Hysteresis Characteristics of SteeringMirror Driven by Piezoelectric Actuator and Its Experimental Research

空间激光通信精瞄系统中压电式倾斜镜存在的迟滞非线性特性,不仅降低了精瞄系统定位精度,而且对信标光的捕获以及链路的稳定性造成影响。针对该问题,提出一种基于PLAY迟滞算子改进Prandtl-Ishlinskii(P-I)数学模型及参数辨识方法,利用该模型对迟滞特性进行前馈线性化逆补偿。为进一步提高系统跟踪精度,在线性化的基础上,设计了静态输出反馈控制器,形成复合控制方法,并设计了激光通信终端精瞄系统实验,验证了该复合方法的有效性。通过对系统输入不同频率等幅和减幅正弦控制信号进行测试,结果表明,改进P-I模型最大拟合误差在1%之内,前馈模型逆补偿使压电陶瓷执行器(PEA)的线性度误差由5%减小到1%以内,复合控制方法系统跟踪误差降低了80%。</p

高效液相色谱与质谱联用分析测定川芎中有效成分阿魏酸与藁本内酯

采用HPLC-MS系统地研究了中药川芎有效成分阿魏酸(ferykuc acid)和藁本内酯(liguatilide)的定量分析方法。利用制备色谱制备了藁本内酯对照品，并对其进行了紫外光谱、质谱、红外光谱等结构鉴定。分别考察了水、甲醇、乙醇、95％乙醇4种溶剂以及提取时间对川芎中阿魏酸和藁本内酯提取量的影响。结果表明：水是阿魏酸的最佳提取溶剂，提取时间45min为宜；乙醇是适合提取藁本内酯的溶剂，提取时间75min为宜。以外标法对市售川芎中的阿魏酸与藁本内酯进行了定量分析，二者含量分别是0．15％(m／m)和0．82％(m/m)

High Performance Proton Exchange Membrane Fuel Cells

用全氟磺酸质子交换膜作为质子交换膜燃料电池（ＰＥＭＦＣ） 电解质，简化了水和电解质的管理．本文研究了该燃料电池质子交换膜厚度对电池性能影响；性能最佳的Ｎａｆｉｏｎ １１２ 膜和低铂载量Ｅ＿ＴＥＫ 电极组装的ＰＥＭＦＣ，最大输出功率高达０－９５ Ｗ／ｃｍ２ ；同时考察了电池的能量转换效率、Ｅ＿ＴＥＫ 电极中铂电催化剂利用率和电池的稳定性Proton_exchange membrane fuel cells(PEMFC) using a perfluorosulfonic acid proton exchange membrane as an electrolyte can simplify water and electrolyte management.In this paper,the effects of thickness of PEM on the performance of PEMFC were studied.The Nafion_112 PEM and low platinum loading E_TEK electrode yielded very high power density,of the order of 0.95 W/cm 2.The energy_conversion efficiency,the degree of platinum utilization and stability for PEMFC using Nafion 112 and E_TEK electrode were also investigated.作者联系地址：中国科学院大连化学物理研究所燃料电池工程中心!大连116023,中国科学院大连化学物理研究所燃料电池工程中心!大连116023,中国科学院大连化学物理研究所燃料电池工程中心!大连116023,中国科学院大连化学物理研究所燃料电池工程中心!大连116023,中国科学院大连化学物理研究所燃Author's Address: FC R & D Center,Dalian Inst.of Chem.Phys.,Chinese Academy of Sci.,Dalian 11602

Numerical studies of shock wave interactions with a supersonic turbulent boundary layer in compression corner:Turning angle effects

