The Experts below are selected from a list of 31281 Experts worldwide ranked by ideXlab platform
Roy D Yates - One of the best experts on this subject based on the ideXlab platform.
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lazy is timely status updates by an energy harvesting source
International Symposium on Information Theory, 2015Co-Authors: Roy D YatesAbstract:A source submits status updates to a Service facility for delivery to a monitor. Each update requires energy and the source is powered by a stochastic energy harvesting system. With knowledge of the Service facility state, the source avoids queue-induced delays by submitting a fresh update only after the Service Completion of a prior update. For a source with a large battery, we evaluate updating policies using a status age timeliness metric. We show that an optimal policy is lazy; following a Service Completion, the Service facility is frequently left idle even though the server may have sufficient energy to submit an update.
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ISIT - Lazy is timely: Status updates by an energy harvesting source
2015 IEEE International Symposium on Information Theory (ISIT), 2015Co-Authors: Roy D YatesAbstract:A source submits status updates to a Service facility for delivery to a monitor. Each update requires energy and the source is powered by a stochastic energy harvesting system. With knowledge of the Service facility state, the source avoids queue-induced delays by submitting a fresh update only after the Service Completion of a prior update. For a source with a large battery, we evaluate updating policies using a status age timeliness metric. We show that an optimal policy is lazy; following a Service Completion, the Service facility is frequently left idle even though the server may have sufficient energy to submit an update.
Tiannaishuo - One of the best experts on this subject based on the ideXlab platform.
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Analysis of Queueing Systems with Synchronous Single Vacation for Some Servers
Queueing Systems, 2003Co-Authors: G Zhangzhe, TiannaishuoAbstract:We study a multi-server M/M/c type queue with a single vacation policy for some idle servers. In this queueing system, if at a Service Completion instant, any d (d c) servers become idle, these d s...
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Analysis on queueing systems with synchronous vacations of partial servers
Performance Evaluation, 2003Co-Authors: Zhangzhe George, TiannaishuoAbstract:We study an M/M/c queue with server vacations. In this queueing system, d (≤ c) of c servers take synchronous vacations when these d servers become idle at a Service Completion instant. This type o...
Charles J Malmborg - One of the best experts on this subject based on the ideXlab platform.
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design models for unit load storage and retrieval systems using autonomous vehicle technology and resource conserving storage and dwell point policies
Applied Mathematical Modelling, 2007Co-Authors: Pohsun Kuo, Ananth Krishnamurthy, Charles J MalmborgAbstract:Computationally efficient design conceptualization models are proposed for automated unit load storage and retrieval systems based on autonomous vehicle technology. Vehicle and lift travel times and the probability distribution for 12 Service scenarios occurring under realistic operating assumptions are formulated and used to generate expected transaction Service times. Additional measures of system performance including transaction waiting time and vehicle utilization are formulated for systems using random storage and point-of-Service-Completion dwell point rules. The models provide a practical means of predicting key aspects of system performance based on five design variables that drive the majority of system costs. They are illustrated in the context of a conceptualization study adapted from an actual system installation.
Hideaki Takagi - One of the best experts on this subject based on the ideXlab platform.
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Times until Service Completion and abandonment in an M/M/ \begin{document}$ m$\end{document} preemptive-resume LCFS queue with impatient customers
Journal of Industrial & Management Optimization, 2018Co-Authors: Hideaki TakagiAbstract:We consider an M/M/ \begin{document}$ m$\end{document} preemptive-resume last-come first-served (PR-LCFS) queue without exogenous priority classes of impatient customers. We focus on analyzing the time interval from the arrival to either Service Completion or abandonment for an arbitrary customer. We formulate the problem as a one-dimensional birth-and-death process with two absorbing states, and consider the first passage times in this process. We give explicit expressions for the probabilities of Service Completion and abandonment. Furthermore, we present sets of recursive computational formulas for calculating the mean and second moment of the times until Service Completion and abandonment. The two special cases of a preemptive-loss system and an ordinary M/M/ \begin{document}$ m$\end{document} queue with patient customers only, both incorporating the preemptive LCFS discipline, are treated separately. We show some numerical examples in order to demonstrate the computation of theoretical formulas.
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QTNA - Waiting and Service Time of a Unique Customer in an M/M/m Preemptive LCFS Queue with Impatient Customers
Queueing Theory and Network Applications, 2017Co-Authors: Hideaki TakagiAbstract:We study an M/M/m preemptive last-come, first-served queue with impatient customers without priority classes. We focus on the probability of Service Completion and abandonment as well as the waiting and Service times of a unique customer who has the mean Service and patience times that are different from those of all other customers in the steady state. The problem is formulated as the first passage times in a combination of two one-dimensional birth-and-death processes each with two absorbing states. We provide explicit expressions in terms of Laplace-Stieltjes transform of the distribution function for the time to Service Completion or abandonment, which is decomposed into the waiting and Service times of the unique customer. A numerical example is presented in order to demonstrate the computation of theoretical formulas.
