MSCT对不同体重注射不同对比剂量在主动脉CTA中的探讨

目的:探讨64层螺旋CT对不同体重注射不同对比剂量在主动脉血管成像中的应用效果.方法:60例临床可疑主动脉病变患者,知情同意后根据不同体重分为A、B、C三组,每组20例.A组:体重在75kg以上注射75mL对比剂+25mL生理盐水;B组:体重在60～75kg之间注射60mL对比剂+40 mL生理盐水;C组:体重在60k...     

利用COSMIC数据构建全球电离层TEC地图

电离层延迟效应是GNSS精密导航的主要误差源之一,通过建立电离层模型可不同程度地消除电离层延迟效应的影响.然而,目前海洋和气候条件极其恶劣的地区地面参考站建立困难,导致电离层观测资料的全球分布很不均匀,从而限制了现有电离层模型的精度,影响了延迟改正的效果.本文提出在日固坐标系(sun-fixed,地磁纬度和地方时)下,...     

基于相位编码的Fourier变换波动方程三维地震照明分析

复杂构造勘探是当前地震勘探的主要目标,提高深层信噪比和分辨率十分重要.地震照明分析是研究地震波能量在复杂构造中传播的有效手段,可指导观测系统设计进而提高野外数据采集和最终成像质量.本文发展了基于三维单程波动方程的地震照明方法,采用相位编码合成平面波源,一阶分离变量Fourier算子进行波场传播.阐述了照明和深度偏移之间...     

On the Significance and Use of the Generalized Moist Potential Vorticity Equation

In this paper,the continuity and thermodynamic equations including moisture forcings were derived.Using these two equations and the basic momentum equation of local Cartesian coordinates,the budget equation of generalized moist potential vorticity(GMPV) was derived.The GMPV equation is a good generalization of the Ertel potential vorticity(PV) and moist potential vorticity(MPV) equations.The GMPV equation is conserved under adiabatic,frictionless,barotropic,or saturated atmospheric conditions,and it is closely associated with the horizontal frontogenesis and stability of the real atmosphere.A real case study indicates that term diabatic heating could be a useful diagnostic tool for heavy rainfall events.     

The Seasonal Variations of Aerosols over East Asia as Jointly Inferred from MODIS and OMI

Data on aerosol optical thickness(AOT) and single scattering albedo(SSA) derived from Moderate Resolution Imaging Spectrometer(MODIS) and Ozone Monitoring Instrument(OMI) measurements,respectively,are used jointly to examine the seasonal variations of aerosols over East Asia.The seasonal signals of the total AOT are well defined and nearly similar over the land and over the ocean.These findings indicate a natural cycle of aerosols that originate primarily from natural emissions. In contrast,the small-sized aerosols represented by the fine-mode AOT,which are primarily generated over the land by human activities,do not have evident seasonalscale fluctuations.A persistent maximum of aerosol loadings centered over the Sichuan basin is associated with considerable amounts of fine-mode aerosols throughout the year.Most regions exhibit a general spring maximum. During the summer,however,the aerosol loadings are the most marked over north central China.This occurrence may result from anthropogenic fine particles,such as sulfate and nitrate.Four typical regions were selected to perform a covariation analysis of the monthly gridded AOT and SSA.Over southwestern and southeastern China,if the aerosol loadings are small to moderate they are composed primarily of the highly absorptive aerosols. However,more substantial aerosol loadings probably represent less-absorptive aerosols.The opposite covariation pattern occurring over the coastal-adjacent oceans suggests that the polluted oceanic atmosphere is closely correlated with the windward terrestrial aerosols.North central China is strongly affected by dust aerosols that show moderate absorption.This finding may explain the lower variability in the SSA that accompanies increasing aerosol loadings in this region.     

基于开口同轴法的岩矿石样品介电常数测试

火成岩及变质岩找矿是金属探矿的重要组成部分,围岩与矿体之间存在的电性差别是区分二者的重要标志;另外探地雷达以高频电磁波传播为基础,决定电磁波场波速的主要因素是介电常数,因此以介电常数及电导率为内容的电性参数测试就显得尤为必要.传统岩矿石介电常数测试主要使用同轴传输/反射法,而开口同轴法在岩矿石电性测试方面的工作开展较少...     

复杂地表边界元-体积元波动方程数值模拟

复杂近地表引起来自深部构造的地震反射信号振幅和相位的异常变化,是影响复杂近地表地区地震资料品质的主要原因.本文采用边界元-体积元方法,通过求解含复杂地表的波动积分方程,来模拟地震波在复杂近地表构造中的传播.其中,边界元法模拟地形起伏和表层地质结构对地震波传播的影响;体积元法模拟起伏地表下非均质低降速层的影响.与其他数值...     

浅议塔河地区“东河砂岩”三角洲沉积

近年来在塔河地区钻揭了一套典型的河控三角洲相“东河砂岩”,它与东河塘、塔中和哈得逊等地区发现的前滨相和滨面相“东河砂岩”明显不同.钻井岩心上该套三角洲相砂岩表现为板状交错层理、平行层理厚砂体;粒度概率具有河道、河口坝微相特征;平面上地震振幅、反射强度斜率属性异常呈以S99、T728井为中心的“鸟足状”外形;古盐度测试结...     

CO_2-H_2O流体不混溶对Au溶解度的影响——以贵州省贞丰县水银洞金矿床为例

运用热力学原理和方法,研究了CO2-H2O流体不混溶作用对Au的溶解度的影响。结果表明,贵州水银洞金矿床的成矿流体是一种富含挥发分（fCO2=70.79MPa）、酸性（pH=3.71）、还原性（fO2=0.50×10-36MPa）、中温（267℃）、具有超压（180MPa）性质的含Au（a∑Au=3.744×10-8mol/L）流体。当超压流体的封闭层——炭质页岩因断裂作用而被破坏时,热液体系的压力发生骤降（28.50～35.30MPa）,CO2-H2O流体发生不混溶作用,并有大量CO2溢出。CO2的流失可使成矿溶液的CO2逸度和O2逸度降低（fCO2=0.80MPa、fO2=2.512×10-42MPa）,酸碱度升高（pH=4.32）,同时伴随温度的下降（224℃）,成矿热液中Au溶解度的降低（a∑Au=3.790×10-9mol/L）,从而快速沉淀下来成矿。     

西南大面积低温成矿域：研究意义、历史及新进展

我国西南大面积低温成矿域是目前世界上公认的2个大面积低温成矿域之一,其面积之大（约100万km^2）、包含的矿种之多（Au、Hg、sb、As、P、Pb—Zn、Ag以及萤石、冰洲石、水晶、分散元素等）、矿床组成和组合之复杂全球罕见,是我国重要的Au、Hg、sb、As、Pb—zn、Ag以及多种分散元素生产基地。国内外学者对该成矿域进行了近30年的研究工作,取得了大量高水平研究成果,同时也存在许多有待深人研究的科学问题。本文回顾了我国西南大面积低温成矿域的研究历史,总结了各研究阶段的主要研究内容、主要研究成果和存在的主要科学问题,同时介绍了近年来我国西南大面积低温成矿域研究新进展。