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The Webster Scalar Curvature and Sharp Upper and Lower Bounds for the First Positive Eigenvalue of the Kohn-Laplacian on Real Hypersurfaces

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Acta Mathematica Sinica,English Series 2018年第8期34卷 1248-1258页

作者： song Ying LI duong Ngoc son Department of Mathematics University of California Irvine CA 92697-3875 Department of Mathematics Fujian Normal University Fujian 350108 P. R. China Fakultiit fiir Mathematik Universitiit Wien Oskar-Morgenstern-Platz 1 1090 Wien Osterreich

Let （M, θ） be a compact strictly pseudoconvex pseudonermitian manifold winch is CR embedded into a complex space. In an earlier paper, Lin and the authors gave several sharp upper bounds for the first positive eigenvalue λ1 of the Kohn-Laplacian □b on （M, θ）. In the present paper, we give a sharp upper bound for λ1, generalizing and extending some previous results. As a corollary, we obtain a Reilly-type estimate when M is embedded into the standard sphere. In another direction, using a Lichnerowicz-type estimate by Chanillo, Chiu, and Yang and an explicit formula for the Webster scalar curvature, we give a lower bound for λ1 when the pseudohermitian structure θ is volume-normalized.

关键词： CR manifold eigenvalue Kohn-Laplacian Webster curvature

Effect of Meteorological Factors on PM<sub>10</sub>Concentration in Hanoi, Vietnam

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Journal of Geoscience and Environment Protection 2019年第11期7卷 138-150页

作者： Nguyen Anh Dung duong Hong son Nguyen The Duc Hanh Doan Quang Tri Department of Science and Technology Ministry of Natural Resources and Environment Hanoi Vietnam Water Resources Institute Ministry of Natural Resources and Environment Hanoi Vietnam Faculty of Environment Hanoi University of Natural Resources and Environment Ministry of Natural Resources and Environment Hanoi Vietnam Vietnam Journal of Hydrometeorology Viet Nam Meteorological and Hydrological Administration Hanoi Vietnam

According to the Ministry of Natural Resources and Environment, Hanoi city is currently facing the increased air pollution, especially particulate matter. This study examines the influence of meteorological factors including temperature, humidity and wind speed on PM10 concentration in Hanoi. The data used in this study include 24-h PM10 concentration data, hourly temperature, humidity and wind speed data in 2018 at three automatic air monitoring stations under Vietnam Environment Administration and Hanoi Natural Resources and Environment Department. The SPSS statistical analysis tools are utilized to analyze the correlation between PM10 concentration and meteorological factors through the Spearman (r) correlation coefficient. Additionally, the Independent-Sample T-Test is also employed to assess the difference in PM10 concentration in the period between dry season (from October to March) and wet season (from May to September). The results show that there is a trend of seasonal variation of PM10 concentration. Specifically, PM10 concentration recorded a higher value in winter and lower in summer. Different correlations between air pollutants and meteorological factors were also observed. PM10 concentration was inversely correlated (r 10 concentration during dry and wetseason. This outcome has confirmed the important role of meteorological factors in the formation of air pollution with large variations in different seasons and geological areas.

关键词： Meteorology Temperature Humidity Wind Speed PM10 Air Quality

A comparative analysis of weight-based machine learning methods for landslide susceptibility mapping in Ha Giang area

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Big Earth Data 2023年第4期7卷 1005-1034页

作者： Thanh Trinh Binh Thanh Luu Trang Ha Thi Le duong Huy Nguyen Trong Van Tran Thi Hai Van Nguyen Khanh Quoc Nguyen Lien Thi Nguyen Faculty of Computer Science Phenikaa UniversityYen NghiaHa DongHanoi 12116Vietnam Phenikaa Research and Technology Institute(PRATI) A&A Green Phoenix Group JSCNo.167 Hoang NganTrung HoaCau GiayHanoi 11313Vietnam Northwestern Geological Division General Department of Geology and Minerals of VietnamHanoiVietnam Youth union office Thuyloi University175 Tay SonDong DaHanoiVietnam Center of Remote Sensing and Geohazards Vietnam Institute of Geosciences and Mineral ResourcesHanoiVietnam

