Control of vortex shedding at moderate Reynolds numbers

The suppression method of vortex shedding from a circular cylinder has been studied experimentally in the Reynolds number range from 300 to 1600. The test is performed in a water channel. The model cylinder is 1 cm in diameter and 38 cm in length. A row of small rods of 0.18 cm in diameter and 1.5 cm in length are perpendicularly connected to the surface of the model cylinder and distributed along the meridian, The distance between the neighboring rods and the angle of attack of the rods can be changed so that the suppression effect on vortex shedding can be adjusted. The results show that vortex shedding can be suppressed effectively if the distance between the neighboring rods is smaller than 3 times and the cylinder diameter and the angle of attack is in the range of 30degreesless than or equal tobeta<90&DEG;.

DPIV and Interferometry Technique for Velocity Field and Concentration Fields Measurement in Crystal Growth

The property of crystal depends seriously on the solution concentration distribution near the growth surface of a crystal. However, the concentration distributions are affected by the diffusion and convection of the solution. In the present experiment, the two methods of optical measurement are used to obtained velocity field and concentration field of NaClO₃ solution. The convection patterns in sodium chlorate (NaClO₃) crystal growth are measured by Digital Particle image Velocimetry (DPIV) technology. The 2-dimentional velocity distributions in the solution of NaClO3 are obtained from experiments. And concentration field are obtained by a Mach-Zehnder interferometer with a phase shift servo system. Interference patterns were recorded directly by a computer via a CCD camera. The evolution of velocity field and concentration field from dissolution to crystallization are visualized clearly. The structures of velocity fields were compared with that of concentration field.

Improved method makes a soft landing of well path

Research and field experience have shown that well-path control is important in many cases, not only to reach the desired coordinates, but also to arrive at the well completion target from the preferred trajectory.

Numerical Analysis of Theoretical Model of the Rf MEMs Switches

An improved electromechanical model of the RF MEMS (radio frequency microelectromechanical systems) switches is introduced, in which the effects of intrinsic residual stress from fabrication processes, axial stress due to stretching of beam, and fringing field are taken into account. Four dimensionless numbers are derived from the governing equation of the developed model. A semi-analytical method is developed to calculate the behavior of the RF MEMS switches. Subsequently the influence of the material and geometry parameters on the behavior of the structure is analyzed and compared, and the corresponding analysis with the dimensionless numbers is conducted too. The quantitative relationship between the presented parameters and the critical pull-in voltage is obtained, and the relative importance of those parameters is given.

菱铁矿热转变过程中岩石磁学性质基本特征

利用吉林大栗子铁矿纯菱铁矿样品，系统测量了菱铁矿在空气环境的的磁化特征，揭示出其饱和曙剩磁（ＳＩＲＭ）、剩磁矫顽力（ＨＣＲ）和居里温度（ＴＣ）随加热温度升高而秘珠系列变化，菱放氧化中准稳定态性矿物磁赤铁矿是中间产物之一，并且具有较高的热稳定性，Ｘ射线衍射和穆斯堡尔效应等分析结果证实了岩石磁学研究所揭示的菱铁矿氧化中磁性矿物转变过程，菱铁矿氧化过程中结晶结构的转变可能会影响其氧化产物的磁性特性。

抗癌药长春新碱及其与微管蛋白相互作用的电化学研究

在0.05 mol/L Tris，0.15 mol/L NaCl溶液中，用吸附伏安法研究长春新碱(VCR)，其峰电位在-1.68 V(vs. Ag/AgCl)，峰电流与1.0*10^{-8}～2.0*10^{-7}mol/L VCR浓度成正比，检测限为7.0*l0^{-9} mol/L，用常规脉冲极谱法、线性扫描和循环伏安法等研究该体系的电化学行为，实验表明，电极还原过程为具有吸附特征的不可逆过程。VCR的吸附符合Frumkin吸附等温式。也研究了VCR与微管蛋白的相互作用。实验表明，VCR与微管蛋白形成一电活性的结合物，这一结合物具有吸附性，且还原过程也为不可逆过程。

Numerical approximation improves well survey calculation

It is now possible to improve the precision of well survey calculations by order of magnitude with numerical approximation.

Although the most precise method of simulating and calculating a wellbore trajectory generally requires more calculation than other, less-accurate methods, the wider use of computers in oil fields now eliminates this as an obstacle.

The results of various calculations show that there is a deviation of more than 10 m among the different methods of calculation for a directional well of 3,000 m.¹ Consequently, it is important to improve the precision and reliability of survey calculation-the fundamental, necessary work of quantitatively monitoring and controlling wellbore trajectories.

固井工程中的流动问题

同井是油气在建过程中的重要工程，一般分下套管和注水泥两个过程．本文结合作者近年来的研究，着重阐述了钻井液、前置液、水泥浆在环形空间中流动的流体力学问题，包括：高温高压下的水泥浆流变性、偏心环形空间中浆液的流动特性、钻井液-前置液和前置液-水泥浆界面的稳定性等，介绍了国内外学者对这些问题的研究进展，提出了今后应深入研究的问题.

Thermal mismatch stress in SiC whisker reinforced aluminium composite: new measurement method by X-ray diffraction

A new X-ray diffraction method for characterising thermal mismatch stress (TMS) in SiC_w–Al composite has been developed. The TMS and thermal mismatch strain (TMSN) in SiC whiskers are considered to be axis symmetrical, and can be calculated by measuring the lattice distortion of the whiskers. Not only the average TMS in whiskers and matrix can be obtained, but the TMS components along longitudinal and radial directions in the SiC whiskers can also be deduced. Experimental results indicate that the TMS in SiC whiskers is compressive, and tensile in the aluminium matrix. The TMS and TMSN components along the longitudinal direction in the SiC whiskers are greater than those along the radial direction for a SiC_w–Al composite quenched at 500°C.

