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71.
X.-M. Su Z.-C. Zhuo Z.-H. Kang L.-J. Wang J.-Y. Gao 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,17(3):395-398
We investigate the conditions in which the propagation of an electromagnetic wave is changed from transparency to cutoff in
a non-uniform plasma. The allowed frequency range of the driving wave is obtained for the case that the probe frequency is
above the plasma frequency. The effect of the power of the driving field on the range is analyzed.
Received 23 May 2001 相似文献
72.
Akira Ozawa 《Pramana》2001,57(2-3):525-533
Recent experimental programs at RIKEN concerning RI beams are reviewed. RIKEN has the ring cyclotron (RRC) with high intense
heavy-ion beams and large acceptance fragment separator, RIPS. The complex can provide high intense RI-beams. By using the
high intense RI-beams, a variety of experiments have been done. Recently, nuclear structure for unstable nuclei has been paid
much attention. In special, disappearance and appearance of magic numbers are discussed experimentally and theoretically.
Thus, in this review, related experiments concerning disappearance and appearance of magic numbers are described. Finally,
future project in RIKEN, RI-beam factory. is introduced briefly. 相似文献
73.
74.
This paper deals with a new solution technique for approximately solving certain variational problems in elasticity by using discrete optimization techniques that were originally used in information theory. This allows us to easily and approximately solve large deformation buckling problems for slender cantilever beams (including post-buckling behavior) as well as problems where the strain energy function is non-convex.The core idea is to quantize or discretize the variables describing the possible configurations of the body. This, when combined with the fact that the variational problem has an inherent Markov structure allows us to use computationally efficient search techniques based on dynamic programming (equivalent to finding the shortest path in a weighted directed graph) to find optimal solutions within the quantized state space. The results can be used in two ways: (1) directly as a fast approximate solution to the variational problem (2) As a means for finding very good (nearly minimum energy) initial configurations for application of conventional minimization techniques, which might otherwise fail because of a poor starting configurations which are far from the global minimum. We demonstrate both these uses in the paper. 相似文献
75.
As a first endeavor, a mixed differential quadrature (DQ) and finite element (FE) method for boundary value structural problems in the context of free vibration and buckling analysis of thick beams supported on two-parameter elastic foundations is presented. The formulations are based on the two-dimensional theory of elasticity. The problem domain along axial direction is discretized using finite elements. The resulting system of equations and the related boundary conditions are discretized in the thickness direction and in strong-form using DQM. The method benefits from low computational efforts of the DQ in conjunction with the effectiveness of the FE method in general geometry and systematic boundary treatment resulting in highly accurate and fast convergence behavior solution. The boundary conditions at the top and bottom surface of the beams are implemented accurately. The presented formulations provide an effective analysis tool for beams free of shear locking. Comparisons are made with results from elasticity solutions as well as higher-order beam theory. 相似文献
76.
Keiji Kataoka 《Optical Review》2008,15(4):196-203
In the slant scanning method of multiple beams a misalignment of the slant angle causes a beam spacing error and pitch irregularities
of scan lines called “banding”. This paper evaluates the pitch irregularities and tries to clarify the allowable beam spacing
error. The following results are obtained: (1) The maximum spacing error of print lines is proportional to m/(dpi), where m is the number of multiple beams and dpi print dot density. (2) The noticeable limit of periodic variations of print density
at low spatial frequency was presumed to be a visibility between 1 and 2% in experiments. (3) The allowable beam spacing error
was calculated introducing the human eye spatial frequency response. (4) The banding simulation experiments by laser recording
on the photographic paper on the XY stage showed good coincidence with the theoretical evaluations. 相似文献
77.
A. Chafiq 《Optics Communications》2006,265(2):594-602
Using Collins formula and the expansion of Mathieu beams in terms of Bessel beams we derive the exact propagation equations of Mathieu-Gauss beams through an apertured paraxial ABCD optical system. A comparison between the exact propagation equations and the approximated ones, which are derived by expanding the circ function into a finite sum of Gaussian functions, is presented. The propagation characteristics of zeroth-order Mathieu-Gauss beams in (y-z) and (x-z) planes are analyzed with detailed numerical calculations. It is found that the profile of the propagated Mathieu-Gauss beam is similar to that of Bessel-Gauss beam. Furthermore, the focalization of the Mathieu-Gauss beams through a thin lens is illustrated and analyzed with numerical results. 相似文献
78.
79.
Polarized photoluminescence spectroscopy in WS2, WSe2 atomic layers and heterostructures by cylindrical vector beams 下载免费PDF全文
Due to the large exciton binding energy, two-dimensional (2D) transition metal dichalcogenides (TMDCs) provide an ideal platform for studying excitonic states and related photonics and optoelectronics. Polarization states lead to distinct light-matter interactions which are of great importance for device applications. In this work, we study polarized photoluminescence spectra from intralayer exciton and indirect exciton in WS2 and WSe2 atomic layers, and interlayer exciton in WS2/WSe2 heterostructures by radially and azimuthally polarized cylindrical vector laser beams. We demonstrated the same in-plane and out-of-plane polarization behavior from the intralayer and indirect exciton. Moreover, with these two laser modes, we obtained interlayer exciton in WS2/WSe2 heterostructures with stronger out-of-plane polarization, due to the formation of vertical electric dipole moment. 相似文献
80.
A. D. Matveev 《Journal of Applied Mechanics and Technical Physics》2004,45(4):591-597
Mixed formulations of bending problems for homogeneous plates (beams) are proposed, whose essence is that the deformation of a plate (beam) near its fixed boundary is described by the threedimensional elasticity equations, and the remaining part by the conventional equations of plate (beam) bending. At the interface between these regions, the solutions of these equations are joined. The mixed formulation allows one to describe the threedimensional stress state in the neighborhood of the fixed boundaries of plates (beams) and take into account the complex nature of the fixing conditions. Finiteelement implementation is more efficient for the mixed formulations of plate (beam) bending problems than for the wellknown threedimensional formulations. 相似文献