Stanniferrous granites of Vietnam: Rb-Sr and Ar-Ar isotope age,composition, sources,and geodynamic formation conditions     

Anh  Phan Luu  Vladimirov  A. G.  Kruk  N. N.  Polyakov  G. V.  Ponomarchuk  V. A.  Hoa  Tran Trong  Phuong  Ngo Thi  Kuibida  M. L.  Annikova  I. Yu.  Pavlova  G. G.  Kiseleva  V. Yu. 《Doklady Earth Sciences》2010,432(2):839-845

Doklady Earth Sciences - Stanniferrous granite-leucogranite massifs in Vietnam to which the bedrock and placer commercial deposits of cassiterite are associated (Timtuc etc.) are of late Cretaceous...  相似文献   

Simple monitoring method for precaution of landslides watching tilting and water contents on slopes surface   总被引：2，自引：2，他引：0  

Taro Uchimura  Ikuo Towhata  Trinh Thi Lan Anh  Jou Fukuda  Carlos J. B. Bautista  Lin Wang  Ichiro Seko  Taro Uchida  Akira Matsuoka  Yosuke Ito  Yuichi Onda  Sho Iwagami  Min-Seok Kim  Naoki Sakai 《Landslides》2010,7(3):351-357

A low-cost and simple monitoring method for early warning of landslides is proposed. To detect abnormal deformation of a slope, this method employs a tilt sensor in place of an extensometer on the slope surface. In order to examine the relevance of measuring rotation angle on a slope surface by tilt sensor, model tests were conducted, and rotation on the slope surface was observed together with slide displacement along the surface. The rotation data responded 30 min before failure in a model test, which could be useful as a signal for early warning. However, the behavior of rotation before failure varies from case to case, and thus, criteria to issue warning should be defined more carefully. For a model slope made of uniform loose sand, measurement of slide displacement along the slope surface is sensitive to failure at the toe, while the measurement of rotation on the slope surface is useful to detect the development of progressive failure upward along the slope. Wireless sensor units with microelectromechanical systems (MEMS) tilt sensor and volumetric water content sensor were also examined on a real slope in Kobe City, and a long-term monitoring was attempted. A simple but possible way to define the criteria of judgment to issue warning can be proposed based on combination of data obtained by the tilt sensors and volumetric water content sensors.  相似文献   

Nitrogen and xenon in acid residues of iron meteorites     

S.V.S. Murty  P.S. Goel  D.Vu. Minh  Yu.A. Shukolyukov 《Geochimica et cosmochimica acta》1983,47(6):1061-1068

Total nitrogen, measured by neutron activation analysis, is highly enriched in residues from iron meteorites obtained by dissolution of the metal in dilute H₂SO₄, relative to the bulk value. On the average, the residues, representing 3% mass, contain 22% of total N. Group IA has more dissolved N than IIIA. Lithium and Ir show a distribution pattern parallel to N. Total Xe has been measured in several residues and its isotopic composition is, similar to atmospheric Xe for mass numbers 131 to 136 but not for ¹²⁴Xe and ¹²⁶Xe which are strongly depleted in the non-magnetic residues. It is suggested that iron meteorites have trapped in their micro-inclusions, some pre-solar nebular matter which is isotopically heterogeneous.  相似文献   

A simplified methodology for mapping groundwater vulnerability and contamination risk, and its first application in a tropical karst area, Vietnam     

Vu Thi Minh Nguyet  Nico Goldscheider 《Hydrogeology Journal》2006,14(8):1666-1675

A simplified methodology for mapping groundwater vulnerability and contamination risk is proposed, and the first application of the methodology, in a mountainous tropical karst area, is presented. The test site is the Tam Duong area, one of the poorest and remotest regions in northern Vietnam. The methodology requires a minimum of input data, which makes it particularly useful for developing countries. Vulnerability is assessed on the basis of two factors, which take into account the duality of recharge processes in karst aquifer systems: the overlying layers (O) and the concentration of flow (C). The risk map is obtained by putting together the vulnerability map and a simplified hazard assessment. The resulting maps provide a basis for groundwater protection zoning and land-use planning. Tracer tests and microbiological data confirmed the vulnerability and risk assessment in the test site.  相似文献   

Geochemistry,zircon U–PB ages and HF isotopes of the Muong Luan granitoid pluton,Northwest Vietnam and its petrogenetic significance     

Pham T. Hieu  Nong T. Q. Anh  Pham Minh  Nguyen T. B. Thuy 《Island Arc》2020,29(1)

