显微CT的研究及应用的初步评述

近五年来在国内外显微CT的研究和应用，得到了很大的发展；微观病理显微诊断的空间分辨为微米数量级。目前医学CT影像的空间分辨率已达到0.35mm，已能满足宏观病理学诊断的要求。如何医学CT的空间分辨率再提高到微米水平，即可清晰显示细胞和组织的微细结构，从而满足现代医学临床病理诊断金标准的要求。目前工业CT（ICT）的空间分辨率已达到5－20微米，从而为提高医学CT的空间分辨率提供技术依据。本文引述用工业微焦点CT机首次对小动物组织进行显微成像的结果：提出应用微焦点X线源，以及采用钨酸镉集成电路CCD检测技术，进一步缩小检测元器件探头的尺寸和增加检测器探头的数目，可以提高医学CT的空间分辨率；应用电子束快速扫描技术，可以提高医学CT的时间分辨率，达到动态的水平；应用双能X线束扫描技术，可以进一步提高密度分辨率，如果未来医学CT的空间分辨率达到微米级（显微CT），时间分辨率达到毫秒级（动态CT），密度分辨率能观察到神经细胞有兴奋时，胞内钙离子浓度的瞬态上升1000倍，即成为显微动态和功能CT，就可以观测人脑神经元在不同功能状态下的动态兴奋和时空编码过程，对进一步研究人脑的记忆和思维认知过程有重要意义。     

二维矢量地震波场的叠前逆时深度偏移

从矢量波动理论出发，导出了二维弹性波逆时传播的高阶差分格式，实现了弹性波在数值空间中的逆时延拓，采用逆时格式差分求解程函方程，得到网格空间中各点的直达波旅行时，以此作为弹性波逆时偏移的成像条件。实现了二维多波多波多分量资料的叠前逆时深度偏移，数值试验得到了满意结果。     

渤海海峡潮流底应力与沉积物分布的关系

用数值模型方法计算了渤海海峡区潮流引起的最大和平均底应力,以及相应的活动层厚度的空间分布,并根据沉积物参数计算了沉积物临界起动切应力。计算结果的分析表明 :(1)最大潮流底应力和沉积物临界起动切应力的关系与底质分布之间存在着明显的对应,最大潮流底应力大于临界起动切应力的地方,分布着粗颗粒沉积物,若前者小于后者,对应的是细颗粒沉积物,若两者近于相等,则对应着较细颗粒的沉积物;(2 )在山东半岛北部近岸和渤海海峡的东北角,最大潮流底应力小于或接近于临界起动切应力的量值,而对应的沉积物是粉砂和砂,这一例外可能是由于残留沉积的出露,这一假说需要根据全新世海面上升历史、古水动力环境模拟、渤海海峡沉积环境演化等方面的研究来验证;(3)活动层厚度的分布规律与海底沉积物的分布存在着相关性 :即活动层厚度越大,对应的海底沉积物越粗;活动层厚度越小,对应的沉积物越细。     

Advanced techniques in site characterization and mining hazard detection for the underground coal industry

Today's highly productive coal mining systems represent large capital investments. Careful geotechnical planning and design are essential to protect these systems and to help ensure their overall success. Too often, however, the ability of the mine operator to adequately characterize the geotechnical environment and keep up with changing geologic conditions lags the advance rate of the mining equipment. Seismic tomographic imaging, based on the same principles as medical Computer-Aided-Tomography (CAT) Scans, offers the ability to identify changing geologic conditions, loading patterns, and the location of nearby abandoned mine workings. Although seismic tomography has been used for many years in the oil industry, until recently its practicality in the mining industry has been limited because the processes involved interfered with mining productivity and were labor-intensive in terms of data collection and interpretation. New advancements in signal processing have greatly enhanced the speed, resolution, and range of applications of tomographic imaging in underground coal mine settings.Many tomography applications in the mining industry use seismic velocity and/or attenuation tomography within a volume enclosed by the seismic source and receiver array. Although results obtained using this geometry work well in many situations, recent developments in reflection tomography show promise in eliminating the requirement that the target volume be surrounded by sources/receivers. For example, in-seam seismic reflection tomography may now be used to image structures and/or old workings from one general location in the mine (e.g., face areas of mains and panel developments) well ahead of planned developments—largely eliminating the need to probe-hole drill on regular intervals. These new developments have greatly expanded the ability of the mine operator to cost-effectively characterize previously inaccessible areas of the property.This paper gives an overview of the theories and processes involved in seismic tomography applicable to coal mine settings. Recent examples are presented of tomographic imaging applied to a variety of coal mine ground control problems and old works detection in the United States and Europe. The applicability of both seismic refraction and seismic reflection tomography is discussed.     

