-Refine Process

Science.gov (United States)

Wang, Yi; Tamai, Tetsuo

2009-01-01

Since the complexity of software systems continues to grow, most engineers face two serious problems: the state space explosion problem and the problem of how to debug systems. In this paper, we propose a game-theoretic approach to full branching time model checking on three-valued semantics. The three-valued models and logics provide successful abstraction that overcomes the state space explosion problem. The game style model checking that generates counter-examples can guide refinement or identify validated formulas, which solves the system debugging problem. Furthermore, output of our game style method will give significant information to engineers in detecting where errors have occurred and what the causes of the errors are.

19. DecreaseKeys are Expensive for External Memory Priority Queues

OpenAIRE

Eenberg, Kasper; Larsen, Kasper Green; Yu, Huacheng

2016-01-01

One of the biggest open problems in external memory data structures is the priority queue problem with DecreaseKey operations. If only Insert and ExtractMin operations need to be supported, one can design a comparison-based priority queue performing $O((N/B)\\lg_{M/B} N)$ I/Os over a sequence of $N$ operations, where $B$ is the disk block size in number of words and $M$ is the main memory size in number of words. This matches the lower bound for comparison-based sorting and is hence optimal fo...

20. Efficient simulation of finite horizon problems in queueing and insurance risk

DEFF Research Database (Denmark)

Rojas-Nandayapa, Leonardo; Asmussen, Søren

2007-01-01

Let ψ(u,t) be the probability that the workload in an initially empty M/G/1 queue exceeds u at time tprobability in the classical Crámer-Lundberg model. Assuming service times/claim sizes to be subexponential, various Monte Carlo estimators for ψ(u,t) are suggested....... A key idea behind the estimators is conditional Monte Carlo. Variance estimates are derived in the regularly varying case, the efficiencies are compared numerically and also the estimators are shown to have bounded relative error in some main cases. In part, also extensions to general Lévy processes...

1. Analysis of Repairable Geo/G/1 Queues with Negative Customers

Directory of Open Access Journals (Sweden)

Doo Ho Lee

2014-01-01

Full Text Available We consider discrete-time Geo/G/1 queues with negative customers and a repairable server. The server is subject to failure due to a negative customer arrival. As soon as a negative customer arrives at a system, the server fails and one positive (ordinary customer is forced to leave. At a failure instant, the server is turned off and the repair process immediately begins. We construct the mathematical model and present the probability generating functions of the system size distribution and the FCFS sojourn time distribution. Finally, some numerical examples are given to show the influence of negative customer arrival on the performance measures of the system.

2. Pricing in M/M/1 queues when cost of waiting in queue differs from cost of waiting in service

Directory of Open Access Journals (Sweden)

Görkem Sarıyer

2016-11-01

Full Text Available Service providers can adjust the entrance price to the state of the demand in real life service systems where the customers' decision to receive the service, is based on this price, state of demand and other system parameters. We analyzed service provider's short and long term pricing problems in unobservable M/M/1 queues having the rational customers, where, for customers, the unit cost of waiting in the queue is higher than unit cost of waiting in the service. We showed that waiting in the queue has a clear negative effect on customers’ utilities, hence the service provider's price values. We also showed that, in the short term, monopolistic pricing is optimal for congested systems with high server utilization levels, whereas in the long term, market capturing pricing is more profitable.

3. On Mx/(G1G2/1/G(BS/Vs vacation queue with two types of general heterogeneous service

Directory of Open Access Journals (Sweden)

2005-01-01

Full Text Available We analyze a batch arrival queue with a single server providing two kinds of general heterogeneous service. Just before his service starts, a customer may choose one of the services and as soon as a service (of any kind gets completed, the server may take a vacation or may continue staying in the system. The vacation times are assumed to be general and the server vacations are based on Bernoulli schedules under a single vacation policy. We obtain explicit queue size distribution at a random epoch as well as at a departure epoch and also the mean busy period of the server under the steady state. In addition, some important performance measures such as the expected queue size and the expected waiting time of a customer are obtained. Further, some interesting particular cases are also discussed.

