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Sample records for active queue management

  1. New active queue management mechanism for Web traffic

    Science.gov (United States)

    Kasthurirangan, Badri; Wang, Bin; Xu, J.

    2002-07-01

    In this work, we devise and study the performance of a new active queue management mechanism for Web traffic to more intelligently select packets to drop incipient of network congestion. The proposed mechanism specifically targets short-lived or fragile flows (e.g., most HTTP flows) to keep link utilization high while reducing the HTTP response time. The goal of the proposed active queue management scheme is to protect new TCP flows and TCP flows that have packet dropped recently from potential network congestion, thus achieving better response times. Our simulation studies have compared the performance of RED and the proposed AQM for a network with only HTTP traffic at loads less, close to, and more than the network capacity. Simulations show that a subsidy given to a flow that that is in its initial stage provides significantly better performance in terms of HTTP request-reply delays without sacrificing the link utilization. The new scheme is very simple to implement. It contains one additional control parameter to RED, and the tuning of this parameter is simple. Since most HTTP flows are short-lived, only the state information for a subset of active flows needs to be maintained for a very short period of time, and then all the resources used for keeping the state information can be reclaimed.

  2. Performance study of Active Queue Management methods: Adaptive GRED, REDD, and GRED-Linear analytical model

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    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.

  3. 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.

  4. 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

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

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    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.

  6. Multicast Services of QoS-Aware Active Queue Management over IP Multimedia Applications

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    Hwang, I.-Shyan; Hwang, Bor-Jiunn; Chang, Pen-Ming

    2010-10-01

    Recently, the multimedia services such as IPTV, video conference emerges to be the main traffic source. When UDP coexists with TCP, it induces not only congestion collapse but also unfairness problem. In this paper, a new Active Queue Management (AQM) algorithm, called Traffic Sensitive Active Queue Management (TSAQM), is proposed for providing multimedia services. The TSAQM comprise Dynamic Weight Allocate Scheme (DWAS) and Service Guarantee Scheme (SGS), the purpose of DWAS is to allocate resource with fairness and high end-user utility, and the purpose of SGS is to determine the satisfactory threshold (TH) and threshold region (TR). Several objectives of this proposed scheme include achieving high end-user utility for video service, considering the multicast as well as unicast proprieties to meet inter-class fairness and achieving the QoS requirement by adjusting the thresholds adaptively based on traffic situations.

  7. Rate-Based Active Queue Management for TCP Flows over Wired and Wireless Networks

    OpenAIRE

    Jun Wang; Min Song

    2007-01-01

    Current active queue management (AQM) and TCP protocol are designed and tuned to work well on wired networks where packet loss is mainly due to network congestion. In wireless networks, however, communication links suffer from significant transmission bit errors and handoff failures. As a result, the performance of TCP flows is significantly degraded. To mitigate this problem, we analyze existing AQM schemes and propose a rate-based exponential AQM (REAQM) scheme. The proposed REAQM scheme u...

  8. Multivariate analysis for performance evaluation of active-queue-management mechanisms in the Internet

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    Eguchi, Tomoya; Ohsaki, Hiroyuki; Murata, Masayuki

    2002-07-01

    AQM (Active Queue Management) mechanism, which performs congestion control at a router for assisting the end-to-end congestion control mechanism of TCP, has been actively studied by many researchers. For instance, RED (Random Early Detection) is a representative AQM mechanism, which drops arriving packets with a probability being proportional to its average queue length. The RED router has four control parameters, and its effectiveness heavily depends on a choice of these control parameters. This is why many researches on the parameter tuning of RED control parameters have been performed. However, most of those studies have investigated the effect of RED control parameters on its performance from a small number of simulation results. In this paper, we therefore statistically analyze a great number of simulation results using the multivariate analysis. We quantitatively show the relation between RED control parameters and its performance.

  9. Predictive functional control for active queue management in congested TCP/IP networks.

    Science.gov (United States)

    Bigdeli, N; Haeri, M

    2009-01-01

    Predictive functional control (PFC) as a new active queue management (AQM) method in dynamic TCP networks supporting explicit congestion notification (ECN) is proposed. The ability of the controller in handling system delay along with its simplicity and low computational load makes PFC a privileged AQM method in the high speed networks. Besides, considering the disturbance term (which represents model/process mismatches, external disturbances, and existing noise) in the control formulation adds some level of robustness into the PFC-AQM controller. This is an important and desired property in the control of dynamically-varying computer networks. In this paper, the controller is designed based on a small signal linearized fluid-flow model of the TCP/AQM networks. Then, closed-loop transfer function representation of the system is derived to analyze the robustness with respect to the network and controller parameters. The analytical as well as the packet-level ns-2 simulation results show the out-performance of the developed controller for both queue regulation and resource utilization. Fast response, low queue fluctuations (and consequently low delay jitter), high link utilization, good disturbance rejection, scalability, and low packet marking probability are other features of the developed method with respect to other well-known AQM methods such as RED, PI, and REM which are also simulated for comparison.

  10. Performance Analysis Of Active Queue Management AQM In VOIP Using Different Voice Encoder Scheme

    OpenAIRE

    Samir Eid Mohammed; Mohamed H. M. Nerma

    2015-01-01

    Abstract Voice over Internet Protocol VoIP is a rapidly growing technology that enables transport of voice over data networks such as Ethernet Wide area networks WANs due to this important different codec scheme is developed to meet the QoS requirements. This thesis presents a comprehensive study about the impact of active queue management AQM on Voice over Internet Protocol VoIP quality of service using different codec scheme such as G711 G723 G729 and GSM using simulations tools. The evalua...

  11. QoS-Aware Active Queue Management for Multimedia Services over the Internet

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    Hwang I-Shyan

    2011-01-01

    Full Text Available Recently, with multimedia services such as IPTV, video conferencing has emerged as a main traffic source. When UDP coexists with TCP, it induces not only congestion collapse but also an unfairness problem. In this paper, a new Active Queue Management algorithm, called Traffic Sensitive Active Queue Management (TSAQM, is proposed for providing multimedia services in routers. The TSAQM is comprised of Dynamic Weight Allocate Scheme (DWAS and Service Guarantee Scheme (SGS. The purpose of DWAS is to fairly allocate resources with high end-user utility, and the SGS is to determine the satisfactory threshold (TH and threshold region (TR. Besides, a multiqueue design for different priority traffic, and threshold TH and threshold region TR is proposed to achieve the different QoS requirements. Several objectives of this proposed scheme include achieving high end user utility for video services, considering the multicast as well as unicast proprieties to meet interclass fairness, and achieving the QoS requirement by adaptively adjusting the thresholds based on the traffic situations. Performance comparisons with the GRED-I are in terms of packet dropping rate and throughput to highlight the better behavior of the proposed schemes due to taking into account the fairness and different weights for video layers.

  12. Survival of the Fittest: An Active Queue Management Technique for Noisy Packet Flows

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    Shirish S. Karande

    2007-01-01

    Full Text Available We present a novel active queue management (AQM technique to demonstrate the efficacy of practically harnessing the predictive utility of SSR indications for improved video communication. We consider a network within which corrupted packets are relayed over multiple hops, but a certain percentage of packets needs to be dropped at an intermediate node due to congestion. We propose an AQM technique, survival of the fittest (SOTF, to be employed at the relay node, within which we use packet state information, available from SSR indications and checksums, to drop packets with the highest corruption levels. On the basis of actual 802.11b measurements we show that such a side information (SI aware processing within the network can provide significant performance benefits over an SI-unaware scheme, random queue management (RQM, which is forced to randomly discard packets. With trace-based simulations, we show the utility of the proposed AQM technique in improving the error recovery performance of cross-layer FEC schemes. Finally, with the help of H.264-based video simulations these improvements are shown to translate into a significant improvement in video quality.

  13. Design of Active Queue Management for Robust Control on Access Router for Heterogeneous Networks

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    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.

  14. Performance Analysis Of Active Queue Management AQM In VOIP Using Different Voice Encoder Scheme

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    Samir Eid Mohammed

    2015-08-01

    Full Text Available Abstract Voice over Internet Protocol VoIP is a rapidly growing technology that enables transport of voice over data networks such as Ethernet Wide area networks WANs due to this important different codec scheme is developed to meet the QoS requirements. This thesis presents a comprehensive study about the impact of active queue management AQM on Voice over Internet Protocol VoIP quality of service using different codec scheme such as G711 G723 G729 and GSM using simulations tools. The evaluation is done using the OPNET Modeler which provides a convenient and easy-to-use platform for simulating large scale networks and this also give a power to go through different levels of designing a network even with the ability to program the mechanism you want which is used here to implement two types of AQM mechanism which is not included by default in the OPNET and these two mechanisms are ARED and GRED. The performance metrics used in the study are jitter throughput and delay. The study shows that G.711 and G729 codecs in a simulation gives a significant result for the performance of VoIP that codec G711 and G.729A has acceptable throughput and less deviation of received to transmit packet as compared to GSM and G.723 also average delay like end to end delay and Voice jitter is lesser in codec G711 and G.729 as compared to the other two referenced codecs.

  15. Packet marking function of active queue management mechanism: should it be linear, concave, or convex?

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    Ohsaki, Hiroyuki; Murata, Masayuki

    2004-09-01

    Recently, several gateway-based congestion control mechanisms have been proposed to support the end-to-end congestion control mechanism of TCP (Transmission Control Protocol). In this paper, we focus on RED (Random Early Detection), which is a promising gateway-based congestion control mechanism. RED randomly drops an arriving packet with a probability proportional to its average queue length (i.e., the number of packets in the buffer). However, it is still unclear whether the packet marking function of RED is optimal or not. In this paper, we investigate what type of packet marking function, which determines the packet marking probability from the average queue length, is suitable from the viewpoint of both steady state and transient state performances. Presenting several numerical examples, we investigate the advantages and disadvantages of three packet marking functions: linear, concave, and convex. We show that, although the average queue length in the steady state becomes larger, use of a concave function improves the transient behavior of RED and also realizes robustness against network status changes such as variation in the number of active TCP connections.

  16. Active Queue Management Mechanisms for Real-Time Traffic in MANETs

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    2001-12-01

    do not drop any packet. Finally, if the queue size exceeds the buffer capacity , we discard the packet with sequence number that is a multiple of SD3...the maximum buffer capacity . That means if the queue size exceeds the third threshold for OUT packets and an OUT packet has arrived, an OUT packet...There are two thresholds Θ1, Θ2 and the maximum buffer capacity is K. The instantaneous queue size is L. For each incoming packet, the queue length is

  17. STUDY THE EFFECTIVENESS APPLICATIONS OF FUZZY CONTROLLER WITH TWO ENTRANCES IN THE SYSTEM OF ACTIVE QUEUE MANAGEMENT THE PACKETS IN TCP/IP NETWORKS

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    O. V. Nevdachyna

    2016-01-01

    Full Text Available The paper presents an approach to solving the overloading problem in TCP/IP networks. Offered fuzzy controller with two inputs for system of active queue management packages in TCP/IP networks, and investigated its use in these systems with a random change of traffic load. Proposed controller has two inputs, one of which is the value of the difference between the current queue length and the second – the difference between the current level of usage of the buffer. The output of the fuzzy controller calculates the probability of discarding packet.Mathematical model system of active queue management that is studied is presented in an interactive MATLAB system, in wherein also is demonstrated the processes occurring in the system with a random change of traffic load. The research results show that the AQM-system with fuzzy controller with two entrances stable enough maintains the desired current length the queue for sufficiently small values of the probability of dropping/marking packets (at acceptable size of queue q0= 200 packets, the average probability of dropping / marking is not more than 3,5×10–3 or less 0,35% packets is discarded or marked from the total number of incoming packets. The results obtained will help improve the efficiency of the functioning and operation of TCP / IP networks by increasing data transmission quality. this happens due introduction of the proposed controller at the design of new, more efficient routers for networks to minimize the delay of information.

  18. The WorkQueue project: A task queue for the CMS workload management system

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    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

  19. 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

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

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    Khoshnevisan, Ladan; Salmasi, Farzad R.

    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.

  1. 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.

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

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    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.

  3. Adaptive Queue Management with Restraint on Non-Responsive Flows

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    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.

  4. Optimal Control for Bufferbloat Queue Management Using Indirect Method with Parametric Optimization

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    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.

  5. 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.

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

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

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    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.

  8. 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.

  9. Active Methodologies in a Queueing Systems Course for Telecommunication Engineering Studies

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    Garcia, J.; Hernandez, A.

    2010-01-01

    This paper presents the results of a one-year experiment in incorporating active methodologies in a Queueing Systems course as part of the Telecommunication Engineering degree at the University of Zaragoza, Spain, during the period of adaptation to the European Higher Education Area. A problem-based learning methodology has been introduced, and…

  10. BOB-RED queue management for IEEE 802.15.4 wireless sensor networks

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    Wu Jean-Lien

    2011-01-01

    Full Text Available Abstract Multimedia services over resource constrained wireless sensor networks (WSNs face a performance bottleneck issue from the gateway node to the sink node. Therefore, the queue management at the gateway node is crucial for diversified messages conveyed from the front nodes to the sink node. In this article, beacon order-based random early detection (BOB-RED queue management is proposed. BOB-RED is a dynamic adaptation scheme based on adjusting beacon interval and superframe duration in the IEEE 802.15.4 MAC superframe accompanied with RED queue management scheme to increase the transmission efficiency of multimedia over WSNs. We focus on the performance improvement upon different traffic loads over WSNs. Evaluation metrics include end-to-end delay, packet delivery ratio, and energy consumption in IEEE 802.15.4 beacon enabled mode. Simulation results show that BOB-RED can effectively decrease end-to-end delay and energy consumption compared to the DropTail scheme.

  11. Queueing Networks.

    Science.gov (United States)

    1979-12-01

    important study in many of the above application rather than single queues. Markov process theory did not provide a rich enough body of knowledge and...of five subareas called: decomposition, recomposition , departures, feedback queues and queues with non-renewal arrivals. Few new results seem to have... Recomposition studies, likewise, have received scant attention since 1975 as is also true for queues with non-renewal arrivals. We suggest that the

  12. 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.

  13. 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.

  14. 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.

  15. 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

    2017-07-24

    As health care shifts toward patient-centered care, wait times have received increasing scrutiny as an important metric for patient satisfaction. Long queues form when radiology practices inefficiently service their customers, leading to customer dissatisfaction and a lower perception of value. This article describes a four-step framework for radiology practices to resolve problematic queues: (1) analyze factors contributing to queue formation; (2) improve processes to reduce service times; (3) reduce variability; (4) address the psychology of queues. Copyright © 2017 American College of Radiology. Published by Elsevier Inc. All rights reserved.

  16. WQM: An Aggregation-aware Queue Management Scheme for IEEE 802.11n based Networks

    KAUST Repository

    Showail, Ahmad

    2014-08-17

    Choosing the right buffer size in Wi-Fi networks is challenging due to the dynamic nature of the wireless environment. Over buffering or \\'bufferbloat\\' may produce unacceptable end-to-end delays, while static small buffers may limit the performance gains that can be achieved with various 802.11n enhancements, such as frame aggregation. We propose WQM, a queue management scheme customized for wireless networks. WQM adapts the buffer size based on measured link characteristics and network load. Furthermore, it accounts for aggregate length when deciding about the optimal buffer size. We implement WQM on Linux and evaluate it on a wireless testbed. WQM reduces the end-to-end delay by up to 8x compared to Linux default buffer size, and 2x compared to CoDel, the state-of-the-art bufferbloat solution, while achieving comparable network goodput. Further, WQM improves fairness as it limits the ability of a single flow to saturate the buffer.

  17. Big queues

    CERN Document Server

    Ganesh, Ayalvadi; Wischik, Damon

    2004-01-01

    Big Queues aims to give a simple and elegant account of how large deviations theory can be applied to queueing problems. Large deviations theory is a collection of powerful results and general techniques for studying rare events, and has been applied to queueing problems in a variety of ways. The strengths of large deviations theory are these: it is powerful enough that one can answer many questions which are hard to answer otherwise, and it is general enough that one can draw broad conclusions without relying on special case calculations.

  18. Priority Queues for Computer Simulations

    Science.gov (United States)

    Steinman, Jeffrey S. (Inventor)

    1998-01-01

    The present invention is embodied in new priority queue data structures for event list management of computer simulations, and includes a new priority queue data structure and an improved event horizon applied to priority queue data structures. ne new priority queue data structure is a Qheap and is made out of linked lists for robust, fast, reliable, and stable event list management and uses a temporary unsorted list to store all items until one of the items is needed. Then the list is sorted, next, the highest priority item is removed, and then the rest of the list is inserted in the Qheap. Also, an event horizon is applied to binary tree and splay tree priority queue data structures to form the improved event horizon for event management.

  19. Flow Time Analysis of Load Management Late Arrival Discrete Time Queueing System with Dual Service Rate Using Hypogeometrical Distribution

    Directory of Open Access Journals (Sweden)

    Syed Asif Ali Shah

    2012-01-01

    Full Text Available 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 hypogeometrically 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.

  20. Optimal management for infinite capacity N-policy M/G/1 queue with a removable service station

    Science.gov (United States)

    Chang, Y. C.; Pearn, W. L.

    2011-07-01

    In this article, we consider an infinite capacity N-policy M/G/1 queueing system with a single removable server. Poisson arrivals and general distribution service times are assumed. The server is controllable that may be turned on at arrival epochs or off at service completion epochs. We apply a differential technique to study system sensitivity, which examines the effect of different system input parameters on the system. A cost model for infinite capacity queueing system under steady-state condition is developed, to determine the optimal management policy at minimum cost. Analytical results for sensitivity analysis are derived. We also provide extensive numerical computations to illustrate the analytical sensitivity properties obtained. Finally, an application example is presented to demonstrate how the model could be used in real applications to obtain the optimal management policy.

  1. Queueing Theory With Reneging

    Science.gov (United States)

    2005-09-01

    List Research Leader Integrated Capabilities Doc Data Sht & Dist List Task Manager : Thea Clark 1 Author: S. Bocquet 1 Printed Michael Ling 1 Nigel......particularly in situations where queueing theory forms only a part of the model of a defence system. RELEASE LIMITATION Approved for

  2. 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...

  3. 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.

  4. 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.

  5. 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.

  6. Queues with Choice via Delay Differential Equations

    Science.gov (United States)

    Pender, Jamol; Rand, Richard H.; Wesson, Elizabeth

    Delay or queue length information has the potential to influence the decision of a customer to join a queue. Thus, it is imperative for managers of queueing systems to understand how the information that they provide will affect the performance of the system. To this end, we construct and analyze two two-dimensional deterministic fluid models that incorporate customer choice behavior based on delayed queue length information. In the first fluid model, customers join each queue according to a Multinomial Logit Model, however, the queue length information the customer receives is delayed by a constant Δ. We show that the delay can cause oscillations or asynchronous behavior in the model based on the value of Δ. In the second model, customers receive information about the queue length through a moving average of the queue length. Although it has been shown empirically that giving patients moving average information causes oscillations and asynchronous behavior to occur in U.S. hospitals, we analytically and mathematically show for the first time that the moving average fluid model can exhibit oscillations and determine their dependence on the moving average window. Thus, our analysis provides new insight on how operators of service systems should report queue length information to customers and how delayed information can produce unwanted system dynamics.

  7. 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

    In a system with implicit queue management, to examine gender and socioeconomic status as determinants of waiting time for inpatient surgery, after adjusting for other potential predictors. A cohort of 452 subjects was examined in outpatient clinics of a general hospital and referred to inpatient surgery. They were followed until scheduled hospital admission (n=396) or until the requested procedure no longer was relevant (n=56). We compared waiting time between groups from referral date until hospital admission, using Kaplan-Meier estimates of waiting times and log rank test. A Cox proportional hazards model was used for assessing the risk ratio (RR) of hospital admission for scheduled surgery. Gender and socioeconomic status could not explain variations in waiting time. However, patients with suspected/verified neoplastic disease or a risk of serious deterioration without treatment had markedly shorter waiting times than the reference groups, with adjusted RR (95% confidence intervals (95%CI)) of time to receiving in-patient surgery of 2.3 (1.7-3.0) and 2.0 (1.3-3.0), respectively. Being on sick leave was associated with shorter waiting time, adjusted RR of 1.7 (1.2-2.5). Referrals from within the hospital or other hospitals had also shorter waiting times than referrals from primary health care physicians, adjusted RR=1.4 (1.1-1.8). There was no evidence of bias against women or people in lower socioeconomic classes in this implicit queue management system. However, patients' access to inpatient surgery was associated with malignancy, prognosis, sick leave status, physician experience, referral pattern and the major diagnosis category.

  8. Queueing systems with renovation

    Directory of Open Access Journals (Sweden)

    A. Ya. Kreinin

    1997-01-01

    Full Text Available We study in this paper-single channel queueing systems with renovation. Such models are often encountered in computer science applications. Explicit solutions are discussed for the queues with Poisson input flow and for queues with general input and exponential service times.

  9. 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

  10. 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

  11. Usage of Message Queueing Technologies in the ATLAS Distributed Data Management System

    CERN Document Server

    Calfayan, P; The ATLAS collaboration; Garonne, V

    2011-01-01

    The ATLAS Distributed Data Management system is composed of semi-autonomous, heterogeneous, and independently designed subsystems. To achieve successful operation of such a system, the activities of the agents controlling the subsystems have to be coordinated. In addition, external applications can require to synchronize on events relative to data availability. A common way to proceed is to implement polling strategies within the distributed components, which leads to an increase of the load in the overall system. We describe an alternative based on notifications using standard message queuing. The application of this technology in the distributed system has been exercised.

  12. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  14. 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.

  15. 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...... where Meld takes worst case time o(n). To our knowledge this is the first priority queue implementation that supports Meld in worst case constant time and DeleteMin in logarithmic time....

  16. 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

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

    Directory of Open Access Journals (Sweden)

    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.

  18. 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.

  19. 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

  20. Multiserver queueing networks and the tandem queue model

    Directory of Open Access Journals (Sweden)

    Pierre Le Gall

    1998-01-01

    Full Text Available Using a tandem queue model we evaluate the local “endogenous” (= internal queueing delay in single server and multiserver queueing networks. The new concept of the apparent overall upstream queueing delay(as perceived by the downstream network allows us to analyze the distribution of this local queue by interpolating between the distributions of the tandem queue (generated by a concentration tree and the isolated G/G/squeue. The interpolation coefficients depend on the proportion of “premature departures”, typically interfering in the upstream stage and leaving the considered path without being offered to the considered local queue. On the other hand, local “exogenous” arrivals (from outside the network require the introduction of the “interference delay” concept. Finally, in the case of single server queueing networks, we stress the need to extend the capacities of the buffers, by considering the “worst case” scenario and by using an “equivalent tandem queue” model.

  1. 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...

  2. Waiting for coronary angiography: is there a clinically ordered queue?

    Science.gov (United States)

    Hemingway, H; Crook, A M; Feder, G; Dawson, J R; Timmis, A

    2000-03-18

    Among over 3000 patients undergoing coronary angiography in the absence of a formal queue-management system, we found that a-priori urgency scores were strongly associated with waiting times, prevalence of coronary-artery disease, rate of revascularisation, and mortality. These data challenge the widely held assumption that such waiting lists are not clinically ordered; however, the wide variation in waiting times within urgency categories suggests the need for further improvements in clinical queueing.

  3. 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...

  4. Priority-queue framework: Programs

    DEFF Research Database (Denmark)

    Katajainen, Jyrki

    2009-01-01

    This is an electronic appendix to the article "Generic-programming framework for benchmarking weak queues and its relatives". The report contains the programs related to our priority-queue framework. Look at the CPH STL reports 2009-3 and 2009-4 to see examples of other component frameworks....

  5. 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...

  6. Queueing theory and network applications

    CERN Document Server

    Takahashi, Yutaka; Yue, Wuyi; Nguyen, Viet-Ha

    2016-01-01

    The 16 papers of this proceedings have been selected from the submissions to the 10th  International Conference on Queueing Theory and Network Applications (QTNA2015) held on 17-20 August, 2015 in Ha Noi and Ha Long, Vietnam. All contributions discuss theoretical and practical issues connected with queueing theory and its applications in networks and other related fields. The book brings together researchers, scientists and practitioners from the world and offers an open forum to share the latest important research accomplishments and challenging problems in the area of queueing theory and network applications.

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

    Directory of Open Access Journals (Sweden)

    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.

  8. JobCenter: an open source, cross-platform, and distributed job queue management system optimized for scalability and versatility.

    Science.gov (United States)

    Jaschob, Daniel; Riffle, Michael

    2012-07-30

    Laboratories engaged in computational biology or bioinformatics frequently need to run lengthy, multistep, and user-driven computational jobs. Each job can tie up a computer for a few minutes to several days, and many laboratories lack the expertise or resources to build and maintain a dedicated computer cluster. JobCenter is a client-server application and framework for job management and distributed job execution. The client and server components are both written in Java and are cross-platform and relatively easy to install. All communication with the server is client-driven, which allows worker nodes to run anywhere (even behind external firewalls or "in the cloud") and provides inherent load balancing. Adding a worker node to the worker pool is as simple as dropping the JobCenter client files onto any computer and performing basic configuration, which provides tremendous ease-of-use, flexibility, and limitless horizontal scalability. Each worker installation may be independently configured, including the types of jobs it is able to run. Executed jobs may be written in any language and may include multistep workflows. JobCenter is a versatile and scalable distributed job management system that allows laboratories to very efficiently distribute all computational work among available resources. JobCenter is freely available at http://code.google.com/p/jobcenter/.

  9. JobCenter: an open source, cross-platform, and distributed job queue management system optimized for scalability and versatility

    Directory of Open Access Journals (Sweden)

    Jaschob Daniel

    2012-07-01

    Full Text Available Abstract Background Laboratories engaged in computational biology or bioinformatics frequently need to run lengthy, multistep, and user-driven computational jobs. Each job can tie up a computer for a few minutes to several days, and many laboratories lack the expertise or resources to build and maintain a dedicated computer cluster. Results JobCenter is a client–server application and framework for job management and distributed job execution. The client and server components are both written in Java and are cross-platform and relatively easy to install. All communication with the server is client-driven, which allows worker nodes to run anywhere (even behind external firewalls or “in the cloud” and provides inherent load balancing. Adding a worker node to the worker pool is as simple as dropping the JobCenter client files onto any computer and performing basic configuration, which provides tremendous ease-of-use, flexibility, and limitless horizontal scalability. Each worker installation may be independently configured, including the types of jobs it is able to run. Executed jobs may be written in any language and may include multistep workflows. Conclusions JobCenter is a versatile and scalable distributed job management system that allows laboratories to very efficiently distribute all computational work among available resources. JobCenter is freely available at http://code.google.com/p/jobcenter/.

  10. On some queue length controlled stochastic processes

    Directory of Open Access Journals (Sweden)

    Lev Abolnikov

    1990-01-01

    Full Text Available The authors study the input, output and queueing processes in a general controlled single-server bulk queueing system. It is supposed that inter-arrival time, service time, batch size of arriving units and the capacity of the server depend on the queue length.

  11. 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...

  12. Queueing networks with a single shared server

    NARCIS (Netherlands)

    M.A.A. Boon (Marko); R.D. van der Mei (Rob); E.M.M. Winands

    2011-01-01

    htmlabstractWe study a queueing network with a single shared server, that serves the queues in a cyclic order according to the gated service discipline. External customers arrive at the queues according to independent Poisson processes. After completing service, a customer either leaves the

  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. Prediction of Ready Queue Processing Time in Multiprocessor Environment Using Lottery Scheduling (ULS

    Directory of Open Access Journals (Sweden)

    Amita CHOUDHARY

    2011-01-01

    Full Text Available While in multi-user environment, CPU has to manage lot of requests generated over the same time. Waiting queue of processes generates a problem of scheduling for processors. Designers and hardware architects have suggested system of multiprocessors to overcome the queue length. Lottery scheduling is one such method where processes in waiting queue are selected through a chance manner. This opens a way to use probability models to get estimates of system parameters. This paper is an application where the processing time of jobs in ready queue is predicted using the sampling method under the k-processors environment (k>1.The random selection of one process by each of k processors through without replacement method is a sample data set which helps in the prediction of possible ready queue processing time. Some theorems are established and proved to get desired results in terms of confidence intervals.

  15. Service by a Queue and a Cart

    OpenAIRE

    E. G. Coffman, Jr.; Gilbert, E.N.

    1992-01-01

    Items arrive randomly at a production facility that functions as a single-server queueing system. The items might represent parts, raw material, etc. and the server might be a factory worker or a machine in a production line. Following service, items are placed in a buffer where they are accumulated before delivery to a customer or some downstream activity in a production line. In practice, the buffer might be called a hopper; it may take the form of a cart or a pallet moved by a forklift. Fo...

