Similar to most mountain glaciers in the world, Urumqi Glacier No. 1 （UG1）, the best observed glacier in China with continued glaciological and climatological monitoring records of longer than 50 years has experienc...Similar to most mountain glaciers in the world, Urumqi Glacier No. 1 （UG1）, the best observed glacier in China with continued glaciological and climatological monitoring records of longer than 50 years has experienced an accelerated recession during the past several decades. The purpose of this study is to investigate the acceleration of recession. By taking UG1 as an example, we analyze the generic mechanisms of acceleration of shrinkage of continental mountain glaciers. The results indicate that the acceleration of mass loss of UG1 commenced first in 1985 and second in 1996 and that the lat- ter was more vigorous. The air temperature rises during melting season, the ice temperature augment of the glacier and the albedo reduction on the glacier surface are considered responsible for the accelerated recession. In addition, the simulations of the accelerated shrinkage of UG1 are introduced in this article.展开更多
随着网络带宽的迅速增长,主机协议处理开销已经成为系统整体性能的瓶颈.近年来,在协议加速领域开展了大量的研究工作,主要分为协议处理机制、实现以及结构的优化.在分析了协议处理的开销与性能之后,从协议机制、实现和处理结构这3方面对...随着网络带宽的迅速增长,主机协议处理开销已经成为系统整体性能的瓶颈.近年来,在协议加速领域开展了大量的研究工作,主要分为协议处理机制、实现以及结构的优化.在分析了协议处理的开销与性能之后,从协议机制、实现和处理结构这3方面对TCP(transmission control protocol)加速技术的研究现状进行了总结,并分析了进一步的研究方向.展开更多
High-speed and precision positioning are fundamental requirements for high-acceleration low-load mechanisms in integrated circuit （IC） packaging equipment. In this paper, we derive the transient nonlinear dynamicres...High-speed and precision positioning are fundamental requirements for high-acceleration low-load mechanisms in integrated circuit （IC） packaging equipment. In this paper, we derive the transient nonlinear dynamicresponse equations of high-acceleration mechanisms, which reveal that stiffness, frequency, damping, and driving frequency are the primary factors. Therefore, we propose a new structural optimization and velocity-planning method for the precision positioning of a high-acceleration mechanism based on optimal spatial and temporal distribution of inertial energy. For structural optimization, we first reviewed the commonly flexible multibody dynamic optimization using equivalent static loads method （ESLM）, and then we selected the modified ESLM for optimal spatial distribution of inertial energy; hence, not only the stiffness but also the inertia and frequency of the real modal shapes are considered. For velocity planning, we developed a new velocity-planning method based on nonlinear dynamic-response optimization with varying motion conditions. Our method was verified on a high-acceleration die bonder. The amplitude of residual vibration could be decreased by more than 20% via structural optimization and the positioning time could be reduced by more than 40% via asymmetric variable velocity planning. This method provides an effective theoretical support for the precision positioning of high-acceleration low-load mechanisms.展开更多
基金supported by the National Basic Research Program of China (No. 2007CB411501)the Knowledge Innovation Project of the Chinese Academy of Sciences (No. KZCX2-EW-311)the National Natural Science Foundation of China (Nos. 91025012, J0930003/J0109)
文摘Similar to most mountain glaciers in the world, Urumqi Glacier No. 1 （UG1）, the best observed glacier in China with continued glaciological and climatological monitoring records of longer than 50 years has experienced an accelerated recession during the past several decades. The purpose of this study is to investigate the acceleration of recession. By taking UG1 as an example, we analyze the generic mechanisms of acceleration of shrinkage of continental mountain glaciers. The results indicate that the acceleration of mass loss of UG1 commenced first in 1985 and second in 1996 and that the lat- ter was more vigorous. The air temperature rises during melting season, the ice temperature augment of the glacier and the albedo reduction on the glacier surface are considered responsible for the accelerated recession. In addition, the simulations of the accelerated shrinkage of UG1 are introduced in this article.
文摘随着网络带宽的迅速增长,主机协议处理开销已经成为系统整体性能的瓶颈.近年来,在协议加速领域开展了大量的研究工作,主要分为协议处理机制、实现以及结构的优化.在分析了协议处理的开销与性能之后,从协议机制、实现和处理结构这3方面对TCP(transmission control protocol)加速技术的研究现状进行了总结,并分析了进一步的研究方向.
基金supported by the National Key Basic Research Program of China (2011CB013104)National Natural Science Foundation of China (U1134004)+2 种基金Guangdong Provincial Natural Science Foundation (2015A030312008)Science and Technology Program of Guangzhou (201510010281)Guangdong Provincial Science and Technology Plan (2013B010402014)
文摘High-speed and precision positioning are fundamental requirements for high-acceleration low-load mechanisms in integrated circuit （IC） packaging equipment. In this paper, we derive the transient nonlinear dynamicresponse equations of high-acceleration mechanisms, which reveal that stiffness, frequency, damping, and driving frequency are the primary factors. Therefore, we propose a new structural optimization and velocity-planning method for the precision positioning of a high-acceleration mechanism based on optimal spatial and temporal distribution of inertial energy. For structural optimization, we first reviewed the commonly flexible multibody dynamic optimization using equivalent static loads method （ESLM）, and then we selected the modified ESLM for optimal spatial distribution of inertial energy; hence, not only the stiffness but also the inertia and frequency of the real modal shapes are considered. For velocity planning, we developed a new velocity-planning method based on nonlinear dynamic-response optimization with varying motion conditions. Our method was verified on a high-acceleration die bonder. The amplitude of residual vibration could be decreased by more than 20% via structural optimization and the positioning time could be reduced by more than 40% via asymmetric variable velocity planning. This method provides an effective theoretical support for the precision positioning of high-acceleration low-load mechanisms.
