小型米散射激光雷达的研制及其探测

介绍了一台自行研制的用于大气气溶胶光学特性和水平能见度测量的小型米散射激光雷达系统,并进行了一系列观测实验和分析.系统选用532nm波长激光作为光源,采用Fernald反演算法对接收到的大气回波信号进行反演得到气溶胶消光系数.通过对西安城区上空的气溶胶光学特性进行连续观测,测得了西安城区不同时刻消光系数的高度分布廓线、以及24小时内大气边界层高度的时空变化特性,并对大气水平能见度进行了连续观测,其结果与当地气象部门提供的水平能见度数据的变化趋势基本一致.观测结果表明,利用该米散射激光雷达可以对大气气溶胶光学特性和水平能见度进行有效测量.     

Horizontal parallax distortion in toed-in camera with wide-angle lens for mobile device

An effect of the toed-in camera configuration is keystone distortion, which causes vertical and horizontal parallax in the stereoscopic image. The horizontal parallax is the source of the depth plane curvature. However, if the stereoscopic image captured by the toed-in camera system with fish-eye lens is displayed on mobile device, it is uncomfortable to view because the horizontal parallax contains horizontal parallax distortion occurred by the wide field of view of the lenses. Therefore, in this paper, we propose a novel correction method of the horizontal parallax distortion, which is one of the keystone distortions, in a toed-in camera with fish-eye lenses for mobile device. We have experimented to attest the proposed method. In experiment, we used two charge coupled device cameras, whose field of view is 48.48°. In addition, the captured stereoscopic image was corrected for the barrel distortion and the horizontal parallax distortion. Therefore, the proposed method provides correcting of the horizontal parallax distortion from a toed-in camera system in order that the users can enjoy three-dimensional effects without the visual fatigue. Additionally, the proposed method is able to apply to toed-in camera consisting of any kinds of cameras.     

Three-dimensional modelling of steam flush for DNAPL site remediation

Numerical simulation of steam flush for clean-up of non-aqueous phase liquid (NAPL) contaminated groundwater sites involves solution of the multiphase, multicomponent subsurface flow equations. This paper describes techniques for discretizing problems with horizontal wells in a three-dimensiontetrahedral mesh. The effectiveness of non-linear flux limiters for reducing numerical dispersion is discussed. Primary variable selection and thermodynamic state transition rules will also be compared. Some example results for several steam flush scenarios will be presented.     

Logistic方程的紊动现象

对于单参数二维映射ｆ（ｘ，ｙ）＝（ｙ，μｙ（１－ｘ）），本文给出使ｆ存在Ｓｍａｌｅ马蹄的两个参数区间，从而对Ｌｏｇｉｓｔｉｃ方程的一些数值计算结果作出理论上的解释。     

On the phase inversion process in an oil–water pipe flow

An experimental study of the phase inversion process in an oil–water flow through a pipe was carried out. Special attention was paid to the critical concentration of the dispersed phase at which phase inversion occurs and to the change in morphological structures during inversion. To that purpose two different types of experiments were performed: (1) continuous experiments during which the dispersed phase fraction was gradually increased and (2) direct experiments whereby oil and water were injected simultaneously into the pipe at a certain concentration. During the experiments detailed pictures were taken of the phase inversion process and simultaneously the electrical conductivity of the mixture was measured to determine which liquid formed the continuous phase and which the dispersed phase. Also the pressure gradient over several parts of the pipe was measured.     

Optimal placement of a wellbore seal impeding seepage from a tilted fracture

Steady, one-phase, 2D Darcian seepage in a homogeneous pay from one horizontal isobar to another with a tilted fracture intersecting the two isobars is studied by the methods of complex analysis. The shortcut through the fracture is foiled by an impermeable seal of a constant length which is placed at the fracture-isobar intersection with an objective to minimise either the total flow rate from the fracture or the travel time of marked particles moving along the seal. Conformal mappings of the slanted-face half-strip in the physical domain onto a half-strip in the complex potential domain give explicit expressions of the seepage rate and travel time through hypergeometric functions. The optimal seal position is found by computer algebra routines for any given distance between isobaric horizons, tilt angle, pressure drop between isobars and hydraulic conductivity of the rock.     

2D numerical manifold method based on quartic uniform B-spline interpolation and its application in thin plate bending

A new numerical manifold （NMM） method is derived on the basis of quartic uniform B-spline interpolation. The analysis shows that the new interpolation function possesses higher-order continuity and polynomial consistency compared with the conven- tional NMM. The stiffness matrix of the new element is well-conditioned. The proposed method is applied for the numerical example of thin plate bending. Based on the prin- ciple of minimum potential energy, the manifold matrices and equilibrium equation are deduced. Numerical results reveal that the NMM has high interpolation accuracy and rapid convergence for the global cover function and its higher-order partial derivatives.     

An attempt to reduce the membrane effects in Richtmyer–Meshkov instability shock tube experiments

A new device has been developed to reduce the effects of the initial materialization of the gaseous interface in the context of horizontal shock tube experiments for the Richtmyer–Meshkov instability study. The thin nitrocellulosic membrane deposited on a stereolithographed grid support woven with thin wires is destroyed by thermal effect, through a powerful electrical pulse, just before the arrival of the incident shock wave. We present a first attempt realized in the light/heavy gas configuration (air/SF₆) and compared with the experiments carried out without destruction. We show that the present device allows to reduce the influence of the membrane on the instability development.