Purification processes are widely used in hydrogen networks of refineries to increase hydrogen reuse. In refineries, hydrogen purification techniques include hydrocarbon, hydrogen sulfide and CO removal units. In addi...Purification processes are widely used in hydrogen networks of refineries to increase hydrogen reuse. In refineries, hydrogen purification techniques include hydrocarbon, hydrogen sulfide and CO removal units. In addition, light hydrocarbon recovery from the hydrogen source streams can also result in hydrogen purification. In order to simplify the superstructure and mathematical model of hydrogen network integration, the models of different purification processes are unified in this paper, including mass balance and the expressions for hydrogen recovery and impurity removal ratios, which are given for all the purification units in refineries. Based on the proposed unified model, a superstructure of hydrogen networks with purification processes is constructed.展开更多
In order to achieve the Quality of Service(QoS) provisioning and efficient resource utili-zation in cellular network and Wireless Local Area Network(WLAN) integration,an Integrated Ser-vice-Based Call Admission Contro...In order to achieve the Quality of Service(QoS) provisioning and efficient resource utili-zation in cellular network and Wireless Local Area Network(WLAN) integration,an Integrated Ser-vice-Based Call Admission Control(ISB-CAC) scheme is proposed in this paper.The integrated network is modeled by using multi-dimensional Markov chains.The numerical analysis is presented to evaluate the important performance measures such as the blocking probability of originating calls,the dropping probability,and the average transfer time,etc.The steady-state probabilities of the multi-dimensional Markov chains are obtained by using an iterative approach,and the CAC pa-rameters are optimally designed.The analytical model is validated by the computer simulation.It is shown that compared with the conventional WLAN-First Call Admission Control(WF-CAC) scheme,the proposed ISB-CAC scheme not only provides better QoS for mobile users but also utilizes the bandwidth resources more efficiently.展开更多
This paper presents a three-stage hypothesis on the development of creative industrial clusters, which includes stages of agglomeration, interfacing, and network development. In the first stage, micro-entities concent...This paper presents a three-stage hypothesis on the development of creative industrial clusters, which includes stages of agglomeration, interfacing, and network development. In the first stage, micro-entities concentrate geographically in a creative industrial cluster in search of resources. The second stage reflects the need for building identity. Finally, the third stage is the outcome of multi-dimensional expansion. As a creative industrial cluster develops, its focus moves from geographic concentration to division of labor and the creation of novel systems. Using this three-stage framework, this paper conducts an empirical study on Beijing＇s 798 District （＂798＂）. Our study finds that the ＂self-destruction ＂phenomenon （which appeared after 798 had reached the stage of network development in a low-level capacity） is essentially the product of a squeezing effect of commercial prosperity on art production. Our study further examines four models of art-commerce integration and explains the ways in which creative industrial clusters are different from conventional industrial clusters： a creative cluster is a platform of integration for culture, commerce, and technology. Its course of development is characterized by novelty, emergence of identity through interfacing, and network cooperation.展开更多
Considering that the collision caused by hidden terminal is particularly serious due to the narrow beams of optical de- vices, the multi-packet reception （MPR） is introduced to mitigate the collisions for IEEE 802.1...Considering that the collision caused by hidden terminal is particularly serious due to the narrow beams of optical de- vices, the multi-packet reception （MPR） is introduced to mitigate the collisions for IEEE 802.15.7 visible light com- munication （VLC） system. To explore the impact of MPR on system performance and investigate the interaction be- tween physical （PHY） layer and media access control （MAC） layer, a three dimensional （3D） integrated PHY-MAC analytical model of carrier sense muttiple access/collision avoidance （CSMA/CA） is established based on Markov chain theory for VLC system, in which MPR is implemented through the use of orthogonal code sequence. Throughput is derived to evaluate the performance of VLC system with MPR capability under imperfect optical channel. The re- sults can be used for the performance optimization of a VLC system with MPR capability.展开更多
基金Supported by the National Basic Research Program of China(2012CB720500)the National Natural Science Foundation of China(21276204,20936004)
文摘Purification processes are widely used in hydrogen networks of refineries to increase hydrogen reuse. In refineries, hydrogen purification techniques include hydrocarbon, hydrogen sulfide and CO removal units. In addition, light hydrocarbon recovery from the hydrogen source streams can also result in hydrogen purification. In order to simplify the superstructure and mathematical model of hydrogen network integration, the models of different purification processes are unified in this paper, including mass balance and the expressions for hydrogen recovery and impurity removal ratios, which are given for all the purification units in refineries. Based on the proposed unified model, a superstructure of hydrogen networks with purification processes is constructed.
基金Supported in part by the National Grand Fundamental Research Program of China (973 Program) (No. 2007CB-310606)the Specialized Foundation for the Achievements Transformation of Science and Technology of Jiangsu Province (No. BA2006101)
文摘In order to achieve the Quality of Service(QoS) provisioning and efficient resource utili-zation in cellular network and Wireless Local Area Network(WLAN) integration,an Integrated Ser-vice-Based Call Admission Control(ISB-CAC) scheme is proposed in this paper.The integrated network is modeled by using multi-dimensional Markov chains.The numerical analysis is presented to evaluate the important performance measures such as the blocking probability of originating calls,the dropping probability,and the average transfer time,etc.The steady-state probabilities of the multi-dimensional Markov chains are obtained by using an iterative approach,and the CAC pa-rameters are optimally designed.The analytical model is validated by the computer simulation.It is shown that compared with the conventional WLAN-First Call Admission Control(WF-CAC) scheme,the proposed ISB-CAC scheme not only provides better QoS for mobile users but also utilizes the bandwidth resources more efficiently.
文摘This paper presents a three-stage hypothesis on the development of creative industrial clusters, which includes stages of agglomeration, interfacing, and network development. In the first stage, micro-entities concentrate geographically in a creative industrial cluster in search of resources. The second stage reflects the need for building identity. Finally, the third stage is the outcome of multi-dimensional expansion. As a creative industrial cluster develops, its focus moves from geographic concentration to division of labor and the creation of novel systems. Using this three-stage framework, this paper conducts an empirical study on Beijing＇s 798 District （＂798＂）. Our study finds that the ＂self-destruction ＂phenomenon （which appeared after 798 had reached the stage of network development in a low-level capacity） is essentially the product of a squeezing effect of commercial prosperity on art production. Our study further examines four models of art-commerce integration and explains the ways in which creative industrial clusters are different from conventional industrial clusters： a creative cluster is a platform of integration for culture, commerce, and technology. Its course of development is characterized by novelty, emergence of identity through interfacing, and network cooperation.
基金supported by the National Natural Science Foundation of China(No.61071074)Jilin Provincial Science&Technology Department of China(No.20130413052GH)
文摘Considering that the collision caused by hidden terminal is particularly serious due to the narrow beams of optical de- vices, the multi-packet reception （MPR） is introduced to mitigate the collisions for IEEE 802.15.7 visible light com- munication （VLC） system. To explore the impact of MPR on system performance and investigate the interaction be- tween physical （PHY） layer and media access control （MAC） layer, a three dimensional （3D） integrated PHY-MAC analytical model of carrier sense muttiple access/collision avoidance （CSMA/CA） is established based on Markov chain theory for VLC system, in which MPR is implemented through the use of orthogonal code sequence. Throughput is derived to evaluate the performance of VLC system with MPR capability under imperfect optical channel. The re- sults can be used for the performance optimization of a VLC system with MPR capability.
