Analysis of a Rubber Cone Tensioned by a Concentrated Force

Using the constitutive equation of a rubber-like materials given by Gao (1997), this paper investigates the problem of a cone under tension of a concentrated force at its apex. Under consideration is the axial-symmetry case and the large strain is taken into account. The stress strain fields near the apex are obtained by both asymptotic analysis and finite element calculation. The two results are consistent well. When the cone angle is 180 degrees, the solution becomes that of non-linear Boussinesq's problem for tension case.

Influence of Indenter Tip Roundness on Hardness Behavior in Nanoindentation

In this paper. the effect of indenter tip roundness on hardness behavior for two typical elastic perfectly plastic materials is studied by means of finite element simulation. A rigid conical indenter of semi apex angle 70.3 degrees fitted smoothly with a spherical tip is employed. It is shown that as the indentation depth increases hardness first rises from zero, reaches a maximum and then decreases slowly approaching asymptotically the limiting value equal to that due to a conical indenter of ideally sharp tip. The range within which hardness varies appreciably is comparable to the radius of the indenter tip. The difference between the maximum value and the limiting value depends on the yield stress over the Young's modulus ratio. The smaller this ratio the greater the difference is. Numerical simulation also provides an opportunity for checking the accuracy and limitations of the widely used Oliver-Pharr method.

Analysis of Behaviors of Shock Focusing in the Inner Cavities of Double Wedge and Cone

The mechanisms of shock focusing in inner cavities of double wedge and cone are compared with that of traditional curved-surface shock focusing. The results show that there are many high temperature regions just behind shock surface which appear in two place alternately, one is near the surface of wall and the other is near the centerline. Also, changes in temperature, pressure, energy and power of the high temperature regions were analyzed and the results show that energy and power per unit volume increase, but total energy and power in the high temperature regions decrease during the process of shock moving forward the apex of double wedge or cone.

Laser pulse induced bumps in chalcogenide phase change films

Formation of bumps in chalcogenide phase change thin films during the laser writing process is theoretically and experimentally investigated. The process involves basically fast heating and quenching stages. Circular bumps are formed after cooling, and the shape and size of the bumps depend on various parameters such as temperatures, laser power, beam size, laser pulse duration, etc. In extreme cases, holes are formed at the apex of the bumps. To understand the bumps and their formation is of great interest for data storage. In the present work, a theoretical model is established for the formation process, and the geometric characters of the formed bumps can be analytically and quantitatively evaluated from various parameters involved in the formation. Simulations based on the analytic solution are carried out taking Ag8In14Sb55Te23 as an example. The results are verified with experimental observations of the bumps. (C) 2008 American Institute of Physics.

立方反射镜失调特性的研究

结合理想坐标系下立方镜镜面微小倾斜后其三个平面法线坐标，利用刚体微量转动的反射法线向量公式，获得非理想立方镜反射矩阵；为了研究在光斜入射时镜面倾斜对出射光方向的影响，利用立方镜绕顶点旋转等效于光斜入射的方法，计算出光束夹角δ与单一镜面偏差角ε和立方镜旋转角θ之间的关系式；对于理想情况下的立方镜，利用几何光学可以证明出射光与入射光不但平行，而且过顶点作任意截面交于两光线所得的两个交点关于顶点对称，从而计算出立方镜绕顶点以外任意轴旋转造成出射光束相对原出射光的偏移量与旋转角关系式，理论计算值与实验数据吻合得很

晚粳水稻生长点在光周期反应中的地位

光敏核不育水稻晚粳农垦58S具有长日下不育，短日照下可育的特点。为了确定突变体NK58S突变基因的作用器官及功能。我们设计了一系列光周期处理实验，并对不同光周期处理的生长点或幼穗进行细胞学及细胞化学观察，同时选择光调节基因对其在NK58S上表达特性进行分析。材料选用突变体NK58S，及其野生型NK58S，和它的回复突变体NK58Sr，加两个籼稻品种W6154S及珍汕97，共设计十三个不同的光周期处理。根据试验分析我们发现： 第一，温度对结实率的影响，NK58S，NK58及NK58Sr表现一致，没有发现对NK58S有特异作用的温度效应。三个粳稻品种均因幼穗分化前的长日处理延迟抽穗，而使各处理粳稻品种处于不同环境条件下，引起结实率的变化。 第二，温度对花粉育性的影响较对结实率的影响小。因而用花粉育性进行不育材料的鉴定和比较较可靠。 第三，光周期处理引起生长点原套及原体组织的一定的细胞学变化，但三个粳稻品种间没有差异。生长点周围及其下节部的淀粉积累的变化，三个粳稻品种一致，没有发现不育与可育材料之间的差异。一直处于长日处理条件下的三个粳稻材料，表现出NK58S突变体生长点周围及节部淀粉积累少于NK58，和NK58Sr。 第四，就总RNA而言，三个粳稻品种在光周期处理下各样品绝对量不同，但不同光周期处理，三个粳稻品种反应一致。不同发育时期叶片内光调节基因表达丰度与总RNA水平不一致，不同基因表现出因不同发育阶段而不同的转录特点。在所选三个光调节基因的Northern印迹分析结果没有发现三个晚粳稻品种之间的差异。 第五，幼穗分化开始后的光周期反应不是农垦58S的花粉育性所特有，对NK58，及NK58Sr也有作用。光周期处理还会影响幼穗其它方面的发育。短日处理下农垦58S的育性恢复也只有农垦58的一半。 总之，我们的试验结果使我们得出光周期作用产生的信息在植物不同发育阶段一致。不同发育时期的生长点对来自该信息的作用产生不同的反应。光敏核不育的突变表型体现在生长点的变化上。突变基因的功能是感受来自不同环境因素所产生的胁迫作用。

