Uncertainty representation of ocean fronts based on fuzzy-rough set theory

Analysis of ocean fronts' uncertainties indicates that they result from indiseemibility of their spatial position and fuzzi-ness of their intensity. In view of this, a flow hierarchy for uncertainty representation of ocean fronts is proposed on the basis of fuzzy-rough set theory. Firstly, raster scanning and blurring are carried out on an ocean front, and the upper and lower approximate sets, the indiscernible relation in fuzzy-rough theories and related operators in fuzzy set theories are adopted to represent its uncer-tainties, then they are classified into three sets: with members one hundred pereent belonging to the ocean front, belonging to the ocean front's edge and definitely not belonging to the ocean front. Finally, the approximate precision and roughness degree are util-ized to evaluate the ocean front's degree of uncertainties and the precision of the representation. It has been proven that the method is not only capable of representing ocean fronts' uncertainties, but also provides a new theory and method for uncertainty representation of other oceanic phenomena.     

探空资料审核中特性层气压近似值的简易确定方法

这里介绍自治区气象局探空审核中,在不使用气压鉴定曲线的情况下求取气压近似值的简易方法,供探空资料预审人员参考.     

The Offset-Domain Prestack Depth Migration with Optimal Separable Approximation

The offset-domain prestack depth migration with optimal separable approximation, based on the double square root equation, is used to image complex media with large and rapid velocity variations. The method downward continues the source and the receiver wavefields simultaneously. The mixed domain algorithm with forward Fourier and inverse Fourier transform is used to construct the double square root equation wavefield extrapolation operator. This operator separates variables in the wave number domain and variables in the space domain. The phase operation is implemented in the wave number domain, whereas the time delay for lateral velocity variation is corrected in the space domain. The migration algorithm is efficient since the seismic data are not computed shot by shot. The data set test of the Marmousi model indicates that the offset-domain migration provides a satisfied seismic migration section on which complex geologic structures are imaged in media with large and rapid lateral velocity variations.     

THE EQUIVALENT SLOPE - A NEW METHOD FOR CALCULATING SOIL LOSS FROM IRREGULAR SLOPES

he slopes in field conditions are always irregular, but the supposed uniform slopes are used in most erosion models. Some studies used several uniform slopes to approximate an irregular slope for estimating soil erosion. This approximation is both time-consuming and weak in physical insights. In this paper, the concept of equivalent slope is presented based on that runoff potential on uniform slope is equal to that of irregular slope, and the equivalent uniform slope is used to estimate soil erosion instead of the irregular slopes. The estimated results of slope-length factors for convex and concave slopes are consistent with those from the method of Foster and Wischmeier, The experiments in the southern part of the Loess Plateau in China confirmed the applicability of the present method. The method is simple and has, to some extent, clear physical meanings, and is applicable for estimating soil erosion from irregular slopes.     

镁橄榄石电场梯度张量的重新计算

为了用一个无参数模式获得镁橄榄石所有晶核的电场梯度，提出了一个以密度函数为基础的能带结构重新计算方法。用广义梯度近似值法得到的＾２５Ｍｇ的Ｖｚｚ与由实验值获得Ｖｚｚ相差最大为１％，＾１６Ｏ为２％。如果在换算中使用核四极矩动量值，则绝对值相差约为５％，不对称参数与实验值也相当一致。     

一种改进的序贯平差算法

分析了序贯平差的基本原理,提出了一种基于前一期参数平差值的序贯平差的改进算法,简化了计算并具有很强的实用性。     

An approximation to the P-wave reflection coefficient for amplitude variation with long-offset seismic data

近年来,长偏移距排列逐渐被大量应用到海上勘探。传统AVO分析都是小入射角,对于长偏移距数据来说有很大不足。为了探讨拓宽AVO分析的研究范围,本文推导了长偏移距时P波反射系数的一种近似公式,并讨论了其精确性。本文的结果和广泛应用的Shuey公式相类似,Shuey公式可以看作本文结果在小入射角情况的简化。