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91.
Uniaxial stress influence on lattice, band gap and optical properties of n-type ZnO: first-principles calculations 下载免费PDF全文
The lattice,the band gap and the optical properties of n-type ZnO under uniaxial stress are investigated by firstprinciples calculations.The results show that the lattice constants change linearly with stress.Band gaps are broadened linearly as the uniaxial compressive stress increases.The change of band gap for n-type ZnO comes mainly from the contribution of stress in the c-axis direction,and the reason for band gap of n-type ZnO changing with stress is also explained.The calculated results of optical properties reveal that the imaginary part of the dielectric function decreases with the increase of uniaxial compressive stress at low energy.However,when the energy is higher than 4.0 eV,the imaginary part of the dielectric function increases with the increase of stress and a blueshift appears.There are two peaks in the absorption spectrum in an energy range of 4.0-13.0 eV.The stress coefficient of the band gap of n-type ZnO is larger than that of pure ZnO,which supplies the theoretical reference value for the modulation of the band gap of doped ZnO. 相似文献
92.
G. V. Kulak 《Journal of Applied Spectroscopy》1999,66(2):302-305
The specific features are considered of the noncollinear optoacoustic interaction in uniaxial gyrotropic quartz crystals in
an intermeadiate regime of diffraction close to the Bragg regime. A system of equations of coupled waves is presented which
describes the optoacoustic interaction in uniaxial gyrotropic crystals in the Raman-Nath, intermedaite, and the Bragg regimes
of diffraction. The dependences of the diffraction efficiency on the ultrasonic wave intensity, the optoacoustic interaction
length, and on the incident light polarization are investigated. A multispike structure of the Bragg maximum is studied that
appears in accounting for the crystal gyrotropy. A good agreement between the theoretical calculations and the known experimental
results for a quartz crystal is shown.
Mozyr State Pedagogical Institute, 28, Studencheskaya Str., Mozyr, 247760, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii,
Vol. 66, No. 2, pp. 278–281, March–April, 1999. 相似文献
93.
混凝土单轴受拉的非局部本构模型 总被引:1,自引:0,他引:1
混凝土受拉本构行为存在很强的局部软化现象,使得单轴受拉试验无法给出应力-应变关系,而只能给出应力-位移关系。本文根据内变量理论和等效应变假设建立了基于真实应变的混凝土单轴受力本构方程,并根据Weibull分布可以描述混凝土等脆性材料断裂过程的试验现象,建立了关于弹性应变的损伤演化规律。然后,通过假设平均应变与真实弹性应变的函数关系,在应力-平均应变的本构关系中采用平均弹性应变以描述其非局部行为,而在材料的损伤演化规律中采用真实弹性应变以描述其局部行为,由此建立了单轴受拉荷载条件下的非局部本构模型。最后,对一个单调受拉试验和一个反复受拉试验的仿真结果表明所提出的非局部本构模型可以准确地模拟试验结果。 相似文献
94.
Shahida Sadiqi Muhammad Hamza Farooq Ali Sadia Alam Qismat Shakeela Shehzad Ahmed Asma Ayaz Sajid Ali Saddam Saqib Fazal Ullah Wajid Zaman 《Molecules (Basel, Switzerland)》2022,27(19)
Some soil microbes, with their diverse inhabitance, biologically active metabolites, and endospore formation, gave them characteristic predominance and recognition among other microbial communities. The present study collected ten soil samples from green land, agricultural and marshy soil sites of Khyber Pakhtunkhwa, Pakistan. After culturing on described media, the bacterial isolates were identified through phenotypic, biochemical and phylogenetic analysis. Our phylogenetic analysis revealed three bacterial isolates, A6S7, A1S6, and A1S10, showing 99% nucleotides sequence similarity with Brevibacillus formosus, Bacillus Subtilis and Paenibacillus dendritiformis. The crude extract was prepared from bacterial isolates to assess the anti-bacterial potential against various targeted multidrug-resistant strains (MDRS), including Acinetobacter baumannii (ATCC 19606), Methicillin-resistant Staphylococcus aureus (MRSA) (BAA-1683), Klebsiella pneumoniae (ATCC 13883), Pseudomonas aeruginosa (BAA-2108), Staphylococcus aureus (ATCC 292013), Escherichia coli (ATCC25922) and Salmonella typhi (ATCC 14028). Our analysis revealed that all bacterial extracts possess activity against Gram-negative and Gram-positive bacteria at a concentration of 5 mg/mL, efficiently restricting the growth of E. coli compared with positive control ciprofloxacin. The study concluded that the identified species have the potential to produce antimicrobial compounds which can be used to control different microbial infections, especially MDRS. Moreover, the analysis of the bacterial extracts through GC-MS indicated the presence of different antimicrobial compounds such as propanoic acid, oxalic acid, phenol and hexadecanoic acid. 相似文献
95.
