CT在脑血管病急性期定性诊断中的应用     

杨炳森  刁振华  林秀极  齐莲英  孙贻忠  班贵江 《CT理论与应用研究》1994,(1)

本文应用ＣＴ对４２例脑血管病急性期病人进行检查，结果表明：ＣＴ在脑血管病急性期定性诊断中具有首选价值．尤其对出血性脑血管病最为实用，对超早期缺血性脑血管病虽然不如ＭＲＩ敏感，但应用ＣＴ动感观察可以弥补这方面的不足，这对无设备的单位更为重要，ＤＳＡ对脑动脉瘤、脑动静脉畸型、脑血管狭窄的诊断较特异。  相似文献   

消除强震加速度记录数字化误差的方法和处理软件     

于海英谢礼立  公茂盛 《地震工程与工程振动》2005,25(5):1-5

本文详细地分析了用数字化仪和激光扫描仪对模拟加速度记录进行数字化时所产生的误差及消除这些误差的方法，并开发了相关处理软件。数字化误差由数字化设备的系统误差和读数员在操作过程中的随机误差迭加而成，随机数字化误差是具有各态历经性质的、其振幅按高斯规律分布的平稳随机过程。利用激光扫描仪做强震记录数字化，工作效率很高。本文给出了激光扫描仪分析处理软件和消除数字化噪声实例。  相似文献   

Carbon and strontium isotope variations and responses to sea-level fluctuations in the Ordovician of the Tarim Basin   总被引：2，自引：0，他引：2  

JIANG Maosheng  ZHU Jingquan  CHEN Daizhao  ZHANG Renhu  QIAO Guangsheng 《中国科学D辑(英文版)》2001,44(9):816-823

In the Ordovician, a carbonate platform system grading from the platformal interior eastwards to basin was developed in the Tazhong area of the Tarim Basin, and the study column is located in the place where the paleoslope occurred. The isotope compositions of the carbonates there are thus considered as having reflected those of simultaneous sea waters in view of its good connection with the open seas. The carbon and strontium isotope compositions of the Ordovician carbonates in the Tazhong area are analyzed, and their relationships to the sea-level fluctuations are discussed as well. Studies have revealed that the carbon isotope composition is related positively with the sea-level fluctuations, whereas an opposing situation occurs to the strontium isotope variation. Similar responses of carbon and strontium isotope compositions to the sea-level fluctuations are reported elsewhere in the world, suggesting that the Ordovician sea-level fluctuations of the Tarim Basin were of eustatic implication.  相似文献   

Long-distance correlation between tectonic-controlled, isolated carbonate platforms by cyclostratigraphy and sequence stratigraphy in the Devonian of South China   总被引：5，自引：1，他引：5  

Daizhao Chen  Maurice E. Tucker  Maosheng Jiang  & Jingquan Zhu 《Sedimentology》2001,48(1):57-78

During the early Middle Devonian in South China, an extensive carbonate platform was broken up through extension to create a complex pattern of platforms, and interplatform basins. In Givetian and Frasnian carbonate successions, five depositional facies, including peritidal, restricted shallow subtidal, semi‐restricted subtidal, intermediate subtidal and deep subtidal facies, and 18 lithofacies units are recognized from measured sections on three isolated platforms. These deposits are arranged into metre‐scale, upward‐shallowing peritidal and subtidal cycles. Nine third‐order sequences are identified from changes in cycle stacking patterns, vertical facies changes and the stratigraphic distribution of subaerial exposure indicators. These sequences mostly consist of a lower transgressive part and an upper regressive part. Transgressive packages are dominated by thicker‐than‐average subtidal cycles, and regressive packages by thinner‐than‐average peritidal cycles. Sequence boundaries are transitional zones composed of stacked, high‐frequency, thinner‐than‐average cycles with upward‐increasing intensity of subaerial exposure, rather than individual, laterally traceable surfaces. These sequences can be further grouped into catch‐up and keep‐up sequence sets from the long‐term (second‐order) changes in accommodation and vertical facies changes. Catch‐up sequences are characterized by relatively thick cycle packages with a high percentage of intermediate to shallow subtidal facies, and even deep subtidal facies locally within some individual sequences, recording long‐term accommodation gain. Keep‐up sequences are characterized by relatively thin cycle packages with a high percentage of peritidal facies within sequences, recording long‐term accommodation loss. Correlation of long‐term accommodation changes expressed by Fischer plots reveals that during the late Givetian to early Frasnian increased accommodation loss on platforms coincided with increased accommodation gain in interplatform basins. This suggests that movement on faults resulted in the relative uplift of platforms and subsidence of interplatform basins. In the early Frasnian, extensive siliceous deposits in most interplatform basins and megabreccias at basin margins correspond to exposure disconformities on platforms.  相似文献   