4. Buffer Management of Multi-Queue QoS Switches with Class Segregation

OpenAIRE

Itoh, Toshiya; Yoshimoto, Seiji

2013-01-01

In this paper, we focus on buffer management of multi-queue QoS switches in which packets of different values are segregated in different queues. Our model consists of $m$ queues and $m$ packet values $0 < v_{1} < v_{2} < ... < v_{m}$. Recently, Al-Bawani and Souza [IPL 113(4), pp.145-150, 2013] presented an online algorithm GREEDY for buffer management of multi-queue QoS switches with class segregation and showed thatif $m$ queues have the same size, then the competitive ratio of GREEDY is ... 5. A cooperative approach to queue allocation of indivisible objects NARCIS (Netherlands) Hamers, H.J.M.; Klijn, F.; Slikker, M.; Velzen, van B. 2009-01-01 We consider the allocation of a finite number of indivisible objects to the same number of agents according to an exogenously given queue. We assume that the agents collaborate in order to achieve an efficient outcome for society. We allow for side-payments and provide a method for obtaining stable 6. A queueing model with randomized depletion of inventory NARCIS (Netherlands) Albrecher, H.-J.; Boxma, O.J.; Essifi, R.; Kuijstermans, A.C.M. 2015-01-01 In this paper we study an M/M/1 queue, where the server continues to work during idle periods and builds up inventory. This inventory is used for new arriving service requirements, but it is completely emptied at random epochs of a Poisson process, whose rate depends on the current level of the 7. An adversarial queueing model for online server routing NARCIS (Netherlands) Bonifaci, V. 2007-01-01 In an online server routing problem, a vehicle or server moves in a network in order to process incoming requests at the nodes. Online server routing problems have been thoroughly studied using competitive analysis. We propose a new model for online server routing, based on adversarial queueing 8. Single-server queues with spatially distributed arrivals NARCIS (Netherlands) Kroese, Dirk; Schmidt, Volker 1994-01-01 Consider a queueing system where customers arrive at a circle according to a homogeneous Poisson process. After choosing their positions on the circle, according to a uniform distribution, they wait for a single server who travels on the circle. The server's movement is modelled by a Brownian motion 9. Arrival first queueing networks with applications in kanban production systems NARCIS (Netherlands) Boucherie, R.J.; Chao, X.; Miyazawa, M. 2001-01-01 In this paper we introduce a new class of queueing networks called {\\it arrival first networks}. We characterise its transition rates and derive the relationship between arrival rules, linear partial balance equations, and product form stationary distributions. This model is motivated by production 10. Arrival first queueing networks with applications in kanban production systems NARCIS (Netherlands) Boucherie, Richardus J.; Chao, X.; Miyazawa, M. 2003-01-01 In this paper, we introduce a new class of queueing networks called arrival first networks. We characterise its transition rates and derive the relationship between arrival rules, linear partial balance equations, and product form stationary distributions. This model is motivated by production 11. Performance analysis of manufacturing systems : queueing approximations and algorithms NARCIS (Netherlands) Vuuren, van M. 2007-01-01 Performance Analysis of Manufacturing Systems Queueing Approximations and Algorithms This thesis is concerned with the performance analysis of manufacturing systems. Manufacturing is the application of tools and a processing medium to the transformation of raw materials into finished goods for sale. 12. Estimation of the workload correlation in a Markov fluid queue NARCIS (Netherlands) Kaynar, B.; Mandjes, M.R.H. 2013-01-01 This paper considers a Markov fluid queue, focusing on the correlation function of the stationary workload process. A simulation-based computation technique is proposed, which relies on a coupling idea. Then an upper bound on the variance of the resulting estimator is given, which reveals how the 13. A scheme for evaluating a local queue warning system. NARCIS (Netherlands) Botma, H. & Oei, H.-L. 2018-01-01 This article outlines a method of evaluating a 'local queue warning system', in principle intended only to warn drivers of unexpected congestion at known discontinuities of the road geomctry (bottleneck) and give them advisory speed indications. A prerequisite for installing this system is therefore 14. 7. Data Structures: Lists, Queues, Stacks and Arrays Indian Academy of Sciences (India) Home; Journals; Resonance – Journal of Science Education; Volume 2; Issue 6. Algorithms - Data Structures: Lists, Queues, Stacks and Arrays. R K Shyamasundar. Series Article Volume 2 Issue 6 June 1997 pp 39-46. Fulltext. Click here to view fulltext PDF. Permanent link: 15. Analysis of a multi-server queueing model of ABR NARCIS (Netherlands) R. Núñez Queija (Rudesindo); O.J. Boxma (Onno) 1996-01-01 textabstractIn this paper we present a queueing model for the performance a-na-ly-sis of ABR traffic in ATM networks. We consider a multi-channel service station with two types of customers, the first having preemptive priority over the second. The arrivals occur according to two independent Poisson 16. Efficient Simulation of Population Overflow in Parallel Queues NARCIS (Netherlands) Nicola, V.F.; Zaburnenko, T.S. 2006-01-01 In this paper we propose a state-dependent importance sampling heuristic to estimate the probability of population overﬂow in networks of parallel queues. This heuristic approximates the “optimal��? state-dependent change of measure without the need for dif��?cult mathematical analysis or costly 17. Moving toward queue operations at the Large Binocular Telescope Observatory Science.gov (United States) Edwards, Michelle L.; Summers, Doug; Astier, Joseph; Suarez Sola, Igor; Veillet, Christian; Power, Jennifer; Cardwell, Andrew; Walsh, Shane 2016-07-01 The Large Binocular Telescope Observatory (LBTO), a joint scientific venture between the Instituto Nazionale di Astrofisica (INAF), LBT Beteiligungsgesellschaft (LBTB), University of Arizona, Ohio State University (OSU), and the Research Corporation, is one of the newest additions to the world's collection of large optical/infrared ground-based telescopes. With its unique, twin 8.4m mirror design providing a 22.8 meter interferometric baseline and the collecting area of an 11.8m telescope, LBT has a window of opportunity to exploit its singular status as the "first" of the next generation of Extremely Large Telescopes (ELTs). Prompted by urgency to maximize scientific output during this favorable interval, LBTO recently re-evaluated its operations model and developed a new strategy that augments classical observing with queue. Aided by trained observatory staff, queue mode will allow for flexible, multi-instrument observing responsive to site conditions. Our plan is to implement a staged rollout that will provide many of the benefits of queue observing sooner rather than later - with more bells and whistles coming in future stages. In this paper, we outline LBTO's new scientific model, focusing specifically on our "lean" resourcing and development, reuse and adaptation of existing software, challenges presented from our one-of-a-kind binocular operations, and lessons learned. We also outline further stages of development and our ultimate goals for queue. 18. Python for Scientific Computing Education: Modeling of Queueing Systems Directory of Open Access Journals (Sweden) Vladimiras Dolgopolovas 2014-01-01 Full Text Available In this paper, we present the methodology for the introduction to scientific computing based on model-centered learning. We propose multiphase queueing systems as a basis for learning objects. We use Python and parallel programming for implementing the models and present the computer code and results of stochastic simulations. 19. Approximations for Markovian multi-class queues with preemptive priorities NARCIS (Netherlands) van der Heijden, Matthijs C.; van Harten, Aart; Sleptchenko, Andrei 2004-01-01 We discuss the approximation of performance measures in multi-class M/M/k queues with preemptive priorities for large problem instances (many classes and servers) using class aggregation and server reduction. We compared our approximations to exact and simulation results and found that our approach 20. Method, apparatus and system for managing queue operations of a test bench environment Science.gov (United States) Ostler, Farrell Lynn 2016-07-19 Techniques and mechanisms for performing dequeue operations for agents of a test bench environment. In an embodiment, a first group of agents are each allocated a respective ripe reservation and a second set of agents are each allocated a respective unripe reservation. Over time, queue management logic allocates respective reservations to agents and variously changes one or more such reservations from unripe to ripe. In another embodiment, an order of servicing agents allocated unripe reservations is based on relative priorities of the unripe reservations with respect to one another. An order of servicing agents allocated ripe reservations is on a first come, first served basis. 1. Comparing the Overhead of Lock-based and Lock-free Implementations of Priority Queues DEFF Research Database (Denmark) Passas, Stavros; Karlsson, Sven 2011-01-01 . In this paper, we compare a lock-free implementation of a priority queue with a lock-based implementation. We perform experiments with processors of different generations and observe large performance differences for lock-free data structures depending on the processor generation. The lock-free implementation...... performs much better on the most recent processor generation. We investigate this performance trend, using a set of micro-benchmarks and show a significant difference in the overhead of atomic operations between processor generations. The lock-free implementation executes approximately three times as many... 2. Computational Approach to Profit Optimization of a Loss-Queueing System Directory of Open Access Journals (Sweden) Dinesh Kumar Yadav 2010-01-01 Full Text Available Objective of the paper is to deal with the profit optimization of a loss queueing system with the finite capacity. Here, we define and compute total expected cost (TEC, total expected revenue (TER and consequently we compute the total optimal profit (TOP of the system. In order to compute the total optimal profit of the system, a computing algorithm has been developed and a fast converging N-R method has been employed which requires least computing time and lesser memory space as compared to other methods. Sensitivity analysis and its observations based on graphics have added a significant value to this model. 3. A Game Theoretic Approach to Minimize the Completion Time of Network Coded Cooperative Data Exchange KAUST Repository Douik, Ahmed S. 2014-05-11 In this paper, we introduce a game theoretic framework for studying the problem of minimizing the completion time of instantly decodable network coding (IDNC) for cooperative data exchange (CDE) in decentralized wireless network. In this configuration, clients cooperate with each other to recover the erased packets without a central controller. Game theory is employed herein as a tool for improving the distributed solution by overcoming the need for a central controller or additional signaling in the system. We model the session by self-interested players in a non-cooperative potential game. The utility function is designed such that increasing individual payoff results in a collective behavior achieving both a desirable system performance in a shared network environment and the Pareto optimal solution. Through extensive simulations, our approach is compared to the best performance that could be found in the conventional point-to-multipoint (PMP) recovery process. Numerical results show that our formulation largely outperforms the conventional PMP scheme in most practical situations and achieves a lower delay. 4. A Game Theoretic Approach to Minimize the Completion Time of Network Coded Cooperative Data Exchange KAUST Repository Douik, Ahmed S.; Al-Naffouri, Tareq Y.; Alouini, Mohamed-Slim; Sorour, Sameh; Tembine, Hamidou 2014-01-01 In this paper, we introduce a game theoretic framework for studying the problem of minimizing the completion time of instantly decodable network coding (IDNC) for cooperative data exchange (CDE) in decentralized wireless network. In this configuration, clients cooperate with each other to recover the erased packets without a central controller. Game theory is employed herein as a tool for improving the distributed solution by overcoming the need for a central controller or additional signaling in the system. We model the session by self-interested players in a non-cooperative potential game. The utility function is designed such that increasing individual payoff results in a collective behavior achieving both a desirable system performance in a shared network environment and the Pareto optimal solution. Through extensive simulations, our approach is compared to the best performance that could be found in the conventional point-to-multipoint (PMP) recovery process. Numerical results show that our formulation largely outperforms the conventional PMP scheme in most practical situations and achieves a lower delay. 5. Information-Theoretic Performance Analysis of Sensor Networks via Markov Modeling of Time Series Data. Science.gov (United States) Li, Yue; Jha, Devesh K; Ray, Asok; Wettergren, Thomas A; Yue Li; Jha, Devesh K; Ray, Asok; Wettergren, Thomas A; Wettergren, Thomas A; Li, Yue; Ray, Asok; Jha, Devesh K 2018-06-01 This paper presents information-theoretic performance analysis of passive sensor networks for detection of moving targets. The proposed method falls largely under the category of data-level information fusion in sensor networks. To this end, a measure of information contribution for sensors is formulated in a symbolic dynamics framework. The network information state is approximately represented as the largest principal component of the time series collected across the network. To quantify each sensor's contribution for generation of the information content, Markov machine models as well as x-Markov (pronounced as cross-Markov) machine models, conditioned on the network information state, are constructed; the difference between the conditional entropies of these machines is then treated as an approximate measure of information contribution by the respective sensors. The x-Markov models represent the conditional temporal statistics given the network information state. The proposed method has been validated on experimental data collected from a local area network of passive sensors for target detection, where the statistical characteristics of environmental disturbances are similar to those of the target signal in the sense of time scale and texture. A distinctive feature of the proposed algorithm is that the network decisions are independent of the behavior and identity of the individual sensors, which is desirable from computational perspectives. Results are presented to demonstrate the proposed method's efficacy to correctly identify the presence of a target with very low false-alarm rates. The performance of the underlying algorithm is compared with that of a recent data-driven, feature-level information fusion algorithm. It is shown that the proposed algorithm outperforms the other algorithm. 6. Efficient simulation of finite horizon problems in queueing and insurance risk DEFF Research Database (Denmark) Rojas-Nandayapa, Leonardo; Asmussen, Søren Let ψ(u, t) be the probability that the workload in an initially empty M/G/1 queue exceeds u at time t < ∞, or, equivalently, the ruin probability in the classical Crámer-Lundberg model. Assuming service times/claim sizes to be subexponential, various Monte Carlo estimators for ψ(u, t) are sugges......Let ψ(u, t) be the probability that the workload in an initially empty M/G/1 queue exceeds u at time t classical Crámer-Lundberg model. Assuming service times/claim sizes to be subexponential, various Monte Carlo estimators for ψ(u, t......) are suggested. A key idea behind the estimators is conditional Monte Carlo. Variance estimates are derived in the regularly varying case, the eﬃciencies are compared numerically and also one of the estimators is shown to have bounded relative error. In part, also extensions to general Lévy processes are treated.... 7. Design of Active Queue Management for Robust Control on Access Router for Heterogeneous Networks Directory of Open Access Journals (Sweden) Åhlund Christer 2011-01-01 Full Text Available The Internet architecture is a packet switching technology that allows dynamic sharing of bandwidth among different flows with in an IP network. Packets are stored and forwarded from one node to the next until reaching their destination. Major issues in this integration are congestion control and how to meet different quality of service requirements associated with various services. In other words streaming media quality degrades with increased packet delay and jitter caused by network congestion. To mitigate the impact of network congestion, various techniques have been used to improve multimedia quality and one of those techniques is Active Queue Management (AQM. Access routers require a buffer to hold packets during times of congestion. A large buffer can absorb the bursty arrivals, and this tends to increase the link utilizations but results in higher queuing delays. Traffic burstiness has a considerable negative impact on network performance. AQM is now considered an effective congestion control mechanism for enhancing transport protocol performance over wireless links. In order to have good link utilization, it is necessary for queues to adapt to varying traffic loads. This paper considers a particular scheme which is called Adaptive AQM (AAQM and studies its performance in the presence of feedback delays and its ability to maintain a small queue length as well as its robustness in the presence of traffic burstiness. The paper also presents a method based on the well-known Markov Modulated Poisson Process (MPP to capture traffic burstiness and buffer occupancy. To demonstrate the generality of the presented method, an analytic model is described and verified by extensive simulations of different adaptive AQM algorithms. The analysis and simulations show that AAQM outperforms the other AQMs with respect to responsiveness and robustness. 8. Approximation of the steady state system state distribution of the M/G/1 retrial queue with impatient customers Directory of Open Access Journals (Sweden) Stihi Nadjet 2012-01-01 Full Text Available For M/G/1 retrial queues with impatient customers, we review the results, concerning the steady state distribution of the system state, presented in the literature. Since the existing formulas are cumbersome (so their utilization in practice becomes delicate or the obtaining of these formulas is impossible, we apply the information theoretic techniques for estimating the above mentioned distribution. More concretely, we use the principle of maximum entropy which provides an adequate methodology for computing a unique estimate for an unknown probability distribution based on information expressed in terms of some given mean value constraints. 9. Competing for jobs: labor queues and gender sorting in the hiring process. Science.gov (United States) Fernandez, Roberto M; Mors, Marie Louise 2008-12-01 While much research has documented the pattern and extent of sex segregation of workers once they are employed, few studies have addressed the pre-hire mechanisms that are posited to produce sex segregation in employment. While the notion of a labor queue-the rank order of the set of people that employers choose among-plays a prominent role in pre-hire accounts of job sex sorting mechanisms, few studies have examined the ways in which job candidates are sorted into labor queues. In this paper, we explore the mechanisms by which labor queues contribute to the gendering of jobs by studying the hiring process for all jobs at a call center. Being placed in a queue has a clear gendering effect on the hiring process: the sex distribution of applicants who are matched to queues and those who are rejected at this phase diverge, and among those assigned to queues, women are prevalent in queues for low pay, low status jobs. The screening process also contributes to the gendering of the population of hires at this firm. Females are more prevalent among hires than they are among candidates at initial queue assignment. Among high status jobs, however, males are more prevalent than females. Moreover, there are important wage implications associated with matching to queues. While there are large between-queue sex differences in the paid wages associated with allocation to queues, once allocated to queues the wage differences between male and female candidates are nil. Consequently, the roots of gender wage inequality in this setting lie in the initial sorting of candidates to labor queues. 10. A theoretical analysis of time-dependent fragment momenta in indirect photofragmentation DEFF Research Database (Denmark) Henriksen, Niels Engholm 2010-01-01 We study theoretically diatomic molecules which are prepared in a superposition of quasibound resonance states by a femtosecond laser pulse. An analytical (Landau–Zener-like) result is derived for the momentum distribution of the atomic fragments in the asymptotic force-free region after a single... 11. Exploring super-gaussianity towards robust information-theoretical time delay estimation DEFF Research Database (Denmark) Petsatodis, Theodoros; Talantzis, Fotios; Boukis, Christos 2013-01-01 the effect upon TDE when modeling the source signal with different speech-based distributions. An information theoretical TDE method indirectly encapsulating higher order statistics (HOS) formed the basis of this work. The underlying assumption of Gaussian distributed source has been replaced... 12. The Effect of Queueing Strategy on Network Traffic International Nuclear Information System (INIS) Zhang Xue-Jun; Guan Xiang-Min; Sun Deng-Feng; Tang Shao-Ting 2013-01-01 In recent years, the transportation system has been faced by increasing challenge in congestion and inefficiency, and research in traffic network has become a significant area of interest. In this paper, we introduce a dynamic-information-based (DIB) queueing strategy into network traffic model under the efficient routing strategy. DIB makes a packet with higher priority to be delivered if there are less packets travelling along its path from the current node to the destination. It is found that, compared with the traditional first-in-first-out (FIFO) queueing strategy, DIB can effectively balance the traffic load of the system via delaying packets to be delivered to congested nodes. Although the network capacity has no obvious changes, some other indexes which reflect transportation efficiency are efficiently improved in the congestion state. Besides, extensive simulation results and discussions are provided to explain the phenomena. The results may provide novel insights for research on traffic systems. (condensed matter: structural, mechanical, and thermal properties) 13. Adaptive Queue Management with Restraint on Non-Responsive Flows Directory of Open Access Journals (Sweden) Lan Li 2003-12-01 Full Text Available This paper proposes an adaptive queue management scheme (adaptive RED to improve Random Early Detection (RED on restraining non-responsive flows. Due to a lack of flow control mechanism, non-responsive flows can starve responsive flows for buffer and bandwidth at the gateway. In order to solve the disproportionate resource problem, RED framework is modified in this way: on detecting when the non-responsive flows starve the queue, packet-drop intensity (Max_p in RED can be adaptively adjusted to curb non-responsive flows for resource fair-sharing, such as buffer and bandwidth fair-sharing. Based on detection of traffic behaviors, intentionally restraining nonresponsive flows is to increase the throughput and decrease the drop rate of responsive flows. Our experimental results based on adaptive RED shows that the enhancement of responsive traffic and the better sharing of buffer and bandwidth can be achieved under a variety of traffic scenarios. 14. SAM: Support Vector Machine Based Active Queue Management International Nuclear Information System (INIS) Shah, M.S. 2014-01-01 Recent years have seen an increasing interest in the design of AQM (Active Queue Management) controllers. The purpose of these controllers is to manage the network congestion under varying loads, link delays and bandwidth. In this paper, a new AQM controller is proposed which is trained by using the SVM (Support Vector Machine) with the RBF (Radial Basis Function) kernal. The proposed controller is called the support vector based AQM (SAM) controller. The performance of the proposed controller has been compared with three conventional AQM controllers, namely the Random Early Detection, Blue and Proportional Plus Integral Controller. The preliminary simulation studies show that the performance of the proposed controller is comparable to the conventional controllers. However, the proposed controller is more efficient in controlling the queue size than the conventional controllers. (author) 15. Elements of queueing theory palm martingale calculus and stochastic recurrences CERN Document Server Baccelli, François 2003-01-01 The Palm theory and the Loynes theory of stationary systems are the two pillars of the modern approach to queuing. This book, presenting the mathematical foundations of the theory of stationary queuing systems, contains a thorough treatment of both of these. This approach helps to clarify the picture, in that it separates the task of obtaining the key system formulas from that of proving convergence to a stationary state and computing its law. The theory is constantly illustrated by classical results and models: Pollaczek-Khintchin and Tacacs formulas, Jackson and Gordon-Newell networks, multiserver queues, blocking queues, loss systems etc., but it also contains recent and significant examples, where the tools developed turn out to be indispensable. Several other mathematical tools which are useful within this approach are also presented, such as the martingale calculus for point processes, or stochastic ordering for stationary recurrences. This thoroughly revised second edition contains substantial addition... 16. The queue as a social statement / Maria-Kristiina Soomre Index Scriptorium Estoniae Soomre, Maria-Kristiina, 1978- 2010-01-01 Tallinna Lauluväljakul veebruaris 2010 olnud töötute järjekorrast, kus 5000-st said alternatiivse töö reisisaatjatena 400. Keskerakonna kampaaniatest, mida võib vaadata sotsiaalse kunsti kontekstis. Sügisel 2010 Tallinna Kunstihoone juures korraldatud kunstiprojektist "Art Queue 100x100 EEK", millega sooviti tõmmata tähelepanu kunstiinstitutsioonile. Seoses kunstiga tekkinud järjekordadest, masside valmidusest kampaania korras rünnata kunsti 17. Large deviations and queueing networks: Methods for rate function identification OpenAIRE Atar, Rami; Dupuis, Paul 1999-01-01 This paper considers the problem of rate function identification for multidimensional queueing models with feedback. A set of techniques are introduced which allow this identification when the model possesses certain structural properties. The main tools used are representation formulas for exponential integrals, weak convergence methods, and the regularity properties of associated Skorokhod Problems. Two examples are treated as special cases of the general theory: the classical Jackson netwo... 