Landslide susceptibility maps (LSMs) are very crucial for planningpolicies in hazardous areas. However, the accuracy and reliability ofLSMs depend on available data and the selection of suitable *** study is conducted to produce LSMs by combinations of machinelearning methods and weighting techniques for Ha Giang province,Vietnam, where has limited data. In study area, we gather 11 landslideconditioning factors and establish a landslide inventory *** the weights of classes (or factors) is very important toprepare data for machine learning methods to generate LSMs. Wefrst use frequency ratio (FR) and analytic hierarchy process (AHP)techniques to generate the weights. Then, random forest (RF), supportvector machine (SVM), logistic regression (LR), and AHP methods arecombined with FR and AHP weights to yield accurate and reliableLSMs. Finally, the performance of these methods is evaluated by fivestatistical metrics, ROC and R-index. The empirical results have shownthat RF is the best method in terms of R-index and the five metrics, *** rate (0.9661), FP rate (0.0), ACC (0.9835), MAE (0.0046), and RMSE(0.0350) for this study area. This study opens the perspective of weightbasedmachine learning methods for landslide susceptibility mapping.

关键词： Landslide logistic regression random forest SvM Vietnam

Ecoregional variations of aboveground biomass and stand structure in evergreen broadleaved forests

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Journal of Forestry Research 2020年第5期31卷 1713-1722页

作者： Tran Van Do Mamoru Yamamoto Osamu Kozan Vo Dai Hai Phung Dinh Trung Nguyen Toan Thang Lai Thanh Hai Vu Thanh Nam Trieu Thai Hung Hoang Van Thang Tran Duc Manh Cao Chi Khiem Vu Tien Lam Nguyen Quang Hung Tran Hoang Quy Pham Quang Tuyen Trinh Ngoc Bon Nguyen Thi Thu Phuong Ninh Viet Khuong Nguyen Van Tuan Dang Thi Hai Ha Tran Hai Long Dang Van Thuyet Dang Thinh Trieu Nguyen Van Thinh Tran Anh Hai duong Quang Trung Nguyen Van Bich Dinh Hai Dang Pham Tien Dung Nguyen Huy Hoang Le Thi Hanh Phan minh Quang Nguyen Thi Thuy Huong Hoang Thanh son Nguyen Thanh son Nguyen Thi Van Anh Nguyen Thi Hoai Anh Pham Dinh Sam Hoang Thi Nhung Hoang Van Thanh Nguyen Huu Thinh Tran Hong Van Ho Trung Luong Bui Kieu Hung Research Institute for Sustainable Humanosphere Kyoto UniversityUjiKyotoJapan Silviculture Research Institute Vietnamese Academy of Forest SciencesNorth Tu LiemHanoiVietnam Center for Southeast Asian Studies Kyoto UniversityKyotoJapan Vietnamese Academy of Forest Sciences North Tu LiemHanoiVietnam Vietnam Administration of Forestry No.2 Ngoc HaBa DinhHanoiVietnam

Biotic and abiotic factors control aboveground biomass(AGB)and the structure of forest *** study analyses the variation of AGB and stand structure of evergreen broadleaved forests among six ecoregions of Vietnam.A data set of 1731-ha plots from 52 locations in undisturbed old-growth forests was *** results indicate that basal area and AGB are closely correlated with annual precipitation,but not with annual temperature,evaporation or hours of *** area and AGB are positively correlated with trees>30 cm *** areas surveyed(52.6%)in these old-growth forests had AGB of 100–200 Mg ha^-1;5.2%had AGB of 400–500 Mg ha^-1,and 0.6%had AGB of>800 Mg ha^-*** percent of the areas surveyed had stand densities of 300–600 ***^-1,and 64%had basal areas of 20–40 m^2 ha^-*** is an important factor influencing the AGB of old-growth,evergreen broadleaved forests in *** causing the loss of large-diameter trees(e.g.,>100 cm DBH)affects AGB but may not seriously affect stand density.

