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Spatiotemporal Trend Analysis of Precipitation Extremes in Ho Chi Minh City, Vietnam During 1980–2017

International Journal of Disaster Risk Science 2021年第1期12卷 131-146页

作者： nguyen trong quan Dao nguyen Khoi nguyen Xuan Hoan nguyen Ky Phung Thanh Duc Dang Faculty of Environmental and Food Engineering Nguyen Tat Thanh UniversityHo Chi Minh City 700000Vietnam Faculty of Environment University of ScienceHo Chi Minh City 700000Vietnam Vietnam National University Ho Chi Minh City 700000Vietnam Ho Chi Minh City University of Food Industry Ho Chi Minh City 700000Vietnam Institute for Computational Science and Technology Ho Chi Minh City 700000Vietnam Engineering Systems and Design Pillar Singapore University of Technology and DesignTampines 487372Singapore

In this study,the spatiotemporal variability of trends in extreme precipitation events in Ho Chi Minh City during the period 1980–2017 was analyzed based on several core extreme precipitation indices(Rx1 day,Rx5 day,CDD,CWD,R20 mm,R25 mm,R95 p,and SDII).The nonparametric Mann–Kendall and Sen’s slope methods were used to compute the statistical strength,stability,and magnitude of trends in annual rainfall,as well as the extreme precipitation *** found that 64%of the stations had statistically significant upward trends in yearly rainfall,with high magnitudes frequently observed in the northern and southern regions of the *** the extreme precipitation indices,only SDII and R25 mm showed dominantly significant ***,there were increasing trends in the frequency and duration at the southern and central regions of the city during the study ***,El Ni?o-Southern Oscillation and Pacific Decadal Oscillation positively correlated with the duration and negatively correlated with the intensity and frequency of extreme ***,water management plans should be adjusted appropriately to reduce the severe impacts of precipitation extremes on communities and ecosystems.

关键词： Spatiotemporal trend Extreme precipitation Extreme precipitation indices Ho Chi Minh City

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基于FUNWAVE-TVD波浪模型的黄河三角洲近岸波浪变形与破碎过程数值模拟

基于FUNWAVE-TVD波浪模型的黄河三角洲近岸波浪变形与破碎过程数...

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作者： nguyen trong quan 中国科学院大学(中国科学院烟台海岸带研究所)

学位级别：硕士

近岸海洋包括河口、浅海区和陆架,对于沿海地区的生活安定、经济活动、交通和居住功能至关重要。然而,海岸带环境正面临着气候变化和人类活动带来的巨大压力,导致海岸线侵蚀、潮汐淹水、海岸线形态变化等风险。因此,对沿海系统行为的全... 详细信息

近岸海洋包括河口、浅海区和陆架,对于沿海地区的生活安定、经济活动、交通和居住功能至关重要。然而,海岸带环境正面临着气候变化和人类活动带来的巨大压力,导致海岸线侵蚀、潮汐淹水、海岸线形态变化等风险。因此,对沿海系统行为的全面研究为政府确保沿海地区的价值提供支撑起到重要作用。此外,沿海地区的水动力数值模拟已被证明可以有效地模拟复杂的物理过程,例如冲浪区的波浪破碎、冲流带波浪的升降。本研究采用数值模拟方法来分析近岸流体动力学,特别关注波浪破碎过程。本研究旨在加深黄河三角洲近岸波浪破碎过程的基本机制以及主要因素对波浪模拟性能的影响方面的理解。这些研究结果为实际应用中选择合适的数值模型提供了指导,并有助于近岸区域水动力的综合评价。研究区黄河三角洲位于渤海湾和莱州湾之间,近年来因其沿岸的风险和灾害而受到广泛关注。然而,对该地区近岸水动力和波流相互作用的数值模拟研究十分有限。本研究为校准和验证数值波浪模型提供了案例研究框架,重点关注初始边界条件和模型参数化。所提出的程序有望在今后应用于类似三角洲地区波浪破碎过程的研究。本文研究了所选数值模式(FUNWAVE-TVD)的重要模型参数(如计算网格大小和波浪破碎准则)和物理参数(如能量谱和波相干度),以了解它们对黄河三角洲近岸地区波浪特征和波浪破碎过程非均匀性的贡献。FUNWAVE-TVD是一种相位解析Boussinesq波浪模型,用于模拟具有理想相干效应的波浪。水深和地形数据来自中国海图和欧盟哥白尼海洋服务信息。在模型配置完成之后,研究了不同程度的波浪相干性和能量谱离散化的统计数据(例如,均方根和有效波高、最大跨岸流速和最大涡度)在该区域内的空间分布情况。因此,利用经过校准和验证参数后的数值模型,研究了黄河三角洲近岸的波浪破碎情况。本研究获得的结果表明,波浪统计数据的空间分布的复杂性及近岸变化的大小与波浪的相干性程度成正比。相干性较高的波浪在近岸方向表现出更复杂的变化性和更强的波动性。通过比较有无相干性影响的模拟结果,可以看出黄河三角洲地区地形变化对波高的影响。当波浪向破碎带移动时,跨岸流速下降,而涡度增加,表明剪切波的幅度较大。当波浪到达浅水区和海岸线时,可以观察到破碎特征。因此,模拟波在到达水深小于5米(2米)时分散了60%以上(80%)的能量,当在海岸线破碎时完全耗散。