  16. Research into Queueing Network Theory.

    Science.gov (United States)

    1977-09-01

    recomposition , and stretching) that have been considered in queueing networks map arrival processes that are Markov renewal processes into other...research under this contract are marked by a double asterik(**). Other references are to work cited in the body of the report and are not ideas

  17. Equilibrium Arrival Times to Queues

    DEFF Research Database (Denmark)

    Breinbjerg, Jesper; Østerdal, Lars Peter

    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...

  18. 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...

  19. 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;

  20. Terminal appointment system design by non-stationary M(t)/E /c(t) queueing model and genetic algorithm

    DEFF Research Database (Denmark)

    Chen, G.; Govindan, Kannan; Yang, Z.-Z.

    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...

  1. Mathematical analysis of single queue multi server and multi queue multi server queuing models: comparison study

    OpenAIRE

    Vijay Prasad; Badshah V.H; Tariq Ahmad Koka

    2015-01-01

    In the research paper entitled Mathematical Analysis of Single Queue Multi Server and Multi Queue Multi Server Queuing Model, Prasad and Badshah [7] were proved that single queue multi server model is better than multi queue multi server model, and discussed the relation between the performance measures of these two models, and derive the mathematical equations. In this paper we derive the total cost with assumption of certain Waiting cost in both cases. Also, prove that the expected total co...

  2. Isomorphs of a class of Queueing systems

    Directory of Open Access Journals (Sweden)

    A. Ghosal

    1979-01-01

    Full Text Available Restricted isomorphism between two queueing systems implies that they have equivalent distribution function for at least one (but not all output elements (e.g. waiting time, queue size, idle time, etc.. Quasi-isomorphism implies an approximate equivalence. Most of the single-server queueing systems can be approximated by a quasi-isomorphic system which has a gamma inter-arrival and gamma service distributions (Ep/Eq/1.

  3. 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

  4. Analysis on Realization of Sequential Queue

    Science.gov (United States)

    Wang, Min

    Analyzed and introduced the sequential storage structure of the queue, detailed analyzed several specific methods for the circular queue to resolve the "false overflow", gave the algorithm descriptions in C of the corresponding basic operations of the queue, compared and analyzed each algorithm the time complexity and the space complexity, so as to complement and play a guiding role in the relevant chapters in "Data Structure" curriculum.

  5. Effect of queue discipline on the performance of a queueing system ...

    African Journals Online (AJOL)

    The comparison of the systems were carried out by writing an appropriate program in BASIC to simulate the queue discipline. This is due to the versatile nature of simulation and the fact that it is extremely difficult to obtain numerical results mathematically for the single server queue when the queue discipline is not FIFO and ...

  6. A two-queue polling model with two priority levels in the first queue

    NARCIS (Netherlands)

    Boon, M.A.A.; Adan, I.J.B.F.; Boxma, O.J.

    2008-01-01

    In this paper we consider a single-server cyclic polling system consisting of two queues. Between visits to successive queues, the server is delayed by a random switch-over time. Two types of customers arrive at the first queue: high and low priority customers. For this situation the following

  7. A two-queue polling model with two priority levels in the first queue

    NARCIS (Netherlands)

    Boon, M.A.A.; Adan, I.J.B.F.; Boxma, O.J.

    2010-01-01

    In this paper we consider a single-server cyclic polling system consisting of two queues. Between visits to successive queues, the server is delayed by a random switch-over time. Two types of customers arrive at the first queue: high and low priority customers. For this situation the following

  8. Adaptive circular queue image steganography with RSA cryptosystem

    National Research Council Canada - National Science Library

    Jain, Mamta; Lenka, Saroj Kumar; Vasistha, Sunil Kumar

    2016-01-01

    ... circular queue least significant bits (LSBs) substitution. The data structure queue is employed dynamically in resource distribution between multiple communication recipients and once secret information transmitted asynchronously...

  9. 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.

  10. Curing the queue

    NARCIS (Netherlands)

    Zonderland, Maartje Elisabeth

    2012-01-01

    In this dissertation we study several problems related to the management of healthcare and the cure of disease. In each chapter a hospital capacity distribution problem is analyzed using techniques from operations research, also known as mathematical decision theory. The problems considered are

  11. Two queues with non-stochastic arrivals

    NARCIS (Netherlands)

    Walton, N.S.

    2014-01-01

    This article presents a paradigm where no stochastic assumptions are made on a queue’s arrival process. To this end, we study two queueing systems which exhibit a form of stability under an arbitrary arrival process. The first queueing system applies Blackwell’s Approachability Theorem and the

  12. The single server semi-markov queue

    NARCIS (Netherlands)

    de Smit, J.H.A.

    1986-01-01

    A general model for the single server semi-Markov queue is studied. Its solution is reduced to a matrix factorization problem. Given this factorization, results are obtained for the distributions of actual and virtual waiting times, queue lengths both at arrival epochs and in continuous time, the

  13. Monotonicity in the limited processor sharing queue

    NARCIS (Netherlands)

    M. Nuyens; W. van der Weij (Wemke)

    2008-01-01

    htmlabstractWe study a processor sharing queue with a limited number of service positions and an infinite buffer. The occupied service positions share an underlying resource. We prove that for service times with a decreasing failure rate, the queue length is stochastically decreasing in the number

  14. Gaussian queues in light and heavy traffic

    NARCIS (Netherlands)

    Dębicki, K.; Kosiński, K.M.; Mandjes, M.

    2012-01-01

    In this paper we investigate Gaussian queues in the light-traffic and in the heavy-traffic regime. Let $Q^{(c)}_{X}\\equiv\\{Q^{(c)}_{X}(t):t\\ge0\\}$ denote a stationary buffer content process for a fluid queue fed by the centered Gaussian process X≡{X(t):t∈ℝ} with stationary increments, X(0)=0,

  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. 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

  17. 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

  18. Fuzzy service control of queueing systems.

    Science.gov (United States)

    Phillis, Y A; Zhang, R

    1999-01-01

    We consider queueing systems in which the service rate is the controlled variable. The cost depends on the queue length and selected rate. The objective is to choose the service rate dynamically, based on the state of the system so as to minimize the average cost over an infinite horizon. Six classes, either known in the literature or new, are studied in detail: queueing systems with vacations, single-server queueing systems with and without switching costs, and tandem queueing systems with and without service costs. A novel approach is presented here using fuzzy control to solve these problems. Simulation shows that the approach is efficient and promising, especially in cases where analytical solutions do not exist.

  19. Stres in Manager Activities

    Directory of Open Access Journals (Sweden)

    Luboš Socha

    2017-07-01

    Full Text Available The article presents and clarifies the topic that was focused on the influence of stress factors in the manger’s activity. The subject of the evaluation was the impact of stress on the work and performance of managers. Using the methods we used, we learned about whether stress is a daily part of the managerial position from the point of view of the managers themselves. Furthermore, we are dealing with the issue of the extent to which stressful situations affect the quality and efficiency of the work of managers and we are looking for the main causes of stress in the manager’s work. At the same time, we address the possibilities of managing stress, eliminating stress in the work environment, and streamlining workflows in the form of stress stimuli. Last but not least, we have focused on identifying the level of management stress management to support the management of the stresses in organizations where individual managers operate.

  20. MANAGEMENT AND SPORTING ACTIVITIES

    Directory of Open Access Journals (Sweden)

    MONICA DELIA BÎCĂ

    2015-10-01

    Full Text Available “Using applied science in sport management as creates opportunities for rationalization and systematization of sports activity, relying on the knowledge and application of the laws that control the dynamics and phenomena. Management is on the border between art and science. Arts management is manifested by "science" as opposed to use and harness the creative compromise that can produce increased efficiency and effectiveness.”

  1. Waiting times in queueing networks with a single shared server

    NARCIS (Netherlands)

    Boon, M.A.A; van der Mei, R.D.; Winands, E.M.M.

    2013-01-01

    We study a queueing network with a single shared server that serves the queues in a cyclic order. External customers arrive at the queues according to independent Poisson processes. After completing service, a customer either leaves the system or is routed to another queue. This model is very

  2. Regular Simple Queues of Protein Contact Maps.

    Science.gov (United States)

    Guo, Qiang-Hui; Sun, Lisa Hui; Wang, Jian

    2017-01-01

    A protein fold can be viewed as a self-avoiding walk in certain lattice model, and its contact map is a graph that represents the patterns of contacts in the fold. Goldman, Istrail, and Papadimitriou showed that a contact map in the 2D square lattice can be decomposed into at most two stacks and one queue. In the terminology of combinatorics, stacks and queues are noncrossing and nonnesting partitions, respectively. In this paper, we are concerned with 2-regular and 3-regular simple queues, for which the degree of each vertex is at most one and the arc lengths are at least 2 and 3, respectively. We show that 2-regular simple queues are in one-to-one correspondence with hill-free Motzkin paths, which have been enumerated by Barcucci, Pergola, Pinzani, and Rinaldi by using the Enumerating Combinatorial Objects method. We derive a recurrence relation for the generating function of Motzkin paths with [Formula: see text] peaks at level i, which reduces to the generating function for hill-free Motzkin paths. Moreover, we show that 3-regular simple queues are in one-to-one correspondence with Motzkin paths avoiding certain patterns. Then we obtain a formula for the generating function of 3-regular simple queues. Asymptotic formulas for 2-regular and 3-regular simple queues are derived based on the generating functions.

  3. ANALYSIS OF MULTI-SERVER SINGLE QUEUE

    Directory of Open Access Journals (Sweden)

    Emmanuel John Ekpenyong

    2011-04-01

    Full Text Available Queuing properties such as expected total service time and its variance and some performance measures like the expected number of phases in the system, expected number of phases in the queue, expected number of customers in the queue, expected waiting time in the queue and in the system as well as the number of customers in the system have been derived for an  M/Ek/s: ( /FCFS queuing model with k identified stages in series, each with average service time of . Also, numerical illustrations have also been used to illustrate the results.

  4. 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.

  5. Queueing Models and Stability of Message Flows in Distributed Simulators of Open Queueing Networks

    OpenAIRE

    Gupta, Manish; Kumar, Anurag; Shorey, Rajeev

    1996-01-01

    In this paper we study message flow processes in distributed simulators of open queueing networks. We develop and study queueing models for distributed simulators with maximum lookahead sequencing. We characterize the external arrival process, and the message feedback process in the simulator of a simple queueing network with feedback. We show that a certain natural modelling construct for the arrival process is exactly correct, whereas an obvious model for the feedback process is wrong; we t...

  6. The theory of networks of single server queues and the tandem queue model

    Directory of Open Access Journals (Sweden)

    Pierre Le Gall

    1997-01-01

    Full Text Available We consider the stochastic behavior of networks of single server queues when successive service times of a given customer are highly correlated. The study is conducted in two particular cases: 1 networks in heavy traffic, and 2 networks in which all successive service times have the same value (for a given customer, in order to avoid the possibility of breaking up the busy periods. We then show how the local queueing delay (for an arbitrary customer can be derived through an equivalent tandem queue on the condition that one other local queueing delay is added: the jitter delay due to the independence of partial traffic streams.

  7. 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.

  8. ANALYSIS OF MULTI-SERVER SINGLE QUEUE

    National Research Council Canada - National Science Library

    Emmanuel John Ekpenyong; Nse S Udoh

    2011-01-01

    Queuing properties such as expected total service time and its variance and some performance measures like the expected number of phases in the system, expected number of phases in the queue, expected...

  9. Queues with Congestion-dependent Feedback

    OpenAIRE

    van Foreest, N.D.

    2004-01-01

    This dissertation expands the theory of feedback queueing systems and applies a number of these models to a performance analysis of the Transmission Control Protocol, a flow control protocol commonly used in the Internet.

  10. 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.

  11. Network resiliency through memory health monitoring and proactive management

    Science.gov (United States)

    Andrade Costa, Carlos H.; Cher, Chen-Yong; Park, Yoonho; Rosenburg, Bryan S.; Ryu, Kyung D.

    2017-11-21

    A method for managing a network queue memory includes receiving sensor information about the network queue memory, predicting a memory failure in the network queue memory based on the sensor information, and outputting a notification through a plurality of nodes forming a network and using the network queue memory, the notification configuring communications between the nodes.

  12. Density profiles of the exclusive queueing process

    OpenAIRE

    Arita, Chikashi; Schadschneider, Andreas

    2012-01-01

    The exclusive queueing process (EQP) incorporates the exclusion principle into classic queueing models. It can be interpreted as an exclusion process of variable system length. Here we extend previous studies of its phase diagram by identifying subphases which can be distinguished by the number of plateaus in the density profiles. Furthermore the influence of different update procedures (parallel, backward-ordered, continuous time) is determined.

  13. Some Problems of Queues with Feedback.

    Science.gov (United States)

    1978-11-01

    0 — t 0 < t1 < t 2 < ... < t < (t n ) is the sequence of output epoc hs. Let N~ — N(t +) be the vector of queue lengths at t + . The entry NC...Feedback” , ~% mt . Set., 24, 168—180. 161 d’Avignon , C. R. and Disney, R. L. (1978) “EquIvalence for Feedback Queues with Poisson Arrivals

  14. The JCMT observing queue and recipe sequencer

    Science.gov (United States)

    Kackley, Russell D.; Rees, Nicholas P.; Walther, Craig; Jenness, Tim

    2004-09-01

    The James Clerk Maxwell Telescope (JCMT), the world's largest sub-mm telescope, will soon be switching operations from a VAX/VMS based control system to a new, Linux-based, Observatory Control System1 (OCS). A critical part of the OCS is the set of tasks that are associated with the observation queue and the observing recipe sequencer: 1) the JCMT observation queue task 2) the JCMT instrument task, 3) the JCMT Observation Sequencer (JOS), and 4) the OCS console task. The JCMT observation queue task serves as a staging area for observations that have been translated from the observer's science program into a form suitable for the various OCS subsystems. The queue task operates by sending the observation at the head of the queue to the JCMT instrument task and then waits for the astronomer to accept the data before removing the observation from the queue. The JCMT instrument task is responsible for running up the set of tasks required to observe with a particular instrument at the JCMT and passing the observation on to the JOS. The JOS is responsible for executing the observing recipe, pausing/continuing the recipe when commanded, and prematurely ending or aborting the observation when commanded. The OCS console task provides the user with a GUI window with which they can control and monitor the observation queue and the observation itself. This paper shows where the observation queue and recipe sequencer fit into the JCMT OCS, presents the design decisions that resulted in the tasks being structured as they are, describes the external interfaces of the four tasks, and details the interaction between the tasks.

  15. Simulation of queue with cyclic service in signalized intersection system

    Directory of Open Access Journals (Sweden)

    Muhammad Dermawan Mulyodiputro

    2015-03-01

    Full Text Available The simulation was implemented by modeling the queue with cyclic service in the signalized intersection system. The service policies used in this study were exhaustive and gated, the model was the M/M/1 queue, the arrival rate used was Poisson distribution and the services rate used was Exponential distribution. In the gated service policy, the server served only vehicles that came before the green signal appears at an intersection. Considered that there were 2 types of exhaustive policy in the signalized intersection system, namely normal exhaustive (vehicles only served during the green signal was still active, and exhaustive (there was the green signal duration addition at the intersection, when the green signal duration at an intersection finished. The results of this queueing simulation program were to obtain characteristics and performance of the system, i.e. average number of vehicles and waiting time of vehicles in the intersection and in the system, as well as system utilities. Then from these values, it would be known which of the cyclic service policies (normal exhaustive, exhaustive and gated was the most suitable when applied to a signalized intersection system

  16. 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.

  17. Applying queueing theory to single machine systems subject to interruptions.

    NARCIS (Netherlands)

    Wu, K.; McGinnis, L.F.; Zwart, A.P.

    2011-01-01

    Queueing models are commonly applied to quantify the performance of production systems. Prior research has usually focused on deriving queueing models for a specific type of interruptions. However, machines generally suffer multiple types of interruptions in practical manufacturing systems. To

  18. Toward Concurrent Lock-Free Queues on GPUs

    National Research Council Canada - National Science Library

    ZHANG, Xiangyu; DENG, Yangdong; MU, Shuai

    2014-01-01

    .... In this work, we proposed an efficient concurrent queue data structure for GPU computing. The GPU based provably correct, lock-free FIFO queue allows a massive number of concurrent producers and consumers...

  19. The power-series algorithm for Markovian queueing networks

    NARCIS (Netherlands)

    van den Hout, W.B.; Blanc, J.P.C.

    1994-01-01

    A newversion of the Power-Series Algorithm is developed to compute the steady-state distribution of a rich class of Markovian queueing networks. The arrival process is a Multi-queue Markovian Arrival Process, which is a multi-queue generalization of the BMAP. It includes Poisson, fork and

  20. Threshold queueing describes the fundamental diagram of uninterrupted traffic

    NARCIS (Netherlands)

    Baër, Niek; Boucherie, Richardus J.; van Ommeren, Jan C.W.

    2012-01-01

    Queueing due to congestion is an important aspect of road traffic. This paper provides a brief overview of queueing models for traffic and a novel threshold queue that captures the main aspects of the empirical shape of the fundamental diagram. Our numerical results characterises the sources of

  1. 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

  2. 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

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

    Directory of Open Access Journals (Sweden)

    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.

  4. Convergence of a Queueing System in Heavy Traffic with General Abandonment Distributions

    Science.gov (United States)

    2010-10-08

    3 in Reiman [27]. We circumvent the use of Reiman’s “Snap-shot Principle” and a comparison result with a non-abandoning queue used in Reed and Ward...4):2606–2650, 2005. 37 [5] R. Atar, A. Mandelbaum, and M. I. Reiman . Scheduling a multi class queue with many exponential servers: asymptotic... Reiman Designing a call center with impatient cus- tomers. Manufacturing and Service Oper. Management, 4(1A):208–227, 2002. [15] J. M. George and J. M

  5. A Queue Simulation Tool for a High Performance Scientific Computing Center

    Science.gov (United States)

    Spear, Carrie; McGalliard, James

    2007-01-01

    The NASA Center for Computational Sciences (NCCS) at the Goddard Space Flight Center provides high performance highly parallel processors, mass storage, and supporting infrastructure to a community of computational Earth and space scientists. Long running (days) and highly parallel (hundreds of CPUs) jobs are common in the workload. NCCS management structures batch queues and allocates resources to optimize system use and prioritize workloads. NCCS technical staff use a locally developed discrete event simulation tool to model the impacts of evolving workloads, potential system upgrades, alternative queue structures and resource allocation policies.

  6. Design of the Bank Customer Queue Application Based on the Switch and Sound Visualization

    OpenAIRE

    Yusuf, Yuhendra; Februanda, Sudindri Rahmad

    2016-01-01

    Activities or community needs the same individuals, especially in the public interest would lead to an activity that requires a service. Limitations of service will cause the queue. This sort of thing (queue), often found at the center of public interest, such as the line at the bank, bill payments (electricity, telephone, water), and so forth. Services at the bank, for example, customers who would require the service is to be in line to wait his turn to receive services. However, it must gai...

  7. Fluid queues driven by an M/M/1/N queue

    Directory of Open Access Journals (Sweden)

    R. B. Lenin

    2000-01-01

    Full Text Available In this paper, we consider fluid queue models with infinite buffer capacity which receives and releases fluid at variable rates in such a way that the net input rate of fluid into the buffer (which is negative when fluid is flowing out of the buffer is uniquely determined by the number of customers in an M/M/1/N queue model (that is, the fluid queue is driven by this Markovian queue with constant arrival and service rates. We use some interesting identities of tridiagonal determinants to find analytically the eigenvalues of the underlying tridiagonal matrix and hence the distribution function of the buffer occupancy. For specific cases, we verify the results available in the literature.

  8. Fluid queues driven by an M / M / 1 / N queue

    Directory of Open Access Journals (Sweden)

    Lenin R. B.

    2000-01-01

    Full Text Available In this paper, we consider fluid queue models with infinite buffer capacity which receives and releases fluid at variable rates in such a way that the net input rate of fluid into the buffer (which is negative when fluid is flowing out of the buffer is uniquely determined by the number of customers in an M / M / 1 / N queue model (that is, the fluid queue is driven by this Markovian queue with constant arrival and service rates. We use some interesting identities of tridiagonal determinants to find analytically the eigenvalues of the underlying tridiagonal matrix and hence the distribution function of the buffer occupancy. For specific cases, we verify the results available in the literature.

  9. Waiting time dynamics of priority-queue networks.

    Science.gov (United States)

    Min, Byungjoon; Goh, K-I; Kim, I-M

    2009-05-01

    We study the dynamics of priority-queue networks, generalizations of the binary interacting priority-queue model introduced by Oliveira and Vazquez [Physica A 388, 187 (2009)]. We found that the original AND-type protocol for interacting tasks is not scalable for the queue networks with loops because the dynamics becomes frozen due to the priority conflicts. We then consider a scalable interaction protocol, an OR-type one, and examine the effects of the network topology and the number of queues on the waiting time distributions of the priority-queue networks, finding that they exhibit power-law tails in all cases considered, yet with model-dependent power-law exponents. We also show that the synchronicity in task executions, giving rise to priority conflicts in the priority-queue networks, is a relevant factor in the queue dynamics that can change the power-law exponent of the waiting time distribution.

  10. Two new methods for constructing double-ended priority queues from priority queues

    DEFF Research Database (Denmark)

    Elmasry, Amr; Jensen, Claus; Katajainen, Jyrki

    2008-01-01

    transformation we obtain a double-ended priority queue which guarantees the worst-case cost of O(1) for find-min, find-max , insert , extract ; and the worst-case cost of O(lg n) with at most lg n+O(1) element comparisons for delete. With the second transformation we get a meldable double-ended priority queue......We introduce two data-structural transformations to construct double-ended priority queues from priority queues. To apply our transformations the priority queues exploited must support the extraction of an unspecified element, in addition to the standard priority-queue operations. With the first...... which guarantees the worst-case cost of O(1) for find-min, find-max , insert , extract ; the worst-case cost of O(lg n) with at most lg n+O(lg lg n) element comparisons for delete; and the worst-case cost of O(min {lgm, lg n}) for meld. Here, m and n denote the number of elements stored in the data...

  11. Fluid Limits of Optimally Controlled Queueing Networks

    OpenAIRE

    Guodong Pang; Day, Martin V.

    2007-01-01

    We consider a class of queueing processes represented by a Skorokhod problem coupled with a controlled point process. Posing a discounted control problem for such processes, we show that the optimal value functions converge, in the fluid limit, to the value of an analogous deterministic control problem for fluid processes. Peer Reviewed

  12. Fluid Limits of Optimally Controlled Queueing Networks

    Directory of Open Access Journals (Sweden)

    Guodong Pang

    2007-01-01

    Full Text Available We consider a class of queueing processes represented by a Skorokhod problem coupled with a controlled point process. Posing a discounted control problem for such processes, we show that the optimal value functions converge, in the fluid limit, to the value of an analogous deterministic control problem for fluid processes.

  13. 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

  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. 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.

  16. 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

  17. Queueing networks : Rare events and fast simulations

    NARCIS (Netherlands)

    Miretskiy, D.I.

    2009-01-01

    This monograph focuses on rare events. Even though they are extremely unlikely, they can still occur and then could have significant consequences. We mainly consider rare events in queueing networks. More precisely, we are interested in the probability of collecting some large number of jobs in the

  18. A comparison of queueing, cluster and distributed computing systems

    Science.gov (United States)

    Kaplan, Joseph A.; Nelson, Michael L.

    1993-01-01

    Using workstation clusters for distributed computing has become popular with the proliferation of inexpensive, powerful workstations. Workstation clusters offer both a cost effective alternative to batch processing and an easy entry into parallel computing. However, a number of workstations on a network does not constitute a cluster. Cluster management software is necessary to harness the collective computing power. A variety of cluster management and queuing systems are compared: Distributed Queueing Systems (DQS), Condor, Load Leveler, Load Balancer, Load Sharing Facility (LSF - formerly Utopia), Distributed Job Manager (DJM), Computing in Distributed Networked Environments (CODINE), and NQS/Exec. The systems differ in their design philosophy and implementation. Based on published reports on the different systems and conversations with the system's developers and vendors, a comparison of the systems are made on the integral issues of clustered computing.

  19. 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

  20. Autonomous Hybrid Priority Queueing for Scheduling Residential Energy Demands

    Science.gov (United States)

    Kalimullah, I. Q.; Shamroukh, M.; Sahar, N.; Shetty, S.

    2017-05-01

    The advent of smart grid technologies has opened up opportunities to manage the energy consumption of the users within a residential smart grid system. Demand response management is particularly being employed to reduce the overall load on an electricity network which could in turn reduce outages and electricity costs. The objective of this paper is to develop an intelligible scheduler to optimize the energy available to a micro grid through hybrid queueing algorithm centered around the consumers’ energy demands. This is achieved by shifting certain schedulable load appliances to light load hours. Various factors such as the type of demand, grid load, consumers’ energy usage patterns and preferences are considered while formulating the logical constraints required for the algorithm. The algorithm thus obtained is then implemented in MATLAB workspace to simulate its execution by an Energy Consumption Scheduler (ECS) found within smart meters, which automatically finds the optimal energy consumption schedule tailor made to fit each consumer within the micro grid network.

  1. Single server tandem queues and queueing networks with non-correlated successive service times

    Directory of Open Access Journals (Sweden)

    Pierre Le Gall

    2001-01-01

    Full Text Available To evaluate the local actual queueing delay in general single server queueing networks with non-correlated successive service times for the same customer, we start from a recent work using the tandem queue effect, when two successive local arrivals are not separated by “premature departures”. In that case, two assumptions were made: busy periods not broken up, and there are limited variations for successive service times. These assumptions are given up after having crossed two stages. The local arrivals become indistinguishable for the sojourn time inside a given busy period. It is then proved that the local sojourn time of this tandem queue effect may be considered as the sum of two components: the first (independent of the local interarrival time corresponding to the case where upstream, successive service times are supposed to be identical to the local service time, and the second (negligible after having crossed 2 or 3 stages depending on local interarrival times increasing because of broken up busy periods. The consequence is the possible occurrence of the agglutination phenomenon of indistinguishable customers in the buffers (when there are limited “premature departures”, due to a stronger impact of long service times upon the local actual queueing delay, which is not consistent with the traditional concept of local traffic source only generating distinguishable customers.

  2. Theoretical description of metabolism using queueing theory.

    Science.gov (United States)

    Evstigneev, Vladyslav P; Holyavka, Marina G; Khrapatiy, Sergii V; Evstigneev, Maxim P

    2014-09-01

    A theoretical description of the process of metabolism has been developed on the basis of the Pachinko model (see Nicholson and Wilson in Nat Rev Drug Discov 2:668-676, 2003) and the queueing theory. The suggested approach relies on the probabilistic nature of the metabolic events and the Poisson distribution of the incoming flow of substrate molecules. The main focus of the work is an output flow of metabolites or the effectiveness of metabolism process. Two simplest models have been analyzed: short- and long-living complexes of the source molecules with a metabolizing point (Hole) without queuing. It has been concluded that the approach based on queueing theory enables a very broad range of metabolic events to be described theoretically from a single probabilistic point of view.

  3. Queueing process with excluded-volume effect.

    Science.gov (United States)

    Arita, Chikashi

    2009-11-01

    We introduce an extension of the M/M/1 queueing process with a spatial structure and excluded-volume effect. The rule of particle hopping is the same as for the totally asymmetric simple exclusion process (TASEP). A stationary-state solution is constructed in a slightly arranged matrix product form of the open TASEP. We obtain the critical line that separates the parameter space depending on whether the model has the stationary state. We calculate the average length of the model and the number of particles and show the monotonicity of the probability of the length in the stationary state. We also consider a generalization of the model with backward hopping of particles allowed and an alternate joined system of the M/M/1 queueing process and the open TASEP.

  4. Critical behavior of the exclusive queueing process

    Science.gov (United States)

    Arita, Chikashi; Schadschneider, Andreas

    2013-11-01

    The exclusive queueing process (EQP) is a generalization of the classical M/M/1 queue. It is equivalent to a totally asymmetric exclusion process (TASEP) of varying length. Here we consider two discrete-time versions of the EQP with parallel and backward-sequential update rules. The phase diagram (with respect to the arrival probability α and the service probability β) is divided into two phases corresponding to divergence and convergence of the system length. We investigate the behavior on the critical line separating these phases. For both update rules, we find diffusive behavior for small service probability (\\beta \\beta_c it becomes sub-diffusive and nonuniversal: the critical exponents characterizing the divergence of the system length and the number of customers are found to depend on the update rule. For the backward-update case, they also depend on the hopping parameter p, and remain finite when p is large, indicating a first-order transition.