关键词： Aboveground biomass Carbon storage Climatic variables Ecoregion Edaphic variables Oldgrowth forest

Soil Gas Radon Measurement for Identifying Active Faults in Thua Thien Hue (Vietnam)

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Journal of Geoscience and Environment Protection 2020年第7期8卷 44-64页

作者： Pham Tich Xuan Nguyen Anh duong Vu Van Chinh Pham Thanh Dang Nguyen Xuan Qua Nguyen Van Pho Institute of Geological Sciences Vietnam Academy of Science and Technology Hanoi Vietnam Institute of Geophysics Vietnam Academy of Science and Technology Hanoi Vietnam

The solid-state nuclear track detectors have long been applied to assess the activity of tectonic faults. We measured the Radon (Rn) concentration in soil gas on 09 profiles with a total of 245 measurement points in Thua Thien Hue area (Vietnam). Measurement results show that the Rn concentration in soil gas ranges from ~10 Bq/m3 to 144,570 Bq/m3. There is a clear difference in the Rn concentration on the granite rock of Dai Loc complex compared to the remaining rocks. The calculated background value and anomaly threshold of Rn concentration on the granite rock of Dai Loc complex and on the remaining rocks are 33,488 Bq/m3, 82,839 Bq/m3 and 5313 Bq/m3, 24,850 Bq/m3 respectively. Spatial distribution of Rn concentration in soil gas reflects the existence of faults since Rn concentration increases at the points above or near fault lines. The level of expression of fault activity is assessed by radon activity index (KRn), which is calculated by the ratio of anomaly value to background value of Rn concentration. According to KRn, in Thua Thien Hue area, only the Dakrong-Hue fault shows a strong expression of activity with high and very high KRn (the maximum KRn = 27.21). The Truong son, Huu Trach River, Ta Trach River and Bo River fault zones do not show clear activity with low and medium KRn. There is no Rn anomaly value recorded on the Rao Trang fault, demonstrating that it is likely to be inactive at present. The study results indicate that the Rn concentration in soil gas is a strong evidence of the existence of faults or tectonic fracture zones as the Rn concentration always increases at the points above or near the fault line.

关键词： Radon Active Fault Radon Activity Index Thua Thien Hue Vietnam

越南少数民族干部培养问题研究——以谅山省为例

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东南亚纵横 2016年第6期 65-70页

作者：吴凡滕志勇杨梅科广西大学公共管理学院广西大学中国-东盟研究院越南谅山省北山县共青团团委

越南谅山省是越南一个少数民族众多的省份,少数民族干部在其干部队伍建设中扮演着极其重要的角色。谅山省少数民族干部的培养呈现出干部和女性少数民族干部较多、高层次人才少、队伍呈过度年轻化趋势、政策环境弱的基本现状,并出现了整... 详细信息

越南谅山省是越南一个少数民族众多的省份,少数民族干部在其干部队伍建设中扮演着极其重要的角色。谅山省少数民族干部的培养呈现出干部和女性少数民族干部较多、高层次人才少、队伍呈过度年轻化趋势、政策环境弱的基本现状,并出现了整体素质有待改善、数量分布不均衡、年轻化严重、政策有待补充完善等问题,本文对越南谅山省少数民族干部培养存在的问题和原因进行分析,提出可从丰富少数民族干部培养途径、加大培养其他少数民族干部的力度、合理选拔任用各年龄阶段的少数民族干部、完善少数民族干部培养政策等路径,对越南谅山省少数民族干部培养现状进行优化,从而进一步提升越南少数民族干部队伍的素质。

关键词：越南谅山省少数民族干部培养