The Heterogeneous Growth of P(3MeTh)--An Ellipsometric Study

Successive thicker P(3MeTh) layers are analysed by ex situ conventional and imaging ellipsometry. Thin films display a smooth surface, are compact and homogeneous while for a growth charge above 20 mC cm(-2) the polymer structure modifies to a still uniform but less dense layer. A two-layer model is used and a mathematical procedure is developed to obtain, simultaneously, from the experimental ellipsometric parameters, Delta and Psi, the thickness and the complex refractive index of P(3MeTh) films grown up to 80 mC cm(-2). Thicker polymer layers are disordered and present a high degree of surface roughness. 

配液结晶法制备溶菌酶蛋白质晶体的生长机理研究

采用配液结晶法制取了溶菌酶蛋白质晶体,使用动态光散射测量了溶液中聚集体的颗粒度几率分布;使用Zeiss显微镜测定了溶菌酶(110)晶面的生长速度.实验表明:随着蛋白质和NaCl浓度的增加,溶液中聚集体的颗粒尺寸也相应增加.随着反应时间的增加,溶菌酶分子在溶液中的聚集反应,逐渐达到平衡;在蛋白质和NaCl浓度较高时,溶菌酶晶体的(110)面生长较快,而在蛋白质和NaCl浓度较低时,该晶面生长较慢.基于二维成核生长机理,从晶体生长动力学理论方程出发,计算了二维成核的形成能a=4.01×10-8J?cm-2.

微米尺度结构最大抗扭强度的在线测试和研究

提出了一种新型的测试结构，对面积为微米量级下键合的最大抗扭强度进行了测试) 实验设计一系列的单晶硅悬臂梁结构测试键合面积在微米量级时的最大剪切力，键合面为常用的矩形其边长从*!+ 到!#$!+，并根据实际移动距离计算得出的最大剪切力) 并实验实际得出最大剪切扭矩和相应的键合面积的曲线，以及最大扭转剪切破坏应力与悬臂梁加载距离的关系，并针对*$!+, *$!+ 的矩形键合结构进行了加载和位移的重复性实验测量，两次测量结果符合较好) 微电子机械系统（+-./0121.3/0+1.456-.52 78731+，9:9;）器件的设计人员可以根据结论曲线，针对所需的抗扭强度设计相应的键合面积，为9:9; 器件工艺的在线定量测试与设计提供参考)

Energy Conversion in Shape Memory Alloy Heat Engine Part I: Theory

Shape Memory Alloy (SMA) can be easily deformed to a new shape by applying a small external load at low temperature, and then recovers its original configuration upon heating. This unique shape memory phenomenon has inspired many novel designs. SMA based heat engine is one among them. SMA heat engine is an environment-friendly alternative to extract mechanical energy from low-grade energies, for instance, warm wastewater, geothermal energy, solar thermal energy, etc. The aim of this paper is to present an applicable theoretical model for simulation of SMA-based heat engines. First, a micro-mechanical constitutive model is derived for SMAs. The volume fractions of austenite and martensite variants are chosen as internal variables to describe the evolution of microstructure in SMA upon phase transition. Subsequently, the energy equation is derived based on the first thermodynamic law and the previous SMA model. From Fourier’s law of heat conduction and Newton’s law of cooling, both differential and integral forms of energy conversion equation are obtained.

重力对异向聚集过程影响的探讨

自90年代初,分散体系聚集过程的微重力研究开始受到重视,并有一系列论文发表[1－4].Folkersma[3,4]等人在最近发表的文章中,公布了他们的最新研究结果.在探空火箭实现的微重力条件下,他们发现聚集速率要比地面实验快11倍多.为了解释这一现象,他们把重力的影响分为两部分,即沉降和自然对流.用密度匹配法,检验了在无沉降时的聚集过程.得到的结果是,聚集速率在无重力沉降影响时会比有沉降时快2.7倍.即便如此,微重力实验的聚集速率仍高出4.2倍.他们推断,这一巨大差异是由在地面上无法避免的自然对流造成的.

Deformation behavior and microstructure effect in 2124Al/SiCp composite

Dynamic compression tests were performed by means of a Split Hopkinson Pressure Bar (SHPB). Test materials were 2124Al alloys reinforced with 17% volume fraction of 3, 13 and 37 μm SiC particles, respectively. Under strain rate ε = 2100 l/s, SiC particles have a strong effect on σ_0.2 of the composites and the σ_0.2 increases with different SiC particle size in the following order: 2124Al-alloy → 124Al/SiC_p (37 μm) → 2124Al/SiC_p (13 μm) → 2124Al/SiC_p (3 μm), and the strain hardening of the composites depends mainly on the strain hardening of matrix, 2124A1 alloy. The results of dimensional analysis present that the flow stress of these composites not only depends on the property of reinforcement and matrix but also relates to the microstructure scale, matrix grain size, reinforcement size, the distance between reinforcements and dislocations in matrix. The normalized flow stress here is a function of inverse power of the edge-edge particle spacing, dislocation density and matrix grain size. Close-up observation shows that, in the composite containing SiC particles (3 μm), localized deformation formed readily comparing with other materials under the same loading condition. Microscopic observations indicate that different plastic flow patterns occur within the matrix due to the presence of hard particles with different sizes.