Compton散射反问题的适定性的一些结果     

张廷杰  张兆田 《CT理论与应用研究》1995,4(3):40-42

本文对于Ｃｏｍｐｔｏｎ散射无损检测问题得出了非线性Ｖｏｌｔｅｒｒａ积分方程的模型，在某些通常容许的条件下证明了问题适定性，并探讨了一种图象重建的数值方法。  相似文献   

大尺度涡旋的正压不稳定   总被引：5，自引：4，他引：5  

罗哲贤 《气象学报》1995,53(3):281-288

用极坐标中线性化的正压涡度方程，将大尺度圆形基流上扰动的稳定性问题化为广义特征值的问题，得到了扰动振幅增长率沿方位角方向波数的关系。然后以不稳定模态的扰动流函数场作为初始场，在强、弱两类圆形基流的条件下，用直角坐标中准地转正压模式，分别实施积分时间为６０ｈ的试验。结果在模式大气中，初始扰动均随时间而增幅；强圆形基流的扰动增幅更快，并形成与台风螺旋云系看似有些相近的结构。  相似文献   

EFFECT OF WINTER MONSOON ON SUMMER MONSOON THROUGH AIR-SEA INTERACTION   总被引：2，自引：0，他引：2       下载免费PDF全文

罗会邦 《Acta Meteorologica Sinica》1995,(1)

In this paper the relationships between the sea surface temperature (SST) of Xisha and that in the northern Indianand northern Pacific Oceans,the geopotential height at 500 hPa level of the Northern Hemisphere,and rainfall in Chinaare studied statistically using data in the period of 1961—1992.Results show that in winter,the interannual variation inSST of Xisha describes that for a large oceanic region off the East Asia coast,and is closely related to the activity of EastAsia winter monsoon.On the other hand,there exist very high values of auto-correlation of Xisha SST anomaly fromDecember through the following July,but the anomalous condition is hardly correlated to that in the preceding autumn.The winter monsoon related anomalous SST condition in Xisha has a strong tendency to persist through the succeedingsummer monsoon season with the same sign.In addition,correlation maps of monthly mean rainfall in China with re-spect to Xisha SST of the same month show positive correlations with confidence level above 95% to the east of 110°Eand to the south of Changjiang (Yangtze) River during the months of October through April;the region becomes smal-ler in May and changes correlation sign in June;the positive correlation region is located in the middle and lower reachesof Changjiang River from July to September.The air-sea interaction plays an important role in these processes.  相似文献   

SOME RELATIONS BETWEEN ASYMMETRIC STRUCTURE AND MOTION OF TYPHOONS   总被引：11，自引：0，他引：11       下载免费PDF全文

陈联寿  罗哲贤 《Acta Meteorologica Sinica》1995,(4)

The analysis of the SPECTRUM (Special Experiment Concerning Typhoon Recurvature andUnusual Movement) data indicates that the structure of recurving target typhoons 9015 (Abe),9019(Flo) and 9020 (Gene) at different stages of moving processes showed different motion features.Ondifferent time scales,temporal variations of typhoon structure and motion speed displayed differentfeatures.  相似文献   

利用NOAA－AVHRR资料提取水体信息的初步研究   总被引：2，自引：0，他引：2  

杨忠恩  骆剑承  徐鹏炜 《国土资源遥感》1995,(1)

本文讨论了应用ＮＯＡＡ－ＡＶＨＲＲ资料来提取水体信息的方法。采用ＡＶＨＲＲ一、二通道（下面简写为ＣＨ１、ＣＨ２）获得的地面反射率数据构成的归一化植被指数（ＮＤＶＩ）来识别水体，并初步提出了应用模糊数学的方法提取混合像元中的水体面积信息的技术思路。  相似文献   

