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

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 ecosystems.This 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 developed.The results indicate that basal area and AGB are closely correlated with annual precipitation,but not with annual temperature,evaporation or hours of sunshine.Basal area and AGB are positively correlated with trees>30 cm DBH.Most 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^-1.Seventy percent of the areas surveyed had stand densities of 300–600 ind.ha^-1,and 64%had basal areas of 20–40 m^2 ha^-1.Precipitation is an important factor influencing the AGB of old-growth,evergreen broadleaved forests in Vietnam.Disturbances 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

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Research and Experimental Application of Empirical Formulas to Calculate Riverbank Erosion in Tien River in the Mekong Delta

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Journal of Environmental Science and Engineering(A) 2021年第3期10卷 116-123页

作者： Can Thu Van nguyen thanh son Ngo Chi Tuan Ho Chi Minh City University of Natural Resources and Environment Ho Chi Minh City 700000Vietnam University of Science Vietnam National UniversityHo Chi Minh City 700000Vietnam

In recent years,the problem of riverbank and coastal erosion in the MD(Mekong Delta)is very complicated;landslides occur in most of the inland and coastal provinces.Most riverbank landslides occur gradually,but in contrast to sudden landslides that cause great damage,occur with increasing frequency.This shows that the trend of riverbank erosion will be more complicated and more frequent,especially in the context of extreme weather changes and changes in hydrological regime in the next time.Statistics from the authorities show that,if in 2010 the whole region had nearly 100 landslide points;by 2020 it had increased to more than 680 points;in which Dong Thap in the Tien River is one of the two localities with the most serious riverbank erosion.Currently,there are many methods used to assess and forecast the level of riverbank erosion in specific areas,such as:method of document analysis,measurement data;physical model;mathematical models and empirical formulas.In this study,the empirical formula is used to calculate the landslide level for the Tien River section in Cao Lanh,Dong Thap province.The calculation results according to the empirical formula have a certain agreement with the actual data,the correlation coefficient is 0.90 and the Nash coefficient is 0.78,the relative error of less than 15%is 80%of the cross-section.Such results have shown the possibility of applying empirical formulas to establish and calculate for other landslide areas along the banks of Hau River and MD.

关键词： Riverbank erosion MD empirical formula for calculating bank erosion

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Research to Establish a Set of Combinatorial Indicators to Calculate Flood Vulnerability Index in Thach Han-Ben Hai River Basin, Quang Tri Province, Vietnam

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Journal of Environmental Science and Engineering(B) 2021年第4期10卷 138-150页

作者： Ngo Chi Tuan nguyen thanh son nguyen Kien Dung Can Thu Van University of Science Vietnam National UniversityHanoi 1000000Vietnam Hanoi University of Natural Resources and Environment Hanoi 1000000Vietnam Ho Chi Minh City University of Natural Resources and Environment Ho Chi Minh City 700000Vietnam

In recent times,approaches to flood prevention and mitigation have changed a lot.These changes are to shift the focus from flood control to flood risk management,in which the assessment of vulnerability to floods caused by each sector and field corresponding to each flood magnitude is typical.Current flood vulnerability assessment studies are basically holistic based on factors affected by floods or in aspects:economy,society and ecological environment,and aspects that are mentioned in all areas of social life.The content of the flood vulnerability assessment method usually considers 3 components:E(Exposure),S(Susceptibility),A(Adaptability-Recovery).Each component will contain many different variables belonging to different objects and different natural-economic-social characteristics in each area.Therefore,for each research area,the evaluation method needs to establish an appropriate set of indicators.A set of indicators used to assess flood vulnerability must:be scientific;be practical;simplify the investigation,collection and synthesis of data.This study has established a set of combinatorial indicators including 27 indicators for the T-BRB(Thach Han-Ben Hai River Basin)on the basis of analysis and synthesis from case studies.

