Using ethanol or acetone as the working fluid, visualization of oscillations in steady state was observed visually by high-speed cameras, and temperature oscillating and heat transfer characteristics of closed-loop pl...Using ethanol or acetone as the working fluid, visualization of oscillations in steady state was observed visually by high-speed cameras, and temperature oscillating and heat transfer characteristics of closed-loop plate oscillating heat pipe with parallel channels(POHP-PC) were experimentally investigated by varying liquid filled ratios(50%, 70%, 85%), section scales(1 mm×1 mm and 1 mm×1.5 mm), inclination angles, working fluids and heating inputs. It was found that during operating there was mixed flow consisting of plug flow and annular flow in channels of oscillating heat pipe at steady-state. There was an equilibrium position for working fluid of condenser during oscillating, and periodic oscillations occurred up and down in the vicinity of equilibrium position. With heat input increasing, equilibrium position rose slowly as a result of vapor pressure of evaporation.Evaporation temperature oscillating amplitude possessed a trend of small-large-small and frequency trend was of small-large during steady-state. It may be generally concluded that temperature, whether evaporator or condenser, fluctuated sharply or rose continuously when oscillating heat pipe coming to dry burning state. Simultaneously, it was found that temperature difference of cooling water possibly dropped with heat input rising during dry burning state. Thermal resistance of No. 2 with acetone was lower than that of No. 1 during experiments, but No. 2 achieving heat transfer limit was earlier than No. 1. However, with ethanol, thermal resistance of No. 1 and No. 2 were similar with the heating input less than 110-120 W and filling ratios of 50% and 70%. And with filling ratio of 85%, heating transfer performance of No. 2 was better compared to No. 1 during all the experiments.展开更多
A contour-parallel offset (CPO) tool-path linking algorithm is derived without toolretractions and with the largest practicability. The concept of "tool-path loop tree" (TPL-tree) providing the information on th...A contour-parallel offset (CPO) tool-path linking algorithm is derived without toolretractions and with the largest practicability. The concept of "tool-path loop tree" (TPL-tree) providing the information on the parent/child relationships among the tool-path loops (TPLs) is presented. The direction, tool-path loop, leaf/branch, layer number, and the corresponding points of the TPL-tree are introduced. By defining TPL as a vector, and by traveling throughout the tree, a CPO tool-path without tool-retractions can be derived.展开更多
Abstract:A low-delay loop detection algorithm for bit-flipping based iteration LDPC decoding is proposed.By introducing the concept of loop characteristic,only the iteration steps with loop characteristics are detecte...Abstract:A low-delay loop detection algorithm for bit-flipping based iteration LDPC decoding is proposed.By introducing the concept of loop characteristic,only the iteration steps with loop characteristics are detected and labeled for the subsequent loop detection.As a result,computation delay is greatly reduced.Furthermore,the position vector for the selected iteration steps is also established to implement loop detection for these iteration steps,which reduces the hardware cost of the loop detection as well.The validity of the proposed algorithm is verified by simulations.展开更多
【目的】针对现有2自由度并联机构构型创新不足、运动学性能分析不完善等问题,进行了新型单回路平移并联机构拓扑综合与运动学性能研究,为杆式模块化机器人提供基础运动单元设计理论。【方法】首先,根据基于方位特征(Position and Orien...【目的】针对现有2自由度并联机构构型创新不足、运动学性能分析不完善等问题,进行了新型单回路平移并联机构拓扑综合与运动学性能研究,为杆式模块化机器人提供基础运动单元设计理论。【方法】首先,根据基于方位特征(Position and Orientation Characterization,POC)的并联机构拓扑设计方法,提出了4个由2个移动副和5个转动副组成的单回路平移空间并联机构,对其进行拓扑分析;其次,分别推导出4个平移并联机构的符号化位置正反解,以及发生奇异的条件及其奇异位置,并分别进行了数值算例验证;最后,运用差分进化算法,以最大工作空间为优化目标,分别对4个机构进行尺度优化并求得其最大工作空间。【结果】这种单回路平移空间并联机构可用于设计杆式模块化机器人的单元,研究为基于这种单元的杆式模块化机器人的构型设计与分析奠定了基础。展开更多