关键词：波浪破碎波浪相干性黄河三角洲近岸 FUNWAVE-TVD

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Assessing the Vulnerability of Agricultural Production Activities in the Coastal Area of Thua Thien Hue Province, Vietnam by GIS Analysis Tools

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Journal of Geoscience and Environment Protection 2019年第5期7卷 116-130页

作者： nguyen Hoang Son Dao Dinh Cham Phan Anh Hang nguyen trong quan nguyen Thanh Hoan University of Education Hue University Hue Vietnam Institute of Geography Vietnam Academy of Science and Technology Hanoi Vietnam Graduate University of Science and Technology Vietnam Academy of Science and Technology Hanoi Vietnam University of Science Hue University Hue Vietnam

Using Geography Information System (GIS) tools and remote sensing data in assessing the level of vulnerability of agricultural production activities in the coastal area has become more efficient in the recent years. This research has identified the sensitivity index (S) (including the traffic access index;the impact of residential areas;the impacts of industrial zones;the community dependence level), exposure index (E) (the sea level rises to 2100;the temperature change to 2100), the adaptable capacity index (AC) (slope;morphology), thereby synthesizing the vulnerability index (V). Based on the indexes to calculate vulnerability, the high to very high vulnerability area is 37,081.44 ha, accounting for 68.09%;the average vulnerability level is 15,286.49 ha, accounting for 28.07%;the low to very low vulnerability level with an area is 2087.82 ha, accounting for 3.84% of the total area. With a high and very high vulnerability accounting for 68.09%, there will be great influences on the lives of resident in the area, especially agricultural production.

关键词： Vulnerability Indexes GIS Tools Agricultural Production Activity Coastal Areas

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Fresh and hardened properties of high-performance fiber-reinforced concrete containing fly ash and rice husk ash:Influence of fiber type and content

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Frontiers of Structural and Civil Engineering 2022年第12期16卷 1621-1632页

作者： nguyen-trong HO Viet Quoc DANG Minh-Hieu nguyen Chao-Lung HWANG trong-Phuoc HUYNH Faculty of Civil Engineering VSB-Technical University of OstravaOstrava-Poruba 70800Czech Republic Faculty of Bridge and Road Construction Mientrung University of Civil Engineering(MUCE)Tuy Hoa City 56100Vietnam Vinh Long Department of Construction Vinh Long City 85000Vietnam Taiwan Building Technology Center Taiwan University of Science and TechnologyTaipei 10607China Faculty of Civil Engineering College of EngineeringCan Tho UniversityCan Tho City 94000Vietnam

