The rising number of electronic control units （ECUs） in vehicles and the decreasing time to market have led to the need for advanced methods of calibration. A multi-ECU calibration system was developed based on the ...The rising number of electronic control units （ECUs） in vehicles and the decreasing time to market have led to the need for advanced methods of calibration. A multi-ECU calibration system was developed based on the explicit calibration protocol （XCP） and J1939 communication protocol to satisfy the need of calibrating multiple ECUs simultaneously. The messages in the controller area network （CAN） are defined in the J1939 protocol. Each CAN node can get its own calibration messages and information from other ECUs, and block other messages by qualifying the CAN messages with priority, source or destination address. The data field of the calibration message is designed with the XCP, with CAN acting as the transport layer. The calibration sessions are setup with the event-triggered XCP driver in the master node and the responding XCP driver in the slave nodes. Mirroring calibration variables from ROM to RAM enables the user to calibrate ECUs online. The application example shows that the multi-ECU calibration system can calibrate multiple ECUs simultaneously, and the main program can also accomplish its calculation and send commands to the actuators in time. By the multi-ECU calibration system, the calibration effort and time can be reduced and the variables in ECU can get a better match with the variables of other ECUs.展开更多
Network application identification is one of the core elements in network operations and management to provide enhanced network service and security. For accurate identification, an approach using common patterns call...Network application identification is one of the core elements in network operations and management to provide enhanced network service and security. For accurate identification, an approach using common patterns called "signatures" is widely used to compensate the limitations of the traditional transport-layer port-based classification. However, our simulation results indicate that using the signatures generated from a set of well known algorithms may lead to very poor identification performance, with less than 60% of true positives even in an optimal case. To improve the quality of signatures, we present a technique in this paper, which consists of two steps:(i) pairwise merging to consider every possible combination of the initially collected signatures to reduce their specificity that causes the signatures to be less common;and (ii) signature reduction to identify effective signatures with greater importance from a large set of signatures produced in the merging step, so as to manage the space/time complexity in the identification process for greater scalability. Our experimental results show that the proposed technique can dramatically improve the performance, even with a small number of signatures (e.g., 95% true positives rate with 30 signatures per application) which is more compact than the initial signature set.展开更多
Friction factor estimation is essential in fluid flow in pipes calculations. The Colebrook equation, which is a referential standard for its estimation, is implicit in friction factor, f. This implies that f can only ...Friction factor estimation is essential in fluid flow in pipes calculations. The Colebrook equation, which is a referential standard for its estimation, is implicit in friction factor, f. This implies that f can only be obtained via iterative solution. Sequel to this, explicit approximations of the Colebrook equation developed using analytical approaches have been proposed. A shift in paradigm is the application of artificial intelligence in the area of fluid flow. The use of artificial neural network, an artificial intelligence technique for prediction of friction factor was investigated in this study. The network having a 2-30-30-1 topology was trained using the Levenberg-Marquardt back propagation algorithm. The inputs to the network consisted of 60,000 dataset of Reynolds number and relative roughness which were transformed to logarithmic scales. The performance evaluation of the model gives rise to a mean square error value of 2.456 × 10<sup>–15</sup> and a relative error of not more than 0.004%. The error indices are less than those of previously developed neural network models and a vast majority of the non neural networks are based on explicit analytical approximations of the Colebrook equation.展开更多
Following a half century of popularity, central place theory experienced 20 years of neglect when the new urban system theory of network modeling gained attention at the beginning of the 1990s. However, central place ...Following a half century of popularity, central place theory experienced 20 years of neglect when the new urban system theory of network modeling gained attention at the beginning of the 1990s. However, central place theory remains valid, and it seems there has been a reemergence with it. Using the Greater Pearl River Delta (Greater PRD) as an experimental study region, this paper intends to present an empirical study that validates central place theory and shows that it can be integrated into an overall regional urban system. The study uses the compound Central Place Importance (CPI) to evaluate whether there is a hierarchy among the urban centers within the study area. The results indicate the existence of a hierarchy. Furthermore, empirical observation finds distinct complementarity relationships, rank-size distributions, and co-operative actions between the different cities, thus substantiating the claim that central place theory can be incorporated into an overall regional urban system. Besides, the presence of the densely distributed modern infrastructure system also appears to constitute a dimension of the overall urban system. There need further theoretical and empirical studies in order to support this proposition.展开更多