基金Project(51306198)supported by the National Natural Science Foundation of ChinaProject(NR2013K07)supported by Beijing Key Lab of Heating,Gas Supply,Ventilating and Air Conditioning Engineering,China+1 种基金Project(331614013)supported by Beijing University of Civil Engineering and Architecture,ChinaProject(00921915023)supported by Organization Department of Beijing,China
摘要Using ethanol or acetone as the working fluid, visualization of oscillations in steady state was observed visually by high-speed cameras, and temperature oscillating and heat transfer characteristics of closed-loop plate oscillating heat pipe with parallel channels(POHP-PC) were experimentally investigated by varying liquid filled ratios(50%, 70%, 85%), section scales(1 mm×1 mm and 1 mm×1.5 mm), inclination angles, working fluids and heating inputs. It was found that during operating there was mixed flow consisting of plug flow and annular flow in channels of oscillating heat pipe at steady-state. There was an equilibrium position for working fluid of condenser during oscillating, and periodic oscillations occurred up and down in the vicinity of equilibrium position. With heat input increasing, equilibrium position rose slowly as a result of vapor pressure of evaporation.Evaporation temperature oscillating amplitude possessed a trend of small-large-small and frequency trend was of small-large during steady-state. It may be generally concluded that temperature, whether evaporator or condenser, fluctuated sharply or rose continuously when oscillating heat pipe coming to dry burning state. Simultaneously, it was found that temperature difference of cooling water possibly dropped with heat input rising during dry burning state. Thermal resistance of No. 2 with acetone was lower than that of No. 1 during experiments, but No. 2 achieving heat transfer limit was earlier than No. 1. However, with ethanol, thermal resistance of No. 1 and No. 2 were similar with the heating input less than 110-120 W and filling ratios of 50% and 70%. And with filling ratio of 85%, heating transfer performance of No. 2 was better compared to No. 1 during all the experiments.
摘要A contour-parallel offset (CPO) tool-path linking algorithm is derived without toolretractions and with the largest practicability. The concept of "tool-path loop tree" (TPL-tree) providing the information on the parent/child relationships among the tool-path loops (TPLs) is presented. The direction, tool-path loop, leaf/branch, layer number, and the corresponding points of the TPL-tree are introduced. By defining TPL as a vector, and by traveling throughout the tree, a CPO tool-path without tool-retractions can be derived.
基金National Science Foundation of China(No.61072069)the 111 Project(B08038)
摘要Abstract:A low-delay loop detection algorithm for bit-flipping based iteration LDPC decoding is proposed.By introducing the concept of loop characteristic,only the iteration steps with loop characteristics are detected and labeled for the subsequent loop detection.As a result,computation delay is greatly reduced.Furthermore,the position vector for the selected iteration steps is also established to implement loop detection for these iteration steps,which reduces the hardware cost of the loop detection as well.The validity of the proposed algorithm is verified by simulations.
摘要【目的】针对现有2自由度并联机构构型创新不足、运动学性能分析不完善等问题,进行了新型单回路平移并联机构拓扑综合与运动学性能研究,为杆式模块化机器人提供基础运动单元设计理论。【方法】首先,根据基于方位特征(Position and Orientation Characterization,POC)的并联机构拓扑设计方法,提出了4个由2个移动副和5个转动副组成的单回路平移空间并联机构,对其进行拓扑分析;其次,分别推导出4个平移并联机构的符号化位置正反解,以及发生奇异的条件及其奇异位置,并分别进行了数值算例验证;最后,运用差分进化算法,以最大工作空间为优化目标,分别对4个机构进行尺度优化并求得其最大工作空间。【结果】这种单回路平移空间并联机构可用于设计杆式模块化机器人的单元,研究为基于这种单元的杆式模块化机器人的构型设计与分析奠定了基础。