Casting aluminum(Al)alloys have been widely used in the automotive industry to improve fuel economy as well as to reduce greenhouse gas(GHG)emissions in the vehicle use phase.However,the casting Al alloys used for loa...Casting aluminum(Al)alloys have been widely used in the automotive industry to improve fuel economy as well as to reduce greenhouse gas(GHG)emissions in the vehicle use phase.However,the casting Al alloys used for load-bearing body and chassis components today are mostly made from primary Al with a low impurity Fe content typically less than 0.2 wt.%,owing to the requirements for high ductility and adequate fatigue strength.Primary Al is made directly from alumina which was refined from aluminum ore(bauxite),using an electrolytic process which consumes a lot of energy and produces GHG emissions that are much higher than those from steel making.The objective of this paper is to present a Unified Casting(UniCast)Al alloy concept as a sustainable materials solution for vehicle lightweighting.The UniCast alloy chemistry is intentionally designed to be more tolerant of Fe impurity.This chemistry can not only satisfy the requirements on castability,but also deliver mechanical properties needed for a variety of thin-walled and thick-walled automotive structural components that are produced by various casting processes.The UniCast alloy concept will contribute to the establishment of a closed-loop recycling system in the future as the shredded scrap obtained from the disposed end-of-life vehicles can be directly recycled back into UniCast alloy ingot with a more efficient sorting process.In addition,by setting the upper limit of Fe content in the UniCast alloy to a higher level,it will become possible to use a high fraction of post-consumer scraps to produce this alloy.To demonstrate the feasibility of this concept,an exemplary UniCast alloy chemistry has been elaborated in this article.Furthermore,challenges and future research opportunities related to the realization of UniCast alloy concept in the automotive industry are discussed.It is hoped that this article will be of great implication to industrial researchers and academicians for making concerted efforts to establish closed-loop recycling of Al castings for the automotive and other transportation industry segments.展开更多
The optimal rate control problem in networks with unicast and multiratemulticast sessions is investigated. A penalty function approach is used to solve a convex programformulation of this problem, and then a heuristic...The optimal rate control problem in networks with unicast and multiratemulticast sessions is investigated. A penalty function approach is used to solve a convex programformulation of this problem, and then a heuristic rate control algorithm is derived. The algorithmis distributed, and suitable both for source-driven unicast sessions and receiver-driven multicastsessions. To obtain practical viability, the computational burden on core routers as well asend-hosts is kept very low, also is the overhead of network congestion feedback. Simulation resultsshow that the algorithm guarantees TCP (Transmission Control Protocol)-based unicast sessionscoexisting with multirate multicast sessions in a fair and friendly manner. It is also shown thatvarious fairness criteria of resource allocation could be achieved by choosing appropriate utilityfunctions, and resource-utilizing efficiencies would be likewise different.展开更多
Over the past few years, numerous traffic safety applications have been developed using vehicular ad hoc networks(VANETs). These applications represent public interest and require network-wide dissemination techniques...Over the past few years, numerous traffic safety applications have been developed using vehicular ad hoc networks(VANETs). These applications represent public interest and require network-wide dissemination techniques. On the other hand, certain non-safety applications do not require network-wide dissemination techniques.Such applications can be characterized by their individual interest between two vehicles that are geographically apart. In the existing literature, several proposals of unicast protocols exist that can be used for these non-safety applications. Among the proposals, unicast protocols for city scenarios are considered to be most challenging.This implies that in city scenarios unicast protocols show minimal persistence towards highly dynamic vehicular characteristics, including mobility, road structure, and physical environment. Unlike other studies, this review is motivated by the diversity of vehicular characteristics and