高阻尼比低质量比圆柱涡激振动试验研究

针对圆柱的涡激振动问题,设计开发了高性能循环水槽与超声位移传感器,研究了高阻尼比、低质量比条件下,弹性支撑的刚性圆柱的涡激振动变化规律。结果表明:(1)高阻尼比条件下,振幅主要受独立参数阻尼比、质量比的影响;低质量比条件下,振动频率随流速增大而增大,"锁定区间"较高质量比范围扩大。(2)高阻尼比、低质量比条件下,阻尼的增大会导致振幅减小且"锁定区间"变窄;但振动频率在"锁定区间"内变化趋势一致。(3)高阻尼比、低质量比有利于涡激振动的能量转化,但阻尼不可过大,否则振幅与"锁定区间"均变小,影响电能转化。     

钢筋再生混凝土梁徐变性能试验研究

为揭示钢筋再生混凝土梁的徐变性能,通过三种持荷水平下9根钢筋再生混凝土梁试件的徐变(徐变应变与徐变挠度)对比试验,分析了钢筋再生混凝土梁徐变与时间的相关关系,研究了加荷幅值、初始变形(初始应变、初始挠度)等因素对钢筋再生混凝土梁徐变性能的影响规律,揭示了钢筋再生混凝土梁的徐变机理。研究结果表明:在45%极限荷载水平的持续作用下,钢筋再生混凝土梁总徐变挠度值为初始挠度值的62%左右,并且在前期发展较快,7d发展至总徐变挠度值的64%左右,后期变缓;钢筋再生混凝土梁徐变随着施加荷载幅值、初始变形的升高而有所增加。经历徐变过程后的钢筋再生混凝土梁,其承载性能有所下降,变化趋势为总徐变值越大,降低的幅度也越大。     

方管铝合金梁受子弹撞击时动力响应的实验研究

报导了简支、固支方形管状截面铝合金梁在子弹撞击时动力响应的实验研究。实验中,采用电-光位移传感器记录了梁中点的位移-时间、速度-时间和加速度-时间历史曲线。实验结果表明,在子弹动能相同、质量不同时,其变形不同。梁中点最大位移和中点最终位移间有较大的差值,可见采用理想刚塑性模型很难描述这一现象,在分析中,必须考虑弹性效应。同时发现,由于方管局部变形而引起的变形软化效应将减少梁的动力承载能力。     

EXPERIMENTAL INVESTIGATION AND COMPUTER SIMULATION ON DYNAMIC BUCKLING BEHAVIOR OF LIQUID-FILLED CYLINDRICAL SHELLS UNDER AXIAL IMPACT

This article reports an experimental investigation on the axial impact buckling of thin metallic cylindrical shells fully filled with water. Low velocity impact tests are carried out by DHR-9401 drop hammer rig. The whole process of dynamic buckling is simulated using LS-DYNA computer code. The consistency between experimental observation and numerical simulation is quite satisfactory. The investigation indicates that quite high internal hydrodynamic pressure occurs inside the shell during the impact process. Under the combined action of the high internal pressure and axial compression plastic buckling occurs easily in the thin-walled shells and buckling modes take on regular and axisymmetric wrinkles. This project is supported by the National Natural Science Foundation of China(19672039) and the Shanxi Foundation for Returned Scholars from Abroad.     

光学薄膜激光损伤的光热偏转法实时研究

本文首次把调制与脉冲光热偏转技术同时置于激光损伤测试装置之中,用以进行光学薄膜激光损伤的实时研究.初步实验结果表明,该方法不仅有助于确定损伤阀值,也有助于分析损伤形貌和损伤过程,包括样品损伤前的行为及样品在重复频率激光作用下损伤的累积效应.     

Improved growth of PbI2 single crystals

The phase equilibrium and the crystallization process of lead iodide (PbI₂) melt have been primarily investigated according to the lead–iodine phase diagram. It is found that the iodine evaporation and the segregated lead deposition are the two important factors that affect the PbI₂ crystal quality. The new method of Pulling U-type quartz growth ampoule has been made to impede the decomposition of PbI₂ and the vaporization and condensation of iodine. An orange and translucent PbI₂ single crystal of large size was obtained by the improved growth method, i.e. U-type ampoule pulling. Resistivity of the as-grown crystal is up to 4×10¹¹ Ω cm, and IR transmission is up to 45% in the region from 7800 to 450 cm⁻¹. Therefore, the improved growth method is a promising convenient new method for the growth of high quality PbI₂ crystals.     

Analytical tools for the analysis of fire debris. A review: 2008–2015

The analysis of fire debris evidence might offer crucial information to a forensic investigation, when for instance, there is suspicion of the intentional use of ignitable liquids to initiate a fire. Although the evidence analysis in the laboratory is mainly conducted by a handful of well-established methodologies, during the last eight years several authors proposed noteworthy improvements on these methodologies, suggesting new interesting approaches. This review critically outlines the most up-to-date and suitable tools for the analysis and interpretation of fire debris evidence. The survey about analytical tools covers works published in the 2008–2015 period. It includes sources of consensus-classified reference samples, current standard procedures, new proposals for sample extraction and analysis, and the most novel statistical tools. In addition, this review provides relevant knowledge on the distortion effects of the ignitable liquid chemical fingerprints, which have to be considered during interpretation of results.     

RING-OPENING POLYMERIZATION OF 1,4-DIOXAN-2-ONE INITIATED BY LANTHANUM TRIS( 2,6-DI- TERT-B UTYL-4-METHYLPHENOLATE)

The ring-opening polymerization of 1,4-dioxan-2-one (PDO) was carried out by lanthanum tris(2,6-di-tert-butyl-4-methylphenolate) (La(OAr)3) as novel single component initiator. The influences of polymerization reaction temperature and the molar ratio of monomer to initiator on the monomer conversion and molecular weight of poly(1,4-dioxan-2-one) (PPDO) were explored. PPDO with high viscosity average molecular weight of 1.95 × 105 can be prepared at 40℃ when [PDO]/ [La(OAr)3] molar ratio was 800. Mechanism investigation shows that the polymerization proceeds through a "coordinationinsertion" mechanism with selective rupture of acyl-oxygen bond of PDO.     

Investigation of Phase Transition inLa1–xPrxGaO3 and La1–xNdxGaO3 Crystals

The solid solution crystals, La_1–xNd_xGaO₃ and La_1–xPr_xGaO₃ have been studied by differential scanning calorimetry method; the crystals exhibit the first order phase transition, the temperature of the transition linearly increases with the concentration of Pr or Nd. The structure of the crystals has been determined by X-ray diffraction. The correlation between the phase transition temperature and crystalline structure at the temperature of the phase transition in both solid solution families is discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

中国北方某河流水质现状调查及分析

为调查A河、B河下游水体的水质现状,于2014年丰水期（8月）和枯水期（12月）,选取A、B河下游各8个采样点,对水体的溶解氧、氨氮等6项理化指标,以及Hg、Pb等7项重金属指标进行检测,采用单项参数评价法和综合水质标识指数法对2条河流的水质现状进行分析及评价,并采用对数型幂函数普适指数公式对水体的富营养程度进行评价。结果发现,A、B河下游水质以劣V类为主,水体中各类重金属不超标,主要超标污染物为总氮、总磷、氨氮等。A河水质好于B河,2条河流丰水期水质好于枯水期。A、B河下游水体处于重富和极富营养化状态,应加强整治2条河流流域的农业面污染源,降低河流的富营养化风险。