Although fibers are used only infrequently as an additive in concrete in the construction industry,fiberenhanced concrete is known to provide a wide range of advantages over conventional *** main objective of this study was to investigate the influences of fiber type and content on the mechanical properties and durability of highperformance fiber-reinforced concrete(HPFRC)designed using a novel densified mixture design algorithm with fly ash and rice husk *** types of fiber,including polypropylene(PP)fiber,steel fiber(SF),and hybrid fiber(HF),were *** on the results,the inclusion of fibers decreased HPFRC flowability,regardless of fiber *** the compressive strength of HPFRC with 1.6%PP fiber content was 11.2%below that of the reference HPFRC specimen at 91 d of curing age,the 91-d compressive strengths of both SF and HF-enhanced HPFRC specimens were significantly better than that of the reference HPFRC ***,the HPFRC specimens incorporating SF and HF both exhibited better splitting tensile and flexural strengths as well as less drying shrinkage than the HPFRC specimens incorporating PP ***,the fiber-enhanced specimens,especially those with added SF,registered less surface electrical resistivity and greater vulnerability to chloride ion penetration than the reference HPFRC specimen.

关键词： high-performance fiber-reinforced concrete fly ash rice husk ash durability mechanical strength

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Shear strength model of the reinforced concrete beams with embedded through-section strengthening bars

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Frontiers of Structural and Civil Engineering 2022年第7期16卷 843-857页

作者： Linh Van Hong BUI Phuoc trong nguyen Faculty of Civil Engineering Ho Chi Minh City Open UniversityHo Chi Minh City 700000Vietnam

In this study,finite element(FE)analysis is utilized to investigate the shear capacity of reinforced concrete(RC)beams strengthened with embedded through-section(ETS)*** of critical variables on the beam shear strength,including the compressive strength of concrete,stiffness ratio between ETS bars and steel stirrups,and use of ETS strengthening system alone,are parametrically investigated.A promising method based on the bond mechanism between ETS strengthening and concrete is then proposed for predicting the shear resistance forces of the strengthened *** expression for the maximum bond stress of the ETS bars to concrete is *** new expression eliminates the difficulty in the search and selection of appropriate bond parameters from adhesion *** results obtained from the FE models and analytical models are validated by comparison with those measured from the ***,the model proposed in this study demonstrates better performance and more accuracy for prediction of the beam shear-carrying capacity than those of existing *** results obtained from this study can also serve researchers and engineers in selection of the proper shear strength models for design of ETS-strengthened RC beams.

关键词： embedded through-section strengthening fiber-reinforced polymer finite element shear strength model bond mechanism

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An Optimal Node Localization in WSN Based on Siege Whale Optimization Algorithm

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Computer Modeling in Engineering & Sciences 2024年第3期138卷 2201-2237页

作者： Thi-Kien Dao trong-The nguyen Fujian Provincial Key Laboratory of Big Data Mining and Applications Fujian University of TechnologyFuzhou350118China Multimedia Communication Lab University of Information TechnologyHo Chi Minh CityVietnam

Localization or positioning scheme in Wireless sensor networks (WSNs) is one of the most challenging andfundamental operations in various monitoring or tracking applications because the network deploys a large areaand allocates the acquired location information to unknown devices. The metaheuristic approach is one of themost advantageous ways to deal with this challenging issue and overcome the disadvantages of the traditionalmethods that often suffer from computational time problems and small network deployment scale. This studyproposes an enhanced whale optimization algorithm that is an advanced metaheuristic algorithm based on thesiege mechanism (SWOA) for node localization inWSN. The objective function is modeled while communicatingon localized nodes, considering variables like delay, path loss, energy, and received signal strength. The localizationapproach also assigns the discovered location data to unidentified devices with the modeled objective functionby applying the SWOA algorithm. The experimental analysis is carried out to demonstrate the efficiency of thedesigned localization scheme in terms of various metrics, e.g., localization errors rate, converges rate, and executedtime. Compared experimental-result shows that theSWOA offers the applicability of the developed model forWSNto perform the localization scheme with excellent quality. Significantly, the error and convergence values achievedby the SWOA are less location error, faster in convergence and executed time than the others compared to at least areduced 1.5% to 4.7% error rate, and quicker by at least 4%and 2% in convergence and executed time, respectivelyfor the experimental scenarios.

