Conditional curvilinear stochastic simulation using pixel-based algorithms

In geology, structures displaying differing local directions of continuity are widespread, a typical example being a flusial depositional system. Conventional pixel-based geostatistical algorithms, may fail to reproduce such curvilinear structures. Conversely, object-based algorithms can reproduce curvilinear shapes but are difficult to condition to dense local data. Local depositional directions as obtained from dipmeter data. 3D seismic data, and geological interpretation represent critical information. An improved pixel-based geostatistical algorithm is proposed to account for such directional information. Case studies demonstrate the potential and limitations of the algorithm.     

部分预制型钢混凝土梁抗震性能试验研究

为探究部分预制型钢混凝土梁的抗震性能,进行了7个部分预制型钢混凝土梁试件的拟静力试验,研究了试件的裂缝开展过程、破坏形态、承载能力、延性、耗能能力和刚度退化情况,探究预制截面模式、剪跨比和后浇混凝土强度等对其抗震能力的影响。结果表明:地震作用下,该7个试件力学性能较好,剪跨比是影响试件抗震性能的首要要素,剪跨比大的试件耗能能力强,型钢约束部分混凝土可以提高试件的耗能能力,截面模式和后浇混凝土强度对抗震性能影响不大。     

Change of Support for Estimating Local Block Grade Distributions

An important aspect in mineral resource evaluation is the reduction of variance when post-processing the grade distributions defined on the support (volume) of the available data into distributions defined on the support of the proposed selective mining units. Although the volume-variance relationship is well understood for the estimation of global grade distributions, it is still an unsolved issue for local estimation studies based on non-parametric geostatistical methods, such as indicator kriging, for which the support correction is not inherent to the method. To clarify this relationship, the local change of support problem is examined in the scope of two parametric models (multi-Gaussian and discrete Gaussian models). It is shown that the variance reduction factor between point and block-support local distributions depends on the block being considered and is less than the global variance reduction factor. As a consequence, post-processing the local point-support grade distributions on the basis of the latter systematically understates the importance of the change of support at the local scale and makes selective mining appear more economically attractive than it really is. In the light of these results, a methodology is proposed to post-process the local point-support distributions obtained via non-parametric (indicator) methods into block-support distributions. An application to simulated data indicates that this methodology provides an accurate estimation at the block support when dealing with diffusion-type random fields.     

Crustal laminations in deep seismic profiles in France and neighbouring areas

Summary. Remarkable crustal features appear on the ECORS profiles carried out in northern France and the Bay of Biscay as well as on the SWAT profiles shot in the western Channel and the Celtic Sea. The most striking one is the occurrence of flat laminations in the lower crust. Dipping events and laminations are also present in the upper and lower crust, especially in the SWAT profiles. They can readily be related to tectonic events, Variscan in age, some of them identified in the field. The flat laminations in the lower crust are at first interpreted as resulting from delamination, shearing, magmatism and metamorphism at the crust-mantle transition during the Variscan orogeny. This interpretation raises some difficulty concerning the space and time correlation of the laminations with the Variscan orogeny. They seem to have been emplaced after the Permian-Triassic infilling of the Plymouth Bay basin and before the early Cretaceous opening of the Bay of Biscay. An early to middle Jurassic age is suggested, a period when large cratonic basins were formed without noticeable extension. Heat flow increase and magmatism are proposed as a second hypothesis for the formation of the lower crust laminations. Choosing between orogenic and non-orogenic causes of these laminations will require further deep seismic profiles together with good velocity determination.     

基于高阶累积量的简正波声场匹配场定位效果分析

由于传统情况,匹配场处理器主要针对接收信号为高斯信号,而海洋环境中存在大量的有色噪声,因此设计基于高阶累积量的匹配场处理器具有一定价值。本文介绍了一种在海洋声层析环境下用高阶累积量来降低匹配场处理中高斯有色噪声的算法,对比研究了基于高阶累积量的简正波声场匹配场处理器、传统线性匹配场处理器、自适应匹配场处理器及二阶MUSIC算法匹配场处理器在相同声场环境条件下的匹配场定位效果。研究结果表明,在不考虑参数失配与计算量前提下,接收信号经过基于高阶累积量的简正波声场匹配场处理器后再进行匹配场定位,能有效降低旁瓣,且使用高阶累积量可显著消除海洋传播环境中高斯有色噪声和高斯白噪声对信号的干扰,其匹配效果优于另外三种匹配场处理器。     

