基于高光谱遥感技术的土地质量信息挖掘研究

土地资源的高效管理对土地资源与生态环境监测提出更高的要求,高光谱遥感图像精细的光谱线可提高土地动态监测的精度、广度和深度,在土地资源与土地质量监测中具有广阔的应用前景。本文基于高光谱遥感技术,详细探讨了土地质量指标,主要是土壤有机质土壤水分信息提取的技术流程和关键技术。通过地物光谱分析认为,有机质含量越高的土壤,其光谱发射率越低;重度沙化土地实验室光谱曲线光谱反射率最高,依次排序为中度沙化、轻度沙化和无退化土地;重度水蚀土地光谱反射率较高,但中度水蚀土地与轻度水蚀和无退化土地实验室光谱曲线无明显差异。在光谱分析基础上,利用多元统计分析技术建立了土壤光谱在677、1202、2074和1509nm四个波段的有机质反演模型和在1423、1524、1746nm三个波段的预测土壤含水量的回归模型;并将有机质反演模型应用于宜兴成像光谱遥感数据中,进行宜兴试验区土壤有机质参数成图。最后探讨了反演模型应用推广所存在的问题。     

电子出版系统直接制版版材及输出工艺的研究

文中详细阐述了印前系统直接制版版材的制作原理及其输出工艺.通过选择经过采用特殊染料增感的卤化银乳剂作为银盐扩散型直接制版版材的感光物质,使之对630～680 nm的激光极为敏感;控制合成过程中化学反应条件,获得致密、具有一定的厚度和耐磨性能的核层;经涂布制成银盐扩散型直接制版版材,并配制出与之相适应的亲水、感脂液.实验证明,该版材适合CTP系统输出,经显影稳定后具有良好的印刷适性,可作为少份数印品的印刷版材.     

Semi‐active control of sliding isolated bridges using MR dampers: an experimental and numerical study

Sliding base‐isolation systems used in bridges reduce pier drifts, but at the expense of increased bearing displacements under near‐source pulse‐type earthquakes. It is common practice to incorporate supplemental passive non‐linear dampers into the isolation system to counter increased bearing displacements. Non‐linear passive dampers can certainly reduce bearing displacements, but only with increased isolation level forces and pier drifts. The semi‐active controllable non‐linear dampers, which can vary damping in real time, can reduce bearing displacements without further increase in forces and pier drifts; and hence deserve investigation. In this study performance of such a ‘smart’ sliding isolation system, used in a 1:20 scaled bridge model, employing semi‐active controllable magneto‐rheological (MR) dampers is investigated, analytically and experimentally, under several near‐fault earthquakes. A non‐linear analytical model, which incorporates the non‐linearities of sliding bearings and the MR damper, is developed. A Lyapunov control algorithm for control of the MR damper is developed and implemented in shake table tests. Analytical and shake table test results are compared. It is shown that the smart MR damper reduces bearing displacements further than the passive low‐ and high‐damping cases, while maintaining isolation level forces less than the passive high‐damping case. Copyright © 2005 John Wiley & Sons, Ltd.     

近场地震学中3个术语译名的商榷

asperity，barrier和fling step是近场地震学中3个重要的术语。但到目前为止，这3个术语还没有贴切、统一的中文译名。为了便于学术交流和读者对近场地震学的学习和理解，有必要规范统一它们的中文译名。本文基于3个术语产生的物理背景及其意义，建议这3个术语的中文译名分别为：asperity——高强体，barrier——止裂体，fling step——滑冲。     

快速成像：磁共振成像技术的进展

本文复习了大部分快速成像磁共振扫描技术，包括：半傅里叶技术，矩形视野，多层激励，快速自旋回波，快速梯度回波和回波平面技术。磁共振快速成像技术的使用可减少检查时间和运动伪影，提高病人检查耐受性以及获取动态影像等。使磁共振扫描有一更广的临床适应症。     

近场源二极激电法的找矿效果

赤峰兴隆山以铜为主的多金属矿区,属草原覆盖的隐伏矿床。经采用近场源二极激电法面积工作,获得了理想的激电异常11处,经钻探工程验证,取得了明显的找矿效果。本文主要介绍了近场源二极激电法在该区的找矿效果及资料解释中几种组合方法和辅助参数的综合利用。     

磁共振扫描对鼻咽癌放疗后局部复发与纤维化的鉴别诊断

本文对３２例鼻咽癌病人进行了Ｇｄ－ＤＴｈＡ增强前后磁共振成像（ＭＲＩ）检查。放疗后局部肿瘤复发（ＲＮＰＣ），纤维化（ＲＦ）的病例。结果表明；Ｇｄ－ＤＴＰＡＭＲ增强扫描下加权像能够提高病块与周围结构的区别。副鼻窦及鼻咽部粘膜看明显的强化作用。ＮＰＣ及ＲＮＰＣ皆为轻度到中等度均匀或四块状强化，ＲＦ组一般无强化，但有５例３８．５％呈轻度索条状强化，且多发生于放疗后间隔时间小于１年内者，ＲＮＰＣ与ＲＦ两组的强化率平均值有显著差别（Ｐ＜０．０５），虽其Ｘ±ＳＤ有部分重叠，但如能结合病灶强化程度和强化形式，对ＲＮＰＣ与ＲＦ的鉴别可提供重要信息．     

A new approach to pre-stack seismic processing

Pre-stack processing of seismic reflection data is significantly simplified if the data organization is the same as that in which the data were acquired in the field; that is, in time slices through common-source gathers. For an impulsive source, the entire processing stream reduces to two elements: velocity analysis and reverse-time pre-stack migration. Many of the steps that are applied as independent operations in standard processing (including demultiplexing, sorting into common-midpoint gathers, elevation corrections, near-surface velocity static corrections, first break muting, ground roll removal, and both normal and dip move-out corrections) either are eliminated, or are applied implicitly during migration. This approach is ideally suited to parallel processing, and can be implemented in machines with small processor memories.     

一种倾角时差校正和叠前成象方法

本文从测量射线参数出发进行反向射线追踪,导出倾角时差校正（DMO）的公式。经过DMO后,可以从一组等炮检距剖面得出共分角线点道集。用于对这些道集进行叠加的速度值与界面倾角无关。对经过DMO的资料的等时切片进行叠前成象（PSI）,就可以把分布在圆上的绕射能量沿圆弧加起来,并放在圆弧上对应于最大炮检距的位置。经过这两种处理,再应用标准的速度分析和叠加方法,就可得出偏移后的剖面。这两种处理均与速度无关。最后用物理模型试验说明了DMO和PSI的效果是好的。