Thermal stability of cluster structure in Bi x Sn1− x molten alloys in vicinity of eutectic point

Structure of liquid Bi _x Sn_{1? x} molten alloys has been studies in the vicinity of eutectic point at temperatures of complete melting and above by 100?K. It is shown that the structure parameter concentration dependences reveal the deviation from linear function with extremum points at eutectic composition. Such features exist also at higher temperatures. The reason of untypical behaviour of structure parameters is supposed to be attributed to the existence of two kinds of clusters with Sn‐ and Bi‐like structures.     

铜导线短路熔痕的XPS研究

利用氩离子溅射对熔痕样品进行了深度刻蚀,同时利用Cu的俄歇谱线和计算的俄歇参数值,对不同环境形成的铜导线短路痕迹的物相及元素分布规律进行了分析。根据刻蚀时间可将一次短路熔痕表面膜层分为三部分,即C含量迅速减少的近表面层;O含量变化不大,C含量逐渐消失且有Cu₂O相的中间层;无Cu₂O相,O含量显著减少的过渡层。而将二次短路熔痕表面膜层分为两部分：C含量迅速减少的近表面层;无Cu₂O相,C和O量逐渐减少层。由此可见,一次短路熔痕的表面膜层与基体分界明显,有显著的过渡层,而二次短路熔痕的表面膜层与基体分界不明显,无过渡层。综上所述,可以根据两种短路熔痕是否含有Cu₂O相以及定量分析结果来区分两种熔痕,为判断火灾原因提供新的技术依据。     

静电纺丝制备SiO2短纤维对聚丙烯冲击性能的影响

采用静电纺丝技术, 结合正硅酸乙酯(TEOS)的溶胶-凝胶反应制备出了直径为500 nm的SiO2短纤维(n-SF). 纤维经过硅烷偶联剂KH570表面处理后, 与聚丙烯(PP)通过螺杆混合制得复合材料. 通过SEM观察, KH570处理过的SiO2短纤维(n-MSF)在PP基体中分散均匀, 界面结合良好. DSC和XRD测试结果表明, n-SF和n-MSF的加入均可提高PP的结晶速率, 同时改变PP中β晶含量, 进而影响冲击强度; 冲击实验结果表明, n-MSF添加量为3%(质量分数)时, 复合材料冲击性能比纯PP提高了40.3%.     

超短强激光脉冲在大气传播中的自聚焦行为

通过建立涉及克尔效应和多光子电离效应的非线性数学模型,利用数值方法研究了超短激光脉冲在大气传播中的聚焦行为。结果表明由自聚焦导致的成丝现象具有间断,而不是一种稳态的模式。每次轴上的成丝都会由于光场损耗减弱,但同时由于克尔效应会使离轴区域的能量间断地补充到光轴上。     

Microemulsion polymerization of styrene stabilized by sodium dodecyl sulfate and short‐chain alcohols

Styrene microemulsion polymerizations with different short‐chain alcohols [n‐C_iH_2i+1OH (C_iOH), where i = 4, 5, or 6] as the cosurfactant were investigated. Sodium dodecyl sulfate and sodium persulfate (SPS) were used as the surfactant and initiator, respectively. The desorption of free radicals out of latex particles played an important role in the polymerization kinetics. An Arrhenius expression for the radical desorption rate coefficient was obtained from the polymerizations at temperatures of 50–70 °C. The polymerization kinetics were not very sensitive to the alkyl chain length of alcohols compared with the temperature effect. The maximal polymerization rate in decreasing order was C₆OH > C₄OH > C₅OH. This was related to the differences in the water solubility of C_iOH and the structure of the oil–water interface. The feasibility of using a water‐insoluble dye to study the particle nucleation mechanisms was also evaluated. The parameters chosen for the study of the particle nucleation mechanisms include the cosurfactant type (C_iOH), the SPS concentration, and the initiator type (oil‐soluble 2,2′‐azobisisobutyronitrile versus water‐soluble SPS). © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3199–3210, 2001     

