CT机X射线高频高压发生器的研究

高频高压发生器是CT高压系统中最重要的组成部分.本文主要介绍高频高压发生器的组成和原理、高频逆变器脉冲控制的FM和PM方法、高频磁芯材料的选择、绕组的设计、损耗的计算、电磁兼容的考虑、高压整流电路的设计.研制20KHz和50kHz高压发生器的体会.     

海南岛北西部新构造特征及其演化研究

利用DGPS系统测量海南岛西部阶地, 绘制地质地貌综合剖面, 将西部阶地分为海成阶地和河流阶地两种。 其中海成地貌包括一条砂堤和四级阶地: 砂堤宽2～10 m, 高程约10 m, 形成于5 ka以来; 海成一级阶地发育较好, 阶地面高程21～22 m, 形成于晚更新世至全新世之间; 海成二级阶地顶面高程约32 m左右, 形成于晚更新世晚期; 海成三级阶地较为发育, 阶地面高程40～42 m, 形成于121.8 ka; 海成四级阶地零星分布, 阶地面高程约57 m, 形成于中更新世晚期。 河流阶地也可分出四级: 一级阶地高程约20 m, 局部发育, 形成于11.4 ka; 二级阶地高程约34 m, 形成于47.2 ka; 三级阶地高约50 m, 其基座顶面标高约41 m, 形成于晚更新世早期; 四级阶地高程约71 m, 基座面标高约60 m, 形成于中更新世晚期。 这些阶地中均以二级最为发育。 晚更新世以来全区处于整体加速抬升的状态。 依据阶地面的综合剖面特征, 认为王五-文教断裂晚更新世以来的活动性较弱。     

春秋两季鄱阳湖浮游动物的编目、数量分布与变动

分析鉴定了1999年春、秋两季,在鄱阳湖区8个断面24个采样站采得的水样．共观察到各类浮游动物共150种．其中轮虫动物物种最为丰富,为96种,占总种数的64．0％,且单位体积的数量亦呈明显优势,说明轮虫动物是该湖区浮游动物的优势类群;其次为原生动物．24个采样站中,原生动物、轮虫动物、枝角类、桡足类这四类浮游动物个体数量分布的差异极大,其中第10、12、13和23号站中的个体数量较高,超过100ind／L最大数量出现在13号站,个体数量高达1101．60ind／L鄱阳湖浮游动物的数量有明显的季节变动,尤属轮虫的变动最大．本次调查中轮虫和枝角类的数量春季大于秋季,而原生动物和桡足类则秋季大于春季．     

结构健康监测系统设计标准化评述与展望

阐述了结构健康监测的概念和内涵。详细介绍了结构健康监测系统的功能、组成和应用现状。结构健康监测系统设计标准化能够促进健康监测的应用和发展,具有重要的工程意义。对世界范围内相关研究进展进行了综述和评价。强调在我国建立监测系统设计标准的重要性,并提出了相应的说明和建议。设计标准可以分为总则、外观检查与无损检测、传感器的选择与布置、信息采集与处理系统、通信与传输系统、损伤识别和评估系统、应用实例等7部分。结构健康监测系统设计标准的实现将有力地推动健康监测的研究。     

Analysis on Double-difference Earthquake Location and the Seismicity Pattern of the Yangjiang Earthquake Sequences

The locations of about 400 earthquakes in Yangjiang, Guangdong Province are determined using the double, difference earthquake location algorithm （DDA）. The seismicity pattern becomes concentrated from discrete grids. The rupture characteristics of the Yangjiang earthquake sequence show a conjugated distribution in NW and NE directions. The major distribution trends NE and dips NE with an angle of 30^o and a length of 30km,and the minor distribution trends NW and dips SE with an angle of 30^o and a length of 20km. The focal depth is 5km - 15km. The distribution of the Enping earthquake sequence,which is not far from Yangjiang,is NW-trending. The relationship between hypocenter distribution and geological structure is discussed.     