  5. 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

    2016-10-14

    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.

  6. A queueing model for chronic recurrent conditions under panel observation.

    Science.gov (United States)

    Crespi, Catherine M; Cumberland, William G; Blower, Sally

    2005-03-01

    In many chronic conditions, subjects alternate between an active and an inactive state, and sojourns into the active state may involve multiple lesions, infections, or other recurrences with different times of onset and resolution. We present a biologically interpretable model of such chronic recurrent conditions based on a queueing process. The model has a birth-death process describing recurrences and a semi-Markov process describing the alternation between active and inactive states, and can be fit to panel data that provide only a binary assessment of the active or inactive state at a series of discrete time points using a hidden Markov approach. We accommodate individual heterogeneity and covariates using a random effects model, and simulate the posterior distribution of unknowns using a Markov chain Monte Carlo algorithm. Application to a clinical trial of genital herpes shows how the method can characterize the biology of the disease and estimate treatment efficacy.

  7. Fairness in the coronary angiography queue.

    Science.gov (United States)

    Alter, D A; Basinski, A S; Cohen, E A; Naylor, C D

    1999-10-05

    Since waiting lists for coronary angiography are generally managed without explicit queuing criteria, patients may not receive priority on the basis of clinical acuity. The objective of this study was to examine clinical and nonclinical determinants of the length of time patients wait for coronary angiography. In this single-centre prospective cohort study conducted in the autumn of 1997, 357 consecutive patients were followed from initial triage until a coronary angiography was performed or an adverse cardiac event occurred. The referring physicians' hospital affiliation (physicians at Sunnybrook & Women's College Health Sciences Centre, those who practice at another centre but perform angiography at Sunnybrook and those with no previous association with Sunnybrook) was used to compare processes of care. A clinical urgency rating scale was used to assign a recommended maximum waiting time (RMWT) to each patient retrospectively, but this was not used in the queuing process. RMWTs and actual waiting times for patients in the 3 referral groups were compared; the influence clinical and nonclinical variables had on the actual length of time patients waited for coronary angiography was assessed; and possible predictors of adverse events were examined. Of 357 patients referred to Sunnybrook, 22 (6.2%) experienced adverse events while in the queue. Among those who remained, 308 (91.9%) were in need of coronary angiography; 201 (60.0%) of those patients received one within the RMWT. The length of time to angiography was influenced by clinical characteristics similar to those specified on the urgency rating scale, leading to a moderate agreement between actual waiting times and RMWTs (kappa = 0.53). However, physician affiliation was a highly significant (p < 0.001) and independent predictor of waiting time. Whereas 45.6% of the variation in waiting time was explained by all clinical factors combined, 9.3% of the variation was explained by physician affiliation alone

  8. Control of Entry to a Queueing System

    Science.gov (United States)

    1979-11-01

    University of New Mexico . Zacks, S. and Yadin, M. (1970). Analytic characterization of the optimal control of a queueing system. J. Appl. Prob. 7, pp. 617...WILL. BE RH OF SYST!!¶. 29q VI~iSIO!I &A (2501)) , BE (101 ,TDOLD 50) c DIMEISION 0’P AA XW 3 5B vT FS !XNC~rtY IT MY Nf AND N ?OR VINO c TIRESE AP

  9. Schedulers with load-store queue awareness

    Science.gov (United States)

    Chen, Tong; Eichenberger, Alexandre E.; Jacob, Arpith C.; Sura, Zehra N.

    2017-01-24

    In one embodiment, a computer-implemented method includes tracking a size of a load-store queue (LSQ) during compile time of a program. The size of the LSQ is time-varying and indicates how many memory access instructions of the program are on the LSQ. The method further includes scheduling, by a computer processor, a plurality of memory access instructions of the program based on the size of the LSQ.

  10. Schedulers with load-store queue awareness

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Tong; Eichenberger, Alexandre E.; Jacob, Arpith C.; Sura, Zehra N.

    2017-02-07

    In one embodiment, a computer-implemented method includes tracking a size of a load-store queue (LSQ) during compile time of a program. The size of the LSQ is time-varying and indicates how many memory access instructions of the program are on the LSQ. The method further includes scheduling, by a computer processor, a plurality of memory access instructions of the program based on the size of the LSQ.

  11. The Average Velocity in a Queue

    Science.gov (United States)

    Frette, Vidar

    2009-01-01

    A number of cars drive along a narrow road that does not allow overtaking. Each driver has a certain maximum speed at which he or she will drive if alone on the road. As a result of slower cars ahead, many cars are forced to drive at speeds lower than their maximum ones. The average velocity in the queue offers a non-trivial example of a mean…

  12. On a bulk queueing system with impatient customers

    Directory of Open Access Journals (Sweden)

    Tadj Lotfi

    1997-01-01

    Full Text Available We consider a bulk arrival, bulk service queueing system. Customers are served in batches of r units if the queue length is not less than r . Otherwise, the server delays the service until the number of units in the queue reaches or exceeds level r . We assume that unserved customers may get impatient and leave the system. An ergodicity condition and steady-state probabilities are derived. Various system characteristics are also computed.

  13. On a bulk queueing system with impatient customers

    Directory of Open Access Journals (Sweden)

    Lotfi Tadj

    1998-01-01

    Full Text Available We consider a bulk arrival, bulk service queueing system. Customers are served in batches of r units if the queue length is not less than r. Otherwise, the server delays the service until the number of units in the queue reaches or exceeds level r. We assume that unserved customers may get impatient and leave the system. An ergodicity condition and steady-state probabilities are derived. Various system characteristics are also computed.

  14. Delay-Optimal Scheduling for Two-Hop Relay Networks with Randomly Varying Connectivity: Join the Shortest Queue-Longest Connected Queue Policy

    Directory of Open Access Journals (Sweden)

    Seung Jun Baek

    2017-01-01

    Full Text Available We consider a scheduling problem for a two-hop queueing network where the queues have randomly varying connectivity. Customers arrive at the source queue and are later routed to multiple relay queues. A relay queue can be served only if it is in connected state, and the state changes randomly over time. The source queue and relay queues are served in a time-sharing manner; that is, only one customer can be served at any instant. We propose Join the Shortest Queue-Longest Connected Queue (JSQ-LCQ policy as follows: (1 if there exist nonempty relay queues in connected state, serve the longest queue among them; (2 if there are no relay queues to serve, route a customer from the source queue to the shortest relay queue. For symmetric systems in which the connectivity has symmetric statistics across the relay queues, we show that JSQ-LCQ is strongly optimal, that is, minimizes the delay in the stochastic ordering sense. We use stochastic coupling and show that the systems under coupling exist in two distinct phases, due to dynamic interactions among source and relay queues. By careful construction of coupling in both phases, we establish the stochastic dominance in delay between JSQ-LCQ and any arbitrary policy.

  15. 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.

  16. 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....

  17. 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.

  18. IOOS Data Management Activities

    Science.gov (United States)

    2010-06-01

    customers are Harmful algal bloom forecasting, coastal inundation, hurricane intensification, and integrated ecosystem assessments. The customer projects...include methods to guard against data corruption. • Configuration management is necessary to ensure that when functions are added or changed the...with Climate and Forecast (CF) conventions [15]. For images of data, the DIF recommends the OGC Web Map Service (WMS) [16], which generates

  19. Environmental management activities

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-07-01

    The Office of Environmental Management (EM) has been delegated the responsibility for the Department of Energy`s (DOE`s) cleanup of the nuclear weapons complex. The nature and magnitude of the waste management and environmental remediation problem requires the identification of technologies and scientific expertise from domestic and foreign sources. Within the United States, operational DOE facilities, as well as the decontamination and decommissioning of inactive facilities, have produced significant amounts of radioactive, hazardous, and mixed wastes. In order to ensure worker safety and the protection of the public, DOE must: (1) assess, remediate, and monitor sites and facilities; (2) store, treat, and dispose of wastes from past and current operations; and (3) develop and implement innovative technologies for environmental restoration and waste management. The EM directive necessitates looking beyond domestic capabilities to technological solutions found outside US borders. Following the collapse of the Soviet regime, formerly restricted elite Soviet scientific expertise became available to the West. EM has established a cooperative technology development program with Russian scientific institutes that meets domestic cleanup objectives by: (1) identifying and accessing Russian EM-related technologies, thereby leveraging investments and providing cost-savings; (2) improving access to technical information, scientific expertise, and technologies applicable to EM needs; and (3) increasing US private sector opportunities in Russian in EM-related areas.

  20. A tandem queue with Lévy input: a new representation of the downstream queue length.

    NARCIS (Netherlands)

    Dębicki, K.; Mandjes, M.; van Uitert, M.

    2007-01-01

    In this article we present a new representation for the steady-state distribution of the workload of the second queue in a two-node tandem network. It involves the difference of two suprema over two adjacent intervals. In the case of spectrally positive Lévy input, this enables us to derive the

  1. 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

  2. Mathematical Analysis of Queue with Phase Service: An Overview

    National Research Council Canada - National Science Library

    Sharma, Richa

    2014-01-01

    ... is to provide an overview on the conceptual aspects for the phase service queueing models in different frameworks. In traditional queueing models, all arriving customers/jobs require main service which is to be completed in single phase. In many real time systems the service may be completed in many phases. The concept of optional phase services has b...

  3. Generalized processor sharing queues with heterogeneous traffic classes

    NARCIS (Netherlands)

    Borst, Sem; Mandjes, M.R.H.; van Uitert, Miranda

    2003-01-01

    We consider a queue fed by a mixture of light-tailed and heavy-tailed traffic. The two traffic flows 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

  4. Batch arrival discrete time queue with gated vacation system ...

    African Journals Online (AJOL)

    A class of single server vacation queues, which have batch arrivals and single server, is considered in discrete time. Here the server goes on vacation of random length as soon as the system becomes empty. On return from vacation, if he finds any customers waiting in the queue, the server starts serving the customers one ...

  5. 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.

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

    NARCIS (Netherlands)

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

  7. 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

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

    NARCIS (Netherlands)

    N.D. van Foreest; M.R.H. Mandjes (Michel); J.C.W. van Ommeren; W.R.W. Scheinhardt (Werner)

    2005-01-01

    textabstractWe 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

  9. Environmental Management vitrification activities

    Energy Technology Data Exchange (ETDEWEB)

    Krumrine, P.H. [Waste Policy Institute, Gaithersburg, MD (United States)

    1996-05-01

    Both the Mixed Waste and Landfill Stabilization Focus Areas as part of the Office of Technology Development efforts within the Department of Energy`s (DOE) Environmental Management (EM) Division have been developing various vitrification technologies as a treatment approach for the large quantities of transuranic (TRU), TRU mixed and Mixed Low Level Wastes that are stored in either landfills or above ground storage facilities. The technologies being developed include joule heated, plasma torch, plasma arc, induction, microwave, combustion, molten metal, and in situ methods. There are related efforts going into development glass, ceramic, and slag waste form windows of opportunity for the diverse quantities of heterogeneous wastes needing treatment. These studies look at both processing parameters, and long term performance parameters as a function of composition to assure that developed technologies have the right chemistry for success.

  10. 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 and id...... and statistical tests, including a simple bootstrap two-sample test for comparing patience distributions. A small simulation study and a real data example are presented....

  11. Queues with Dropping Functions and General Arrival Processes.

    Science.gov (United States)

    Chydzinski, Andrzej; Mrozowski, Pawel

    2016-01-01

    In a queueing system with the dropping function the arriving customer can be denied service (dropped) with the probability that is a function of the queue length at the time of arrival of this customer. The potential applicability of such mechanism is very wide due to the fact that by choosing the shape of this function one can easily manipulate several performance characteristics of the queueing system. In this paper we carry out analysis of the queueing system with the dropping function and a very general model of arrival process--the model which includes batch arrivals and the interarrival time autocorrelation, and allows for fitting the actual shape of the interarrival time distribution and its moments. For such a system we obtain formulas for the distribution of the queue length and the overall customer loss ratio. The analytical results are accompanied with numerical examples computed for several dropping functions.

  12. Queueing phase transition: theory of translation.

    Science.gov (United States)

    Romano, M Carmen; Thiel, Marco; Stansfield, Ian; Grebogi, Celso

    2009-05-15

    We study the current of particles on a lattice, where to each site a different hopping probability has been associated and the particles can move only in one direction. We show that the queueing of the particles behind a slow site can lead to a first-order phase transition, and derive analytical expressions for the configuration of slow sites for this to happen. We apply this stochastic model to describe the translation of mRNAs. We show that the first-order phase transition, uncovered in this work, is the process responsible for the classification of the proteins having different biological functions.

  13. Funnel Heap - A Cache Oblivious Priority Queue

    DEFF Research Database (Denmark)

    Brodal, Gerth Stølting; Fagerberg, Rolf

    2002-01-01

    model. Arge et al. recently presented the first optimal cache oblivious priority queue, and demonstrated the importance of this result by providing the first cache oblivious algorithms for graph problems. Their structure uses cache oblivious sorting and selection as subroutines. In this paper, we devise......The cache oblivious model of computation is a two-level memory model with the assumption that the parameters of the model are unknown to the algorithms. A consequence of this assumption is that an algorithm efficient in the cache oblivious model is automatically efficient in a multi-level memory...

  14. 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

  15. Waiting time in a queueing network with a single shared server

    NARCIS (Netherlands)

    Boon, M.A.A.; van der Mei, R.D.; Winands, E.M.M.

    2013-01-01

    We study a queueing network with a single shared server that serves the queues in a cyclic order. External customers arrive at the queues according to independent Poisson processes. After completing service, a customer either leaves the system or is routed to another queue. This model is very

  16. Dynamical analysis of the exclusive queueing process.

    Science.gov (United States)

    Arita, Chikashi; Schadschneider, Andreas

    2011-05-01

    Recently, the stationary state of a parallel-update totally asymmetric simple exclusion process with varying system length, which can be regarded as a queueing process with excluded-volume effect (exclusive queueing process), was obtained [C Arita and D Yanagisawa, J. Stat. Phys. 141, 829 (2010)]. In this paper, we analyze the dynamical properties of the number of particles [N(t)] and the position of the last particle (the system length) [L(t)], using an analytical method (generating function technique) as well as a phenomenological description based on domain-wall dynamics and Monte Carlo simulations. The system exhibits two phases corresponding to linear convergence or divergence of [N(t)] and [L(t)]. These phases can both further be subdivided into high-density and maximal-current subphases. The predictions of the domain-wall theory are found to be in very good agreement quantitively with results from Monte Carlo simulations in the convergent phase. On the other hand, in the divergent phase, only the prediction for [N(t)] agrees with simulations.

  17. Retrial queues with recurrent demand option

    Directory of Open Access Journals (Sweden)

    K. Farahmand

    1996-01-01

    Full Text Available The object of this paper is to analyze the model of a queueing system in which customers can call in only to request service: if the server is free, the customer enters service immediately. Otherwise, if the service system is occupied, the customer joins a source of unsatisfied customers called the orbit. On completion of each service the recipient of service has an option of leaving the system completely with probability 1−p or returning to the orbit with probability p. We consider two models characterized by the discipline governing the order of rerequests for service from the orbit. First, all the customers from the orbit apply at a fixed rate. Secondly, customers from the orbit are discouraged and reduce their rate of demand as more customers join the orbit. The arrival at and the demands from the orbit are both assumed to be according to the Poisson process. However, the service times for both primary customers and customers from the orbit are assumed to have a general distribution. We calculate several characteristic quantities of these queueing systems.

  18. Queue-length synchronization in communication networks.

    Science.gov (United States)

    Mukherjee, Satyam; Gupte, Neelima

    2009-05-01

    We study the synchronization in the context of network traffic on a 2-d communication network with local clustering and geographic separations. The network consists of nodes and randomly distributed hubs where the top five hubs ranked according to their coefficient of betweenness centrality (CBC) are connected by random assortative and gradient mechanisms. For multiple message traffic, messages can trap at the high CBC hubs, and congestion can build up on the network with long queues at the congested hubs. The queue lengths are seen to synchronize in the congested phase. Both complete and phase synchronization are seen, between pairs of hubs. In the decongested phase, the pairs start clearing and synchronization is lost. A cascading master-slave relation is seen between the hubs, with the slower hubs (which are slow to decongest) driving the faster ones. These are usually the hubs of high CBC. Similar results are seen for traffic of constant density. Total synchronization between the hubs of high CBC is also seen in the congested regime. Similar behavior is seen for traffic on a network constructed using the Waxman random topology generator. We also demonstrate the existence of phase synchronization in real internet traffic data.

  19. Dynamic Capacity Allocation Algorithms for iNET Link Manager

    Science.gov (United States)

    2014-05-01

    Simulation, Training and Instrumentation (PEO STRI ), Contract No. W900KK-09-C-0021. The Executing Agent and Program Manager work out of the AFTC. 412 TW...certain details such as: • Timing of queue draining based on LM commands, • Interplay between MAC and Traffic Engineering (TE) queues at the IP layer...implement iNET Traffic Engineering (TE) Queues, the testbed shown in Figure 3 enhances the Hierarchical Token Bucket (HTB) queue provided in Linux

  20. 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.

  1. DIRAC pilot framework and the DIRAC Workload Management System

    Science.gov (United States)

    Casajus, Adrian; Graciani, Ricardo; Paterson, Stuart; Tsaregorodtsev, Andrei; LHCb DIRAC Team

    2010-04-01

    DIRAC, the LHCb community Grid solution, has pioneered the use of pilot jobs in the Grid. Pilot Jobs provide a homogeneous interface to an heterogeneous set of computing resources. At the same time, Pilot Jobs allow to delay the scheduling decision to the last moment, thus taking into account the precise running conditions at the resource and last moment requests to the system. The DIRAC Workload Management System provides one single scheduling mechanism for jobs with very different profiles. To achieve an overall optimisation, it organizes pending jobs in task queues, both for individual users and production activities. Task queues are created with jobs having similar requirements. Following the VO policy a priority is assigned to each task queue. Pilot submission and subsequent job matching are based on these priorities following a statistical approach.

  2. 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.

  3. Probability, statistics and queueing theory, with computer science applications

    CERN Document Server

    Allen, Arnold O

    1978-01-01

    Probability, Statistics, and Queueing Theory: With Computer Science Applications focuses on the use of statistics and queueing theory for the design and analysis of data communication systems, emphasizing how the theorems and theory can be used to solve practical computer science problems. This book is divided into three parts. The first part discusses the basic concept of probability, probability distributions commonly used in applied probability, and important concept of a stochastic process. Part II covers the discipline of queueing theory, while Part III deals with statistical inference. T

  4. 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.

  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...... 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...... derive steady-state waiting-time distributions for both models. The results are illustrated with numerical examples....

  6. 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.

  7. A Report on Stochastic Fairness Queueing (SFQ) Experiments

    Science.gov (United States)

    Denny, Barbara A.

    1993-01-01

    SRI International (SRI) has developed an improved queueing algorithm, known as Stochastic Fairness Queueing (SFQ), for best-effort traffic (i.e., traffic that does not require any guaranteed service). SFQ is a probablistic variant of strict fair queueing where instead of a single queue being allocated per flow, a fixed number of queues are used and a hash function maps the IP source and destination to a particular queue. A seed to the hash function is also perturbed occasionally to help distribute the flows amongst different queues when more than one flow maps to the same queue during the lifetime of the flow. SFQ provides 'fair' access by trying to ensure that each flow from source to destination host obtains equal access to the available bandwidth. This report covers a series of experiments performed on DARTnet evaluating the behavior and performance of SFQ against a FIFO queueing discipline. These experiments were designed to show SFQ's advantages and performance, and include tests demonstrating: Fair utilization of available resources; Starvation prevention; Graceful degradation under overload conditions; and Resource usage. In general, the experiments do show that SFQ is better than FIFO queueing at allocating bandwidth equally among a set of flows. SFQ also prevents a stream from dominating the available bandwidth, which seems to be a tendency with FIFO queueing (i.e., if a flow demands more than its share of the available bandwidth, with FIFO queueing that stream receives a disproportionate amount when compared to flows demanding less than their share). Furthermore, SFQ seems to reward 'nice' users of the network by providing a lower variance in delay and more throughput when their resource demand is less than their available share. Both SFQ and FIFO queueing seem to degrade fairly well as the network becomes saturated and to recover well as the network becomes less congested. Not unexpectedly, FIFO queueing is a little more efficient than SFQ-the delays are

  8. Simple queueing approach to segregation dynamics in Schelling model

    OpenAIRE

    Sobkowicz, Pawel

    2007-01-01

    A simple queueing approach for segregation of agents in modified one dimensional Schelling segregation model is presented. The goal is to arrive at simple formula for the number of unhappy agents remaining after the segregation.

  9. 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.

  10. A unifying property for distribution-sensitive priority queues

    DEFF Research Database (Denmark)

    Elmasry, Amr Ahmed Abd Elmoneim; Farzan, Arash; Iacono, John

    2011-01-01

    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......, 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...

  11. Adaptive circular queue image steganography with RSA cryptosystem

    Directory of Open Access Journals (Sweden)

    Mamta Jain

    2016-09-01

    Full Text Available The major objective of the article is to supply the novel and efficient methodology of digital image steganography that describes individuality regarding secret transmission using the adaptive circular queue least significant bits (LSBs substitution. The data structure queue is employed dynamically in resource distribution between multiple communication recipients and once secret information transmitted asynchronously. Here, RSA cryptosystem is employed for secret information confidentiality and authentication. The result of the cryptosystem organised into various blocks. In steganography method, organise the cover image into various circular queues blocks. Dynamically adapted procedure is employed to assign secret cypher blocks to circular queues for embedding. Authorised receiver will determine the right plain text using private key in RSA decypherment. Performance analysis is evaluated by using MSE, PSNR and maximum embedding capacity. Results are higher as compared with several of existing algorithms of image steganography.

  12. 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...

  13. 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.

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

    Science.gov (United States)

    van Eeden, Karin; Moeke, Dennis; Bekker, René

    2016-09-01

    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 for the daily care of the residents and account for a significant proportion of the total labor expenses. In practice, the lack of reliable data makes it difficult for nursing home managers to make informed staffing decisions. The focus of this study lies on the 'care on demand' process in a Belgian nursing home. Based on the analysis of real-life 'call button' data, a queueing model is presented which can be used by nursing home managers to determine the number of care workers required to meet a specific service level. Based on numerical experiments an 80/10 service level is proposed for this nursing home, meaning that at least 80 percent of the clients should receive care within 10 minutes after a call button request. To the best of our knowledge, this is the first attempt to develop a quantitative model for the 'care on demand' process in a nursing home.

  15. MQCC: Maximum Queue Congestion Control for Multipath Networks with Blockage

    Science.gov (United States)

    2015-10-19

    Design, Implementation and Evaluation of Congestion Control for Multipath TCP ,” in Proc. of USENIX Conference on Networked Systems Design and...MQCC: Maximum Queue Congestion Control for Multipath Networks with Blockage Scott Pudlewski, Brooke Shrader, Laura Herrera, Nathaniel M. Jones...queue-based (MQCC) congestion control algorithm. MQCC uses average buffer occupancy as a measure of the congestion in a network (as opposed to packet

  16. Asymptotic analysis of Lévy-driven tandem queues

    NARCIS (Netherlands)

    P.M.D. Lieshout (Pascal); M.R.H. Mandjes (Michel)

    2008-01-01

    htmlabstractWe analyze tail asymptotics of a two-node tandem queue with spectrally-positive Lévy input. A first focus lies in the tail probabilities of the type ¿(Q 1>¿ x,Q 2>(1¿¿)x), for ¿¿(0,1) and x large, and Q i denoting the steady-state workload in the ith queue. In case of light-tailed input,

  17. Computing Fuzzy Queueing Performance Measures by L-R Method

    Directory of Open Access Journals (Sweden)

    J.P. Mukeba Kanyinda

    2015-04-01

    Full Text Available This article shows that the {\\it L-R method} introduced in this work is one of valid methods for computing performance measures of fuzzy queues. Using this calculation technique, we find the number of customers and the waiting time of a simple queue M/M/1 in fuzzy environment. L-R method has the advantage of being short, convenient and flexible compared to the well-known and called alpha-cuts method.

  18. 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.

  19. Ethics in radiology: wait lists queue jumping.

    Science.gov (United States)

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

    2013-08-01

    Education in ethics is a requirement for all Royal College residency training programs as laid out in the General Standards of Accreditation for residency programs in Canada. The ethical challenges that face radiologists in clinical practice are often different from those that face other physicians, because the nature of the physician-patient interaction is unlike that of many other specialties. Ethics education for radiologists and radiology residents will benefit from the development of teaching materials and resources that focus on the issues that are specific to the specialty. This article is intended to serve as an educational resource for radiology training programs to facilitate teaching ethics to residents and also as a continuing medical education resource for practicing radiologists. In an environment of limited health care resources, radiologists are frequently asked to expedite imaging studies for patients and, in some respects, act as gatekeepers for specialty care. The issues of wait lists, queue jumping, and balancing the needs of individuals and society are explored from the perspective of a radiologist. Copyright © 2013 Canadian Association of Radiologists. Published by Elsevier Inc. All rights reserved.

  20. The Curse of the First-in-first-out Queue Discipline

    DEFF Research Database (Denmark)

    Platz, Trine Tornøe; Østerdal, Lars Peter

    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 ......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....

  1. 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.

  2. An expected coverage model with a cutoff priority queue.

    Science.gov (United States)

    Yoon, Soovin; Albert, Laura A

    2017-07-19

    Emergency medical services provide immediate care to patients with various types of needs. When the system is congested, the response to urgent emergency calls can be delayed. To address this issue, we propose a spatial Hypercube approximation model with a cutoff priority queue that estimates performance measures for a system where some servers are reserved exclusively for high priority calls when the system is congested. In the cutoff priority queue, low priority calls are not immediately served-they are either lost or entered into a queue-whenever the number of busy ambulances is equal to or greater than the cutoff. The spatial Hypercube approximation model can be used to evaluate the design of public safety systems that employ a cutoff priority queue. A mixed integer linear programming model uses the Hypercube model to identify deployment and dispatch decisions in a cutoff priority queue paradigm. Our computational study suggests that the improvement in the expected coverage is significant when the cutoff is imposed, and it elucidates the tradeoff between the coverage improvement and the cost to low-priority calls that are "lost" when using a cutoff. Finally, we present a method for selecting the cutoff value for a system based on the relative importance of low-priority calls to high-priority calls.

  3. Properties of Multi-Stage M/G/1/K Queues with Series Arrangement

    Directory of Open Access Journals (Sweden)

    Hernández-González Salvador

    2015-07-01

    Full Text Available We propose a modification to the Buzacott & Shantikumar (1993 method to evaluate the properties of M/G/1/K queues with series arrangement. We made several tests and compared with simulation to validate the results. We observed that, with the proposed modification, the method has an acceptable level of exactitude. It can be considered an alternative calculation to other methods in the literature. The fact that this method requires less computational effort, can be useful to practitioners and managers that require tools to analyze the performance of systems in production and services areas.

  4. The single server queue and the storage model: Large deviations and fixed points

    Directory of Open Access Journals (Sweden)

    2006-01-01

    Full Text Available We consider the coupling of a single server queue and a storage model defined as a queue/store model. We establish that if the input variables, arrivals at the queue and store, satisfy large deviations principles and are linked through an exponential tilting, then the output variables (departures from each system satisfy large deviations principles with the same rate function.

  5. 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

  6. A microscopic investigation into the capacity drop : Impacts of longitudinal behavior on the queue discharge rate

    NARCIS (Netherlands)

    Yuan, K.; Knoop, V.L.; Hoogendoorn, S.P.

    2017-01-01

    The capacity drop indicates that the queue discharge rate is lower than the free-flow capacity. Studies show that the queue discharge rate varies under different traffic conditions. Empirical data show that the queue discharge rate increases as the speed in congestion increases. Insights into the

  7. 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.

  8. 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.

  9. Analysis of an M/{Dn}/1 retrial queue

    Science.gov (United States)

    Wu, Xiaoyong; Ke, Xiaowu

    2007-03-01

    We consider a single server retrial queueing system in which each customer (primary or retrial customer) has discrete service times taking on value Dj with probability , and . An arriving primary customer who finds the server busy tries later. Moreover, each retrial customer has its own orbit, and the retrial customers try to enter the service independently of each other. We call this retrial queue an M/{Dn}/1 retrial queue. A necessary and sufficient condition for this system stability is given. In the steady state, we derive the joint distribution of the state of the server and the number of customers in the retrial orbits. The explicit expressions of some performance measures are given. In addition, the steady-state distribution of the waiting time is discussed.