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times until Service Completion and abandonment in an m m begin document m end document preemptive resume lcfs queue with impatient customers
Journal of Industrial and Management Optimization, 2017Co-Authors: Hideaki TakagiAbstract:We consider an M/M/ \begin{document}$ m$\end{document} preemptive-resume last-come first-served (PR-LCFS) queue without exogenous priority classes of impatient customers. We focus on analyzing the time interval from the arrival to either Service Completion or abandonment for an arbitrary customer. We formulate the problem as a one-dimensional birth-and-death process with two absorbing states, and consider the first passage times in this process. We give explicit expressions for the probabilities of Service Completion and abandonment. Furthermore, we present sets of recursive computational formulas for calculating the mean and second moment of the times until Service Completion and abandonment. The two special cases of a preemptive-loss system and an ordinary M/M/ \begin{document}$ m$\end{document} queue with patient customers only, both incorporating the preemptive LCFS discipline, are treated separately. We show some numerical examples in order to demonstrate the computation of theoretical formulas.
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times to Service Completion and abandonment in the m m m preemptive lcfs queue with impatient customers
International Conference on Queueing Theory and Network Applications, 2016Co-Authors: Hideaki TakagiAbstract:We consider the M/M/m preemptive last-come, first-served queue without customer's priority classes. We focus on the analysis of the time interval from the arrival to either Service Completion or to abandonment of an arbitrary customer. We formulate the problem as a one-dimensional birth-and-death process with two absorbing states and consider the first passage times in this process. We give explicit expressions for the probabilities of Service Completion and abandonment. We also show sets of recursive computational formulas for calculating the mean and second moment of the times to Service Completion and abandonment. We present some numerical examples in order to demonstrate the computation of theoretical formulas.
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QTNA - Times to Service Completion and Abandonment in the M/M/m Preemptive LCFS Queue with Impatient Customers
Proceedings of the 11th International Conference on Queueing Theory and Network Applications - QTNA '16, 2016Co-Authors: Hideaki TakagiAbstract:We consider the M/M/m preemptive last-come, first-served queue without customer's priority classes. We focus on the analysis of the time interval from the arrival to either Service Completion or to abandonment of an arbitrary customer. We formulate the problem as a one-dimensional birth-and-death process with two absorbing states and consider the first passage times in this process. We give explicit expressions for the probabilities of Service Completion and abandonment. We also show sets of recursive computational formulas for calculating the mean and second moment of the times to Service Completion and abandonment. We present some numerical examples in order to demonstrate the computation of theoretical formulas.
Fred F. Easton - One of the best experts on this subject based on the ideXlab platform.
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Service Completion estimates for cross trained workforce schedules under uncertain attendance and demand
Production and Operations Management, 2014Co-Authors: Fred F. EastonAbstract:Although cross-trained workers offer numerous operational advantages for extended-hour Service businesses, they must first be scheduled for duty. The outcome from those decisions, usually made a week or more in advance, varies with realized Service demand, worker attendance, and the way available cross-trained workers are deployed once the demands for Service are known. By ignoring the joint variability of attendance and demand, we show that existing workforce scheduling models tend to overstate expected schedule performance and systematically undervalue the benefits of cross-training. We propose a two-stage stochastic program for profit-oriented cross-trained workforce scheduling and allocation decisions that is driven by Service Completion estimates obtained from the convolution of the employee attendance and Service demand distributions. Those estimates, reflecting optimal worker allocation decisions over all plausible realizations of attendance and demand, provide the gradient information used to guide workforce scheduling decisions. Comparing the performance of workforce scheduling decisions for hundreds of different hypothetical Service environments, we find that solutions based on convolution estimates are more profitable, favor proportionately more cross-trained workers and fewer specialists, and tend to recommend significantly larger (smaller) staffing levels for Services under high (low) contribution margins than workforce schedules developed with independent expectations of attendance and demand.
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Service Completion Estimates for Cross‐trained Workforce Schedules under Uncertain Attendance and Demand
Production and Operations Management, 2014Co-Authors: Fred F. EastonAbstract:Although cross-trained workers offer numerous operational advantages for extended-hour Service businesses, they must first be scheduled for duty. The outcome from those decisions, usually made a week or more in advance, varies with realized Service demand, worker attendance, and the way available cross-trained workers are deployed once the demands for Service are known. By ignoring the joint variability of attendance and demand, we show that existing workforce scheduling models tend to overstate expected schedule performance and systematically undervalue the benefits of cross-training. We propose a two-stage stochastic program for profit-oriented cross-trained workforce scheduling and allocation decisions that is driven by Service Completion estimates obtained from the convolution of the employee attendance and Service demand distributions. Those estimates, reflecting optimal worker allocation decisions over all plausible realizations of attendance and demand, provide the gradient information used to guide workforce scheduling decisions. Comparing the performance of workforce scheduling decisions for hundreds of different hypothetical Service environments, we find that solutions based on convolution estimates are more profitable, favor proportionately more cross-trained workers and fewer specialists, and tend to recommend significantly larger (smaller) staffing levels for Services under high (low) contribution margins than workforce schedules developed with independent expectations of attendance and demand.