茂金属聚乙烯的非等温结晶行为及其动力学研究

为探索分子量和支链含量对聚乙烯非等温结晶过程的影响,选用3组样品:(1)不同分子量的无支链线形聚乙烯;(2)低分子量的支链含量不同的试样;(3)高分子量的支链含量不同的试样.用DSC研究了这3组样品的非等温结晶动力学.结果表明:(1)与支链含量相比,分子量大小对结晶的影响是次要的,但高分子量样品的结晶度比低分子量样品低;(2)支链对聚乙烯的非等温结晶有重要影响,在支化聚乙烯中起决定作用;(3)无论是高分子量试样还是低分子量试样,支化含量增加,聚乙烯的结晶温度、结晶度、结晶动力学以及晶体的熔点等显著降低.     

9号染色体上海洛因依赖易感基因的定位

目的:筛查和定位9号染色体上海洛因依赖易感基因的位点.方法:在10例海洛因依赖者和其正常同胞对照者中用覆盖第9号染色体的20个短串联重复序列(Short Tandem Repeats,STR)进行荧光标记的基因组扫描.结果:D9S286, D9S167和D9S164位点等位基因在海洛因依赖组和其正常同胞对照组之间分布有显著性差异(x2检验,P＜0.05).其它17个STR位点D9S288,D9S285,D9S157, D9S171,D9S161,D9S1817, D9S273,D9S175,D9S283,D9S287,D9S1690,D9S1677,D9S1766, D9S1682, D9S290,D9S1826,D9S158的等位基因在海洛因依赖组和其正常同胞对照组之间分布没有显著性差异(x2检验,P＞0.05).结论:D9S286,D9S167和D9S164位点附近可能存在海洛因依赖的易感基因,多巴胺β-羟化酶基因可以作为候选基因.     

Short-range order in some polymer melts from X-ray diffraction

Wide-angle X-ray diffraction measurements were performed on polymer melts of isotactic and syndiotactic polypropylene (IPP and SPP), poly(ethylenepropylene) (PEP), polystyrene (PS), polyisobutylene (PIB), and polyethylene (PE), to study the dependence of the short-range structure of polymer liquids on chain architecture. Total structure functions, which comprise intra- and intermolecular contributions, were derived from the scattering data. The trivial Fourier components of the intramolecular structure (C(SINGLE BOND)>C ≃ 1.54 Å and C(SINGLE BOND)C(SINGLE BOND)C ≃ 2.55 Å) were subtracted from the total structure functions. The remaining functions contain only those intramolecular contributions dependent on the chain's conformational degrees of freedom, plus the intramolecular contributions. The structural differences between the polymers in momentum space are discerned only when the trivial components are subtracted. This subtraction also reduces the effects of truncation errors on Fourier transformation to real space. The short-range structure of PIB appears very different compared to all the others, which correlates with anomalies in a number of physical properties for this polymer. © 1996 John Wiley & Sons, Inc.     

渐开线斜齿轮短齿廓修形降噪分析*

为了降低特定工况下减速箱的噪声特性,找到相对最佳的渐开线斜齿轮修形方式,该文基于专业的齿轮修形软件Kisssoft和多学科一体化软件LMS Virtual Lab,根据短齿廓修形可以改变渐开线斜齿轮的端面、轴向重合度的原理,比较了未修形和经过不同短齿廓修形方式达到特定重合度后的渐开线斜齿轮减速箱声功率级的大小。分析了经过短齿廓修形后的减速箱声功率级在转速500~2000 r/min之间显著下降的原因,并对经过短齿廓修形后的减速箱声功率级在2500 r/min和3000 r/min时并未明显下降的原因做了解释。最后根据减速箱声功率级在转速500~2000 r/min之间的平均降幅,认为通过齿形鼓形修形使得渐开线斜齿轮的端面、轴向重合度分别为1.516、0.864时,减速箱声功率级降幅最大,降噪效果最好。