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基于第一性原理赝势平面波方法对伽马晶体CuCl, CuBr, CuI的体模量、体模量对压强的一阶偏导 数、电子结构、折射率等光学性质进行了计算.计算结果表明,广义梯度近似(GGA)下CuX(X = Cl, Br, I) 晶体的晶格常数与体模量的计算值与实验相差较小.与局域密度近似(LDA)相比, GGA更适合于 CuX(X = Cl, Br, I)晶体 的计算.这三者的价带都来源于Cu的3d态,导带部分主要来自Cu和卤素的s电子贡献,很少部分来自卤素的p电子 贡献.计算得到CuCl, CuBr, CuI的折射率分别为1.887, 2.015, 2.199,与应用Gladstone-Dale半经验关系得到 的结果符合得很好. 相似文献
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现代可编程约瑟夫森电压基准的核心器件是约瑟夫森结阵.目前最具有优势的约瑟夫森结阵是 Nb/NbxSi1-x/Nb材料的结阵. Nb/NbxSi1-x/Nb材料的约瑟夫森结 具有三层薄膜的制作过程简便, Nb和NbxSi1-x刻蚀工艺相同以及NbxSi1-x 势垒层成分可调等优点.中国计量科学研究院设计制作了Nb/NbxSi1-x/Nb约瑟夫森单结. 通过在4.2 K低温下对所做单结进行直流电流-电压特性测量,观测到了清晰的超导隧穿电流和 从零电压态向电压态的跳变,最后就测量结果进行了分析讨论.此项工作属于国内首个开展 Nb/NbxSi1-x/Nb材料约瑟夫森单结研究的工作. 相似文献
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基于对Poly-Si1-xGex栅功函数的分析,通过求解Poisson方程, 获得了Poly-Si1-xGex栅应变Si N型金属-氧化物-半导体场效应器件 (NMOSFET)垂直电势与电场分布模型.在此基础上,建立了考虑栅耗尽的Poly-Si1-xGex栅应变Si NMOSFET的阈值电压模型和栅耗尽宽度及其归一化模型,并利用该模型,对器件几何结构参数、 物理参数尤其是Ge组分对Poly-Si1-xGex栅耗尽层宽度的影响, 以及栅耗尽层宽度对器件阈值电压的影响进行了模拟分析.结果表明:多晶耗尽随Ge组分和栅掺杂浓度的增加而减弱, 随衬底掺杂浓度的增加而增强;此外,多晶耗尽程度的增强使得器件阈值电压增大. 所得结论能够为应变Si器件的设计提供理论依据. 相似文献
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用传统的熔融急冷法制备了组分为(100-2x) GeS2-xGa2S3-xCsCl (x= 15, 20, 25 mol%)系列硫卤玻璃, 测试了样品玻璃的吸收光谱. 采用Z-扫描方法测试了样品的三阶非线性光学特性. 分析了激光光子能量与玻璃三阶非线性光学特性的关系,并研究了组分变化对玻璃的三阶非线性性能的影响. 研究结果表明,光子能量的少许改变可以使非线性吸收系数在一个较大的范围内变化,随着光子能量的增大, 玻璃的非线性吸收系数β 增大;当光子能量趋近于0.5Eg时, β值趋近于0,玻璃有最佳的品质因子; 玻璃样品中CsCl含量的增加使得玻璃的光学带隙Eg增大,短波截止边蓝移,非线性吸收系数β 减小. 但是由于结构与带隙对光学非线性的影响相反,非线性折射率γ 值变化不大. 该结果表明样品的光学非线性性能由光学带隙和结构两方面因素共同决定,对今后研究全光开关用硫系玻璃具有一定的指导意义和参考价值. 相似文献
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研制了一种激光共焦扫描显微内窥镜,采用望远式显微内窥光学系统,同时实现长距离的图像中继传输、远心f-theta光学扫描和显微内窥成像功能.二维共焦扫描由双振镜实现,低噪音扫描控制信号由嵌入式系统产生.为实现便携式应用,激光共焦扫描显微内窥镜采用小型化设计方案.首先,体内的显微内窥成像光学系统,外径尺寸为8 mm,工作长度为250.3 mm,可通过标准腹腔镜手术孔进行体内显微内窥成像;其次,采用3 mm通光孔径的小尺寸平面反射镜实现体外共焦扫描,摆动频率为100 Hz,实现快速共焦扫描;最后,激光控制和荧光探测仅通过电缆和光纤与共焦扫描显微内窥镜前端连接,减小了显微内窥镜的前端尺寸和重量.通过实验验证,本系统的成像视场为φ 600 μm,光学分辨率为2.2 μm,可采用手持式或者其他方式工作,进行体内组织的共焦扫描成像,实现微创、在体的荧光显微内窥术. 相似文献
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We present a line-scan camera calibration method in a plane not perpendicular to but parallel to the optical axis, without requiring the camera motion or a complex calibration pattern. A random 2D reference coordinate system in the calibration plane can be used, images of a rod perpendicular to the calibration plane at known coordinates are captured by the camera, the relation between the given coordinates and the rod image centroid position are analyzed based on a reduced pinhole model and image processing, and then the camera parameters and distortion factors are all estimated. These distortion factors build a sample relation only between the image position in theory and in practice, and they do not change with object position. Two wide-angle line-scan cameras that are used in a 2D-coordinate measurement system are calibrated by this method; the application results illustrate the effectiveness and convenience of this method. 相似文献
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Takashi MORISHIGE Masanori TAMAKOSHI Tomoya TAKEMURA Fumihiko SATO 《Proceedings of the Japan Academy. Series B, Physical and biological sciences》2010,86(7):757-768
O-Methyltransferases, which catalyze the production of small molecules in plants, play a crucial role in determining biosynthetic pathways in secondary metabolism because of their strict substrate specificity. Using three O-methyltransferase (OMT) cDNAs that are involved in berberine biosynthesis, we investigated the structure that was essential for this substrate specificity and the possibility of creating a chimeric enzyme with novel substrate specificity. Since each OMT has a relatively well-conserved C-terminal putative S-adenosyl-L-methionine-binding domain, we first exchanged the N-terminal halves of different OMTs. Among the 6 combinations that we tested for creating chimeric OMTs, 5 constructs produced detectable amounts of recombinant proteins, and only one of these with an N-terminal half of 6-OMT and a C-terminal half of 4′-OMT (64′-OMT) showed methylation activity with isoquinoline alkaloids as a substrate. Further enzymological analysis of 64′-OMT reaction product indicated that 64′-OMT retained the regio-specificity of 6-OMT. Further examination of the N-terminal region of 64′-OMT showed that about 90 amino acid residues in the N-terminal half were critical for reaction specificity. The creation of OMTs with novel reactivity is discussed. 相似文献
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Mosquito flight tones occur during locomotion and courtship and are mostly analyzed using microphones. The use of microphones is impractical for analyzing the wingbeat of non-tethered insects especially if one is interested in studying the frequency content of wingbeats of a large number of insects. In this study we present a practical setting based on a novel 2D optical sensor that we embed inside insectary cages to record the wingbeats of three mosquito species belonging to three different genera, namely Culex pipiens molestus, Anopheles gambiae and Aedes albopictus. We show that this setting allows to automatically create distributions of parameters related to wingbeat frequency and harmonic properties derived from many non-tethered wingbeats and therefore characterize the wingbeat properties of a whole species with increased confidence. Implications for potential applications are discussed. 相似文献
