Fabrication and electrical properties of a carbon nanotube quantum dot

Single-walled carbon nanotubes (SWNTs) were synthesized by pyrolyzing methane (CH₄) at a temperature of 900℃ on SiO₂ substrates pre-coated with iron nano-particles. Electrical contacts were fabricated onto one of the SWNTs by using an electron beam lithography process. Coulomb blockade and single-electron tunnelling characters were found at low temperatures, indicating that the SWNT in-between the electrodes forms a quantum dot. It is found that the Coulomb gap of the quantum dot is about 8.57 meV, and the factor \alpha , which converts the gate voltage to the true electrostatic potential shift, is around 200 for this device.     

Hopping Conductivity in a Single-Walled Carbon Nanotube Network

We investigate the resistance and magnetoresistance （MR） of an entangled single-walled carbon nanotube （SWNT） network. The temperature dependence of conductance is fitted by formula G（T） = Go exp[-（To/T）^1/2] with To = 15.8 K at a wide temperature range from 4 K to 300K. The MR defined by [R（T, H） - R（T, 0）]/ R（T, 0） as a function of temperature and magnetic field perpendicular to the tube axis is negative at low temperatures. The MR amplitude increases as the temperature decreases at relative high temperature, but becomes decrease when temperature below 4 K. The results are explained in terms of the coherent hopping of carriers in the presence of a Coulomb gap at low temperature.     

长飞片撞击薄靶板结构的定位技术及实验研究

出于防护机匣被发动机破碎叶片破坏的需求,利用一级轻气炮实验装置对长飞片高速撞击薄靶板结构进行冲击实验和测试方法的研究.实验中使用对靶定位控制技术保证长飞片对靶板撞击的位置准确定位,同时碰撞平面度误差小于10毫弧度,得到了不同撞击参数下薄板击穿性能的实验数据.实验结果表明:薄板的破坏失效模式为隆起-剪切破坏,裂纹出现及发展也主要由于剪切应力造成.本研究可为进一步的相关结构冲击实验及测试方法提供参考.     

“烧蚀模式”激光推进的实验研究

 采用单脉冲激光进行了大气环境下激光烧蚀小钢珠实验,得到其推进效应参数,发现并分析了钢珠在不同放置位置（焦前与焦后）时不同的物理现象;为了得到一系列定量实验数据,采用自行研制的激光冲量靶仪进行了单脉冲激光烧蚀推进效应实验测试,得到了不同环境条件、不同靶材料的激光推进效应参数,并与国外的实验数据以及数值计算结果进行了比较。实验表明,靶材料和激光功率密度是影响冲量耦合系数的主要因素,冲量耦合系数随环境气压的降低而升高。     

Experimental investigation of the effects of laser parameters on laser propulsion

The effects of main laser parameters, such as pulse energy, pulse duration, frequency, and work time on laser propulsion of "air-breathing mode", are investigated experimentally with a high power and high repetition frequency TEA-CO_2 pulsed laser. The results show that the momentum coupling coefficient C_m decreases with increasing the pulse energy for single pulse tests and pulse duration of about 1 μs. Either higher or lower frequency will reduce C_m in multi-pulse tests, which suggests an optimal frequency for the maximum C_m. As to the work time, the longer the work time is, the less the C_m will be.