卫星星座与编队飞行问题综述   总被引：3，自引：0，他引：3  

胡松杰  王歆  刘林 《天文学进展》2003,21(3):231-240

卫星应用的日益发展需要由多颗卫星组成的卫星系统(形成各种类型的星座)来替代单颗卫星，这就给卫星轨道力学的应用增加了一些新内容。重点阐述了卫星星座整体结构的演化、卫星星座编队飞行中的星-星相对几何构形及其保持问题，以及星座卫星定轨所涉及的测控方式和天地基网联合定轨问题。这些内容都是卫星星座轨道力学中的重要组成部分。  相似文献   

Characters of the Pco2 and CO2 Flux in the East China Sea in Autumn     

纪雷  崔鹤  辛淑平  王军  张龙军  陆贤昆 《中国海洋湖沼学报》2003,21(2):180-186

Pco2 of air and seawater samples from the East China Sea(ECS) were measured in situ in autumn, 1994,Ocean currents,terrestrial fluviation,biological activities,etc.,Pco2 char-acters in air and seawater were investigated,CO2 flux and its character in the East China Sea are discussed on the basis of the Pco2 profiles of air and seawater,It was clear that the nearshore was the source of CO2;and tht the oulter sea area was the sink of CO2; and that the shelf area of the EXS is a net sink for atmospheric CO2 in autumn.  相似文献   

STUDY ON THE INTERACTION BETWEEN NDVI PROFILE AND THE GROWING STATUS OF CROPS   总被引：5，自引：1，他引：4  

JIANGDong WANGNai-bin YANGXIao-huan WANGJi-hua 《中国地理科学(英文版)》2003,13(1):62-65

Daily and ten-day Normalized Difference Vegetation Index(NDVI) of crops were retrieved from meteorological statellite NOAA AVHRR images ,The temporal variations of the NDVI were analyzed during the whole growing season,and thus the principle of the interaction between NDIV profile and the growing status of crops was discussed,As a case in point,the relationship between integral NDVI and winter wheat yield of Henan Province in 1999 had been analyzed.By putting integral NDVI values of 60 sample counties into the winter wheat yield-integral NDVI coordination,scattering map was plotted. It demonstrated that integral NDVI had a close relation with winter wheat yield.These relation could be described with linear,cubic polynomial ,and exponential regression,and the cubic polynomial regression was the best way,In general ,NDVI reflects growing status of green vegetation ,so crop monitoring and crop yield estimation could be realized by using remote sensing technique on the basis of time serial NDVI data together with agriculture calendars.  相似文献   

DISASTER ANALYSIS AND COUNTERMEASURES OF LAND SUBSIDENCE CAUSED BY COAL CUTTING IN CHINA     

YANGYong-liang SHITong-guang JLANGLU-guang LIYue 《中国地理科学(英文版)》2003,13(2):130-133

In recent years, many coal-producing countries have paid great attention to the land subsidence causedby coal cutting. In China, because of the dense population in coalfield areas, the land subsidence hazard is more seri-ous. After a brief analysis on the mechanism of land subsidence, this paper gives a comprehensive and systematical ac-count on all kinds of hazards caused by the land subsidence in China. The study shows that land subsidence has endan-gered land, buildings, traffic and communication lines, dykes and dams. It also causes damage to ecological and socialenvironment. In order to lessen the hazard of land subsidence, preventive measures should be taken to reduce the col-lapse amount, such as extraction with stowing, banded mining system, succession and coordination mining system, orhigh-pressure mudflow between rock strata. Measures of reinforcing or moving certain buildings should also be taken toreduce the destructive degree. In order to harness the subsidence land and bring them under control for fanning, mea-sures should be taken such as filling with spoil or fine breeze, excavating the deeper and covering the shallower land.  相似文献   

Multistep matched-field inversion for broad-band data from ASIAEX2001     

Kunde Yang Yuanliang Ma Chao Sun Miller  J.H. Potty  G.R. 《Oceanic Engineering, IEEE Journal of》2004,29(4):964-972

