45941410
The optimal service time allocation of a versatile server to queue jobs and stochastically available non-queue jobs of different types
Abstract In this paper, we consider a service system in which the server can process N + 1 different types of jobs. Jobs of type 0 are generated randomly according to a Poisson stream. Jobs of types 1 to N are non-queue types which may or may not be available for completion by the server. To optimally allocate the server's time to these jobs, we formulate a finite state semi-Markov decision process model to this environment. With this model, the optimal stationary policies can be numerically determined via a policy-iteration algorithm. We also discuss the practical applications of this model to tele-service and tele-marketing operations.
41203874
Optimal Two-Threshold Policies in an M/G/1 Queue With Two Vacation Types
This paper treats two-threshold policies for an M/G/1 queue with two types of generally distributed random vacations: type 1 (long) and type 2 (short) vacations. Upon returning from a vacation, the server observes the queue length. If this is less than the lower threshold, the server takes a type 1 vacation; if it is between the two thresholds, the server takes a type 2 vacation; and if it is at or above the upper threshold, the server resumes serving the queue exhaustively. There is a shutdown cost for starting a series of vacations, a linear customer waiting cost, and type-dependent vacation reward rates. Renewal theory or the PASTA property is used to develop expressions for the average queue length and the average system cost for generally distributed vacations. A search procedure, which is provably finite for exponentially distributed vacations, is developed for determining the optimal threshold values.
20091556
Allocating kanbans for a production system in a general configuration with a new control strategy
We consider a production system in a general configuration with a new control strategy: the push policy for the part sending and the kanban mechanism for the work-in-process (WIP). The production system is composed of many stations (or workshops) such as an entry station, a set of workstations, a central station, and an exit station. This type of system is modeled as an open queueing network (OQN) in a general configuration with a Markov-type part sending policy and a machine no blocking (MNB) mechanism. The most important performance measures of the production system are the total throughput of the workstations and the total blocking flow of blocked parts sent from the workstations to the central station. This paper discusses an optimization problem with multiple objectives: allocate kanbans to the workstations so as to simultaneously maximize the total throughput and minimize the total blocking flow. Based on a semi-open decomposition approach, several useful properties of the system are characterized. These properties are used to develop a marginal algorithm for the optimization problem. Moreover, a dynamic simulation approach is devised as a tool for evaluating the quality of the solutions obtained by the algorithm. Numerical experiments are provided to demonstrate the efficiency of the algorithm through the simulation approach.
5191709
Discrete Time Geo/G/1 Queue with Multiple Adaptive Vacations
This paper treats the discrete time Geometric/G/1 system with vacations. In this system, after serving all customers in the system, the server will take a random maximum number of vacations before returning to the service mode. The stochastic decomposition property of steady-state queue length and waiting time has been proven. The busy period, vacation mode period, and service mode period distributions are also derived. Several common vacation policies are special cases of the vacation policy presented in this study.
1280703
Stationary Distributions of GI/M/c Queue with PH Type Vacations
We study a GI/M/c type queueing system with vacations in which all servers take vacations together when the system becomes empty. These servers keep taking synchronous vacations until they find waiting customers in the system at a vacation completion instant.The vacation time is a phase-type (PH) distributed random variable. Using embedded Markov chain modeling and the matrix geometric solution methods, we obtain explicit expressions for the stationary probability distributions of the queue length at arrivals and the waiting time. To compare the vacation model with the classical GI/M/c queue without vacations, we prove conditional stochastic decomposition properties for the queue length and the waiting time when all servers are busy. Our model is a generalization of several previous studies.
6801587
Performance analysis of k-fold multicast networks
Multicast involves transmitting information from a single source to multiple destinations, and is an important operation in high-performance networks. A k-fold multicast network was recently proposed as a cost-effective solution to providing better quality-of-service functions in supporting real-world multicast applications. To give a quantitative basis for network designers to determine the suitable value of system parameter k under different traffic loads, in this paper, we propose an analytical model for the performance of k-fold multicast networks under Poisson traffic. We first give the stationary distribution of network states, and then derive the throughput and blocking probability of the network. We also conduct extensive simulations to validate the analytical model, and the results show that the analytical model is very accurate under the assumptions made. The analytical and simulation results reveal that by increasing the fold of the network, network throughput increases very fast when the fanouts of multicast connections are relatively small, compared with the network size.
