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111.
112.
The micrometric changes over the size of the objects produced by the temperature variations can create deleterious effects; the decoupling of soldering points in electronic circuits is one of them. In this work, we present a system based on digital holographic interferometry to quantify the magnitude of the changes produced on an electronic circuit board as it operates at very low electric currents. For the system to work, two digital holograms of the object are registered for different temperatures. These holograms are reconstructed numerically in a computer by using Fresnel's approximation to make a phase difference map. This map is converted into micrometer size variations by means of a lookup table. The implemented system allows for determining mechanical deformations in the range of 0.5–4 μm for a regular electronic circuit board drawing an electric current from 10 μA to 50 μA. 相似文献
113.
The stability and electronic properties of carbon in α-Al2O3 are investigated using density functional theory. In the host lattice, the substitutional C prefers the Al site under the O-rich conditions, whereas the O site is preferred by carbon under the Al-rich conditions. The calculated results predict a direct relationship between the thermodynamic and optical transition levels with the degree of the local distortion induced by C in the alumina lattice. We also find C at the O site acts as a charge compensator to stabilize the F+ center, thereby enhancing the TL signal at 465 K. Also, C at Al site can serve as electron traps for TL emission process in α-Al2O3. 相似文献
114.
S. Bagˇcı H.M. Tütüncü S. Duman E. Bulut M. Özacar G.P. Srivastava 《Journal of Physics and Chemistry of Solids》2014
We have performed an ab initio study of structural, electronic, magnetic, vibrational and thermal properties of the cubic spinel LiMn2O4 by employing the density functional theory, the linear-response formalism, and the plane-wave pseudopotential method. An analysis of the electronic structure with the help of electronic density of states shows that the density of states at the Fermi level (N (EF)) is found to be governed by the Mn 3d electrons with some contributions from the 2p states of O atoms. It is important to note that the contribution of Mn 3d states to N(EF) is as much as 85%. From our phonon calculations, we have obtained that the main contribution to phonon density of states (below 250 cm−1) comes from the coupled motion of Mn and O atoms while phonon modes between 250 cm−1 and 375 cm−1 are characterized by the vibrations of all the three types of atoms. The contribution from Li increases rapidly at higher frequency (above 375 cm−1) due to the light mass of this atom. Finally, the specific heat and the Debye temperature at 300 K are calculated to be 249.29 J/mol K and 820.80 K respectively. 相似文献
115.
116.
为了获得准确的面形测量,提出了一种相移电子散斑干涉技术测量物体面形的测量方法.利用电子散斑干涉产生载波条纹,该载波条纹受到物体表面高度的调制变得弯曲,引起载波条纹相位的变化,可运用相移技术提取物体的相位信息,最后根据高度和相位之间的关系得到物体的面形.介绍了该方法的原理,利用该方法对球冠物体进行了面形测量,证明该方法测量物体面形是可行性的.由于是采用散斑干涉的方法产生干涉条纹,因此该方法测量物体面形具有灵敏度高的优点. 相似文献
117.
为满足卫星激光通信中超高速数据传输的特殊要求,采用电子束和离子辅助沉积技术,制备了532 nm、632 nm和1 064 nm波长处高反射,808 nm和1 550 nm处高透射的多波段滤光膜.选取了H4和SiO2作为高低折射率材料,通过对膜系设计曲线的不断优化,减少了灵敏层的个数,得到了相对易于制备的膜系结构;采用电子束加热蒸发方法并加以离子辅助沉积系统制备薄膜, 采用光控与晶控同时监控的方法控制膜厚;通过不断调整工艺,提高了薄膜的抗激光损伤能力,减小了膜厚控制误差,提高了透射波段的透过率及反射波段的反射率,最终得到了光谱性能较好的滤光膜.该薄膜能够承受雨淋、盐雾、高低温等环境测试,满足使用要求. 相似文献
118.
Chao Zhang Yongzhong Jia Yan Jing Ying Yao Jun Ma Jinhe Sun 《Physica B: Condensed Matter》2012,407(24):4649-4654
The electronic structures and optical properties of N-doped, S-doped and N/S co-doped SrTiO3 have been investigated on the basis of density functional theory (DFT) calculations. Through band structure calculation, the top of the valence band is made up of the O 2p states for the pure SrTiO3. When N and S atoms were introduced into SrTiO3 lattice at O site, the electronic structure analysis shows that the doping of N and S atoms could substantially lower the band gap of SrTiO3 by the presence of an impurity state of N 2p on the upper edge of the valence band and S 2p states hybrid with O 2p states, respectively. When the N/S co-doped, the energy gap has further narrowing compared with only N or S doped SrTiO3. The calculations of optical properties also indicate a high photo response for visible light for N/S co-doped SrTiO3. Besides, we find a new impurity state which separates from the O 2p states could improve the photocatalytic efficiency and we also propose a model for light electron-hole transportation which can explain the experiment results well. All these conclusions are in agreement with the recent experimental results. 相似文献
119.
Zhi-Sheng Nong Jing-Chuan Zhu Xia-Wei Yang Yong Cao Zhong-Hong Lai Yong Liu 《Physica B: Condensed Matter》2012,407(24):4706-4711
The structural, elastic and electronic properties of Al2La, AlLa3 and Al3La binary intermetallics in the Al–La alloy system were investigated using the first-principles method. The calculated lattice constants were consistent with the experimental values. Formation enthalpy and cohesive energy showed that the studied Al2La, AlLa3 and Al3La all have a higher structural stability, and the alloying ability of Al2La and Al3La is stronger than that of AlLa3. The single-crystal elastic constants (Cij) as well as polycrystalline elastic parameters (bulk modulus B, shear modulus G, Young's modulus E, Poisson's ratio υ and anisotropy value A) were calculated by the Voigt–Reuss–Hill (V–R–H) approximations, and the relationship of these elastic parameters between Al2La, AlLa3 and Al3La phases were discussed in detail. The results showed that Al2La and Al3La which are anisotropic materials are absolutely brittle, while the isotropic AlLa3 is slightly ductile. Finally, the electronic density of states (DOS) was also calculated to reveal the underlying mechanism of structural stability. 相似文献
120.
S. Amari S. MéçabihB. Abbar N. BenosmanB. Bouhafs 《Physica B: Condensed Matter》2012,407(17):3639-3645
We have investigated the structural, electronic and magnetic properties of substitutional europium rare earth impurity in cubic CdS and CdSe by employing the ab-initio method. Calculations were performed by using the full potential linearized augmented plane wave plus local orbitals (FP-L/APW+lo) method within the framework of spin-polarized density functional theory (DFT). The electronic exchange-correlation energy is described by generalized gradient approximation GGA and GGA+U (U is the Hubbard correction). The GGA+U method is applied to the rare-earth 4f states. We have calculated the lattice parameters, bulk modulii, the first pressure derivatives of the bulk modulii and the cohesive energies. The calculated densities of states presented in this study identify the metallic behavior of CdEuS and CdEuSe when we use the GGA scheme, whereas when we use the GGA+U, we see that these compounds are half-metallic. 相似文献