关键词： Vulnerability combine indicators T-BRB

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Establishing the Basic Indicator for the Calculation of the Flood Vulnerability Index for River Basins in Vietnam

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Journal of Environmental Science and Engineering(B) 2016年第8期5卷 390-394页

作者： Can Thu Van nguyen thanh son Phan Vu Hoang Phuong Hydrology Department Faculty of Hydro-Meteorology Hochiminh City University of Natural Resources and Environment Hochiminh City 70000 Vietnam Faculty of Hydro-meteorology & Oceanography Hanoi University of Science Hanoi 100000 Vietnam Climate Change Department Faculty of Hydro-Meteorology Hochiminh City University of Natural Resources and EnvironmentHochiminh City 70000 Vietnam

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Establishing the Method for Assessing Flood Vulnerability in Ho Chi Minh City, Vietnam A Case Study in District 6

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Journal of Environmental Science and Engineering(B) 2018年第2期7卷 72-82页

作者： Tran Thi Diem Loan Can Thu Van nguyen thanh son Do Thi Hong Hoa Insitute for Environment and Resources Vietnam National University Ho Chi Minh HCM City 700000 Vietnam Ho Chi Minh City University of Natural Resources and Environment HCM City 700000 Vietnam Ha Noi University of Science Vietnam National University Ha Noi Ha Noi 100000 Vietnam Vietnam Academy of Science and Technology Ha Noi 100000 Vietnam

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A comparative study on kinetics and dynamics of two dump truck lifting mechanisms using MATLAB simscape

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Theoretical & Applied Mechanics Letters 2024年第2期14卷 146-156页

作者： Thong Duc Hong Minh Quang Pham son Cong Tran Lam Quang Tran Truong thanh nguyen Faculty of Transportation Engineering Ho Chi Minh City University of Technology(HCMUT)Ho Chi Minh City 700000Vietnam Vietnam National University Ho Chi Minh City(VNU-HCM) Ho Chi Minh City 700000Vietnam Industrial Maintenance Training Center Ho Chi Minh City University of Technology(HCMUT)Ho Chi Minh City 700000Vietnam

In this paper,two lifting mechanism models with opposing placements,which use the same hydraulic hoist model and have the same angle of 50°,have been developed.The mechanical and hydraulic simulation models are established using MATLAB Simscape to analyze their kinetics and dynamics in the lifting and holding stages.The simulation findings are compared to the analytical calculation results in the steady state,and both methods show good agreement.In the early lifting stage,Model 1 produces greater force and discharges goods in the container faster than Model 2.Meanwhile,Model 2 reaches a higher force and ejects goods from the container cleaner than its counterpart at the end lifting stage.The established simulation models can consider the effects of dynamic loads due to inertial moments and forces generated during the system operation.It is crucial in studying,designing,and optimizing the structure of hydraulic-mechanical systems.

关键词： Dump truck Lifting mechanism Hydraulic MATLAB Simscape Kinetic dynamic analysis

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Unknown DDoS Attack Detection with Fuzzy C-Means Clustering and Spatial Location Constraint Prototype Loss

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Computers, Materials & Continua 2024年第2期78卷 2181-2205页

作者： thanh-Lam nguyen HaoKao thanh-Tuan nguyen Mong-Fong Horng Chin-Shiuh Shieh Department of Electronic Engineering National Kaohsiung University of Science and TechnologyKaohsiung807618Taiwan Department of Electronic and Automation Engineering Nha Trang UniversityNha Trang650000Vietnam