人工冻土力学性能影响因素敏感性分析 总被引:3,自引:0,他引:3
为分析人工冻土单轴抗压强度影响因素敏感性,选定人工冻土单轴抗压强度的7 种影响因素,按正交试验设计方案进行大量冻土单轴压缩试验,并采用灰色关联理论对试验结果进行分析,研究分析诸因素敏感性排列顺序. 试验结果表明:在选定的7 种影响因素中,温度为最大敏感因素,其它依次为深度、土性、养护时间、加载速率、含水率和密度,且选定的7 种因素均为重要影响因素,为相关室内试验与工程应用提供依据. 相似文献
96.
97.
为研究层状复合岩石高温作用下的力学特性,对相似材料制备的层状复合岩石进行20℃(室温),100℃,200℃和300℃热处理,并开展单轴压缩试验获取其物理力学参数。结果表明,随着温度升高,层状复合岩石质量变化率与体积膨胀率呈上升趋势,且在100℃时增幅明显。拟合各力学参数的经验公式发现,峰值强度及弹性模量趋于劣化并呈线性降低,峰值应变与温度成正相关。随着温度升高,层状复合岩石呈剪切–滑移型破坏,单一类岩石由剪切破坏向张拉–剪切破坏转化,破坏时微裂纹数量增多,在300℃时延性特征显著。引入考虑温度效应的岩石本构模型并拟合了不同温度下的应力应变曲线,该模型较好地表征了热处理后层状复合岩石的损伤演化规律及破坏特征,合理地揭示了层状复合岩石高温作用后的损伤机理。
相似文献98.
Jie Xu 《Liquid crystals》2018,45(1):22-31
The orientational elasticity of the uniaxial and the biaxial nematic phases is deduced earlier. For bent–core molecules with hardcore interaction, we examine how the molecular shape affects the elastic constants of these phases. The calculation is built on a tensor model based on the Onsager theory. The elastic constants are expressed by the coefficients in the tensor model, and these coefficients are derived from molecular parameters. We calculate the elastic constants of bent–core molecules as functions of the bending angle, concentration and thickness. We also examine the elastic constants of star molecules, where we focus on the effect of the extra arm. 相似文献
99.
Leonid I. Muravsky Olexander P. Maksymenko Olexander M. Sakharuk 《Optics Communications》2004,240(4-6):275-291
The optical speckle–displacement correlation technique (OSDCT) is proposed for study of in-plane speckle displacements. The joint transform correlator architecture is used to evaluate the displacements of speckle subimages of strained surfaces. The procedure of the correlation response producing as a result of cross-correlation of strainless and strained surfaces in a conventional joint transform correlator (JTC) is considered. The convenient techniques for a joint power spectrum transformation are selected. The systematic and random errors of a mean speckle pattern displacement of a rigid body motion calculated by using the OSDCT and the digital speckle–displacement measurement technique are compared. The robustness of some JTC versions (a conventional JTC, a JTC with median thresholding, a JTC with subset median thresholding, and a fringe adjusted filter JTC) to input noise of speckle patterns and output noise of a correlation response is studied. 相似文献
100.
V. D. Bondar’ 《Journal of Applied Mechanics and Technical Physics》2007,48(3):460-466
Antiplane strain of a cylindrical elastic body undergoing large rotations under surface load in the absence of body loads
is studied. The form of the elastic potential corresponding to this strain is found. The stresses, the strains, and the displacement
are expressed in terms of pressure and two independent strains and the pressure is expressed in terms of the linear strain
invariant. For the strains and displacement, nonlinear boundary-value problems are formulated and their ellipticity conditions
are given. The linear problem for the displacement is obtained by transformation of variables. An example of determining the
displacement is considered.
__________
Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 3, pp. 191–198, May–June, 2007. 相似文献