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ZnO thin films, as polymer protection layers against ultraviolet radiation, were deposited on polyimide foil substrates using cathodic vacuum arc deposition technique. X-ray diffraction results showed that all the samples had (0 0 2) preferred orientation and the FWHM decreased as the position angle decreased. A fragmentation test was employed to investigate the influence of substrate position angle on the adhesion of ZnO thin films. It was found that the intrinsic adhesion between the ZnO film and the polyimide substrate is about 60 MPa at the substrate position angle of 0°. When the position angle increases to ±60°, the value of intrinsic adhesion decreases to about 30 MPa. 相似文献
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The Kirchhoff diffraction theory is applied to the multi-pinhole aperture diffraction screens, and the intensity, the zero-contour of the real and imaginary parts of complex amplitude and the phase distribution in deep Fresnel diffraction region are simulated. It is found that the number of bright spots, the zero-contours of the real and imaginary parts of complex amplitude and the phase singularities are all related to number of pinholes in diffraction screens. The brightness of bright spots in center of each pattern would become larger with increasing number of pinholes. In addition, there are many lines, on which the intensity value is close to 0. 相似文献
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A study on interface states density distribution and characteristic parameters of the In/SiO2/p-Si (MIS) capacitor has been made. The thickness of the SiO2 film obtained from the measurement of the corrected capacitance in the strong accumulation region for MIS Schottky diodes was 220 Å. The diode parameters from the forward bias I-V characteristics such as ideality factor, series resistance and barrier heights were found to be 1.75, 106-112 Ω and 0.592 eV, respectively. The energy distribution of the interface state density Dit was determined from the forward bias I-V characteristics by taking into account the bias dependence of the effective barrier height. The interface state density obtained using the I-V characteristics had an exponential growth, with bias towards the top of the valance band, from 9.44×1013 eV−1 cm−2 in 0.329-Ev eV to 1.11×1013 eV−1 cm−2 in 0.527-Ev eV at room temperature. Furthermore, the values of interface state density Dit obtained by the Hill-Coleman method from the C-V characteristics range from 52.9×1013 to 1.11×1013 eV−1 cm−2 at a frequency range of 30kHz-1 MHz. These values of Dit and Rs were responsible for the non-ideal behaviour of I-V and C-V characteristics. 相似文献
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Sasaki S 《Proceedings of the Japan Academy. Series B, Physical and biological sciences》2008,84(2):31-57
The physiological characteristics of the dominant tree species in the tropical rain forest mainly belonging to dipterocarps as well as the environmental conditions especially for the light in the forest were studied to establish the silvicultural system for the forest regeneration in the tropical South Asia. The flowering patterns of the dipterocarp trees are usually irregular and unpredictable, which make difficult to collect sufficient seeds for raising the seedlings. The field survey revealed the diverged features of the so-called gregarious or simultaneous flowering of various species of this group. Appropriate conditions and methods for the storage of the seeds were established according to the detailed analyses of the morphological and physiological characteristics of the seeds such as the low temperature tolerance and the moisture contents. The intensity and spectra of the light in the forest primarily determine the growth and the morphological development of the seedlings under the canopy. Based on the measurements of the diffused light at the sites in the tropical forest in the varying sunlight, the parameters such as "the steady state of the diffuse light" and "the turning point" were defined, which were useful to evaluate the light conditions in the forest. To improve the survival of the transplanted seedlings, a planting method of "the bare-root seedlings", the seedlings easy to be handled by removal of all leaves, soil and pots, was developed. Its marked efficiency was proved with various dipterocarps and other tropical trees by the field trial in the practical scale. Tolerance of the various species to the extreme environmental conditions such as fires, acid soils and drought were examined by the experiments and the field survey, which revealed marked adaptability of Shorea roxburghii as a potential species for regeneration of the tropical forests. 相似文献