  10. Bulk input queues with quorum and multiple vacations

    Directory of Open Access Journals (Sweden)

    Jewgeni H. Dshalalow

    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.

  11. 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 ...

  12. Queueing models of potentially lethal damage repair in irradiated cells.

    Science.gov (United States)

    Myasnikova, E M; Rachev, S T; Yakovlev, A Y

    1996-07-01

    Some of the ideas arising in queueing theory are applied to describe the repair mechanisms responsible for recovery of cells from potentially lethal radiation damage. Two alternative versions are presented of a queueing model of damage repair after a single dose of irradiation. The first version represents a linear misrepair model, and the second invokes the idea of spontaneous lesion fixation. They are pieced together in the third model, allowing for both mechanisms. The consistency of the proposed models with published experimental data is tested.

  13. 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...... element. Our data structure is the first to support multi-insertion and multi-decrease key in constant time. The priority queue can be implemented on the EREW PRAM and can perform any sequence ofnoperations inO(n) time andO(mlogn) work,mbeing the total number of keyes inserted and/or updated. A main...

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

    Directory of Open Access Journals (Sweden)

    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

  15. 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.

  16. 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.

  17. Exact overflow asymptotics for queues with many Gaussian inputs

    NARCIS (Netherlands)

    K.G. Debicki; M.R.H. Mandjes (Michel)

    2002-01-01

    textabstractIn this paper we consider a queue fed by a large number $n$ of independent continuous-time Gaussian processes with stationary increments. After scaling the buffer exceedance threshold $B$ and the (constant) service capacity $C$ by the number of sources (i.e., $Bequiv nb$ and $Cequiv

  18. Exact overflow asymptotics for queues with many Gaussian inputs

    NARCIS (Netherlands)

    Debicki, Krzysztof; Mandjes, M.R.H.

    2003-01-01

    In this paper we consider a queue fed by a large number of independent continuous-time Gaussian processes with stationary increments. After scaling the buffer exceedance threshold and the (constant) service capacity by the number of sources, we present asymptotically exact results for the

  19. Performance Measures of a Fuzzy Product Form Queueing Network

    Directory of Open Access Journals (Sweden)

    J. P. Mukeba Kanyinda

    2015-04-01

    Full Text Available This paper introduces the performance measures computation of a product form queueing network with fuzzy parameters. In this first study, we focus our objective to find the customers number and the customer sojourn time in the system at the stationary state. Values of these characteristics are provided. A didactical example is used to illustrate the process.

  20. Control approach to Queue Theory | Omolehin | Journal of the ...

    African Journals Online (AJOL)

    The rigid condition for simple queue problem is minimized by considering multiple channels through control approach. The result control problem is solved using Conventional Conjugate Gradient Method and the optimal system performance is obtained. Journal of the Nigerian Association of Mathematical Physics Vol.

  1. Arrival first queueing networks with applications in kanban production systems

    NARCIS (Netherlands)

    Boucherie, Richardus 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

  2. Transient error approximation in a Lévy queue

    NARCIS (Netherlands)

    B. Mathijsen (Britt); A.P. Zwart (Bert)

    2017-01-01

    textabstractMotivated 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

  3. Limit distributions for queues and random rooted trees

    Directory of Open Access Journals (Sweden)

    Lajos Takács

    1993-01-01

    Full Text Available In this paper several limit theorems are proved for the fluctuations of the queue size during the initial busy period of a queuing process with one server. These theorems are used to find the solutions of various problems connected with the heights and widths of random rooted trees.

  4. 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.

  5. 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...

  6. Large Deviations without Principle: Join the Shortest Queue

    NARCIS (Netherlands)

    Ridder, Ad; Shwartz, Adam

    2004-01-01

    We develop a methodology for studying "large deviations type" questions. Our approach does not require that the large deviations principle holds, and is thus applicable to a larg class of systems. We study a system of queues with exponential servers, which share an arrival stream. Arrivals are

  7. Large deviations without principle: join the shortest queue

    NARCIS (Netherlands)

    Ridder, A.A.N.; Shwartz, A.

    2005-01-01

    We develop a methodology for studying "large deviations type" questions. Our approach does not require that the large deviations principle holds, and is thus applicable to a large class of systems. We study a system of queues with exponential servers, which share an arrival stream. Arrivals are

  8. Efficient estimation of overflow probabilities in queues with breakdowns

    NARCIS (Netherlands)

    Kroese, Dirk; Nicola, V.F.

    1999-01-01

    Efficient importance sampling methods are proposed for the simulation of a single server queue with server breakdowns. The server is assumed to alternate between the operational and failure states according to a continuous time Markov chain. Both, continuous (fluid flow) and discrete (single

  9. Strategic behavior and social outcomes in a bottleneck queue

    DEFF Research Database (Denmark)

    Breinbjerg, Jesper Breinbjerg; Sebald, Alexander Christopher; Østerdal, Lars Peter

    2016-01-01

    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...

  10. Queueing and Service Patterns in a University Teaching Hospital FO

    African Journals Online (AJOL)

    acer

    INTRODUCTION. In real life, waiting for service is a common phenomenon. We wait for service in bars and restaurants; we queue up for service in the banks, schools, supermarkets, filling stations, post offices ... Queuing theory is part of the mathematical theory of the ... as the service distribution, the probability distribution of ...

  11. Overflow behavoir in queues with many long-tailed inputs

    NARCIS (Netherlands)

    M.R.H. Mandjes (Michel); S.C. Borst (Sem)

    1999-01-01

    textabstractWe consider a fluid queue fed by a superposition of $n$ homogeneous on-off sources with generally distributed on- and off-periods. We scale buffer space $B$ and link rate $C$ by $n$, such that we get $nb$ and $nc$, respectively. Then we let $n$ grow large. In this regime, the overflow

  12. 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 ... Author Affiliations. R K Shyamasundar1. Computer Science Group, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400 005, India ...

  13. 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...

  14. Predicting clinical image delivery time by monitoring PACS queue behavior.

    Science.gov (United States)

    King, Nelson E; Documet, Jorge; Liu, Brent

    2006-01-01

    The expectation of rapid image retrieval from PACS users contributes to increased information technology (IT) infrastructure investments to increase performance as well as continuing demands upon PACS administrators to respond to "slow" system performance. The ability to provide predicted delivery times to a PACS user may curb user expectations for "fastest" response especially during peak hours. This, in turn, could result in a PACS infrastructure tailored to more realistic performance demands. A PACS with a stand-alone architecture under peak load typically holds study requests in a queue until the DICOM C-Move command can take place. We investigate the contents of a stand-alone architecture PACS RetrieveSend queue and identified parameters and behaviors that enable a more accurate prediction of delivery time. A prediction algorithm for studies delayed in a stand-alone PACS queue can be extendible to other potential bottlenecks such as long-term storage archives. Implications of a queue monitor in other PACS architectures are also discussed.

  15. 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.

  16. Job Queues, Certification Status, and the Education Labor Market

    Science.gov (United States)

    Evans, Lorraine

    2011-01-01

    This research explores the interaction between training programs and certification status in one education labor market to examine the micro-level interactions that shape the recruitment process. Using job queue theory, it is found that the information available to novice teachers operates to stratify and shape their worksite choices in addition…

  17. Reduced-load equivalence for queues with Gaussian input

    NARCIS (Netherlands)

    A.B. Dieker (Ton)

    2004-01-01

    textabstractIn this note, we consider a queue fed by a number of independent heterogeneous Gaussian sources. We study under what conditions a reduced load equivalence holds, i.e., when a subset of the sources becomes asymptotically dominant as the buffer size increases. For this, recent results on

  18. On a single-server queue with fixed accumulation level, state dependent service, and semi-Markov modulated input flow

    Directory of Open Access Journals (Sweden)

    Jewgeni H. Dshalalow

    1992-01-01

    Full Text Available The authors study the queueing process in a single-server queueing system with state dependent service and with the input modulated by a semi-Markov process embedded in the queueing process. It is also assumed that the server capacity is r≥1 and that any service act will not begin until the queue accumulates at least r units. In this model, therefore, idle periods also depend upon the queue length.

  19. Active Risk Management and Banking Stability

    NARCIS (Netherlands)

    Silva Buston, C.F.

    2013-01-01

    Abstract: This paper analyzes the net impact of two opposing effects of active risk management at banks on their stability: higher risk-taking incentives and better isolation of credit supply from varying economic conditions. We present a model where banks actively manage their portfolio risk by

  20. Intercultural Management and Managerial Activities

    National Research Council Canada - National Science Library

    Nový, Ivan

    2007-01-01

    .... Research findings from Misumi, Sinha and Ohio school are emphasized. Influences are analyzed on the levels of leading, goal setting, decision making, problem solving, motivating and intercultural competences of managers...

  1. 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.

  2. A Note on Bayesian Estimation of the Traffic Intensity in M/M/1 Queue and Queue Characteristics under Quadratic Loss Function

    Directory of Open Access Journals (Sweden)

    Sanku Dey

    2009-01-01

    Full Text Available Bayes' estimators of the traffic intensity r and various queue characteristics in an M/M/1 queue have been derived under the assumptions of different priors for r and the quadratic error loss function (QELF. Finally, a numerical example is given to illustrate the results

  3. Organizational Actively Management for Opportunity Hunting

    Directory of Open Access Journals (Sweden)

    Nasser Fegh-hi FARAHMAND

    2012-03-01

    Full Text Available Organizational Actively Management (OAM is the responsibility of every manager. Because, an approach for OAM is becoming more widely accepted is a community-based development approach. In Opportunity Hunting Approach (OHA, OAM is the responsibility of every manager for his/her actions. OAM is using from top to bottom development model. According to the survey of market and customers, after understand customers’ needs, organization then decide how the quality policy and target will develop, from there the actively management system can be developed. The aim of this study in field of organizational actively management and policy of it can provide the specific process required for setting up and monitoring the actively target. As it also is customer-oriented, it aims to improve customer satisfaction. In addition, the actively target should be set up and implemented within every organization department and at each level, in accordance with actively policy. Furthermore, organization should develop the actively management system, in order to conform to general requirements and actively target.

  4. Generalized priority-queue network dynamics: impact of team and hierarchy.

    Science.gov (United States)

    Cho, Won-kuk; Min, Byungjoon; Goh, K-I; Kim, I-M

    2010-06-01

    We study the effect of team and hierarchy on the waiting-time dynamics of priority-queue networks. To this end, we introduce generalized priority-queue network models incorporating interaction rules based on team-execution and hierarchy in decision making, respectively. It is numerically found that the waiting-time distribution exhibits a power law for long waiting times in both cases, yet with different exponents depending on the team size and the position of queue nodes in the hierarchy, respectively. The observed power-law behaviors have in many cases a corresponding single or pairwise-interacting queue dynamics, suggesting that the pairwise interaction may constitute a major dynamic consequence in the priority-queue networks. It is also found that the reciprocity of influence is a relevant factor for the priority-queue network dynamics.

  5. 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.

  6. Transient Analysis of Hysteresis Queueing Model Using Matrix Geometric Method

    Directory of Open Access Journals (Sweden)

    Wajiha Shah

    2011-10-01

    Full Text Available Various analytical methods have been proposed for the transient analysis of a queueing system in the scalar domain. In this paper, a vector domain based transient analysis is proposed for the hysteresis queueing system with internal thresholds for the efficient and numerically stable analysis. In this system arrival rate of customer is controlled through the internal thresholds and the system is analyzed as a quasi-birth and death process through matrix geometric method with the combination of vector form Runge-Kutta numerical procedure which utilizes the special matrices. An arrival and service process of the system follows a Markovian distribution. We analyze the mean number of customers in the system when the system is in transient state against varying time for a Markovian distribution. The results show that the effect of oscillation/hysteresis depends on the difference between the two internal threshold values.

  7. ARQ with sequential decoding of packetized data - Queueing analysis

    Science.gov (United States)

    Shacham, N.

    1984-10-01

    The operation of a sequential decoder in a packet-switching environment is considered. Packets arrive randomly at the decoder, and a packet is stored in a buffer if the decoder is busy upon its arrival. The decoder devotes no more than a time-out period of predetermined length to the decoding of any single packet. If packet decoding is completed within that period, the packet leaves the system. Otherwise, it is retransmitted and its decoding starts anew. While a packet is retransmitted, the decoder decodes another packet that resides in its buffer. An upper bound on the maximum rate of packets that can be supported by the channel-decoder combination is derived, and the optimum time-out that maximizes that rate is determined. A discrete-time model of the decoder's queue is presented, and the average queue length and throughput are evaluated.

  8. Algorithm for queueing networks with multi-rate traffic

    DEFF Research Database (Denmark)

    Iversen, Villy Bæk; Ko, King-Tim

    2011-01-01

    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...... is reversibility which implies that the arrival process and departure process are identical processes, for example state-dependent Poisson processes. This property is equivalent to reversibility. Due to product form, an open network with multi-rate traffic is easy to evaluate by convolution algorithms because...... 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...

  9. 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...

  10. Queueing induced by bidirectional motor motion near the end of a microtubule.

    Science.gov (United States)

    Ashwin, Peter; Lin, Congping; Steinberg, Gero

    2010-11-01

    Recent live observations of motors in long-range microtubule (MT) dependent transport in the fungus Ustilago maydis have reported bidirectional motion of dynein and an accumulation of the motors at the polymerization-active (the plus-end) of the microtubule. Quantitative data derived from in vivo observation of dynein has enabled us to develop an accurate, quantitatively-valid asymmetric simple exclusion process (ASEP) model that describes the coordinated motion of anterograde and retrograde motors sharing a single oriented microtubule. We give approximate expressions for the size and distribution of the accumulation, and discuss queueing properties for motors entering this accumulation. We show for this ASEP model, that the mean accumulation can be modeled as an M/M/∞ queue that is Poisson distributed with mean F(arr)/p(d), where F(arr) is the flux of motors that arrives at the tip and p(d) is the rate at which individual motors change direction from anterograde to retrograde motion. Deviations from this can in principle be used to gain information about other processes at work in the accumulation. Furthermore, our work is a significant step toward a mathematical description of the complex interactions of motors in cellular long-range transport of organelles.

  11. Queueing induced by bidirectional motor motion near the end of a microtubule

    Science.gov (United States)

    Ashwin, Peter; Lin, Congping; Steinberg, Gero

    2010-11-01

    Recent live observations of motors in long-range microtubule (MT) dependent transport in the fungus Ustilago maydis have reported bidirectional motion of dynein and an accumulation of the motors at the polymerization-active (the plus-end) of the microtubule. Quantitative data derived from in vivo observation of dynein has enabled us to develop an accurate, quantitatively-valid asymmetric simple exclusion process (ASEP) model that describes the coordinated motion of anterograde and retrograde motors sharing a single oriented microtubule. We give approximate expressions for the size and distribution of the accumulation, and discuss queueing properties for motors entering this accumulation. We show for this ASEP model, that the mean accumulation can be modeled as an M/M/∞ queue that is Poisson distributed with mean Farr/pd , where Farr is the flux of motors that arrives at the tip and pd is the rate at which individual motors change direction from anterograde to retrograde motion. Deviations from this can in principle be used to gain information about other processes at work in the accumulation. Furthermore, our work is a significant step toward a mathematical description of the complex interactions of motors in cellular long-range transport of organelles.

  12. 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

  13. Diagonal queue medical image steganography with Rabin cryptosystem.

    Science.gov (United States)

    Jain, Mamta; Lenka, Saroj Kumar

    2016-03-01

    The main purpose of this work is to provide a novel and efficient method to the image steganography area of research in the field of biomedical, so that the security can be given to the very precious and confidential sensitive data of the patient and at the same time with the implication of the highly reliable algorithms will explode the high security to the precious brain information from the intruders. The patient information such as patient medical records with personal identification information of patients can be stored in both storage and transmission. This paper describes a novel methodology for hiding medical records like HIV reports, baby girl fetus, and patient's identity information inside their Brain disease medical image files viz. scan image or MRI image using the notion of obscurity with respect to a diagonal queue least significant bit substitution. Data structure queue plays a dynamic role in resource sharing between multiple communication parties and when secret medical data are transferred asynchronously (secret medical data not necessarily received at the same rate they were sent). Rabin cryptosystem is used for secret medical data writing, since it is computationally secure against a chosen-plaintext attack and shows the difficulty of integer factoring. The outcome of the cryptosystem is organized in various blocks and equally distributed sub-blocks. In steganography process, various Brain disease cover images are organized into various blocks of diagonal queues. The secret cipher blocks and sub-blocks are assigned dynamically to selected diagonal queues for embedding. The receiver gets four values of medical data plaintext corresponding to one ciphertext, so only authorized receiver can identify the correct medical data. Performance analysis was conducted using MSE, PSNR, maximum embedding capacity as well as by histogram analysis between various Brain disease stego and cover images.

  14. Queue position in the endoscopic schedule impacts effectiveness of colonoscopy.

    Science.gov (United States)

    Lee, Alexander; Iskander, John M; Gupta, Nitin; Borg, Brian B; Zuckerman, Gary; Banerjee, Bhaskar; Gyawali, C Prakash

    2011-08-01

    Endoscopist fatigue potentially impacts colonoscopy. Fatigue is difficult to quantitate, but polyp detection rates between non-fatigued and fatigued time periods could represent a surrogate marker. We assessed whether timing variables impacted polyp detection rates at a busy tertiary care endoscopy suite. Consecutive patients undergoing colonoscopy were retrospectively identified. Indications, clinical demographics, pre-procedural, and procedural variables were extracted from chart review; colonoscopy findings were determined from the procedure reports. Three separate timing variables were assessed as surrogate markers for endoscopist fatigue: morning vs. afternoon procedures, start times throughout the day, and queue position, a unique variable that takes into account the number of procedures performed before the colonoscopy of interest. Univariate and multivariate analyses were performed to determine whether timing variables and other clinical, pre-procedural, and procedural variables predicted polyp detection. During the 4-month study period, 1,083 outpatient colonoscopy procedures (57.5±0.5 years, 59.5% female) were identified, performed by 28 endoscopists (mean 38.7 procedures/endoscopist), with a mean polyp detection rate of 0.851/colonoscopy. At least, one adenoma was detected in 297 procedures (27.4%). A 12.4% reduction in mean detected polyps was detected between morning and afternoon procedures (0.90±0.06 vs. 0.76±0.06, P=0.15). Using start time on a continuous scale, however, each elapsed hour in the day was associated with a 4.6% reduction in polyp detection (P=0.005). When queue position was assessed, a 5.4% reduction in polyp detection was noted with each increase in queue position (P=0.016). These results remained significant when controlled for each individual endoscopist. Polyp detection rates decline as time passes during an endoscopist's schedule, potentially from endoscopist fatigue. Queue position may be a novel surrogate measure for

  15. The stationary G/G/s queue with non-identical servers

    Directory of Open Access Journals (Sweden)

    Pierre Le Gall

    1998-01-01

    Full Text Available We extend a recently developed factorization method to the case of the G/G/s queue with non-identical servers, by presenting three simple properties which lead to a simple numerical calculation method. We compare our results with those determined by classical Markovian (phase methods in the case of the symmetrical M/G/s queue, and for the mean queueing delay we compare with results given by traffic simulation.

  16. 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.

  17. 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.

  18. A Brownian model for multiclass queueing networks with finite buffers

    Science.gov (United States)

    Dai, Wanyang

    2002-07-01

    This paper is concerned with the heavy traffic behavior of a type of multiclass queueing networks with finite buffers. The network consists of d single server stations and is populated by K classes of customers. Each station has a finite capacity waiting buffer and operates under first-in first-out (FIFO) service discipline. The network is assumed to have a feedforward routing structure under a blocking scheme. A server stops working when the downstream buffer is full. The focus of this paper is on the Brownian model formulation. More specifically, the approximating Brownian model for the networks is proposed via the method of showing a pseudo-heavy-traffic limit theorem which states that the limit process is a reflecting Brownian motion (RBM) if the properly normalized d-dimensional workload process converges in distribution to a continuous process. Numerical algorithm with finite element method has been designed to effectively compute the solution of the Brownian model (W. Dai, Ph.D. thesis (1996); X. Shen et al. The finite element method for computing the stationary distribution of an SRBM in a hypercube with applications to finite buffer queueing networks, under revision for Queueing Systems).

  19. On a multilevel controlled bulk queueing system MX/Gr,R/1

    Directory of Open Access Journals (Sweden)

    Lev Abolnikov

    1992-01-01

    Full Text Available The authors introduce and study a class of bulk queueing systems with a compound Poisson input modulated by a semi-Markov process, multilevel control service time and a queue length dependent service delay discipline. According to this discipline, the server immediately starts the next service act if the queue length is not less than r; in this case all available units, or R (capacity of the server of them, whichever is less, are taken for service. Otherwise, the server delays the service act until the number of units in the queue reaches or exceeds level r.

  20. A queueing system with a fixed accumulation level, random server capacity and capacity dependent service time

    Directory of Open Access Journals (Sweden)

    Jewgeni H. Dshalalow

    1992-01-01

    Full Text Available This paper introduces a bulk queueing system with a single server processing groups of customers of a variable size. If upon completion of service the queueing level is at least r the server takes a batch of size r and processes it a random time arbitrarily distributed. If the queueing level is less than r the server idles until the queue accumulates r customers in total. Then the server capacity is generated by a random number equals the batch size taken for service which lasts an arbitrarily distributed time dependent on the batch size.

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

    National Research Council Canada - National Science Library

    Li, Jing; Cui, Yidong; Ma, Yan

    2015-01-01

    .... 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...

  2. Management of active Crohn disease.

    Science.gov (United States)

    Cheifetz, Adam S

    2013-05-22

    Treatment of Crohn disease is rapidly evolving, with the induction of novel biologic therapies and newer, often more intensive treatment approaches. Knowing how to treat individual patients in this quickly changing milieu can be a challenge. To review the diagnosis and management of moderate to severe Crohn disease, with a focus on newer treatments and goals of care. MEDLINE was searched from 2000 to 2011. Additional citations were procured from references of select research and review articles. Evidence was graded using the American Heart Association level-of-evidence guidelines. Although mesalamines are still often used to treat Crohn disease, the evidence for their efficacy is lacking. Corticosteroids can be effectively used to induce remission in moderate to severe Crohn disease, but they do not maintain remission. The mainstays of treatment are immunomodulators and biologics, particularly anti-tumor necrosis factor. Immunomodulators and biologics are now the preferred treatment options for Crohn disease.

  3. Message passing with parallel queue traversal

    Science.gov (United States)

    Underwood, Keith D [Albuquerque, NM; Brightwell, Ronald B [Albuquerque, NM; Hemmert, K Scott [Albuquerque, NM

    2012-05-01

    In message passing implementations, associative matching structures are used to permit list entries to be searched in parallel fashion, thereby avoiding the delay of linear list traversal. List management capabilities are provided to support list entry turnover semantics and priority ordering semantics.

  4. Rare-event simulation for tandem queues: A simple and efficient importance sampling scheme

    NARCIS (Netherlands)

    Miretskiy, D.; Scheinhardt, W.; Mandjes, M.

    2009-01-01

    This paper focuses on estimating the rare event of overflow in the downstream queue of a tandem Jackson queue, relying on importance sampling. It is known that in this setting ‘traditional’ state-independent schemes perform poorly. More sophisticated state-dependent schemes yield asymptotic

  5. Rainfall time series synthesis from queue scheduling of rain event fractals over radio links

    Science.gov (United States)

    Alonge, Akintunde A.; Afullo, Thomas J.

    2015-12-01

    Rainfall attenuation over wireless networks stems from random fluctuations in the natural process of arriving rainfall rates over radio links. This arrival process results in discernible rainfall traffic pattern which manifests as naturally scheduled and queue-generated rain spikes. Hence, the phenomenon of rainfall process can be approached as a semi-Markovian queueing process, with event characteristics dependent on queue parameters. However, a constraint to this approach is the knowledge of the physical characteristics of queue-generated rain spikes. Therefore, this paper explores the probability theory and descriptive mathematics of rain spikes in rainfall processes. This investigation presents the synthesis of rainfall queue with rain spikes at subtropical and equatorial locations of Durban (29°52'S, 30°58'E) and Butare (2°36'S, 29°44'E), respectively. The resulting comparative analysis of rainfall distributions, using error analysis at both locations, reveals that queue-generated rainfall compares well with measured rainfall data set. This suggests that the time-varying process of rainfall, though stochastic, can be synthesized via queue scheduling with the application of relevant queue parameters at any location.

  6. Busy Period of a Delayed-Service Single-Server Poisson Queue

    Science.gov (United States)

    Haghighi, A. M.; Mishev, D. P.; Chukova, S. S.

    2007-10-01

    In this paper we investigate busy period of a single-server Poisson queue with delayed-service. We will analyze this model by considering M/G/1 approximating a non-Markovian system. We obtain the distribution of the length of a busy period. Additionally, steady-state mean and distribution of the queue length will be obtained.

  7. Analysis of a single server queue interacting with a fluid reservoir

    NARCIS (Netherlands)

    Adan, I.J.B.F.; van Doorn, Erik A.; Resing, J.A.C.; Scheinhardt, Willem R.W.

    1998-01-01

    We consider a single-server queueing system with Poisson arrivals in which the speed of the server depends on whether an associated fluid reservoir is empty or not. Conversely, the rate of change of the content of the reservoir is determined by the state of the queueing system, since the reservoir

  8. Queueing system analysis of multi server model at XYZ insurance company in Tasikmalaya city

    Science.gov (United States)

    Muhajir, Ahmad; Binatari, Nikenasih

    2017-08-01

    Queueing theory or waiting line theory is a theory that deals with the queue process from the customer comes, queue to be served, served and left on service facilities. Queue occurs because of a mismatch between the numbers of customers that will be served with the available number of services, as an example at XYZ insurance company in Tasikmalaya. This research aims to determine the characteristics of the queue system which then to optimize the number of server in term of total cost. The result shows that the queue model can be represented by (M/M/4):(GD/∞/∞), where the arrivals are Poisson distributed while the service time is following exponential distribution. The probability of idle customer service is 2,39% of the working time, the average number of customer in the queue is 3 customers, the average number of customer in a system is 6 customers, the average time of a customer spent in the queue is 15,9979 minutes, the average time a customer spends in the system is 34,4141 minutes, and the average number of busy customer servicer is 3 server. The optimized number of customer service is 5 servers, and the operational cost has minimum cost at Rp 4.323.

  9. First in Line Waiting Times as a Tool for Analysing Queueing Systems

    DEFF Research Database (Denmark)

    Koole, G. M.; Nielsen, Bo Friis; Nielsen, Thomas Bang

    2012-01-01

    We introduce a new approach to modelling queueing systems where the priority or the routing of customers depends on the time the first customer has waited in the queue. This past waiting time of the first customer in line, WFIL, is used as the primary variable for our approach. A Markov chain...

  10. An infinite-server queue influenced by a semi-Markovian environment

    NARCIS (Netherlands)

    Fralix, B.H.; Adan, I.J.B.F.

    2008-01-01

    We consider an infinite-server queue, where the arrival and service rates are both governed by a semi-Markov process that's independent of all other aspects of the queue. In particular, we derive a system of equations that are satisfied by various "parts" of the generating function of the

  11. An infinite-server queue influenced by a semi-Markovian environment

    NARCIS (Netherlands)

    Fralix, B.H.; Adan, I.J.B.F.

    2009-01-01

    We consider an infinite-server queue, where the arrival and service rates are both governed by a semi-Markov process that is independent of all other aspects of the queue. In particular, we derive a system of equations that are satisfied by various "parts" of the generating function of the

  12. The queue M|G|1 with Markov modulated arrivals and services

    NARCIS (Netherlands)

    Regterschot, G.J.K.; de Smit, J.H.A.

    1986-01-01

    We study an M|G|1 queue in which both the arrival rate and the service time distribution depend on the state of an underlying finite-state Markov chain. The solution is obtained by a matrix factorization method. This leads to results for waiting times and queue lengths both at arrival epochs and in

  13. 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.

  14. 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.

  15. 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.

  16. Algorithm for queueing networks with multi-rate traffic

    DEFF Research Database (Denmark)

    Iversen, Villy Bæk; King-Tim, Ko

    2011-01-01

    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...... is reversibility which implies that the arrival process and departure process are identical processes, for example state-dependent Poisson processes. This property is equivalent to reversibility. Due to product form, an open network with multi-rate traffic is easy to evaluate by convolution algorithms because...

