During the current epidemic,it is necessary to ensure the rehabilitation treatment of children with serious illness.At the same time,however,it is essential to effectively prevent cross-infection and prevent infection...During the current epidemic,it is necessary to ensure the rehabilitation treatment of children with serious illness.At the same time,however,it is essential to effectively prevent cross-infection and prevent infections from occurring within the hospital setting.To resolve this contradiction,the rehabilitation department of Nanjing Children’s Hospital adjusted its bed allocation based on the queuing model,with reference to the regional source and classification of the children’s conditions in the rehabilitation department ward.The original triple rooms were transformed into a double room to enable the treatment of severely sick children coming from other places.A M/G/2 queuing model with priority was also applied to analyze the state of patient admissions.Moreover,patients in Nanjing were also classified into mild and severe cases.The M/M/1 queuing model with priority was used for analysis of this situation,so that severely ill children could be treated in time while patients with mild symptoms could be treated at home.This approach not only eases the bed tension in the ward,but also provides suitable conditions for controlling cross-infection.展开更多
An Ethereum blockchain based on proof of stake ( PoS) consensus mechanism is used to achieve the data sharing within the civil aviation service platform for both airport group management and passengers. Considering th...An Ethereum blockchain based on proof of stake ( PoS) consensus mechanism is used to achieve the data sharing within the civil aviation service platform for both airport group management and passengers. Considering the Gas consumption of Ethereum, the dynamic batch-service capacity constraint by the Block Gas Limit and the priority mechanism depending on the different Gas Price of transactions, M/ G/1 queuing theory with batch-service is used to construct the service model of transactions confirmation process in the proposed blockchain system, where the effects of transactions arrival rate, block capacity, service rate and number of nodes on the average confirmation time of transactions with different priority are analyzed, and eventually a performance analysis model of blockchain for civil aviation business data is proposed. The simulation results prove the usability and accuracy of the model, which can provide both theoretical basis for data sharing of civil aviation using Ethereum blockchain and the further optimization of transactions confirmation time.展开更多
Exploring theory and methods to analyze the impacts of non real-time services on jitter performance of real-time services is a quite challenging but meaningful job. This article puts forward a general theoretical meth...Exploring theory and methods to analyze the impacts of non real-time services on jitter performance of real-time services is a quite challenging but meaningful job. This article puts forward a general theoretical method to calculate packet jitter in network node bearing mixed services. Based on queuing theory and Markov theory, the network node is modeled as a double-queue single-server and limited-cache queuing system with thresholds. Two-state Markov-modulated Bernoulli process (MMBP-2) and interrupted Bernoulli process (IBP) are used to model the arrival processes of real-time services and small data services respectively in a packet switched network. In order to depict the interaction between real-time services and small data services, a four-dimensional discrete-time Markov chain is implemented to describe the transition of the system states. By solving the system model, expressions for packet jitter are obtained. The results given by the model are then compared with the simulation results obtained by network simulator, version 3 (NS-3).展开更多
High energy consumption is one of the key issues of cloud computing systems. Incoming jobs in cloud computing environments have the nature of randomness, and compute nodes have to be powered on all the time to await i...High energy consumption is one of the key issues of cloud computing systems. Incoming jobs in cloud computing environments have the nature of randomness, and compute nodes have to be powered on all the time to await incoming tasks. This results in a great waste of energy. An energy-saving task scheduling algorithm based on the vacation queuing model for cloud computing systems is proposed in this paper. First, we use the vacation queuing model with exhaustive service to model the task schedule of a heterogeneous cloud computing system.Next, based on the busy period and busy cycle under steady state, we analyze the expectations of task sojourn time and energy consumption of compute nodes in the heterogeneous cloud computing system. Subsequently, we propose a task scheduling algorithm based on similar tasks to reduce the energy consumption. Simulation results show that the proposed algorithm can reduce the energy consumption of the cloud computing system effectively while meeting the task performance.展开更多
