地震波反射系数偏导矩阵的精确解及对近似计算的精度分析

目前叠前反演方法大多是基于Zoeppritz方程近似式实现的,它仅适应于弱反射介质界面、中小角度(或小偏移距)的地震数据反演,不能满足勘探开发的地质需求.本文建立了基于zoeppritz方程精确求解反射系数的梯度矩阵,分析了矩阵特点和精度,为研究利用反射系数梯度精确解反演地震参数奠定了基础.     

广东百顺地区伽马场参数特征及其与铀矿化关系

运用伽马场参数特征与铀矿化关系,结合判别分析系数和伽马频率曲线形态,对百顺地区的牛澜、烟筒岭、百顺硅化断裂带的异常点、带的找矿远景区段作了评价,简述伽马频率曲线形态与矿体空间位置的关系。     

Application of particle filter combined with extended Kalman filter in model identification of an autonomous underwater vehicle based on experimental data

This study proposes a method for identification of the nonlinear dynamic model of an AUV while some states are unmeasured; hence, it concentrates on a nonlinear “state and parameter estimation” issue. In this method, a local linearization is used for solving the nonlinear dynamics based on the extended Kalman filter (EKF), and a particle filter (PF) is used to minimize errors and variances of the nonlinear system. In other words, the PF is combined with the EKF in the form of the extended Kalman particle filter (EKPF). The EKPF method is independent of the initial values and satisfies the limits of the parameters and also the assumption that the hydrodynamic coefficients are constant. Hence, it is shown when the ranges or signs of some parameters are known, the EKPF is a more accurate estimator than the EKF. Moreover, a new simulation is done using the model estimated by the EKPF and the results are compared and validated with the measured data of a new experimental test. It is shown that the obtained model can predict the trajectory path with the total normalized root-mean-square error (NRMSE) of 14% and the surge mean speed with the NRMSE of 5%; and it describes the 6DOF motion of the AUV more accurate than the EKF model.     

Principle of Cross Coupling Between Vertical Heat Turbulent Transport and Vertical Velocity and Determination of Cross Coupling Coefficient

It has been proved that there exists a cross coupling between vertical heat turbulent transport and vertical velocity by using linear thermodynamics. This result asserts that the vertical component of heat turbulent transport flux is composed of both the transport of the vertical potential temperature gradient and the coupling transport of the vertical velocity. In this paper, the coupling effect of vertical velocity on vertical heat turbulent transportation is validated by using observed data from the atmospheric boundary layer to determine cross coupling coefficients, and a series of significant properties of turbulent transportation are opened out. These properties indicate that the cross coupling coefficient is a logarithm function of the dimensionless vertical velocity and dimensionless height, and is not only related to the friction velocity u*, but also to the coupling roughness height zW0 and the coupling temperature TW0 of the vertical velocity. In addition, the function relations suggest that only when the vertical velocity magnitude conforms to the limitation |W/u*|≠1, and is above the level zW0, then the vertical velocity leads to the cross coupling effect on the vertical heat turbulent transport flux. The cross coupling theory and experimental results provide a challenge to the traditional turbulent K closure theory and the Monin-Obukhov similarity theory.     

Numerical investigation of the hydrodynamic interaction between two underwater bodies in relative motion

The hydrodynamic interaction between an Autonomous Underwater Vehicle (AUV) manoeuvring in close proximity to a larger underwater vehicle can cause rapid changes in the motion of the AUV. This interaction can lead to mission failure and possible vehicle collision. Being self-piloted and comparatively small, an AUV is more susceptible to these interaction effects than the larger body. In an aim to predict the manoeuvring performance of an AUV under the effects of the interaction, the Australian Maritime College (AMC) has conducted a series of computer simulations and captive model experiments. A numerical model was developed to simulate pure sway motion of an AUV at different lateral and longitudinal positions relative to a larger underwater vehicle using Computational Fluid Dynamics (CFDs). The variables investigated include the surge force, sway force and the yaw moment coefficients acting on the AUV due to interaction effects, which were in turn validated against experimental results. A simplified method is presented to obtain the hydrodynamic coefficients of an AUV when operating close to a larger underwater body by transforming the single body hydrodynamic coefficients of the AUV using the steady-state interaction forces. This method is considerably less time consuming than traditional methods. Furthermore, the inverse of this method (i.e. to obtain the steady state interaction force) is also presented to obtain the steady-state interaction force at multiple lateral separations efficiently. Both the CFD model and the simplified methods have been validated against the experimental data and are capable of providing adequate interaction predictions. Such methods are critical for accurate prediction of vehicle performance under varying conditions present in real life.     

