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951.
Signs of the evolutionary process are well preserved in the aeolian deposits of desert margins and enable reconstruction of desert expansion and contraction. The sand content (percentage >63 µm) of loess in the loess–desert transitional zone was used as a proxy indicator for determining the proximity of the desert margin. According to the dominant wind direction, generally NW–SE in the northwest Chinese Loess Plateau, a transect was projected to observe spatial changes in sedimentological characteristics of aeolian deposits during the Last Glacial Period. The transect consists of 12 loess sections, starting at Shapotou in the transitional region between the Loess Plateau and the Tengger Desert and ending at Tianshui, which is located at the north foot of the Western Qinling Mountains in the southernmost part of the Loess Plateau. It shows the properties of temporal and spatial distribution of the Malan loess, with reduced sand content from northwest to southeast. A linear correlation model of sand content and distance was obtained, which was similar to the east of the Chinese Loess Plateau. According to this model, and on the basis of optically stimulated luminescence (OSL) dating from Binggou section, a detailed and quantificational expansion and contraction for the Tengger Desert was established. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
952.
The concentrations of Zn, Cd, Pb, Cu ions are shown to be similar in natural waters of Tianshan Mountains and Qinghai-Tibet
plateau and to be similar in those of the sea water. The average and variability of concentraions of trace metal ions in fresh
water are Zn 5.7±1.5, Cd 0.092±0.038, Pb 0.048±0.011, and Cu 1.1±0.20 ppb. The average concentrations in the East China Sea
are Zn 7.3 (5.5 in 1976), Cd 0.12, Pb 0.036, and Cu 0.94 ppb. It proves that the homogeneous distribution of trace metal ions
(free ion and unstable complexes) in natural waters is present in the nature as a rule.
Contribution No. 985 from the Institute of Oceanology, Academia Sinica. 相似文献
953.
杨保 《气候变化研究进展》2007,3(Z1):31-34
Temperature variations on the Tibetan Plateau during the last millennium are revealed by comparing a Qamdo tree-ring δ13C, the Dasuopu ice-core δ18O series, and a previous composite temperature reconstruction. Results show that an obvious warm period during 1200-1400 AD corresponds to the Medieval Warm Period (MWP) when summer temperature was 1.2℃ higher than the recent 1000 years average, and a cool phase from 1400 to 1700 AD, with summer temperature being 0.5℃lower than long-term average, can be correlated to the Little Ice Age (LIA). The 13th century was the warmest phase during the past 1000 years, while the coldest period occurred during 1000-1200 AD. The 20th century warming was characterized by rapid winter temperature rise while summer temperature at that time displayed a slight downward trend. 相似文献
954.
955.
956.
在卫星影像制作的DOM和DEM基础上,利用侦查无人机拍摄的影像照片,在DOM底图上计算目标的精确坐标和对DLG数据进行及时更新,满足了应急保障需要。 相似文献
957.
The United Nations Sustainable Development Goals (SDG) and the Response Strategies of China 总被引:2,自引:0,他引:2
Yanqiang Wei Xin Li Feng Gao Chunlin Huang Xiaoyu Song Bao Wang Hanqing Ma Penglong Wang 《地球科学进展》2018,33(10):1084-1093
The United Nations Sustainable Development Goals (SDG) which launched in 2015 inherited, extended and developed the merits of the United Nations Millennium Development Goals (MDG) in 2000. By the analysis of SDG goals, it can be found that SDG has mainly covered the securities of food supplies, disease prevention, social justice and human rights, the securities of water, energy, land and eco-environment. It covers the human, social, economic, and eco-environmental dimensions. To achieve it, the SDG should be localized and coordinated with the long-term development strategies of Chinese government. And the goals should be integrated into the policies and engineering projects of China simultaneously. By multilaterally cooperating with international communities and sharing the development experiences of other countries/regions, and confronting global issues together, the SDG can be achieved eventually by all the countries of the world. 相似文献
958.