The couple between the power network and the transportation network(TN)is deepening gradually with the increasing penetration rate of electric vehicles(EV),which also poses a great challenge to the traditional voltage...The couple between the power network and the transportation network(TN)is deepening gradually with the increasing penetration rate of electric vehicles(EV),which also poses a great challenge to the traditional voltage control scheme.In this paper,we propose a coordinated voltage control strategy for the active distribution networks considering multiple types of EV.In the first stage,the action of on-load tap changer and capacitor banks,etc.,are determined by optimal power flow calculation,and the node electricity price is also determined based on dynamic time-of-use tariff mechanism.In the second stage,multiple operating scenarios of multiple types of EVs such as cabs,private cars and buses are considered,and the scheduling results of each EV are solved by building an optimization model based on constraints such as queuing theory,Floyd-Warshall algorithm and traffic flow information.In the third stage,the output power of photovoltaic and energy storage systems is fine-tuned in the normal control mode.The charging power of EVs is also regulated in the emergency control mode to reduce the voltage deviation,and the amount of regulation is calculated based on the fair voltage control mode of EVs.Finally,we test the modified IEEE 33-bus distribution system coupled with the 24-bus Beijing TN.The simulation results show that the proposed scheme can mitigate voltage violations well.展开更多
This paper shows the researches of the queuing theory,especially the Markov Chainand the Poison Process,and implements the efficient way of designing the queuing system.Then simulating the queuing systems based on the...This paper shows the researches of the queuing theory,especially the Markov Chainand the Poison Process,and implements the efficient way of designing the queuing system.Then simulating the queuing systems based on the“Simply package”in the“Python”programming language.And the paper would discuss and analyze the differences between different queuing systems.展开更多
To ensure the security of resource and intelligence sharing in 6G,blockchain has been widely adopted in wireless communications and applications.Although blockchain can ensure the traceability and non-tamperability of...To ensure the security of resource and intelligence sharing in 6G,blockchain has been widely adopted in wireless communications and applications.Although blockchain can ensure the traceability and non-tamperability of data in the concatenated blocks,it cannot guarantee the honest behaviors of users in the application before the generation of transactions.Thus,additional technologies are required to ensure that the source of blockchain data is reliable.In this paper,the detailed procedure is designed for the application-oriented task validation in the blockchainenhanced computing resource sharing and transactions in ultra dense networks(UDN).The corresponding queuing model is built and analyzed with the consideration of the wireless re-transmission and the probability of malicious deception by users.Based on the analysis results,the UDN deployment is optimized to save network cost while ensuring latency performance.Numerical results verify our analysis,and the optimized system deployment including the number and service capacities of both base stations and mobile edge computing(MEC)servers are also given with various system settings.展开更多
In this work,we consider the performance analysis of state dependent priority traffic and scheduling in device to device(D2D)heterogeneous networks.There are two priority transmission types of data in wireless communi...In this work,we consider the performance analysis of state dependent priority traffic and scheduling in device to device(D2D)heterogeneous networks.There are two priority transmission types of data in wireless communication,such as video or telephone,which always meet the requirements of high priority(HP)data transmission first.If there is a large amount of low priority(LP)data,there will be a large amount of LP data that cannot be sent.This situation will cause excessive delay of LP data and packet dropping probability.In order to solve this problem,the data transmission process of high priority queue and low priority queue is studied.Considering the priority jump strategy to the priority queuing model,the queuing process with two priority data is modeled as a two-dimensionalMarkov chain.A state dependent priority jump queuing strategy is proposed,which can improve the discarding performance of low priority data.The quasi birth and death process method(QBD)and fixed point iterationmethod are used to solve the causality,and the steady-state probability distribution is further obtained.Then,performance parameters such as average queue length,average throughput,average delay and packet dropping probability for both high and low priority data can be expressed.The simulation results verify the correctness of the theoretical derivation.Meanwhile,the proposed priority jump queuing strategy can significantly improve the drop performance of low-priority data.展开更多
This paper focuses on the distribution of passenger flow in Huoying Station,Line 13 of Beijing subway system.The transformation measures taken by Line 13 since operation are firstly summarized.Then the authors elabora...This paper focuses on the distribution of passenger flow in Huoying Station,Line 13 of Beijing subway system.The transformation measures taken by Line 13 since operation are firstly summarized.Then the authors elaborate the facilities and equipment of this station,especially the node layout and passenger flow field.An optimization scheme is proposed to rapidly distribute the passenger flow in Huoying Station by adjusting the operation time of the escalator in the direction of Xizhimen.The authors adopt Queuing theory and Anylogic simulation software to simulate the original and the optimized schemes of Huoying Station to distribute the passenger flow.The results of the simulation indicate that the optimized scheme could effectively alleviate the traffic congestion in the hall of Huoying Station,and the pedestrian density in other places of the hall is lowered;passengers could move freely in the hall and no new congestion points would form.The rationality of the scheme is thus proved.展开更多
