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81.
In this paper, a new finite element method for the flow analysis of the viscous incompressible power-law fluid is proposed by the use of penalty-hybrid/mixed finite element formulation and by the introduction of an alternative perturbation, which is weighted by viscosity, of the continuity equation. A numerical example is presented to exhibit the efficiency of the method.The Project Supported by the National Natural Science Foundation of China. 相似文献
82.
83.
We prove that any polyhedron in two dimensions admits a type of potential theoretic skeleton called mother body. We also show that the mother bodies of any polyhedron in any number of dimensions are in one-to-one correspondence with certain kinds of decompositions of the polyhedron into convex subpolyhedra. A consequence of this is that there can exist at most finitely many mother bodies of any given polyhedron. The main ingredient in the proof of the first mentioned result consists of showing that any polyhedron in two dimensions contains a convex subpolyhedron which sticks to it in the sense that every face of the subpolyhedron has some part in common with a face of the original polyhedron. 相似文献
84.
本文利用Cayley-Hamilton定理,给出了两种直接获得转动张量显式表示的方法。一种为只含变形梯度较低次幂的表达形式,利用此表示,获得了主转动角的计算公式和主转动轴的显式表示。而另一种则是不含复杂系数且含变量个数较少的高效获得转动张量的方法。进一步,给出了主转动角和主转动轴的一些性质。 相似文献
85.
By using Cayley-Hamilton theorem, two kinds of explicit representation for the rotation tensor are proposed. One contains
the lower powers of deformation gradient, by which the formula of the principal rotation angle and the explicit representation
of principal axis are obtained; the other, a high efficient method to obtain the rotation tensor, does not contain the complicated
coefficients and uses few variables. Some properties about the principal rotation angle and the principal rotation axis are
obtained. 相似文献
86.
B. Bureau G. Silly J. Y. Buzar C. Legein D. Massiot 《Solid state nuclear magnetic resonance》1999,14(3-4):181-190
Owing to the implementation of acquisition techniques specific for nuclei with very large quadrupolar interaction (full shifted echo and variable offset cumulative spectra (VOCS)), NMR spectra of 69Ga and 71Ga are obtained in crystallised (PbGaF5, Pb3Ga2F12, Pb9Ga2F24 and CsZnGaF6) and glassy (PbF2–ZnF2–GaF3) gallium fluorides. Simulations of both static (full echo or VOCS) and 15 kHz MAS spectra allow to obtain consistent determinations of isotropic chemical shifts and very large quadrupolar parameters (νQ up to 14 MHz). In the crystalline compounds whose structures are unknown, the number and the local symmetry of the different gallium sites are tentatively worked out. For the glassy systems, a continuous Czjzek's distribution of the NMR quadrupolar parameters accounts for the particular shape of the NMR spectrum. 相似文献
87.
In this paper, the effective pyroelectric coefficient
and polarization offset of
the compositionally step-like graded multilayer ferroelectric structures
have been studied by use of the first-principles approach.
It is exhibited that the dielectric gradient has a nontrivial influence
on the effective pyroelectric coefficient, but has a little influence
on the polarization offset; and the polarization gradient
plays an important role in the abnormal hysteresis loop phenomenon
of the compositionally step-like graded ferroelectric structures.
Moreover, the origin of the polarization offset is explored,
which can be attributed to the polarization gradient
in the compositionally step-like graded structure. 相似文献
88.
89.
A convolutional neural network approach to calibrating the rotation axis for X‐ray computed tomography
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Xiaogang Yang Francesco De Carlo Charudatta Phatak Dogˇa Gürsoy 《Journal of synchrotron radiation》2017,24(2):469-475
This paper presents an algorithm to calibrate the center‐of‐rotation for X‐ray tomography by using a machine learning approach, the Convolutional Neural Network (CNN). The algorithm shows excellent accuracy from the evaluation of synthetic data with various noise ratios. It is further validated with experimental data of four different shale samples measured at the Advanced Photon Source and at the Swiss Light Source. The results are as good as those determined by visual inspection and show better robustness than conventional methods. CNN has also great potential for reducing or removing other artifacts caused by instrument instability, detector non‐linearity, etc. An open‐source toolbox, which integrates the CNN methods described in this paper, is freely available through GitHub at tomography/xlearn and can be easily integrated into existing computational pipelines available at various synchrotron facilities. Source code, documentation and information on how to contribute are also provided. 相似文献
90.
以单束正交线偏振光为光源,利用角向偏振显示器,采用CCD摄像机进行图像采集,利用Matlab软件进行图像处理,设计了一种由He-Ne激光器、角向偏振显示器组成的偏振光偏振方向显示系统,并研究了其角度特性.实验结果表明:系统在起偏器的起偏角分别为0°、90°、180°、270°、360°时,角向偏振显示器偏振显示角度的测量准确度分别为0.480°、0.168°、0.528°、0.421°、0.340°,测量精确度分别为0.208°、0.576°、0.660°、0.603°、0.466°,测量数据拟合曲线的线性相关系数为0.999.结合1/4波片,检偏器和分光比为50:50的分束器,构建了椭圆偏振光测量系统,完成了椭圆偏振光测量实验,椭圆率为0.198. 相似文献