大尺度雁列断层粘滑运动数值模拟

通过ANSYS软件建立二维雁列断层模型,采用粘弹性力学参数,建立摩擦系数接触单元,模拟10万年时间大尺度雁列走滑断层活动（地震相关活动）,分析挤压条件下的断层活动特征,研究结果表明：①断层时空区域不同,所受应力也不同,接近贯通区域重合地区所受应力较大,粘滑运动剧烈,由贯通区域向断层两侧逐渐延伸,所受应力依次减小;②摩擦系数越小,地震发生频率越高,地震运动周期越短,则位错量相对较小,易发生震级较小地震;摩擦系数越大,地震发生频率越低,地震运动周期越长,则位错量相对较大,易发生震级较大地震;③给定的边界挤压速率越大,地震发生频率越高,地震运动周期越短,则位错量增大,易发生震级较大地震。     

龙门山及其邻区的构造和地震活动及动力学

论述了龙门山推覆构造带、岷山隆起、成都平原和龙泉山地区的构造和地震活动，讨论了构造活动特点和演化历史，并分析了它们的形成机制和动力学问题     

Mechanism of the June 4, 2000 Southern Sumatra, Indonesia, earthquake

Introduction The June 4, 2000 southern Sumatra, Indonesia, earthquake (16h28min26.2s UTC, 4.72, 102.09, 33 km, MS=8.0 [IRIS]) occurred under the Indian Ocean, near the Mentawai fault, along the well-known Sumatran subduction zone and the great Sumatran fault, all of which trend northwest-southeast. 1 800 houses were totally destroyed, 10 196 were heavily damaged, and 18 378 were slightly damaged by the earthquake. At least 97 people were killed, 1 900 were injured, and 122 000 were left…     

克孜尔水库跨断层形变年变特征分析

通过对克孜尔水库跨断层形变特征进行分析,结果显示:①垂直形变每年3～4月、10～11月分别为峰、谷值时间;水平形变每年6～7月、1月分别为峰、谷值时间.②垂直变形的峰-谷时间间隔在1997年之前多为5～8个月,1998年后多为1～3个月;谷-峰值时间间隔在1997年前多为4～7个月,1998年后多在8～11个月.水平形...     

太湖流域城市化对平原河网水系结构与连通性影响

太湖流域的快速城市化使河流形态发生了改变,影响了平原河网水系结构与连通性本文以近几年城市化发展较为迅速的张家港地区为例,基于景观生态学和图论的相关理论,利用2002与2015年的水系数据,对全区以及各行政分区水面率、河网密度、河频率等指标进行研究,旨在揭示该地区河网水系结构与连通性参数变化及城市化对其影响结果表明:研究区2015年与2002年相比全区各水系结构指标都呈减小趋势,水面率、河网密度、河频率的衰减率分别为15.7%、12.6%、33.3%,河网有主干化趋势,干流面积与长度发育的同步性较好;不同行政区的水系变化有明显的空间分异,张家港南部水系较北部水面率、河频率衰减更剧烈;东北部地区河网密度与河网复杂度变化明显;张家港全区河网连通性略有提高,但地区分异明显,沿江的西北部地区河网连通能力有所加强,而东南部内河区域河网畅通程度减弱,被圩区、水闸与泵站切断的水系需要更合理的调度方案才能增强并维持水体的连通度;水面率、河网密度与人口、GDP之间相关水平较高,各地区水系结构参数与其变化率的空间分异和该地区人口、经济发展水平密切相关;河网河链数、节点数受城市化影响较大,线点率、实际连通度的变化与城市化指标相关性较弱本研究可以为后期张家港地区优化水系结构及防洪排涝建设提供基础,并帮助基于各片区的特点开展因地制宜的管理.     

Palynofloral changes in the Upper Paleozoic and Mesozoic of the Deocha-Pachami area,Birbhum Coalfield,West Bengal,India

The study of Upper Paleozoic and Mesozoic palynomorphs in three boreholes from the Deocha-Pachami area, Birbhum Coalfield, West Bengal, India, has allowed dating of the Talchir, Barakar, Dubrajpur, and Rajmahal formations, and revealed many hiatuses. The lowermost unit, the Talchir Formation, yielded earliest Permian palynomorphs. The Barakar Formation, which includes coal-bearing strata, was previously dated as Early Permian. However, data presented herein indicate an Early Permian to earliest Triassic age for this unit-containing actually the Karharbari, Barakar s.s., Kulti, and Ranigang formations as well as the basal part of the Panchet Formation. The overlying Dubrajpur Formation is Jurassic (Callovian to Tithonian), with an unconformity at its base. The uppermost Dubrajpur Formation is Tithonian-Berriasian. The palynomorphs from the intertrappeans within the Rajmahal Formation suggest an Early Cretaceous age. The revised ages of the Barakar and Dubrajpur formations are of major regional significance. The distribution patterns of spore-pollen may provide a broad spectrum of paleoclimate during Permian, Late Jurassic, and Early Cretaceous times, as there is no record of marine signatures in the study area.     