The popularization of EVs(electric vehicles) has brought an increasingly heavy burden to the development of charging facilities. To meet the demand of rapid energy supply during the driving period, it is necessary to ...The popularization of EVs(electric vehicles) has brought an increasingly heavy burden to the development of charging facilities. To meet the demand of rapid energy supply during the driving period, it is necessary to establish a fast charging station in public area. However, EVs arrive at the charging station randomly and connect to the distribution network for fast charging, it causes the grid power to fluctuate greatly and the peak-valley loads to alternate frequently, which is harmful to the stability of distribution network. In order to reduce the power fluctuation of random charging, the energy storage is used for fast charging stations. The queuing model is determined to demonstrate the load characteristics of fast charging station, and the state space of fast charging station system is described by Markov chain. After that the power of grid and energy storage is quantified as the number of charging pile, and each type of power is configured rationally to establish the random charging model of energy storage fast charging station. Finally, the economic benefit is analyzed according to the queuing theory to verify the feasibility of the model.展开更多
Infrastructure of fog is a complex system due to the large number of heterogeneous resources that need to be shared.The embedded devices deployed with the Internet of Things(IoT)technology have increased since the pas...Infrastructure of fog is a complex system due to the large number of heterogeneous resources that need to be shared.The embedded devices deployed with the Internet of Things(IoT)technology have increased since the past few years,and these devices generate huge amount of data.The devices in IoT can be remotely connected and might be placed in different locations which add to the network delay.Real time applications require high bandwidth with reduced latency to ensure Quality of Service(QoS).To achieve this,fog computing plays a vital role in processing the request locally with the nearest available resources by reduced latency.One of themajor issues to focus on in a fog service is managing and allocating resources.Queuing theory is one of the most popular mechanisms for task allocation.In this work,an efficient model is designed to improve QoS with the efficacy of resource allocation based on a Queuing Theory based Cuckoo Search(QTCS)model which will optimize the overall resource management process.展开更多
According to the analysis of the very high frequency (VHF) self organized time division multiple access (S TDMA) aviation data link, a new dynamic slot assignment scheme is proposed in this paper, which adopts var...According to the analysis of the very high frequency (VHF) self organized time division multiple access (S TDMA) aviation data link, a new dynamic slot assignment scheme is proposed in this paper, which adopts variable data frame structure and can eliminate the effect of the idle slot on message delay. By using queue theory, the analysis models of the new scheme and previous scheme are presented, and the performance of message delay and that of system throughput are analyzed under two schemes. The simulation results show that the new scheme has a better performance than the previous one in the message delay and system throughput.展开更多
The queueing theory has been used by academicians and practitioners to solve supply chain problems over the years. Here, we propose a system dynamics approach and queuing theory parameters to discover the best method ...The queueing theory has been used by academicians and practitioners to solve supply chain problems over the years. Here, we propose a system dynamics approach and queuing theory parameters to discover the best method to handle the (supply chain) “Waiters” problem via a telecommunication service provider. We developed more than one system dynamics model and introduced the following parameters: the number of times information about registered waiters and the number of days required for procuring and commissioning the (telecommunication) ports are collected in a month. We found the number of waiting times for the customers is reduced and improved when the above-mentioned first parameter is performed more frequently (i.e., more than once).展开更多
This paper uses quantitative methods to estimate the size of the time buffer in lean operations controlled by the Theory of Constraints(TOC).The main focus of the operations system of TOC is the identification and man...This paper uses quantitative methods to estimate the size of the time buffer in lean operations controlled by the Theory of Constraints(TOC).The main focus of the operations system of TOC is the identification and management of constraints.To protect the constraints,they should be buffered with time buffers,which protecting the system’s output from disruptions and fluctuations.Despite the importance of time buffers,the approaches to identifying the size of the time buffer in literature are very empirical.In this paper,a queuing-theory based method is applied to calculate the time buffer sizes.It provides a mathematically exact expression for the coefficient of variation of waiting time for Markov queues.It then applies the concept of isomorphism to approximate the variance of customer waiting time in a general queue.Simulation experiments are conducted to verify the accuracy of approximation.展开更多
