AlGaN中的应变状态

用X射线衍射和卢瑟福背散射方法研究了生长在GaN上厚度为570nm的AlxGa1-xN外延层中的应变状态.实验结果显示AlGaN的共格因子在组分小于0.42时随组分的增加而近似线性减小,并且在0.42时达到30%,此后随组分的增加变化较慢,在x=1(AlN)时接近0.在本实验条件中,由于GaN层处于压应变状态,导致与AlGaN外延层的失配变小,使得组分约为0.16的AlxGa1-xN外延层可以共格生长在GaN层上.     

全固态窄线宽钠导星激光器

研制了一台重复频率400 Hz,平均功率1.0 W的激光二极管抽运全固态窄线宽钠导星激光器.利用两路波长分别为1064 nm和1319 nm的声光(AO)调Q激光器作为基频光,在腔外通过三硼酸锂(LBO)晶体和频产生(SFG)589 nm钠导旱激光,和频效率约达20%.每路基频光均采用标准具压窄线宽,输出和频光线宽约1.8 GHz,并调节控制标准具的温度和倾斜角度将中心波长锁定于589.159 nm(偏差±1 pm),实现了激光器谱线与钠原子D2线的精确匹配.     

Ni元素对激光诱导自蔓延反应合成Ti-Fe共晶合金组织性能的影响

采用激光诱导自蔓延反应合成制备了Ti-Fe-Ni三元合金。实验结果表明,当第三组元Ni含量介于12 at.%之内时,合成产物仍保持Ti70.5Fe29.5共晶合金的相组成,即是由β-Ti固溶体、TiFe和Ti2Fe金属间化合物所组成。但随着Ni含量的增加,合成产物中β-Ti固溶体的数量逐渐减少,而TiFe和Ti2Fe金属间化合物的数量逐渐增加。同时组织形态也由共晶组织逐渐转变为过共晶组织。随着Ni含量的增加,合成样品的致密度逐渐降低;由于受合成样品微观组织和致密性这两种因素的综合作用,致使Ni含量为9 at.%的合成样品具有高的硬度、强度及良好的塑性。     

Red polymer light-emitting devices based on dye-dispersed poly (9,9-dioctylfluorene-alt-benzothiadiazole)

A polymer-organic host-guest emitter (POHGE) system for obtaining polymer light-emitting diodes (PLEDs) with pure red emission and high luminance is proposed. The POHGE system was prepared by the fluorescent dye 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetra-methyljulolidy-9-enyl)-4H-pyran (DCJTB) doped in green-emitting polymer poly (9,9-dioctylfluorene-alt-benzothiadiazole) (BTF8). A photoluminescence (PL) quenching phenomenon was observed owing to the higher doping amount of DCJTB dopant. In this study, the red DCJTB dopant emits with high luminance and without concentration quenching when the host BTF8 emitting layer is doped with a small amount of the red guest DCJTB dopant. An optimal amount of DCCJTB dopant was obtained at 2 mg. Devices with a configuration of indium tin oxide (ITO)/poly (ethylenedioxythiophene) doped with poly (styrenesulfonate) (PEDOT:PSS)/BTF8:DCJTB/Ca/Al were fabricated. This device achieved an electroluminescence (EL) efficiency of 1.33 cd/A at 6 V. The emission area is 1.5 × 0.5 cm². The devices show the red light emission with a peak at about 630 nm. The color coordinate in Commission Internationale d’Eclairage (CIE) chromaticity is at x = 0.64 and y = 0.36.     

金属管材激光弯曲成形的扫描路径规划

基于几何曲率方法,针对AIS1304L不锈钢金属直管的激光平面弯曲成形和三维空间弯曲成形进行了路径规划的研究.对平面内弯曲成形,根据目标管形的极值点和拐点将管材分段,取极值点作为路径规划的初始位置,对各分段采用不同的扫描间距以确定加热扫描路径.对三维空间弯曲成形,采用投影分解的方法,把三维成形曲面投影分解为两个二维曲面,分别获取扫描路径和工艺参数,然后组合与简化,获取三维弯曲成形的扫描路径.实验采用Nd:YAG固体激光器,以平面内正弦曲面弯曲和空间螺旋管弯曲两种形式为例,作为目标形状进行扫描路径规划与实验验证,扫描弯曲结果证明了扫描路径规划方法的有效性.     

