Dynamic processes of a simple linear dune—a study in the Taklimakan Sand Sea, China

Samples of dune sands, surveys of the morphology and field measurements of wind velocity and direction of a simple linear dune in Taklimakan Sand Sea show that the airflow and sand flux vary with the change of wind direction on the dune surface. Decrease of the airflow stress on the lee flank does not result in much decrease of the sand flux because of the low threshold shear velocities and the airflow conditions. There are no significant relations between the sand flux on the lee flank and the angle of incidence of the airflow. The low threshold shear velocities and the maintenance of the sand flux at the lee flank are the main mechanisms keeping the linear shape of the dunes. Measurements of the sand flux shows that it reaches a maximum on the crest of the dune. The grain size of the transported sands has some differences compared to that of the dune surface. The sands transported are finer than that on the dune surface, but better sorted under the influence of the medium to low wind activity. The field experiment results exhibit that it is possible for the dunes to be shaped as linear dunes during the processes of accumulation and elongation.     

盐渍土与分散性针孔试验影响

通过具体实例,研究了新疆氯盐渍、硫酸盐渍土对针孔试验的影响,认为氯盐渍土因其胶结作用,随着盐量的增加,土样孔径大小、流量变化不大。硫酸盐渍土因其膨胀性,随着盐量的增加,土样孔径、流量减小,对土样的冲蚀破坏作用而不相同。     

遥感技术在珠江三角洲基塘用地变迁调查中的应用——以顺德、南海基塘区为例

本文选用两个不同时相的TM卫片(1984年、1994年)作为调查基础资料,结合地形图和局部地区大比例尺黑白航片,通过解译量测,对珠江三角洲顺德、南海基塘区十一个镇的基塘用地变迁情况进行了调查。并利用TM4波段图像对基、塘信息进行了分离,同时估算了基、塘面积比。这次工作是利用TM图像对珠江三角洲地区这一特有的土地利用类型进行调查所作的一次有益的尝试,并取得了较好的效果。     

门静脉系统癌栓的CT表现

本文观察分析了肝癌侵犯门静脉，在门脉分支及主干内形成癌栓后的ＣＴ影像特征。发现４６例中有４１例（９１％）有门脉增宽，此征象在ＣＴ图像上容易发现和测量出，可作为门脉癌栓的辅助诊断依据；同时ＣＴ平扫可以发现早期新形成的栓子，其特点是增宽的门脉内高密度结节影，ＣＴ值平均５６±７·８Ｈｕ；另外增强扫描可显示出平扫低密度而无增强表现的癌栓影。同时对上述各征象的产生机制进行了分析。     

吉林省西部沙化土地持续农业体系建立的实践

吉林省沙化土地的８７．９％分布在吉林省西部白城、松原半干旱地区，统属科尔沁和松嫩沙地，面积９２１６．５ｋｍ２，占吉林省西部总面积的１９．６％。８年（１９８６年～１９９３年）实践证明：针对沙地环境特点建立的“乔、灌、草”、“果、药、杂”、“田、林、草”为主体的三种持续农业体系效果明显。     

弹性波CT技术及应用

弹性波ＣＴ技术是一种新的物探方法。本文简单地介绍了该技术的方法原理及影响图像重建的因素，并以实例说明了弹性波ＣＴ技术在煤矿井下的应用效果     

原生金矿成矿年龄测定研究

金成矿年龄和矿源同位素组成的准确测定，对金矿地质研究和找矿具有重要意义。本文根据３年多野外和室内工作的总结，获得了多个典型矿床的年龄和同位素测定结果：华北古陆北缘北侧槽区乌花敖包金矿测定为１３０—１２０Ｍａ的晚期造山作用成矿；南侧台区赛乌素金矿为２１１±１５Ｍａ的再循环古陆改造成矿；中段台区后沟一黄土梁金矿为２４３±７Ｍａ的古陆再造成矿；胶东焦家－乳山金矿为１２２．７±３．４Ｍａ和１２８±２３Ｍａ的燕山期成矿；华夏古陆八宝山金银矿为１４０±５Ｍａ的火山热液成矿。     

Coal-generated oil in Tuha Basin

The Turpan-Harmi (abbreviated to Tuha below) Basin is a typical basin of coal-generated oil accumulation in China. The Middle-Lower Jurassic coal measures are considered the main source beds. Hence, both desmocollinite and suberinite are considered the contributors for coal-generated oil. Principal geochemical features of the crude oil in the Tuha Basin are rich in alkanes (70%—80%), high pristane/phytane ratio (6—8), abundant heavy carbon isotope (δ¹³C PDB= -26%–-23%) and absolute GP sterane predominance. The hydrocarbon generation process from the coal series is characterized by multistages, early generation and early expulsion.