Friction Properties of Bio-mimetic Nano-fibrillar Arrays

Nano-fibrillar arrays are fabricated using polystyrene materials. The average diameter of each fiber is about 300 nm. Experiments show that such a fibrillar surface possesses a relatively hydrophobie feature with a water contact angle of 142°. Nanoscale friction properties are mainly focused on. It is found that the friction force of polystyrene nano-fibrillar surfaces is obviously enhanced in contrast to polystyrene smooth surfaces. The apparent coefficient of friction increases with the applied load, but is independent of the scanning speed. An interesting observation is that the friction force increases almost linearly with the real contact area, which abides by the fundamental Bowden-Tabor law of nano-seale friction.     

Derivative of Electron Density in Non-Equilibrium Green's Function Technique and Its Application to Boost Performance of Convergence

The non-equilibrium Green＇s function （NEGF） technique provides a solid foundation for the development of quantum mechanical simulators. However, the convergence is always of great concern. We present a general analytical formalism to acquire the accurate derivative of electron density with respect to electrical potential in the framework of NEGF. This formalism not only provides physical insight on non-local quantum phenomena in device simulation, but also can be used to set up a new scheme in solving the Poisson equation to boost the performance of convergence when the NEGF and Poisson equations are solved self-consistently. This method is illustrated by a simple one-dimensional example of an N＋＋ N＋ N＋＋ resistor. The total simulation time and iteration number are largely reduced.     

白蛋白酸致变性的动态激光散斑研究

利用动态激光散斑的方法研究了白蛋白的酸致变性过程。首先,利用动态散斑理论模拟生成了动态散斑序列图;然后,利用模拟和实验散斑图的时间序列散斑图及其灰度共生矩阵对白蛋白的酸致变性过程进行了分析;接着,又利用灰度共生矩阵的惯性矩和不同阶段的四幅散斑图的平均对比度图对该过程进行了更深入的研究。理论模拟和实验研究结果表明,在白蛋白酸致变性过程中,胶体溶液中的蛋白质微粒的运动由剧烈逐渐变得缓慢;同时,微粒数量减少而微粒尺寸增加。研究表明,动态激光散斑方法是一种实时、快速、有效的研究白蛋白变性过程的新手段。     

Design and test of a Multi-gap Resistive Plate Chamber with Long readout-strip （LMRPC）

A new kind （two end readout） of Multi-gap Resistive Plate Chamber with long readout-strip （LMRPC） is developed to be used at the large-area Muon Telescope Detector （MTD） at mid-rapidity at RHIC/STAR experiment for Time-of-Flight （TOF） measurement. The LMRPC has an active area of 87 cm× 17 cm, 10 gas gaps of 250 μm arranged in 2 stacks, with readout strips of 2.5 cm wide and 90 cm long. The considerations in LMRPC design related to its performance are discussed in this paper. The cosmic ray test results of a prototype LMRPC show a detection efficiency 〉95% and the time resolution -70 ps.     

X-ray beam hardening correction for measuring density in linear accelerator industrial computed tomography

Due to X-ray attenuation being approximately proportional to material density,it is possible to measure the inner density through Industrial Computed Tomography（ICT） images accurately. In practice,however,a number of factors including the non-linear effects of beam hardening and diffuse scattered radiation complicate the quantitative measurement of density variations in materials. This paper is based on the linearization method of beam hardening correction,and uses polynomial fitting coecient which is obtained by the curvature of iron polychromatic beam data to fit other materials. Through theoretical deduction,the paper proves that the density measure error is less than 2% if using pre-filters to make the spectrum of linear accelerator range mainly 0.3 MeV to 3 MeV. Experiment had been set up at an ICT system with a 9 MeV electron linear accelerator. The result is satisfactory. This technique makes the beam hardening correction easy and simple,and it is valuable for measuring the ICT density and making use of the CT images to recognize materials.     

分析北京城市污泥中铅砷镉形态浓度的ICP-MS

城市污泥中重金属的难降解和高毒性限制了污泥的资源化利用.以北京G和Q污水处理厂的压滤出厂污泥为实验材料,采用BCR三步浸提法对污泥中铅砷镉Pb,As,Cd的三种形态进行提取,以HNO3-HClO4进行全量消解,利用ICP-MS检测Pb,As,Cd的全量和各形态的含量,从而为北京城市污泥的资源开发研究提供基础数据.实验结果表明,北京城市污泥中Pb和Cd含量比上世纪末明显降低:其中,G污泥中Pb,As,Cd的全量(干重)分别为19.60,37.96和1.34 mg·kg-1,而Q污泥中分别为19.58,23.46和2.30 mg·kg-1;两种污泥中Pb含量相差甚微,G污泥中As明显高于Q污泥,而Cd则显著低于后者;两种污泥中相应金属的三种形态的变化趋势基本一致:Pb与As以HAc酸溶态为主,H2O2可氧化态最少;而Cd主要以NH2OH-HCl可还原态存在,HAc酸溶态最少.三种重金属中生物毒性大的形态均占70%以上.     

6H-SiC的A_1(LO)拉曼峰低温温度特性研究

对6H-SiC单品体材料进行了从80到320 K的低温变温拉曼光谱测量,从实验得到的谱图上指认了部分6H-SiC的折叠拉曼峰,重点利用三声子模型和四声子模型分析了A1(LO)光学声子模峰位和线宽在低温下随温度的变化特性.实验发现,随着温度降低,LO声子模谱峰中心向高波数移动,线宽减小;同时发现当温度低于160 K时,无论足谱峰中心位置还是线宽的变化都趋于平缓,这是在常温和高温下观察不到的,说明在160 K以下时A1(LO)谱线线宽是由声子本身的性质决定,温度对线宽的影响几乎可忽略;理论拟合表明,四声子模型更能与实验数据相符,三次、四次非谐振动共同作用,前者是主要过程;温度越低,A1(LO)光学声子寿命越长,这是由于原子热运动的剧烈程度随温度降低而下降,声子弛豫减弱.     

基于ARM技术的嵌入式OCT成像系统研究

分析了光谱光学相干层成像的基本原理,并基于ARM9内核的嵌入式微处理器S3C2443和当前主流嵌入式的WINCE实时多任务操作系统,提出了一套用于检测人体胃肠道病变的光谱光学相干层内窥成像系统的研制方案。从硬件和软件两个方面,详细介绍了系统的搭建过程,给出了整个系统框架图和软件运行流程图,并通过旋转扫描实验获得三层盖玻片的实物图,实验结果表明该嵌入式光学相干层成像系统是可行的。     

以吐温-80为增溶剂催化光度法测定痕量钒(Ⅴ)

本文报道了在硫酸性介质中 ,以吐温 - 80为增溶剂 ,溴酸钾氧化姜黄催化光度法测定痕量钒 ( )的新体系。方法的检出限为 2 .6× 10 -3mg· L-1;相对标准偏差为 2 .7% (n=9) ,线性范围为 0 .0 12— 0 .0 4 0mg· L-1。可用于测定水样中痕量钒 ( ) ,结果满意     

电感耦合等离子体发射光谱法同时测定涂料中的Pb、Cd、Cr和Hg

研究了电感耦合等离子体发射光谱法测定涂料中的重金属Pb，Cd，Cr和Hg，确定了测定涂料中的重金属Pb，Cd，Cr和Hg的最佳条件。加标回收试验和实际样品测定结果表明，方法的回收率和精密度分别在99.5％-110．0％和0．95％-1．98％范围，该方法快速、准确、可靠，各元素的检出限能满足涂料安全标准，适用于涂料的日常检验。