泥盆纪海相碳酸盐岩碳同位素组成及演变   总被引：4，自引：0，他引：4       下载免费PDF全文

陈代钊  陈其英  江茂生 《沉积与特提斯地质》1995,(5):22-28

根据对六景泥盆系碳酸盐岩碳同位素组成的系统分析表明：从落霍柯夫期到布拉格期海洋中的δ~１３Ｃ是逐渐变重，埃姆斯期明显变轻．艾菲尔期又开始变重，特别是基维特期有较明显的正向偏移，并继续向上变重，至弗拉斯期与法门期之交达到最大，尔后逐渐变轻，反映了泥盆纪海洋碳同位素组成的演变趋势．这和泥盆纪（二级）海平面的变化趋势是基本一致的，反映海洋碳同位素组成与海平面变化及相关的气候和海洋、大气中ＣＯ_２含量的成因联系。弗拉斯阶－法门阶界线附近δ~１３Ｃ的变化型式表明其间发生的生物绝灭事件是海平面升降和缺氧环境的周期性扩展等因素的累积效应的结果．  相似文献   

干涉雷达在DEM测量中的精度影响及处理方法   总被引：1，自引：0，他引：1  

郭泾平  彭军  向茂生 《测绘学院学报》1998,(3)

干涉合成孔径雷达 (INSAR)为数字高程模型 (DEM)测量提供了一种新的手段。它具有同时获取三维信息、测量范围广、空间和高程分辨率高等优点。文中首先扼要介绍了干涉雷达的原理 ,然后重点讨论几个影响测量精度的因素及其处理方法 ,如相关、运动补偿、配准、相位展开等。  相似文献   

湘黔地区中奥陶世海平面上升的沉积响应   总被引：2，自引：0，他引：2       下载免费PDF全文

江茂生 《地质科学》1998,33(1):93-101

中奥陶世克拉道克阶(Caradocian)在全球范围内为海侵期,体现在全球范围广泛的黑色页岩沉积及笔石动物的大规模繁盛,湘黔地区这一时期地层发育完全,从碳酸盐台地-斜坡-外陆架盆地均有不同程度的响应。在台地区表现为碳酸盐台地的淹没,斜坡区表现为碳酸盐重力流及黑色页岩、粉砂岩沉积,形成碳酸盐与陆源碎屑的混合沉积,而在外陆架盆地区表现为黑色岩系大规模发育及笔石的大量繁盛。  相似文献   

二华平原区环境地质问题与地下水资源开发   总被引：2，自引：1，他引：1  

张茂省  杨培养  徐金龙 《陕西地质》1998,(1)

本文从二华平原区地下水动态特征以及与地下水开采有关的环境地质问题入手,研究人类工程活动与地质环境之间的相互作用和相互制约关系,预测地下水资源开发过程中可能出现的环境地质问题,提出合理开发利用地下水资源的意见。  相似文献   

Computational microstructure modeling to estimate progressive moisture damage behavior of asphaltic paving mixtures     

Hoki Ban  Yong‐Rak Kim  Suk‐Keun Rhee 《国际地质力学数值与分析法杂志》2013,37(13):2005-2020

This paper presents a computational microstructure model to estimate the progressive moisture damage of multiphase asphaltic paving mixtures. Moisture damage because of water transport is incorporated with mechanical loading through a finite element method. To simulate nonlinear damage evolution in the mixtures, the model includes Fickian moisture diffusion, a cohesive zone model to simulate the gradual fracture process, and a degradation characteristic function to represent the reduction of material properties because of moisture infiltration. With the model developed, various parametric analyses are conducted to investigate how each model parameter affects the material‐specific moisture damage mechanism and damage resistance potential of the mixtures. Analysis results clearly demonstrate the significance of physical and mechanical properties of mixture components and geometric characteristics of microstructure for the better design of asphaltic paving mixtures and roadway structures. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Systematic marine conservation planning in data-poor regions: Socioeconomic data is essential   总被引：1，自引：0，他引：1  

Natalie C. Ban  Gretchen J.A. Hansen  Michael Jones  Amanda C.J. Vincent   《Marine Policy》2009,33(5):794-800

Systematic planning for conservation is highly regarded but relies on spatially explicit data that are lacking in many areas of conservation concern. The decision support tool Marxan is applied to a reef system in the central Philippines where 30 marine protected areas (MPAs) have been established in communities without much use of biophysical data. The intent was to explore how Marxan might assist with the legally required expansion to protect 15% of marine waters, and how existing MPAs might affect that process. Results show that biophysical information alone did not provide much guidance in identifying patterns of conservation importance in areas where the data are poor. Socioeconomic data were needed to distinguish among possible areas for protection; but here, as elsewhere in marine environments, the availability of such data was very limited. In the final analysis, local knowledge and integrated understanding of socioeconomic realities may offer the best spatially explicit information. The 30 existing MPAs, which encompassed a small proportion of the reef system, did not limit future options in developing a suite of MPAs on a broader scale. Rather, they appeared to generate the support for MPAs that is obligatory for any larger zoning effort. In summary, establishing MPAs based on community-driven criteria has biological and social value, but efforts should be made to collect ecological and socioeconomic data to guide the continued creation of MPAs.  相似文献