Ad hoc网络是一种对等式网络，使用无线通信技术，节点可移动。Ad hoc网络拓扑的频繁变化导致了分组的大量丢失，会被TCP认为是网络发生拥塞，不正确的引发拥塞控制，从而引起吞吐量的急剧下降。使用基于反馈的体系结构与显式的报文通...Ad hoc网络是一种对等式网络，使用无线通信技术，节点可移动。Ad hoc网络拓扑的频繁变化导致了分组的大量丢失，会被TCP认为是网络发生拥塞，不正确的引发拥塞控制，从而引起吞吐量的急剧下降。使用基于反馈的体系结构与显式的报文通知机制可以有效地克服这一问题。对已有的方法进行比较研究。展开更多
为解决命名数据网络中的拥塞控制问题,提出一种博弈拥塞控制算法。将路由器为数据流分配带宽问题构建成单主多从的Stackelberg博弈模型,建立路由器和数据流的效用函数,证明数据流非合作动态博弈纳什均衡解的存在性,运用分布式迭代方法,...为解决命名数据网络中的拥塞控制问题,提出一种博弈拥塞控制算法。将路由器为数据流分配带宽问题构建成单主多从的Stackelberg博弈模型,建立路由器和数据流的效用函数,证明数据流非合作动态博弈纳什均衡解的存在性,运用分布式迭代方法,获得数据流最优带宽需求量和路由器最优价格策略,通过数据包将数据流最优带宽需求量对应的速率反馈给下游路由器和请求端。基于ndnSIM平台对该算法与ICP(interest control protocol)和HR-ICP(hop-by-hop and receiver-driven interest control protocol)算法进行仿真试验,结果表明该算法能有效提升瓶颈链路利用率并保证较低的丢包率。展开更多
文摘The rising number of electronic control units （ECUs） in vehicles and the decreasing time to market have led to the need for advanced methods of calibration. A multi-ECU calibration system was developed based on the explicit calibration protocol （XCP） and J1939 communication protocol to satisfy the need of calibrating multiple ECUs simultaneously. The messages in the controller area network （CAN） are defined in the J1939 protocol. Each CAN node can get its own calibration messages and information from other ECUs, and block other messages by qualifying the CAN messages with priority, source or destination address. The data field of the calibration message is designed with the XCP, with CAN acting as the transport layer. The calibration sessions are setup with the event-triggered XCP driver in the master node and the responding XCP driver in the slave nodes. Mirroring calibration variables from ROM to RAM enables the user to calibrate ECUs online. The application example shows that the multi-ECU calibration system can calibrate multiple ECUs simultaneously, and the main program can also accomplish its calculation and send commands to the actuators in time. By the multi-ECU calibration system, the calibration effort and time can be reduced and the variables in ECU can get a better match with the variables of other ECUs.
文摘Network application identification is one of the core elements in network operations and management to provide enhanced network service and security. For accurate identification, an approach using common patterns called "signatures" is widely used to compensate the limitations of the traditional transport-layer port-based classification. However, our simulation results indicate that using the signatures generated from a set of well known algorithms may lead to very poor identification performance, with less than 60% of true positives even in an optimal case. To improve the quality of signatures, we present a technique in this paper, which consists of two steps:(i) pairwise merging to consider every possible combination of the initially collected signatures to reduce their specificity that causes the signatures to be less common;and (ii) signature reduction to identify effective signatures with greater importance from a large set of signatures produced in the merging step, so as to manage the space/time complexity in the identification process for greater scalability. Our experimental results show that the proposed technique can dramatically improve the performance, even with a small number of signatures (e.g., 95% true positives rate with 30 signatures per application) which is more compact than the initial signature set.
文摘Friction factor estimation is essential in fluid flow in pipes calculations. The Colebrook equation, which is a referential standard for its estimation, is implicit in friction factor, f. This implies that f can only be obtained via iterative solution. Sequel to this, explicit approximations of the Colebrook equation developed using analytical approaches have been proposed. A shift in paradigm is the application of artificial intelligence in the area of fluid flow. The use of artificial neural network, an artificial intelligence technique for prediction of friction factor was investigated in this study. The network having a 2-30-30-1 topology was trained using the Levenberg-Marquardt back propagation algorithm. The inputs to the network consisted of 60,000 dataset of Reynolds number and relative roughness which were transformed to logarithmic scales. The performance evaluation of the model gives rise to a mean square error value of 2.456 × 10<sup>–15</sup> and a relative error of not more than 0.004%. The error indices are less than those of previously developed neural network models and a vast majority of the non neural networks are based on explicit analytical approximations of the Colebrook equation.
文摘Following a half century of popularity, central place theory experienced 20 years of neglect when the new urban system theory of network modeling gained attention at the beginning of the 1990s. However, central place theory remains valid, and it seems there has been a reemergence with it. Using the Greater Pearl River Delta (Greater PRD) as an experimental study region, this paper intends to present an empirical study that validates central place theory and shows that it can be integrated into an overall regional urban system. The study uses the compound Central Place Importance (CPI) to evaluate whether there is a hierarchy among the urban centers within the study area. The results indicate the existence of a hierarchy. Furthermore, empirical observation finds distinct complementarity relationships, rank-size distributions, and co-operative actions between the different cities, thus substantiating the claim that central place theory can be incorporated into an overall regional urban system. Besides, the presence of the densely distributed modern infrastructure system also appears to constitute a dimension of the overall urban system. There need further theoretical and empirical studies in order to support this proposition.
文摘为解决命名数据网络中的拥塞控制问题,提出一种博弈拥塞控制算法。将路由器为数据流分配带宽问题构建成单主多从的Stackelberg博弈模型,建立路由器和数据流的效用函数,证明数据流非合作动态博弈纳什均衡解的存在性,运用分布式迭代方法,获得数据流最优带宽需求量和路由器最优价格策略,通过数据包将数据流最优带宽需求量对应的速率反馈给下游路由器和请求端。基于ndnSIM平台对该算法与ICP(interest control protocol)和HR-ICP(hop-by-hop and receiver-driven interest control protocol)算法进行仿真试验,结果表明该算法能有效提升瓶颈链路利用率并保证较低的丢包率。
