海洋地球物理研究与海底探测声学技术的发展

海洋地球物理以物理学的思维与方法研究占地球三分之二面积的海洋系统.20世纪地球科学迅猛发展,它的重大进展是海底扩张说与板块构造说的出现和海底大洋的发现,以及前者所引发的地球科学思想革命,从固定论向活动论的思维转变.海底研究对于20世纪地球科学发展的贡献极为巨大,而海洋地球物理是推动海底科学研究的重要原动力.海洋地球物理在20世纪地球科学的发展中有过辉煌的成就,占有十分重要的地位;在新的21世纪里,海洋地球物理研究仍然保持着前沿科学的地位,继续推动着地球科学的进展.目前的海底探测主要还是依赖于声学探测技术.水下声学定位技术是实现水下探测系统精确定位和海底高精度探测的基础.传统性的海洋地震探测技术是研究海底构造与海洋岩石圈深部结构和寻找海底矿产的主力技术,它近年来无论在海上采集技术还是数据处理技术方面都发展得很快.多波束测深、侧扫声呐测图和海底地层剖面测量等则是近数十年快速发展起来探测海底浅部结构信息的技术.这些技术已经在当代海底科学研究、海底资源勘查、海洋工程和海洋开发,以及海洋军事活动等方面发挥出极其重要的作用.     

2.5维电阻率成像的新方法

以作者提出的正演方法为基础,给出一种新的2.5维电阻率成像方法,节省了计算时间,使成像迭代过程很稳定,可以对实际上广泛存在的大电性对比度的介质成像,从而提高了电阻率层析成像技术的实用性.     

Localisation and phase transition of acoustic waves in a soft medium containing air bubbles

We study via numerical experiments the localisation property of an acoustic wave in a viscoelastic soft medium containing randomly-distributed air bubbles. The behaviours of the oscillation phases of bubbles are particularly investigated in various cases for distinguishing efficiently the acoustic localisation from the effects of acoustic absorption caused by the viscosity of medium. The numerical results reveal the phenomenon of `phase transition' characterized by an unusual collective oscillation of bubbles, which is an effective criterion to unambiguously identify the acoustic localisation in the presence of viscosity. Within the localisation region, the phenomenon of phase transition persists, and a remarkable decrease in the fluctuation of the oscillation phases of bubbles is observed. The localisation phenomenon will be impaired by the enhancement of the viscosity factors, and the extent to which the acoustic wave is localised may be determined by appropriately analyzing the values of the oscillation phases or the amount of reduction of the phase fluctuation. The results are particularly significant for the practical experiments in an attempt to observe the acoustic localisation in such a medium, which is in general subjected to the interference of the great ambiguity resulting from the effect of acoustic absorption.     

Sub-basalt seismic imaging using optical-to-acoustic model building and wave equation datuming processing

The presence of highly heterogeneous basalt layers has a detrimental effect on seismic imaging of underlying structures. Due to the prevalence of basalt, the challenge of imaging below basalts impinges on a broad spectrum of geological problems, from hydrocarbon exploration to volcano seismology. Both internal basalt characteristics and rough interfaces can degrade the sub-basalt image quality. In this paper we investigate the effects of both internal and surface heterogeneity on the wavefield. Using highly heterogeneous models of basalts derived from optical imagery and borehole sonic logs, combined with wave simulations to generate synthetic data, we explore the causes of poor sub-basalt imagery. We establish the significant role that surface roughness plays in the imagery problem and demonstrate, through a novel application of wave equation datuming, how to suppress its effect. The methodology demonstrated herein may be applicable in any environment where heterogeneous surface structures/interfaces severely degrade seismic image quality.     

光学航天传感器几何建模与DEM生成新进展

高分辨率光学卫星成像系统正越来越多地应用于遥感和摄影测量领域。根据新型的高分辨率卫星影像系统主要特点及高分辨率卫星测图的关键技术的发展趋势,以第21届国际摄影测量与遥感大会“光学航天传感器几何建模与DEM生成”专题中的51篇文章为参考,总结了目前典型的光学卫星影像（主要是IRS—P5和ALOS／PRISM）的几何建模方法,影像匹配与DEM提取方法以及光学航天传感器在其他方面的应用。     

高分辨率卫星影像车辆检测的抗体网络

将车辆检测的过程视为一种“抗体”检测“危险抗原”的过程, 其中车辆是“危险抗原”, 车辆检测模板是“抗体”。利用一些车辆图像作为训练样本, 建立一种抗体网络学习并获取一组优化的“抗体”。这些“抗体”经过与待测影像的匹配, 实现对道路车辆目标的有效提取。采用0.6m分辨率的QuickBird全色数据进行实验, 实验结果验证了该方法的有效性和可行性。     

内外业一体化调查方法在土地调杏中的应用

以广东省龙门县土地利用更新调查为例,介绍了内外业一体化调查方法在土地调查中的应用,并论述了内外业一体化调查方法在生产中需要注意的事项。     

多功能水声设备模拟信号源的设计与功能实现

针对目前水声测量装备的日常使用训练、维护保养和性能检测的需要,设计了一种对水声测量设备进行常态维修检测和在非航行状态下仿真模拟深水操作训练的专用信号源设备,论述了多功能水声设备模拟信号源的设计思路,硬件设计原理及各功能的实现过程。     

海洋水声调查及信号处理方法的研究

水声环境包括海洋中影响声信号传播的各种参数,传统上,这些参数的测量都是由从事水声及其设备研究的专业人员进行,而且需要许多实验室测量仪器,所以,一直被称为水声实验。就如何将海洋水声参数的测量工程化,实现多航次、大面积的高效率水声调查,对信号获取方法、信号分析与处理方法进行了探索性研究,并在专门的数据处理软件研制中,对提出的联合时频分析法进行了验证。     

An improved procedure for detection and enumeration of walrus signatures in airborne thermal imagery

In recent years, application of remote sensing to marine mammal surveys has been a promising area of investigation for wildlife managers and researchers. In April 2006, the United States and Russia conducted an aerial survey of Pacific walrus (Odobenus rosmarus divergens) using thermal infrared sensors to detect groups of animals resting on pack ice in the Bering Sea. The goal of this survey was to estimate the size of the Pacific walrus population. An initial analysis of the U.S. data using previously-established methods resulted in lower detectability of walrus groups in the imagery and higher variability in calibration models than was expected based on pilot studies. This paper describes an improved procedure for detection and enumeration of walrus groups in airborne thermal imagery.Thermal images were first subdivided into smaller 200 × 200 pixel “tiles.” We calculated three statistics to represent characteristics of walrus signatures from the temperature histogram for each tile. Tiles that exhibited one or more of these characteristics were examined further to determine if walrus signatures were present. We used cluster analysis on tiles that contained walrus signatures to determine which pixels belonged to each group. We then calculated a thermal index value for each walrus group in the imagery and used generalized linear models to estimate detection functions (the probability of a group having a positive index value) and calibration functions (the size of a group as a function of its index value) based on counts from matched digital aerial photographs.The new method described here improved our ability to detect walrus groups at both 2 m and 4 m spatial resolution. In addition, the resulting calibration models have lower variance than the original method. We anticipate that the use of this new procedure will greatly improve the quality of the population estimate derived from these data. This procedure may also have broader applicability to thermal infrared surveys of other wildlife species.