18. Vehicle routing with dynamic travel times : a queueing approach NARCIS (Netherlands) Woensel, van T.; Kerbache, L.; Peremans, H.; Vandaele, N.J. 2008-01-01 Transportation is an important component of supply chain competitiveness since it plays a major role in the inbound, inter-facility, and outbound logistics. In this context, assigning and scheduling vehicle routes is a crucial management problem. In this paper, a vehicle routing problem with dynamic 19. Infinite Queue Management via Cascade Control for Industrial Routers in Smart Grid IP Networks OpenAIRE Kim, Ku-Hwan; To, Hoang-Linh; Hwang, Won-Joo; Lee, Jung-Tae 2016-01-01 Smart grid applications experience an extremely wide range of communication delay. Data flows of those applications are normally aggregated at industrial network routers in substations, form infinite (long) queues termed bufferbloat issue, and might damage the operation of transmission control protocol. The default queue management scheme, DropTail, in such routers just drops packets if queue is full while the others in literature are mostly based on one-loop feedback control where an optimal... 20. Analysis of Multiserver Queueing System with Opportunistic Occupation and Reservation of Servers Directory of Open Access Journals (Sweden) Bin Sun 2014-01-01 Full Text Available We consider a multiserver queueing system with two input flows. Type-1 customers have preemptive priority and are lost during arrival only if all servers are occupied by type-1 customers. If all servers are occupied, but some provide service to type-2 customers, service of type-2 customer is terminated and type-1 customer occupies the server. If the number of busy servers is less than the threshold M during type-2 customer arrival epoch, this customer is accepted. Otherwise, it is lost or becomes a retrial customer. It will retry to obtain service. Type-2 customer whose service is terminated is lost or moves to the pool of retrial customers. The service time is exponentially distributed with the rate dependent on the customer’s type. Such queueing system is suitable for modeling cognitive radio. Type-1 customers are interpreted as requests generated by primary users. Type-2 customers are generated by secondary or cognitive users. The problem of optimal choice of the threshold M is the subject of this paper. Behavior of the system is described by the multidimensional Markov chain. Its generator, ergodicity condition, and stationary distribution are given. The system performance measures are obtained. The numerical results show the effectiveness of considered admission control. 1. A QoS-Based Dynamic Queue Length Scheduling Algorithm in Multiantenna Heterogeneous Systems Directory of Open Access Journals (Sweden) Verikoukis Christos 2010-01-01 Full Text Available The use of real-time delay-sensitive applications in wireless systems has significantly grown during the last years. Therefore the designers of wireless systems have faced a challenging issue to guarantee the required Quality of Service (QoS. On the other hand, the recent advances and the extensive use of multiple antennas have already been included in several commercial standards, where the multibeam opportunistic transmission beamforming strategies have been proposed to improve the performance of the wireless systems. A cross-layer-based dynamically tuned queue length scheduler is presented in this paper, for the Downlink of multiuser and multiantenna WLAN systems with heterogeneous traffic requirements. To align with modern wireless systems transmission strategies, an opportunistic scheduling algorithm is employed, while a priority to the different traffic classes is applied. A tradeoff between the maximization of the throughput of the system and the guarantee of the maximum allowed delay is obtained. Therefore, the length of the queue is dynamically adjusted to select the appropriate conditions based on the operator requirements. 2. Data Mining Foundations and Intelligent Paradigms Volume 2 Statistical, Bayesian, Time Series and other Theoretical Aspects CERN Document Server Jain, Lakhmi 2012-01-01 Data mining is one of the most rapidly growing research areas in computer science and statistics. In Volume 2 of this three volume series, we have brought together contributions from some of the most prestigious researchers in theoretical data mining. Each of the chapters is self contained. Statisticians and applied scientists/ engineers will find this volume valuable. Additionally, it provides a sourcebook for graduate students interested in the current direction of research in data mining. 3. An Energy-Efficient MAC Protocol Using Dynamic Queue Management for Delay-Tolerant Mobile Sensor Networks Directory of Open Access Journals (Sweden) Yugui Qu 2011-02-01 Full Text Available Conventional MAC protocols for wireless sensor network perform poorly when faced with a delay-tolerant mobile network environment. Characterized by a highly dynamic and sparse topology, poor network connectivity as well as data delay-tolerance, delay-tolerant mobile sensor networks exacerbate the severe power constraints and memory limitations of nodes. This paper proposes an energy-efficient MAC protocol using dynamic queue management (EQ-MAC for power saving and data queue management. Via data transfers initiated by the target sink and the use of a dynamic queue management strategy based on priority, EQ-MAC effectively avoids untargeted transfers, increases the chance of successful data transmission, and makes useful data reach the target terminal in a timely manner. Experimental results show that EQ-MAC has high energy efficiency in comparison with a conventional MAC protocol. It also achieves a 46% decrease in packet drop probability, 79% increase in system throughput, and 25% decrease in mean packet delay. 4. Apparatus and method for managing digital resources by passing digital resource tokens between queues Science.gov (United States) Crawford, H.J.; Lindenstruth, V. 1999-06-29 A method of managing digital resources of a digital system includes the step of reserving token values for certain digital resources in the digital system. A selected token value in a free-buffer-queue is then matched to an incoming digital resource request. The selected token value is then moved to a valid-request-queue. The selected token is subsequently removed from the valid-request-queue to allow a digital agent in the digital system to process the incoming digital resource request associated with the selected token. Thereafter, the selected token is returned to the free-buffer-queue. 6 figs. 5. The optimal control in batch arrival queue with server vacations, startup and breakdowns Directory of Open Access Journals (Sweden) Ke Jau-Chuan 2004-01-01 Full Text Available This paper studies the N policy M[x]/G/1 queue with server vacations; startup and breakdowns, where arrivals form a compound Poisson process and service times are generally distributed. The server is turned off and takes a vacation whenever the system is empty. If the number of customers waiting in the system at the instant of a vacation completion is less than N, the server will take another vacation. If the server returns from a vacation and finds at least N customers in the system, he is immediately turned on and requires a startup time before providing the service until the system is empty again. It is assumed that the server breaks down according to a Poisson process whose repair time has a general distribution. The system characteristics of such a model are analyzed and the total expected cost function per unit time is developed to determine the optimal threshold of N at a minimum cost. 6. On the GI/M/1 Queue with Vacations and Multiple Service Phases Directory of Open Access Journals (Sweden) Jianjun Li 2017-01-01 Full Text Available This paper considers a GI/M/1 queue with vacations and multiple service phases. Whenever the system becomes empty, the server takes a vacation, causing the system to move to vacation phase 0. If the server returns from a vacation to find no customer waiting, another vacation begins. Otherwise, the system jumps from phase 0 to some service phase i with probability qi, i=1,2,…,N. Using the matrix geometric solution method and semi-Markov process, we obtain the distributions of the stationary system size at both arrival and arbitrary epochs. The distribution of the stationary waiting time of an arbitrary customer is also derived. In addition, we present some performance measures such as mean waiting time of an arbitrary customer, mean length of the type-i cycle, and mean number of customers in the system at the end of phase 0. Finally, some numerical examples are presented. 7. On the automation of periodic hard real-time processes: a graph-theoretical approach OpenAIRE Boode, Antoon Hendrik 2018-01-01 Summary In certain single-core mono-processor configurations, e.g. embedded control systems like robotic applications comprising many short processes, process context switches may consume a considerable amount of the available processing power. Reducing the number of context switches decreases the execution time and thereby increases the performance of the application. Furthermore, the end-to-end processing time suffers from the idle time of the processor, because, for example, processes have... 8. System-theoretic analysis of due-time performance in production systems OpenAIRE Jacobs David; Meerkov Semyon M. 1995-01-01 Along with the average production rate, the due-time performance is an important characteristic of manufacturing systems. Unlike the production rate, the due-time performance has received relatively little attention in the literature, especially in the context of large volume production. This paper is devoted to this topic. Specifically, the notion of due-time performance is formalized as the probability that the number of parts produced during the shipping period reaches the required shipme... 9. Convergence of a Queueing System in Heavy Traffic with General Abandonment Distributions Science.gov (United States) 2010-10-08 331–391, 2005. [4] R. Atar . Scheduling control for queueing systems with many servers: asymptotic optimality in heavy traffic. Ann. Appl. Probab., 15...4):2606–2650, 2005. 37 [5] R. Atar , A. Mandelbaum, and M. I. Reiman. Scheduling a multi class queue with many exponential servers: asymptotic 10. Matrix-geometric analysis of the shortest queue problem with threshold jockeying NARCIS (Netherlands) Zijm, Willem H.M.; Adan, I.J.B.F.; Wessels, J. 1993-01-01 In this paper we study a system consisting of c parallel servers with possibly different service rates. Jobs arrive according to a Poisson stream and generate an exponentially distributed workload. An arriving job joins the shortest queue, where in case of multiple shortest queues, one of these 11. Analysis of an M/G/1 queue with customer impatience and an adaptive arrival process NARCIS (Netherlands) Boxma, O.J.; Prabhu, B.J. 2009-01-01 We study an M/G/1 queue with impatience and an adaptive arrival process. The rate of the arrival process changes according to whether an incoming customer is accepted or rejected. We analyse two different models for impatience : (i) based on workload, and (ii) based on queue length. For the 12. Routing policies for a partially observable two-server queueing system NARCIS (Netherlands) Ellens, W.; Kovács, P.; Núñez-Queija, R.; Berg, H. van den 2015-01-01 We consider a queueing system controlled by decisions based on partial state information. The motivation for this work stems from road traffic, in which drivers may, or may not, be subscribed to a smartphone application for dynamic route planning. Our model consists of two queues with independent 13. Routing policies for a partially observable two-server queueing system NARCIS (Netherlands) W. Ellens; P. Kovacs; J.L. van den Berg (Hans); R. Núñez Queija (Rudesindo); A. Busic; M. Gribaudo; P. Reinecke 2015-01-01 htmlabstractWe consider a queueing system controlled by decisions based on partial state information. The motivation for this work stems from road traffic, in which drivers may, or may not, be subscribed to a smartphone application for dynamic route planning. Our model consists of two queues 14. Analysis of the asymmetric shortest queue problem : part 2: numerical analysis NARCIS (Netherlands) Adan, I.J.B.F.; Wessels, J.; Zijm, W.H.M. 1990-01-01 In this paper we study a system consisting of two parallel servers with different service rates. Jobs arrive according to a Poisson stream and generate an exponentially distributed workload. On arrival a job joins the shortest queue and in case both queues have equal lengths, he joins the first 15. Efficient Heuristics for the Simulation of Buffer Overflow in Series and Parallel Queueing Networks NARCIS (Netherlands) Nicola, V.F.; Zaburnenko, T.S. 2006-01-01 In this paper we propose state-dependent importance sampling heuristics to estimate the probability of population overï¬‚ow in Markovian networks of series and parallel queues. These heuristics capture state-dependence along the boundaries (when one or more queues are empty) which is critical for 16. Two coupled Lévy queues with independent input OpenAIRE Jevgenijs Ivanovs; Onno Boxma 2014-01-01 We consider a pair of coupled queues driven by independent spectrally-positive Lévy processes. With respect to the bi-variate workload process this framework includes both the coupled processor model and the two-server fluid network with independent Lévy inputs. We identify the joint transform of the stationary workload distribution in terms of Wiener-Hopf factors corresponding to two auxiliary Lévy processes with explicit Laplace exponents. We reinterpret and extend the ideas of Cohen and Bo... 17. Correlations in Output and Overflow Traffic Processes in Simple Queues Directory of Open Access Journals (Sweden) Don McNickle 2007-01-01 Full Text Available We consider some simple Markov and Erlang queues with limited storage space. Although the departure processes from some such systems are known to be Poisson, they actually consist of the superposition of two complex correlated processes, the overflow process and the output process. We measure the cross-correlation between the counting processes for these two processes. It turns out that this can be positive, negative, or even zero (without implying independence. The models suggest some general principles on how big these correlations are, and when they are important. This may suggest when renewal or moment approximations to similar processes will be successful, and when they will not. 18. Selected International Definitions about Young Students' Leisure Time: Theoretical and Practical Background in Poland Science.gov (United States) Janicka-Panek, Teresa 2017-01-01 Terms such as recreation, leisure, functions of spare time, physical hygiene, mental hygiene or forms of spare time are among the issues discussed in the branch of educational science. The majority of educationalists are convinced that the issue of active leisure should form part of the core curriculum and should be an objective of education in… 19. System-theoretic analysis of due-time performance in production systems Directory of Open Access Journals (Sweden) David Jacobs 1995-01-01 Full Text Available Along with the average production rate, the due-time performance is an important characteristic of manufacturing systems. Unlike the production rate, the due-time performance has received relatively little attention in the literature, especially in the context of large volume production. This paper is devoted to this topic. Specifically, the notion of due-time performance is formalized as the probability that the number of parts produced during the shipping period reaches the required shipment size. This performance index is analyzed for both lean and mass manufacturing environments. In particular, it is shown that, to achieve a high due-time performance in a lean environment, the production system should be scheduled for a sufficiently small fraction of its average production rate. In mass production, due-time performance arbitrarily close to one can be achieved for any scheduling practice, up to the average production rate. 20. On the Nonsymmetric Longer Queue Model: Joint Distribution, Asymptotic Properties, and Heavy Traffic Limits Directory of Open Access Journals (Sweden) Charles Knessl 2013-01-01 Full Text Available We consider two parallel queues, each with independent Poisson arrival rates, that are tended by a single server. The exponential server devotes all of its capacity to the longer of the queues. If both queues are of equal length, the server devotes ν of its capacity to the first queue and the remaining 1−ν to the second. We obtain exact integral representations for the joint probability distribution of the number of customers in this two-node network. Then we evaluate this distribution in various asymptotic limits, such as large numbers of customers in either/both of the queues, light traffic where arrivals are infrequent, and heavy traffic where the system is nearly unstable. 1. Request queues for interactive clients in a shared file system of a parallel computing system Science.gov (United States) Bent, John M.; Faibish, Sorin 2015-08-18 Interactive requests are processed from users of log-in nodes. A metadata server node is provided for use in a file system shared by one or more interactive nodes and one or more batch nodes. The interactive nodes comprise interactive clients to execute interactive tasks and the batch nodes execute batch jobs for one or more batch clients. The metadata server node comprises a virtual machine monitor; an interactive client proxy to store metadata requests from the interactive clients in an interactive client queue; a batch client proxy to store metadata requests from the batch clients in a batch client queue; and a metadata server to store the metadata requests from the interactive client queue and the batch client queue in a metadata queue based on an allocation of resources by the virtual machine monitor. The metadata requests can be prioritized, for example, based on one or more of a predefined policy and predefined rules. 2. A survey on queues in machining system: Progress from 2010 to 2017 Directory of Open Access Journals (Sweden) Shekhar C. 2017-01-01 Full Text Available The aim of the present article is to give a historical survey of some important research works related to queues in machining system since 2010. Queues of failed machines in machine repairing problem occur due to the failure of machines at random in the manufacturing industries, where different jobs are performed on machining stations. Machines are subject to failure what may result in significant loss of production, revenue, or goodwill. In addition to the references on queues in machining system, which is also called Machine Repair Problem' (MRP or Machine Interference Problem' (MIP, a meticulous list of books and survey papers is also prepared so as to provide a detailed catalog for understanding the research in queueing domain. We have classified the relevant literature according to a year of publishing, methodological, and modeling aspects. The author(s hope that this survey paper could be of help to learners contemplating research on queueing domain. 3. Impact source identification in finite isotropic plates using a time-reversal method: theoretical study International Nuclear Information System (INIS) Chen, Chunlin; Yuan, Fuh-Gwo 2010-01-01 This paper aims to identify impact sources on plate-like structures based on the synthetic time-reversal (T-R) concept using an array of sensors. The impact source characteristics, namely, impact location and impact loading time history, are reconstructed using the invariance of time-reversal concept, reciprocal theory, and signal processing algorithms. Numerical verification for two finite isotropic plates under low and high velocity impacts is performed to demonstrate the versatility of the synthetic T-R method for impact source identification. The results show that the impact location and time history of the impact force with various shapes and frequency bands can be readily obtained with only four sensors distributed around the impact location. The effects of time duration and the inaccuracy in the estimated impact location on the accuracy of the time history of the impact force using the T-R method are investigated. Since the T-R technique retraces all the multi-paths of reflected waves from the geometrical boundaries back to the impact location, it is well suited for quantifying the impact characteristics for complex structures. In addition, this method is robust against noise and it is suggested that a small number of sensors is sufficient to quantify the impact source characteristics through simple computation; thus it holds promise for the development of passive structural health monitoring (SHM) systems for impact monitoring in near real-time 4. Time-dependent theoretical model of the polar wind: Preliminary results International Nuclear Information System (INIS) Gombosi, T.I.; Cravens, T.E.; Nagy, A.F. 1985-01-01 The coupled time dependent continuity, momentum and energy equations of a two ion (O + and H + ) quasineutral plasma were solved in order to extend our understanding of polar wind behavior. This numerical code allows studies of the time dependent behavior of polar wind-type flows into and out of the ionosphere. Initial studies indicate that the typical time constants for electron and ion temperature changes are of the order of minutes and tens of minutes, respectively. The response time of the minor high altitude ion O + is less than an hour, whereas that of the major ion, H + , is many hours. The initial test runs also demonstrate the fact that temporary supersonic flows of both O + and H + are possible, especially in the presence of significant ion heating 5. Theoretical implications of quantitative properties of interval timing and probability estimation in mouse and rat. Science.gov (United States) Kheifets, Aaron; Freestone, David; Gallistel, C R 2017-07-01 In three experiments with mice ( Mus musculus ) and rats (Rattus norvigicus), we used a switch paradigm to measure quantitative properties of the interval-timing mechanism. We found that: 1) Rodents adjusted the precision of their timed switches in response to changes in the interval between the short and long feed latencies (the temporal goalposts). 2) The variability in the timing of the switch response was reduced or unchanged in the face of large trial-to-trial random variability in the short and long feed latencies. 3) The adjustment in the distribution of switch latencies in response to changes in the relative frequency of short and long trials was sensitive to the asymmetry in the Kullback-Leibler divergence. The three results suggest that durations are represented with adjustable precision, that they are timed by multiple timers, and that there is a trial-by-trial (episodic) record of feed latencies in memory. © 2017 Society for the Experimental Analysis of Behavior. 6. Theoretical study of time-dependent, ultrasound-induced acoustic streaming in microchannels. Science.gov (United States) Muller, Peter Barkholt; Bruus, Henrik 2015-12-01 Based on first- and second-order perturbation theory, we present a numerical study of the temporal buildup and decay of unsteady acoustic fields and acoustic streaming flows actuated by vibrating walls in the transverse cross-sectional plane of a long straight microchannel under adiabatic conditions and assuming temperature-independent material parameters. The unsteady streaming flow is obtained by averaging the time-dependent velocity field over one oscillation period, and as time increases, it is shown to converge towards the well-known steady time-averaged solution calculated in the frequency domain. Scaling analysis reveals that the acoustic resonance builds up much faster than the acoustic streaming, implying that the radiation force may dominate over the drag force from streaming even for small particles. However, our numerical time-dependent analysis indicates that pulsed actuation does not reduce streaming significantly due to its slow decay. Our analysis also shows that for an acoustic resonance with a quality factor Q, the amplitude of the oscillating second-order velocity component is Q times larger than the usual second-order steady time-averaged velocity component. Consequently, the well-known criterion v(1)≪c(s) for the validity of the perturbation expansion is replaced by the more restrictive criterion v(1)≪c(s)/Q. Our numerical model is available as supplemental material in the form of comsol model files and matlab scripts. 7. Delay Variation Model with Two Service Queues Directory of Open Access Journals (Sweden) Filip Rezac 2010-01-01 Full Text Available Delay in VoIP technology is very unpleasant issue and therefore a voice packets prioritization must be ensured. To maintain the high call quality a maximum information delivery time from the sender to the recipient is set to 150 ms. This paper focuses on the design of a mathematical model of end-to-end delay of a VoIP connection, in particular on a delay variation. It describes all partial delay components and mechanisms, their generation, facilities and mathematical formulations. A new approach to the delay variation model is presented and its validation has been done by experimention. 8. Theoretical restrictions on longest implicit time scales in Markov state models of biomolecular dynamics Science.gov (United States) Sinitskiy, Anton V.; Pande, Vijay S. 2018-01-01 Markov state models (MSMs) have been widely used to analyze computer simulations of various biomolecular systems. They can capture conformational transitions much slower than an average or maximal length of a single molecular dynamics (MD) trajectory from the set of trajectories used to build the MSM. A rule of thumb claiming that the slowest implicit time scale captured by an MSM should be comparable by the order of magnitude to the aggregate duration of all MD trajectories used to build this MSM has been known in the field. However, this rule has never been formally proved. In this work, we present analytical results for the slowest time scale in several types of MSMs, supporting the above rule. We conclude that the slowest implicit time scale equals the product of the aggregate sampling and four factors that quantify: (1) how much statistics on the conformational transitions corresponding to the longest implicit time scale is available, (2) how good the sampling of the destination Markov state is, (3) the gain in statistics from using a sliding window for counting transitions between Markov states, and (4) a bias in the estimate of the implicit time scale arising from finite sampling of the conformational transitions. We demonstrate that in many practically important cases all these four factors are on the order of unity, and we analyze possible scenarios that could lead to their significant deviation from unity. Overall, we provide for the first time analytical results on the slowest time scales captured by MSMs. These results can guide further practical applications of MSMs to biomolecular dynamics and allow for higher computational efficiency of simulations. 