difficulty of unicast protocol adaption in city scenarios.The review starts with the categorization of unicast protocols for city scenarios according to their requirement for a predefined unicast path. Then, properties of typical city roads are discussed, which helps to explore limitations in efficient unicast communication. Through an exhaustive literature review, we propose a thematic taxonomy based on different aspects of unicast protocol operation. It is followed by a review of selected unicast protocols for city scenarios that reveal their fundamental characteristics. Several significant parameters from the taxonomy are used to qualitatively compare the reviewed protocols. Qualitative comparison also includes critical investigation of distinct approaches taken by researchers in experimental protocol evaluation. As an outcome of this review, we point out open research issues in unicast routing.展开更多
With the deployment of heterogeneous networks, mobile users are expecting ubiquitous connectivity when using applications. For bandwidth-intensive applications such as Internet Protocol Television(IPTV), multimedia co...With the deployment of heterogeneous networks, mobile users are expecting ubiquitous connectivity when using applications. For bandwidth-intensive applications such as Internet Protocol Television(IPTV), multimedia contents are typically transmitted using a multicast delivery method due to its bandwidth efficiency. However, not all networks support multicasting. Multicasting alone could lead to service disruption when the users move from a multicast-capable network to a non-multicast network. In this paper, we propose a handover scheme called application layer seamless switching(ALSS) to provide smooth real-time multimedia delivery across unicast and multicast networks. ALSS adopts a soft handover to achieve seamless playback during the handover period. A real-time streaming testbed is implemented to investigate the overall handover performance, especially the overlapping period where both network interfaces are receiving audio and video packets. Both the quality of service(QoS) and objective-mapped quality of experience(QoE) metrics are measured. Experimental results show that the overlapping period takes a minimum of 56 and 4 ms for multicast-to-unicast(M2U) and unicast-to-multicast(U2M) handover, respectively. The measured peak signal-to-noise ratio(PSNR) confirms that the frame-by-frame quality of the streamed video during the handover is at least 33 dB, which is categorized as good based on ITU-T recommendations. The estimated mean opinion score(MOS) in terms of video playback smoothness is also at a satisfactory level.展开更多
在轨道交通控制系统中,为了保证车辆控制稳定和运行数据及故障记录准确可靠,其关键部件——中央控制单元(Central Control Unit,CCU)和数据记录单元(Event Record Machine,ERM)采用嵌入式实时操作系统VxWorks。一般情况下,该系统启动时...在轨道交通控制系统中,为了保证车辆控制稳定和运行数据及故障记录准确可靠,其关键部件——中央控制单元(Central Control Unit,CCU)和数据记录单元(Event Record Machine,ERM)采用嵌入式实时操作系统VxWorks。一般情况下,该系统启动时需要先启动DOS,之后再被当作一般软件调用启动。在系统启动失败、前面板6个灯常亮故障的基础上,研究DOS对电子盘的读写对其启动过程的影响,提出并验证一种可以直接在FAT32格式电子盘上启动解决方案,避免系统启动失败问题。然后结合作者遇到的不同版本VxWorks在应用过程中的UDP单播问题、FTP文件传输问题、启动检查DBR及读写LBA扇区问题进行测试,并提出了解决方案。展开更多
为提高水电厂监控系统性能,本文研究提出了水电厂监控系统新型通信模型。论文基于以太网的开放系统互联参考模型OSI(Open Systems Interconnection Reference Model)架构,分析了目前水电厂监控系统普遍采用单播和广播相结合的以太网通...为提高水电厂监控系统性能,本文研究提出了水电厂监控系统新型通信模型。论文基于以太网的开放系统互联参考模型OSI(Open Systems Interconnection Reference Model)架构,分析了目前水电厂监控系统普遍采用单播和广播相结合的以太网通信的优点和不足,分析了传输控制协议TCP(Transmission Control Protocol)模型架构和报文发送、握手连接及断开连接过程,阐述了用户数据报协议UDP(User Datagram Protocol)网络模型的特点,提出了改进UDP网络协议安全性的措施。本文系统对比分析了单播、组播和广播网络信息传输模型的特点,探讨了单播、组播和广播网络信息传送模型与TCP和UDP相结合的以太网网络通信模型的特点。基于对TCP网络协议模型在广播中的可靠性与实时性研究,本文提出了一种UDP与IP组播技术相结合的新型水电厂计算机监控系统网络通信模型,可大幅提高监控系统通信实时性和可靠性,并通过实际工程应用案例进行验证和分析,为水电厂计算机监控系统通信模型建立提供新的选择,具有巨大的应用前景和推广价值。展开更多
In this paper, the requirements of routing due to the multimedia applications are briefly discussed. In order to solve the QoS constrained routing effectively and efficiently, the scheme of routing based on Hopfield n...In this paper, the requirements of routing due to the multimedia applications are briefly discussed. In order to solve the QoS constrained routing effectively and efficiently, the scheme of routing based on Hopfield neural network is proposed after the analysis of related work. Then the QoS routing algorithm for unicast based on Hopfield NN is described and the result of emulation is given. At last, multicast QoS routing considerations based on Hopfield NN are proposed.展开更多
基金the National Natural Science Foundation of China(No.51904352)the Scientific Research Foundation of Hunan Provincial Education Department,China(No.22A0004).