Mechanism on Effect of Surface Plasmons Coupling with InGaN/GaN Quantum Wells: Enhancement and Suppression of Photoluminescence Intensity

The photoluminescence (PL) intensity enhancement and suppression mechanism on surface plasmons (SPs) coupling with InGaN/GaN quantum wells (QWs) have been systematically studied. The SP-QW coupling behaviors in the areas of GaN cap layer coated with silver thin film were compared at different temperatures and excitation powers. It is found that the internal quantum efficiency (IQE) of the light emitting diodes (LEDs) varies with temperature and excitation power, which in turn results in anomalous emission enhancement and suppression tendency related to SP-QW coupling. The observation is explained by the balance between the extraction efficiency of SPs and the IQE of LEDs

Investigations on V-defects in quaternary AlInGaN epilayers

The characteristics of V-defects in quaternary AlInGaN epilayers and their correlation with fluctuations of the In distribution are investigated. The geometric size of the V-defects is found to depend on the In composition of the alloy. The V-defects are nucleated within the AlInGaN layer and associated with threading dislocations. Line scan cathodoluminescence (CL) shows a redshift of the emission peak and an increase of the half width of the CL spectra as the electron beam approaches the apex of the V-defect. The total redshift decreases with decreasing In mole fraction in the alloy samples. Although the strain reduction may partially contribute to the CL redshift, indium segregation is suggested to be responsible for the V-defect formation and has a main influence on the respective optical properties. (C) 2004 American Institute Of Physics.

Cathodoluminescence and Raman research of V-shape inverted pyramid in HVPE grown GaN film

Thick GaN films with high quality have been grown on (0001) sapphire substrate in a home-made vertical HVPE reactor. Micron-size hexagonal pits with inverted pyramid shape appear on the film surface, which have six triangular {10-11} facets. These I {10-11} facets show strong luminescence emission and are characteristic of doped n-type materials. Broad red emission is suppressed in {10-11} facets and is only found at the flat region out of the pit, which is related with the decreasing defects on {10-11} facets. Low CL emission intensity is observed at the apex of V-shape pits due to the enhanced nonradiative recombination. Raman spectra show that there are higher carrier concentration and low strain in the pit in comparison to the flat region out of the pit. The strain relaxation may be the main mechanism of the V-shape pits formation on the GaN film surface. (c) 2006 Elsevier B.V. All rights reserved.

Effect of Si overgrowth on the structural and luminescence properties of Ge islands on Si(100)

The effect of Si overgrowth on the structural and luminescence properties of strained Ge layer grown on Si(1 0 0) is studied. Capping Si leads to the dissolution of Ge island apex and reduced island height. The structural changes in island shape, especially in chemical composition during Si overgrowth have a large effect on the PL properties. The integrated PL intensity of Ge layer increases and there are large blue shifts in peak energies after capping Si. The PL spectra from buried Ge layer are consistent with type-II band alignment in SiGe/Si. We show that the PL properties from buried Ge layer may be tailored by modifying the cap layer growth conditions as well as post-growth annealing. (C) 1999 Elsevier Science B.V. All rights reserved.

Introduction to Molecular Analysis of Ectomycorrhizal Communities

A number of methods are available for those researchers considering the addition of molecular analyses of ectomycorrhizal (EcM) fungi to their research projects and weighing the various approaches they might take. Analyzing natural EcM fungal communities has traditionally been a highly skilled, time-consuming process relying heavily on exacting morphological characterization of EcM root tips. Increasingly powerful molecular methods for analyzing EcM communities make this area of research available to a much wider range of researchers. Ecologists can gain from the body of work characterizing EcM while avoiding the requirement for exceptional expertise by carefully combining elements of traditional methods with the more recent molecular approaches. A cursory morphological analysis can yield a traditional quantification of EcM fungi based on tip numbers, a unit with functional and historical significance. Ectomycorrhizal root DNA extracts may then be analyzed with molecular methods widely used for characterizing microbiota. These range from methods applicable only to the simple mixes resulting from careful morphotyping, to community-oriented methods that identify many types in mixed samples as well as provide an estimate of their relative abundances. Extramatrical hyphae in bulk soil can also be more effectively studied, extending characterization of EcM fungal communities beyond the rhizoplane. The trend toward techniques permitting larger sample sets without prohibitive labor and time requirements will also permit us to more frequently address the issues of spatial and temporal variability and better characterize the roles of EcM fungi at multiple scales.

