Cathode plasma electrolytic deposition of Al2O3 coatings doped with SiC particles

Semiconductor particles doped Al₂O₃ coatings were prepared by cathode plasma electrolytic deposition in Al(NO₃)₃ electrolyte dispersed with SiC micro- and nano-particles (average particle sizes of 0.5–1.7?µm and 40?nm respectively). The effects of the concentrations and particle sizes of the SiC on the microstructures and tribological performances of the composite coatings were studied. In comparison with the case of dispersing with SiC microparticles, the dispersion of SiC nanoparticles in the coatings was more uniform. When the concentration of SiC nanoparticles was 5?g/L, the surface roughness of the composite coating was reduced by 63%, compared with that of the unmodified coating. Friction results demonstrated that the addition of 5?g/L SiC nanoparticles reduced the friction coefficient from 0.60 to 0.38 and decreased the wear volume under dry friction. The current density and bath voltage were measured to analyze the effects of SiC particles on the deposition process. The results showed that the SiC particles could alter the electrical behavior of the coatings during the deposition process, weaken the bombardment of the plasma, and improve the structures of the coatings.     

基于SoC的多轴驱控一体化平台设计

随着FPGA技术和电力电机技术的发展,FPGA+ARM的集成方式已经成为FPGA的发展方向.针对一体化多轴运动控制与驱动的特点,选用了集成双核ARM CPU与FPGA结合的Xilinx Zynq-7020全可编程System-on-chip(SoC)作为硬件平台,一个ARM CPU完成多轴的位置环、速度环和电流环的算法以及多轴轨迹生成,能同时完成伺服高级算法如谐振等,另一个ARM CPU完成交互功能,发挥FPGA高速运算的功能,完成6轴电流环流水线控制以及双采样双更新电流环算法.提高了系统整体带宽,实现多轴ns级同步精度以实现更精确的位置轨迹,驱控一体内部数据通过共享内存以及高速内部总线的方式进行交换,其传输速度更快、传输信息更加丰富.     

基于力测量法研究滑石的晶面各向异性

层状硅酸盐矿物滑石在解离时会形成具有明显性质差异的2种表面，滑石的晶面各向异性会导致矿物不同表面表现出不同的润湿性以及不同的电荷密度。通过原子力显微镜力（AFM）曲线测量以及经典DLVO理论计算，对滑石的非极性面和极性面进行深入研究，首先利用AFM力曲线测量和计算，得到不同pH值时氮化硅的电位值，利用AFM直接力测量法对符合粗糙度要求的滑石非极性面和极性面样品在10 mmol/L的KCl溶液中进行测量，得到不同pH值环境下的力曲线，通过DLVO理论拟合计算得到滑石非极性面和极性面的表面电位值。滑石的非极性面电位值在研究的pH范围内一直为负，且恒定，极性面电位值随pH升高而降低，零电点出现在pH=7.6左右。将计算得到的滑石表面电位与氮化硅之间的作用力拟合曲线与实际测得的作用力进行对比发现，计算值与测量值基本一致，拟合度较高。     

磷酸高效分解磷矿实验研究

为改进湿法磷酸生产工艺,提高副产石膏的品质,减少湿法磷酸固体副产物磷石膏堆存产生的经济和环保压力,进行了磷酸分解磷矿制磷酸的实验研究。采用贵州某磷矿为主要原料,研究了湿法磷酸预分解磷矿的反应条件。通过单因素实验确定了湿法磷酸分解磷矿最优反应条件：反应温度为75 ℃,磷酸与磷矿的质量比（液固比）为9,反应时间为3 h,磷酸质量分数为30%（以五氧化二磷计）。在此条件下,磷矿的分解率为98.62%。     

Strain hardening behaviors and mechanisms of polyurethane under various strain rate loading

