纳米铝颗粒强氧化反应的发光特性

纳米颗粒与常规尺度颗粒相比，因具有小尺寸效应、表面效应以及很高的化学反应活性等特点，所以较之常规尺度粒子，能够在光、热、化学活性等方面展现出更多特有的性质。为了研究纳米铝颗粒在氧气环境下的氧化反应发光特性，设计了电容器放电将脉冲大电流通过铝丝，利用铝丝的电阻热储能使其在几微秒或更短的时间内熔化、气化，形成金属蒸汽或进一步形成等离子体，产生的纳米金属颗粒与周围的氧气自发进行氧化反应发光的电爆炸实验方案。实验测量到的铝氧发光光谱如图1所示。     

Synthesis and Structure of a Novel Cluster with Trigonal-bipyramidal Ge_2Ru_3 Core

ＩｎｔｒｏｄｕｃｔｉｏｎＷｅｒｅｃｅｎｔｌｙｒｅｐｏｒｔｅｄａｎｉｎｔｒａｍｏｌｅｃｕｌａｒｔｈｅｒｍａｌｒｅａｒ ｒａｎｇｅｍｅｎｔｂｅｔｗｅｅｎＳｉ—ＳｉａｎｄＦｅ—Ｆｅｂｏｎｄｓｉｎｔｈｅｄｉｎｕ ｃｌｅａｒｉｒｏｎｃｏｍｐｌｅｘ { (Ｍｅ2 ＳｉＳｉＭｅ2 ) [(η5 Ｃ5Ｈ4 )Ｆｅ(ＣＯ) ]2 (μ ＣＯ) 2 } (Ｓｃｈｅｍｅ 1) .1 5Ｔｈｅｔｈｅｒｍａｌｒｅａｒｒａｎｇｅｍｅｎｔｗａｓｌａｔｅｒｅｘｔｅｎｄｅｄｔｏｇｅｒｍａｎｉｕｍ ｉｒｏｎａｎｄｓｉｌｉｃｏｎ ｒｕｔｈｅｎｉ ｕｍａｎａｌｏｇｕｅｓ .6 8Ｔｈ…     

基于双剪应力屈服准则的受内压管道爆破压力分析

采用双剪应力屈服准则,对在内压作用下的无缺陷管道进行了塑性极限分析,得到了管道爆破压力的计算公式;并且将结果与基于Tresca、Mises、平均剪应力屈服准则得到的爆破压力进行了比较.研究结果表明:爆破压力随着管道材料的应变硬化指数的增大而减小,随着管道厚径比的增大而增大;此外,基于双剪应力屈服准则得到的管道爆破压力为爆破压力的上限,而基于Tresca屈服准则得到的爆破压力为管道爆破压力的下限.     

烟酰胺碳核苷类似物的模块化合成

以核糖异头羧酸制备为起始,以可见光/金属镍双重催化脱羧偶联反应为核心,与氰基水解反应相结合,开发了一条新的模块化合成路线,实现了一系列苄基保护烟酰胺碳核苷类似物的高效合成,其结构经¹H NMR, ¹³C NMR和HR-MS( ESI)表征。      

靶与光斑尺寸对激光冲量影响的数值模拟

采用二维雷诺平均N-S方程,数值模拟研究了大气条件下短脉冲激光与固体靶相互作用所产生等离子体的动力学过程。采用k-ε两方程模型用于湍流的数值模拟,分别利用ROE格式和二阶中心格式对对流通量和粘性通量进行离散处理;用高斯-赛德尔隐式格式对方程进行时间推进求解。数值模拟给出了激光引发靶蒸气等离子体侧向膨胀、稀疏等二维流体动力学过程的物理图像,讨论了靶与光斑尺寸对脉冲激光冲量的影响。结果表明,不同宽度固体靶受到的激光冲量有很大差异,固体靶宽度越大,受到的激光冲量也越大。     

Characteristics of surface waves in anisotropic left-handed materials

We report the coexistence of TE and TM surface modes in certain same frequency domain at the interface between one isotropic regular medium and another biaxially anistotropic left-handed medium. The conditions for the existence of TE and TM polarized surface waves in biaxially anisotropic left-handed materials are identified, respectively. The Poynting vector and the energy density associated with surface modes are calculated. Depending on the system parameters, either TE or TM surface modes can have the time averaged Poynting vector directed to or opposite to the mode phase velocity. It is seen that the characteristics of surface waves in biaxially anisotropic left-handed media are significantly different from that in isotropic left-handed media.     

切向气流和激光作用下碳纤维/环氧材料的损伤特性

无气流和切向气流马赫数分别为0.50,0.85条件下,开展了碳纤维/环氧材料激光辐照损伤特性研究实验,对碳纤维、环氧树脂和复合材料热失重曲线、温度历史曲线以及实验后复合材料损伤形进行分析,结果表明:由于切向气流阻止材料燃烧且对材料表面起冷却作用,无气流条件下材料的热损伤区域远大于激光辐照区域,与切向气流条件相比,材料后表面温升时间长、温升幅值高;在切向气流环境下,由于气流作用使得材料的损伤包括烧蚀损伤和断裂损伤;从损伤形貌和后表面温度历史、温升速率比较来看,在切向气流马赫数为0.50~0.85的速度范围内,碳纤维/环氧材料在切向气流和连续激光(102 W/cm2量级)联合作用下的损伤差异不明显。     

连续激光重复加载下30CrMnSiA钢的反射率

利用双光束反射率测量装置,研究了连续激光重复加载作用下30CrMnSiA钢金属材料的反射率变化特性。通过激光加载、冷却然后再加载到更高的温度的辐照试验与激光单次辐照的结果比较,发现二次加载时材料表面的激光反射率与样品表面首次加载时达到的最高温度所对应的反射率基本一致,只有达到并超过首次加载时样品曾达到的最高温度后,样品表面的反射率才会再次发生变化,且变化趋势与单次完整加载时的路径重合。这表明样品表面的反射率与其达到的最高温度有关,进一步的研究结果表明,样品达到的最高温度与样品表面在最高温度下产生的氧化反应层有关,而这一氧化层在冷却过程和再加载过程不变化。     

Study on optical characteristics of Nd:YVO_4/YVO_4 composite crystal laser

Thermal effect in crystals is the main obstacle blocking diode-pumped solid state laser to get high and stable output, power. Diffusion bonding crystal has been demonstrated to be an effective method to relieve the thermal lensing theoretically based on the numerical heat analysis to the end-pumped anisotropic laser crystal. The temperature distributions in Nd:YV04/YVO4 composite crystal and conventional crystal were analyzed and compared. The end-pumped Nd:YVO4/YVO4 composite crystal laser was designed and set up with 2-cavity. The maximum output powers of 9.87 W at 1064 nm and 6.14 W at 532 nm were obtained at the incident purnp power of 16.5 W. The highest optical-optical conversion efficiencies were up to 59.8% at 1064 nm and 37.2% at 532 nm respectively.     

Influence of ambient pressure on properties and expansion of laser-induced plasma

A Nd:YAG pulsed laser is used to ablate HgCdTe target at different ambient pressures, the emission spectrum is detected by a time- and space-resolved diagnostic technique. It is found that the characteristics of time-resolved emission spectra are influenced by the pressure of background gas. A theoretical model is developed to investigate expansion mechanism of plasma, the time evolution of the propagation distances and the velocities of plasma plume are calculated by the model at pressures of 1.01×105, 1000, and 5 Pa, respectively. The calculated results are well consistent with the experimental data.