Active site structure of NO decomposition on perovskite(-like) oxides: An investigation from experiment and density functional theory

Active site structure for NO decomposition carried out on perovskite-like oxides were discussed based on the N-2 yield measured from LaSrNi1-x,AlxO4 with different B-site cations and from La2-ySryCuO4 with different crystal phases. Results show that the active site contains two oxygen vacancies, two transition metals, and one lattice-oxygen, with the oxygen vacancy locating on the apex of MO6 octahedron, and the lattice oxygen locating between the two transition metals (i.e., M-O-M plane). Density functional theory (DFT) analysis to the structure shows that this new active site is the most active structure for NO adsorbing, and hence, for NO decomposition. The similar trend of the relative energies that are required for the formation of oxygen vacancies with f form (calculated from DFT), the amount of oxygen vacancies, and the activities (N-2 yield) certifies this result further.

A two-dimensional molybdenum (V) phosphate with covalently bonded transition metal coordination complexes: hydrothermal synthesis and structure characterization of Na-2[{Mn(phen)(2)(H2O)}{Mn(phen)(2)}(3){Mn (Mo12O24)-O-V (HPO4)(6)(PO4)(2)(OH)(6)}] center dot 4H(2)O (phen=1,10-phenanthroline)

An organic-inorganic hybrid molybdenum phosphate, Na-2[{Mn(phen)(2)(H2O)} {Mn(phen)(2)}(3){(MnMo12O24)-O-v (HPO4)(6)(PO4)(2) (OH)(6)}] . 4H(2)O (phen=1,10-phenanthroline), involving molybdenum present in V oxidation state and covalently bonded transition metal coordination complexes, has been hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction. Deep brown-red crystals are formed in the triclinic system, space group P (1) over bar, a=16.581(l)Angstrom, b=18.354(1)Angstrom, c=24.485(2)Angstrom, alpha=80.589(l)degrees, beta=71.279(1)degrees, gamma=67.084(1)degrees, V=6493.8(8)Angstrom(3), Z=2, lambda(MoKalpha)=0.71073Angstrom (R(F)=0.0686 for 29,053 reflections). Data were collected on a Bruker Smart Apex CCD diffractometer at 293 K in the range of 1.76 < theta < 28.06degrees using omega-2theta scans technique. The structure of the title compound may be considered to be based on {Mo6O12(HPO4)(3)(PO4)(OH)(3)} units bonded together with {Mn(phen)(2)} subunits into a two-dimensional network. Two types of tunnels are observed in the solid of the title compound.

朝鲜淫羊藿中生物碱类新成分的分离提取及结构鉴定

淫羊藿系小檗科淫羊藿属植物 ,具有补肾壮阳、强筋骨、祛风湿之功效 .现代药理研究表明 ,它还具有防治骨质疏松和提高免疫功能等作用 .2 0 0 0年版中国药典收载了 5种淫羊藿属植物 ,朝鲜淫羊藿为其中一种 ,是长白山道地中药材之一 .朝鲜淫羊藿中化学成分的研究多集中在黄酮类化合物方面 [1～ 6 ] ,而对其生物碱类化合物的研究较少 [7,8] .本文对朝鲜淫羊藿中生物碱类化合物进行了研究 ,并发现了一种新的生物碱 (6-羟基 -1 1 ,1 2 -二甲氧基 -2 ,2 -二甲基 -1 ,8-二氧 -1 ,3 ,4,8-四氢 -2 H -7-氧杂 -2 -氮 -苯并 [c]菲 ) ,采用核磁共振波谱技术鉴定了该化合物的结构 ,并用电喷雾多级串联质谱对其结构的正确性进行了验证 .1　实验部分1 .1　仪器　APEX FT-ICRMS高分辨质谱仪 (德国 Bruker Daltonnics公司 ) ;FTS-7型红外光谱仪(美国 BIO-RAD公司 ) ;AV40 0核磁共振波谱仪 (德国 Bruker公司 ) ,以 CDCl3作溶剂及内标 ;X-4数字显示显微熔点仪 (北京泰克仪器有限公司 ) ;MSn在 ...

Fabrication of nanometer-sized electrodes and tips for scanning electrochemical microscopy

A novel method for fabrication of nanometer-sized electrodes and tips suitable for scanning electrochemical microscopy (SECM) is reported. A fine etched Pt wire is coated with polyimide, which was produced by polymerization on the Pt surface initiated by heat. This method can prepare electrodes with effective radii varying from a few to hundreds of nanometers. Scanning electron microscopy, cyclic voltammetry, and SECM were used to characterize these electrodes. Well-defined steady-state voltammograms could be obtained in aqueous or in 1,2-dichloroethane solutions. Ibis method produced the nanoelectrodes with exposed Pit on the apex, and they can also be employed as the nanotips for SECM investigations. Different sizes of Pt nanotips made by this method were employed to evaluate the kinetics of the redox reaction of Ru(NH3)6(3+) on the surface of a large Pt electrode by SECM, and the standard rate constant kappa (o) of this system was calculated from the best fit of the SECM approach curve. This result is similar to the values obtained by analysis of the obtained voltammetric data.