爆轰加载下柱壳断裂时刻微小差异测量方法

对于断裂时刻差异较小的对比实验,提出一种判读方法:同时采用高速摄影和干涉测速,利用高速摄影判读壳体断裂时刻应变,利用干涉测速获取壳体位移及应变曲线,两者结合得出较为精确的壳体断裂时刻差异。利用该方法得出45钢柱壳在JO-9159和JOB-9003两种炸药加载下断裂时间相差0.45 μs,钨合金柱壳在两种炸药加载下的断裂时间相差0.39 μs。同时该方法可以推广应用于单发壳体膨胀断裂实验中,更精确测定壳体的断裂时刻。     

高速列车致声屏障风压变化和分布特性研究

高速列车致声屏障在极短的时间内受到交变气动力作用,一旦声屏障因强度或疲劳破坏而失效,有可能危及行车安全,因此准确评估高速列车致声屏障的脉动风压分布是结构设计需考虑的关键要素．利用数值风洞技术,模拟了道路及桥梁两侧分别布置5m、3.5m高声屏障,350km/h的列车通过时致声屏障的极值风压分布特性．研究结果表明列车驶过声屏障会产生气流挤压的正压波及气流填充的负压波,正压数值较负压数值大;极值风压随声屏障高度的增加而减小,且列车中心与声屏障的距离、声屏障的高度都会明显减弱极值风压的数值;两列车的交会相比单列车的通过,会更明显地挤压声屏障区域内的气流,从而在声屏障上产生更大的极值风压,且随着列车与声屏障距离的靠近,挤压增大极值风压的特性表现更为明显．最终通过选取京沪高铁试验段,进行相关的现场高速列车致声屏障极值风压试验测试,试验结果验证了数值模拟结果的准确性．     

半制备型高速逆流色谱分离制备铁棒锤根中的一种咪唑生物碱

采用高速逆流色谱（HSCCC）技术从铁棒锤根氯仿提取物中分离制备了一种高纯度咪唑类生物碱1H-imidazole-2-carboxylic acid,butyl ester （ICABE）。采用高效液相色谱（HPLC）测定目标化合物在两相溶剂中的分配系数,优化HSCCC分离ICABE的溶剂体系,确定了以正己烷-氯仿-乙醇-水（10：1：13：2,v/v/v/v）为HSCCC的两相溶剂系统,以上相为固定相,下相为流动相,流动相流速为1.8 mL/min,主机转速850 r/min,检测波长为230 nm条件下进行分离制备,在350 min内从100 mg粗样品中一步分离得到7.5 mg ICABE,经HPLC检测其纯度达98%以上（峰面积归一化法）,结构由UV、¹H-NMR和¹³C-NMR得以鉴定。该方法简便、快速,所得产物纯度高,适合于铁棒锤中ICABE的制备分离。     

高速光探测器封装的优化设计

提出了一种高速光探测器封装优化设计的新方法。首先用矢量网络分析仪对封装寄生参量和探测器芯片进行准确测量,研究了探测芯片的本征参量与封装寄生参量之间的谐振现象,然后合理利用这种谐振效应对芯片的频率响应特性进行有效补偿。理论分析和实验结果都证明优化封装后器件的频率响应带宽超过了芯片的响应带宽。该方法不需要另加其它元件．而仅仅利用光电器件封装过程中必不可少的金丝所带来的寄生电感,就达到了改善器件频率响应特性的目的。     

单晶硅高速磨削亚表层损伤机制的分子动力学仿真研究

运用分子动力学仿真模拟高速磨削下单颗金刚石磨粒切削单晶硅的过程,通过分析切屑、相变、位错运动并结合工件表面积的演变规律研究磨削速度对亚表层损伤和磨削表面完整性的影响.仿真结果显示:磨削速度的增大会加剧磨粒前端材料的堆积,超过200 m/s后增加不再明显.而加工区域的平均温度通过原子之间的挤压和摩擦会不断增大.在磨削温度、磨削力以及粘附效应的相互作用下,摩擦系数先增大后减小.晶格的变形、晶格重构和非晶相变导致切屑形成过程中的磨削力剧烈波动.研究结果表明:在加工脆性材料单晶硅过程中,随着磨削速度的升高亚表层损伤厚度先减小后增大.当磨削速度低于150 m/s时,随着磨削速度的升高,磨粒下方的原子晶格重新排列的时间缩短,非晶结构的产生减少,亚表层损伤厚度减小.当磨削速度超过150 m/s时,加工区域中的高温成为主导因素促进位错的成核、运动致使亚表层损伤厚度增大.     