Greenhouse environmental management,seedling bed scheduling,and fertilizer and water management are the core technologies of seedling nursery.Precision management and control of the whole production process guarantees...Greenhouse environmental management,seedling bed scheduling,and fertilizer and water management are the core technologies of seedling nursery.Precision management and control of the whole production process guarantees high grated seedling quality.In order to improve management efficiency of grafted watermelon seedling production and seedling quality,this paper designs and develops a grafted watermelon seedling production management system based on process control methods by process control strategy,seedling bed planning design,and handheld device technology.展开更多
To deal with the challenges of both computation-complexity and algorithm-scalability posed to the design of an IPSec engine, we develop PAC (parallel algorithm core), called PAC, employed in an IPSec engine, which c...To deal with the challenges of both computation-complexity and algorithm-scalability posed to the design of an IPSec engine, we develop PAC (parallel algorithm core), called PAC, employed in an IPSec engine, which can meet requirements of both exploiting parallelism existing in IPSec packets and offering scalability in both the scales and types of cryptographic algorithms. With three kinds of parallelism and two kinds of transparency defined, a novel hierarchy of the specifically-designed parallel structure for PAC is presented, followed by corresponding mechanisms. With a simulation, the scalability of PAC is examined. For the purpose of performance evaluation, a Quasi Birth-and-Death (QBD) process is then established to model a simplified version of the proposed PAC. Performance evaluation of PAC in terms of two representative measures, throughput and mean packet waiting time, is numerically investigated. A comparison study is done on a simulation basis. Conclusions are finally drawn for providing a helpful guideline for both the design and implementation of our proposal.展开更多
In this paper we consider a retail service facility with cross-trained workers who can perform operations in both the front room and back room. Workers are brought from the back room to the front room and vice versa d...In this paper we consider a retail service facility with cross-trained workers who can perform operations in both the front room and back room. Workers are brought from the back room to the front room and vice versa depending on the number of customers in the system. A loss of productivity occurs when a worker returns to the back room. Two problems are studied. In the first problem, given the number of workers available, we determine an optimal deterministic switching policy so that the expected number of customers in queue is minimized subject to a constraint ensuring that there is a sufficient workforce to fulfill the functions in the back room. In the second problem, the number of workers needed is minimized subject to an additional constraint requiring that the expected number of customers waiting in queue is bounded above by a given threshold value. Exact solution procedures are developed and illustrative numerical examples are presented.展开更多
For real-time edge systems such as autonomous driving,not only the correctness of task functions,but also the response and processing time of tasks should be satisfied.In the hardware selection phase of a real-time sy...For real-time edge systems such as autonomous driving,not only the correctness of task functions,but also the response and processing time of tasks should be satisfied.In the hardware selection phase of a real-time system,time series analyses must be performed on the hardware platform running real-time applications.At present,the common method of worst-case execution time(WCET)analysis focuses mainly on analyzing the impact of hardware platform architecture or task execution process on the task running time.However,different tasks in an autopilot system have different levels of urgency,and preemption between tasks is the main factor that affects the task execution time.The key problem is how to quantify the time fluctuation caused by task preemption for each subtask of the autopilot system running on a fixed hardware platform.This paper presents a time analysis method for a real-time application based on a queuing theory and preemptive scheduling strategy,which assigns different priorities to tasks according to their time urgency and preemptive scheduling according to task priority.Through an experimental case study,the impact of the running time of each subtask in a real-time application with task priority preemptive scheduling is analyzed,along with the impact of changes in hardware platform performance on such real-time applications.展开更多
文摘During the current epidemic,it is necessary to ensure the rehabilitation treatment of children with serious illness.At the same time,however,it is essential to effectively prevent cross-infection and prevent infections from occurring within the hospital setting.To resolve this contradiction,the rehabilitation department of Nanjing Children’s Hospital adjusted its bed allocation based on the queuing model,with reference to the regional source and classification of the children’s conditions in the rehabilitation department ward.The original triple rooms were transformed into a double room to enable the treatment of severely sick children coming from other places.A M/G/2 queuing model with priority was also applied to analyze the state of patient admissions.Moreover,patients in Nanjing were also classified into mild and severe cases.The M/M/1 queuing model with priority was used for analysis of this situation,so that severely ill children could be treated in time while patients with mild symptoms could be treated at home.This approach not only eases the bed tension in the ward,but also provides suitable conditions for controlling cross-infection.