Propagation of partially coherent beams carrying an edge dislocation through atmospheric turbulence along a slant path

This paper derives the explicit expressions for the average intensity, beam width and angular spread of Gaussian Schell-model (GSM) beams with edge dislocation propagating through atmospheric turbulence along a slant path. The propagation of GSM beams with edge dislocation through horizontal atmospheric turbulence can be treated as a special case through a slant one. The propagation properties of GSM beams with edge dislocation through slant atmospheric turbulence are studied, where the influence of edge dislocation parameters including the slope p and off-axis distance d on the spreading of GSM beams with edge dislocation in atmospheric turbulence is stressed. It shows that the spreading of the intensity profile of GSM beams with edge dislocation along a slant path is smaller than that along a horizontal path in the long-distance atmospheric propagation. The larger the slope vert pvert and the smaller the off-axis distance vert dvert are, the less the beam-width spreading and angular spread of GSM beams with edge dislocation are affected by turbulence. The GSM beams with edge dislocation is less affected by turbulence than that of GSM beams without edge dislocation. The results are illustrated numerically and their validity is interpreted physically.     

南海内波研究前沿与热点

内波为发生在层结海洋内部的亚中尺度波动,是物理海洋学研究,特别是海洋混合及能量级串研究,不可或的缺环节。孤立内波的突发性巨大冲击能量可对水下航行和工程设施构成灾难性威胁,实现实时监测与预报海洋内波具有重大现实意义。南海是全球海洋中超强内波多发海区之一。长期现场观测表明,吕宋海峡以西海域内孤立波振幅高达150～200 m,且终年发生。因此,南海是目前海洋内孤立波观测与研究热点海域。本文以2015年至2021年间发表的论文为依据,评述南海内波研究新进展,认为7 a来研究成果取得质的提升。第一,实现了由卫星为主要手段2D观测到以卫星与潜标同步3D观测为主要手段的提升。由此催生出振幅240 m超强内孤立波、中尺度涡对内波的调制作用、重现周期23 h内孤立波、浅海内孤立波裂变现象、深海盆内波及动能级串等创新成果。第二,研究区开始呈现向中部深海盆扩展趋势。迄今为止,南海内波观测与研究集中在吕宋海峡以西和北部陆架,现已出现向中部深海盆扩展趋势。第三,海洋探测高新技术应用于南海内波观测与研究,取得了突破性成果。由卫星高度计沿轨海面高度场二维平面波分解技术得出的南海M2内潮辐射图,解决了多年争论不休的南...     

海流剖面仪信号处理系统中最小二乘改进算法的应用研究

ADCP技术是海洋测流领域的热门技术,而频谱估计方法的研究是该技术的核心。文章介绍一种最小二乘的改进算法(ELMS),利用该算法可以很好的提取出淹没在白噪声下的正弦频谱。和传统的快速傅立叶变换方法(FFT)相比,该算法极大的压缩了数据量的要求,而且在信噪比为0DB的时候,仍能够较准确的估计出信号的谱峰位置。实验结果辩明该算法具有良好的鲁棒性。     

基于高斯平滑滤波的罗兰C周期识别新方法

在有效估计天波延迟地波时间的基础上,提出了全新的基于高斯平滑滤波的罗兰C周期识别新方法。该方法完全摆脱了固定第三周期识别的思路,在有效防止信号出现周跳和确保接收机接收性能的精确性与稳定性的同时,提高了采样信号的信噪比,降低了信号电平的损失,增加了信息的利用率。     

Object detection and tracking method of AUV based on acoustic vision

This paper describes a new framework for object detection and tracking of AUV including underwater acoustic data interpolation, underwater acoustic images segmentation and underwater objects tracking. This framework is applied to the design of vision-based method for AUV based on the forward looking sonar sensor. First, the real-time data flow (underwater acoustic images) is pre-processed to form the whole underwater acoustic image, and the relevant position information of objects is extracted and determined. An improved method of double threshold segmentation is proposed to resolve the problem that the threshold cannot be adjusted adaptively in the traditional method. Second, a representation of region information is created in light of the Gaussian particle filter. The weighted integration strategy combining the area and invariant moment is proposed to perfect the weight of particles and to enhance the tracking robustness. Results obtained on the real acoustic vision platform of AUV during sea trials are displayed and discussed. They show that the proposed method can detect and track the moving objects underwater online, and it is effective and robust.