共查询到18条相似文献,搜索用时 93 毫秒
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为了研究热致应力对光学元件损伤特性的影响,通过实验测试退火处理消除热应力和未消热应力石英基片的激光损伤特性,研究了热致应力对石英元件初始损伤阈值、损伤增长阈值以及损伤增长规律的影响.结果表明,热致应力对熔石英光学元件的初始损伤阈值有影响,初始损伤阈值随着热致应力增大而降低;热致应力会加剧激光引发的损伤增长,相同的激光通量下,表面应力越大的区域拥有越高的损伤增长因子,但损伤增长仍遵从指数增长规律.热致应力对损伤增长阈值没有明显的影响.本文的研究将为CO2激光预处理工艺能否被应用于大口径光学元件提供一个必要的技术参考. 相似文献
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计算了电子-正电子散射的16种极化散射截面.根据角分布的特征,它们可以分为三大类,其前向奇性分别是sin~(-4)(θ/2)、sin~(-2)(θ/2)和1.也计算了电子-电子散射的16种极化散射截面,它们既可以按前向奇性分为三大类,也可以按后向奇性分为三大类.三类奇性的特征与电子-正电子散射类似.对于三类奇性的出现给出了直观的物理说明. 相似文献
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本文用光学中Fourier变换的概念和方法处理纯物质自由枝晶尖端前沿的热势波传输问题,进而描述其凝固界面生长形态变化特征。具体做法是:先将热势波与枝晶端部作用后的传播过程用Fourier变换表示出来,从而求得了热势的空间分布,再由热势的分布特征反推出枝晶尖端界面生长形态的演化特点。这种方法还可简洁地处理界面能各向异性对界面凝固生长特征的作用问题。 相似文献
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通过准连续介质方法模拟了纳米多晶体Ni中裂纹的扩展过程.模拟结果显示:裂纹尖端的应力场可以导致晶界分解、层错和变形孪晶的形成等塑性形变,在距离裂纹尖端越远的位置,变形孪晶越少,在裂纹尖端附近相同距离处,层错要远多于变形孪晶.这反映了局部应力的变化以及广义平面层错能对变形孪晶的影响.计算了裂纹尖端附近区域原子级局部静水应力的分布.计算结果表明:裂纹前端晶界处容易产生细微空洞,这些空洞附近为张应力集中区,并可能促使裂纹沿着晶界扩展.模拟结果定性地反映了纳米多晶体Ni中的裂纹扩展过程,并与相关实验结果符合得很好 相似文献
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本文采用多尺度准连续介质法(quasi-continuum method, QC)模拟体心立方(body-centered-cubic, bcc)金属钽(Ta)Ⅱ型裂纹尖端位错的形核与发射过程,获得位错发射位置与应力强度因子关系曲线,分析裂纹尖端缺陷萌生过程,研究全位错分解以及扩展位错形成机理. 位错活动在不同阶段表现出不一致的特征,新位错的发射对于位错运动具有促进作用. 研究表明,裂纹扩展初始阶段首先萌生点缺陷,点缺陷随着加载强度增加会萌生新的点缺陷,点缺陷最终运动到边界,导致Ⅱ型断裂破坏. 在全位错发射之前有不全位错的形核与发射表明全位错的分解分步进行,从势能曲线上来看,也就是两个极小值点的形成机理不同.
关键词:
多尺度
准连续介质法
Ⅱ型裂纹
扩展位错 相似文献
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V. V. Fisanov 《Russian Physics Journal》1987,30(10):862-866
A matrix method is proposed to obtain the characteristic equations for quantities governing the degree of the field singularity on the edge of sectorial gyrotropic structures. Exact analytic solutions are analyzed for giving mixed boundary conditions on the outer faces of a wedgelike domain.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 64–69, October, 1987. 相似文献
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A.A. Kharkov 《Physics letters. A》1982,88(3):109-112
A regularization procedure is given for the stress tensor of a quantized field in a background metric. This regularization is shown to be equivalent to a covariant renormalization of constants in the generalized Einstein equations. An example of the massive spinor field in Robertson-Walker universe is considered. Regular values of the stress tensor near the cosmological singularity are found. 相似文献
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Chaos game representation (CGR) is proposed as a
scale-independent representation for DNA sequences and provides
information about the statistical distribution of oligonucleotides
in a DNA sequence. CGR images of DNA sequences represent some kinds of
fractal patterns, but the common multifractal analysis based on the
box counting method cannot deal with CGR images perfectly. Here, the
wavelet transform modulus maxima (WTMM) method is applied to the
multifractal analysis of CGR images. The results show that the
scale-invariance range of CGR edge images can be extended to three
orders of magnitude, and complete singularity spectra can be
calculated. Spectrum parameters such as the singularity spectrum
span are extracted to describe the statistical character of DNA
sequences. Compared with the singularity spectrum span, exon
sequences with a minimal spectrum span have the most uniform
fractal structure. Also, the singularity spectrum parameters are
related to oligonucleotide length, sequence component and species,
thereby providing a method of studying the length polymorphism of
repeat oligonucleotides. 相似文献
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Bojowald M 《Physical review letters》2008,100(22):221301
When quantum gravity is used to discuss the big bang singularity, the most important, though rarely addressed, question is what role genuine quantum degrees of freedom play. Here, complete effective equations are derived for isotropic models with an interacting scalar to all orders in the expansions involved. The resulting coupling terms show that quantum fluctuations do not affect the bounce much. Quantum correlations, however, do have an important role and could even eliminate the bounce. How quantum gravity regularizes the big bang depends crucially on properties of the quantum state. 相似文献
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根据本征方程,研究磁电弹性体中若干平行螺型位错与Griffith裂纹的相互作用.结合Muskhelishvili方法和算子理论,得到磁电弹性体中由位错和裂纹所诱导的应力场、电场和磁场的解析解.数值算例表明:在裂纹的端点及位错点上仍然存在应力的奇异性,离位错点越远处广义力越小,结论与已有的结果相符,证明了结论的正确性.当位错点与裂纹端点距离越近时,裂纹与位错间的应力场越小,并逐渐趋近于零. 相似文献
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J.-S. Wang 《哲学杂志》2013,93(2):225-251
In this paper, a symplectic model, based on the Hamiltonian system, is developed for analyzing singularities near the apex of a multi-dissimilar piezoelectric wedge under antiplane deformation. The derivation is based on a modified Hellinger–Reissner generalized variational principle or a differential equation approach. The study indicates that the order of singularity depends directly on the non-zero eigenvalue of the proposed Hamiltonian operator. Using the coordinate transformation technique and continuity conditions on the interface between two dissimilar materials, the orders of singularity for multi-dissimilar piezoelectric and piezoelectric–elastic composite wedges are determined. Numerical examples are considered to show potential applications and validity of the proposed method. It is found that the order of singularity also depends on the piezoelectric constant, in addition to the geometry and shear modulus. 相似文献
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《Physics letters. A》1997,229(3):173-182
The singularity confinement method is applied to the systematic derivation of the bilinear equations for discrete soliton equations. Using the bilinear forms, the N-soliton and algebraic solutions of the discrete potential mKdV equation are constructed. 相似文献
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It is shown that the existence of singularity in the centrally symmetric gravitational field, which is interpreted as a surface
with unusual physical properties, follows from equations for the action and the energy of a test particle not using Einstein
equations and their solutions. A black hole is treated as a physical model of the singularity in question. The results are
compared with the usual interpretation of the singularity in Schwarzschild solutions to Einstein equations. 相似文献