  17. 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

  18. STATIONARY CHARACTERISTICS OF UNRELIABLE QUEUEING SYSTEM WITH BATCH MARKOVIAN ARRIVAL PROCESS AND RESERVE SERVER

    Directory of Open Access Journals (Sweden)

    V. I. Klimenok

    2016-01-01

    Full Text Available In the paper, a queueing system with unreliable server and so called «cold» redundancy is analyzed. The system consists of an infinite buffer, the main unreliable server and the reliable reserve server. The term «cold reserve» means that the reserve server is off until the main server is in good order and is activated when the main server is under repair. The input flow to the system is a BMAP (Batch Markovian Arrival Process. Breakdowns arrive to the main server according to a MAP (Markovian Arrival Process. Service times as well as repair time have PH (Phase type distribution. A condition for the stable operation of the system is shown, its stationary distribution and the main characteristics are calculated and the expression for the Laplace – Stieltjes transform of the sojourn time distribution is derrived.

  19. Managing School-Based Professional Development Activities

    Science.gov (United States)

    Cheng, Eric C. K.

    2017-01-01

    Purpose: The purpose of this paper is to present a model to assist school leaders in managing the professional development activities of teachers. The model illustrates the important role of principals in promoting continuing professional development (CPD), chiefly by cultivating a collaborative learning culture and formulating policy.…

  20. Identification of waiting time distribution of M/G/1, Mx/G/1, GIr/M/1 queueing systems

    Directory of Open Access Journals (Sweden)

    A. Ghosal

    1988-01-01

    Full Text Available This paper brings out relations among the moments of various orders of the waiting time of the 1st customer and a randomly selected customer of an arrival group for bulk arrivals queueing models, and as well as moments of the waiting time (in queue for M/G/1 queueing system. A numerical study of these relations has been developed in order to find the (β1,β2 measures of waiting time distribution in a comutable form. On the basis of these measures one can look into the nature of waiting time distribution of bulk arrival queues and the single server M/G/1 queue.

  1. 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.

  2. 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.

  3. Queueing up for enzymatic processing: correlated signaling through coupled degradation

    Science.gov (United States)

    Cookson, Natalie A; Mather, William H; Danino, Tal; Mondragón-Palomino, Octavio; Williams, Ruth J; Tsimring, Lev S; Hasty, Jeff

    2011-01-01

    High-throughput technologies have led to the generation of complex wiring diagrams as a post-sequencing paradigm for depicting the interactions between vast and diverse cellular species. While these diagrams are useful for analyzing biological systems on a large scale, a detailed understanding of the molecular mechanisms that underlie the observed network connections is critical for the further development of systems and synthetic biology. Here, we use queueing theory to investigate how ‘waiting lines' can lead to correlations between protein ‘customers' that are coupled solely through a downstream set of enzymatic ‘servers'. Using the E. coli ClpXP degradation machine as a model processing system, we observe significant cross-talk between two networks that are indirectly coupled through a common set of processors. We further illustrate the implications of enzymatic queueing using a synthetic biology application, in which two independent synthetic networks demonstrate synchronized behavior when common ClpXP machinery is overburdened. Our results demonstrate that such post-translational processes can lead to dynamic connections in cellular networks and may provide a mechanistic understanding of existing but currently inexplicable links. PMID:22186735

  4. 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.

  5. Single retrial queues with service option on arrival

    Directory of Open Access Journals (Sweden)

    K. Farahmand

    1997-01-01

    Full Text Available We analyze a queueing system in which customers can call in to request service. A proportion, say 1−p of them on their arrival test the availability of the server. If the server is free the customer enters service immediately. Otherwise, if the service system is occupied, the customer joins a source of unsatisfied customers called the orbit. The remaining p proportion of the initial customers enter the orbit directly, without examining the state of the server. We consider two models characterized by the discipline governing the order of re-requests for service from the orbit. First, all the customers from the orbit apply at a fixed rate. Secondly, customers from the orbit are discouraged and reduce their rate of demand as more customers join the orbit. The arrival at and the demands from the orbit are both assumed to be according to the Poisson Process. However, the service times for both primary customers and customers from the orbit are assumed to have a general distribution. We calculate several characteristic quantities of these queueing systems.

  6. Management of Logistics Activities and Costing Approaches

    Directory of Open Access Journals (Sweden)

    İlker KIYMETLİ ŞEN

    2014-06-01

    Full Text Available In recent years, enterprises are required to reconsider the management of logistics activities as a result of developments such as increasing competition, rapid technological development, and the shortening of product life cycles. As a result of globalization, costs of logistics activities have also increased depending on changes in the quality and quantity of logistics activities. According to research on logistics activities, the physical distribution costs of enterprises may reach up to 30% of sales. For this reason, the management of logistics operations and control of costs caused by these activities is a necessity. The increase in costs negatively impact on the financial performance of enterprises, cash flows, profitability and so value of the shares. The aim of this study was to describe the structure of logistics costs and logistics activities to explain the methods used in costing. For this purpose, many studies in the literature were investigated. The aim of this study was to describe the structure of logistics costs and logistics activities to explain the methods used in costing. For this purpose, many studies in the literature were investigated.

  7. 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.

  8. 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%.

  9. A Taylor series approach for coupled queueing systems with intermediate load

    Science.gov (United States)

    Evdokimova, Ekaterina; Wittevrongel, Sabine; Fiems, Dieter

    2017-07-01

    We focus on the numerical analysis of a coupled queueing system with Poisson arrivals and exponentially distributed service times. Such a system consists of multiple queues served by a single server. Service is synchronised meaning that there is a departure from every queue upon service completion and there is no service whenever one of the queues is empty. It was shown before that the terms in the Maclaurin series expansion of the steady-state distribution of this queueing system when the service rate is sent to 0 (overload) can be calculated efficiently. In the present paper we extend this approach to lower loads. We focus on a sequence of Taylor series expansions of the stationary distribution around increasing service rates. For each series expansion, we use Jacobi iteration to calculate the terms in the series expansion where the initial solution is the approximation found by the preceding series expansion. As the generator matrix of the queueing system at hand is sparse, the numerical complexity of a single Jacobi iteration is O(N MK), where N is the order of the series expansion, K is the number of queues and M is the size of the state space. Having a good initial solution reduces the number of Jacobi iterations considerably, meaning that we can find a sequence of good approximations of the steady state probabilities fast.

  10. Characteristics of rainfall queues for rain attenuation studies over radio links at subtropical and equatorial Africa

    Science.gov (United States)

    Alonge, Akintunde A.; Afullo, Thomas J.

    2014-08-01

    Attenuation due to precipitation remains an important design factor in the future deployment of terrestrial and earth-space communication radio links. Largely, there are concerted efforts to understand the dynamics of precipitation in attenuation occurrence at subtropical, tropical, and equatorial region of Africa. In this deliberate approach, rainfall spikes pertaining to rain cells are conceptualized as distinct rain spike traffic over radio links, by applying queueing theory concepts. The queue distributions at Durban (29°52'S, 30°58'E) and Butare (2°36'S, 29°44'E)—respectively, of subtropical and equatorial climates—are investigated from distrometer measurements. The data sets at both sites are observed over four rain regimes: drizzle, widespread, shower, and thunderstorm. The queue parameters of service time and inter-arrival of rain spikes traffic at both regions are found to be Erlang-k distributed (Ek) and exponentially distributed (M), respectively. It is established that the appearance of rain rates over radio links invariably follows a First Come, First Served (FCFS), multi-server (s), infinite queue, and semi-Markovian process, designated as M/Ek/s/∞/FCFS discipline. Modeled queue parameters at both regions are found to vary significantly over different regimes. However, these queue parameters over the entire data set suggest similar queue patterns at both sites. More importantly, power law relationships describing other queue-related parameters are formulated. The paper concludes by demonstrating an application of queueing theory for rainfall synthesis. The proposed technique will provide an alternative method of estimating rain cell sizes and rain attenuation over satellite and terrestrial links.

  11. Managing CSCL Activity through networking models

    Directory of Open Access Journals (Sweden)

    Luis Casillas

    2014-04-01

    Full Text Available This study aims at managing activity carried out in Computer-Supported Collaborative Learning (CSCL environments. We apply an approach that gathers and manages the knowledge underlying huge data structures, resulting from collaborative interaction among participants and stored as activity logs. Our method comprises a variety of important issues and aspects, such as: deep understanding of collaboration among participants in workgroups, definition of an ontology for providing meaning to isolated data manifestations, discovering of knowledge structures built in huge amounts of data stored in log files, and development of high-semantic indicators to describe diverse primitive collaborative acts, and binding these indicators to formal descriptions defined in the collaboration ontology; besides our method includes gathering collaboration indicators from web forums using natural language processing (NLP techniques.

  12. Managing Brain Extracellular K(+) during Neuronal Activity

    DEFF Research Database (Denmark)

    Larsen, Brian Roland; Stoica, Anca; MacAulay, Nanna

    2016-01-01

    isoform compositions of the Na(+)/K(+)-ATPase remain unresolved. The various cell types in the brain serve a certain temporal contribution in the face of network activity; astrocytes respond directly to the immediate release of K(+) from neurons, whereas the neurons themselves become the primary K...... characteristics required to fulfill their distinct physiological roles in clearance of K(+) from the extracellular space in the face of neuronal activity. Understanding the nature, impact and effects of the various Na(+)/K(+)-ATPase isoform combinations in K(+) management in the central nervous system might...

  13. Exact dynamical state of the exclusive queueing process with deterministic hopping.

    Science.gov (United States)

    Arita, Chikashi; Schadschneider, Andreas

    2011-11-01

    The exclusive queueing process (EQP) has recently been introduced as a model for the dynamics of queues that takes into account the spatial structure of the queue. It can be interpreted as a totally asymmetric exclusion process of varying length. Here we investigate the case of deterministic bulk hopping p=1 that turns out to be one of the rare cases where exact nontrivial results for the dynamical properties can be obtained. Using a time-dependent matrix product form we calculate several dynamical properties, e.g., the density profile of the system.

  14. Mixed loss and delay retrial queueing system with two classes of customers

    Directory of Open Access Journals (Sweden)

    B. Krishna Kumar

    2007-10-01

    Full Text Available This paper is concerned with the analysis of a single-server batch arrival retrial queue with two classes of customers. In the case of blocking, the class-1 customers leave the system forever whereas the class-2 customers leave the service area and enter the orbit and wait to be served later. The necessary and sufficient condition for the system to be stable is derived and analytic results for the queue length distribution as well as some performance measures of the system under steady state condition are obtained. A general decomposition law for the retrial queueing system is established.

  15. 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.

  16. IAEA activities on steam generator life management

    Energy Technology Data Exchange (ETDEWEB)

    Gueorguiev, B.; Lyssakov, V.; Trampus, P. [International Atomic Energy Agency, Div. of Nuclear Power, Vienna (Austria)

    2002-07-01

    The International Atomic Energy Agency (IAEA) carries out a set of activities in the field of Nuclear Power Plant (NPP) life management. Main activities within this area are implemented through the Technical Working Group on Life Management of NPPs, and mostly concentrated on studies of understanding mechanisms of degradation and their monitoring, optimisation of maintenance management, economic aspects, proven practices of and approaches to plant life management including decommissioning. The paper covers two ongoing activities related to steam generator life management: the International Database on NPP Steam Generators and the Co-ordinated Research Project on Verification of WWER Steam Generator Tube Integrity (WWER is the Russian designed PWR). The lifetime assessment of main components relies on an ability to assess their condition and predict future degradation trends, which to a large extent is dependent on the availability of relevant data. Effective management of ageing and degradation processes requires a large amount of data. Several years ago the IAEA started to work on the International Database on NPP Life Management. This is a multi-module database consisting of modules such as reactor pressure vessels materials, piping, steam generators, and concrete structures. At present the work on pressure vessel materials, on piping as well as on steam generator is completed. The paper will present the concept and structure of the steam generator module of the database. In countries operating WWER NPPs, there are big differences in the eddy current inspection strategy and practice as well as in the approach to steam generator heat exchanger tube structural integrity assessment. Responding to the need for a co-ordinated research to compare eddy current testing results with destructive testing using pulled out tubes from WWER steam generators, the IAEA launched this project. The main objectives of the project are to summarise the operating experiences of WWER

  17. COMPUTER APPLICATIONS IN U.S. COAST GUARD PERSONNEL MANAGEMENT.

    Science.gov (United States)

    MANAGEMENT PLANNING AND CONTROL, AUTOMATIC, AUTOMATION, QUEUEING THEORY , LINEAR PROGRAMMING, DECISION THEORY , STATISTICAL PROCESSES, PROBABILITY, FEASIBILITY STUDIES, ARMY, NAVY, AIR FORCE....COAST GUARD, *PERSONNEL MANAGEMENT , NAVAL PERSONNEL, JOB ANALYSIS, DATA PROCESSING, OPERATIONS RESEARCH, NAVAL TRAINING, COMPUTER PROGRAMMING

  18. Design professional activity analysis in design management

    Directory of Open Access Journals (Sweden)

    Claudia de Souza Libanio

    2013-08-01

    Full Text Available Design use perception, as an essential element for achieving competitive advantage, also suggests the need to manage the design activities in companies. However, a few is discussed about the activity of these design professionals who participate in this process, their roles, functions and competencies, including  their connections to a company and other involved sectors. This article aims to analyze, during the design management processes, the work relations of design professionals connected to organizations both internal and externally, in order to comprehend the structure and intervenient factors on the activity of these professionals, as well as the interactions with their main coworkers. The methodology was exploratory and qualitative, using in-depth interviews with three design professionals. Subsequently, the responses were analyzed allowing the comparison of these obtained data to the theoretical bases researched. Through this case study, it was possible to realize the aspects and the structure of the design professional activity, connected intern and externally to organizations, as well as its relations with the main coworkers.

  19. Fast Multidimensional Nearest Neighbor Search Algorithm Using Priority Queue

    Science.gov (United States)

    Ajioka, Shiro; Tsuge, Satoru; Shishibori, Masami; Kita, Kenji

    Nearest neighbor search in high dimensional spaces is an interesting and important problem which is relevant for a wide variety of applications, including multimedia information retrieval, data mining, and pattern recognition. For such applications, the curse of high dimensionality tends to be a major obstacle in the development of efficient search methods. This paper addresses the problem of designing an efficient algorithm for high dimensional nearest neighbor search using a priority queue. The proposed algorithm is based on a simple linear search algorithm and eliminates unnecessary arithmetic operations from distance computations between multidimensional vectors. Moreover, we propose two techniques, a dimensional sorting method and a PCA-based method, to accelerate multidimensional search. Experimental results indicate that our scheme scales well even for a very large number of dimensions.

  20. 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.

  1. Carbon sink activity of managed grasslands

    Science.gov (United States)

    Klumpp, Katja; Chabbi, Abad; Gastal, Francois; Senapati, Nimai; Charrier, Xavier; Darsonville, Olivier; Creme, Alexandra

    2017-04-01

    In agriculture, a large proportion of GHG emission saving potential may be achieved by means of soil C sequestration. Recent demonstrations of carbon sink activities however, often questioned the existence of C storing grasslands, as uncertainty surrounding estimates are often larger than the sink itself. Besides climate, key components of the carbon sink activity in grasslands are type and intensity of management practices. Here, we analysed long term data on C flux and soil organic carbon stocks for two long term (>13yrs) national observation sites in France (SOERE-ACBB). These sites comprise a number of grassland fields and managements options (i.e. permanent, sowing, grazing, mowing, and fertilization) offering an opportunity to study carbon offsets (i.e. compensation of CH4 and N2O emissions), climatic-management interactions and trade-offs concerning ecosystem services (e.g. production). Furthermore, for some grassland fields, the carbon sink activity was compared using two methods; repeated soil inventory and estimation of the ecosystem C budget by continuous measurement of CO2 exchange (i.e. eddy covariance) in combination with quantification of other C imports and exports, necessary to estimate net C storage. In general grasslands, were a potential sink of C (i.e. net ecosystem exchange, NEE), where grazed sites had lower NEE compared the cut site. However, when it comes to net C storage (NCS), mowing reduced markedly potential sink leading to very low NCS compared to grazed sites. Including non-CO2 fluxes (CH4 and N2O emission) in the budget, revealed that GHG emissions were offset by C sink activity.

  2. Impacts assessment of dynamic speed harmonization with queue warning : task 3, impacts assessment report.

    Science.gov (United States)

    2015-06-01

    This report assesses the impacts of a prototype of Dynamic Speed Harmonization (SPD-HARM) with Queue : Warning (Q-WARN), which are two component applications of the Intelligent Network Flow Optimization : (INFLO) bundle. The assessment is based on an...

  3. 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 ...

  4. Application of the queueing theory with Monte Carlo simulation to inhalation toxicology.

    Science.gov (United States)

    Wu, G

    1998-05-01

    Various models have been developed in modelling of inhalation toxicology. The deterministic approach, which has been used to date in most of the models, needs to consider numerous factors, e.g. anatomical structure, breathing frequency, humidity, metabolism rate, partition coefficients, pulmonary ventilation, perfusion rates, unidirectional/cyclic air flow, non-steady-state, steady-state, etc. In the present study, a stochastic approach was used in the modelling of inhalation toxicology, because there is a phenomenological analogy between the queueing system and respiratory system dealing with inhaled toxicants. Using the queueing theory, the amounts of toxicants in the respiratory system, the time needed to remove the accumulated amounts of toxicants from the respiratory system, etc. can be estimated. The Monte Carlo simulation of queueing process was performed to analyse cigarette smoking, and shows the potential use of the queueing theory in inhalation toxicology.

  5. On the ergodicity bounds for a constant retrial rate queueing model

    OpenAIRE

    Zeifman, Alexander; Satin, Yacov; Morozov, Evsey; Nekrasova, Ruslana; Gorshenin, Andrey

    2015-01-01

    We consider a Markovian single-server retrial queueing system with a constant retrial rate. Conditions of null ergodicity and exponential ergodicity for the correspondent process, as well as bounds on the rate of convergence are obtained.

  6. Repairable queue with non-exponential service time and variable breakdown rates

    Science.gov (United States)

    Khew, Koh Siew; Hin, Pooi Ah; Fei, Tan Yi

    2015-05-01

    Consider a single server queue in which the service station may breakdown according to a Poisson process with rates γ in busy time and γ' in idle time respectively. After a breakdown, the service station will be repaired immediately and the repair time is assumed to have an exponential distribution with rate δ. Suppose the arrival time has an exponential distribution with rate λ, and the probability density function g(t) and the cumulative distribution function G(t) of the service time are such that the rate g(t)/[1 - G(t)] tends to a constant as t tends to infinity. 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 of the system.

  7. Methods for estimating vehicle queues at a marine terminal: A computational comparison

    Directory of Open Access Journals (Sweden)

    Chen Gang

    2014-09-01

    Full Text Available A long queue of vehicles at the gate of a marine terminal is a common traffic phenomenon in a port-city, which sometimes causes problems in urban traffic. In order to be able to solve this issue, we firstly need accurate models to estimate such a vehicle queue length. In this paper, we compare the existing methods in a case study, and evaluate their advantages and disadvantages. Particularly, we develop a simulation-based regression model, using the micro traffic simulation software PARAMIC. In simulation, it is found that the queue transient process follows a natural logarithm curve. Then, based on these curves, we develop a queue length estimation model. In the numerical experiment, the proposed model exhibits better estimation accuracy than the other existing methods

  8. 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.

  9. Study on queueing behavior in pedestrian evacuation by extended cellular automata model

    Science.gov (United States)

    Hu, Jun; You, Lei; Zhang, Hong; Wei, Juan; Guo, Yangyong

    2018-01-01

    This paper proposes a pedestrian evacuation model for effective simulation of evacuation efficiency based on extended cellular automata. In the model, pedestrians' momentary transition probability to a target position is defined in terms of the floor field and queueing time, and the critical time is defined as the waiting time threshold in a queue. Queueing time and critical time are derived using Fractal Brownian Motion through analysis of pedestrian arrival characteristics. Simulations using the platform and actual evacuations were conducted to study the relationships among system evacuation time, average system velocity, pedestrian density, flow rate, and critical time. The results demonstrate that at low pedestrian density, evacuation efficiency can be improved through adoption of the shortest route strategy, and critical time has an inverse relationship with average system velocity. Conversely, at higher pedestrian densities, it is better to adopt the shortest queueing time strategy, and critical time is inversely related to flow rate.

  10. Store operation with conditional push of a tag value to a queue

    Science.gov (United States)

    Heidelberger, Philip; Steinmacher-Burow, Burkhard

    2015-07-28

    According to one embodiment, a method for a store operation with a conditional push of a tag value to a queue is provided. The method includes configuring a queue that is accessible by an application, setting a value at an address in a memory device including a memory and a controller, receiving a request for an operation using the value at the address and performing the operation. The method also includes the controller writing a result of the operation to the address, thus changing the value at the address, the controller determining if the result of the operation meets a condition and the controller pushing a tag value to the queue based on the condition being met, where the tag value in the queue indicates to the application that the condition is met.

  11. Non-stationary analysis of queueing delay behavior in the GI/M/1/N-type queue with server working vacations

    Science.gov (United States)

    Kempa, Wojciech M.

    2015-11-01

    A finite-buffer GI/M/1/N-type queueing model with single working vacations is considered. Every time when the system becomes empty the server initializes an exponentially distributed single working vacation period, during which the processing of jobs is carried out with another (slower) rate. After finishing the vacation period the service process is being continued with normal (higher) speed. The next working vacation period is started at the next moment at which the queue empties and so on. The systems of integral equations for time-dependent queueing delay distributions, conditioned by the initial level of buffer saturation and related to each other, are built for systems beginning the operation in normal and working vacation modes, separately. The solutions for corresponding systems written for Laplace transforms are given explicitly using the linear algebraic approach.

  12. Optimal control for a BMAP/G/1 queue with two service modes

    Directory of Open Access Journals (Sweden)

    Alexander N. Dudin

    1999-01-01

    Full Text Available Queueing models with controllable service rate play an important role in telecommunication systems. This paper deals with a single-server model with a batch Markovian arrival process (BMAP and two service modes, where switch-over times are involved when changing the service mode. The embedded stationary queue length distribution and the explicit dependence of operation criteria on switch-over levels and derived.

  13. "SIRIUS-T" Package For Characteristics Evaluation Of The Queueing System

    OpenAIRE

    Dudin, A.; Klimenok, V.; Tsarenkov, G.

    2011-01-01

    This paper contains description of new features of software package "Sirius-T" as an elaboration of "Sirius++" and "Sirius-C" packages. "Sirius-T" introduces new models for calculation characteristics of tandem queues allowing performance evaluation and capacity planning of the telecommunication networks and their fragments. Additionally, the software facilitates a study of queueing models under consideration of correlated service and evaluation of the algorithms' numerical complexity.

  14. Recent Advances in Queueing Networks : A Survey With Applications to Automated Manufacturing

    OpenAIRE

    R Ram; Vismnadham, N

    1990-01-01

    Queueing models have been the most widely used analytical modelling tool for performance studies on complex manufacturing systems. Conventional analysis has proceeded along the lines of product form queueing models, and their extensions. Traditional applications of these models have been restricted to the computation of mean values of important performance measures; besides, certain simplifying assumptions have to be made for these model6 to be applicable. The last decade has witnessed import...

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

    Science.gov (United States)

    Kearney, Michael J.

    2004-09-01

    A well-known discrete-time, single-server queueing system with mean arrival rate lgr and mean departure rate mgr 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(-Dx1/2) for all rgr \

  16. Transient behaviour of the M/M/2 queue with catastrophes

    Directory of Open Access Journals (Sweden)

    B. Krishna Kumar

    2007-10-01

    Full Text Available This paper presents a transient solution for the system size in the M/M/2 queue with the possibility of catastrophes at the service stations. The state probability of the system size at time t, where the queue starts with any number of customers, in obtained. Asymptotic behaviour of the probability of the server being idle and mean system size are discussed.

  17. Transient analysis of a two-heterogeneous servers queue with impatient behavior

    Directory of Open Access Journals (Sweden)

    Sherif I. Ammar

    2014-04-01

    Full Text Available Recently, [1] have obtained the transient solution of multi-server queue with balking and reneging. In this paper, a similar technique is used to drive a new elegant explicit solution for a two heterogeneous servers queue with impatient behavior. In addition, steady-state probabilities of the system size are studied and some important performance measures are discussed for the considered system.

  18. Stochastic Prediction and Feedback Control of Router Queue Size in a Virtual Network Environment

    Science.gov (United States)

    2014-09-18

    OPNET model of the simple queuing system had used [3]. Client ServerRouter Figure 3.8: 1 router network topology 3.4.1.2 2 Routers Network...traffic demand with the inclusion of real operating systems and applications versus application models provided by discrete-event modeling and...2.1 Network Queues The mathematical study of queues or waiting lines is referred to as queuing theory. It consist of models constructed with the aim

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

    Directory of Open Access Journals (Sweden)

    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.

  20. 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.

  1. Factorized time-dependent distributions for certain multiclass queueing networks and an application to enzymatic processing networks

    Science.gov (United States)

    Mather, W.H.; Hasty, J.; Tsimring, L.S.

    2013-01-01

    Motivated by applications in biological systems, we show for certain multiclass queueing networks that time-dependent distributions for the multiclass queue-lengths can have a factorized form which reduces the problem of computing such distributions to a similar problem for related single-class queueing networks. We give an example of the application of this result to an enzymatic processing network. PMID:24596432

  2. Conceptual basis of management activities diagnostics in the system of process-structured management

    OpenAIRE

    Kuzmin, O. Ye.; Melnyk, O. H.; Mukan, O. V.

    2014-01-01

    The role and place of diagnostics in management systems of enterprises and peculiarities of management activities diagnostics are considered. The essence and characteristics of process-structured management as the most effective integrated approach to management in current operation conditions are described. The conceptual basis of management activities diagnostics in the system of process-structured management is worked out, it foreseeing distinguishing and specify...

  3. Classroom Management to Support Active Middle Level Classrooms

    Directory of Open Access Journals (Sweden)

    Bryan Lloyd McCoy

    2012-09-01

    Full Text Available

    This article presents a discussion of connections between middle level concepts of teaching and learning and managing a classroom through creating opportunities for active and engaged learning. The article argues and concludes that classroom management is more about managing learning than managing behavior and that one effective way to manage student behavior is to create an environment where students continuously engage in active learning (Haydon, Borders, Embury, & Clarke, 2009.

  4. Classroom Management to Support Active Middle Level Classrooms

    Directory of Open Access Journals (Sweden)

    Bryan Lloyd McCoy

    2012-09-01

    Full Text Available This article presents a discussion of connections between middle level concepts of teaching and learning and managing a classroom through creating opportunities for active and engaged learning. The article argues and concludes that classroom management is more about managing learning than managing behavior and that one effective way to manage student behavior is to create an environment where students continuously engage in active learning (Haydon, Borders, Embury, & Clarke, 2009.

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

    Directory of Open Access Journals (Sweden)

    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.

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

    Directory of Open Access Journals (Sweden)

    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.

  7. 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.

  8. Network-of-queues approach to B-cell-receptor affinity discrimination

    Science.gov (United States)

    Felizzi, Federico; Comoglio, Federico

    2012-06-01

    The immune system is one of the most complex signal processing machineries in biology. The adaptive immune system, consisting of B and T lymphocytes, is activated in response to a large spectrum of pathogen antigens. B cells recognize and bind the antigen through B-cell receptors (BCRs) and this is fundamental for B-cell activation. However, the system response is dependent on BCR-antigen affinity values that span several orders of magnitude. Moreover, the ability of the BCR to discriminate between affinities at the high end (e.g., 109M-1-1010M-1) challenges the formulation of a mathematical model able to robustly separate these affinity-dependent responses. Queuing theory enables the analysis of many related processes, such as those resulting from the stochasticity of protein binding and unbinding events. Here we define a network of queues, consisting of BCR early signaling states and transition rates related to the propensity of molecular aggregates to form or disassemble. By considering the family of marginal distributions of BCRs in a given signaling state, we report a significant separation (measured as Jensen-Shannon divergence) that arises from a broad spectrum of antigen affinities.

  9. A queueing approach to multi-site enzyme kinetics

    Science.gov (United States)

    Hochendoner, Philip; Ogle, Curtis; Mather, William H.