9. Computation of a near-optimal service policy for a single-server queue with homogeneous jobs DEFF Research Database (Denmark) Johansen, Søren Glud; Larsen, Christian 2001-01-01 We present an algorithm for computing a near-optimal service policy for a single-server queueing system when the service cost is a convex function of the service time. The policy has state-dependent service times, and it includes the options to remove jobs from the system and to let the server...... be off. The systems' semi-Markov decision model has infinite action sets for the positive states. We design a new tailor-made policy-iteration algorithm for computing a policy for which the long-run average cost is at most a positive tolerance above the minimum average cost. For any positive tolerance... 10. Computation of a near-optimal service policy for a single-server queue with homogeneous jobs DEFF Research Database (Denmark) Johansen, Søren Glud; Larsen, Christian 2000-01-01 We present an algorithm for computing a near optimal service policy for a single-server queueing system when the service cost is a convex function of the service time. The policy has state-dependent service times, and it includes the options to remove jobs from the system and to let the server...... be off. The system's semi-Markov decision model has infinite action sets for the positive states. We design a new tailor-made policy iteration algorithm for computing a policy for which the long-run average cost is at most a positive tolerance above the minimum average cost. For any positive tolerance... 11. Theoretical determination of transit time locus curves for ultrasonic pulse echo testing - ALOK. Pt. 4 International Nuclear Information System (INIS) Grohs, B. 1983-01-01 The ALOK-technique allows the simultaneous detection of flaws and their evaluation with respect to type, location and dimension by interpretation of the transit time behaviour during scanning of the reflector. The accuracy of information obtained by means of this technique can be further improved both during interference elimination and reconstruction owing to the ability of exact calculation of possible transit time locus curves of given reflectors. The mathematical solution of transit time locus curve calculations refers here to pulse echo testing in consideration of the refraction of sound on the forward wedge/test object - interface. The method of solving the problem is equivalent to the Fermat's principle in optics. (orig.) [de 12. ANALYSIS OF MULTI-SERVER QUEUEING SYSTEM WITH PREEMPTIVE PRIORITY AND REPEATED CALLS Directory of Open Access Journals (Sweden) S. A. Dudin 2015-01-01 Full Text Available Multi-server retrial queueing system with no buffer and two types of customers is analyzed as the model of cognitive radio system. Customers of type 1 have a preemptive priority. Customers of both types arrive according to Markovian Arrival Processes. Service times have exponential distribution with parameter depending on the customer type. Type 2 customers are admitted for service only if the number of busy servers is less than the predefined threshold. The rejected type 2 customers retry for the service. Existence condition of the stationary mode of system operation is derived. Formulas for computing key performance measures of the system are presented. 13. STATIONARY DISTRIBUTION OF A TANDEM QUEUE WITH ADDITIONAL FLOWS ON THE STATIONS OF THE TANDEM Directory of Open Access Journals (Sweden) V. I. Klimenok 2017-01-01 Full Text Available A tandem queueing system consisting of a finite number of multi-server stations without buffers is analized. The input flow at the first station is a ???????????? (Markovian arrival process. The customers from this flow aim to be served at all stations of the tandem. For any station, besides transit customers proceeding from the previous station, an additional ???????????? flow of new customers arrives at this station directly. Customers from this flow aim to be served at this station and all subsequent stations of the tandem. The service times of customer at the stations are exponentially distributed with the service rate depending of number of the station. The algorithms for culculation of stationary distributions and the loss probabilities associated with the tandem are given. 14. Worst-case efficient external-memory priority queues DEFF Research Database (Denmark) Brodal, Gerth Stølting; Katajainen, Jyrki 1998-01-01 A priority queue Q is a data structure that maintains a collection of elements, each element having an associated priority drawn from a totally ordered universe, under the operations Insert, which inserts an element into Q, and DeleteMin, which deletes an element with the minimum priority from Q....... In this paper a priority-queue implementation is given which is efficient with respect to the number of block transfers or I/Os performed between the internal and external memories of a computer. Let B and M denote the respective capacity of a block and the internal memory measured in elements. The developed...... data structure handles any intermixed sequence of Insert and DeleteMin operations such that in every disjoint interval of B consecutive priorityqueue operations at most clogM/B N/M I/Os are performed, for some positive constant c. These I/Os are divided evenly among the operations: if B ≥ clogM/B N... 15. Upper Bound for Queue length in Regulated Burst Service Scheduling Directory of Open Access Journals (Sweden) Mahmood Daneshvar Farzanegan 2016-01-01 Full Text Available Quality of Service (QoS provisioning is very important in next computer/communication networks because of increasing multimedia services. Hence, very investigations are performed in this area. Scheduling algorithms effect QoS provisioning. Lately, a scheduling algorithm called Regulated Burst Service Scheduling (RBSS suggested by author in [1] to provide a better service to bursty and delay sensitive services such as video. One of the most significant feature in RBSS is considering burstiness of arrival traffic in scheduling algorithm. In this paper, an upper bound of queue length or buffer size and service curve are calculated by Network Calculus analysis for RBSS. Because in RBSS queue length is a parameter that is considered in scheduling arbitrator, analysis results a differential inequality to obtain service curve. To simplify, arrival traffic is assumed to be linear that is defined in the paper clearly. This paper help to analysis delay in RBSS for different traffic with different specifications. Therefore, QoS provisioning will be evaluated. 16. Theoretical Time Dependent Thermal Neutron Spectra and Reaction Rates in H2O and D2O International Nuclear Information System (INIS) Purohit, S.N. 1966-04-01 The early theoretical and experimental time dependent neutron thermalization studies were limited to the study of the transient spectrum in the diffusion period. The recent experimental measurements of the time dependent thermal neutron spectra and reaction rates, for a number of moderators, have generated considerable interest in the study of the time dependent Boltzmann equation. In this paper we present detailed results for the time dependent spectra and the reaction rates for resonance detectors using several scattering models of H 2 O and D 2 O. This study has been undertaken in order to interpret the integral time dependent neutron thermalization experiments in liquid moderators which have been performed at the AB Atomenergi. The proton gas and the deuteron gas models are inadequate to explain the measured reaction rates in H 2 O and D 2 O. The bound models of Nelkin for H 2 O and of Butler for D 2 O give much better agreement with the experimental results than the gas models. Nevertheless, some disagreement between theoretical and experimental results still persists. This study also indicates that the bound model of Butler and the effective mass 3. 6 gas model of Brown and St. John give almost identical reaction rates. It is also surprising to note that the calculated reaction rate for Cd for the Butler model appears to be in better agreement with the experimental results of D 2 O than of the Nelkin model with H 2 O experiments. The present reaction rate studies are sensitive enough so as to distinguish between the gas model and the bound model of a moderator. However, to investigate the details of a scattering law (such as the effect of the hindered rotations in H 2 O and D 2 O and the weights of different dynamical modes) with the help of these studies would require further theoretical as well as experimental investigations. Theoretical results can be further improved by improving the source for thermal neutrons, the group structure and the scattering 17. Theoretical treatment of photodissociation of water by time-dependent quantum mechanical methods International Nuclear Information System (INIS) Weide, K. 1993-01-01 An algorithm for wavepacket propagation, based on Kosloff's method of expansion of the time evolution operator in terms of Chebychev polynomials, and some details of its implementation are described. With the programs developed, quantum-mechanical calculations for up to three independent molecular coordinates are possible and feasible and therefore photodissociation of non-rotating triatomic molecules can be treated exactly. The angular degree of freedom here is handled by expansion in terms of free diatomic rotor states. The time-dependent wave packet picture is compared with the more traditional view of stationary wave functions, and both are used to interpret computational results where appropriate. Two-dimensional calculations have been performed to explain several experimental observations about water photodissociation. All calculations are based on ab initio potential energy surfaces, and it is explained in each case why it is reasonable to neglect the third degree of freedom. Many experimental results are reproduced quantitatively. (orig.) [de 18. THEORETICAL RESEARCH ON HYDRODYNAMICS OF A GEOMETRIC SPAR IN FREQUENCY- AND TIME-DOMAINS Institute of Scientific and Technical Information of China (English) WANG Ying; YANG Jian-min; HU Zhi-qiang; XIAO Long-fei 2008-01-01 Considering the coupling effects of the vessel and its riser and mooring system, hydrodynamic analyses of a geometric spar were performed both in frequency- and time-domains. Based on the boundary element method, the 3-D panel model of the geometric spar and the related free water surface model were established, and the first-order and second-order difference-frequency wave loads and other hydrodynamic coefficients were calculated. Frequency domain analysis of the motion Response Amplitude Operators (RAO) and Quadratic Transfer Functions (QTF) and time domain analysis of the response series and spectra in an extreme wave condition were conducted for the coupled system with the mooring lines and risers involved. These analyses were further validated by the physical model test results. 19. Time Analysis of Building Dynamic Response Under Seismic Action. Part 1: Theoretical Propositions Science.gov (United States) Ufimtcev, E. M. 2017-11-01 The first part of the article presents the main provisions of the analytical approach - the time analysis method (TAM) developed for the calculation of the elastic dynamic response of rod structures as discrete dissipative systems (DDS) and based on the investigation of the characteristic matrix quadratic equation. The assumptions adopted in the construction of the mathematical model of structural oscillations as well as the features of seismic forces’ calculating and recording based on the data of earthquake accelerograms are given. A system to resolve equations is given to determine the nodal (kinematic and force) response parameters as well as the stress-strain state (SSS) parameters of the system’s rods. 20. Theoretical foundation for the discrete dynamics of physicochemical systems: Chaos, self-organization, time and space in complex systems Directory of Open Access Journals (Sweden) V. Gontar 1997-01-01 Full Text Available A new theoretical foundation for the discrete dynamics of physicochemical systems is presented. Based on the analogy between the π-theorem of the theory of dimensionality, the second law of thermodynamics and the stoichiometry of complex physicochemical reactions, basic dynamic equations and an extreme principle were formulated. The meaning of discrete time and space in the proposed equations is discussed. Some results of numerical calculations are presented to demonstrate the potential of the proposed approach to the mathematical simulation of spatiotemporal physicochemical reaction dynamics. 1. Infinite Queue Management via Cascade Control for Industrial Routers in Smart Grid IP Networks Directory of Open Access Journals (Sweden) Ku-Hwan Kim 2016-01-01 Full Text Available Smart grid applications experience an extremely wide range of communication delay. Data flows of those applications are normally aggregated at industrial network routers in substations, form infinite (long queues termed bufferbloat issue, and might damage the operation of transmission control protocol. The default queue management scheme, DropTail, in such routers just drops packets if queue is full while the others in literature are mostly based on one-loop feedback control where an optimal point of performance between queue length and drop rate is limited. In this paper, we study the problem of managing a long queue of industrial router at substation under heterogeneous smart grid networks. Specifically, we propose an enqueue-dequeue dropping cascade control using a two-loop design method to control both window size and queue length. Moreover, our proposal can be easily implemented into router firmware with provided discrete expressions. Finally, our simulation results are presented to validate the possible benefits that can be gained from cascade control and compare the existing queue management methods as well. 2. M/M/1 RETRIAL QUEUEING SYSTEM WITH VACATION INTERRUPTIONS UNDER PRE-EMPTIVE PRIORITY SERVICE Directory of Open Access Journals (Sweden) Muthu Ganapathi Subramanian Annasamy 2010-10-01 Full Text Available Consider a single server retrial queueing system with pre-emptive priority service and vacation interruptions in which customers arrive in a Poisson process with arrival rate λ1 for low priority customers and λ2 for high priority customers. Further it is assume that the service times follow an exponential distribution with parameters μ1 and μ2 for low and high priority customers respectively. The retrial is introduced for low priority customers only. The server goes for vacation after exhaustively completing the service to both types of customers. The vacation rate follows an exponential distribution with parameter α. The concept of vacation interruption is used in this paper that is the server comes from the vacation into normal working condition without completing his vacation period subject to some conditions. Let k be the maximum number of waiting spaces for high priority customers in front of the service station. The high priority customers will be governed by the pre-emptive priority service. We assume that the access from orbit to the service facility is governed by the classical retrial policy. This model is solved by using Matrix geometric Technique. Numerical study have been done for Analysis of Mean number of low priority customers in the orbit (MNCO, Mean number of high priority customers in the queue(MPQL,Truncation level (OCUT,Probability of server free and Probabilities of server busy with low and high priority customers and probability of server in vacation for various values of λ1 , λ2 , μ1 , μ2, α and σ in elaborate manner and also various particular cases of this model have been discussed. 3. Performance Evaluation of a M/Geo[xy]/1 Queue with varying probabilities of success which Treats Two Like Jobs As a Single Entity Science.gov (United States) Gowrishankar, Lavanya; Bhaskar, Vidhyacharan; Sundarammal, K. 2018-04-01 The developed model comprises of a single server capable of handling two different job types X and Y type job. Job Y takes more time for execution than job X. The objective is to construct a single server which would replace the standard M/M/2 queuing model The method used to find the relative measures involves the cost equation. The properties of the service distribution are discussed in detail. The maximum likelihood estimates for the parameters are obtained. The results are analytically derived for the M/Geo[xy]/1 model. A comparison is done between the model proposed and the standard M/M/2 queue. From the numerical results, it is observed that the waiting time in queue increases as the number of cycles is increased but however it is more economical than the M/M/2 model with restriction on the number of time slices. 4. Graphene-Based FET Detector for E. coli K12 Real-Time Monitoring and Its Theoretical Analysis Directory of Open Access Journals (Sweden) Jieyi Zhu 2016-01-01 Full Text Available This paper presents a theoretical analysis for a graphene-based FET real-time detector of the target bacteria E. coli K12. The motivation for this study is to design a sensor device for detection of bacteria in food and water in order to guarantee food safety. Graphene is chosen as our material for sensor design, which has outstanding electrical, physical, and optical performance. In our sensor structure, graphene-based solution gate field effect transistor (FET is the device model; fabrication and functionalization protocol are presented together in this paper. What is more, a real-time signal display system is the accompanied equipment for our designed biosensor device. In this system, the sensor bias current signal Ids would change obviously when the target bacteria are attached to the sensor surface. And the bias current Ids increases when the E. coli concentration increases. In the latter part, a theoretical interpretation of the sensor signal is to explain the bias current Ids increasing after the E. coli K12 attachment. 5. Ultrasound waiting lists: rational queue or extended capacity? Science.gov (United States) Brasted, Christopher 2008-06-01 The features and issues regarding clinical waiting lists in general and general ultrasound waiting lists in particular are reviewed, and operational aspects of providing a general ultrasound service are also discussed. A case study is presented describing a service improvement intervention in a UK NHS hospital's ultrasound department, from which arises requirements for a predictive planning model for an ultrasound waiting list. In the course of this, it becomes apparent that a booking system is a more appropriate way of describing the waiting list than a conventional queue. Distinctive features are identified from the literature and the case study as the basis for a predictive model, and a discrete event simulation model is presented which incorporates the distinctive features. 6. Real-time feedback on nonverbal clinical communication. Theoretical framework and clinician acceptance of ambient visual design. Science.gov (United States) Hartzler, A L; Patel, R A; Czerwinski, M; Pratt, W; Roseway, A; Chandrasekaran, N; Back, A 2014-01-01 This article is part of the focus theme of Methods of Information in Medicine on "Pervasive Intelligent Technologies for Health". Effective nonverbal communication between patients and clinicians fosters both the delivery of empathic patient-centered care and positive patient outcomes. Although nonverbal skill training is a recognized need, few efforts to enhance patient-clinician communication provide visual feedback on nonverbal aspects of the clinical encounter. We describe a novel approach that uses social signal processing technology (SSP) to capture nonverbal cues in real time and to display ambient visual feedback on control and affiliation--two primary, yet distinct dimensions of interpersonal nonverbal communication. To examine the design and clinician acceptance of ambient visual feedback on nonverbal communication, we 1) formulated a model of relational communication to ground SSP and 2) conducted a formative user study using mixed methods to explore the design of visual feedback. Based on a model of relational communication, we reviewed interpersonal communication research to map nonverbal cues to signals of affiliation and control evidenced in patient-clinician interaction. Corresponding with our formulation of this theoretical framework, we designed ambient real-time visualizations that reflect variations of affiliation and control. To explore clinicians' acceptance of this visual feedback, we conducted a lab study using the Wizard-of-Oz technique to simulate system use with 16 healthcare professionals. We followed up with seven of those participants through interviews to iterate on the design with a revised visualization that addressed emergent design considerations. Ambient visual feedback on non- verbal communication provides a theoretically grounded and acceptable way to provide clinicians with awareness of their nonverbal communication style. We provide implications for the design of such visual feedback that encourages empathic patient 7. Synchronization as a biological, psychological and social mechanism to create common time: A theoretical frame and a single case study. Science.gov (United States) Bao, Yan; Pöppel, Ernst; Wang, Lingyan; Lin, Xiaoxiong; Yang, Taoxi; Avram, Mihai; Blautzik, Janusch; Paolini, Marco; Silveira, Sarita; Vedder, Aline; Zaytseva, Yuliya; Zhou, Bin 2015-12-01 Synchronizing neural processes, mental activities, and social interactions is considered to be fundamental for the creation of temporal order on the personal and interpersonal level. Several different types of synchronization are distinguished, and for each of them examples are given: self-organized synchronizations on the neural level giving rise to pre-semantically defined time windows of some tens of milliseconds and of approximately 3 s; time windows that are created by synchronizing different neural representations, as for instance in aesthetic appreciations or moral judgments; and synchronization of biological rhythms with geophysical cycles, like the circadian clock with the 24-hr rhythm of day and night. For the latter type of synchronization, an experiment is described that shows the importance of social interactions for sharing or avoiding common time. In a group study with four subjects being completely isolated together for 3 weeks from the external world, social interactions resulted both in intra- and interindividual circadian synchronization and desynchronization. A unique phenomenon in circadian regulation is described, the "beat phenomenon," which has been made visible by the interaction of two circadian rhythms with different frequencies in one body. The separation of the two physiological rhythms was the consequence of social interactions, that is, by the desire of a subject to share and to escape common time during different phases of the long-term experiment. The theoretical arguments on synchronization are summarized with the general statement: "Nothing in cognitive science makes sense except in the light of time windows." The hypothesis is forwarded that time windows that express discrete timing mechanisms in behavioral control and on the level of conscious experiences are the necessary bases to create cognitive order, and it is suggested that time windows are implemented by neural oscillations in different frequency domains. © 2015 The 8. Fast distributed strategic learning for global optima in queueing access games KAUST Repository Tembine, Hamidou 2014-01-01 In this paper we examine combined fully distributed payoff and strategy learning (CODIPAS) in a queue-aware access game over a graph. The classical strategic learning analysis relies on vanishing or small learning rate and uses stochastic 9. Technical report on prototype intelligent network flow optimization (INFLO) dynamic speed harmonization and queue warning. Science.gov (United States) 2015-06-01 This Technical Report on Prototype Intelligent Network Flow Optimization (INFLO) Dynamic Speed Harmonization and : Queue Warning is the final report for the project. It describes the prototyping, acceptance testing and small-scale : demonstration of ... 10. Computing a constrained control policy for a single-server queueing system DEFF Research Database (Denmark) Larsen, Christian We consider a single-server queueing system designed to serve homogeneous jobs. The jobs arrive to the system after a Poisson process and all processing times are deterministic. There is a set-up cost for starting up production and a holding cost rate is incurred for each job present. Also......, there is a service cost per job, which is a convex function of the service time. The control policy specifies when the server is on or off. It also specifies the state-dependent processing times. In order to avoid a very detailed control policy (which could be hard to implement) we will only allow the server to use...... n different processing times. Hence, we must subdivide the infinite state space into n disjoint sets and for each set decide which processing time to use. We show how to derive a mathematical expression for the long-run average cost per time unit. We also present an algorithm to find the optimal... 