Direct numerical simulations (DNS) were performed to investigate the interactions of a Mach 2.9 turbulent boundary layer with shock waves of varying strengths in compression corner. The supersonic turbulent boundary layer was triggered by wall blowing-and-suction perturbations. The shock waves were produced by two-dimensional compression corners of 8, 14, 20 and 24 degrees. Compared with previous DNS results and experimental data, the numerical calculations were validated. The effects of shock wave on the boundary layer are studied by both flow visualizations and statistical analysis, and the results show that the intensity of fluctuations is amplified greatly by the shock wave. With the increasing of turning angle, three-dimensionality of separation bubble is significantly enhanced. Based on the statistics and power spectrum of the wall pressure signals, the effect of turning angle on the unsteadiness of shock motion is also studied, and the results show that the shock motions are quite different in the small and the large turning angle cases. The motion in the 8 and 14 cases is characterized by high-frequency and small amplitude, but the low-frequency and large-scale streamwise oscillation is the main feature in the 20 and 24 cases. The effect of turning angle on the turbulence state is analyzed by using the anisotropy of Reynolds stress tensor. The coherent vortex structures are also studied qualitatively. The results indicate that the cane-like streamwise vortexes in the near-wall region are the dominant structure for the small angle cases, while the hairpin vortexes and packets in the outer layer play the leading role in the large angle cases. According to the quantitative analysis of turbulent kinetic energy budgets in the separation region, the effect of turning angle on the transport mechanism is studied. It is found that the influence of shear layer above separation bubble on the mechanism is significant. (C) 2017 Elsevier Ltd. All rights reserved

Normally Off AlGaN/GaN MIS-High-Electron Mobility Transistors Fabricated by Using Low Pressure Chemical Vapor Deposition Si3N4 Gate Dielectric and Standard Fluorine Ion Implantation

This letter presents a fabrication technology of enhancement-mode (E-mode) AlGaN/GaN metal-insulator-semiconductor high-electron mobility transistors (MIS-HEMTs) using 10 keV fluorine ion implantation. An 8 nm low-pressure chemical vapor deposition silicon nitride layer was deposited on the AlGaN as gate dielectric and energy-absorbing layer that slows down the high energy (10 keV) fluorine ions to reduce the implantation damage. The E-mode MIS-HEMTs exhibit a threshold voltage as high as +3.3 V with a maximum drain current over 200 mA/mm (250 mA/mm for depletion-mode MIS-HEMTs) and a high on/off current ratio of 10(9). Meanwhile, the E-mode MIS-HEMT dynamic R-ON is only 1.53 times larger than the static R-ON after off-state V-DS stress of 500 V

2003～2015年CERN植物物候观测数据集

中国生态系统研究网络(Chinese Ecosystem Research Network,CERN)植物物候观测数据集是CERN生态站植物物候观测数据综合集成的产物,包含21个生态站2003～2015年660余个物种的物候观测记录。因木本植物和草本植物观测的物候期不同,本数据集被分为木本子集和草本子集。木本子集主要记录了芽开放期、展叶期、开花始期、开花盛期、果实或者种子成熟期、叶秋季变色期和落叶期等物候信息。草本子集则记录了萌动期、开花期、果实或种子成熟期、种子散布期和黄枯期等物候信息。另外,本数据集还包含生态站代码、年份、样地代码、样地名称、样地类别、植物种名、拉丁名等信息。本数据集可以为环境变化、碳循环、植物对环境变化的响应等方面的研究提供数据支持

Studies on High-Voltage GaN-on-Si MIS-HEMTs Using LPCVD Si3N4 as Gate Dielectric and Passivation Layer

This paper investigates the performance of AlGaN/gallium nitride (GaN) MIS high electron mobility transistors (MIS-HEMTs). The gate dielectric layer and the surface passivation layer are formed by the low-pressure chemical vapor deposition (LPCVD) Si3N4. The LPCVD-Si3N4 MIS-HEMTs exhibit a high breakdown voltage (BV) of 1162 V at I-DS = 1 mu A/mm, a low OFF-state leakage of 7.7 x 10(-12) A/mm, and an excellent ON/OFF-current ratio of similar to 10(11). Compared with the static ON-resistance of 2.88 m Omega . cm(2), the dynamic ON-resistance after high OFF-state drain bias stress at 600 V only increases to 4.89 m Omega . cm(2). The power device figure of merit = BV2/R-ON.sp is calculated to be 469 MW . cm(-2). The LPCVD-Si3N4/GaN interface state density is in the range of (1.4-5.3) x 10(13) eV(-1) cm(-2) extracted by the conventional conductance method. Finally, the gate insulator degradation of GaN-based MIS-HEMTs is analyzed by time-dependent dielectric breakdown test. The lifetime is extrapolated to 0.01% of failures after ten years at 300 K by fitting the data with a power law to a gate voltage of 10.1 V