Since its inception,the Internet has been rapidly evolving.With the advancement of science and technology and the explosive growth of the population,the demand for the Internet has been on the rise.Many applications in education,healthcare,entertainment,science,and more are being increasingly deployed based on the internet.Concurrently,malicious threats on the internet are on the rise as well.Distributed Denial of Service(DDoS)attacks are among the most common and dangerous threats on the internet today.The scale and complexity of DDoS attacks are constantly growing.Intrusion Detection Systems(IDS)have been deployed and have demonstrated their effectiveness in defense against those threats.In addition,the research of Machine Learning(ML)and Deep Learning(DL)in IDS has gained effective results and significant attention.However,one of the challenges when applying ML and DL techniques in intrusion detection is the identification of unknown attacks.These attacks,which are not encountered during the system’s training,can lead to misclassification with significant errors.In this research,we focused on addressing the issue of Unknown Attack Detection,combining two methods:Spatial Location Constraint Prototype Loss(SLCPL)and Fuzzy C-Means(FCM).With the proposed method,we achieved promising results compared to traditional methods.The proposed method demonstrates a very high accuracy of up to 99.8%with a low false positive rate for known attacks on the Intrusion Detection Evaluation Dataset(CICIDS2017)dataset.Particularly,the accuracy is also very high,reaching 99.7%,and the precision goes up to 99.9%for unknown DDoS attacks on the DDoS Evaluation Dataset(CICDDoS2019)dataset.The success of the proposed method is due to the combination of SLCPL,an advanced Open-Set Recognition(OSR)technique,and FCM,a traditional yet highly applicable clustering technique.This has yielded a novel method in the field of unknown attack detection.This further expands the trend of applying DL and ML techniques in the development of intrusion det

关键词： Cybersecurity DDoS unknown attack detection machine learning deep learning incremental learning convolutional neural networks(CNN) open-set recognition(OSR) spatial location constraint prototype loss fuzzy c-means CICIDS2017 CICDDoS2019

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High-temperature corrosion of sintered RE_(2)Si_(2)O_(7)(RE=Yb and Ho)environmental barrier coating materials by volcanic ash

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International Journal of Minerals,Metallurgy and Materials 2024年第7期31卷 1628-1638页

作者： Ayahisa Okawa son thanh nguyen Tadachika Nakayama Thi-Mai-Dung Do Hisayuki Suematsu Shu Yin Takuya Hasegawa Tsuneo Suzuki Takashi Goto Koichi Niihara Institute of Multidisciplinary Research for Advanced Materials Tohoku UniversitySendai 980-8577Japan Department of Creative Engineering National Institute of TechnologyKushiro 084-0916Japan Extreme Energy-Density Research Institute Nagaoka University of TechnologyNagaoka 940-2188Japan Advanced Institute for Materials Research(WPI-AIMR) Tohoku UniversitySendai 980-8577Japan

Rare-earth silicates are promising environmental barrier coatings(EBCs)that can protect SiC_(f)/Si C_(m)substrates in next-genera tion gas turbine blades.Notably,RE_(2)Si_(2)O_(7)(RE=Yb and Ho)shows potential as an EBC due to its coefficient of thermal expansion(CTE)compatible with substrates and high resistance to water vapor corrosion.The target operating temperature for next-generation tur bine blades is 1400°C.Corrosion is inevitable during adhesion to molten volcanic ash,and thus,understanding the corrosion behavior o the material is crucial to its reliability.This study investigates the high-temperature corrosion behavior of sintered RE_(2)Si_(2)O_(7)(RE=Yb and Ho).Samples were prepared using a solid-state reaction and hot-press method.They were then exposed to volcanic ash at 1400°C for 224,and 48 h.After 48 h of exposure,volcanic ash did not react with Yb_(2)Si_(2)O_(7)but penetrated its interior,causing damage.Meanwhile Ho_(2)Si_(2)O_(7)was partially dissolved in the molten volcanic ash,forming a reaction zone that prevented volcanic ash melts from penetrating the interior.With increasing heat treatment time,the reaction zone expanded,and the thickness of the acicular apatite grains increased The Ca:Si ratios in the residual volcanic ash were mostly unchanged for Yb_(2)Si_(2)O_(7)but decreased considerably over time for Ho_(2)Si_(2)O_(7).Th Ca in volcanic ash was consumed and formed apatite,indicating that RE^(3+)ions with large ionic radii(Ho>Yb)easily precipitated apatit from the volcanic ash.