成像光谱仪分光技术概览

论文介绍了多种成像光谱仪的分光技术。棱镜或光栅色散型成像光谱仪技术成熟，应用广泛；在发散光束中使用光栅的方法，克服了准直光束用法中的一些缺陷；傅里叶变换光谱仪是遥感探测可见和红外弱辐射的有力工具；光楔成橡光谱仪结构简单，随着渐变滤光片工艺技术的成熟，已走向实用化；采用可调谐滤光片的成像光谱仪由于滤光片水平的限制，投入应用还有待时日；采用二元光学元件的成像光谱仪结构紧凑，体积小，扫描速度快，已研制出地面实用型产品；层析成像光谱仪原理新，目前还处在实验阶段；三维成像光谱仪可以同时获取二维影像和一维光谱信息，可实现对迅变目标的观测。     

Crustal structure of the ancestral northwestern California forearc region from seismic reflection imaging: implications for convergent margin tectonics

Analysis of a suite of 2-D seismic reflection profiles reveals that the northwestern Sacramento Valley and eastern Coast Range foothills, northern California, are underlain by a system of blind, west-dipping thrust faults. Homoclinally east-dipping and folded Mesozoic marine forearc strata exposed along the western valley margin define the forelimbs of northeast-vergent fault-propagation folds developed in the hanging walls of the thrusts. Exhumed coherent blueschists of the accretionary complex and attenuated remnants of the ophiolitic forearc basement presently exposed in the eastern Coast Ranges are in the hanging wall of the blind thrust system, and have been displaced from their roots in the footwall. Deep, east-dipping magnetic reflectors in the footwall of the thrust system may be fragments of sheared, serpentinized and attenuated ophiolitic basement. Restoration of slip on the thrusts suggests that the Coast Range fault, which is the exposed structural contact between the coherent blueschists and attenuated ophiolite, originally dipped east and is associated with the east-dipping magnetic reflectors in the footwall. This interpretation of the reflection data is consistent with previous inferences about the deep structure in this region, and supports a two-stage model for blueschist exposure in the eastern Coast Ranges: (1) blueschist exhumation relative to the forearc basin by attenuation of the ophiolitic basement along the east-dipping Coast Range fault system in late Cretaceous; (2) blueschists, attenuated ophiolite, and forearc strata all were subsequently uplifted and folded in the hanging wall of the blind thrust system beginning in latest Cretaceous–early Tertiary. The blind thrust system probably rooted in, and was antithetic to, the east-dipping subduction zone beneath the forearc region. Active transpressional plate motion in western California is locally accommodated, in part, by reactivation of blind thrust faults that originally developed during the convergent regime.     

断层附近地面地震动空间分布

运用震源位错模型, 分析矩形垂直断层及倾斜断层走向滑动和倾向滑动的近场地震动场，以地表地震动的傅立叶振幅谱比为参量考察断层附近地震动空间分布的特点. 结果表明, 断层附近的地震动强度主要受近旁子断层的控制，高强度的地震动分布在紧靠断层两侧有限的带状区域内，长周期分量受断层破裂传播方向性的影响. 走向滑动的方向性影响主要表现在垂直于断层走向的分量，倾向滑动则表现在平行于断层走向的分量，且深震在地面上引起的地震动强度分布比浅震要平缓，影响范围宽. 倾斜断层产生的地震动有明显的上盘效应，空间分布不对称，与观测结果相符. 最后给出了断层附近近场地震动强度分布拟合函数的表达式，并与美国的1997统一建筑规范规定的近场因子作了比较.