参数三次B样条曲线的一种整体光顺方法

本文在能量法的基础上，提出了一种新的目标函数，给出了参数三次Ｂ样条曲线的一种新的整体光顺方法。利用这种方法得到的曲线不仅具有较小的应变能，而且曲率变化比较均匀，具有很好的光顺效果。该方法能推广到对曲面的光顺。     

Crystallization behavior of star-shaped poly(ethylene oxide) with cubic silsesquioxane (CSSQ) core

The crystallization behavior of well-defined star-shaped cubic silsesquioxane-poly(ethylene oxide) (CSSQ-PEO) and linear PEO were studied in terms of differential scanning calorimetry (DSC) and wide-angle X-ray scattering (WAXS). It was found in DSC analysis that the glass transition temperature (T_g) and the crystallization temperature (T_c) of CSSQ-PEO are different from those of linear PEO. The presence of CSSQ in PEO reduced the overall crystallization growth rate. This effect can be ascribed to the reduction of the mobility of the PEO crystallites in the presence of CSSQ and the star structure of the polymer. The Ozawa method is qualitatively satisfactory for describing the nonisothermal crystallizations of linear PEO and CSSQ-PEO. The presence of CSSQ leads to the diffusion- and nucleation-controlled mechanisms in the crystallization process of CSSQ-PEO whilst only the nucleation-controlled mechanism was observed in the case of linear PEO. The apparent activation energy required for crystallization was calculated using the Kissinger method. The isothermal crystallization morphology of PEO and CSSQ-PEO were also examined by cross-polarizing optical microscopy (CPOM). The CPOM images indicated the spherulite growth is slower in CSSQ-PEO as compared to linear PEO. It was also investigated that more number of PEO spherulites in CSSQ-PEO were observed, which sizes are markedly smaller than the spherulites developed in linear PEO. Wide-angle X-ray scattering (WAXS) studies showed that the crystallization peaks for linear PEO and CSSQ-PEO appeared at different temperature revealing the crystallization process and crystal growth rate are different from each other. However, no significant distortion of the crystal structure of PEO was evaluated in the presence of CSSQ.     

立方相GaN的持续光电导

研究了金属有机物化学气相外延 (MOVPE)方法生长的非故意掺杂的立方相 Ga N的持续光电导效应 .在六方相 Ga N中普遍认为持续光电导效应与黄光发射有关 ,而实验则显示在立方 Ga N中 ,持续光电导效应与其中的六方相 Ga N夹杂有关系 ,而与黄光发射没有关系 .文中提出 ,立方相 Ga N与其中的六方相 Ga N夹杂之间的势垒引起的空间载流子分离是导致持续光电导现象的物理原因 .通过建立势垒限制复合模型 ,解释了立方相 Ga N的持续光电导现象的物理过程 ,并对光电导衰减过程的动力学作了分析 .对实验数据拟合的结果证明以上的模型和推导是与实验相符的 .     

大尺寸氟化铅晶体的生长

描述了不用高真空条件，在通常的Ｂｒｉｄｇｍａｎ－Ｓｔｏｃｋｂａｒｇｅｒ炉中，用高温下的反应方法，消除了原料及生长炉内残存的Ｏ＾２－及ＯＨ＾－，生长出优质，大尺寸的β－ＰｂＦ２晶体。在晶体生长时，出现的主要问题是在晶体中的针状结构及开裂，但可通过控制条件来解决。     