在20世纪90年代,Lehrmann等把中国南方贵州省南部罗甸地区早三叠世的一个孤立的"罗甸碳酸盐岩台地",称作"大贵州滩"。在国外,已有300多篇文章引用"大贵州滩"这一术语。笔者等曾对中国南方早及中三叠世的岩相古地理进行过研究,根据我们的地质资料,在贵州省南部的罗甸地区,在早三叠世,只有一个孤立的"罗甸碳酸盐岩台地",没有"大贵州滩",也不能把"罗甸碳酸盐岩台地"称作"大贵州滩"。《古地理学报》(英文版)2015年第4卷第1期,刊登了冯增昭等的文章,There was no"Great Bank of Guizhou"in the Early Triassic in Guizhou Province,South China(中国南方贵州省早三叠世没有"大贵州滩")。本文是该英文文章的详细摘要,目的在于让国内的广大读者也知道:"大贵州滩"这一术语是严重的名不副实,不应继续使用。 相似文献
959.
塔里木盆地寒武系白云岩是深层、超深层油气勘探的重要接替层系,但该套白云岩具有时代古老、埋藏深、成岩和构造演化复杂的特征,亟需在揭示储集层成因基础上建立不同成因白云岩储集层配套测井评价方法。由此通过岩心、薄片观察,结合常规和成像测井首先从储集层孔隙成因角度出发,识别出“岩溶改造型”和“沉积相控型”两大类白云岩。岩溶改造型白云岩储集层质量受岩溶相带控制,纵向可划分出表层岩溶带、垂直渗流带、水平潜流带和深部缓流带4个岩溶相带。沉积相控型白云岩储集层物性则受沉积相带控制,颗粒滩等高能沉积相决定了储集层质量。通过岩心刻度常规和成像测井分别建立岩溶相带以及沉积微相的测井识别模式与准则,实现了单井岩溶相带和沉积微相的测井识别与划分。最后在岩溶相带和沉积微相约束下实现单井白云岩储集层综合评价以及有利发育区带预测。岩溶改造型白云岩储集层,其垂直渗流带与水平潜流带分别以高角度裂缝和水平溶蚀孔洞为主要特征,可形成有利储集体发育的缝洞系统。沉积相控型白云岩,其中的颗粒滩和云坪高能相带原始孔隙发育,且也有利于进一步溶蚀,因此物性较好。研究成果可为深层、超深层白云岩有利储集层分布预测提供理论指导和技术支撑。 相似文献
960.
Sk Ajim Ali Farhana Parvin Jana Vojteková Romulus Costache Nguyen Thi Thuy Linh Quoc Bao Pham Matej Vojtek Ljubomir Gigović Ateeque Ahmad Mohammad Ali Ghorbani 《地学前缘(英文版)》2021,12(2):857-876
Hazards and disasters have always negative impacts on the way of life.Landslide is an overwhelming natural as well as man-made disaster that causes loss of natural resources and human properties throughout theworld.The present study aimed to assess and compare the prediction efficiency of different models in landslide susceptibility in the Kysuca river basin,Slovakia.In this regard,the fuzzy decision-making trial and evaluation laboratory combining with the analytic network process(FDEMATEL-ANP),Na?ve Bayes(NB)classifier,and random forest(RF)classifier were considered.Initially,a landslide inventory map was produced with 2000 landslide and nonlandslide points by randomly dividedwith a ratio of 70%:30%for training and testing,respectively.The geospatial database for assessing the landslide susceptibility was generated with the help of 16 landslide conditioning factors by allowing for topographical,hydrological,lithological,and land cover factors.The ReliefF methodwas considered for determining the significance of selected conditioning factors and inclusion in the model building.Consequently,the landslide susceptibility maps(LSMs)were generated using the FDEMATEL-ANP,Na?ve Bayes(NB)classifier,and random forest(RF)classifier models.Finally,the area under curve(AUC)and different arithmetic evaluation were used for validating and comparing the results and models.The results revealed that random forest(RF)classifier is a promising and optimum model for landslide susceptibility in the study area with a very high value of area under curve(AUC=0.954),lower value of mean absolute error(MAE=0.1238)and root mean square error(RMSE=0.2555),and higher value of Kappa index(K=0.8435)and overall accuracy(OAC=92.2%). 相似文献