近日,佳能(中国)发布了恒定F2.8光圈L级旗舰远摄变焦镜头RF100-300mm F2.8 L IS USM。这支镜头的诞生进一步拓展了佳能RF远摄镜头阵营。在单反相机时代,佳能EF 300mm f/2.8L IS II USM镜头以其尖端技术、高画质得到了专业摄影师和摄影...近日,佳能(中国)发布了恒定F2.8光圈L级旗舰远摄变焦镜头RF100-300mm F2.8 L IS USM。这支镜头的诞生进一步拓展了佳能RF远摄镜头阵营。在单反相机时代,佳能EF 300mm f/2.8L IS II USM镜头以其尖端技术、高画质得到了专业摄影师和摄影爱好者的一致好评。现在,借助先进的RF卡口,佳能将被看作是尖端技术和高画质标杆的EF 300mm f/2.8L IS II USM“移植”到了这支起步100mm焦距、具有3倍变焦倍率的RF100-300mm F2.8 L IS USM上,使RF100-300mm F2.8 L IS USM这支恒定F2.8大光圈L级远摄变焦镜头不仅具备可匹敌F2.8大光圈定焦镜头的高画质,还可覆盖100-300mm宽广焦距范围。它将高表现力与便利性集于一身,在拍摄室内外体育比赛、T台时装秀、红毯走秀、飞机火车、野生动物等题材和新闻报道中可以大显身手。展开更多
Evaluation of IEEE 802.11 Mobile Ad Hoc Networks (MANET) security issues becomes significant concern for researchers since Denial of Service (DoS) attacks are recognized as one of the most harmful threats. A variety o...Evaluation of IEEE 802.11 Mobile Ad Hoc Networks (MANET) security issues becomes significant concern for researchers since Denial of Service (DoS) attacks are recognized as one of the most harmful threats. A variety of security mechanisms are proposed to solve security dilemma in MANETs against different layers of DoS attacks. Physical Layer jamming attacks exhaust the victim’s network resources such as bandwidth, computing power, battery, etc. Unified Security Mechanism (USM) and Rate Adaptation Scheme (RAS) are two of the proposed methods by researchers against DoS attacks. USM and RAS mechanisms are simulated through OPNET simulator and Jamming Attack is generated on the network for each security mechanisms to compare specific performance metrics on the network.展开更多
A unified second-order moment (USM) turbulence-chemistry model for simulating NOx formation in turbulent combustion is proposed.All of correlations,including the correlation of the reaction-rate coefficient fluctuatio...A unified second-order moment (USM) turbulence-chemistry model for simulating NOx formation in turbulent combustion is proposed.All of correlations,including the correlation of the reaction-rate coefficient fluctuation with the concentration fluctuation,are closed by the transport equations in the same form.This model discards the approximation of series expansion of the exponential function or the approximation of using the product of several 1-D PDF's instead of a joint PDF.It is much simpler than other refined models,such as the PDF transport equation model and the conditional moment closure model.The proposed model is used to simulate methane-air swirling turbulent combustion and NOx formation.The prediction results are in good agreement with the experimental results.展开更多
文摘近日,佳能(中国)发布了恒定F2.8光圈L级旗舰远摄变焦镜头RF100-300mm F2.8 L IS USM。这支镜头的诞生进一步拓展了佳能RF远摄镜头阵营。在单反相机时代,佳能EF 300mm f/2.8L IS II USM镜头以其尖端技术、高画质得到了专业摄影师和摄影爱好者的一致好评。现在,借助先进的RF卡口,佳能将被看作是尖端技术和高画质标杆的EF 300mm f/2.8L IS II USM“移植”到了这支起步100mm焦距、具有3倍变焦倍率的RF100-300mm F2.8 L IS USM上,使RF100-300mm F2.8 L IS USM这支恒定F2.8大光圈L级远摄变焦镜头不仅具备可匹敌F2.8大光圈定焦镜头的高画质,还可覆盖100-300mm宽广焦距范围。它将高表现力与便利性集于一身,在拍摄室内外体育比赛、T台时装秀、红毯走秀、飞机火车、野生动物等题材和新闻报道中可以大显身手。
文摘Evaluation of IEEE 802.11 Mobile Ad Hoc Networks (MANET) security issues becomes significant concern for researchers since Denial of Service (DoS) attacks are recognized as one of the most harmful threats. A variety of security mechanisms are proposed to solve security dilemma in MANETs against different layers of DoS attacks. Physical Layer jamming attacks exhaust the victim’s network resources such as bandwidth, computing power, battery, etc. Unified Security Mechanism (USM) and Rate Adaptation Scheme (RAS) are two of the proposed methods by researchers against DoS attacks. USM and RAS mechanisms are simulated through OPNET simulator and Jamming Attack is generated on the network for each security mechanisms to compare specific performance metrics on the network.
文摘A unified second-order moment (USM) turbulence-chemistry model for simulating NOx formation in turbulent combustion is proposed.All of correlations,including the correlation of the reaction-rate coefficient fluctuation with the concentration fluctuation,are closed by the transport equations in the same form.This model discards the approximation of series expansion of the exponential function or the approximation of using the product of several 1-D PDF's instead of a joint PDF.It is much simpler than other refined models,such as the PDF transport equation model and the conditional moment closure model.The proposed model is used to simulate methane-air swirling turbulent combustion and NOx formation.The prediction results are in good agreement with the experimental results.