Study of Millimeter-Wave Radar for Helicopter Assisted-Landing System

Landing helicopters on rough unprepared terrain has always been considered hazardous, since the massive dust cloud generated by wind drafts from the helicopter's rotors completely obstructs the pilot's view of the landing area. This article presents a performance assessment of a proposed millimeter-wave (MMW) three-dimensional imaging radar system, specifically meant for helicopter assisted landing. The assessment includes simulation of radar backscattering from the underlying rough terrain, in addition to the signal attenuation and scattering from dust clouds generated by the helicopter's rotors. Terrain scattering is simulated in two steps: 1) generation of a two-scale random rough surface according to prescribed statistics of a large-scale undulation and a small-scale surface roughness; and 2) simulation of the returned signal, including the effects of the real-aperture radar parameters and the terrain-backscatter response. Details of the three-dimensional imaging algorithm are presented. Single-scattering theory is used to simulate the effects of a dust cloud - including signal attenuation and backscatter clutter generation - on the radar's performance. It is shown that operating in the upper millimeter-wave regime (70 GHz-220 GHz) is the most practical solution for a compact, high-resolution, three-dimensional imaging system for this problem.     

水煤浆在工业炉窑应用的市场分析

由于能源价格体系的不合理性,我国近年来水煤浆技术的发展和推广工作受到很大阻碍,甚至处于停滞状态。本文避开暂时的价格因素,从能源发展形势、应用市场前景及相关技术条件等方面对水煤浆的市场问题进行了分析。     

Laser diffraction from capillary waves on liquid film surfaces

A simple experiment for laser diffraction of capillary waves on liquid film surface (LFS) is realized. Steady and visible diffraction patterns are obtained. The dispersion relation of capillary waves on LFS is verified by laser diffraction. In particular, both the relation between the wave number and the film thickness at a fixed angular frequency and the relation between the angular frequency and the wave number at a fixed film thickness are investigated. The theoretical and experimental results are in good agreement.     

半导体激光器焊接的热分析

为了解决大功率半导体激光器的散热问题,利用有限元软件ANSYS,采用稳态热模拟方法,分析了半导体激光器内部的温度分布情况,对比分析了In、SnPb、AuSn几种不同焊料烧结激光器管芯对激光器热阻的影响。由模拟结果可见,焊料的厚度和热导率对激光器热阻影响很大,在保证浸润性和可靠性的前提下,应尽量减薄焊料厚度。另外,采用高导热率的热沉材料和减薄热沉厚度可有效降低激光器热阻。在这几种焊接方法中,采用In焊料Cu热沉焊接的激光器总热阻最小,是减小激光器热阻的最佳选择。通过光谱法测出了激光器热阻,验证了模拟结果,为优化激光器的封装设计提供了参考依据。     

A combined low power SAR capacitance-to-digital analog-to-digital converter for multisensory system

A combined successive approximation (SAR) capacitance-to-digital converter (CDC)/analog-to-digital converter (ADC) for biomedical multisensory system is presented in this paper. The two converters have same circuit blocks and can be exchanged by four switches. Capacitance or voltage from different sensing elements can be measured and converted to digital output directly. This single chip takes place of separated CDC and ADC so that the power consumption of the multisensory system is reduced. The asynchronous SAR circuit has low power and small area. A dynamic comparator with zero-static power is adopted. Switches are carefully designed to reduce the non-idealities of the converter. Several techniques, such as bootstrapped switches, bottom-plate sampling, dummy switches are used to improve the performance of the circuit. The CDC/ADC is fabricated in 0.18 μm CMOS process. Measurement results show that the ENOB of this 11 bits converter is 10.15 bits and its FOM is 45 fJ/conversion-step under 200 kHz sampling. The power consumption is 9.4 μW with 1.4 V power supply voltage and the core area is 0.1764 mm².