文摘Casting aluminum(Al)alloys have been widely used in the automotive industry to improve fuel economy as well as to reduce greenhouse gas(GHG)emissions in the vehicle use phase.However,the casting Al alloys used for load-bearing body and chassis components today are mostly made from primary Al with a low impurity Fe content typically less than 0.2 wt.%,owing to the requirements for high ductility and adequate fatigue strength.Primary Al is made directly from alumina which was refined from aluminum ore(bauxite),using an electrolytic process which consumes a lot of energy and produces GHG emissions that are much higher than those from steel making.The objective of this paper is to present a Unified Casting(UniCast)Al alloy concept as a sustainable materials solution for vehicle lightweighting.The UniCast alloy chemistry is intentionally designed to be more tolerant of Fe impurity.This chemistry can not only satisfy the requirements on castability,but also deliver mechanical properties needed for a variety of thin-walled and thick-walled automotive structural components that are produced by various casting processes.The UniCast alloy concept will contribute to the establishment of a closed-loop recycling system in the future as the shredded scrap obtained from the disposed end-of-life vehicles can be directly recycled back into UniCast alloy ingot with a more efficient sorting process.In addition,by setting the upper limit of Fe content in the UniCast alloy to a higher level,it will become possible to use a high fraction of post-consumer scraps to produce this alloy.To demonstrate the feasibility of this concept,an exemplary UniCast alloy chemistry has been elaborated in this article.Furthermore,challenges and future research opportunities related to the realization of UniCast alloy concept in the automotive industry are discussed.It is hoped that this article will be of great implication to industrial researchers and academicians for making concerted efforts to establish closed-loop recycling of Al castings for the automotive and other transportation industry segments.
文摘The optimal rate control problem in networks with unicast and multiratemulticast sessions is investigated. A penalty function approach is used to solve a convex programformulation of this problem, and then a heuristic rate control algorithm is derived. The algorithmis distributed, and suitable both for source-driven unicast sessions and receiver-driven multicastsessions. To obtain practical viability, the computational burden on core routers as well asend-hosts is kept very low, also is the overhead of network congestion feedback. Simulation resultsshow that the algorithm guarantees TCP (Transmission Control Protocol)-based unicast sessionscoexisting with multirate multicast sessions in a fair and friendly manner. It is also shown thatvarious fairness criteria of resource allocation could be achieved by choosing appropriate utilityfunctions, and resource-utilizing efficiencies would be likewise different.
基金Project supported by the High Impact Research,University of Malaya and Ministry of Higher Education of Malaysia(No.UM.C/HIR/MOHE/FCSIT/09)
文摘Over the past few years, numerous traffic safety applications have been developed using vehicular ad hoc networks(VANETs). These applications represent public interest and require network-wide dissemination techniques. On the other hand, certain non-safety applications do not require network-wide dissemination techniques.Such applications can be characterized by their individual interest between two vehicles that are geographically apart. In the existing literature, several proposals of unicast protocols exist that can be used for these non-safety applications. Among the proposals, unicast protocols for city scenarios are considered to be most challenging.This implies that in city scenarios unicast protocols show minimal persistence towards highly dynamic vehicular characteristics, including mobility, road structure, and physical environment. Unlike other studies, this review is motivated by the diversity of vehicular characteristics and difficulty of unicast protocol adaption in city scenarios.The review starts with the categorization of unicast protocols for city scenarios according to their requirement for a predefined unicast path. Then, properties of typical city roads are discussed, which helps to explore limitations in efficient unicast communication. Through an exhaustive literature review, we propose a thematic taxonomy based on different aspects of unicast protocol operation. It is followed by a review of selected unicast protocols for city scenarios that reveal their fundamental characteristics. Several significant parameters from the taxonomy are used to qualitatively compare the reviewed protocols. Qualitative comparison also includes critical investigation of distinct approaches taken by researchers in experimental protocol evaluation. As an outcome of this review, we point out open research issues in unicast routing.