基金the Open Foundation of Key Laboratory of Airports Cluster Intelligent Operation(No.KLACIO201900006124)National Natural Science Foundation of China(No.61901011)+1 种基金Foundation of Beijing Municipal Commission of Education(No.KM202010005017,KM202110005021)Beijing Natural Science Foundation(No.L192002).
文摘An Ethereum blockchain based on proof of stake ( PoS) consensus mechanism is used to achieve the data sharing within the civil aviation service platform for both airport group management and passengers. Considering the Gas consumption of Ethereum, the dynamic batch-service capacity constraint by the Block Gas Limit and the priority mechanism depending on the different Gas Price of transactions, M/ G/1 queuing theory with batch-service is used to construct the service model of transactions confirmation process in the proposed blockchain system, where the effects of transactions arrival rate, block capacity, service rate and number of nodes on the average confirmation time of transactions with different priority are analyzed, and eventually a performance analysis model of blockchain for civil aviation business data is proposed. The simulation results prove the usability and accuracy of the model, which can provide both theoretical basis for data sharing of civil aviation using Ethereum blockchain and the further optimization of transactions confirmation time.
基金supported by Jilin Provincial Science & Technology Department of China(20130413052GH)
文摘Exploring theory and methods to analyze the impacts of non real-time services on jitter performance of real-time services is a quite challenging but meaningful job. This article puts forward a general theoretical method to calculate packet jitter in network node bearing mixed services. Based on queuing theory and Markov theory, the network node is modeled as a double-queue single-server and limited-cache queuing system with thresholds. Two-state Markov-modulated Bernoulli process (MMBP-2) and interrupted Bernoulli process (IBP) are used to model the arrival processes of real-time services and small data services respectively in a packet switched network. In order to depict the interaction between real-time services and small data services, a four-dimensional discrete-time Markov chain is implemented to describe the transition of the system states. By solving the system model, expressions for packet jitter are obtained. The results given by the model are then compared with the simulation results obtained by network simulator, version 3 (NS-3).
基金supported by Research and Innovation Projects for Graduates of Jiangsu Graduates of Jiangsu Province (No. CXZZ12 0483)the Science and Technology Support Program of Jiangsu Province (No. BE2012849)
文摘High energy consumption is one of the key issues of cloud computing systems. Incoming jobs in cloud computing environments have the nature of randomness, and compute nodes have to be powered on all the time to await incoming tasks. This results in a great waste of energy. An energy-saving task scheduling algorithm based on the vacation queuing model for cloud computing systems is proposed in this paper. First, we use the vacation queuing model with exhaustive service to model the task schedule of a heterogeneous cloud computing system.Next, based on the busy period and busy cycle under steady state, we analyze the expectations of task sojourn time and energy consumption of compute nodes in the heterogeneous cloud computing system. Subsequently, we propose a task scheduling algorithm based on similar tasks to reduce the energy consumption. Simulation results show that the proposed algorithm can reduce the energy consumption of the cloud computing system effectively while meeting the task performance.
基金supported by the Science and Technology Project of North China Electric Power Research Institute,which is“Research on Key Technologies for Power Quality Evaluation and Improvement of New Distribution Network Based on Collaborative Interaction of Source-Network-Load-Storage”(KJZ2022016).