Evolution of Can-Etili(Canakkale-NW Turkey) lignite basin:Sedimentology,petrology,palynology and lignite characterization

This study examines the development and sedimentology of Can-Etili lignite basin in Biga Peninsula(NW Turkey) along with the palynologic and petrographic properties of the coals in this region.The CanEtili lignite basin discordantly overlies Oligocene-aged Can volcanics.The basin consists of caldera type sedimentation developed by the combined effects of volcanism and tectonics.The volcanic rocks forming the basement of the basin consist of andesitic,dacitic and basaltic lava flows as well as agglomerates,tuff and silicified tuffs,and kaolin which is their alteration product.The basement volcanic rocks cooled from high potassium and calc-alkaline magma.The trace element geochemistry of different rocks within the volcanics reveals that they are from a volcanic arc.The Can Formation contains lignites and consists of6 lithofacies representing alluvial,fluvial,marsh and lacustrine environments.These lithofacies are the lower volcanogenic conglomerate,the claystone,the lignite,the laminated organic claystone,the tuff intercalated sandstone-siltstone and the upper volcanogenic conglomerate.The lignite in the basin is limnic and is formed in a non-fluvial marsh and marsh-lake environment.An abundant percentage of vegetation(Engelhardia,Sapotaceae,Cyrillaceae) is compatible with temperate and subtropical climatic conditions in the basin during sedimentation of lignite.The coals of Can-Etili basin are humic with high sulfur content(6-6.5%average) mostly containing huminite compounds belonging to the class of lignitelow bituminous(C-A) coal.Their coalification rank is between 0.38%and 0.56%Ro.The coals are formed in limnic-limnotelmatic marsh zones based on their microlithotype components.The inorganic components of the coal mostly consist of pyrite and clay.The trace elements,As,Th,U and V,are higher than international coal standards.The coal quality is adversely affected by high sulfur content and sulfur driven trace element enrichments.The lignite reserve(possible-proved) of Can-Etili basin is greater than a hundred million tons,and the average coal seam thickness is 17 m.The lignite production in the basin is 3 mt/year and 1.8 million tons of this are used in the local thermal power plant.     

盐碱池塘浮游动物的群落演替和多样性

于1997年4月5日至1998年9月1日对山东高青赵店乡渔场34个盐碱池浮游动物群落演替及其多样性进行了研究,采集了389个浮游动物定量水样。结果表明,轮虫主要是在夏秋高温季节占主导地位,桡足类在春季和秋末冬初在大部分养鱼池和所有无鱼对照池中占绝对优势,原生动物在养鱼池浮游动物中占相当比重,浮游动物生物量的冬季变动一般都有放养早期的春季生物量峰值和盛夏至初秋的生物量高峰,浮游动物多样性指数的季节变动形式与浮游动物生物量的季节变动不尽相同,其季节变动的总趋势是,冬季最低,春季开始上扬,夏季最高,秋季又开始下降;浮游动物多样性指数在浮游动物生物量峰值时多是低谷,而生物量下降时多样性指数又上升,无鱼对照池和新挖池塘的浮游动物多样性指数和生物量均较一般养鱼池塘的高。     

Preliminary Study on Cenozoic Group and Fault Activity in the Sea Area Near the Yangtze River Mouth

By shallow seismic prospecting, the Cenozoic Group in the sea area near the Yangtze Rver Mouth can be divided into five seismic sequences. They correspond to the Quaternary,Pliocene, Upper Miocene, Lower Miocene and Eocene respectively. The Quaternary System covers all the detecting area. The Tertiary System overlaps and thins out from NE to SW. The sedimentary basement mainly consists of volcanic rock (J3) and acidic rock (r35). Paleogene or Late Cretaceous basins are not found there. The faults that have been detected are all normal faults. They can be divided into three groups (NE, NW, near EW) by their trend. The NE and NW-trending faults are predominant, and agree with aeromagnetic anomaly. Their length and displacement are larger than that of the EW-trending faults. The activity of the NEtrending faults is different in different segments. The SW segment is a Quaternary fault, the middle segment is a Neogene fault, The NE is Paleogene. But the segment of the NW-trending fault is not obvious. The average vertical displacement rate is about 0.015mm/a.     