11. Fluid queues driven by a birth and death process with alternating flow rates OpenAIRE P. R. Parthasarathy; K. V. Vijayashree; R. B. Lenin 2004-01-01 Fluid queue driven by a birth and death process (BDP) with only one negative effective input rate has been considered in the literature. As an alternative, here we consider a fluid queue in which the input is characterized by a BDP with alternating positive and negative flow rates on a finite state space. Also, the BDP has two alternating arrival rates and two alternating service rates. Explicit expression for the distribution function of the buffer occupancy is obtained. The case where the s... 12. New theoretical approaches to atomic and molecular dynamics triggered by ultrashort light pulses on the atto- to picosecond time scale International Nuclear Information System (INIS) Pabst, Stefan Ulf 2013-04-01 The concept of atoms as the building blocks of matter has existed for over 3000 years. A revolution in the understanding and the description of atoms and molecules has occurred in the last century with the birth of quantum mechanics. After the electronic structure was understood, interest in studying the dynamics of electrons, atoms, and molecules increased. However, time-resolved investigations of these ultrafast processes were not possible until recently. The typical time scale of atomic and molecular processes is in the picosecond to attosecond realm. Tremendous technological progress in recent years makes it possible to generate light pulses on these time scales. With such ultrashort pulses, atomic and molecular dynamics can be triggered, watched, and controlled. Simultaneously, the need rises for theoretical models describing the underlying mechanisms. This doctoral thesis focuses on the development of theoretical models which can be used to study the dynamical behavior of electrons, atoms, and molecules in the presence of ultrashort light pulses. Several examples are discussed illustrating how light pulses can trigger and control electronic, atomic, and molecular motions. In the first part of this work, I focus on the rotational motion of asymmetric molecules, which happens on picosecond and femtosecond time scales. Here, the aim is to align all three axes of the molecule as well as possible. To investigate theoretically alignment dynamics, I developed a program that can describe alignment motion ranging from the impulsive to the adiabatic regime. The asymmetric molecule SO 2 is taken as an example to discuss strategies of optimizing 3D alignment without the presence of an external field (i.e., field-free alignment). Field-free alignment is particularly advantageous because subsequent experiments on the aligned molecule are not perturbed by the aligning light pulse. Wellaligned molecules in the gas phase are suitable for diffraction experiments. From the 13. New theoretical approaches to atomic and molecular dynamics triggered by ultrashort light pulses on the atto- to picosecond time scale Energy Technology Data Exchange (ETDEWEB) Pabst, Stefan Ulf 2013-04-15 The concept of atoms as the building blocks of matter has existed for over 3000 years. A revolution in the understanding and the description of atoms and molecules has occurred in the last century with the birth of quantum mechanics. After the electronic structure was understood, interest in studying the dynamics of electrons, atoms, and molecules increased. However, time-resolved investigations of these ultrafast processes were not possible until recently. The typical time scale of atomic and molecular processes is in the picosecond to attosecond realm. Tremendous technological progress in recent years makes it possible to generate light pulses on these time scales. With such ultrashort pulses, atomic and molecular dynamics can be triggered, watched, and controlled. Simultaneously, the need rises for theoretical models describing the underlying mechanisms. This doctoral thesis focuses on the development of theoretical models which can be used to study the dynamical behavior of electrons, atoms, and molecules in the presence of ultrashort light pulses. Several examples are discussed illustrating how light pulses can trigger and control electronic, atomic, and molecular motions. In the first part of this work, I focus on the rotational motion of asymmetric molecules, which happens on picosecond and femtosecond time scales. Here, the aim is to align all three axes of the molecule as well as possible. To investigate theoretically alignment dynamics, I developed a program that can describe alignment motion ranging from the impulsive to the adiabatic regime. The asymmetric molecule SO{sub 2} is taken as an example to discuss strategies of optimizing 3D alignment without the presence of an external field (i.e., field-free alignment). Field-free alignment is particularly advantageous because subsequent experiments on the aligned molecule are not perturbed by the aligning light pulse. Wellaligned molecules in the gas phase are suitable for diffraction experiments. From the 14. Performance Analysis and Optimal Allocation of Layered Defense M/M/N Queueing Systems Directory of Open Access Journals (Sweden) Longyue Li 2016-01-01 Full Text Available One important mission of strategic defense is to develop an integrated layered Ballistic Missile Defense System (BMDS. Motivated by the queueing theory, we presented a work for the representation, modeling, performance simulation, and channels optimal allocation of the layered BMDS M/M/N queueing systems. Firstly, in order to simulate the process of defense and to study the Defense Effectiveness (DE, we modeled and simulated the M/M/N queueing system of layered BMDS. Specifically, we proposed the M/M/N/N and M/M/N/C queueing model for short defense depth and long defense depth, respectively; single target channel and multiple target channels were distinguished in each model. Secondly, we considered the problem of assigning limited target channels to incoming targets, we illustrated how to allocate channels for achieving the best DE, and we also proposed a novel and robust search algorithm for obtaining the minimum channel requirements across a set of neighborhoods. Simultaneously, we presented examples of optimal allocation problems under different constraints. Thirdly, several simulation examples verified the effectiveness of the proposed queueing models. This work may help to understand the rules of queueing process and to provide optimal configuration suggestions for defense decision-making. 15. A novel fair active queue management algorithm based on traffic delay jitter Science.gov (United States) Wang, Xue-Shun; Yu, Shao-Hua; Dai, Jin-You; Luo, Ting 2009-11-01 In order to guarantee the quantity of data traffic delivered in the network, congestion control strategy is adopted. According to the study of many active queue management (AQM) algorithms, this paper proposes a novel active queue management algorithm named JFED. JFED can stabilize queue length at a desirable level by adjusting output traffic rate and adopting a reasonable calculation of packet drop probability based on buffer queue length and traffic jitter; and it support burst packet traffic through the packet delay jitter, so that it can traffic flow medium data. JFED impose effective punishment upon non-responsible flow with a full stateless method. To verify the performance of JFED, it is implemented in NS2 and is compared with RED and CHOKe with respect to different performance metrics. Simulation results show that the proposed JFED algorithm outperforms RED and CHOKe in stabilizing instantaneous queue length and in fairness. It is also shown that JFED enables the link capacity to be fully utilized by stabilizing the queue length at a desirable level, while not incurring excessive packet loss ratio. 16. Optimal Control for Bufferbloat Queue Management Using Indirect Method with Parametric Optimization Directory of Open Access Journals (Sweden) Amr Radwan 2016-01-01 Full Text Available Because memory buffers become larger and cheaper, they have been put into network devices to reduce the number of loss packets and improve network performance. However, the consequences of large buffers are long queues at network bottlenecks and throughput saturation, which has been recently noticed in research community as bufferbloat phenomenon. To address such issues, in this article, we design a forward-backward optimal control queue algorithm based on an indirect approach with parametric optimization. The cost function which we want to minimize represents a trade-off between queue length and packet loss rate performance. Through the integration of an indirect approach with parametric optimization, our proposal has advantages of scalability and accuracy compared to direct approaches, while still maintaining good throughput and shorter queue length than several existing queue management algorithms. All numerical analysis, simulation in ns-2, and experiment results are provided to solidify the efficiency of our proposal. In detailed comparisons to other conventional algorithms, the proposed procedure can run much faster than direct collocation methods while maintaining a desired short queue (≈40 packets in simulation and 80 (ms in experiment test. 17. A comprehensive study of the use of temporal moments in time-resolved diffuse optical tomography: part I. Theoretical material Energy Technology Data Exchange (ETDEWEB) Ducros, Nicolas; Herve, Lionel; Dinten, Jean-Marc [CEA, LETI, MINATEC, 17 rue des Martyrs, F-38054 Grenoble (France); Da Silva, Anabela [Institut Fresnel, CNRS UMR 6133, Universite Aix-Marseille, Ecole Centrale Marseille, Campus universitaire de Saint-Jerome, F-13013 Marseille (France); Peyrin, Francoise [CREATIS, INSERM U 630, CNRS UMR 5220, Universite de Lyon, INSA de Lyon, bat. Blaise Pascal, F-69621 Villeurbanne Cedex (France)], E-mail: nicolas.ducros@cea.fr 2009-12-07 The problem of fluorescence diffuse optical tomography consists in localizing fluorescent markers from near-infrared light measurements. Among the different available acquisition modalities, the time-resolved modality is expected to provide measurements of richer information content. To extract this information, the moments of the time-resolved measurements are often considered. In this paper, a theoretical analysis of the moments of the forward problem in fluorescence diffuse optical tomography is proposed for the infinite medium geometry. The moments are expressed as a function of the source, detector and markers positions as well as the optical properties of the medium and markers. Here, for the first time, an analytical expression holding for any moments order is mathematically derived. In addition, analytical expressions of the mean, variance and covariance of the moments in the presence of noise are given. These expressions are used to demonstrate the increasing sensitivity of moments to noise. Finally, the newly derived expressions are illustrated by means of sensitivity maps. The physical interpretation of the analytical formulae in conjunction with their map representations could provide new insights into the analysis of the information content provided by moments. 18. Analysis of an MAP/PH/1 Queue with Flexible Group Service Directory of Open Access Journals (Sweden) Brugno Arianna 2017-03-01 Full Text Available A novel customer batch service discipline for a single server queue is introduced and analyzed. Service to customers is offered in batches of a certain size. If the number of customers in the system at the service completion moment is less than this size, the server does not start the next service until the number of customers in the system reaches this size or a random limitation of the idle time of the server expires, whichever occurs first. Customers arrive according to a Markovian arrival process. An individual customer’s service time has a phase-type distribution. The service time of a batch is defined as the maximum of the individual service times of the customers which form the batch. The dynamics of such a system are described by a multi-dimensional Markov chain. An ergodicity condition for this Markov chain is derived, a stationary probability distribution of the states is computed, and formulas for the main performance measures of the system are provided. The Laplace–Stieltjes transform of the waiting time is obtained. Results are numerically illustrated. 19. Analysis of Queue-Length Dependent Vacations and P-Limited Service in BMAP/G/1/N Systems: Stationary Distributions and Optimal Control Directory of Open Access Journals (Sweden) A. D. Banik 2013-01-01 Full Text Available We consider a finite-buffer single server queueing system with queue-length dependent vacations where arrivals occur according to a batch Markovian arrival process (BMAP. The service discipline is P-limited service, also called E-limited with limit variation (ELV where the server serves until either the system is emptied or a randomly chosen limit of L customers has been served. Depending on the number of customers present in the system, the server will monitor his vacation times. Queue-length distributions at various epochs such as before, arrival, arbitrary and after, departure have been obtained. Several other service disciplines like Bernoulli scheduling, nonexhaustive service, and E-limited service can be treated as special cases of the P-limited service. Finally, the total expected cost function per unit time is considered to determine locally optimal values N* of N or a maximum limit L^* of L^ as the number of customers served during a service period at a minimum cost. 20. Steps in Designing Queue and Interview Process using Information System: A Case of Re-registration of New Students in Universitas Negeri Makassar Directory of Open Access Journals (Sweden) Ansari Saleh Ahmar 2016-06-01 Full Text Available Universitas Negeri Makassar (UNM have a number of prospective students is quite a lot. Based on data released by the BAPSI UNM (2015 that the data student candidates of UNM who passed the selection with SNMPTN SBMPTN selection as 3,791 people. If the prospective graduate students interviewed are normally it will take a long time and will certainly make students uncomfortable. Therefore it is necessary design an information systems to solving this problem. This research aim to develop an information system to facilitate the process queue. The method used in this research is to use the three stages in the Software Development Life Cycle method namely Initiation Phase, Development/Acquisition Phase, and Implementation Phase. This information system development using PHP and CodeIgniter as a its framework. This design results will be obtained an queues and interviews information system that can be used to manage the queue and interview data. By implementing this system, it potentially reduce time to wait and the process of managing results of interviews can be obtained directly without a process of inputting interview repeat if done manually. 1. Adaptation of the concept of varying time of concentration within flood modelling: Theoretical and empirical investigations across the Mediterranean Science.gov (United States) Michailidi, Eleni Maria; Antoniadi, Sylvia; Koukouvinos, Antonis; Bacchi, Baldassare; Efstratiadis, Andreas 2017-04-01 The time of concentration, tc, is a key hydrological concept and often is an essential parameter of rainfall-runoff modelling, which has been traditionally tackled as a characteristic property of the river basin. However, both theoretical proof and empirical evidence imply that tc is a hydraulic quantity that depends on flow, and thus it should be considered as variable and not as constant parameter. Using a kinematic method approach, easily implemented in GIS environment, we first illustrate that the relationship between tc and the effective rainfall produced over the catchment is well-approximated by a power-type law, the exponent of which is associated with the slope of the longest flow path of the river basin. Next, we take advantage of this relationship to adapt the concept of varying time of concentration within flood modelling, and particularly the well-known SCS-CN approach. In this context, the initial abstraction ratio is also considered varying, while the propagation of the effective rainfall is employed through a parametric unit hydrograph, the shape of which is dynamically adjusted according to the runoff produced during the flood event. The above framework is tested in a number of Mediterranean river basins in Greece, Italy and Cyprus, ensuring faithful representation of most of the observed flood events. Based on the outcomes of this extended analysis, we provide guidance for employing this methodology for flood design studies in ungauged basins. 2. Multiplexing real-time timed events NARCIS (Netherlands) Holenderski, M.J.; Cools, W.A.; Bril, R.J.; Lukkien, J.J. 2009-01-01 This paper presents the design and implementation of RELTEQ, a timed event management algorithm based on relative event times, supporting long event interarrival time, long lifetime of the event queue, no drift and low overhead. It is targeted at embedded operating systems. RELTEQ has been conceived 3. Model Predictive Control for the acquisition queue and related queueing networks NARCIS (Netherlands) Leeuwaarden, van J.S.H.; Lefeber, A.A.J.; Nazarathy, J.; Rooda, J.E. 2010-01-01 Model Predictive Control (MPC) is a well established method in control theory and engineering practice. It is often the method of choice for systems that need to be controlled in view of constraints. The main idea of MPC is to solve an optimization problem over a given time horizon at each control 4. A Multi-Objective Compounded Local Mobile Cloud Architecture Using Priority Queues to Process Multiple Jobs. Science.gov (United States) Wei, Xiaohui; Sun, Bingyi; Cui, Jiaxu; Xu, Gaochao 2016-01-01 As a result of the greatly increased use of mobile devices, the disadvantages of portable devices have gradually begun to emerge. To solve these problems, the use of mobile cloud computing assisted by cloud data centers has been proposed. However, cloud data centers are always very far from the mobile requesters. In this paper, we propose an improved multi-objective local mobile cloud model: Compounded Local Mobile Cloud Architecture with Dynamic Priority Queues (LMCpri). This new architecture could briefly store jobs that arrive simultaneously at the cloudlet in different priority positions according to the result of auction processing, and then execute partitioning tasks on capable helpers. In the Scheduling Module, NSGA-II is employed as the scheduling algorithm to shorten processing time and decrease requester cost relative to PSO and sequential scheduling. The simulation results show that the number of iteration times that is defined to 30 is the best choice of the system. In addition, comparing with LMCque, LMCpri is able to effectively accommodate a requester who would like his job to be executed in advance and shorten execution time. Finally, we make a comparing experiment between LMCpri and cloud assisting architecture, and the results reveal that LMCpri presents a better performance advantage than cloud assisting architecture. 5. A Multi-Objective Compounded Local Mobile Cloud Architecture Using Priority Queues to Process Multiple Jobs. Directory of Open Access Journals (Sweden) Xiaohui Wei Full Text Available As a result of the greatly increased use of mobile devices, the disadvantages of portable devices have gradually begun to emerge. To solve these problems, the use of mobile cloud computing assisted by cloud data centers has been proposed. However, cloud data centers are always very far from the mobile requesters. In this paper, we propose an improved multi-objective local mobile cloud model: Compounded Local Mobile Cloud Architecture with Dynamic Priority Queues (LMCpri. This new architecture could briefly store jobs that arrive simultaneously at the cloudlet in different priority positions according to the result of auction processing, and then execute partitioning tasks on capable helpers. In the Scheduling Module, NSGA-II is employed as the scheduling algorithm to shorten processing time and decrease requester cost relative to PSO and sequential scheduling. The simulation results show that the number of iteration times that is defined to 30 is the best choice of the system. In addition, comparing with LMCque, LMCpri is able to effectively accommodate a requester who would like his job to be executed in advance and shorten execution time. Finally, we make a comparing experiment between LMCpri and cloud assisting architecture, and the results reveal that LMCpri presents a better performance advantage than cloud assisting architecture. 6. The impact of aviation checkpoint queues on optimizing security screening effectiveness Energy Technology Data Exchange (ETDEWEB) Lee, Adrian J., E-mail: ajlee@citeri.or [Central Illinois Technology and Education Research Institute, 2312 Connie Drive, Springfield, IL 62704-8722 (United States); Jacobson, Sheldon H., E-mail: shj@illinois.ed [Department of Computer Science, University of Illinois at Urbana-Champaign, 201 N. Goodwin Ave. M/C 258, Urbana, IL 61801-2302 (United States) 2011-08-15 Passenger screening at aviation security checkpoints is a critical component in protecting airports and aircraft from terrorist threats. Recent developments in screening device technology have increased the ability to detect these threats; however, the average amount of time it takes to screen a passenger still remains a concern. This paper models the queueing process for a multi-level airport checkpoint security system, where multiple security classes are formed through subsets of specialized screening devices. An optimal static assignment policy is obtained which minimizes the steady-state expected amount of time a passenger spends in the security system. Then, an optimal dynamic assignment policy is obtained through a transient analysis that balances the expected number of true alarms with the expected amount of time a passenger spends in the security system. Performance of a two-class system is compared to that of a selective security system containing primary and secondary levels of screening. The key contribution is that the resulting optimal assignment policies increase security and passenger throughput by efficiently and effectively utilizing available screening resources. 7. The impact of aviation checkpoint queues on optimizing security screening effectiveness International Nuclear Information System (INIS) Lee, Adrian J.; Jacobson, Sheldon H. 2011-01-01 Passenger screening at aviation security checkpoints is a critical component in protecting airports and aircraft from terrorist threats. Recent developments in screening device technology have increased the ability to detect these threats; however, the average amount of time it takes to screen a passenger still remains a concern. This paper models the queueing process for a multi-level airport checkpoint security system, where multiple security classes are formed through subsets of specialized screening devices. An optimal static assignment policy is obtained which minimizes the steady-state expected amount of time a passenger spends in the security system. Then, an optimal dynamic assignment policy is obtained through a transient analysis that balances the expected number of true alarms with the expected amount of time a passenger spends in the security system. Performance of a two-class system is compared to that of a selective security system containing primary and secondary levels of screening. The key contribution is that the resulting optimal assignment policies increase security and passenger throughput by efficiently and effectively utilizing available screening resources. 8. The Effectiveness Analysis of Waiting Processes in the Different Branches of a Bank by Queue Model Directory of Open Access Journals (Sweden) Abdullah ÖZÇİL 2015-06-01 Full Text Available Despite the appreciable increase in the number of bank branches every year, nowadays queues for services don’t decrease and even become parts of our daily lives. By minimizing waiting processes the least, increasing customer satisfaction should be one of branch managers’ main goals. A quick and also customer oriented service with high quality is the most important factor for customer loyalty. In this study, Queueing theory, one of Operation Research techniques, is handled and in application, the data are obtained related to waiting in queue of customer in six different branches of two banks operating in Denizli and then they are analyzed by Queueing theory and also calculated the average effectiveness of the system. The study’s data are obtained by six branches of two banks called as A1, A2, A3, B1, B2 and B3. At the end of study it is presented to the company some advices that can bring benefits to the staff and customers. In this study, Queueing theory, one of Operation Research techniques, is handled and in application, the data are obtained related to waiting in queue of customer in three different branches of a bank operating in Denizli and then they are analyzed by Queueing theory and also calculated the average effectiveness of the system. The study’s data are obtained by three branches of the bank called A1, A2 and A3. At last it is presented to the company some advices that can bring more benefits to the staff and clients. 9. Folding Proteins at 500 ns/hour with Work Queue. Science.gov (United States) Abdul-Wahid, Badi'; Yu, Li; Rajan, Dinesh; Feng, Haoyun; Darve, Eric; Thain, Douglas; Izaguirre, Jesús A 2012-10-01 Molecular modeling is a field that traditionally has large computational costs. Until recently, most simulation techniques relied on long trajectories, which inherently have poor scalability. A new class of methods is proposed that requires only a large number of short calculations, and for which minimal communication between computer nodes is required. We considered one of the more accurate variants called Accelerated Weighted Ensemble Dynamics (AWE) and for which distributed computing can be made efficient. We implemented AWE using the Work Queue framework for task management and applied it to an all atom protein model (Fip35 WW domain). We can run with excellent scalability by simultaneously utilizing heterogeneous resources from multiple computing platforms such as clouds (Amazon EC2, Microsoft Azure), dedicated clusters, grids, on multiple architectures (CPU/GPU, 32/64bit), and in a dynamic environment in which processes are regularly added or removed from the pool. This has allowed us to achieve an aggregate sampling rate of over 500 ns/hour. As a comparison, a single process typically achieves 0.1 ns/hour. 10. THEORETICAL FEATURES REGARDING THE EVOLUTION OVER TIME OF THE MAIN COMMUNICATION MODELS USED FOR THE STUDY OF MASS COMMUNICATION Directory of Open Access Journals (Sweden) Irina IOSUB 2016-06-01 Full Text Available In the context of increasingly accelerated development of technology and particularly of the Internet, mass communication acquires new meanings. This article proposes a brief theoretical approach to the study of mass communication as it was treated in the specific literature of the 50s and 60s, when there was little talk about new technologies. However, many features identified since then still retain their topicality and for this reason it is interesting to note the evolution over time of the main communication models that were and some of them still are used for the study of mass communication. They are relevant to the context in which a complete study of mass communication is required, not only from the perspective of the present, but also from the period in which it was outlined. Thus, this article is divided into three main sections: the first part represents the meaning of communication in a general sense, so that the second part to represent the mass communication process and its characteristics, and the last part to represent the main models of communication in the order in which they have occurred, and especially aiming at new features that each of them brought. 11. Approximate anlysis of an unreliableM/M/c$retrial queue with phase merging algorithm. Directory of Open Access Journals (Sweden) faiza BELARBI 2016-06-01 Full Text Available In this paper, we investigate an approximate analysis of unreliable$M/M/c$retrial queue with$c\\geq 3$in which all servers are subject to breakdowns and repairs. Arriving customers that are unable to access a server due to congestion or failure can choose to enter a retrial orbit for an exponentially distributed amount of time and persistently attempt to gain access to a server, or abandon their request and depart the system. Once a customer is admitted to a service station, they remain there for a random duration until service is complete and then depart the system. However, if the server fails during service, i.e., an active breakdown, the customer may choose to abandon the system or proceed directly to the retrial orbit while the server begins repair immediately. In the unreliable model, there are no exact solutions when the number of servers exceeds one. Therefore, we seek to approximate the steady-state joint distribution of the number of customers in orbit and the status of the$c\$ servers for the case of Markovian arrival and service times. Our approach to deriving the approximate steady-state probabilities employs a phase-merging algorithm.