合成彩色立方氧化锆的宝石学特征

市场上出现的紫色、浅紫色、浅黄色、粉红色、酒黄色、黄褐色、红色人造立方氧化锆均为亚金刚光泽, 火彩明显; 密度为5.99～6.34 g/cm3, 相对硬度为8～9; 除粉红色者表现出非均质性和弱多色性且内含大量定向排列的白色脱溶物外, 其余的为均质性, 内部洁净; 不同颜色的立方氧化锆的吸收光谱、紫外荧光以及滤色镜下的变色情况均存在差异; 浅紫色立方氧化锆的吸收光谱特征表明它是Nd致色. 能谱分析结果表明: 彩色立方氧化锆的常见元素有Zr, Y, P, Hf, Ca等; Er, Ce, Fe分别是粉红色、红色、酒黄色立方氧化锆的致色元素; 当Y2O3的摩尔分数大于或近于7%时, 立方氧化锆为立方面心结构且内部洁净; 当Y2O3的摩尔分数小于5%时, 立方氧化锆表现为非均质性且内含大量定向分布的白色脱溶物. 用拉尔森改写的格拉斯顿-代尔公式计算其近似折射率为2.12～2.19.     

The thermal ignition of lignocellulosics in infinite slab and cubic geometries

Wood shaving samples were heated in both cubic baskets and in a previously described system realising the conditions of the ‘infinite slab’ in thermal ignition. Results from the two sets of experiment were found to be totally consistent with each other.     

Simulation of polycrystalline aluminum tensile test with crystal plasticity finite element method

The crystal plasticity was implemented in the finite element method（FEM） software ABAQUS through the user subroutine UMAT. By means of discretizing the space at the grain level with the Voronoi diagram method, a polycrystal model was built and used in the FEM analysis. The initial orientation of each grain was generated based on the orientation distribution function（ODF）. The developed model was successfully applied in simulation of polycrystalline aluminium samples deformed by the tensile tests. The theoretical strain--stress relation was in good agreement with the experimental result. The simulation results show that the grain size has significant effect on the deformation behavior. The initial plastic deformation usually occurs at grain boundaries, and multiple slip often results in an enhanced local hardening at grain boundaries.     

Small Noncoding RNAs in Knee Osteoarthritis: The Role of MicroRNAs and tRNA-Derived Fragments

Knee osteoarthritis (OA) is a degenerative knee joint disease that results from the breakdown of joint cartilage and underlying bone, affecting about 3.3% of the world’s population. As OA is a multifactorial disease, the underlying pathological process is closely associated with genetic changes in articular cartilage and bone. Many studies have focused on the role of small noncoding RNAs in OA and identified numbers of microRNAs that play important roles in regulating bone and cartilage homeostasis. The connection between other types of small noncoding RNAs, especially tRNA-derived fragments and knee osteoarthritis is still elusive. The observation that there is limited information about small RNAs different than miRNAs in knee OA was very surprising to us, especially given the fact that tRNA fragments are known to participate in a plethora of human diseases and a portion of them are even more abundant than miRNAs. Inspired by these findings, in this review we have summarized the possible involvement of microRNAs and tRNA-derived fragments in the pathology of knee osteoarthritis.     

Influence of the stress,strain, and temperature on the surface roughness of an AlSl 52100 steel due to an orthogonal cut

In recent years, the finite element method (FEM) has become the main tool for simulating the metal cutting process because research based on trial and error is time consuming and requires high investment. Early studies were done by different investigators. In this research AISI 52100, hardened steel (62 HRC) was selected for an orthogonal machining process as well as metal cutting simulation using the software DEFORM-2D. This software is based on a forging process and has been adapted to an orthogonal machining process. The results of simulated cutting forces were compared with experimental cutting force data to validate the orthogonal cut simulation. Also, the surface roughness was measured, and the influence of the stress, strain, and temperature on the surface roughness was studied.     

人胎盘泌乳素的提纯及裂解片断免疫学特性的研究

采用人胎盘泌乳素（hPL）-亲和层析和抗人血清抗体-亲和层析技术，从胎盘匀浆中提取hPL纯品，经圆盘电泳、免疫电泳及交叉试验证实为单一成分。溴化氰水解后的产物，以高效液相色谱分析。分离出7个肽链片断峰，分别用hPL和人生长激素（hGH）放免法检测其活性，其中第6肽链片断无hGH免疫活性，若用此片断制备特异抗体，可避免与hGH出现交叉反应。