正交设计试验优化高速逆流色谱分离制备玛咖中芥子油苷的条件

基于高速逆流色谱（HSCCC）技术从玛咖中分离制备出两种芥子油苷,苄基芥子油苷（glucotropaeolin, GTL）和甲氧基苄基芥子油苷（glucolimnanthin, GLI）。使用正交设计试验对分离条件进行优化,采用高分辨质谱对制备的组分进行鉴定,采用高效液相色谱法（HPLC）对组分进行定量分析。确定了两个组分GTL与GLI的HSCCC最佳分离条件：溶剂系统为正丁醇-乙腈-200 g/L硫酸铵溶液（1:0.5:2.4, v/v/v）,上相为固定相,下相为流动相,流动相流速2 mL/min,主机转速900 r/min,从玛咖根粗提物中一次性分离得到157.72 mg/kg纯度为97.9%的苄基芥子油苷和31.93 mg/kg的甲氧基苄基芥子油苷,固定相保留率达57.6%。该方法成本低,简便易行,样品损失量小,可大量循环进样制备。     

细长体倾斜出水的实验研究

为了获得细长体倾斜出水空泡生成、发展及溃灭过程,基于高速摄像系统对细长体小倾角倾斜出水过程进行了实验研究。通过对比细长体垂直及倾斜带泡出水过程,分析了倾斜出水过程中体现出的新特征及其影响因素。在此基础上,对不同初始倾角及细长体头型对出水轨迹及姿态的影响规律进行了实验研究:细长体姿态及轨迹变化与其初始倾角并非线性相关,与肩空泡的闭合位置密切相关;细长体头型变钝,其水下运动过程稳定性增加。     

动车组车轮轮缘塑性变形白层组织分析

本文作者对动车组ER8C车轮轮缘白层的微观组织进行了观察,重点对由于剧烈塑性变形而形成的白层进行了分析和探讨.在光镜下可以观察到白层厚为3~18μm,分布不连续.在扫描电镜下,塑性变形白层主要有两种类型:一种为经塑性变形作用而细化的组织和经动态再结晶作用得到的铁素体纳米晶,后者具有纳米量级的铁素体晶粒.白层内的碳化物数量与塑性变形程度及运行过程中的温升有关,越接近表层未溶碳化物越少、晶粒越小.白层形成机制主要分为两种:一种为反复塑性变形作用的机制,导致铁素体破碎细化同时伴随碳化物碎化溶解;另一种为变形与一定温升综合作用的机制,表层发生动态再结晶而形成超细晶粒组织并伴随碳化物溶解,后者在超细晶粒形成中起主导作用.     

Analysis of Multiple Melting of High-Speed Melt Spun Polylactide Fibers Based on Kinetic Modeling

Multiple melting behavior of high-speed melt-spun polylactide (PLA) fibers was investigated by temperature modulated differential scanning calorimetry (TMDSC) in the heating process with various modulation periods in the calorimeter. In the case of the as-spun PLA fibers taken-up at 1 km/min, a melting endothermic peak and a recrystallization exothermic peak appeared at the same peak temperature of 151°C in the reversing and non-reversing heat flows (RHF and NRHF), respectively, whereas at 168°C, an endothermic peak was observed in both the RHF and NRHF. On the other hand, the as-spun PLA fibers taken-up at a high-speed of 6 km/min showed the melting in both the RHF and NRHF, but the recrystallization behavior was not obvious in the NRHF at the shorter modulation period conditions. The obtained data were analyzed based on the kinetic modeling of melting proposed by Toda et al. The real and imaginary parts of the complex apparent heat capacity in the melting region showed a strong modulation period dependence for both the low- and high-speed spun fibers. The endothermic heat flow of melting was separated by extrapolating the frequency to zero. For the PLA fibers spun at 1 km/min, a set of melting and recrystallization peaks in the RHF and NRHF appeared even for the melting at 168°C. In other words, the simultaneous occurrence of melting and recrystallization was confirmed through this extrapolation. For the 6 km/min PLA fibers, the presence of an exothermic heat of recrystallization was clearly confirmed at a peak temperature of 164°C.     

Multiple Melting Behavior of High-Speed Melt Spun Polylactide Fibers

High-speed melt spinning of polylactide (PLA) was conducted and the structure and multiple melting behavior of the as-spun fibers were investigated. In the analysis of temperature modulated differential scanning calorimetry (TMDSC) thermograms for the as-spun PLA fibers taken-up at 1 and 6 km/min, the peaks around the melting temperature region in the reversing heat flow (RHF) and nonreversing heat flow (NRHF) curves were mainly separated into (1) a pair of an endothermic peak (Peak L) in RHF and an exothermic peak (Peak R) in NRHF in a low temperature region, (2) an endothermic peak (Peak M) both in RHF and NRHF (only in RHF for PLA fiber spun at the low-speed) in an intermediate temperature region, and (3) an endothermic peak (Peak H) both in RHF and NRHF in a higher temperature region. Wide-angle X-ray diffraction (WAXD) measurements were conducted during the heating process of the as-spun fibers cut into powders. In the case of fibers obtained at 1 km/min, disordered crystals, i.e. α′-form crystals, were formed through cold crystallization followed by a disorder-to-order phase transition, i.e. α′ to α crystalline modification, with partial melting of the α′ crystals around 148.5°C in the temperature range of Peaks R and L. Finally, the α form crystals melted above 169.4°C, in the temperature range of Peak H. On the other hand, the PLA crystals generated by the orientation-induced crystallization during the spinning process at a spinning velocity of 6 km/min did not show a WAXD profile of perfect α form crystals but showed an intermediate structure having lattice spacings between the α′ and α forms. Such intermediate crystals did not transformed into α form crystals during the heating process.