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51.
Starting from the vectorial Rayleigh diffraction integral formula and without using the far-field approximation, a solution of the wave equation beyond the paraxial approximation is found, which represents vectorial non-paraxial elliptical Gaussian beams in free space. The far-field expressions for non-paraxial Gaussian beams and elliptical Gaussian beams can be regarded as special cases treated in this paper. Some basic propagation properties of vectorial non-paraxial elliptical Gaussian beams, including the irradiance distribution, phase term, beam widths and divergence angles are studied. Numerical results are given and illustrated. 相似文献
52.
基于CVaR风险计量技术,分别给出了正态和t分布情形下资产组合的CVaR值,对一般情形下风险资产组合的CVaR风险关于头寸的敏感度进行了分析,研究了其经济意义。 相似文献
53.
L. V. Stepanova 《Journal of Applied Mechanics and Technical Physics》2008,49(1):142-147
This paper discusses the problem of finding the eigenvalue spectrum in determining the stress and strain fields at the tip
of an antiplane-shear crack in a power-law material. It is shown that the perturbation method provides an analytical dependence
of the eigenvalue on the material nonlinearity parameter and the eigenvalue of the linear problem. Thus, it is possible to
find the entire spectrum of eigenvalues and not only the eigenvalue of the Hutchinson-Rice-Rosengren problem.
__________
Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 49, No. 1, pp. 173–180, January–February, 2008. 相似文献
54.
K. Suzuki S. Miyashita K. Takashina Y. Hirayama 《Physica E: Low-dimensional Systems and Nanostructures》2004,20(3-4):232
We investigate the quantum Hall effect (QHE) in the InAs/GaSb hybridized electron–hole system grown on a conductive InAs substrate which act as a back-gate. In these samples, the electron density is constant and the hole density is controlled by the gate-voltage. Under a magnetic field perpendicular to the sample plane, the QHE appears along integer Landau-level (LL) filling factors of the net-carriers, where the net-carrier density is the difference between the electron and hole densities. In addition, longitudinal resistance maxima corresponding to the crossing of the extended states of the original electron and hole LLs make the QHE regions along integer-νnet discontinuous. Under tilted magnetic fields, these Rxx maxima disappear in the high magnetic field region. The results show that the in-plane magnetic field component enhances the electron–hole hybridization and the formation of minigaps at LL crossings. 相似文献
55.
C.Q. Ru 《International Journal of Non》2003,38(4):521-530
This paper gives an asymptotic analysis of the deformation field near the tip of an arbitrary mixed-mode crack in a compressible hyperelastic harmonic material which loses ellipticity at sufficiently large deformations. It is found that the near-tip deformation field is characterized by a localized non-elliptic deformation band issuing from the crack-tip and bounded by two curves of discontinuous deformation gradient. Explicit expression for the near-tip deformation field is obtained both inside and outside the localized deformation band. In particular, a simple relation is derived that determines the orientation of the deformation band in terms of two complex governing parameters of the near-tip fields inside and outside the deformation band, respectively. 相似文献
56.
陈化温度和Fe/Zr配比对SO42-/Fe2O3-ZrO2固体超强酸结构与性能的影响 总被引:6,自引:0,他引:6
用低温陈化法制备了SO42 -/Fe2 O3 ZrO2 (简称SFZ)固体超强酸催化剂 ,用红外光谱 (IR)和X光衍射(XRD)对其结构进行了表征 ,并考察了它对合成癸二酸二正丁酯的催化性能 .IR谱显示 ,低温陈化的SFZ样品在10 70cm-1处吸收峰远强于常温陈化样品 .XRD分析则显示 ,在焙烧温度为 6 5 0℃、Fe/Zr为 2∶1时 ,低温陈化的样品出现了亚稳态的ZrO2 四方晶相 .该样品在催化酯化反应中使产率达 90 %以上 ,高于常温陈化样品的 30 % .研究结果表明 :在其他条件不变时 ,低温陈化所出现的亚稳态的ZrO2 四方晶相是表面酸性和催化活性增加的微观原因 相似文献
57.
We prove that simply connected open manifolds of bounded geometry, linear growth and sublinear filling growth (e.g. finite filling area) are simply connected at infinity. 相似文献
58.
I. M. Lavit Nguyen Viet Trung 《Journal of Applied Mechanics and Technical Physics》2008,49(3):491-499
The thermoelastoplastic fracture mechanics problem of a thick-walled cylinder subjected to internal pressure and a nonuniform
temperature field is solved by the method of elastic solutions combined with the finite-element method. The correctness of
the solution is provided by using the Barenblatt crack model, in which the stress and strain fields are regular. The elastoplastic
problem of a cracked cylinder subjected to internal pressure and a nonuniform temperature field are solved. The calculation
results are compared with available data.
__________
Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 49, No. 3, pp. 173–183, May–June, 2008. 相似文献
59.
Applying Parikh-Wilzcek‘s semi-classical quantum tunneling model, we study the Hawking radiation of charged particles as tunneling from the event horizon of a cylindrically symmetric black hole in anti-de Sitter space-time.The derived result shows that the tunneling rate of charged particles is related to the change of Bekenstein-Hawking entropy and that the radiation spectrum is not strictly pure thermal after taking the black hole background dynamical and self-gravitation interaction into account, but is consistent with the underlying unitary theory. 相似文献
60.
A. C. Orifici R. S. Thomson R. Degenhardt C. Bisagni J. Bayandor 《Mechanics of Composite Materials》2007,43(1):9-28
Analysing the collapse of skin-stiffened structures requires capturing the critical phenomenon of skin-stiffener separation,
which can be considered analogous to interlaminar cracking. This paper presents the development of a numerical approach for
simulating the propagation of interlaminar cracks in composite structures. A degradation methodology was introduced in MSC.Marc,
which involved the modelling of a structure with shell layers connected by user-defined multiple-point constraints (MPCs).
User subroutines were written that employ the virtual crack closure technique (VCCT) to determine the onset of crack growth
and modify the properties of the user-defined MPCs to simulate crack propagation. Methodologies for the release of failing
MPCs are presented and are discussed with reference to the VCCT assumption of self-similar crack growth. The numerical results
obtained by using the release methodologies are then compared with experimental data for a double-cantilever beam specimen.
Based on this comparison, recommendations for the future development of the degradation model are made, especially with reference
to developing an approach for the collapse analysis of fuselage-representative structures.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 43, No. 1, pp. 15–42, January–February, 2007. 相似文献