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981.
正常小儿颅内不同组织CT值 总被引:2,自引:0,他引:2
正常小儿脑组织CT值国内尚我报告;作者选择10岁以内正常小儿子120例,分三人年龄组进行颅内不同脑组织CT值测定,并将小儿与成人的脑绰组织值CT比较,收结果看出;小儿灰质、白质及小脑CT值明显低于成人的,随年龄增长CT值递增;新生儿脑组织CT值明显低于儿童;儿童丘脑莫过基底节CT值近似成人。 相似文献
982.
大同地震序列的震源机制解 总被引:1,自引:2,他引:1
使用CDSN长周期地震波形记录,利用Helmberger(1968)的广义地震射线理论得到的线性反演地震矩张量的方法,对1989年10月18日-1991年3月25日发生在大同的4个Ms>5.0的地震进行了反演,计算了这些地震矩张量和断层面解。 相似文献
983.
984.
The effects of asymmetric potential vorticity forcing on the instability of South Asia High and Indian summer monsoon onset 总被引:1,自引:0,他引:1
Based on the theory of potential vorticity(PV),the unstable development of the South Asia High(SAH)due to diabatic heating and its impacts on the Indian Summer Monsoon(ISM)onset are studied via a case diagnosis of 1998.The Indian Summer Monsoon onset in 1998 is related to the rapidly strengthening and northward moving of a tropical cyclone originally located in the south of Arabian Sea.It is demonstrated that the rapid enhancement of the cyclone is a consequence of a baroclinic development characterized by the phase-lock of high PV systems in the upper and lower troposphere.Both the intensification of the SAH and the development of the zonal asymmetric PV forcing are forced by the rapidly increasing latent heat released from the heavy rainfall in East Asia and South East Asia after the onsets of the Bay of Bengal(BOB)monsoon and the South China Sea(SCS)monsoon.High PV moves southwards along the intensified northerlies on the eastern side of the SAH and travels westwards on its south side,which can reach its northwest.Such a series of high PV eddies are transported to the west of the SAH continuously,which is the main source of PV anomalies in the upper troposphere over the Arabian Sea from late spring to early summer.A cyclonic curvature on the southwest of the SAH associated with increasing divergence,which forms a strong upper tropospheric pumping,is generated by the anomalous positive PV over the Arabian Sea on 355 K.The cyclone in the lower troposphere moves northwards from low latitudes of the Arabian Sea,and the upper-layer high PV extends downwards and southwards.Baroclinic development thus occurs and the tropical low-pressure system develops into an explosive vortex of the ISM,which leads to the onset of the ISM.In addition,evolution of subtropical anticyclone over the Arabian Peninsula is another important factor contributing to the onset of the ISM.Before the onset,the surface sensible heating on the Arabian Peninsula is very strong.Consequently the subtropical anticyclone which dominated the Arabian Sea in spring retreats westwards to the Arabian Peninsula and intensifies rapidly.The zonal asymmetric PV forcing develops gradually with high PV eddies moving southwards along northerlies on the eastern side of the anticyclone,and a high PV trough is formed in the middle troposphere over the Arabian Sea,which is favorable to the explosive barotropic development of the tropical cyclone into the vortex.Results from this study demonstrate that the ISM onset,which is different from the BOB and the SCS monsoon onset,is a special dynamical as well as thermodynamic process occurring under the condition of fully coupling of the upper,middle,and lower tropospheric circulations. 相似文献
985.
目前钻孔应变观测一般为水平应变,使用无限岩石平板中的钻孔应力集中模型,可反演出水平应力场分布及变化.如果在此基础上加上垂向应力测量,就可反演出三维应力场分布.本文介绍的RZB型深井宽频带地形变综合观测系统的垂向应变测量单元,外钢筒为波纹管结构,并通过螺旋刻丝、热处理等技术,其垂向等效弹性模量比耦合水泥低一个数量级,同时垂向应变钢筒的水平向等效弹性模量高于垂向弹性模量一个数量级.垂向应变探头的力学结构可以被形象地看成是一个螺旋柱形弹簧,其轴向极易产生弹性形变,而水平向的硬度却得到了极大的加强,因此可在竖井中较为准确地测量轴向应变. 相似文献
986.
本文以天津市房地产开发(集团)河西友谊小区综合楼为研究对象,研究其在地震作用下高层建筑的可靠性,探索高层建筑结构系统的抗震可靠性分析方法,本文还对比一般框架梁柱结构与后张无粘结预应力板柱结构抗震可靠性的差异,研究层数变化时可靠性所受的影响,得到满意的结果。 相似文献
987.
地震期间的地磁脉动效应 总被引:1,自引:1,他引:1
1996年11月17日至11月29日在新疆喀仁地区8次地震期间观测到的震前发生的高频地磁脉动现象,文中对每次地震前的Pcl-2脉动的形态,以及脉动的起动时刻,持续时间,H分量和D分量的平均振幅随北京地方时的分布进行了详细研究分析,对这种震前观测到的高频地磁脉动的激发机制也做了深入的讨论,事实表明,这种震前发生的高频地磁脉动的地震的短期预报上可能有广泛的应用前景。 相似文献
988.
Aromatic hydrocarbons are generally main distillation of crude oil and organic extract of source rocks. Bicyclic and tricyclic aromatic hydrocarbons can be purified by two-step method of chromatography on alumina. Carbon isotopic composition of individual aromatic hydrocarbons is affected not only by thermal maturity, but also by organic matter input, depositional environment, and hydrocarbon generation process based on the GC-IRMS analysis of Upper Ordovician, Lower Ordovician, and Cambrian source rocks in different areas in the Tarim Basin, western China. The subgroups of aromatic hydrocarbons as well as individual aromatic compound, such as 1-MP, 9-MP, and 2,6-DMP from Cambrian-Lower Ordovician section show more depleted 13 C distribution. The 13 C value difference between Cambrian-Lower Ordovician section and Upper Ordovician source rocks is up to 16.1‰ for subgroups and 14‰ for individual compounds. It can provide strong evidence for oil source correlation by combing the 13 C value and biomarker distribution of different oil and source rocks from different strata in the Tarim Basin. Most oils from Tazhong area have geochemical characteristics such as more negative 13C9-MP value, poor gammacerane, and abundant homohopanes, which indicate that Upper Ordovician source rock is the main source rock. In contrast, oils from Tadong area and some oils from Tazhong area have geochemical characteristics such as high 13C9-MP value, abundant gammacerane, and poor homohopanes, which suggest that the major contributor is Cambrian-Lower Ordovician source rock. 相似文献
989.
990.