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891.
An approach for the three-dimensional (3D) reconstruction of architectural scenes from two un-calibrated images is described in this paper. From two views of one architectural structure, three pairs of corresponding vanishing points of three major mutual orthogonal directions can be extracted. The simple but powerful constraints of parallelism and orthogonal lines in architectural scenes can be used to calibrate the cameras and to recover the 3D information of the structure. This approach is applied to the real images of architectural scenes, and a 3D model of a building in virtual reality modelling language (VRML) format is presented which illustrates the method with successful performance. 相似文献
892.
Laser drilling of thick material using femtosecond pulse with a focus of dual-frequency beam 总被引:1,自引:0,他引:1
Laser drilling is one of the basic, most frequently performed, material removal processes. The drilling aspect ratio is theoretically limited by the size and the focal depth of the machining laser spot. The aspect ratio can be improved by using dual focus. In this paper we describe a focus of two different frequencies based on the longitudinal chromatic aberration arisen when polychromatic collimated light is incident on a positive lens element. In the experiments, a Ti:Sapphire laser of 800 nm wavelength and 150 fs pulse duration was used as a source. Two tightly focused laser spots few hundred micrometers apart from each other were formed by focusing a combined collimated laser beam which contains the fundamental optic frequency and the second harmonic optic frequency. The focus of dual-frequency beam was used to drill a 3 mm thick PMMA plate. The drilling aspect ratio of a dual-frequency beam was compared to that of a focus of single frequency beam. Experimental results reveal that dual-frequency beam increases the aspect ratio and improves the drilling quality in terms of profile of the produced features. 相似文献
893.
We report, for the first time, an efficient intra-cavity second-harmonic generation (SHG) at 1084 nm in a nonlinear optical crystal, BiB3O6(BIBO) at the direction of (θ, ?) = (170.1°, 90°), performed with a LD end-pumped cw Nd:YVO4 laser. With 590 mW diode pump power, a continuous-wave (cw) SHG output power of 19 mW at 542 nm yellow-green color has been obtained using a 1.5 mm-thick BIBO crystal. The optical conversion efficiency was 3.22%. It was found that the output wavelength could be 532 nm, 537 nm or 542 nm according to regulating the angle of BIBO. 相似文献
894.
本文给出了具有两个抛线解的中心对称三次系统存在在极限环的条件,它可能也是充要条件。 相似文献
895.
J. Glimm H.C. Kranzer D. Tan F.M. Tangerman 《Communications in Mathematical Physics》1997,187(3):647-677
The Hamilton-Jacobi equation describes the dynamics of a hypersurface in . This equation is a nonlinear conservation law and thus has discontinuous solutions. The dependent variable is a surface
gradient and the discontinuity is a surface cusp. Here we investigate the intersection of cusp hypersurfaces. These intersections
define (n-1)-dimensional Riemann problems for the Hamilton-Jacobi equation. We propose the class of Hamilton-Jacobi equations as a
natural higher-dimensional generalization of scalar equations which allow a satisfactory theory of higher-dimensional Riemann
problems. The fist main result of this paper is a general framwork for the study of higher-dimensional Riemann problems for
Hamilton-Jacobi equations. The purpose of the framwork ist to unterstand the structure of Hamilton-Jacobi wave interactions
in an explicit and constructive manner. Specialized to two-dimensional Riemann problems (i.e., the intersection of cusp curves
on surfaces embedded in ), this framework provides explicit solutions to a number of cases of interest. We are specifically interested in models
of deposition and etching, important processes for the manufacture of semiconductor chips.
We also define elementary waves as Riemann solutions which possess a common group velocity. Our second main result, for elementary
waves, is a complete characterization in terms of algebraic constraints on the data. When satisfied, these constraints allow
a consistently defined closed form expression for the solution. We also give a computable characterization for the admissibility
of an elementary wave which is inductive in the codimension of the wave, and which generalizes the classical Oleinik condition
for scalar conservation laws in one dimension.
Received: 9 September 1996 / Accepted: 22 April 1997 相似文献
896.
897.
本文对CCD摄象技术、等离子体诊断和脉冲辐射摄影的国内外最新发展作了评述,并涉及到在高技术领域的应用。 相似文献
898.
Duan-Ming Tan 《Tetrahedron letters》2005,46(3):503-505
Chiral arsinooxazoline Ru(II) complex has been found to be an efficient catalyst for asymmetric transfer hydrogenation of aromatic ketones in 2-propanol. Secondary alcohols with up to 94% enantiomeric excess were obtained at a substrate/catalyst mole ratio of 1000:1. Asymmetric kinetic resolution has also been obtained with 1-arylalkanols at room temperature with 99% ee. 相似文献
899.
This paper deals with the solvability of boundary value problems for singular integral equations of the form (i)-(ii).By an algebraic method we reduce the problem (i)-(ii) to a system of linear algebraic equations which gives all solutions in a closed form.AMS Subject Classification: 47G05, 45GO5, 45E05 相似文献
900.
Yao Shi Xin Wang Wei Li Tian-en Tan Jian-jun Ruan 《Plasma Chemistry and Plasma Processing》2006,26(2):187-196
Effects of multiple corona reactor modes on pulse characteristics, energy transfer efficiency, and odor (H2S and NH3) removal were investigated experimentally by the wire-plate corona reactor(s). The removal efficiency of H2S was only 91% and the energy consumption was 16.1 Wh m−3 by the single mode with a gas-flow rate of 23 m3 h−1 and an initial concentration of 200 mg m−3. At the same experimental conditions, almost 100% removal efficiency was achieved and the energy consumption was only 12.8 and 14.9 Wh m−3 by the series and parallel modes. In the case of 50 mg m−3 NH3 removal at the same gas-flow rate, the removal efficiencies with the single mode, the series and parallel modes were 64, 92 and 70%, respectively. The energy requirement did not increase at the same residence time under the experimental conditions of the single mode with a gas-flow rate of 11.5 m3 h−1 and the series or parallel mode with a gas-flow rate of 23.0 m3 h−1. The experimental results indicate that the series and parallel modes are effective in saving energy consumption, improving removal ability and efficiency, especially for the series mode. 相似文献