    2014-01-01

    Multi-site enzymes, defined as where multiple substrate molecules can bind simultaneously to the same enzyme molecule, play a key role in a number of biological networks, with the Escherichia coli protease ClpXP a well-studied example. These enzymes can form a low latency ‘waiting line’ of substrate to the enzyme's catalytic core, such that the enzyme molecule can continue to collect substrate even when the catalytic core is occupied. To understand multi-site enzyme kinetics, we study a discrete stochastic model that includes a single catalytic core fed by a fixed number of substrate binding sites. A natural queueing systems analogy is found to provide substantial insight into the dynamics of the model. From this, we derive exact results for the probability distribution of the enzyme configuration and for the distribution of substrate departure times in the case of identical but distinguishable classes of substrate molecules. Comments are also provided for the case when different classes of substrate molecules are not processed identically. PMID:24904740

  10. DESAIN FRAMEWORK MULTIMEDIA QUEUEING SYSTEM BERBASIS ANDROID ANTRIAN PASIEN PUSKESMAS

    Directory of Open Access Journals (Sweden)

    Erika Devi Udayanti

    2015-10-01

    Full Text Available Saat ini antrian di puskesmas masih dilakukan dengan metode konvensional, yaitu dengan menumpuk kartu registrasi. Metode seperti ini memungkinkan kartu menjadi terselip. Selain itu, penumpukan kartu yang tidak benar dapat mengakibatkan urutan menjadi tidak sesuai dengan urutan yang seharusnya. Pasien yang datang lebih ahir dimungkinkan untuk dapat dilayani lebih awal dari pasien yang sudah lama menunggu. Penelitian ini mengusulkan multimedia queueing system berbasis android untuk layanan antrian pasien puskesmas. Sistem ini mencatat antrian di dalam database server, sehingga tidak ada kartu yang terselip ataupun salah tumpuk. Lebih lanjut lagi, penelitian ini akan mengangkat kecanggihan mesin android sebagai input device. Sedangkan untuk output devicenya, menggunakan portable bluetooth printer dan layar LCD. Setiap pasien yang datang dapat mencetak tiket antrian dengan menyentuh tombol pada layar mesin android. Mesin android tersebut kemudian akan mencetak tiket melaui printer portable yang disediakan dan mengirim nomor antrian ke database server. Selain itu, mesin android ini juga memotret wajah pasien yang masuk, dan file foto akan dikirim beserta nomor antrian ke server. Pada saat giliran pasien tiba, layar LCD akan menampilkan nomor antrian pasien beserta fotonya. Metode ini diharapkan mampu menyelesaikan problem kartu registrasi terselip, dan juga membantu pasien yang buta huruf/angka. Kata Kunci: puskesmas, sistem antrian, android

  11. Preemptive queueing system with randomized push-out mechanism

    Science.gov (United States)

    Muliukha, Vladimir; Ilyashenko, Alexander; Zayats, Oleg; Zaborovsky, Vladimir

    2015-04-01

    In this article considered a queueing theory model with limited buffer size, one service channel, and two incoming flows. In this model one of the flows has a power to preempt other tasks. We call it a high-priority flow. Another one is low-priority. This priority mechanism is realized in a two different ways. The first one is a preemptive priority, which allows high-priority packets to interrupt low-priority packets in service channel and push them out. The second one is a randomized push-out mechanism with probability α, which allows us to choose what type of packets should be pushed out of the system when it is full. In this article we provide an algorithm for computing statistical characteristics of the model for all values of push-out probability α. We have used generating functions method to simplify the system of linear equations. This method allows us to reduce the order of linear equations system from k(k + 1)/2 to (k + 1). As the result we have got two effects in this model. The first one is a linear behavior of loss probabilities in the model with low overload. The second one is a "closing" of a system for low-priority packets with high overload.

  12. Stability and performance of ant queue inspired task partitioning methods.

    Science.gov (United States)

    Scheidler, Alexander; Merkle, Daniel; Middendorf, Martin

    2008-06-01

    In this paper, we consider computing systems that have autonomous helper components which fulfill support functions and that possess reconfigurable hardware so that they can specialize to different types of service tasks. Several self-organized task partitioning methods are proposed that can be used by the helper components to decide how to reconfigure and which service tasks to execute. The proposed task partitioning methods are inspired by the so-called ant queue system that can be found in real ants for partitioning tasks between the individuals. The aim of this study is to investigate basic properties of the task partitioning methods, like stability and efficiency, in order to obtain basic insights into the design of task partitioning methods in self-organized service systems. More precisely, the investigations are threefold: (1) discrete event simulations are used to investigate systems, (2) for a simple version of the task partitioning system analytical stability results are obtained by means of delay differential equation systems and (3) by numerically solving initial value problems.

  13. A queueing theory based model for business continuity in hospitals.

    Science.gov (United States)

    Miniati, R; Cecconi, G; Dori, F; Frosini, F; Iadanza, E; Biffi Gentili, G; Niccolini, F; Gusinu, R

    2013-01-01

    Clinical activities can be seen as results of precise and defined events' succession where every single phase is characterized by a waiting time which includes working duration and possible delay. Technology makes part of this process. For a proper business continuity management, planning the minimum number of devices according to the working load only is not enough. A risk analysis on the whole process should be carried out in order to define which interventions and extra purchase have to be made. Markov models and reliability engineering approaches can be used for evaluating the possible interventions and to protect the whole system from technology failures. The following paper reports a case study on the application of the proposed integrated model, including risk analysis approach and queuing theory model, for defining the proper number of device which are essential to guarantee medical activity and comply the business continuity management requirements in hospitals.

  14. Managed lanes handbook training : year 2 report of activities.

    Science.gov (United States)

    2009-02-01

    This report summarizes the Year 2 activities under Implementation Project 5-4160-01, Managed Lanes : Handbook Training. The overall objective of the project is to develop a 12-hour workshop covering The : Managed Lanes Handbook, and teach the materia...

  15. Modelling delay saving through pro-active incident management techniques

    National Research Council Canada - National Science Library

    Taylor, Nicholas B; Olstam, Johan; Bernhardsson, Viktor; Nitsche, Philippe

    2017-01-01

    Road traffic incidents cause delay, affect public safety and the environment. The CEDR PRIMA project aims to extend practical guidance for traffic managers in pro-active Traffic Incident Management (TIM...

  16. 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.

  17. Unreliable bulk retrial queues with delayed repairs and modified vacation policy

    Science.gov (United States)

    Jain, Madhu; Bhagat, Amita

    2014-06-01

    The present investigation deals with the bulk arrival M/G/1 retrial queue with impatient customers and modified vacation policy. The incoming customers join the virtual pool of customers called orbit if they find the server being busy, on vacation or in broken down state otherwise the service of the customer at the head of the batch is started by the server. The service is provided in k essential phases to all the customers by the single server which may breakdown while rendering service to the customers. The broken down server is sent to a repair facility wherein the repair is performed in d compulsory phases. As soon as the orbit becomes empty, the server goes for vacation and takes at most J vacations until at least one customer is noticed. The incoming customers are impatient and may renege on seeing a long queue of the customers for the service. The probability generating functions and queue length for the number of customers in the orbit and queue have been obtained using supplementary variable technique. Various system characteristics viz. average number of customers in the queue and the orbit, long run probabilities of the system states, etc. are obtained. Furthermore, numerical simulation has been carried out to study the sensitivity of various parameters on the system performance measures by taking an illustration.

  18. Method and apparatus for efficiently tracking queue entries relative to a timestamp

    Science.gov (United States)

    Blumrich, Matthias A.; Chen, Dong; Gara, Alan G.; Giampapa, Mark E.; Heidelberger, Philip; Ohmacht, Martin; Salapura, Velentina; Vranas, Pavlos

    2014-06-17

    An apparatus and method for tracking coherence event signals transmitted in a multiprocessor system. The apparatus comprises a coherence logic unit, each unit having a plurality of queue structures with each queue structure associated with a respective sender of event signals transmitted in the system. A timing circuit associated with a queue structure controls enqueuing and dequeuing of received coherence event signals, and, a counter tracks a number of coherence event signals remaining enqueued in the queue structure and dequeued since receipt of a timestamp signal. A counter mechanism generates an output signal indicating that all of the coherence event signals present in the queue structure at the time of receipt of the timestamp signal have been dequeued. In one embodiment, the timestamp signal is asserted at the start of a memory synchronization operation and, the output signal indicates that all coherence events present when the timestamp signal was asserted have completed. This signal can then be used as part of the completion condition for the memory synchronization operation.

  19. Propagation speed of a starting wave in a queue of pedestrians.

    Science.gov (United States)

    Tomoeda, Akiyasu; Yanagisawa, Daichi; Imamura, Takashi; Nishinari, Katsuhiro

    2012-09-01

    The propagation speed of a starting wave, which is a wave of people's successive reactions in the relaxation process of a queue, has an essential role for pedestrians and vehicles to achieve smooth movement. For example, a queue of vehicles with appropriate headway (or density) alleviates traffic jams since the delay of reaction to start is minimized. In this paper, we have investigated the fundamental relation between the propagation speed of a starting wave and the initial density by both our mathematical model built on the stochastic cellular automata and experimental measurements. Analysis of our mathematical model implies that the relation is characterized by the power law αρ-β (β≠1), and the experimental results verify this feature. Moreover, when the starting wave is characterized by the power law (β>1), we have revealed the existence of optimal density, where the required time, i.e., the sum of the waiting time until the starting wave reaches the last pedestrian in a queue and his/her travel time to pass the head position of the initial queue, is minimized. This optimal density inevitably plays a significant role in achieving a smooth movement of crowds and vehicles in a queue.

  20. Queue Content Analysis in a 2-Class Discrete-Time Queueing System under the Slot-Bound Priority Service Rule

    Directory of Open Access Journals (Sweden)

    Sofian De Clercq

    2012-01-01

    Full Text Available The paper we present here introduces a new priority mechanism in discrete-time queueing systems. It is a milder form of priority when compared to HoL priority, but it favors customers of one type over the other when compared to regular FCFS. It also provides an answer to the starvation problem that occurs in HoL priority systems. In this new priority mechanism, customers of different priority classes entering the system during the same time slot are served in order of their respective priority class—hence the name slot-bound priority. Customers entering during different slots are served on an FCFS basis. We consider two customer classes (pertaining to two levels of priority such that type-1 customers are served before type-2 customers that enter the system during the same slot. A general independent arrival process and generally distributed service times are assumed. Expressions for the probability generating function (PGF of the system content (number of type- customers, in regime are obtained using a slot-to-slot analysis. The first moments are calculated, as well as an approximation for the probability mass functions associated with the found PGFs. Lastly, some examples allow us some deeper insight into the inner workings of the slot-bound priority mechanism.

  1. The effect of varying routing probability in two parallel queues with dynamic routing under a threshold-type scheduling

    NARCIS (Netherlands)

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

    1993-01-01

    In the paper entitled "The effect of varying routing probability in two parallel queues with dynamic routing under a threshold-type scheduling", Kojima et al. derive an expression in the form of a product of powers for the state probabilities of a threshold-type shortest queue problem. In this note

  2. Timing of nurses activities: human resources management

    Directory of Open Access Journals (Sweden)

    Hamid Hosein Poor

    2016-11-01

    Full Text Available Costs of human resources include a high percentage of hospital’s costs; therefore, determination of number of real and optimal employees needed for organizations is very important. In the meantime, the optimal organization of nurses, as the biggest human resource in health care organizations, is of great importance. The present study aimed to assess the distribution of nurses’ activities in shifts and the results of productivity in human resources management in Imam Khomeini hospital in Shirvan. The present cross-sectional study was conducted in 2016. All nurses, working in three shifts of morning, afternoon, and evening in emergency unit and general units of Imam Khomeini hospital, Shirvan, were enrolled into the study through census methods. The instrument, used in this study, was the checklist of timing activities and patients’ satisfaction from nurses. The statistical software SPSS was used for analysis. Mean age of employees in these two units/wards was 31 years and mean duration of work experience was 5.24 years, The difference was significant between the two wards. necessity of the work, especially in emergency unit, are issues that need more assessment and need to be adjusted. Given the high volume of non-care matters of nursing staff, including writing services, including completing paper records and work with HIS (Hospital Information System, which has been emphasized in several studies, new definition of service and use of artificial intelligence with high efficacy is proposed. The status of the available equipment, availability, and efficiency of digital equipment and hoteling state of wards and hospitals also play an important factor in the distribution of time of nursing care activities. Employment of nurses to perform non-nursing duties, because of the shortage of other classes or lack of their permanent presence and based on Although there were differences in standard time of direct and indirect care in emergency unit and

  3. 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.

  4. 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.

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

    Directory of Open Access Journals (Sweden)

    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.

  6. Middleware for Processing Message Queues with Elasticity Support and Sequential Integrity of Asynchronous Message Processing

    Science.gov (United States)

    Henrique Teixeira, Eduardo; Patrícia Favacho de Araújo, Aletéia

    2015-10-01

    Elasticity in computing refers to dynamically adjusting the amount of allocated resources to process a distributed application. In order to achieve this, mechanisms are needed to avoid the phenomenon of the elasticity threshold detection moving constantly up or down. The existing work fails to deliver sequential integrity of asynchronous messages processing and the asymmetries of data distribution to achieve parallel consumption. This paper fills this gaps and proposes a middleware solution to dynamically analyze the flow of message queue, and a mechanism to increase the parallelized consumption based on the output behavior. An architecture for IOD (Increase On Demand) middleware is presented, with support for the increase and decrease of thread's to cope with the growth of message queues, using the technique of limit-based heuristics over a given period of time and grouping messages into sub-queues based on classification criteria.

  7. An agent-based model for queue formation of powered two-wheelers in heterogeneous traffic

    Science.gov (United States)

    Lee, Tzu-Chang; Wong, K. I.

    2016-11-01

    This paper presents an agent-based model (ABM) for simulating the queue formation of powered two-wheelers (PTWs) in heterogeneous traffic at a signalized intersection. The main novelty is that the proposed interaction rule describing the position choice behavior of PTWs when queuing in heterogeneous traffic can capture the stochastic nature of the decision making process. The interaction rule is formulated as a multinomial logit model, which is calibrated by using a microscopic traffic trajectory dataset obtained from video footage. The ABM is validated against the survey data for the vehicular trajectory patterns, queuing patterns, queue lengths, and discharge rates. The results demonstrate that the proposed model is capable of replicating the observed queue formation process for heterogeneous traffic.

  8. 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.

  9. A non-Markovian queueing system with a variable number of channels

    Directory of Open Access Journals (Sweden)

    Hong-Tham T. Rosson

    2003-01-01

    Full Text Available In this paper we study a queueing model of type GI/M/m˜a/∞ with m parallel channels, some of which may suspend their service at specified random moments of time. Whether or not this phenomenon occurs depends on the queue length. The queueing process, which we target, turns out to be semi-regenerative, and we fully explore this utilizing semi-regenerative techniques. This is contrary to the more traditional supplementary variable approach and the less popular approach of combination semi-regenerative and supplementary variable technique. We pass to the limiting distribution of the continuous time parameter process through the embedded Markov chain for which we find the invariant probability measure. All formulas are analytically tractable.

  10. 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.

  11. 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......-four hours of admission. The importance of each parameter is identified using multiple regression combined with a circular queue to iteratively fit outcome. Out of 39 parameters, the model isolated 14 which combined could estimate outcome with a root mean square error of 1.69 on the Scandinavian Stroke Scale......, where outcome for patients were 36.75 ± 10.99. The queue-based model integrating multiple linear regression shows promising results for automatic selection of significant medically relevant parameters....

  12. 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.

  13. Equilibrium Customer Strategies in the Geo/Geo/1 Queue with Single Working Vacation

    Directory of Open Access Journals (Sweden)

    Fang Wang

    2014-01-01

    Full Text Available This paper is concerned with the equilibrium balking strategies of customers in a Geo/Geo/1 queue with single working vacation. Instead of completely stopping service, the server works with a small probability during the working vacation period. As soon as no customers exist in the system, the server takes a single vacation. The customers decide for themselves whether to enter the system or balk based on a natural reward-cost structure, the information available about the status of the server, and the queue length on hand upon arrival. We obtain the equilibrium balking strategies in two cases: fully observable and fully unobservable cases, which depend on whether the customers know both the queue length and the state of the server or none of them. Finally, we present several numerical experiments that demonstrate the effect of some parameters on the equilibrium behavior.

  14. Analysis of Fuzzy Queue Characteristics by Flexible Alpha-cuts Method

    Directory of Open Access Journals (Sweden)

    J. P. Mukeba K.

    2017-03-01

    Full Text Available This article is a contribution to papers applying two kinds of fuzzy arithmetics to analyze fuzzy queues characteristics, namely, fuzzy arithmetic based on Zadeh's extension principle and fuzzy arithmetic based on alpha-cuts and intervals arithmetic. The two arithmetics being compatible, the paper shows that without reference to arithmetic based on Zadeh's extension principle, fuzzy queues characteristics can be analyzed normally by an other technique called flexible $\\alpha-cuts$ method following which all calculations are based only on alpha-cuts approach. To accomplish this task, the paper brings out all mathematical optimization programs contained in intervals arithmetic, which is one of ineluctable tools of $\\alpha-cuts$ approach, and shows how these programs are solved progressively. To illustrate this approach, the expected customer waiting time and the expected customers number in a single server fuzzy retrial queue are computed at steady state through an example in the next to last section.

  15. The M/G/1 retrial queue: New descriptors of the customer's behavior

    Science.gov (United States)

    Amador, J.; Artalejo, J. R.

    2009-01-01

    We consider queuing systems where customers are not allowed to queue; instead of that they make repeated attempts, or retrials, in order to enter service after some time. The performance of telephone systems and communication networks modelled as retrial queues differs from standard waiting lines because typically the retrial group is an invisible queue which cannot be observed. As a result, the original flow of primary arrivals and the flow of repeated attempts become undistinguished. Our aim in this paper is to consider some aspects of this problem. Thus, we focus on the main retrial model of M/G/1 type and investigate the distribution of the successful and blocked events made by the primary customers and the retrial customers.

  16. 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.

  17. Stochastic ordering properties and optimal routing control for a class of finite capacity queueing systems

    Science.gov (United States)

    Towsley, Don; Sparaggis, Panayotis D.; Cassandras, Christos G.

    1990-01-01

    The problem of routing jobs to parallel queues with identical exponential servers and unequal finite buffer capacities is considered. Stochastic ordering and weak majorization properties on critical performance measures are established by means of event-driven inductions. In particular, it is shown that the intuitive 'join the shortest non-full queue' (SNQ) policy is optimal with respect to an overall function that accounts for holding and blocking costs. Moreover, the buffer allocation problem is solved by proving the intuitive result that, for a fixed total buffer capacity, the optimal allocation scheme is the one in which the difference between the maximum and minimum queue capacities is minimized, i.e., becomes either 0 or 1.

  18. Stability condition for a multiserver retrial queue with interaction between servers and orbit

    Science.gov (United States)

    Phung-Duc, Tuan; Dragieva, Velika

    2017-07-01

    A retrial queue is characterized by the feature that an incoming call that cannot receive service immediately upon arrival joins a virtual waiting room (orbit) and retries for service in a random time. Most of models in the literature assume that the servers only serve incoming calls. Recently, Artalejo and Phung-Duc [1] study two-way communication queueing models where the server makes outgoing calls in its idle time. It is assumed in [1] that outgoing calls are independent of incoming calls in the orbit. In this paper, we relax this assumption by introducing the interaction between the servers and the orbit. In particular, we consider the case where outgoing calls may be those in the orbit. For this extended model, we establish the necessary and sufficient stability condition. It turns out that the stability condition depends on the retrial rate which is a new finding in the queueing literature.

  19. On the Discrete-Time Geo/G/1 Queue with Vacations in Random Environment

    Directory of Open Access Journals (Sweden)

    Jianjun Li

    2016-01-01

    Full Text Available A discrete-time Geo/G/1 queue with vacations in random environment is analyzed. Using the method of supplementary variable, we give the probability generating function (PGF of the stationary queue length distribution at arbitrary epoch. The PGF of the stationary sojourn time distribution is also derived. And we present the various performance measures such as mean number of customers in the system, mean length of the type-i cycle, and mean time that the system resides in phase 0. In addition, we show that the M/G/1 queue with vacations in random environment can be approximated by its discrete-time counterpart. Finally, we present some special cases of the model and numerical examples.

  20. 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.

  1. Energy saving for OpenFlow switch on the NetFPGA platform based on queue engineering.

    Science.gov (United States)

    Vu, Tran Hoang; Luc, Vu Cong; Quan, Nguyen Trung; Thanh, Nguyen Huu; Nam, Pham Ngoc

    2015-01-01

    Data centers play an important role in our daily activities. The increasing demand on data centers in both scale and size has led to huge energy consumption that rises the cost of data centers. Besides, environmental impacts also increase considerably due to a large amount of carbon emissions. In this paper, we present a design aimed at green networking by reducing the power consumption for routers and switches. Firstly, we design the Balance Switch on the NetFPGA platform to save consumed energy based on Queue Engineering. Secondly, we design the test-bed system to precisely measure the consumed energy of our switches. Experimental results show that energy saving of our switches is about 30% - 35% of power consumption according to variation of input traffic compared with normal Openflow Switch. Finally, we describe performance evaluations.

  2. The CMS workload management system

    Energy Technology Data Exchange (ETDEWEB)

    Cinquilli, M. [CERN; Evans, D. [Fermilab; Foulkes, S. [Fermilab; Hufnagel, D. [Fermilab; Mascheroni, M. [CERN; Norman, M. [UC, San Diego; Maxa, Z. [Caltech; Melo, A. [Vanderbilt U.; Metson, S. [Bristol U.; Riahi, H. [INFN, Perugia; Ryu, S. [Fermilab; Spiga, D. [CERN; Vaandering, E. [Fermilab; Wakefield, Stuart [Imperial Coll., London; Wilkinson, R. [Caltech

    2012-01-01

    CMS has started the process of rolling out a new workload management system. This system is currently used for reprocessing and Monte Carlo production with tests under way using it for user analysis. It was decided to combine, as much as possible, the production/processing, analysis and T0 codebases so as to reduce duplicated functionality and make best use of limited developer and testing resources. This system now includes central request submission and management (Request Manager), a task queue for parcelling up and distributing work (WorkQueue) and agents which process requests by interfacing with disparate batch and storage resources (WMAgent).

  3. 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....

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

    Directory of Open Access Journals (Sweden)

    Zhanyou Ma

    2013-01-01

    Full Text Available 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, we analyze the effect of some related parameters on the system performance measures.

  5. 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.

  6. Some Estimation Approaches of Intensities for a Two Stage Open Queueing Network

    Directory of Open Access Journals (Sweden)

    Suresh B Pathare

    2014-02-01

    Full Text Available In this paper we propose a consistent and asymptotically normal estimator (CAN for intensity parameters for a queueing network with distribution-free inter-arrival and service times. Using this estimator and its estimated variance, some asymptotic confidence interval of intensities are constructed. Exact- t, Bootstrap-t, Variance-stabilized bootstrap-t, Standard bootstrap, Bayesian bootstrap, Percentile bootstrap and Bias-corrected and accelerated bootstrap are also applied to develop the confidence intervals of intensities.  A comparative analysis is conducted to demonstrate performances of the confidence intervals of intensities for a queueing network with short run.

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

    Directory of Open Access Journals (Sweden)

    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.

  8. Performance Study of OBS Combined Node via Mixed Loss Delay Queueing Systems

    Directory of Open Access Journals (Sweden)

    Muhammad Faisal Hayat

    2014-01-01

    Full Text Available In this paper, we present a performance study of OBS (Optical Burst Switched combined node via mixed loss delay queueing models. In an OBS network, a node combining both edge and core switching functions multiplex the local traffic with the transit traffic on the output wavelengths channels. To control the channel sharing, strategies are proposed and analyzed in this study by extending the basic mixed loss delay queueing models. The presented models are solved by Markov chain techniques and the results are compared, and where necessary also supported, by the simulations of an OBS node implemented in detail

  9. 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.

  10. The Application of The Double Queue Asymmetric Gated Service Polling Control Theory in Intelligent Traffic System

    OpenAIRE

    Zhao Yi Fan; Ding Hong Wei; Wang Meng Yao; Liang Zhu Guan

    2016-01-01

    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 t...

  11. On the Use of Second-Order Descriptors To Predict Queueing Behavior of MAPs

    DEFF Research Database (Denmark)

    Andersen, Allan T.; Nielsen, Bo Friis

    2002-01-01

    The contributions of this paper are the following: We derive a formula for the IDI (Index of Dispersion for Intervals) for the Markovian Arrival Process (MAP). We show that two-state MAPs with identical fundamental rate, IDI and IDC (Index of Dispersion for Counts), define interval stationary point...... stationary and time stationary behavior of the two-state model. We give various illustrative numerical examples on the merits in predicting queueing behavior on the basis of first- and second-order descriptors by considering queueing behavior of MAPs with constant fundamental rate and IDC, respectively...

  12. 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.

  13. Performance evaluation of an M/G/n-type queue with bounded capacity and packet dropping

    Directory of Open Access Journals (Sweden)

    Tikhonenko Oleg

    2016-12-01

    Full Text Available A queueing system of the M/G/n-type, n ≥ 1, with a bounded total volume is considered. It is assumed that the volumes of the arriving packets are generally distributed random variables. Moreover, the AQM-type mechanism is used to control the actual buffer state: each of the arriving packets is dropped with a probability depending on its volume and the occupied volume of the system at the pre-arrival epoch. The explicit formulae for the stationary queue-size distribution and the loss probability are found. Numerical examples illustrating theoretical formulae are given as well.

  14. Reservicing some customers in M/G/1 queues under three disciplines

    Directory of Open Access Journals (Sweden)

    M. R. Salehi-Rad

    2004-01-01

    Full Text Available Consider an M/G/1 production line in which a production item is failed with some probability and is then repaired. We consider three repair disciplines depending on whether the failed item is repaired immediately or first stockpiled and repaired after all customers in the main queue are served or the stockpile reaches a specified threshold. For each discipline, we find the probability generating function (p.g.f. of the steady-state size of the system at the moment of departure of the customer in the main queue, the mean busy period, and the probability of the idle period.

  15. Activity: Managing an 80-Acre School Forest.

    Science.gov (United States)

    EE News: Environmental Education in Wisconsin, 1996

    1996-01-01

    Students play the role of members serving on a Wisconsin school forest advisory committee. Through these roles students begin to explore and understand the complex considerations that influence the management of an imaginary school forest, including both educational and forest management needs. Analytical, problem-solving, and consensus-building…

  16. A Study on improvement of comprehensive environmental management system - activation of liberalized environmental management

    Energy Technology Data Exchange (ETDEWEB)

    Chung, Hweu Sung; Kang, Chul Goo [Korea Environment Institute, Seoul (Korea)

    1998-12-01

    As a part of improvement on a comprehensive environmental management system, this study was attempted to find an activating policy for a liberalized environmental management. This study provided an activation plan of reasonable environmental regulation reform and liberalized environmental management through the analysis of foreign examples and domestic situation. Furthermore, it analyzed an institutional mechanism for a smooth operation of liberalized environmental management. 68 refs., 5 figs., 51 tabs.

  17. PSYCHOLOGICAL PECULIARITIES OF CREATIVITY MANIFESTATION IN ACTIVITIES OF MANAGERS

    Directory of Open Access Journals (Sweden)

    A R Akimova

    2016-12-01

    Full Text Available The modern economic, political and cultural situation in Russia calls for a new generation of managers, creative in their activities. In this regard we need to develop in them the personal qualities and characteristics which will enable them to achieve personal and professional success in various spheres of life. The article is devoted to studying features of ingenuity manifestation in managers as a systemic property of the personality. The features of creative activity, strategies for achieving goals, planning and time management in managers were analyzed in the article. The correlations of motivational, productive, dynamic and emotional sides of the personality traits of ingenuity, individual strategies of achieving goals and signs of time pressure in solving professional tasks for managers were considered. The practical recommendations developed in the study can significantly optimize the psychological support for managers, concerning the conditions of effective strategies for achieving goals, planning and time management, as the most important factors for their successful professional activity.

  18. A New Activity-Based Financial Cost Management Method

    Science.gov (United States)

    Qingge, Zhang

    The standard activity-based financial cost management model is a new model of financial cost management, which is on the basis of the standard cost system and the activity-based cost and integrates the advantages of the two. It is a new model of financial cost management with more accurate and more adequate cost information by taking the R&D expenses as the accounting starting point and after-sale service expenses as the terminal point and covering the whole producing and operating process and the whole activities chain and value chain aiming at serving the internal management and decision.

  19. 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.

  20. US - Former Soviet Union environmental management activities

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1995-09-01

    The Office of Environmental Management (EM) has been delegated the responsibility for US DOE`s cleanup of nuclear weapons complex. The nature and the magnitude of the waste management and environmental remediation problem requires the identification of technologies and scientific expertise from domestic and foreign sources. This booklet makes comparisons and describes coordinated projects and workshops between the USA and the former Soviet Union.

  1. Management of Logistics Activities and Costing Approaches

    National Research Council Canada - National Science Library

    İlker KIYMETLİ ŞEN

    2014-01-01

    ..., and the shortening of product life cycles. As a result of globalization, costs of logistics activities have also increased depending on changes in the quality and quantity of logistics activities...