This paper discusses the results of geoacoustic inversion carried out using explosive charge data from the Asian Seas International Acoustic Experiment (ASIAEX) East China Sea (ECS) Experiment. A multifrequency incoherent matched-field inversion processor and a genetic algorithm (GA) are used for the inversion. A multistep matched field inversion approach is presented, which makes use of the varying sensitivities of wave fields at various frequencies to reduce the inversion problem into a sequence of smaller inversions with fewer unknowns to estimate at each stage. Different parameters are estimated using data at different frequencies according to their sensitivities. Inversion results for different areas in the ECS region are summarized and compared with core data.  相似文献   

SORPTION AND DESORPTION CHARACTERISTICS OF CADMIUM BY FOUR DIFFERENT SOILS IN NORTHEAST CHINA   总被引：3，自引：0，他引：3  

ZHANG Lei SONG Feng-bin 《中国地理科学(英文版)》2005,15(4):343-347

1IN TR O D U C TIO NA s a persistentand toxic pollutant, cadm ium (C d) canresultin m any adverse health effects in a variety oftis-suesand organssuch asthe lung,kidney,urinary,blad-der,pancreas,breast and prostate (SA TA R U G etal.,2003).C adm ium in so…  相似文献   

法库地区大型韧性剪切带特征及成因机制     

杨晓波  高恩忆 《国土资源》1996,(2)

通过对辽北法库地区构造岩的观察和研究，确定了本区存在一大型推覆韧性剪切带。根据同构造侵入岩的同位素年龄，确定该韧性剪切带形成时期为海西－印支期，这与天山－兴安褶皱系最终形成时间相一致  相似文献   

Tidal effects on temperature front in the Yellow Sea   总被引：5，自引：0，他引：5  

Ma Jian  Qiao Fangli  Xia Changshui  Yang Yongzeng 《中国海洋湖沼学报》2004,22(3):314-321

Temperature front (TF) is one of the important features in the Yellow Sea, which forms in spring, thrives in summer, and fades in autumn as thermocline declines. TF intensity ⋎S _T ⋎ is defined to describe the distribution of TF. Based on the MASNUM wave-tide-circulation coupled model, temperature distribution in the Yellow Sea was simulated with and without tidal effects. Along 36°N, distribution of TF from the simulated results are compared with the observations, and a quantitative analysis is introduced to evaluate the tidal effects on the forming and maintaining processes of the TF. Tidal mixing and the circulation structure adapting to it are the main causes of the TF. Supported by the National Basic Research Program of China (No. G1999043809) and the National Science Foundation of China (No. 49736190).  相似文献   

2种亚洲龙鱼的D-Loop序列结构分析     

潘阳  白俊杰  叶星  劳海华  罗建仁  汪学杰 《广东海洋大学学报》2005,25(4):5-8

采用PCR技术对2种亚洲龙鱼的mtDNAD_Loop全序列进行扩增和测序,序列结构分析和序列同源性比对结果表明,2种亚洲龙鱼的mtDNAD_Loop在靠近5’端有3个终止相关序列TAS(Ⅰ、Ⅱ、Ⅲ),靠近D_Loop的3’端有4个保守区域CSB1、CSB2、CSB3、CSB-D。在终止相关序列和保守区域之间是连续重复区域。经DNASP4.0软件分析,全序列中检测出多态位点数(S)为26,其中有17个转换,核苷酸多样性(Pi)为0.013,平均核苷酸差异数(K)为17.333。  相似文献   

CATASTROPHIC ECO-ENVIRONMENTAL CHANGE IN THE SONGNEN PLAIN, NORTHEASTERN CHINA SINCE 1900S   总被引：1，自引：1，他引：0  

WANGHai-xia WANZhong-juan YUShao-peng LUOXin-zheng SUNGuang-you 《中国地理科学(英文版)》2004,14(2):179-185

Although the Songnen Plain in the northeastern China was developed relatively late in the temperate zone of the world, its eco-environment has changed greatly. This paper analyzes the changes of land cover and the rates and trends ofdesertification during the past 100 years in the Songnen Plain. According to the macroscopic analysis, we find that the eco-environment in the plain has reached to the threshold of catastrophic change since the 1950s. The Thorn Needle Catastrophic Model was used to determine and validate this conclusion. Human activities, including large-scale construction projects, such as huge dams and dikes, and excessive grazing were the primary factors contributing to regional eco-environmental catastrophe. And irrational reclamation of the wilderness also affected the eco-environmental change. The results reveal the complex human-land interactions.  相似文献