汶川地震序列早期特征及成因探讨

地震序列的特征和震型判定工作有助于抗震救灾工作的开展,对其发生成因的研究是解决地震预报难题必须面对的科学问题。汶川8．0级地震序列的初步研究表明：①余震沿龙门山断裂带分布于宽100km,长约330km的带状区域内,并侧向于主震震中的北侧;②序列发展初期有2个快速衰减过程;③序列类型为主震一余震型,最大强余震6．4级;④序列的空间演化过程,强余震震源机制结果和地震精确定位结果分析表明,序列具有分段特征;⑤8．0级地震的发震构造是龙门山断裂带,发震构造在剖面上呈现出“犁形”或“铲形”。地球物理勘探和壳、幔结构反演结果表明,自青藏高原穿越龙门山到四川盆地存在地幔阶梯,上地幔阶梯的阻挡作用使得物质东移速率减慢,并蕴积了汶川8．0级地震所需能量。地震的产生正是东西向应力平衡被打破的结果,余震沿龙门山断裂的分布是高原地壳在印度板块的推挤作用下向北北东方向的运动得以继续的表现。整个龙门山断裂带都参与了活动,龙门山断裂带北端作为断裂带的止裂端与南段同期活动。     

引力场球谐综合的Walsh变换方法

提出直接在序率域内用Walsh变换实现引力场球谐综合的问题。给出球谐函数展开式的Walsh变换及快速算法,讨论了Walsh变换和Walsh-Fourier变换、Fourier变换之间的差异,分析了用地球重力场模型OSU81的位系数作出的Walsh变换和Fourier变换的结果。研究表明:Walsh变换与Walsh-Fourier变换、Fourier变换对应向量在数量方面的差值通常都小于士10~(-5);对于给定的阶数和飞行高度,3种方法求得的球谐综合值总是完全一致的;1°×1°等网格数据和Walsh函数形状相近。在重力场研究中Walsh级数会比Fourier级数收敛得更快;Walsh变换在计算速度、计算准确度、数据储存、收敛速度和方法简单方面都好于Fourier变换。     

天水-礼县地区地壳速度结构

1984—1985年,利用厂坝铅锌矿工业爆破,在天水—礼县地区布设测线进行了大范围的地震测深工作。对该地区的地壳速度结构的研究结果表明,该地区沉积层平均厚度为2.5km,速度为4.0km/s(P波);地壳平均厚度为43.68km,平均速度为6.20km/s;徽县—礼县地壳速度剖面可分为5层,其中在24—29km深处有一低速层,基底深度变化较大,在礼县地壳浅部发现一断层。对天水—礼县地区还进行了P波、S波联合反演,获得了该区P波与S波速度结构,其地壳范围内的平均波速比为1.73。     

地闪对崇明地震台地球物理观测的干扰

通过对比崇明地区地闪及崇明地震台地球物理观测资料,发现受地闪引起的电磁场变化的直接作用或对仪器元件的间接作用,地磁、地电、电磁扰动和水位观测干扰比例较高,干扰幅度与地闪距离及形成的电流强度有关。具体干扰形态如下：①对电磁扰动干扰表现为单向突跳和测值的整体抬升;②对地磁测项干扰表现为正负方向的单点突跳;③对大地电场干扰表现为大幅震荡;④对水位观测干扰表现为大幅突跳。     

Fine structure of auroras during auroral breakup according to the ground-based and satellite observations

The dynamics and fine structure of auroras before and during 60 auroral breakups, including pseudobreakups and breakups at moderate and high auroral activity, have been studied using the developed method for processing television images. The IMAGE and POLAR satellite and simultaneous ground images of auroras, ground magnetic data, and measurements of IMF and solar wind plasma parameters have been analyzed. The signatures that can be precursors of breakup have been found out in the auroral dynamics and morphology in the spatial—temporal vicinity of breakup. The morphological characteristics of auroral structures have been analyzed statistically. The directions of motion of weak subvisual structures have been determined. The velocities of motion of such structures are presented. The relation of the initial auroral arc bright-ening during breakups and pseudobreakups to the beginning of magnetic activation and formation of rayed structures has been analyzed.     

GPS测量方位角方法在琼中地磁台建设中的应用

介绍了GPS测量方位角的原理与方法。使用GPS测量了琼中地震台4个观测墩的方位角,取得较好的结果,并对测量结果的精度和误差来源进行了分析。结果证明,GPS测量方位角方法不受观测时间限制,受天气影响较小,对人员要求不高,观测时间只需2～3天,具有较大的应用前景。