水系划分的剖面相似系数聚类法

提出一种基于温度剖面相似系数的水系划分方法。基本思想是:将各温度剖面视为独立样本,各深度数据为样本变量,先基于划分区域水文特征选取合理数量的水系中心剖面,再利用各样本与各中心剖面相似系数大小进行聚类,得到各水系划分数据集合;利用几何平均求得各水系集合新的中心剖面,重复剖面相似系数聚类过程,直至中心剖面不再变化为止。最后利用国家海洋信息中心发布的中国近海CTD温、盐产品对该方法进行试验,并对聚类得到的各类温度剖面展开讨论。结果较好的反应出各区域温度剖面特征,综合体现出东海各区域温度大小、海流、水团和水深特性。     

T63月动力延伸预报产品的检验

采用NCEP／NCAR再分析资料和T63谱模式月动力延伸预报产品资料,对200、500hPa高度场及200hPa、700hPaU、V风场进行相关系数、距平、距平同号率、距平相关系数的分析,得出如下结论：月动力延伸预报产品对极涡、南亚高压、副热带高压预报能力较强,夏季副热带系统预报偏强,西风带系统预报偏弱;冬季西风带系统预报偏强,副热带系统预报偏弱。西风带和副热带系统的距平误差基本反映出影响我国年季气候变化主导系统的进退及预报误差。     

Influence of a cyclic and dynamic loading history on dynamic properties of dry sand, part II: cyclic axial preloading

Initial fabric of a soil induced by its cyclic strain history is an important parameter among others like void ratio, state of stress and amplitude concerning the further accumulation of deformations under cyclic loading. It is of high importance to determine methods in order to estimate the initial fabric of the grain skeleton or the cyclic loading history of the soil. An attempt is made in this paper to correlate small strain stiffness of non-cohesive soil with its cyclic loading history. For this purpose several cyclic triaxial tests with specimens subjected to cyclic axial loading were performed and changes of small strain soil properties due to this cyclic loading were studied. All these tests showed only moderate changes of small strain stiffnesses independently of the different boundary conditions. Thus, a correlation between fabric or strain history and small strain stiffnesses seems not to be possible.     

基于高斯曲率模态相关系数的弯梁桥支座损伤研究

对于弯梁桥支座病害中普遍存在的刚度不足,甚至脱空现象,提出利用平面多阶模态及高斯曲率模态相关系数来识别弯梁桥支座的损伤情况。在理论推导的基础上,以某小半径弯梁桥为研究对象,建立了相关分析模型。分析结果表明:无论单支座损伤,还是多支座损伤,相应支座处的高斯曲率模态相关系数与其它支座位置处的差异明显,可实现支座损伤的准确定位;且支座损伤越严重,相关系数下降越多;支点预偏心和抗扭支承等因素对损伤定位没有影响,相邻控制点处相关系数有所降低,但不会影响支座损伤识别的有效性。     

THE CCA BETWEEN 500 hPa GEOPOTENTIAL HEIGHT FIELDS OVER NORTHERN HEMISPHERE AND RAINFALL OF CHINA IN MAY

~~THE CCA BETWEEN 500 hPa GEOPOTENTIAL HEIGHT FIELDS OVER NORTHERN HEMISPHERE AND RAINFALL OF CHINA IN MAY@严华生$Department of Earth Sciences, Yunnan University, Kunming 650091 China@陈艳$Yunnan Meteorological Science Institute, Kunming 650034 China@郭世昌$Department of Earth Sciences, Yunnan University, Kunming 650091 China@王会军$Institute of Atmospheric Physics, Academy of Sciences, Beijing 100091 China~~ Project 973 (G1998040905)…