The uniaxial tension experiments are performed on thermoplastic polyurethane to investigate its mechanical behaviors and related potential mechanisms, and the loading strain rate is designing to be wide ranging from 0.0001 to 1 s⁻¹. It is found that the polyurethane presents an obvious rate-dependence, and the stress strain curves share distinct strain hardening characteristics under the investigated strain rates. Furthermore, the strain hardening ratios are sharing nearly same trends and appear to be influenced by both strain rate and the induced adiabatic heating. Besides, the ratio is also strain-dependent on previous loading history. Then, a two-dimension unit cell model is built to investigate potential equivalent mechanisms, of which the hard phase as inclusion is equivalent with crystallization zone, crosslinking sites, and so forth. The simulation results facilitate to explain the distinct strain hardening ratios, even for the matrix from the extrapolated curves under super-low strain rate loading. Finally, the analogic mechanisms of equivalent hard inclusions are proposed, which can reasonably explain the strain rate- and strain-dependence characteristics of polyurethane mechanical behaviors.     

基于统计软件R的安全壳泄漏率试验数据有效性分析

安全壳泄漏率计算过程中，最重要的环节是以不同时刻测量数据对时间进行线性回归分析。对回归的显著性检验以及方差分析是评价试验结果有效性的重要手段。本文基于统计软件R对某电厂调试阶段安全壳泄漏率试验的数据进行分析，通过对线性回归模型的独立性、正态性和异方差性检验以及极端样本点的剔除等方式，探讨泄漏率计算前的回归诊断对计算结果可靠性的影响。通过回归诊断的实例分析发现，在安全壳泄漏率计算的数据样本中，可能存在自相关、非正态和异方差性等问题影响回归结果，进而影响泄漏率的最终结果。因此，在计算泄漏率结果时，须通过回归诊断方法评价数据的有效性，对不能通过检验的样本应通过适当方法对最终结果进行修正。      

Assembly of a DNA Origami Chinese Knot by Only 15% of the Staple Strands

As a giant leap in DNA self-assembly, DNA origami has exhibited an unprecedented ability to construct nanostructures with arbitrary shapes and sizes. In typical DNA origami, hundreds of short DNA staple strands fold a long, single-stranded (ss) DNA scaffold cooperatively into designed nanostructures. However, large numbers of DNA strands are expensive and would hinder applications such as pharmaceutical investigations because of the complicated components. Therefore, one challenge is how to reduce the number of staple strands needed to construct DNA origami. For a DNA origami structure, the scale-free folding pattern of the scaffold strand is determined by staple strands at the branching vertexes. Simple duplex regions help to define the size-related features of the origami geometry. In this study, we hypothesized that a scaffold strand can be correctly folded into a designed topology by using only staple strands involved in branching vertexes. After assembly, any remaining, flexible, single-stranded regions of the scaffold could be converted into rigid duplexes by DNA polymerase to achieve the designed geometric structures. To demonstrate the concept, we used only 18 staple strands (covering 15 % of the scaffold strand) to assemble a porous DNA nanostructure, which was visualized by atomic force microscopy (AFM). This study helps understanding of the role of cooperativity in origami folding, and provides a cost-effective approach for small-scale prototyping DNA origami.     

多肽N端修饰方法研究进展

多肽是源于生物体内的一类重要的生物活性物质,但由于稳定性差等原因,大大限制了其应用。通过对多肽进行结构修饰,可以改变其理化性质,进而提高其稳定性及生物活性。综述了近年来多肽N端修饰方法的研究进展,包括乙酰化、PEG(聚乙二醇)修饰、荧光试剂修饰、多肽N端亲水性基团修饰、NCL及EPL连接反应等,介绍了2-氨基辛酸、丁烯酶1、N-脒基-焦谷氨酰苯丙氨酸、N-terminal caps等多肽N端修饰实例。     

红岭矿18线南西翼通风系统技术改造

针对矿山18线南西翼矿体开采过程中存在的通风系统不完善、风量欠缺、污风无法及时排出等问题，运用风压平衡原理、网络优化技术、机站优化技术以及计算机网络模拟技术展开研究，拟定了3种可行的通风方案。经技术经济比较，确定了新掘18线905～855 m回风井（1.5 m），保留该井905 m 水平回风机站，并在855 m 水平新设1台K45 6 №12风机（18.5 kW）方案。数值模拟结果表明：18线南西翼通风系统总风量达到20.5 m3/s，井下风流的可调性和稳定性增强，为矿山的安全生产提供了有力保障。