关键词： environmental barrier coating volcanic ash rare-earth disilicate corrosion

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Some Mean Convergence Theorems for the Maximum of Normed Double Sums of Banach Space Valued Random Elements

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Acta Mathematica Sinica,English Series 2024年第7期40卷 1727-1740页

作者： Andrew ROSALSKY Le Van thanh nguyen Thi Department of Statistics University of FloridaGainesvilleFL 32611-8545USA Department of Mathematics Vinh UniversityVinhNghe AnViet Nam THUY High School for Gifted Students Vinh UniversityVinhNghe AnViet Nam

In this correspondence,we establish mean convergence theorems for the maximum of normed double sums of Banach space valued random elements.Most of the results pertain to random elements which are M-dependent.We expand and improve a number of particular cases in the literature on mean convergence of random elements in Banach spaces.One of the main contributions of the paper is to simplify and improve a recent result of Li,Presnell,and Rosalsky[Journal of Mathematical Inequalities,16,117–126(2022)].A new maximal inequality for double sums of M-dependent random elements is proved which may be of independent interest.The sharpness of the results is illustrated by four examples.

关键词： Double sum mean convergence Rademacher type p Banach space Banach space valued random element M-dependent random elements

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Prevalence and risk factors associated with long COVID symptoms in children and adolescents in a southern province of Vietnam

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Asian Pacific Journal of Tropical Medicine 2024年第3期17卷 119-128,I0001,I0002页

作者： Huynh Ngoc Linh nguyen The Tan Le Thi Minh Thu nguyen Tu Loan nguyen Thi To Uyen Le thanh Thao Trang Truong thanh Nam Doan Hoang Phu Faculty of Medicine Ca Mau Medical CollegeCa Mau 98000Vietnam Ca Mau Obstetrics and Pediatrics Hospital Ca Mau 98000Vietnam Faculty of Basic Science and Public Health Dong Thap Medical CollegeDong Thap 81000Vietnam Graduate University of Sciences and Technology Vietnam Academy of Science and TechnologyHa Noi 10000Vietnam Community Public Health Research Program School of Public HealthWalailak UniversityNakhon Si Thammarat 80160Thailand Faculty Public Health Can Tho University of Medicine and PharmacyCan Tho City 94000Vietnam Doctoral Program in Health Sciences College of Graduate StudiesWalailak UniversityNakhon Si Thammarat 80160Thailand

Objective:To investigate the prevalence and risk factors associated with long COVID symptoms among children and adolescents who have recovered from COVID-19.Methods:This study applied a cross-sectional approach within community settings in a southern province of Vietnam.A structured questionnaire featuring socio-demographic information and common long COVID symptoms was employed.Phi correlation coefficients assessed associations among pairs of long COVID symptoms.Additionally,multivariable logistic regression models were performed to investigate the risk factors of long COVID in recovered COVID-19 children and adolescents.Results:Among 422 participants,39.3%reported long COVID symptoms,with a prevalence of 45.2%(SD=0.5)in children and 22.2%(SD=0.4)in adolescents.Common symptoms reported were cough 34.6%(SD=0.5),fatigue 20.6%(SD=0.4),shortness of breath 10.9%(SD=0.3),and lack of appetite 6.6%(SD=0.3).Concerning risk factors of long COVID,a higher risk was observed among demographic groups,including girls(OR 1.25,95%CI 1.15-1.37;P<0.001,reference:boys),children compared to adolescents(OR 1.24,95%CI 1.12-1.37;P<0.001),overweight individuals(OR 1.14,95%CI 1.02-1.27;P=0.018,reference:healthy weight),and participants without any COVID-19 vaccination(OR 1.36,95%CI 1.20-1.54;P<0.001),or have received only one single dose(OR 1.35,95%CI 1.10-1.64;P=0.004)compared to those who have received two doses.Besides,patients with a COVID-19 treatment duration exceeding two weeks also had a higher risk of long COVID(OR 1.32,95%CI 1.09-1.60;P=0.003)than those who recovered less than seven days.Conclusions:The insights from this study provide crucial guidance for predicting the factors associated with the occurrence of long COVID in pediatric patients,contributing to strategic interventions aimed at mitigating the long COVID risks among children and adolescents in Vietnam.

关键词： Long COVID Prevalence Risk factors Children Adolescent Vietnam

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