12. THREE-MOMENT BASED APPROXIMATION OF PROBABILITY DISTRIBUTIONS IN QUEUEING SYSTEMS

Directory of Open Access Journals (Sweden)

T. I. Aliev

2014-03-01

Full Text Available The paper deals with the problem of approximation of probability distributions of random variables defined in positive area of real numbers with coefficient of variation different from unity. While using queueing systems as models for computer networks, calculation of characteristics is usually performed at the level of expectation and variance. At the same time, one of the main characteristics of multimedia data transmission quality in computer networks is delay jitter. For jitter calculation the function of packets time delay distribution should be known. It is shown that changing the third moment of distribution of packets delay leads to jitter calculation difference in tens or hundreds of percent, with the same values of the first two moments – expectation value and delay variation coefficient. This means that delay distribution approximation for the calculation of jitter should be performed in accordance with the third moment of delay distribution. For random variables with coefficients of variation greater than unity, iterative approximation algorithm with hyper-exponential two-phase distribution based on three moments of approximated distribution is offered. It is shown that for random variables with coefficients of variation less than unity, the impact of the third moment of distribution becomes negligible, and for approximation of such distributions Erlang distribution with two first moments should be used. This approach gives the possibility to obtain upper bounds for relevant characteristics, particularly, the upper bound of delay jitter.

13. Traffic Regulation on Wireless 802.11 Networks Using Multiple Queue Technique

Science.gov (United States)

Dhanal, Radhika J.; Patil, G. A.

2010-11-01

WLAN technologies are becoming increasingly popular and are platform for many future applications. IEEE 802.11 Wireless LAN (WLAN) is an excellent solution for the broadband wireless networking. This paper presents a simple approach to enhance the performance of real time (RT) and non-real time (NRT) services over the 802.11 WLAN by using some special queues. This requires the system to first identify the type of service and then use the appropriate scheduling algorithm. The admission control algorithm is used first to determine the admission of particular station. Deficit round robin algorithm is used to set the priorities to RT and NRT packets in order to increase the QoS of WLAN. So we can combine both these algorithms by implementing them one after another. The proposed scheme can improve Voice/Data/Video services through simple software upgrades by reducing the delay, jitter and increasing the throughput. Through simulation, we show that the proposed scheme can give better QoS than existing schemes.