文摘The couple between the power network and the transportation network(TN)is deepening gradually with the increasing penetration rate of electric vehicles(EV),which also poses a great challenge to the traditional voltage control scheme.In this paper,we propose a coordinated voltage control strategy for the active distribution networks considering multiple types of EV.In the first stage,the action of on-load tap changer and capacitor banks,etc.,are determined by optimal power flow calculation,and the node electricity price is also determined based on dynamic time-of-use tariff mechanism.In the second stage,multiple operating scenarios of multiple types of EVs such as cabs,private cars and buses are considered,and the scheduling results of each EV are solved by building an optimization model based on constraints such as queuing theory,Floyd-Warshall algorithm and traffic flow information.In the third stage,the output power of photovoltaic and energy storage systems is fine-tuned in the normal control mode.The charging power of EVs is also regulated in the emergency control mode to reduce the voltage deviation,and the amount of regulation is calculated based on the fair voltage control mode of EVs.Finally,we test the modified IEEE 33-bus distribution system coupled with the 24-bus Beijing TN.The simulation results show that the proposed scheme can mitigate voltage violations well.
文摘This paper shows the researches of the queuing theory,especially the Markov Chainand the Poison Process,and implements the efficient way of designing the queuing system.Then simulating the queuing systems based on the“Simply package”in the“Python”programming language.And the paper would discuss and analyze the differences between different queuing systems.
文摘To ensure the security of resource and intelligence sharing in 6G,blockchain has been widely adopted in wireless communications and applications.Although blockchain can ensure the traceability and non-tamperability of data in the concatenated blocks,it cannot guarantee the honest behaviors of users in the application before the generation of transactions.Thus,additional technologies are required to ensure that the source of blockchain data is reliable.In this paper,the detailed procedure is designed for the application-oriented task validation in the blockchainenhanced computing resource sharing and transactions in ultra dense networks(UDN).The corresponding queuing model is built and analyzed with the consideration of the wireless re-transmission and the probability of malicious deception by users.Based on the analysis results,the UDN deployment is optimized to save network cost while ensuring latency performance.Numerical results verify our analysis,and the optimized system deployment including the number and service capacities of both base stations and mobile edge computing(MEC)servers are also given with various system settings.
基金2020 MajorNatural Science Research Project of Jiangsu Province Colleges and Universities:Research on Forensic Modeling and Analysis of the Internet of Things(20KJA520004)2020 Open Project of National and Local Joint Engineering Laboratory of Radio Frequency Integration andMicro-assembly Technology:Research on the Security Performance of Radio Frequency Energy Collection Cooperative Communication Network(KFJJ20200201)+1 种基金2021 Jiangsu Police Officer Academy Scientific Research Project:Research on D2D Cache Network Resource Optimization Based on Edge Computing Technology(2021SJYZK01)High-level Introduction of Talent Scientific Research Start-up Fund of Jiangsu Police Institute(JSPI19GKZL407).
文摘In this work,we consider the performance analysis of state dependent priority traffic and scheduling in device to device(D2D)heterogeneous networks.There are two priority transmission types of data in wireless communication,such as video or telephone,which always meet the requirements of high priority(HP)data transmission first.If there is a large amount of low priority(LP)data,there will be a large amount of LP data that cannot be sent.This situation will cause excessive delay of LP data and packet dropping probability.In order to solve this problem,the data transmission process of high priority queue and low priority queue is studied.Considering the priority jump strategy to the priority queuing model,the queuing process with two priority data is modeled as a two-dimensionalMarkov chain.A state dependent priority jump queuing strategy is proposed,which can improve the discarding performance of low priority data.The quasi birth and death process method(QBD)and fixed point iterationmethod are used to solve the causality,and the steady-state probability distribution is further obtained.Then,performance parameters such as average queue length,average throughput,average delay and packet dropping probability for both high and low priority data can be expressed.The simulation results verify the correctness of the theoretical derivation.Meanwhile,the proposed priority jump queuing strategy can significantly improve the drop performance of low-priority data.