大别山绿辉石晶体结构的再研究—兼与谢窦克等同志商榷   总被引：1，自引：0，他引：1       下载免费PDF全文

郭卫东  罗谷风 《地质论评》1995,41(4):311-319

谢窦克等曾测定了大别山一个绿辉石的晶体结构，认为它具Ｐ２／ｃ空间群；四面体链分别呈ＳＡ和ＯＢ扭转；Ｍ阳离子日位全部为６次配位的八面体：Ａｌ在所有这四种晶位另均有相当多的占有率，为绿辉石的新型结构。本文对该资料再研究后确认其真实空间群为Ｐ２／ｎ；结构中仅有一种Ｏ旋转的四面体链；Ｍ２和Ｍ２晶位为８次配位；Ａｌ全部进入Ｍ１（１）晶位，Ａｌ－Ｍｇ呈完全有序分布，属典型的Ｐ２／ｎ有序绿辉石。本文给出了重新计  相似文献   

从岩石Sm—Nd同位素模式年龄论北秦岭地壳增生和地壳深部性质   总被引：18，自引：5，他引：18  

张宏飞  赵志丹 《岩石学报》1995,11(2):160-170

北秦岭各岩类１１６个样品Ｓｍ－Ｎｄ同位素模式年龄（ｔＤＭ）变化于０．９～２．４Ｇａ之间，反映北秦岭地壳主要形成于元古代，０．９Ｇａ之后没有明显大规模新生地壳的形成。在Ｎｄ模式年龄分布图上出现２．０５Ｇａ、１．４０Ｇａ和１．０５Ｇａ三个明显的峰值，它们相应地代表北秦岭地壳的三个增生期。与华北克拉通南缘地壳存在２．６５Ｇａ、２．１０Ｇａ和１．４０Ｇａ三个增生期相对比，表明从华北克拉通南缘到北秦岭，地壳侧向增生是逐渐发展的，这是一个统一典型陆块的地壳增长过程，而北秦岭原来应属于华北的一部分。另外，从北秦岭花岗岩揭示的北秦岭地壳深部性质看，北秦岭地壳深部在１．０Ｇａ～１．２Ｇａ左右的板底垫托作用是相当明显的，而在晚古生代后可能又受到区域折离层作用的影响。  相似文献   

发展珠江三角洲经济区港口的远洋集装箱运输   总被引：1，自引：0，他引：1  

罗章仁  贾良文 《热带地理》1995,15(4):289-294

本文分析了珠江三角洲经济区远洋集装箱运输的落后现状，论述了三角洲经济区集装箱枢纽港尤其广州港和深圳港建设的重要性，同时指出该两港建设需要解决的问题。  相似文献   

西南地区洪涝灾害区划     

冯水志  罗德富 《山地学报》1995,(4)

统计分析了西南地区洪涝灾害面积、经济损失等。本区洪涝灾害成灾率高，损失大，活动在加强，损失的相对指标均明显高于全国平均水平。本区是我国洪涝灾害的严重危害区域之一，选择洪涝灾害活动强度、人类活动强度和经济活动强度为基础指标，建立洪涝灾害度计算模型，并按计算结果对洪涝灾害进行区划．  相似文献   

Nonlinear three- wave interaction among barotropic rossby waves in a large- scale forced barotropic flow     

Luo Dehai 《大气科学进展》1999,16(3):451-466

In this paper, the coupling equations describing nonlinear three-wave interaction among Rossby waves including the forcing of an external vorticity source are obtained. Under certain conditions, the coupling equations with a constant amplitude forcing, the stability analysis indi-cates that when the amplitude of the external forcing increases to a certain extent, a pitchfork bifurcation occurs. Also, it is shown from numerical results that the bifurcation can lead to chaotic behavior of “strange” attractor. For the obtained three-variable equation, when the amplitude of modulated external forcing gradually increases, a period-doubling bifurcation is found to lead to chaotic behavior. Thus, in a nonlinear three-wave coupling model in the large-scale forced barotropic atmospheric flow, chaotic behavior can be observed. This chaotic behavior can explain in part 30-60-day low-frequency oscillations observed in mid-high latitudes.  相似文献