  2. Quarterly Briefing Book on Environmental and Waste Management Activities

    Energy Technology Data Exchange (ETDEWEB)

    Brown, M.C.

    1991-06-01

    The purpose of the Quarterly Briefing Book on Environmental and Waste Management Activities is to provide managers and senior staff at the US Department of Energy-Richland Operations Office and its contractors with timely and concise information on Hanford Site environmental and waste management activities. Each edition updates the information on the topics in the previous edition, deletes those determined not to be of current interest, and adds new topics to keep up to date with changing environmental and waste management requirements and issues. Section A covers current waste management and environmental restoration issues. In Section B are writeups on national or site-wide environmental and waste management topics. Section C has writeups on program- and waste-specific environmental and waste management topics. Section D provides information on waste sites and inventories on the site. 15 figs., 4 tabs.

  3. 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

  4. Fast simulation of overflow probabilities in a queue with Gaussian input

    NARCIS (Netherlands)

    A.B. Dieker (Ton); M.R.H. Mandjes (Michel)

    2004-01-01

    textabstractIn this paper, we study a queue fed by a large number $n$ of independent discrete-time Gaussian processes with stationary increments. We consider the {it many sources} asymptotic regime, i.e., the buffer exceedance threshold $B$ and the service capacity $C$ are scaled by the number of

  5. Impacts Assessment of Dynamic Speed Harmonization with Queue Warning : Task 3, Impacts Assessment Report. [supporting datasets

    Science.gov (United States)

    2015-05-31

    The datasets in the .pdf and .zip attached to this record are in support of Intelligent Transportation Systems Joint Program Office (ITS JPO) report FHWA-JPO-15-222, "Impacts Assessment of Dynamic Speed Harmonization with Queue Warning : Task 3, Impa...

  6. Fast simulation of overflow probabilities in a queue with Gaussian input

    NARCIS (Netherlands)

    Dieker, A.B.; Mandjes, M.R.H.

    2006-01-01

    In this article, we study a queue fed by a large number n of independent discrete-time Gaussian processes with stationary increments. We consider the many-sources asymptotic regime, that is, the buffer-exceedance threshold B and the service capacity C are scaled by the number of sources (B ≡ nb and

  7. Fluid models for many-server Markovian queues in a changing environment.

    NARCIS (Netherlands)

    Zhang, B.; Zwart, A.P.

    2012-01-01

    Motivated by service systems with time-varying customer arrivals, we consider a fluid model as a macroscopic approximation for many-server Markovian queues alternating between underloaded and overloaded intervals. Our main result is a refinement of the piecewise stationary approximation (PSA) for

  8. Optimization of the service strategy in a queueing system with energy harvesting and customers’ impatience

    National Research Council Canada - National Science Library

    Alexander Dudin; Moon Ho Lee; Sergey Dudin

    2016-01-01

    A single-server queueing system with an infinite buffer is considered. The service of a customer is possible only in the presence of at least one unit of energy, and during the service the number of available units decreases by one...

  9. 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.

  10. A functional central limit theorem for Markov additive arrival processes and its applications to queueing systems

    NARCIS (Netherlands)

    Lu, H.; Pang, G.; Mandjes, M.

    2016-01-01

    We prove a functional central limit theorem for Markov additive arrival processes where the modulating Markov process has the transition rate matrix scaled up by nα(α>0) and the mean and variance of the arrival process are scaled up by n. It is applied to an infinite-server queue and a fork–join

  11. On stability of queueing models for local area networks with slotted ring protocols

    NARCIS (Netherlands)

    van Arem, B.; van Arem, Bart

    1990-01-01

    A study is made of a queueing system which is intended to model local area networks with slotted ring protocols and which generalizes some previously studied models. The author defines a special type of stability, called ¿-stability, which is related to the slot rotation time ¿. The author also

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

    Directory of Open Access Journals (Sweden)

    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.

  13. 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

  14. 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

  15. Analysis of discrete-time queue for broadband ISDN with priorities among traffic classes

    Science.gov (United States)

    Takine, Tetsuya; Sengupta, Bhaskar; Hasegawa, Toshiharu

    1994-02-01

    In Broadband ISDN (Integrated Service Digital Network), different classes of traffic expect to receive different quality of service. One way of providing service is to implement a priority structure among traffic classes. We analyze a single server queue in which video and voice traffic receive priority over data traffic.

  16. The stationary local sojourn time in single server tandem queues with renewal input

    Directory of Open Access Journals (Sweden)

    Pierre Le Gall

    1999-01-01

    Full Text Available We start from an earlier paper evaluating the overall sojourn time to derive the local sojourn time in stationary regime, in a single server tandem queue of (m+1 stages with renewal input. The successive service times of a customer may or may not be mutually dependent, and are governed by a general distribution which may be different at each sage.

  17. Stochastic Approximations and Monotonicity of a Single Server Feedback Retrial Queue

    Directory of Open Access Journals (Sweden)

    Mohamed Boualem

    2012-01-01

    Full Text Available This paper focuses on stochastic comparison of the Markov chains to derive some qualitative approximations for an M/G/1 retrial queue with a Bernoulli feedback. The main objective is to use stochastic ordering techniques to establish various monotonicity results with respect to arrival rates, service time distributions, and retrial parameters.

  18. A Single Server Retrial Queue with Different Types of Server Interruptions

    OpenAIRE

    Kernane, Tewfik

    2009-01-01

    We consider a single server retrial queue with the server subject to interruptions and classical retrial policy for the access from the orbit to the server. We analyze the equilibrium distribution of the system and obtain the generating functions of the limiting distribution.

  19. Simple Product-Form Bounds for Queueing Networks with Finite Clusters

    NARCIS (Netherlands)

    van Dijk, N.M.; van der Sluis, H.J.

    2002-01-01

    Queueing networks are studied with finite capacities for clusters of stations, rather than for individual stations. First, an instructive tandem cluster example is studied to show that a product-form modification method for networks with finite stations can be extended to networks with finite

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

    National Research Council Canada - National Science Library

    Lee, Doo Ho; Kim, Kilhwan

    2014-01-01

    ... systems with negative customers due to their applications to neural networks, communication systems, and manufacturing systems. If a negative customer arrives at a queueing system, it removes one ordinary customer (called a positive customer) according to a predetermined removal discipline. There are two typical removal disciplines: (i) a ne...

  1. Large Deviations Methods and the Join-the-Shortest-Queue Model

    NARCIS (Netherlands)

    Ridder, Ad; Shwartz, Adam

    2005-01-01

    We develop a methodology for studying ''large deviations type'' questions. Our approach does not require that the large deviations principle holds, and is thus applicable to a larg class of systems. We study a system of queues with exponential servers, which share an arrival stream. Arrivals are

  2. Modelling M/G/1 queueing systems with server vacations using ...

    African Journals Online (AJOL)

    The theory of non-Markovian stochastic Petri nets is employed in this paper to derive an alternative method for studying the steady state behaviour of the M/G/1 vacation queueing system with a limited service discipline. Three types of vacation schemes are considered, and sytems with both a finite population and those with ...

  3. A closed-form solution for a two-server heterogeneous retrial queue ...

    Indian Academy of Sciences (India)

    In this paper, we reconsider a two-server heterogeneous retrial queue with threshold policy. However ... Division of Knowledge and System Engineering for ICT, Faculty of Information Technology, Ton Duc Thang University, Ho Chi Minh City, Vietnam; Department of Networked Systems and Services, Budapest University of ...

  4. 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 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 suggested....

  5. 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...

  6. Joint queue-perturbed and weakly-coupled power control for wireless backbone networks

    CSIR Research Space (South Africa)

    Olwal, TO

    2012-09-01

    Full Text Available Wireless Backbone Networks (WBNs) equipped with Multi-Radio Multi-Channel (MRMC) configurations do experience power control problems such as inter-channel and co-channel interference, high energy consumption at the multiple queues and unscalable...

  7. Improving Adaptive Importance Sampling Simulation of Markovian Queueing Models using Non-parametric Smoothing

    NARCIS (Netherlands)

    Woudt, Edwin; de Boer, Pieter-Tjerk; van Ommeren, Jan C.W.

    2007-01-01

    Previous work on state-dependent adaptive importance sampling techniques for the simulation of rare events in Markovian queueing models used either no smoothing or a parametric smoothing technique, which was known to be non-optimal. In this paper, we introduce the use of kernel smoothing in this

  8. Iterative method of analysis of single queue, multi-server with limited ...

    African Journals Online (AJOL)

    In this paper, analysis of single queue, multi-server with limited system capacity under first come first served discipline was carried out using iterative method. The arrivals of customers and service times of customers are assumed poisson and exponential distributions respectively. This queuing model is an extension of ...

  9. A solvable queueing network model for railway networks and its validation and applications for the Netherlands

    NARCIS (Netherlands)

    Huisman, Tijs; Boucherie, Richardus J.; van Dijk, N.M.

    2002-01-01

    The performance of new railway networks cannot be measured or simulated, as no detailed train schedules are available. Railway infrastructure and capacities are to be determined long before the actual traffic is known. This paper therefore proposes a solvable queueing network model to compute

  10. A Discrete-Time Queue with Preferred Customers and Partial Buffer Sharing

    Directory of Open Access Journals (Sweden)

    Shizhong Zhou

    2015-01-01

    Full Text Available We analyze a discrete-time Geo/Geo/1 queueing system with preferred customers and partial buffer sharing. In this model, customers arrive according to geometrical arrival processes with probability λ. If an arriving customer finds the server idle, he begins instantly his services. Otherwise, if the server is busy at the arrival epoch, the arrival either interrupts the customer being served to commence his own service with probability θ (the customer is called the preferred customer or joins the waiting line at the back of the queue with probability θ~ (the customer is called the normal customer if permitted. The interrupted customer joins the waiting line at the head of the queue. If the total number of customers in the system is equal to or more than threshold N, the normal customer will be ignored to enter into the system. But this restriction is not suitable for the preferred customers; that is, this system never loses preferred customers. A necessary and sufficient condition for the system to be stable is investigated and the stationary distribution of the queue length of the system is also obtained. Further, we develop a novel method to solve the probability generating function of the busy period of the system. The distribution of sojourn time of a customer in the server and the other indexes are acquired as well.

  11. 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

  12. Analyzing multi-class, multi-server queueing systems with preemtive priorities

    NARCIS (Netherlands)

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

    2002-01-01

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

  13. Adaptive state-dependent importance sampling simulation of Markovian queueing networks

    NARCIS (Netherlands)

    de Boer, Pieter-Tjerk; Nicola, V.F.

    2002-01-01

    In this paper, a method is presented for the efficient estimation of rare-event (buffer overflow) probabilities in queueing networks using importance sampling. Unlike previously proposed change of measures, the one used here is not static, i.e., it depends on the buffer contents at each of the

  14. Dynamic properties of chasers in a moving queue based on a delayed chasing model

    Science.gov (United States)

    Ning, Guo; Jian-Xun, Ding; Xiang, Ling; Qin, Shi; Reinhart, Kühne

    2016-05-01

    A delayed chasing model is proposed to simulate the chase behavior in the queue, where each member regards the closest one ahead as the target, and the leader is attracted to a target point with slight fluctuation. When the initial distances between neighbors possess an identical low value, the fluctuating target of the leader can cause an amplified disturbance in the queue. After a long period of time, the queue recovers the stable state from the disturbance, forming a straight-line-like pattern again, but distances between neighbors grow. Whether the queue can keep stable or not depends on initial distance, desired velocity, and relaxation time. Furthermore, we carry out convergence analysis to explain the divergence transformation behavior and confirm the convergence conditions, which is in approximate agreement with simulations. Project supported by the National Natural Science Foundation of China (Grant Nos. 71071044, 71001001, 71201041, and 11247291), the Doctoral Program of the Ministry of Education of China (Grant Nos. 20110111120023 and 20120111120022), the Postdoctoral Fund Project of China (Grant No. 2013M530295), the National Basic Research Program of China (Grant No. 2012CB725404), and 1000 Plan for Foreign Talent, China (Grant No. WQ20123400070).

  15. 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.

  16. 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.

  17. 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.

  18. A queueing-theoretic analysis of the threshold-based exhaustive data-backup scheduling policy

    Science.gov (United States)

    Claeys, Dieter; Dorsman, Jan-Pieter; Saxena, Apoorv; Walraevens, Joris; Bruneel, Herwig

    2017-07-01

    We analyse the threshold-based exhaustive data backup scheduling mechanism by means of a queueing-theoretic approach. Data packets that have not yet been backed up are modelled by customers waiting for service (back-up). We obtain the probability generating function of the system content (backlog size) at random slot boundaries in steady state.

  19. DATADRAW: A Command Language for Manipulating and Displaying Stacks, Queues, Lists and Trees.

    Science.gov (United States)

    Siklossy, L.; And Others

    DATADRAW is a command language, written in FORTRAN IV, to manipulate stacks, queues, lists and trees, and to display them on the CDC 252 scope system attached to a CDC 6600. A DATADRAW primer is given, and the algorithms for updating and displaying structures are described. It is noted that DATADRAW was designed to be a simple command language…

  20. 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

  1. Transient analysis of an M/M/1 queue with multiple vacations

    National Research Council Canada - National Science Library

    Kaliappan Kalidass; Kasturi Ramanath

    2014-01-01

    ...; mso-fareast-language: EN-US; mso-bidi-language: AR-SA; mso-no-proof: yes;">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...

  2. Simulating Tail Probabilities in GI/GI.1 Queues and Insurance Risk Processes with Subexponentail Distributions

    NARCIS (Netherlands)

    Boots, Nam Kyoo; Shahabuddin, Perwez

    2001-01-01

    This paper deals with estimating small tail probabilities of thesteady-state waiting time in a GI/GI/1 queue with heavy-tailed (subexponential) service times. The problem of estimating infinite horizon ruin probabilities in insurance risk processes with heavy-tailed claims can be transformed into

  3. International Project Management Committee: Overview and Activities

    Science.gov (United States)

    Hoffman, Edward

    2010-01-01

    This slide presentation discusses the purpose and composition of the International Project Management Committee (IMPC). The IMPC was established by members of 15 space agencies, companies and professional organizations. The goal of the committee is to establish a means to share experiences and best practices with space project/program management practitioners at the global level. The space agencies that are involved are: AEB, DLR, ESA, ISRO, JAXA, KARI, and NASA. The industrial and professional organizational members are Comau, COSPAR, PMI, and Thales Alenia Space.

  4. Medication management activities performed by informal caregivers of older adults.

    Science.gov (United States)

    Look, Kevin A; Stone, Jamie A

    2017-05-16

    Medication management is commonly performed by informal caregivers, yet they are often unprepared and ill-equipped to manage complex medication regimens for their older adult care recipients. In order to develop interventions that will enhance the caregiver's ability to safely and confidently manage medications, it is critical to first understand caregiver challenges and unmet needs related to medication management. To explore how informal caregivers manage medications for their older adult care recipients by identifying the activities involved in medication management and the tools or strategies used to facilitate these activities. Four focus groups with caregivers of older adults were conducted with 5-9 caregivers per group. Participants were asked to describe the medication management activities performed and the tools or strategies used to facilitate these activities. Focus groups were recorded, transcribed verbatim, and analyzed for themes using an inductive approach. Caregivers were commonly involved in 2 types of activities: direct activities requiring physical handling of medications such as obtaining medications, preparing pill boxes, and assisting with medication administration; and indirect activities that were more complex and required more of a cognitive effort by the caregiver, such as organizing and tracking medications, gathering information, and making treatment decisions. They utilized a variety of tools and strategies to support these medication management activities; however, these approaches often needed to be modified or personalized to meet the specific needs of their caregiving situation. Informal caregivers play a vital role in ensuring safe and appropriate medication use by older adults. Medication management is complex and involves many activities that are supported through the use of a variety of tools and strategies that have been adapted and individualized to each specific caregiving scenario. Caregivers should be an important

  5. Active management of labor: does it make a difference?

    Science.gov (United States)

    Rogers, R; Gilson, G J; Miller, A C; Izquierdo, L E; Curet, L B; Qualls, C R

    1997-09-01

    Our goal was to evaluate whether active management of labor lowers cesarean section rates, shortens the length of labor, and overcomes any negative effects of epidural analgesia on nulliparous labor. We randomly assigned 405 low-risk term nulliparous patients to either an active management of labor (n = 200) or our usual care control protocol (n = 205). Patients who were undergoing active management of labor were diagnosed as being in labor on the basis of having painful palpable contractions accompanied by 80% cervical effacement, underwent early amniotomy, and were treated with high-dose oxytocin for failure to progress adequately in labor. The cesarean section rate in the active management of labor group was lower than that of controls but not significantly so (active management, 7.5%; controls, 11.7%; p = 0.36). The length of labor in the active management group was shortened by 1.7 hours (from 11.4 to 9.7 hours, p = 0.001). Fifty-five percent of patients received epidural analgesics; a reduction in length of labor persisted despite the use of epidural analgesics (active management 11.2 hours vs control 13.3 hours, p = 0.001). A significantly greater proportion of active management patients were delivered by 12 hours compared with controls (75% vs 58%, p = 0.01); this difference also persisted despite the use of epidural analgesics (66% vs 51%, p = 0.03). Patients undergoing active management had shortened labors and were more likely to be delivered within 12 hours, differences that persisted despite the use of epidural analgesics. There was a trend toward a reduced rate of cesarean section.

  6. Pathogen transfer through environment-host contact: an agent-based queueing theoretic framework.

    Science.gov (United States)

    Chen, Shi; Lenhart, Suzanne; Day, Judy D; Lee, Chihoon; Dulin, Michael; Lanzas, Cristina

    2017-11-02

    Queueing theory studies the properties of waiting queues and has been applied to investigate direct host-to-host transmitted disease dynamics, but its potential in modelling environmentally transmitted pathogens has not been fully explored. In this study, we provide a flexible and customizable queueing theory modelling framework with three major subroutines to study the in-hospital contact processes between environments and hosts and potential nosocomial pathogen transfer, where environments are servers and hosts are customers. Two types of servers with different parameters but the same utilization are investigated. We consider various forms of transfer functions that map contact duration to the amount of pathogen transfer based on existing literature. We propose a case study of simulated in-hospital contact processes and apply stochastic queues to analyse the amount of pathogen transfer under different transfer functions, and assume that pathogen amount decreases during the inter-arrival time. Different host behaviour (feedback and non-feedback) as well as initial pathogen distribution (whether in environment and/or in hosts) are also considered and simulated. We assess pathogen transfer and circulation under these various conditions and highlight the importance of the nonlinear interactions among contact processes, transfer functions and pathogen demography during the contact process. Our modelling framework can be readily extended to more complicated queueing networks to simulate more realistic situations by adjusting parameters such as the number and type of servers and customers, and adding extra subroutines. © The authors 2017. Published by Oxford University Press on behalf of the Institute of Mathematics and its Applications. All rights reserved.

  7. 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

    2013-01-01

    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

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

    Directory of Open Access Journals (Sweden)

    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.

  9. 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

  10. SOCIAL ORIENTATION MANAGEMENT OF COMMERCIAL BANKS ACTIVITY

    Directory of Open Access Journals (Sweden)

    N. G. Shpankovskaya

    2010-06-01

    Full Text Available The modern theoretical approaches to definition of essence of social activity of enterprises are analyzed. The directions of development of social activity of commercial banks are determined. The expedience of formulation of mission of commercial banks and general requirements it must meet to is grounded.

  11. Anthropogenic Activities Threatening the Management of ...

    African Journals Online (AJOL)

    Abundant fauna and flora resources in Nigeria are being threatened due to the increasing rate of anthropogenic activities across the protected areas in the country. This study examined anthropogenic activities threatening the natural resources considered to be of ecotourism value in Old Oyo National Park. Primary data ...

  12. Nonexercise activity thermogenesis in obesity management.

    Science.gov (United States)

    Villablanca, Pedro A; Alegria, Jorge R; Mookadam, Farouk; Holmes, David R; Wright, R Scott; Levine, James A

    2015-04-01

    Obesity is linked to cardiovascular disease. The global increase in sedentary lifestyle is an important factor contributing to the rising prevalence of the obesity epidemic. Traditionally, counseling has focused on moderate- to vigorous-intensity exercise, with disappointing results. Nonexercise activity thermogenesis (NEAT) is an important component of daily energy expenditure. It represents the common daily activities, such as fidgeting, walking, and standing. These high-effect NEAT movements could result in up to an extra 2000 kcal of expenditure per day beyond the basal metabolic rate, depending on body weight and level of activity. Implementing NEAT during leisure-time and occupational activities could be essential to maintaining a negative energy balance. NEAT can be applied by being upright, ambulating, and redesigning workplace and leisure-time environments to promote NEAT. The benefits of NEAT include not only the extra calories expended but also the reduced occurrence of the metabolic syndrome, cardiovascular events, and all-cause mortality. We believe that to overcome the obesity epidemic and its adverse cardiovascular consequences, NEAT should be part of the current medical recommendations. The content of this review is based on a literature search of PubMed and the Google search engine between January 1, 1960, and October 1, 2014, using the search terms physical activity, obesity, energy expenditure, nonexercise activity thermogenesis, and NEAT. Copyright © 2015 Mayo Foundation for Medical Education and Research. Published by Elsevier Inc. All rights reserved.

  13. Analysis of information systems for the enterprises marketing activities management

    OpenAIRE

    A.O. Natorina

    2014-01-01

    The article deals with the role of the computer information systems in the enterprise marketing activities strategic management, enterprises marketing management information systems. Tthe stages of the development system and launch of a new product into the market within its life cycle are analyzed, exemplified by fat and oil industry.

  14. Pro-active Management of Traffic Incidents Using Novel Technologies

    NARCIS (Netherlands)

    Nitsche, P.; Olstam, J.; Taylor, N.; Reinthaler, M.; Ponweiser, W.; Bernhardsson, V.; Mocanu, I.; Uittenbogaard, J.; Dam, E. van

    2016-01-01

    This paper presents the results of the assessment phase of the project PRIMA (Pro-Active Incident Management), where the benefits, costs and risks of novel traffic incident management techniques are investigated. The project targets the enhancement of current state-of-the-art measures for handling

  15. Effectiveness of marketing in management marketing activity agricultural companies

    OpenAIRE

    KUCHER O.

    2012-01-01

    Modern approaches to evaluating the effectiveness of marketing activity are investigated. The influence of marketing expenses on actualization volume of output is analyzed. A methodical approach of defining economic efficiency in marketing sales in management business is offered.

  16. Preliminary Tritium Management Design Activities at ORNL

    Energy Technology Data Exchange (ETDEWEB)

    Harrison, Thomas J. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Felde, David K. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Logsdon, Randall J. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); McFarlane, Joanna [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Qualls, A. L. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2016-09-01

    Interest in salt-cooled and salt-fueled reactors has increased over the last decade (Forsberg et al. 2016). Several private companies and universities in the United States, as well as governments in other countries, are developing salt reactor designs and/or technology. Two primary issues for the development and deployment of many salt reactor concepts are (1) the prevention of tritium generation and (2) the management of tritium to prevent release to the environment. In 2016, the US Department of Energy (DOE) initiated a research project under the Advanced Reactor Technology Program to (1) experimentally assess the feasibility of proposed methods for tritium mitigation and (2) to perform an engineering demonstration of the most promising methods. This document describes results from the first year’s efforts to define, design, and build an experimental apparatus to test potential methods for tritium management. These efforts are focused on producing a final design document as the basis for the apparatus and its scheduled completion consistent with available budget and approvals for facility use.

  17. Management Control of Public and Not-for-Profit Activities

    OpenAIRE

    Hofstede, G.

    1981-01-01

    Traditional approaches to management control usually fail for public and not-for-profit activities. The type of control applicable to such activities depends on four criteria: are objectives unambiguous, outputs measurable, effects of interventions known, and is the activity repetitive? Depending on where activities stand with regard to these criteria, the control applicable corresponds to one of six different types: routine, expert, trial-and-error, intuitive, judgemental, or political contr...

  18. 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.

  19. Buffer management in wireless full-duplex systems

    KAUST Repository

    Bouacida, Nader

    2015-10-19

    Wireless full-duplex radios can simultaneously transmit and receive using the same frequency. In theory, this can double the throughput. In fact, there is only little work addressing aspects other than throughput gains in full-duplex systems. Over-buffering in today\\'s networks or the so-called “bufferbloat” phenomenon creates excessive end-to-end delays resulting in network performance degradation. Our analysis shows that full-duplex systems may suffer from high latency caused by bloated buffers. In this paper, we address the problem of buffer management in full-duplex networks by using Wireless Queue Management (WQM), which is an active queue management technique for wireless networks. Our solution is based on Relay Full-Duplex MAC (RFD-MAC), an asynchronous media access control protocol designed for relay full-duplexing. We compare the performance of WQM in full-duplex environment to Drop Tail mechanism over various scenarios. Our solution reduces the end-to-end delay by two orders of magnitude while achieving similar throughput in most of the cases.

  20. Management information systems for environmental compliance activities

    Energy Technology Data Exchange (ETDEWEB)

    1990-04-23

    The Department of Energy (DOE) is subject to Federal and state laws designed to protect against threats to public health and the environment. The purpose of this audit was to determine whether the Department had developed adequate information systems for tracking and reporting on the status of its compliance with these laws. Systems used for prioritizing and budgeting for environmental activities are being addressed in a separate review.

  1. Current Management Strategy for Active Surveillance in Prostate Cancer.

    Science.gov (United States)

    Syed, Jamil S; Javier-Desloges, Juan; Tatzel, Stephanie; Bhagat, Ansh; Nguyen, Kevin A; Hwang, Kevin; Kim, Sarah; Sprenkle, Preston C

    2017-02-01

    Active surveillance has been increasingly utilized as a strategy for the management of favorable-risk, localized prostate cancer. In this review, we describe contemporary management strategies of active surveillance, with a focus on traditional stratification schemes, new prognostic tools, and patient outcomes. Patient selection, follow-up strategy, and indication for delayed intervention for active surveillance remain centered around PSA, digital rectal exam, and biopsy findings. Novel tools which include imaging, biomarkers, and genetic assays have been investigated as potential prognostic adjuncts; however, their role in active surveillance remains institutionally dependent. Although 30-50% of patients on active surveillance ultimately undergo delayed treatment, the vast majority will remain free of metastasis with a low risk of dying from prostate cancer. The optimal method for patient selection into active surveillance is unknown; however, cancer-specific mortality rates remain excellent. New prognostication tools are promising, and long-term prospective, randomized data regarding their use in active surveillance will be beneficial.

  2. KNOWLEDGE MANAGEMENT FOR MAINTENANCE ACTIVITIES IN THE MANUFACTURING SECTOR

    Directory of Open Access Journals (Sweden)

    M.A. Mansor

    2012-06-01

    Full Text Available Maintenance is an indispensable part of the business process and plays an important role in an organisation’s success and survival. The main purpose of maintenance is to ensure equipment functions at its original optimal level. Thus, the knowledge and skills of operators are crucial and in demand. This paper presents a knowledge management of maintenance activities transfer method. Knowledge management is a process that a company cannot avoid, because it is a step in providing the necessary information for business performance measurements. Based on the example of a knowledge management system for a consultant company, we propose a knowledge repository or warehouse for maintenance activities that consists of four elements: best practice, databases, discussion forums and assessment tools. Each element has its own role and contribution towards better maintenance activities. Therefore, knowledge management has a deep relationship with performance evaluation or measurement.

  3. University Knowledge Management Tool for Academic Research Activity Evaluation

    Directory of Open Access Journals (Sweden)

    Mihaela OPREA

    2011-01-01

    Full Text Available The implementation of an efficient university knowledge management system involves the de-velopment of several software tools that assist the decision making process for the three main activities of a university: teaching, research, and management. Artificial intelligence provides a variety of techniques that can be used by such tools: machine learning, data mining, text mining, knowledge based systems, expert systems, case-based reasoning, decision support systems, intelligent agents etc. In this paper it is proposed a generic structure of a university knowledge management system, and it is presented an expert system, ACDI_UPG, developed for academic research activity evaluation, that can be used as a decision support tool by the university knowledge management system for planning future research activities according to the main objectives of the university and of the national / international academic research funding organizations.

  4. Network management systems for active distribution networks. A feasibility study

    Energy Technology Data Exchange (ETDEWEB)

    Roberts, D.A.