基金This research is supported by Beijing Municipal Natural Science Foundation(9204023)Ministry of Education“Tiancheng Huizhi”Innovation and Education Promotion Foundation(2018A01012).
文摘This paper focuses on the distribution of passenger flow in Huoying Station,Line 13 of Beijing subway system.The transformation measures taken by Line 13 since operation are firstly summarized.Then the authors elaborate the facilities and equipment of this station,especially the node layout and passenger flow field.An optimization scheme is proposed to rapidly distribute the passenger flow in Huoying Station by adjusting the operation time of the escalator in the direction of Xizhimen.The authors adopt Queuing theory and Anylogic simulation software to simulate the original and the optimized schemes of Huoying Station to distribute the passenger flow.The results of the simulation indicate that the optimized scheme could effectively alleviate the traffic congestion in the hall of Huoying Station,and the pedestrian density in other places of the hall is lowered;passengers could move freely in the hall and no new congestion points would form.The rationality of the scheme is thus proved.
基金Supported by National Key Research Program of China(2016YFB0101800)SGCC Scientific and Technological Project(520940170017)State Grid Shanghai Municipal Electric Power Company Scientific and Technological Projects(5209001500KP)
文摘The popularization of EVs(electric vehicles) has brought an increasingly heavy burden to the development of charging facilities. To meet the demand of rapid energy supply during the driving period, it is necessary to establish a fast charging station in public area. However, EVs arrive at the charging station randomly and connect to the distribution network for fast charging, it causes the grid power to fluctuate greatly and the peak-valley loads to alternate frequently, which is harmful to the stability of distribution network. In order to reduce the power fluctuation of random charging, the energy storage is used for fast charging stations. The queuing model is determined to demonstrate the load characteristics of fast charging station, and the state space of fast charging station system is described by Markov chain. After that the power of grid and energy storage is quantified as the number of charging pile, and each type of power is configured rationally to establish the random charging model of energy storage fast charging station. Finally, the economic benefit is analyzed according to the queuing theory to verify the feasibility of the model.
文摘Infrastructure of fog is a complex system due to the large number of heterogeneous resources that need to be shared.The embedded devices deployed with the Internet of Things(IoT)technology have increased since the past few years,and these devices generate huge amount of data.The devices in IoT can be remotely connected and might be placed in different locations which add to the network delay.Real time applications require high bandwidth with reduced latency to ensure Quality of Service(QoS).To achieve this,fog computing plays a vital role in processing the request locally with the nearest available resources by reduced latency.One of themajor issues to focus on in a fog service is managing and allocating resources.Queuing theory is one of the most popular mechanisms for task allocation.In this work,an efficient model is designed to improve QoS with the efficacy of resource allocation based on a Queuing Theory based Cuckoo Search(QTCS)model which will optimize the overall resource management process.
基金Aeronautical Science F oundation of China !( N o.98E5 1116)
文摘According to the analysis of the very high frequency (VHF) self organized time division multiple access (S TDMA) aviation data link, a new dynamic slot assignment scheme is proposed in this paper, which adopts variable data frame structure and can eliminate the effect of the idle slot on message delay. By using queue theory, the analysis models of the new scheme and previous scheme are presented, and the performance of message delay and that of system throughput are analyzed under two schemes. The simulation results show that the new scheme has a better performance than the previous one in the message delay and system throughput.
文摘The queueing theory has been used by academicians and practitioners to solve supply chain problems over the years. Here, we propose a system dynamics approach and queuing theory parameters to discover the best method to handle the (supply chain) “Waiters” problem via a telecommunication service provider. We developed more than one system dynamics model and introduced the following parameters: the number of times information about registered waiters and the number of days required for procuring and commissioning the (telecommunication) ports are collected in a month. We found the number of waiting times for the customers is reduced and improved when the above-mentioned first parameter is performed more frequently (i.e., more than once).
文摘This paper uses quantitative methods to estimate the size of the time buffer in lean operations controlled by the Theory of Constraints(TOC).The main focus of the operations system of TOC is the identification and management of constraints.To protect the constraints,they should be buffered with time buffers,which protecting the system’s output from disruptions and fluctuations.Despite the importance of time buffers,the approaches to identifying the size of the time buffer in literature are very empirical.In this paper,a queuing-theory based method is applied to calculate the time buffer sizes.It provides a mathematically exact expression for the coefficient of variation of waiting time for Markov queues.It then applies the concept of isomorphism to approximate the variance of customer waiting time in a general queue.Simulation experiments are conducted to verify the accuracy of approximation.
