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941.
对在c面蓝宝石上用氢化物气相外延法(HVPE)生长的六方相纤锌矿结构的GaN膜中的应力进行了分析。高分辨X射线衍射(002)面和(102)面摇摆曲线扫描(半高宽数值分别为317和358角秒)表明生长的GaN膜具有较好的晶体质量。利用高分辨X射线衍射技术准确测量了制备的GaN膜的晶格常数,并计算得到GaN膜中面内双轴应变和面外双轴应变分别为3.37×10-4和-8.52×10-4,等静压应变为-7.61×10-5。拉曼光谱和激光光致发光谱测试表明HVPE-GaN外延膜具有较好的光学特性,利用拉曼光谱的E2模式特征峰和激光光致发光谱中近带边发射峰的频移定量计算了外延膜中的面内双轴压应力和等静压应力。两种方法得到的面内双轴压应力较为相符。 相似文献
942.
943.
研究了Mn42Al50-xFe8+x合金的结构、磁性和磁热效应. 通过成分调节, 居里温度TC在室温附近一宽温区连续可调, 分别为270 K (Mn42Al42Fe16), 341 K (Mn42Al40Fe18)和370 K(Mn42Al38Fe20). 磁化强度在相变温度处发生一陡降, 热磁曲线和等温磁化曲线均未观察到热和磁的滞后, 表明发生一可逆的二级相变. 在各自居里温度附近, 0-5 T的外磁场变化下磁熵变峰值分别为2.48, 2.52和2.40 J·kg-1·K-1. Mn50-xAl50-yFex+y合金的磁熵变峰值虽然与许多优良的磁制冷材料相比并不大, 但是制备该化合物的原材料价格非常低廉, 制备工艺简单, 加工成型也较容易, 化合物本身耐腐蚀性、延展性较好, 且在居里温度附近发生的是可逆的二级相变, 无晶格或结构的变化, 有利于制冷剂的多次循环使用.
关键词:
磁性
磁热效应
二级相变 相似文献
944.
We present a simple method to obtain the optical and dielectric properties of samples without reference measurement in the reflection-type terahertz time-domain spectroscopy. The dielectric properties of the samples of silicon and gallium arsenide were examined. The optical and dielectric properties of the samples were measured through only simple configuration, without the misplacement error. The obtained dielectric functions of the samples in reflection geometry are in good agreement with that predicated by the theory. The main advantage of this method over other methods is its simplicity and accuracy and ease for application of the reflection systems with different incident angle. 相似文献
945.
This paper has presented transparent conductor oxide materials (TCOMs) based microstrip patch antennas with glass substrate and copper ground plane, which have been deeply analyzed in the visible spectrum region in comparison with the practical patch antenna model of indium tin oxide patch with glass substrate and different TCOMs based ground plane. As well as the study have investigated the effect of transparent oxide materials on patch antenna design instead of perfect conductor materials such as copper that has low cost and weight. The tradeoff between optical transparency and electrical conductivity will be evaluated for a range of visible regions. Microstrip transmission line feed method is used to predict the skin effects on a patch antenna and their impact on antenna efficiency, resonance frequency and optical transmission are also described. This study have discussed assessment of these tradeoffs and effect of TCOMs parameters on antenna design. 相似文献
946.
A high-powered tunable terahertz wave (THz-wave) has been parametrically generated via a surface-emitted THz-wave parametric oscillator (TPO) pumped by a multi-longitudinal-mode Q-switched Nd:YAG laser. The effective parametric gain length was enlarged by employing two MgO:LiNbO3 crystals. The tunable THz-wave radiation from 0.8 to 2.8 THz was realized via varying phase-matching angle between the pump wave and the Stokes wave. The maximum THz-wave radiation was 173.9 nJ/pulse at 1.7 THz as the pump energy was 82 mJ, corresponding to an energy conversion efficiency of about 2.12 × 10−6 and a photon conversion efficiency of about 0.035%. The first-order, the second-order and the third-order Stokes waves were observed during the experiments. 相似文献
947.
The availability of state of art GPGPU cards can play a promising role in accelerating the calculations of computer generated holograms (CGH) where one of the main problems of generating such holograms is the need for massive amount of calculations. Both CUDA and Matlab can be used alone to fulfill this purpose but using both at the same time gives a number of benefits. This paper is dedicated to present a performance study of applying Fermi-Architecture CUDA-enabled GPGPU card for speeding up the calculations of binary detour phase holograms using both Matlab and CUDA programming. 相似文献
948.
We study the two-flavor quark-meson (QM) model with the functional renormalization group (FRG) to describe the effects of collective mesonic fluctuations on the phase diagram of QCD at finite baryon and isospin chemical potentials, μB and μI. With only isospin chemical potential there is a precise equivalence between the competing dynamics of chiral versus pion condensation and that of collective mesonic and baryonic fluctuations in the quark-meson-diquark model for two-color QCD at finite baryon chemical potential. Here, finite μB=3μ introduces an additional dimension to the phase diagram as compared to two-color QCD, however. At zero temperature, the (μI,μ) plane of this phase diagram is strongly constrained by the “Silver Blaze problem.” In particular, the onset of pion condensation must occur at μI=mπ/2, independent of μ as long as μ+μI stays below the constituent quark mass of the QM model or the liquid-gas transition line of nuclear matter in QCD. In order to maintain this relation beyond mean field it is crucial to compute the pion mass from its timelike correlator with the FRG in a consistent way. 相似文献
949.
We study a depinning transition based on transient dynamics of vortices driven by a suddenly applied dc current, focusing on whether a difference in the equilibrium vortex phase that can lead to a different vortex flow will change the critical behavior. After preparing an ordered initial vortex configuration, we measure the time evolution of voltage associated with dynamic disordering in three magnetic fields, corresponding to the ordered phase (OP), disordered phase (DP), and coexistence phase. The critical behavior of the depinning transition is commonly observed in these phases, pointing to the universality of the transition. However, the critical behavior is most marked in the coexistence phase, while the suppression of the critical region and that of dynamic disordering are observed in OP and DP, respectively, whose origin is attributed to the different flow states among these phases. 相似文献
950.
纳米光子学已经对人们的日常生活产生了重要影响,并且纳米光子学器件产品有强大的市场需求,因此其研究结果可以很快转化为商品。文章介绍了在未来5到10年内对光子工业有重大影响并且有望进入商品市场的11个纳米光子学领域,其中包括:纳米尺度量子光子学、全光路由、用于增强磁存储的表面等离子体光子学、用于诊断治疗和药物输送纳米光子学、纳米成像、分子尺度上的化学与生物传感器、纳米标签、纳米尺度上操控光场的分布(光伏器件和LED/OLED)、原型试制的新技术、量身定制光学特性的纳米光子材料以及太赫兹技术等,希望文章能对中国的纳米光子学研究及其工业化应用有一定帮助。 相似文献