    2004-07-01

    A technical feasibility study on network management systems for active distribution networks is reported. The study investigated the potential for modifying a Distribution Network Operator (DNO) Supervisory Control and Data Acquisition System (SCADA) to give some degree of active management. Government incentives have encouraged more and more embedded generation being connected to the UK distribution networks and further acceleration of the process should support the 2010 target for a reduction in emissions of carbon dioxide. The report lists the objectives of the study and summarises what has been achieved; it also discusses limitations, reliability and resilience of existing SCADA. Safety and operational communications are discussed under staff safety and operational safety. Recommendations that could facilitate active management through SCADA are listed, together with suggestions for further study. The work was carried out as part of the DTI New and Renewable Energy Programme managed by Future Energy Solutions.

  5. Short communication: Biochemically active humic substances in contrasting agricultural managements

    Energy Technology Data Exchange (ETDEWEB)

    Benitez, E.; Nogales, R.; Doni, S.; Masciandaro, G.; Moreno, B.

    2016-11-01

    Because their crucial role in several soil biochemical cycles and their fast response to changes in soil management, extracellular enzymes activities are widely used as sensitive indicators of ecological change and soil quality. The aim of this work was to determine the effects of soil management on the stable pool of soil carbon cycling enzymes as indicators of essential functions. For this, extracellular β-glucosidase enzymes bounded by humic acids (C higher than 104 Da) were used to compare four long-term contrasting agricultural managements in a rainfed olive orchard representative of semi-arid Mediterranean habitats. The study was conducted for 30 years by designing a random-block of four treatments (nude vs. covered soils) and four replicates. Maintaining cover crops through fall, winter and early spring provoked a more stable and active pool of extracellular β-glucosidase in soils only if spontaneous vegetation was managed with mechanical methods. When herbicides were used during 30 years, the pattern of the molecular composition and activity of humus β-glucosidase complexes were similar in covered and nude soils, although higher activity was retrieved in the former. Tillage management increased carbon mineralization and the level of humic substances and the activity of β-glucosidase humic-bound were quite lower than in the rest of treatments. Given the ecological role of extracellular soil carbon cycling enzymes, the characterization of humus β-glucosidase complexes could be an adequate indicator of sustainability of agricultural management systems. (Author)

  6. A note on the convexity of the expected queue length of the M/M/s queue with respect to the arrival rate: a third proof

    Directory of Open Access Journals (Sweden)

    A. Mehrez

    1992-01-01

    Full Text Available The convexity of the expected number in an M/M/s queue with respect to the arrival rate (or traffic intensity is well known. Grassmann [1] proves this result directly by making use of a bound on the probability that all servers are busy. Independently, Lee and Cohen [2] derive this result by showing that the Erlang delay formula is a convex function. In this note, we provide a third method of proof, which exploits the relationship between the Erlang delay formula and the Poisson probability distribution. Several interesting intermediate results are also obtained.

  7. 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.

  8. Activity-Based Costing: A Cost Management Tool.

    Science.gov (United States)

    Turk, Frederick J.

    1993-01-01

    In college and university administration, overhead costs are often charged to programs indiscriminately, whereas the support activities that underlie those costs remain unanalyzed. It is time for institutions to decrease ineffective use of resources. Activity-based management attributes costs more accurately and can improve efficiency. (MSE)

  9. Impact of sensing errors on the queueing delay and transmit power in cognitive radio access

    KAUST Repository

    Hamza, Doha R.

    2011-03-01

    We study a multiple-access system with a primary user (PU) and a secondary user (SU) utilizing the same frequency band and communicating with a common receiver. Both users transmit with a fixed transmission rate by employing a channel inversion power control scheme. The SU transmits with a certain probability that depends on the sensing outcome, its queue length and whether it has a new packet arrival. We consider the case of erroneous sensing. The goal of the SU is to find the optimal transmission scheduling policy so as to minimize its queueing delay under constraints on its average transmit power and the maximum tolerable primary outage probability caused by miss-detection. The access probabilities are obtained efficiently using linear programming. © 2011 IEEE.

  10. 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.

  11. 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.

  12. 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.

  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. Analysis of M/G/1 queueing model with state dependent arrival and vacation

    Science.gov (United States)

    Singh, Charan Jeet; Jain, Madhu; Kumar, Binay

    2012-05-01

    This investigation deals with single server queueing system wherein the arrival of the units follow Poisson process with varying arrival rates in different states and the service time of the units is arbitrary (general) distributed. The server may take a vacation of a fixed duration or may continue to be available in the system for next service. Using the probability argument, we construct the set of steady state equations by introducing the supplementary variable corresponding to elapsed service time. Then, we obtain the probability generating function of the units present in the system. Various performance indices, such as expected number of units in the queue and in the system, average waiting time, etc., are obtained explicitly. Some special cases are also deduced by setting the appropriate parameter values. The numerical illustrations are provided to carry out the sensitivity analysis in order to explore the effect of different parameters on the system performance measures.

  15. Probabilistic Decomposition Method on the ServerIndices of an Mξ/G/1 Vacation Queue

    Directory of Open Access Journals (Sweden)

    Renbin Liu

    2014-01-01

    Full Text Available This paper develops a probabilistic decomposition method for an Mξ/G/1 repairable queueing system with multiple vacations, in which the customers who arrive during server vacations enter the system with probability p. Such a novel method is used to analyze the main performance indices of the server, such as the unavailability and the mean failure number during (0,t]. It is derived that the structures of server indices are two convolution equations. Further, comparisons with existing methods indicate that our method is effective and applicable for studying server performances in single-server Mξ/G/1 vacation queues and their complex variants. Finally, a stochastic order and production system with a multipurpose production facility is numerically presented for illustrative purpose.

  16. Optimal design of queueing systems for using communication channels with multiple access

    Science.gov (United States)

    Sonkin, D. M.; Nazarov, A. A.; Khrul, S. A.; Kudryashova, A. V.

    2017-01-01

    This article considers the mathematical model of queueing systems for the communication network with multiple access, which is used in the automated group of moving objects control systems. The dynamic communication model in the form of a single-line queuing model with the batch input claims was researched. The method of asymptotic analysis of the communication channel under a heavy load conditions was applied. As a result, the basic probabilistic characteristics of the system were obtained, including: the probability distribution of the waiting time values of the virtual claims, the average length of the queue claims at random time. It has been discovered that the characteristics of the communications models allow performing parametric optimization of communication networks, establishing the most appropriate values of the network parameters.

  17. Improved diagonal queue medical image steganography using Chaos theory, LFSR, and Rabin cryptosystem.

    Science.gov (United States)

    Jain, Mamta; Kumar, Anil; Choudhary, Rishabh Charan

    2017-06-01

    In this article, we have proposed an improved diagonal queue medical image steganography for patient secret medical data transmission using chaotic standard map, linear feedback shift register, and Rabin cryptosystem, for improvement of previous technique (Jain and Lenka in Springer Brain Inform 3:39-51, 2016). The proposed algorithm comprises four stages, generation of pseudo-random sequences (pseudo-random sequences are generated by linear feedback shift register and standard chaotic map), permutation and XORing using pseudo-random sequences, encryption using Rabin cryptosystem, and steganography using the improved diagonal queues. Security analysis has been carried out. Performance analysis is observed using MSE, PSNR, maximum embedding capacity, as well as by histogram analysis between various Brain disease stego and cover images.

  18. The double queue method: a numerical method for integrate-and-fire neuron networks.

    Science.gov (United States)

    Lee, G; Farhat, N H

    2001-01-01

    Numerical methods for initial-value problems based on finite-differencing of differential equations (FDM) are not well suited for the simulation of an integrate-and-fire neuron network (IFNN) due to the discontinuities implied by the firing condition of the neurons. The Double Queue Method (DQM) is an event-queue based numerical method designed for the simulation of an IFNN that can deal with such discontinuities properly. In the DQM, the states of individual neurons at the next predicted discontinuous points are determined by an analytic solution, meaning an optimal performance in both accuracy and speed. A comparison study with the FDM demonstrates the superiority of the DQM, and provides some examples where the FDM gives inaccurate results that can possibly lead to a false conclusion about the dynamics of an IFNN.

  19. 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.

  20. Analysis of a Constant Retrial Queue with Joining Strategy and Impatient Retrial Customers

    Directory of Open Access Journals (Sweden)

    Shan Gao

    2017-01-01

    Full Text Available This paper treats an M/M/1 retrial queue with constant retrial times. If the server is busy at the arrival epoch, the arriving customer decides to join the retrial orbit with probability q or balk with probability 1-q. Only the customer at the head of the orbit is permitted to access the server. Upon retrial, the customer immediately receives his service if the server is idle; otherwise, he may enter the orbit again or leave the system because of impatience. First, we give the performance analysis for this retrial queue and give some important performance indices. Second, based on a natural reward-cost structure, we analyze the Nash equilibrium customers’ joining strategies and give some numerical examples.

  1. Delay decomposition at a single server queue with constant service time and multiple inputs

    Science.gov (United States)

    Ziegler, C.; Schilling, D. L.

    1978-01-01

    Two network consisting of single server queues, each with a constant service time, are considered. The external inputs to each network are assumed to follow some general probability distribution. Several interesting equivalencies that exist between the two networks considered are derived. This leads to the introduction of an important concept in delay decomposition. It is shown that the waiting time experienced by a customer can be decomposed into two basic components called self-delay and interference delay.

  2. Optimal threshold policies in a two-class preemptive priority queue with admission and termination control

    NARCIS (Netherlands)

    Brouns, G.A.J.F.; van der Wal, J.

    2006-01-01

    We consider a two-class M-lambda 1,M-lambda 2\\M-mu\\1 preemptive priority queue in which there are two essential, on-line decisions that have to be taken. The first is the decision to either accept or reject new type-1 or type-2 jobs. The second is the decision to abort jobs, i.e., to remove any

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

    Directory of Open Access Journals (Sweden)

    B. Krishna Kumar

    2008-01-01

    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.

  4. Efficient queue length detection at traffic signals using probe vehicle data and data fusion

    OpenAIRE

    Neumann, Thorsten

    2009-01-01

    In this paper, a new method for the detection of queue lengths at traffic signals is described. Based on conventional probe vehicle data and implementing an extremely flexible data fusion approach for the integration of nearly arbitrary additional traffic information, it provides an efficient way to get high-quality estimates for the traffic states at traffic signals. A systematic evaluation based on extensive simulations addresses several issues concerning quality and demonstrates both th...

  5. A Paradox in a Queueing Network with State-Dependent Routing and Loss

    Directory of Open Access Journals (Sweden)

    Ilze Ziedins

    2007-01-01

    Full Text Available Consider a network of parallel finite tandem queues with two stages, where each arrival attempts to minimize its own cost due to loss. It is known that the user optimal and asymptotic system optimal policies may differ—we give examples showing that they may differ for finite systems and that as the service rate is increased at the second stage the user optimal policy may change in such a way that the total expected cost due to loss increases.

  6. The transformation of the probability of a heart fatality into a queue position.

    Science.gov (United States)

    Rivett, P; Anglin, T; Meyer, A

    1998-10-01

    The population of Bury and Rochdale has a much higher rate of Coronary Heart Disease than the national average. This paper develops an approach, based on the Framingham score method, of making patients aware in a lucid manner of their risk of suffering a fatal heart attack by assigning them a position in a queue of people who are similar to them so far as non-modifiable risk factors are concerned.

  7. Modelling M/G/1 queueing systems with server vacations using ...

    African Journals Online (AJOL)

    Figure 2: MRSPN model of the single vacation M/G/1/N/Vl queueing system. There is an additional place PC in this model to record the fact that the server has com- pleted at least one service before going away on a vacation. The immediate transition S2, when enabled, places a token in PC, thus keeping a record of the first ...

  8. Do case-generic measures of queue performance for bypass surgery accurately reflect the waiting-list experiences of those most urgent?

    Science.gov (United States)

    Burstein, Jason; Lee, Douglas S; Alter, David A

    2006-02-01

    Queue performance is typically assessed using generic measures, which capture the queue in aggregate. The objective of this study was to examine whether case-generic measures of queue performance appropriately reflected the waiting-list experiences of those patients with greatest disease severity. We examined the queue for isolated coronary artery bypass grafting (CABG) in Ontario between April 1993 and March 2000 using data obtained from the Cardiac Care Network. Our primary measure of queue performance was the proportion of patients who received their bypass surgery within their recommended maximum waiting times (%RMWTs) in any given month. We compared case-generic measures of queue performance to case-specific measures of queue performance stratified by urgency level. The queue was largely comprised of elective cases ranging from 73% (1993) to 57%(1999). Urgent patients comprised the minority of the queue ranging from 14% (1993) to 20% (1999). Case-generic month-to-month variations in the percentage of cases completed within RMWTs (an aggregated waiting list measure encompassing the characteristics of all patients in the queue) closely resembled the experiences of elective patients (R2 = 0.81), but conversely, bore little relationship to the waiting-list experiences of those most urgent (R2 = 0.15). Case-generic measures of queue performance for bypass surgery in Ontario were not reflective of the waiting-list experiences of those most urgent. Our results reinforce the concept that urgency-specific waiting list monitoring systems are required to best evaluate and appropriately respond to fluctuations in queue performance.

  9. Money Management Activities in Persons With Multiple Sclerosis.

    Science.gov (United States)

    Goverover, Yael; Haas, Shannon; DeLuca, John

    2016-11-01

    To examine whether participants with multiple sclerosis (MS) have more problems in managing finances compared with persons without MS, and to examine the variables that may contribute to these problems. A cross-sectional study. Nonprofit rehabilitation research institution and the community. Participants (N=53) comprised adults with MS (n=30) and persons without MS (n=23) who were recruited from a nonprofit rehabilitation research institution and from the community. Not applicable. Participants were administered a battery of neuropsychological tests, a money management survey, and a functional test to assess money management skills. Individuals with MS reported and demonstrated more problems managing money than persons without MS. Impaired cognitive functioning was significantly correlated with difficulties in money management. Self-report of functional status (Functional Behavior Profile) was significantly correlated with self-reported money management skills. To our knowledge, this is the first study to examine money management in MS. Money management is an important activity of daily living that presents problems for individuals with MS. Managing one's own money requires adequate processing speed abilities as well as executive-attentional abilities. Additional studies are needed to explore this area and understand the nature of the problem. Copyright © 2016 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

  10. A spatiotemporal model for the LTE uplink: Spatially interacting tandem queues approach

    KAUST Repository

    Gharbieh, Mohammad

    2017-07-31

    With the proliferation of the Internet-of-things (IoT), there is an undeniable consensus that cellular LTE networks will have to support a dramatically larger number of uplink connections. This is true since most of the devices to be added incur machine-type communications which is dominantly upstream. Can current LTE network withstand this challenge? To answer this question, the joint performance of random access process and the uplink data transmission should be investigated. These two problems have been classically treated in the literature in a disjoint fashion. In this paper, they are jointly analyzed as an inseparable couple. To do that, a tandem queuing model is adopted whereby devices are represented as spatially interacting queues. The interaction between queues is governed by the mutual inter-cell and intra-cell interference. To that end, a joint stochastic geometry and queueing theory model is exploited to study this problem and a spatiotemporal analytical model is developed accordingly. Network stability and scalability are two prime performance criteria for performance assessment. In light of these two criteria, the developed model is poised to offer valuable insights into efficient access and resource allocation strategies.

  11. 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.

  12. 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.

  13. 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.

  14. Constructions of Optical Queues With a Limited Number of Recirculations--Part II: Optimal Constructions

    CERN Document Server

    Huang, Xuan-Chao

    2010-01-01

    One of the main problems in all-optical packet-switched networks is the lack of optical buffers, and one feasible technology for the constructions of optical buffers is to use optical crossbar Switches and fiber Delay Lines (SDL). In this two-part paper, we consider SDL constructions of optical queues with a limited number of recirculations through the optical switches and the fiber delay lines. Such a problem arises from practical feasibility considerations. In Part I, we have proposed a class of greedy constructions for certain types of optical queues, including linear compressors, linear decompressors, and 2-to-1 FIFO multiplexers, and have shown that every optimal construction among our previous constructions of these types of optical queues under the constraint of a limited number of recirculations must be a greedy construction. In Part II, the present paper, we further show that there are at most two optimal constructions and give a simple algorithm to obtain the optimal construction(s). The main idea i...

  15. 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.

  16. STAFF ACTIVE AND REFLECTIVE LEARNING (ARL) TO ENHANCE STUDENT MANAGEMENT

    OpenAIRE

    Tay Sing Leong; Lim See Yew

    2010-01-01

    The Staff Active Reflective Learning (ARL) is a new scheme designed to enhance student management though regular get-togethers of a group of teaching staff. It provides a platform for staff to share issues related to teaching, and seek solutions. This addresses current and future challenges faced in classroom management. The implementation of the Staff ARL is one of the recent initiatives taken under a new approach to shared learning within the School of Electronic and Info-Comm Technology. I...

  17. Measuring the True Cost of Active Management by Mutual Funds

    OpenAIRE

    Miller, Ross M.

    2005-01-01

    Recent years have seen a dramatic shift from mutual funds into hedge funds even though hedge funds charge management fees that have been decried as outrageous. While expectations of superior returns may be responsible for this shift, this article shows that mutual funds are more expensive than commonly believed. Mutual funds appear to provide investment services for relatively low fees because they bundle passive and active funds management together in a way that understates the true cost of ...

  18. Physical activity: the forgotten tool for type 2 diabetes management

    OpenAIRE

    Colberg, Sheri R.

    2012-01-01

    Individuals who are currently sedentary, unfit, or overweight can benefit metabolically from simply taking breaks from sitting. Since avoidance of sedentary behavior appears to have a large impact on glycemic management, all individuals with type 2 diabetes should be encouraged to minimally engage in greater daily movement to better manage their diabetes and body weight. In addition, engaging in physical activity of any intensity (including low-intensity ones) likely positively impacts insuli...

  19. Quality management technology impact on small enterprise production activities

    Directory of Open Access Journals (Sweden)

    Ivanova Natalia

    2017-01-01

    Full Text Available A modern quality management technology, the so-called quality management system (QMS, can improve the indicators of production activities of any company. Due to the advantages of a small business such project can be implemented faster and at lesser costs. The conducted research of the QMS development in accordance with ISO 9001-2015 at a particular small St. Petersburg enterprise in 2016 resulted in the growth of production output and labor productivity. The obtained results of the standards introduction in the troublesome divisions of a small firm demonstrate the attractiveness of the given technology for the top management of a corporation.

  20. Training to Support Standardization and Improvement of Configuration Management Activities

    Energy Technology Data Exchange (ETDEWEB)

    Dauber, V.; Scheffer, N.; Schoenfelder, C.

    2015-07-01

    In recent years AREVA has conducted several measures to enhance the effectiveness and efficiency of configuration management-related activities within a nuclear power plant (NPP) new build as well as modernization projects, thereby further strengthening its commitment to achieving the highest level of safety in nuclear facilities. This paper describes a new training course that shall support the standardization and improvement of configuration management activities. Recommendations will be given that should be considered when designing and developing comparable training programs to support change processes within engineering units. (Author)

  1. WAX ActiveLibrary: a tool to manage information overload.

    Science.gov (United States)

    Hanka, R; O'Brien, C; Heathfield, H; Buchan, I E

    1999-11-01

    WAX Active-Library (Cambridge Centre for Clinical Informatics) is a knowledge management system that seeks to support doctors' decision making through the provision of electronic books containing a wide range of clinical knowledge and locally based information. WAX has been piloted in several regions in the United Kingdom and formally evaluated in 17 GP surgeries based in Cambridgeshire. The evaluation has provided evidence that WAX Active-Library significantly improves GPs' access to relevant information sources and by increasing appropriate patient management and referrals this might also lead to an improvement in clinical outcomes.

  2. Capacity Planning and Leadtime management

    NARCIS (Netherlands)

    Zijm, Willem H.M.; Buitenhek, R.

    1996-01-01

    In this paper we discuss a framework for capacity planning and lead time management in manufacturing companies, with an emphasis on the machine shop. First we show how queueing models can be used to find approximations of the mean and the variance of manufacturing shop lead times. These quantities

  3. Surgery or physical activity in the management of sciatica

    DEFF Research Database (Denmark)

    Fernandez, Matthew; Ferreira, Manuela L; Refshauge, Kathryn M

    2016-01-01

    PURPOSE: Previous reviews have compared surgical to non-surgical management of sciatica, but have overlooked the specific comparison between surgery and physical activity-based interventions. METHODS: Systematic review using MEDLINE, CINAHL, Embase and PEDro databases was conducted. Randomised...... controlled trials comparing surgery to physical activity, where patients were experiencing the three most common causes of sciatica-disc herniation, spondylolisthesis and spinal stenosis. Two independent reviewers extracted pain and disability data (converted to a common 0-100 scale) and assessed...

  4. Contributions for territorial management of risks associated with oil activity

    Directory of Open Access Journals (Sweden)

    Felipe Pinto Gonçalves

    2013-06-01

    Full Text Available Whereas that the growing complexity of technical and spatial organization of the oil activity in Espírito Santo state gives new demands for land use management to the local governments, this article addresses the issue of economic and technological risks associated with such activities. Based on the evaluation of legal instruments such as the classification of land uses and the zoning, are discussed the possibilities of insertion the risks in municipal policies for land use planning

  5. Dose Determination of Activated Charcoal in Management of ...

    African Journals Online (AJOL)

    The LOD and LOQ of the method for amitriptyline were 0.109 and 0.332 μg/ml, respectively. The validated method was successfully applied to measure plasma concentrations of amitriptyline and to measure the doses of activated charcoal currently used in the management of acute amitriptyline drug poisoning. Conclusion: ...

  6. Dose Determination of Activated Charcoal in Management of ...

    African Journals Online (AJOL)

    Purpose: To assess the doses of activated charcoal currently used in the management of acute amitriptyline-induced drug poisoning and explore the possibility of using lower doses. Methods: Albino male Wistar rats, weighing 200 ± 20 g, were used for the study. The animals were divided into four groups of eight animals ...

  7. How an Active Learning Classroom Transformed IT Executive Management

    Science.gov (United States)

    Connolly, Amy; Lampe, Michael

    2016-01-01

    This article describes how our university built a unique classroom environment specifically for active learning. This classroom changed students' experience in the undergraduate executive information technology (IT) management class. Every college graduate should learn to think critically, solve problems, and communicate solutions, but 90% of…

  8. Draft position paper on knowledge management in space activities

    Science.gov (United States)

    Holm, Jeanne; Moura, Denis

    2003-01-01

    As other fields of industry, space activities are facing the challenge of Knowledge Management and the International Academy of Astronautics decided to settle in 2002 a Study Group to analyse the problem and issue general guidelines. This communication presents the draft position paper of this group in view to be discussed during the 2003 IAF Congress.

  9. Microgrids in Active Network Management-Part I

    DEFF Research Database (Denmark)

    Palizban, Omid; Kauhaniemia, Kimmo; Guerrero, Josep M.

    2014-01-01

    The microgrid concept has been closely investigated and implemented by numerous experts worldwide. The first part of this paper describes the principles of microgrid design, considering the operational concepts and requirements arising from participation in active network management. Over the last...

  10. Exploring Learner Participation in Waste-Management Activities in a ...

    African Journals Online (AJOL)

    participatory approach part of the infusion of environmental education in the school curriculum as prescribed by the infusion policy, ... culture through equating waste-management activities with environmental education. This generally ..... grass, he can be bitten by a snake as you can see how tall that grass is. But now our ...

  11. The process of marketing management – between the management marketing activities and the operational marketing

    Directory of Open Access Journals (Sweden)

    Luminita Zait

    2009-12-01

    Full Text Available The best known definitions provided to the concept of marketing management, in the last decades of the 21st century have in common – the orientation towards the client and the development of successfull relations with the clients, the substantion and operationalization of the mix of marketing, as the basis of the exchange relation, the involvement of all functional areas inside the organisation in managing relations in order to achieve the long term objectives of the organization – but the main issues are related to four basic activities: - analysis, planning, implementing and controlling marketing activities.

  12. SECONDARY WASTE MANAGEMENT STRATEGY FOR EARLY LOW ACTIVITY WASTE TREATMENT

    Energy Technology Data Exchange (ETDEWEB)

    TW, CRAWFORD

    2008-07-17

    This study evaluates parameters relevant to River Protection Project secondary waste streams generated during Early Low Activity Waste operations and recommends a strategy for secondary waste management that considers groundwater impact, cost, and programmatic risk. The recommended strategy for managing River Protection Project secondary waste is focused on improvements in the Effiuent Treatment Facility. Baseline plans to build a Solidification Treatment Unit adjacent to Effluent Treatment Facility should be enhanced to improve solid waste performance and mitigate corrosion of tanks and piping supporting the Effiuent Treatment Facility evaporator. This approach provides a life-cycle benefit to solid waste performance and reduction of groundwater contaminants.

  13. Microgrids in Active Network Management-Part II

    DEFF Research Database (Denmark)

    Palizban, Omid; Kauhaniemi, Kimmo; Guerrero, Josep M.

    2014-01-01

    The development of distribution networks for participation in active network management (ANM) and smart grids is introduced using the microgrid concept. In recent years, this issue has been researched and implemented by many experts. The second part of this paper describes those developed......, following planned or unplanned transitions to island mode, microgrids may develop instability. For this reason, the paper addresses the principles behind island-detection methods, black-start operation, fault management, and protection systems, along with a comprehensive review of power quality. Finally...

  14. Route activity tracking and management using available technology

    Directory of Open Access Journals (Sweden)

    Sam Yousef Khoury

    2012-01-01

    Full Text Available Small organizations that maintain their own fleet and make their own deliveries are responsible for ensuring their drivers are utilizing the most efficient routes while delivering products to their customers. Furthermore, efficient delivery requires that drivers spend as little time as possible dropping off and picking up products, since these activities are referred to as “non-value added activities,” although they are necessary tasks in the order cycle process. To aid in reducing order cycle times, large organizations that can afford it have employed transportation management systems. Unfortunately, small organizations with limited resources are less likely to adopt transportation management systems, despite the need for such automation. One solution is to use available productivity software to track and manage driver route activity in an effort to improve and maintain driver productivity by reducing non-value time and identifying optimal routes. This paper will outline how office productivity software such as Microsoft® Access can meet the needs of small organizations with limited resources by describing the development and use of a route activity database that employs an easy-to-use multi-user interface. This paper also includes the details of the underlying infrastructure and the user interface.

  15. Rationale choosing interval of a piecewise-constant approximation of input rate of non-stationary queue system

    Science.gov (United States)

    Korelin, Ivan A.; Porshnev, Sergey V.

    2018-01-01

    The paper demonstrates the possibility of calculating the characteristics of the flow of visitors to objects carrying out mass events passing through checkpoints. The mathematical model is based on the non-stationary queuing system (NQS) where dependence of requests input rate from time is described by the function. This function was chosen in such way that its properties were similar to the real dependencies of speed of visitors arrival on football matches to the stadium. A piecewise-constant approximation of the function is used when statistical modeling of NQS performing. Authors calculated the dependencies of the queue length and waiting time for visitors to service (time in queue) on time for different laws. Time required to service the entire queue and the number of visitors entering the stadium at the beginning of the match were calculated too. We found the dependence for macroscopic quantitative characteristics of NQS from the number of averaging sections of the input rate.

  16. 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.

  17. 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.

  18. Smoothed perturbation analysis algorithms for estimating the derivatives of occupancy-related functions in serial queueing networks

    Science.gov (United States)

    Wardi, Y.; Gong, W.-B.; Cassandras, C. G.; Kallmes, M. H.

    1991-01-01

    The authors present smoothed perturbation analysis (SPA) estimators for the derivative of a number of occupancy-related functions in serial queuing networks with finite buffer spaces. The functions are the average number of customers at a network as seen by an arrival, the probability that a customer is blocked at a particular queue, and the probability that a customer leaves a queue empty. In all three cases, the variable is a parameter of the distribution of service times at one of the queues. The derivative estimators considered are very simple and flexible, and they easily lend themselves to analysis of unbiasedness. Unlike most of the established SPA estimators, the present ones are not based on the computation of hazard rates.

  19. 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.

  20. The transient analysis of the queue-length distribution in the batch arrival system with N-policy, multiple vacations and setup times

    Science.gov (United States)

    Kempa, Wojciech M.

    2010-10-01

    A batch arrival queueing system of the MX/G/1 type with unlimited queue is considered. After each busy period the server begins a multiple vacation period, consisting of independent single vacations, when the service process is blocked. The server begins successive single vacations as far as at the end of one of them the number of customers waiting in the queue equals at least N. The service of the first customer after the vacation period is preceded by a setup time. The analysis of the queue-size distribution on the first vacation cycle is directed to the analysis of the same characteristic in the corresponding "usual" system with unremovable server on its first busy period. The renewal-theory approach is used to obtain results in the general case. As main result the explicit representation for the LT of queue-size distribution is derived for the original system.