基金the National High Technology Research and Development Program (863) of China(No.2012AA101903)the Shanghai Municipal Agriculture Commission Program(No.20100401)+1 种基金the Science and Technology Commission of Shanghai Municipality Program(No.11DZ1960203)the Shanghai Watermelon and Melon Industry Technology System and the Shanghai Leading Academic Discipline Project Program(No.B209)
文摘Greenhouse environmental management,seedling bed scheduling,and fertilizer and water management are the core technologies of seedling nursery.Precision management and control of the whole production process guarantees high grated seedling quality.In order to improve management efficiency of grafted watermelon seedling production and seedling quality,this paper designs and develops a grafted watermelon seedling production management system based on process control methods by process control strategy,seedling bed planning design,and handheld device technology.
基金supported by the National High Technology Development 863 Program of China (Grant No. 2005AA121210).
文摘To deal with the challenges of both computation-complexity and algorithm-scalability posed to the design of an IPSec engine, we develop PAC (parallel algorithm core), called PAC, employed in an IPSec engine, which can meet requirements of both exploiting parallelism existing in IPSec packets and offering scalability in both the scales and types of cryptographic algorithms. With three kinds of parallelism and two kinds of transparency defined, a novel hierarchy of the specifically-designed parallel structure for PAC is presented, followed by corresponding mechanisms. With a simulation, the scalability of PAC is examined. For the purpose of performance evaluation, a Quasi Birth-and-Death (QBD) process is then established to model a simplified version of the proposed PAC. Performance evaluation of PAC in terms of two representative measures, throughput and mean packet waiting time, is numerically investigated. A comparison study is done on a simulation basis. Conclusions are finally drawn for providing a helpful guideline for both the design and implementation of our proposal.
基金Supported by a grant from the Faculty Research Committee at the C. W. Post Campus of Long Island University
文摘In this paper we consider a retail service facility with cross-trained workers who can perform operations in both the front room and back room. Workers are brought from the back room to the front room and vice versa depending on the number of customers in the system. A loss of productivity occurs when a worker returns to the back room. Two problems are studied. In the first problem, given the number of workers available, we determine an optimal deterministic switching policy so that the expected number of customers in queue is minimized subject to a constraint ensuring that there is a sufficient workforce to fulfill the functions in the back room. In the second problem, the number of workers needed is minimized subject to an additional constraint requiring that the expected number of customers waiting in queue is bounded above by a given threshold value. Exact solution procedures are developed and illustrative numerical examples are presented.
基金supported by the National Key Research and Development Program under Grant No.2019YFC0118404the National Natural Science Foundation of China under Grant No.U20A20386+2 种基金the Zhejiang Key Research and Development Program under Grant No.2020C01050the Key Laboratory fund general project under Grant No.6142110190406the Zhejiang Natural Science Foundation Project under Grant No.LY19F020044
文摘For real-time edge systems such as autonomous driving,not only the correctness of task functions,but also the response and processing time of tasks should be satisfied.In the hardware selection phase of a real-time system,time series analyses must be performed on the hardware platform running real-time applications.At present,the common method of worst-case execution time(WCET)analysis focuses mainly on analyzing the impact of hardware platform architecture or task execution process on the task running time.However,different tasks in an autopilot system have different levels of urgency,and preemption between tasks is the main factor that affects the task execution time.The key problem is how to quantify the time fluctuation caused by task preemption for each subtask of the autopilot system running on a fixed hardware platform.This paper presents a time analysis method for a real-time application based on a queuing theory and preemptive scheduling strategy,which assigns different priorities to tasks according to their time urgency and preemptive scheduling according to task priority.Through an experimental case study,the impact of the running time of each subtask in a real-time application with task priority preemptive scheduling is analyzed,along with the impact of changes in hardware platform performance on such real-time applications.