基金Project supported by the Ministry of Science,Technology and Innovation under the eScienceFund(No.01-01-03-SF0782)MIMOS Berhad
文摘With the deployment of heterogeneous networks, mobile users are expecting ubiquitous connectivity when using applications. For bandwidth-intensive applications such as Internet Protocol Television(IPTV), multimedia contents are typically transmitted using a multicast delivery method due to its bandwidth efficiency. However, not all networks support multicasting. Multicasting alone could lead to service disruption when the users move from a multicast-capable network to a non-multicast network. In this paper, we propose a handover scheme called application layer seamless switching(ALSS) to provide smooth real-time multimedia delivery across unicast and multicast networks. ALSS adopts a soft handover to achieve seamless playback during the handover period. A real-time streaming testbed is implemented to investigate the overall handover performance, especially the overlapping period where both network interfaces are receiving audio and video packets. Both the quality of service(QoS) and objective-mapped quality of experience(QoE) metrics are measured. Experimental results show that the overlapping period takes a minimum of 56 and 4 ms for multicast-to-unicast(M2U) and unicast-to-multicast(U2M) handover, respectively. The measured peak signal-to-noise ratio(PSNR) confirms that the frame-by-frame quality of the streamed video during the handover is at least 33 dB, which is categorized as good based on ITU-T recommendations. The estimated mean opinion score(MOS) in terms of video playback smoothness is also at a satisfactory level.
文摘在轨道交通控制系统中,为了保证车辆控制稳定和运行数据及故障记录准确可靠,其关键部件——中央控制单元(Central Control Unit,CCU)和数据记录单元(Event Record Machine,ERM)采用嵌入式实时操作系统VxWorks。一般情况下,该系统启动时需要先启动DOS,之后再被当作一般软件调用启动。在系统启动失败、前面板6个灯常亮故障的基础上,研究DOS对电子盘的读写对其启动过程的影响,提出并验证一种可以直接在FAT32格式电子盘上启动解决方案,避免系统启动失败问题。然后结合作者遇到的不同版本VxWorks在应用过程中的UDP单播问题、FTP文件传输问题、启动检查DBR及读写LBA扇区问题进行测试,并提出了解决方案。
文摘为提高水电厂监控系统性能,本文研究提出了水电厂监控系统新型通信模型。论文基于以太网的开放系统互联参考模型OSI(Open Systems Interconnection Reference Model)架构,分析了目前水电厂监控系统普遍采用单播和广播相结合的以太网通信的优点和不足,分析了传输控制协议TCP(Transmission Control Protocol)模型架构和报文发送、握手连接及断开连接过程,阐述了用户数据报协议UDP(User Datagram Protocol)网络模型的特点,提出了改进UDP网络协议安全性的措施。本文系统对比分析了单播、组播和广播网络信息传输模型的特点,探讨了单播、组播和广播网络信息传送模型与TCP和UDP相结合的以太网网络通信模型的特点。基于对TCP网络协议模型在广播中的可靠性与实时性研究,本文提出了一种UDP与IP组播技术相结合的新型水电厂计算机监控系统网络通信模型,可大幅提高监控系统通信实时性和可靠性,并通过实际工程应用案例进行验证和分析,为水电厂计算机监控系统通信模型建立提供新的选择,具有巨大的应用前景和推广价值。
文摘In this paper, the requirements of routing due to the multimedia applications are briefly discussed. In order to solve the QoS constrained routing effectively and efficiently, the scheme of routing based on Hopfield neural network is proposed after the analysis of related work. Then the QoS routing algorithm for unicast based on Hopfield NN is described and the result of emulation is given. At last, multicast QoS routing considerations based on Hopfield NN are proposed.