14. The congestion control algorithm based on queue management of each node in mobile ad hoc networks

Science.gov (United States)

Wei, Yifei; Chang, Lin; Wang, Yali; Wang, Gaoping

2016-12-01

This paper proposes an active queue management mechanism, considering the node's own ability and its importance in the network to set the queue threshold. As the network load increases, local congestion of mobile ad hoc network may lead to network performance degradation, hot node's energy consumption increase even failure. If small energy nodes congested because of forwarding data packets, then when it is used as the source node will cause a lot of packet loss. This paper proposes an active queue management mechanism, considering the node's own ability and its importance in the network to set the queue threshold. Controlling nodes buffer queue in different levels of congestion area probability by adjusting the upper limits and lower limits, thus nodes can adjust responsibility of forwarding data packets according to their own situation. The proposed algorithm will slow down the send rate hop by hop along the data package transmission direction from congestion node to source node so that to prevent further congestion from the source node. The simulation results show that, the algorithm can better play the data forwarding ability of strong nodes, protect the weak nodes, can effectively alleviate the network congestion situation.

15. Priority Queues with Fractional Service for Tiered Delay QoS

Directory of Open Access Journals (Sweden)

Gary Chang

2015-12-01

Full Text Available Packet scheduling is key to quality of service (QoS capabilities of broadband wired and wireless networks. In a heterogeneous traffic environment, a comprehensive QoS packet scheduler must strike a balance between flow fairness and access delay. Many advanced packet scheduling solutions have targeted fair bandwidth allocation while protecting delay-constrained traffic by adding priority queue(s on top of a fair bandwidth scheduler. Priority queues are known to cause performance uncertainties and, thus, various modifications have been proposed. In this paper, we present a packet queueing engine dubbed Fractional Service Buffer (FSB, which, when coupled with a configurable flow scheduler, can achieve desired QoS objectives, such as fair throughputs and differentiated delay guarantees. Key performance metrics, such as delay limit and probability of delay limit violation, are derived as a function of key FSB parameters for each delay class in the packet queueing engine using diffusion approximations. OPNET simulations verify these analytical results.

16. BioQueue: a novel pipeline framework to accelerate bioinformatics analysis.

Science.gov (United States)

Yao, Li; Wang, Heming; Song, Yuanyuan; Sui, Guangchao

2017-10-15

17. Queue Management Practices of Quick ServiceRestaurants (QSR in Lipa City, Philippines

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Leoven A. Austria

2015-12-01

Full Text Available –Problems regarding waiting line in quick service restaurants (QSR has been one of the main concerns of industries and scholars nowadays. It is because people today demand not only for qualityfood but also for speed. Quick service restaurant players explore on the approaches to optimize the efficiency of restaurant management. One important area that defines how well and efficient a fast food restaurant delivers its product and services to customers is its waiting line (queue management practices. The study was conducted at Lipa City, involving five popular quick service restaurants named by the researcher as QSR A, B, C, D, and E. It made used of 363customer respondents proportionally obtained from five restaurants.It intended to assess the extent of implementation of the queue management practices of the restaurants and the level of satisfaction of the customers in such practices in terms of customer arrival, waiting line and service facility. The findings revealed the queuing system used and the waiting line structured utilized by the restaurants. The extent of implementation of the queue management practices in the three areas mentioned of the five QSR’s was presented comparatively. Likewise, the level of customer’s satisfaction on the queue management practices was also determined. Significant difference in the extent of implementation and in the level of customer satisfaction were determined if the respondents were grouped according to restaurant’s profile. Recommendations in the improvement of queue were given based on the findings.

18. Is there a time trend in medical practice variations?: a review of the literature and an critical analysis of theoretical approaches.

NARCIS (Netherlands)

Groenewegen, P.P.; Westert, G.P.

2004-01-01

The aim of this study was to review the research evidence for a decreasing time trend in medical practice variation and to contribute to our theoretical understanding of trends in medical practice variations. We searched Pubmed for articles reporting on time trends in medical practice variations.

19. A Two-Stage Queue Model to Optimize Layout of Urban Drainage System considering Extreme Rainstorms

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Xinhua He

2017-01-01

Full Text Available Extreme rainstorm is a main factor to cause urban floods when urban drainage system cannot discharge stormwater successfully. This paper investigates distribution feature of rainstorms and draining process of urban drainage systems and uses a two-stage single-counter queue method M/M/1→M/D/1 to model urban drainage system. The model emphasizes randomness of extreme rainstorms, fuzziness of draining process, and construction and operation cost of drainage system. Its two objectives are total cost of construction and operation and overall sojourn time of stormwater. An improved genetic algorithm is redesigned to solve this complex nondeterministic problem, which incorporates with stochastic and fuzzy characteristics in whole drainage process. A numerical example in Shanghai illustrates how to implement the model, and comparisons with alternative algorithms show its performance in computational flexibility and efficiency. Discussions on sensitivity of four main parameters, that is, quantity of pump stations, drainage pipe diameter, rainstorm precipitation intensity, and confidence levels, are also presented to provide guidance for designing urban drainage system.

20. Efficient Redundancy Techniques in Cloud and Desktop Grid Systems using MAP/G/c-type Queues

Science.gov (United States)

Chakravarthy, Srinivas R.; Rumyantsev, Alexander

2018-03-01

Cloud computing is continuing to prove its flexibility and versatility in helping industries and businesses as well as academia as a way of providing needed computing capacity. As an important alternative to cloud computing, desktop grids allow to utilize the idle computer resources of an enterprise/community by means of distributed computing system, providing a more secure and controllable environment with lower operational expenses. Further, both cloud computing and desktop grids are meant to optimize limited resources and at the same time to decrease the expected latency for users. The crucial parameter for optimization both in cloud computing and in desktop grids is the level of redundancy (replication) for service requests/workunits. In this paper we study the optimal replication policies by considering three variations of Fork-Join systems in the context of a multi-server queueing system with a versatile point process for the arrivals. For services we consider phase type distributions as well as shifted exponential and Weibull. We use both analytical and simulation approach in our analysis and report some interesting qualitative results.

1. Efficient Redundancy Techniques in Cloud and Desktop Grid Systems using MAP/G/c-type Queues

Directory of Open Access Journals (Sweden)

Chakravarthy Srinivas R.

2018-03-01

Full Text Available Cloud computing is continuing to prove its flexibility and versatility in helping industries and businesses as well as academia as a way of providing needed computing capacity. As an important alternative to cloud computing, desktop grids allow to utilize the idle computer resources of an enterprise/community by means of distributed computing system, providing a more secure and controllable environment with lower operational expenses. Further, both cloud computing and desktop grids are meant to optimize limited resources and at the same time to decrease the expected latency for users. The crucial parameter for optimization both in cloud computing and in desktop grids is the level of redundancy (replication for service requests/workunits. In this paper we study the optimal replication policies by considering three variations of Fork-Join systems in the context of a multi-server queueing system with a versatile point process for the arrivals. For services we consider phase type distributions as well as shifted exponential and Weibull. We use both analytical and simulation approach in our analysis and report some interesting qualitative results.

2. An unreliable group arrival queue with k stages of service, retrial under variant vacation policy

Science.gov (United States)

Radha, J.; Indhira, K.; Chandrasekaran, V. M.

2017-11-01

In this research work we considered repairable retrial queue with group arrival and the server utilize the variant vacations. A server gives service in k stages. Any arriving group of units finds the server free, one from the group entering the first stage of service and the rest are joining into the orbit. After completion of the i th stage of service, the customer may have the option to choose (i+1)th stage of service with probability θi , with probability pi may join into orbit as feedback customer or may leave the system with probability {q}i=≤ft\\{\\begin{array}{l}1-{p}i-{θ }i,i=1,2,\\cdots k-1\\ 1-{p}i,i=k\\end{array}\\right\\}. If the orbit is empty at the service completion of each stage service, the server takes modified vacation until at least one customer appears in the orbit on the server returns from a vacation. Busy server may get to breakdown and the service channel will fail for a short interval of time. By using the supplementary variable method, steady state probability generating function for system size, some system performance measures are discussed.

3. Fight for your breeding right: hierarchy re-establishment predicts aggression in a social queue.

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Wong, Marian; Balshine, Sigal

2011-04-23

Social aggression is one of the most conspicuous features of animal societies, yet little is known about the causes of individual variation in aggression within social hierarchies. Recent theory suggests that when individuals form queues for breeding, variation in social aggression by non-breeding group members is related to their probability of inheriting breeding status. However, levels of aggression could also vary as a temporary response to changes in the hierarchy, with individuals becoming more aggressive as they ascend in rank, in order to re-establish dominance relationships. Using the group-living fish, Neolamprologus pulcher, we show that subordinates became more aggressive after they ascended in rank. Female ascenders exhibited more rapid increases in aggression than males, and the increased aggression was primarily directed towards group members of adjacent rather than non-adjacent rank, suggesting that social aggression was related to conflict over rank. Elevated aggression by ascenders was not sustained over time, there was no relationship between rank and aggression in stable groups, and aggression given by ascenders was not sex-biased. Together, these results suggest that the need to re-establish dominance relationships following rank ascension is an important determinant of variation in aggression in animal societies.

4. Analysis of Single-Server Queue with Phase-Type Service and Energy Harvesting

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Sergey A. Dudin

2016-01-01

Full Text Available We propose a queueing model suitable, for example, for modelling operation of nodes of sensor networks. The sensor node senses a random field and generates packets to be transmitted to the central node. The sensor node has a battery of a finite capacity and harvests energy during its operation from outside (using solar cells, wind turbines, piezoelectric cells, etc.. We assume that, generally speaking, service (transmission of a packet consists of a random number of phases and implementation of each phase requires a unit of energy. If the battery becomes empty, transmission is failed. To reduce the probability of forced transmission termination, we suggest that the packet can be accepted for transmission only when the number of energy units is greater than or equal to some threshold. Under quite general assumptions about the pattern of the arrival processes of packets and energy, we compute the stationary distributions of the system states and the waiting time of a packet in the system and numerically analyze performance measures of the system as functions of the threshold. Validity of Little’s formula and its counterpart is verified.

5. Terminal Appointment System Design by Non-stationary M(t)/Ek/c(t) Queueing Model and Genetic Algorithm

DEFF Research Database (Denmark)

Chen, Gang; Govindan, Kannan; Yang, Zhong-Zhen

2013-01-01

Long truck queue is a common problem at big marine container terminals, where the resources and equipment are usually scheduled to serve ships prior to trucks. To reduce truck queues, some container terminals adopt terminal appointment system (TAS) to manage truck arrivals. This paper addresses two...

6. Active Queue Management in TCP Networks Based on Fuzzy-Pid Controller

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Hossein ASHTIANI

2012-01-01

Full Text Available We introduce a novel and robust active queue management (AQM scheme based on a fuzzy controller, called hybrid fuzzy-PID controller. In the TCP network, AQM is important to regulate the queue length by passing or dropping the packets at the intermediate routers. RED, PI, and PID algorithms have been used for AQM. But these algorithms show weaknesses in the detection and control of congestion under dynamically changing network situations. In this paper a novel Fuzzy-based proportional-integral derivative (PID controller, which acts as an active queue manager (AQM for Internet routers, is proposed. These controllers are used to reduce packet loss and improve network utilization in TCP/IP networks. A new hybrid controller is proposed and compared with traditional RED based controller. Simulations are carried out to demonstrate the effectiveness of the proposed method and show that, the new hybrid fuzzy PID controller provides better performance than random early detection (RED and PID controllers

7. Design and analysis of a model predictive controller for active queue management.

Science.gov (United States)

Wang, Ping; Chen, Hong; Yang, Xiaoping; Ma, Yan

2012-01-01

Model predictive (MP) control as a novel active queue management (AQM) algorithm in dynamic computer networks is proposed. According to the predicted future queue length in the data buffer, early packets at the router are dropped reasonably by the MPAQM controller so that the queue length reaches the desired value with minimal tracking error. The drop probability is obtained by optimizing the network performance. Further, randomized algorithms are applied to analyze the robustness of MPAQM successfully, and also to provide the stability domain of systems with uncertain network parameters. The performances of MPAQM are evaluated through a series of simulations in NS2. The simulation results show that the MPAQM algorithm outperforms RED, PI, and REM algorithms in terms of stability, disturbance rejection, and robustness. Copyright © 2011 ISA. Published by Elsevier Ltd. All rights reserved.

8. Model Integrating Fuzzy Argument with Neural Network Enhancing the Performance of Active Queue Management

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Nguyen Kim Quoc

2015-08-01

Full Text Available The bottleneck control by active queue management mechanisms at network nodes is essential. In recent years, some researchers have used fuzzy argument to improve the active queue management mechanisms to enhance the network performance. However, the projects using the fuzzy controller depend heavily on professionals and their parameters cannot be updated according to changes in the network, so the effectiveness of this mechanism is not high. Therefore, we propose a model combining the fuzzy controller with neural network (FNN to overcome the limitations above. Results of the training of the neural networks will find the optimal parameters for the adaptive fuzzy controller well to changes of the network. This improves the operational efficiency of the active queue management mechanisms at network nodes.

9. Optimal Service Capacities in a Competitive Multiple-Server Queueing Environment

Science.gov (United States)

Ching, Wai-Ki; Choi, Sin-Man; Huang, Min

The study of economic behavior of service providers in a competition environment is an important and interesting research issue. A two-server queueing model has been proposed in Kalai et al. [11] for this purpose. Their model aims at studying the role and impact of service capacity in capturing larger market share so as to maximize the long-run expected profit. They formulate the problem as a two-person strategic game and analyze the equilibrium solutions. The main aim of this paper is to extend the results of the two-server queueing model in [11] to the case of multiple servers. We will only focus on the case when the queueing system is stable.

10. An M[X]/G(a,b/1 Queueing System with Breakdown and Repair, Stand-By Server, Multiple Vacation and Control Policy on Request for Re-Service

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G. Ayyappan

2018-06-01

Full Text Available In this paper, we discuss a non-Markovian batch arrival general bulk service single-server queueing system with server breakdown and repair, a stand-by server, multiple vacation and re-service. The main server’s regular service time, re-service time, vacation time and stand-by server’s service time are followed by general distributions and breakdown and repair times of the main server with exponential distributions. There is a stand-by server which is employed during the period in which the regular server remains under repair. The probability generating function of the queue size at an arbitrary time and some performance measures of the system are derived. Extensive numerical results are also illustrated.

11. Comparison of TEAR and TFRC throughput for Drop tail and RED Queue Management Techniques

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Parminderjeet Singh

2014-12-01

Full Text Available The comparison of throughput for TEAR (TCP emulation at receivers and TFRC TCP friendly rate control in MANETs is done with varying Active queue Management Techniques. The analysis reveals that for bandwidth constraint links, TEAR and TFRC perform far better than normal traffic propagation through TCP. In case of TEAR, the processing and route congestion algorithm load is shared by the receiver resulting in lesser load at the transmitters. In TFRC the TCP traffic is propagated via an algorithm to curb acknowledgement congestions. The effect of these two techniques is monitored on Droptail and RED, two of the most common Active Queue Management Techniques.

12. The Jackson Queueing Network Model Built Using Poisson Measures. Application To A Bank Model

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Ciuiu Daniel

2014-07-01

Full Text Available In this paper we will build a bank model using Poisson measures and Jackson queueing networks. We take into account the relationship between the Poisson and the exponential distributions, and we consider for each credit/deposit type a node where shocks are modeled as the compound Poisson processes. The transmissions of the shocks are modeled as moving between nodes in Jackson queueing networks, the external shocks are modeled as external arrivals, and the absorption of shocks as departures from the network.

13. Stochastic Processes and Queueing Theory used in Cloud Computer Performance Simulations

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Florin-Catalin ENACHE

2015-10-01

Full Text Available The growing character of the cloud business has manifested exponentially in the last 5 years. The capacity managers need to concentrate on a practical way to simulate the random demands a cloud infrastructure could face, even if there are not too many mathematical tools to simulate such demands.This paper presents an introduction into the most important stochastic processes and queueing theory concepts used for modeling computer performance. Moreover, it shows the cases where such concepts are applicable and when not, using clear programming examples on how to simulate a queue, and how to use and validate a simulation, when there are no mathematical concepts to back it up.

