多极化SAR溢油探测影响因素分析研究

Polarimetric synthetic aperture radar(SAR) oil spill detection parameters conformity coefficient(μ), Muller matrix parameters(|C|, B_0), the eigenvalues of simplified coherency matrix(λ_(nos)) and the influence of SAR observing parameters, ocean environment and noise level are investigated. Radarsat-2 data are used to make systematic analysis of polarimetric parameters for different incidences, wind speeds, noise levels and the ocean phenomena(oil slick and look likes). The influence of the SAR observing parameters, the ocean environment and the noise level on the typical polarimetric SAR parameter conformity coefficient has been analyzed. The results indicate that conformity coefficient cannot be simply used for oil spill detection, which represents the image signal to the noise level to some extent. When the signals are below the noise level for the oil slick and the look likes, the conformity coefficients are negative; while the signals above the noise level corresponds to positive conformity coefficients. For dark patches(low wind and biogenic slick) with the signal below the noise,polarization features such as conformity coefficient cannot separate them with oil slick. For the signal above the noise, the oil slick, the look likes(low wind and biogenic slick) and clean sea all have positive conformity coefficients, among which, the oil slick has the smallest conformity coefficient, the look likes the second, and the clean sea the largest value. For polarimetric SAR data oil spill detection, the noise plays a significant role. So the polarimetric SAR data oil spill detection should be carried out on the basis of noise consideration.     

Interaction of solitary waves with emergent, rigid vegetation

In this study, solitary wave interaction with emergent, rigid vegetation was studied numerically and experimentally. Laboratory experiments were carried out in a wave flume with vegetation models of different lengths and porosities; the Boussinesq equations with the effects of the vegetation being modeled by a quadratic drag law are used to simulate the wave scattering by and the wave propagation through vegetation. Effects of incident wave height, vegetation density, and vegetation length are discussed. An empirical expression for the mean drag coefficient of emergent, rigid vegetation is presented and compared with other available data. The results are useful for studying tsunami hazard mitigation by coastal forests.     

Study of Partial Coefficients for Design of Semicircular Breakwaters

In the present study,the reliability design of semicircular breakwater is based on the verification of the rules defined by standard specifications,where partial coefficients are introduced to ensure safety.The reliability of the semicircular breakwaters has been analyzed by using the Hasofer-Lind method to determine the reliability index of structure that has correlated loads,utilizing the long-term observed wave data at a given place.The relation curve between reliability index and safety factor in the traditional design method,as well as the relationships between reliability index and partial coefficients,have been obtained.This paper proposes values of partial coefficients for the design expression of semicircular breakwaters in the cases of anti-sliding and anti-overturning.     

ZnO压敏陶瓷冲击老化的电子陷阱过程研究

使用8/20 μs脉冲电流发生器对普通商用ZnO陶瓷压敏电阻片进行了最多5000次的冲击试验.测量了冲击前后试样的电气性能和介电特性,分析了冲击后小电流区的U-I特性和损耗角正切值tanδ随脉冲大电流的不断作用而发生的变化.实验发现压敏电压U1mA随冲击次数的增加经历增大—稳定—减小三个过程.认为正反偏Schottky势垒的中性费米能级的变化是影响样品小电流区的最根本原因.本文提出用试样的非线性系数α作为老化特征参数比传统的U     

In-line response of a cylinder in oscillatory flow

The most widely used mathematical model to represent flow-induced in-line forces on structures is based on the Morison¹ equation. The present paper investigates the validity of using an extension of Morison's equation for non-stationary structures, by comparing predictions with results from a simple laboratory experiment. An elastically-mounted circular cylinder is placed in the sinusoidal flow of a U-tube, and responds in-line with the flow. Cylinder forces and responses are recorded over a range of Keulegan Carpenter numbers up to 35. An equation of motion is solved simply by using relative coordinates and by employing equivalent linearisation. The linear results are compared over a wide variation of parameters with solutions using the full nonlinear equation. Thereafter experimental results are compared with linear predictions.     

An analysis of horizontal dispersion due to the drift current with an Ekman layer

An analytical method for describing horizontal matter dispersion in shear currents is presented using a tensor expression from the point of view that matter dispersion due to the shear effect should be one of the principal mixing dilution processes. Although the behavior of horizontal dispersion is considerably more complicated than common longitudinal dispersion, the present study elucidates the vertical structure of dispersion and the dispersing process from the initial to the stationary stage, besides the usual depth-averaged dispersion coefficient at the stationary stage. As one of the typical applications of horizontal dispersion, dispersion due to the pure drift current with an Ekman layer is examined theoretically using the present method. This examination reveals that the displacement of the centroid and the major axis of dispersion are twisted in the vertical direction more than the direction of the current vector forming the Ekman spiral; that the variance increases in proportion to the third power of the elapsed time; and that the dispersion coefficient at the stationary stage remains constant, independent of the depth normalized by an Ekman layer thickness. Such dependence of the dispersion coefficient in the steady current is shown to be different from that in the oscillatory current, which is inversely proportional to the depth normalized by a Stokes layer thickness. This is considered to be induced by the difference of the vertical profiles of the first order moment in both currents, that is, the shear region of the first order moment is restricted around the floor by the alternation of the current shear in the oscillatory current while it is diffused in the whole depth in the steady current.     

均匀土质边坡稳定性计算的一种新方法

根据土力学原理 ,推导出一种在不考虑渗流力的情况下 ,确定斜坡临界滑动面和计算斜坡稳定系数的新方法。介绍了该方法在若干土石方工程中的应用实例。     

长江口水域波浪数值计算

利用高阶非线性抛物型缓坡方程对长江口水域的波浪传播变形作了推算,依据测站的资料分析数值模式中的底摩阻因子和风能输入因子对波浪传播的影响,进而确定其参数。针对不同导堤结构型式,分析了潜堤的波浪传递系数,最后对长江口二期整治工程完成后水域的波浪场作了推算。     

地下水弥散系数的测定

以大红染料为示踪剂,采用单井脉冲注入示踪剂的方法测定了主井和观测井中示踪剂的浓度变化,并用解析公式法计算了西小洞垃圾场地下水的纵向弥散系数。     

青黄公路交通调查及交通量预测

通过对1998年2月青黄公路的交通调查,分析了青黄公路的交通现状,根据青岛市的国民经济增长速度、交通运输发展及城市出入口资料,利用弹性系数法预测了2000年和2010年青黄公路的城市交通量。