The Indosinian Orogeny plays a significant role in tectonic background and magmatic evolution in Indochina and surrounding regions. Being a part product of the Indosinian magmatism in northwest Vietnam during late Permian–middle Triassic period, Muong Luan granitoid pluton dominantly consists of granodiorite, less diorite and granite. This pluton is located in the Song Ma suture and assigned to the Dien Bien complex. Geochemically, the Muong Luan granitoid rocks are characterized by a wide range of SiO₂ contents (59.9–75.1 wt%) and high K₂O contents. They display typical features of I‐type granites. The presence of hornblende and no muscovite and cordierite in the rocks further supports for I‐type character of granitoids. The emplacement age of the Muong Luan pluton obtained by LA–ICP–MS U–Pb zircon is at 242–235 Ma, corresponding to Indosinian time. Zircon ε_Hf values of –5.6 to –10.4, in combination with moderate Mg values of 34–45 suggested that the Muong Luan granitoid was derived from partial melting of mafic crustal source rocks, which are probably Paleoproterozoic in age as revealed by Hf model ages (T_DM2 = 1624–1923 Ma).  相似文献   

基于遗传算法的多光谱影像非监督训练分类系统     

HUNG Chih-Cheng  XIANG Mei  Minh Pham  KUO Bor-Chen  Tommy L. Coleman 《遥感学报》2007,11(5):702-709

本文将遗传算法（GA）应用于非监督训练,提高了遥感数据的分类精度。遗传竞争学习算法（GA-CL）综合了遗传算法和简单的竞争学习算法,可用于改进非监督训练的结果。遗传算法在典型样本聚类的过程中可以避免得到局部最优值。Jeffries-Matusita（J-M）距离法是通过统计测量两个训练类别之间的分离度,可用于评价这种算法。将此算法应用于TM数据的结果显示,遗传算法改进了简单的竞争学习算法,与其他非监督训练算法相比,其提供了K-均值,GA-K-均值和简单的竞争学习算法。  相似文献   

Effect of the bubble size on the dynamic adsorption of frothers and collectors in flotation     

Anh V. Nguyen  Chi M. PhanGeoffrey M. Evans 《International Journal of Mineral Processing》2006

  相似文献   

Probabilistic modelling of auto-correlation characteristics of heterogeneous slopes     

Thi Minh Hue Le  Marcelo Sánchez  Domenico Gallipoli  Simon Wheeler 《Geomechanics and Geoengineering》2015,10(2):95-108

Spatial variability of soil materials has long been recognised as an important factor influencing the reliability of geo-structures. This study stochastically investigates the influence of spatial variability of shear strength on the stability of heterogeneous slopes, focusing on the auto-correlation function, auto-correlation distance and cross-correlation between soil parameters. The finite element method is merged with the random field theory to probabilistically evaluate factor of safety and probability of failure via Monte-Carlo simulations. The simulation procedure is explained in detail with suggestions on improving efficiency of the Monte-Carlo process. A simple procedure to create cross-correlation between random variables, which allows direct comparison of the influence of each strength variable, is discussed. The results show that the auto-correlation distance and cross-correlation can significantly influence slope stability, while the choice of auto-correlation function only has a minor effect. An equation relating the probability of failure with the auto-correlation distance is suggested in light of the analyses performed in this work and other results from the literature.  相似文献   

A new species Lobophora tsengii sp. nov. (Dictyotales; Phaeophyceae) from Bach Long Vy (Bailongwei) Island,Vietnam     

Sun  Zhongmin  Dao  Minh Dong  Tran  Quoc Toan  Dam  Duc Tien 《中国海洋湖沼学报》2021,39(6):2363-2369

Journal of Oceanology and Limnology - A new species Lobophora tsengii is described from Bach Long Vy (Bailongwei) Island, Haiphong Province, Vietnam. The plants inhabit the subtidal zone and have...  相似文献   

基于越南遥感时间序列数据的湄公河三角洲土地利用及河岸变化检测研究   总被引：3，自引：0，他引：3  

阮林道  范巴赫  闵阮青  潘麦黎  蓬晃披 《资源与生态学报(英文版)》2011,(4):370-374

通过采用先进的遥感技术,基于光学和雷达时间序列卫星影像（陆地卫星,SPOT和雷达卫星）,本文对金瓯半岛（位于湄公河三角洲南部）土地覆被变化及湄公河河岸侵蚀情况进行了检测研究。鉴于金瓯半岛典型的土地覆被类型为红树林,通过对1973-2008年红树林遥感影像分析发现,近年来红树林林地面积急剧下降,超过一半的红树林已经转变为虾养殖场。与此同时,检测发现湄公河河岸已经被严重侵蚀,且侵蚀趋势正加速恶化。具体而言,田河和口河的左右两岸被认为是遭受严重侵蚀的热点区域。本文以1966-1968年地形图作为基准线数据,与1989-2009年卫星影像数据进行比照分析,此外采用数字海岸线分析系统（DSAS）模型对未来变化趋势进行了预测。  相似文献