14. Chaotic queue-based genetic algorithm for design of a self-tuning fuzzy logic controller

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Saini, Sanju; Saini, J. S.

2012-11-01

This paper employs a chaotic queue-based method using logistic equation in a non-canonical genetic algorithm for optimizing the performance of a self-tuning Fuzzy Logic Controller, used for controlling a nonlinear double-coupled system. A comparison has been made with a standard canonical genetic algorithm implemented on the same plant. It has been shown that chaotic queue-method brings an improvement in the performance of the FLC for wide range of set point changes by a more profound initial population spread in the search space.

15. Analysis of an M|G|1|R queue with batch arrivals and two hysteretic overload control policies

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Gaidamaka Yuliya

2014-09-01

Full Text Available Hysteretic control of arrivals is one of the most easy-to-implement and effective solutions of overload problems occurring in SIP-servers. A mathematical model of an SIP server based on the queueing system M[X]|G|1(L,H|(H,R with batch arrivals and two hysteretic loops is being analyzed. This paper proposes two analytical methods for studying performance characteristics related to the number of customers in the system. Two control policies defined by instants when it is decided to change the system’s mode are considered. The expression for an important performance characteristic of each policy (the mean time between changes in the system mode is presented. Numerical examples that allow comparison of the efficiency of both policies are given

16. Fast concurrent array-based stacks, queues and deques using fetch-and-increment-bounded, fetch-and-decrement-bounded and store-on-twin synchronization primitives

Science.gov (United States)

Chen, Dong; Gara, Alana; Heidelberger, Philip; Kumar, Sameer; Ohmacht, Martin; Steinmacher-Burow, Burkhard; Wisniewski, Robert

2014-09-16

Implementation primitives for concurrent array-based stacks, queues, double-ended queues (deques) and wrapped deques are provided. In one aspect, each element of the stack, queue, deque or wrapped deque data structure has its own ticket lock, allowing multiple threads to concurrently use multiple elements of the data structure and thus achieving high performance. In another aspect, new synchronization primitives FetchAndIncrementBounded (Counter, Bound) and FetchAndDecrementBounded (Counter, Bound) are implemented. These primitives can be implemented in hardware and thus promise a very fast throughput for queues, stacks and double-ended queues.

17. An Empirical Study Of Using New Technology like NFC, AI, RFID etc. to be implemented in shopping malls in ajmer : To Ease Out The Customer Shopping Experience Like Queue Less And Cashless Payment Mode

OpenAIRE

Dimple,; Jyoti Kushwah; Manisha Tak; Neeharika singh; Dr. Ajay Singh Jethoo; Vijay Laxmi Kalyani

2017-01-01

In today’s world due to rapid development of new shopping trend. The retailers launches new technologies for new shopping trend. In today scenario every people are busy. When we are talking about shopping from stores, shopping malls etc., the customers waiting in queue for long time for payment process. This is a problematic conditions for customers. The traditional shopping trend consuming more time of customers during shopping. To remove this problem many retailers are focussing that how to...

18. Queue-based modelling and detection of parameters involved in stroke outcome

DEFF Research Database (Denmark)

Vilic, Adnan; Petersen, John Asger; Wienecke, Troels

2017-01-01

We designed a queue-based model, and investigated which parameters are of importance when predicting stroke outcome. Medical record forms have been collected for 57 ischemic stroke patients, including medical history and vital sign measurement along with neurological scores for the first twenty...

19. The priority queue as an example of hardware/software codesign

DEFF Research Database (Denmark)

Høeg, Flemming; Mellergaard, Niels; Staunstrup, Jørgen

1994-01-01

The paper identifies a number of issues that are believed to be important for hardware/software codesign. The issues are illustrated by a small comprehensible example: a priority queue. Based on simulations of a real application, we suggest a combined hardware/software realization of the priority...

20. On the correlation structure of a Lévy-driven queue

NARCIS (Netherlands)

A. Es-Saghouani; M.R.H. Mandjes (Michel)

2007-01-01

textabstractIn this paper we consider a single-server queue with Lévy input, and in particular its workload process (Q(t)), for t > 0, with a focus on the correlation structure. With the correlation function defined as r(t) := Cov(Q(0),Q(t))/Var Q(0) (assuming that the workload process is in

1. A Busy period analysis of the level dependent PH/PH/1/K queue

NARCIS (Netherlands)

2011-01-01

In this paper, we study the transient behavior of a level dependent single server queuing system with a waiting room of finite size during the busy period. The focus is on the level dependent PH/PH/1/K queue. We derive in closed form the joint transform of the length of the busy period, the number

2. A Busy period analysis for the state dependent M/M/1/K queue

NARCIS (Netherlands)

2010-01-01

In this paper, we study the transient behavior of a state dependent M/M/1/K queue during the busy period. We derive in closed-form the joint transform of the length of the busy period, the number of customers served during the busy period, and the number of losses during the busy period. For two

3. DROP TAIL AND RED QUEUE MANAGEMENT WITH SMALL BUFFERS:STABILITY AND HOPF BIFURCATION

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Ganesh Patil

2011-06-01

Full Text Available There are many factors that are important in the design of queue management schemes for routers in the Internet: for example, queuing delay, link utilization, packet loss, energy consumption and the impact of router buffer size. By considering a fluid model for the congestion avoidance phase of Additive Increase Multiplicative Decrease (AIMD TCP, in a small buffer regime, we argue that stability should also be a desirable feature for network performance. The queue management schemes we study are Drop Tail and Random Early Detection (RED. For Drop Tail, the analytical arguments are based on local stability and bifurcation theory. As the buffer size acts as a bifurcation parameter, variations in it can readily lead to the emergence of limit cycles. We then present NS2 simulations to study the effect of changing buffer size on queue dynamics, utilization, window size and packet loss for three different flow scenarios. The simulations corroborate the analysis which highlights that performance is coupled with the notion of stability. Our work suggests that, in a small buffer regime, a simple Drop Tail queue management serves to enhance stability and appears preferable to the much studied RED scheme.

4. A queueing model of pilot decision making in a multi-task flight management situation

Science.gov (United States)

Walden, R. S.; Rouse, W. B.

1977-01-01

Allocation of decision making responsibility between pilot and computer is considered and a flight management task, designed for the study of pilot-computer interaction, is discussed. A queueing theory model of pilot decision making in this multi-task, control and monitoring situation is presented. An experimental investigation of pilot decision making and the resulting model parameters are discussed.

5. Simple product-form bounds for queueing networks with finite clusters

NARCIS (Netherlands)

van Dijk, N.M.; van der Sluis, E.

2001-01-01

Queueing networks are studied with finite capacity constraints for clusters of stations. First, by an instructive tandem cluster example it is shown how a product-form modification method for networks with finite stations can be extended to networks with finite clusters. Next, a general result is

6. Research on elastic resource management for multi-queue under cloud computing environment

Science.gov (United States)

CHENG, Zhenjing; LI, Haibo; HUANG, Qiulan; Cheng, Yaodong; CHEN, Gang

2017-10-01

As a new approach to manage computing resource, virtualization technology is more and more widely applied in the high-energy physics field. A virtual computing cluster based on Openstack was built at IHEP, using HTCondor as the job queue management system. In a traditional static cluster, a fixed number of virtual machines are pre-allocated to the job queue of different experiments. However this method cannot be well adapted to the volatility of computing resource requirements. To solve this problem, an elastic computing resource management system under cloud computing environment has been designed. This system performs unified management of virtual computing nodes on the basis of job queue in HTCondor based on dual resource thresholds as well as the quota service. A two-stage pool is designed to improve the efficiency of resource pool expansion. This paper will present several use cases of the elastic resource management system in IHEPCloud. The practical run shows virtual computing resource dynamically expanded or shrunk while computing requirements change. Additionally, the CPU utilization ratio of computing resource was significantly increased when compared with traditional resource management. The system also has good performance when there are multiple condor schedulers and multiple job queues.

7. A computational approach for fluid queues driven by truncated birth-death processes.

NARCIS (Netherlands)

Lenin, R.B.; Parthasarathy, P.R.

2000-01-01

In this paper, we analyze fluid queues driven by truncated birth-death processes with general birth and death rates. We compute the equilibrium distribution of the content of the fluid buffer by providing efficient numerical procedures to compute the eigenvalues and the eigenvectors of the

8. On first-come first-served versus random service discipline in multiclass closed queueing networks

NARCIS (Netherlands)

Buitenhek, R.; van Houtum, Geert-Jan; van Ommeren, Jan C.W.

1997-01-01

We consider multiclass closed queueing networks. For these networks, a lot of work has been devoted to characterizing and weakening the conditions under which a product-form solution is obtained for the steady-state distribution. From this work, it is known that, under certain conditions, all

9. Optimal hysteretic control for a BMAP/SM/1/N queue with two operation modes

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Alexander N. Dudin

2000-01-01

Full Text Available We consider BMAP/SM/1 type queueing system with finite buffer of size N. The system has two operation modes, which are characterized by the matrix generating function of BMAP-input, the kernel of the semi-Markovian service process, and utilization cost. An algorithm for determining the optimal hysteresis strategy is presented.

10. Transient analysis of one-sided Lévy-driven queues

NARCIS (Netherlands)

Starreveld, N.J.; Bekker, R.; Mandjes, M.

2016-01-01

In this article, we analyze the transient behavior of the workload process in a Lévy-driven queue. We are interested in the value of the workload process at a random epoch; this epoch is distributed as the sum of independent exponential random variables. We consider both cases of spectrally

11. Transient analysis of one-sided Lévy-driven queues

NARCIS (Netherlands)

Starreveld, N.J.; R. Bekker (Rene); M.R.H. Mandjes (Michel)

2016-01-01

textabstractIn this article, we analyze the transient behavior of the workload process in a Lévy-driven queue. We are interested in the value of the workload process at a random epoch; this epoch is distributed as the sum of independent exponential random variables. We consider both cases of

12. Transient analysis of one-sided Lévy-driven queues

NARCIS (Netherlands)

Starreveld, N.; Bekker, R.; Mandjes, M.R.H.

2015-01-01

In this paper we analyze the transient behavior of the workload process in a Lévy input queue. We are interested in the value of the workload process at a random epoch; this epoch is distributed as the sum of independent exponential random variables. We consider both cases of spectrally one-sided

13. A computational approach for a fluid queue driven by a truncated birth-death process

NARCIS (Netherlands)

Lenin, R.B.; Parthasarathy, P.R.

1999-01-01

In this paper, we consider a fluid queue driven by a truncated birth-death process with general birth and death rates. We find the equilibrium distribution of the content of the fluid buffer by computing the eigenvalues and eigenvectors of an associated real tridiagonal matrix. We provide efficient

14. Optimal control for an M^X/G/1/N+1 queue with two service modes

NARCIS (Netherlands)

Ridder, A.A.N.; Nobel, R.D.; Krishnan, G.S.S.; Anita, R.; Lakshmi, R.S.; Kumar, M.S.; Bonato, A.; Grana, M.

2014-01-01

A finite-buffer queueing model is considered with batch Poisson input and controllable service rate. A batch that upon arrival does not fit in the unoccupied places of the buffer is partially rejected. A decision to change the service mode can be made at service completion epochs only, and vacation

15. Production Task Queue Optimization Based on Multi-Attribute Evaluation for Complex Product Assembly Workshop.

Science.gov (United States)

Li, Lian-Hui; Mo, Rong

2015-01-01

The production task queue has a great significance for manufacturing resource allocation and scheduling decision. Man-made qualitative queue optimization method has a poor effect and makes the application difficult. A production task queue optimization method is proposed based on multi-attribute evaluation. According to the task attributes, the hierarchical multi-attribute model is established and the indicator quantization methods are given. To calculate the objective indicator weight, criteria importance through intercriteria correlation (CRITIC) is selected from three usual methods. To calculate the subjective indicator weight, BP neural network is used to determine the judge importance degree, and then the trapezoid fuzzy scale-rough AHP considering the judge importance degree is put forward. The balanced weight, which integrates the objective weight and the subjective weight, is calculated base on multi-weight contribution balance model. The technique for order preference by similarity to an ideal solution (TOPSIS) improved by replacing Euclidean distance with relative entropy distance is used to sequence the tasks and optimize the queue by the weighted indicator value. A case study is given to illustrate its correctness and feasibility.

16. Production Task Queue Optimization Based on Multi-Attribute Evaluation for Complex Product Assembly Workshop.

Directory of Open Access Journals (Sweden)

Lian-Hui Li

Full Text Available The production task queue has a great significance for manufacturing resource allocation and scheduling decision. Man-made qualitative queue optimization method has a poor effect and makes the application difficult. A production task queue optimization method is proposed based on multi-attribute evaluation. According to the task attributes, the hierarchical multi-attribute model is established and the indicator quantization methods are given. To calculate the objective indicator weight, criteria importance through intercriteria correlation (CRITIC is selected from three usual methods. To calculate the subjective indicator weight, BP neural network is used to determine the judge importance degree, and then the trapezoid fuzzy scale-rough AHP considering the judge importance degree is put forward. The balanced weight, which integrates the objective weight and the subjective weight, is calculated base on multi-weight contribution balance model. The technique for order preference by similarity to an ideal solution (TOPSIS improved by replacing Euclidean distance with relative entropy distance is used to sequence the tasks and optimize the queue by the weighted indicator value. A case study is given to illustrate its correctness and feasibility.

17. Networks of ·/G/∞ queues with shot-noise-driven arrival intensities

NARCIS (Netherlands)

Koops, D.T.; Boxma, O.J.; Mandjes, M.R.H.

2017-01-01

We study infinite-server queues in which the arrival process is a Cox process (or doubly stochastic Poisson process), of which the arrival rate is given by a shot-noise process. A shot-noise rate emerges naturally in cases where the arrival rate tends to exhibit sudden increases (or shots) at random

18. A spectral approach to compute the mean performance measures of the queue with low-order BMAP input

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Ho Woo Lee

2003-01-01

Full Text Available This paper targets engineers and practitioners who want a simple procedure to compute the mean performance measures of the Batch Markovian Arrival process (BMAP/G/1 queueing system when the parameter matrices order is very low. We develop a set of system equations and derive the vector generating function of the queue length. Starting from the generating function, we propose a spectral approach that can be understandable to those who have basic knowledge of M/G/1 queues and eigenvalue algebra.

19. The truncated Hyper-Poisson queues: Hk/Ma,b/C/N with balking, reneging and general bulk service rule

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Shawky A.I.

2008-01-01

Full Text Available The aim of this paper is to derive the analytical solution of the queue: Hk/Ma,b/C/N with balking and reneging in which (I units arrive according to a hyper-Poisson distribution with k independent branches, (II the queue discipline is FIFO; and (III the units are served in batches according to a general bulk service rule. The steady-state probabilities, recurrence relations connecting various probabilities introduced are found and the expected number of units in the queue is derived in an explicit form. Also, some special cases are obtained. .

20. Central line-associated bloodstream infections and catheter dwell-time: A theoretical foundation for a rule of thumb.

Science.gov (United States)

Voets, Philip J G M

2018-05-14

Many clinicians know from experience and medical epidemiological literature that the risk of central line-associated bloodstream infections (CLABSI) increases rapidly with a prolonged catheter dwell-time, but how this infection risk increases over time remains obscure. In this manuscript, a clinically useful rule of thumb is derived, stating that the risk of CLABSI increases in a quadratic fashion with the increase in catheter dwell-time. The proposed rule of thumb could be considered a quick and effortless clinical tool to rationally predict the pattern of CLABSI risk with an increasing catheter dwell-time. Copyright © 2018. Published by Elsevier Ltd.