Experimental investigation on the plasma morphology of ablative pulsed plasma thruster with tongue-shaped and flared electrodes

Ablative pulsed plasma thrusters(APPTs) are considered as an attractive propulsion option for station-keeping and drag makeup purposes for mass-and power-limited satellites. In order to understand the physical mechanism of APPTs, high-speed camera and optical emission spectroscopy are utilized to investigate the plasma characteristics including the spatial distribution and composition between the electrodes. The plume images and spectra at different times and positions are experimentally recorded, and the spatial distribution, composition, and trajectory of plasmas can be concluded through analyzing them. With the increase of the distance from the ablation surface, two clusters of plasmas near the anode and cathode meet downstream,and the species and density of plasmas tend to be uniform.     

Characterization of cloud cover with a smartphone camera

A smartphone sky camera and associated image analysis algorithm has been developed and validated to determine total cloud cover and the percentage of thick and thin clouds using supervised image classification for a range of cloud types, cloud cover from 4% to 98%, and solar zenith angles between 6° and 49°. Additionally, this system provides the percentage of total, thick, and thin clouds in proximity to the solar disc. The measurement errors were comparable to those associated with values obtained by commercial sky camera systems. The benefits of increasing the availability of cloud fraction measurements include the potential to develop improved local ultraviolet indices and weather forecasts and to provide a better understanding of cloud patterns required for the generation of solar energy.     

基于FPGA的高速峰值检测

针对研发数字多道的实际需求,提出了一种基于FPGA的高速峰值检测技术,并且采用ARM+FPGA的架构实现了基于该技术的数字多道系统。通过Modelsim仿真分析了FPGA峰值检测算法的理论,该算法可精确获取高斯信号的最值并获得幅度值。最后通过CZT探测器进行~(241)Am源实测γ射线能谱,实验结果表明该峰值检测算法及数字多道系统设计可准确并且快速获得能谱图。通过合理设置峰值检测算法的高低阈值,可以测试不同基线值的前放信号。     

Fit‐first to be tied

This poem summarizes the fit‐first method of camera evaluation described in Jim Worthey's “Applications of vectorial color.” The algorithm works with the locus of unit monochromats (LUM) in camera and CIE color‐matching spaces. © 2011 Wiley Periodicals, Inc. Col Res Appl, 2011;     

Spider orb webs rely on radial threads to absorb prey kinetic energy

The kinetic energy of flying insect prey is a formidable challenge for orb-weaving spiders. These spiders construct two-dimensional, round webs from a combination of stiff, strong radial silk and highly elastic, glue-coated capture spirals. Orb webs must first stop the flight of insect prey and then retain those insects long enough to be subdued by the spiders. Consequently, spider silks rank among the toughest known biomaterials. The large number of silk threads composing a web suggests that aerodynamic dissipation may also play an important role in stopping prey. Here, we quantify energy dissipation in orb webs spun by diverse species of spiders using data derived from high-speed videos of web deformation under prey impact. By integrating video data with material testing of silks, we compare the relative contributions of radial silk, the capture spiral and aerodynamic dissipation. Radial silk dominated energy absorption in all webs, with the potential to account for approximately 100 per cent of the work of stopping prey in larger webs. The most generous estimates for the roles of capture spirals and aerodynamic dissipation show that they rarely contribute more than 30 per cent and 10 per cent of the total work of stopping prey, respectively, and then only for smaller orb webs. The reliance of spider orb webs upon internal energy absorption by radial threads for prey capture suggests that the material properties of the capture spirals are largely unconstrained by the selective pressures of stopping prey and can instead evolve freely in response to alternative functional constraints such as adhering to prey.     

12bit 800MSPS电流舵结构的高速DAC设计

本文设计了一个分辨率为12位，采样频率为800MHz的高速电流舵结构DAC。该设计基于TSMC0．18umCMOS工艺，采用了二进制码控制和温度计码译码控制相结合的方式，从而在降低DNL误差和减小毛刺的同时，又能实现较小的芯片面积和功耗。为达到高的精度和高的转换速度，该设计在系统结构、电路结构以及芯片版图等方面都做了优化。     

我国高铁建设融资模式再探索

作为公共基础设施建设的重要组成部分,高铁建设具有自然垄断性、地方公共产品性、成本积聚性以及收益长期性等经济属性。高铁建设一般采取政府投资为主、BOT项目融资为辅的融资模式,而政府投资和BOT项目融资模式都存在一定的限制,为满足高铁建设的巨大资金需求,需要探索和尝试更可行、合理的融资模式,制定支持性政策和配套制度。     

Purification and Characterization of Aporphine Alkaloids from Leaves of Nelumbo nucifera Gaertn and Their Effects on Glucose Consumption in 3T3-L1 Adipocytes

Aporphine alkaloids from the leaves of Nelumbo nucifera Gaertn are substances of great interest because of their important pharmacological activities, particularly anti-diabetic, anti-obesity, anti-hyperlipidemic, anti-oxidant, and anti-HIV’s activities. In order to produce large amounts of pure alkaloid for research purposes, a novel method using high-speed counter-current chromatography (HSCCC) was developed. Without any initial cleanup steps, four main aporphine alkaloids, including 2-hydroxy-1-methoxyaporphine, pronuciferine, nuciferine and roemerine were successfully purified from the crude extract by HSCCC in one step. The separation was performed with a simple two-phase solvent system composed of n-hexane-ethyl acetate-methanol-acetonitrile-water (5:3:3:2.5:5, v/v/v/v/v). In each operation, 100 mg crude extracts was separated and yielded 6.3 mg of 2-hydroxy-1-methoxyaporphine (95.1% purity), 1.1 mg of pronuciferine (96.8% purity), 8.5 mg of nuciferine (98.9% purity), and 2.7 mg of roemerine (97.4%) respectively. The chemical structure of four aporphine alkaloids are identified by means of electrospray ionization MS (ESI-MS) and nuclear magnetic resonance (NMR) analysis. Moreover, the effects of four separated aporphine alkaloids on insulin-stimulated glucose consumption were examined in 3T3-L1 adipocytes. The results showed that 2-hydroxy-1-methoxyaporphine and pronuciferine increased the glucose consumption significantly as rosiglitazone did.     

基于相机的转台稳定性检测方法研究

高精密转台常用于高精度测量仪器的性能测试,或作为激光扫描仪的稳定平台使用,而转台的稳定性直接影响仪器的测量精度.提出一种利用数码相机对转台稳定性进行标定的方法,在转台运动时,安装在转台上的相机连续获取相片,基于摄影测量原理,计算相机的空间位置和姿态,从而确定转台的运动轨迹.实验结果表明,该方法可以有效地检测转台运动的稳定性.     

航空相机检测仪系统的设计与实现

航空相机是一种重要的机载光电设备，在航空对地测绘等领域有着较为广泛的应用，为方便、直观地对航空相机进行地面检测，设计和实现了一种配套某型航空相机的检测仪系统。根据航空相机地面保障设备任务书和相机与地保设备通讯协议，给出了检测仪系统的功能需求。根据相机的接口要求和系统计算能力的要求，设计了检测仪系统的硬件方案。根据软件部分的功能需求，提出了一种新的分层架构，同时详细论述了软件系统的关键技术，描述了程序的运行流程，给出了检测仪系统的软件设计方案，并在VC6.0环境下实现了检测仪软件系统。针对检测仪的工作方式，设计了测试流程，并根据流程对检测仪进行了详尽的测试，经多次测试，检测仪工作正常。测试结果表明，检测仪系统满足了对其功能的全部要求，运行稳定，操作简便，显示直观，可以应用于航空相机地面保障任务。