28725102
A Framework for Component Reuse in a Metamodelling-Based Software Development
Reuse forms one key mechanism in improving system development productivity and quality. In this paper we suggest a systematic framework for reuse processes, which is driven by ideas and concepts based on metamodelling. The framework enables us to consider reuse in a comprehensive manner and to develop support for reuse processes within a metaCASE environment. By utilising metamodelling concepts we expand reuse situations to cover both design artefacts and method components. Accordingly, the reuse framework consists of a system development process model, a type level hierarchy, a classification of reuse situation types, a component granularity model, and a model of reuse operations. We demonstrate the usefulness of the framework by analysing reuse support in a metaCASE environment: MetaEdit+. We also examine how the framework can help to strategise over possible software development scenarios (patterns) that involve various levels of reuse in situations where software requirements change considerably and there is a considerable number of design assets to exploit.
15452852
Battery-aware router scheduling in wireless mesh networks
Wireless mesh networks emerge as a flexible, low-cost and multipurpose networking platform with wired infrastructure connected to the Internet. A critical issue in mesh networks is to maintain network activities for a long lifetime with high energy efficiency. As more and more outdoor applications require long-lasting, high energy efficient and continuously-working mesh networks with battery-powered mesh routers, it is important to optimize the performance of mesh networks from a battery-aware point of view. Study in battery technology reveals that discharging of a battery is nonlinear. Batteries tend to discharge more power than needed, and reimburse the over-discharged power later if they have sufficiently long recovery time. Intuitively, to optimize network performance, a mesh router should recover its battery periodically to prolong the lifetime. In this paper, we introduce a mathematical model on battery discharging duration and lifetime for wireless mesh networks. We also present a battery lifetime optimization scheduling algorithm (BLOS) to maximize the lifetime of battery-powered mesh routers. Based on the BLOS algorithm, we further consider the problem of using battery powered routers to monitor or cover a few hot spots in the network. We refer to this problem as the spot covering under BLOS policy problem (SCBP). We prove that the SCBP problem is NP-hard and give an approximation algorithm called the spanning tree scheduling (STS) to dynamically schedule mesh routers. The key idea of the STS algorithm is to construct a spanning tree according to the BLOS policy in the mesh network. The time complexity of the STS algorithm is O(r) for a network with r mesh routers. Our simulation results show that the STS algorithm can greatly improve the lifetime, data throughput and power consumption efficiency of a wireless mesh network
1690812
Combining Labeled and Unlabeled Data for Learning Cross-Document Structural Relationships
Multi-document discourse analysis has emerged with the potential of improving various NLP applications. Based on the newly proposed Cross-document Structure Theory (CST), this paper describes an empirical study that classifies CST relationships between sentence pairs extracted from topically related documents, exploiting both labeled and unlabeled data. We investigate a binary classifier for determining existence of structural relationships and a full classifier using the full taxonomy of relationships. We show that in both cases the exploitation of unlabeled data helps improve the performance of learned classifiers.
18081212
A novel analytical model for electronic and optical switches with shared buffer
Switches with shared buffer have lower packet loss probabilities than other types of switches when the sizes of the buffers are the same. In the past, the performance analysis for electronic shared buffer switches has been carried out extensively. However, due to the strong dependencies of the output queues in the buffer, it is very difficult to find a good analytical model. Existing models are either accurate but have exponential complexities or not very accurate. In this paper, we propose a novel analytical model called the aggregation model for switches with shared buffer. This model can be used for analyzing both electronic and optical switches, and has perfect accuracies under all tested conditions and has polynomial time complexity. It is based on the idea of induction: first find the behavior of 2 queues, then aggregate them into one block; then find the behavior of 3 queues while regarding 2 of the queues as one block, then aggregate the 3 queues into one block; then aggregate 4 queues and so on. When a sufficient number of queues have been aggregated, the behavior of the entire switch is found. We believe that the new model represents the best analytical model for shared buffer switches so far.