关键词： Node localization whale optimization algorithm wireless sensor networks siege whale optimization algorithm optimization

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ON BOUNDEDNESS PROPERTY OF SINGULAR INTEGRAL OPERATORS ASSOCIATED TO A SCHRODINGER OPERATOR IN A GENERALIZED MORREY SPACE AND APPLICATIONS

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Acta Mathematica Scientia 2020年第5期40卷 1171-1184页

作者： Xuan Truong LE Thanh Nhan nguyen Ngoc trong nguyen Division of Computational Mathematics and Engineering Institute for Computational ScienceTon Due Thang UniversityHo Chi Minh CityVietnam Faculty of Mathematics and Statistics Ton Due Thang UniversityHo Chi Minh CityVietnam Department of Mathematics Ho Chi Minh City University of EducationHo Chi Minh CityVietnam Department of Primary Education Ho Chi Minh City University of EducationHo Chi Minh CityVietnam

In this paper,we provide the boundedness property of the Riesz transforms associated to the Schrodinger operator■=-Δ+V in a new weighted Morrey space which is the generalized version of many previous Morrey type *** additional potential V considered in this paper is a non-negative function satisfying the suitable reverse Holder's *** results are new and general in many cases of *** an application of the boundedness property of these singular integral operators,we obtain some regularity results of solutions to Schrodinger equations in the new Morrey space.

关键词： weighted Morrey spaces Schodinger operator riesz transforms Regularity estima tes

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Forecasting measured responses of structures using temporal deep learning and dual attention

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Frontiers of Structural and Civil Engineering 2024年第6期18卷 832-850页

作者： Viet-Hung DANG trong-Phu nguyen Thi-Lien PHAM Huan X.nguyen Department of Structural Mechanics Hanoi University of Civil EngineeringHanoi 11600Vietnam Faculty of Applied Science University of Economics-Technology for IndustriesHanoi 11600Vietnam London Digital Twin Research Centre Faculty of Science and TechnologyMiddlesex UniversityLondon NW44BTUK International School Vietnam National UniversityHanoi 11600Vietnam

The objective of this study is to develop a novel and efficient model for forecasting the nonlinear behavior of structures in response to time-varying random *** key idea is to design a deep learning architecture to leverage the relationships,between external excitations and structure's vibration signals,and between historical values and future values,within multiple time-series *** proposed method consists of two main steps:the first step applies a global attention mechanism to combine multiple-measured time series and time-varying excitation into a weighted time series before feeding it to a temporal architecture;the second step utilizes a self-attention mechanism followed by a fully connected layer to predict multi-step future *** viability of the proposed method is demonstrated via two case studies involving synthetic data from a three-dimensional(3D)reinforced concrete structure and experimental data from an 18-story steel ***,comparison and robustness studies are carried out,showing that the proposed method outperforms conventional methods and maintains high performance in the presence of noise with an amplitude of less than 10%.

关键词： structural dynamic time-varying excitation deep learning signal processing response forecasting

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Enhancing Fire Detection Performance Based on Fine-Tuned YOLOv10

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Computers, Materials & Continua 2024年第11期81卷 2281-2298页

作者： trong Thua Huynh Hoang Thanh nguyen Du Thang Phu Faculty of Information Technology 2 Posts and Telecommunications Institute of Technology(PTIT)Ho Chi Minh City700000Vietnam

In recent years,early detection and warning of fires have posed a significant challenge to environmental protection and human *** learning models such as Faster R-CNN(Faster Region based Convolutional Neural Network),YOLO(You Only Look Once),and their variants have demonstrated superiority in quickly detecting objects from images and videos,creating new opportunities to enhance automatic and efficient fire *** YOLO model,especially newer versions like YOLOv10,stands out for its fast processing capability,making it suitable for low-latency ***,when applied to real-world datasets,the accuracy of fire prediction is still not *** study improves the accuracy of YOLOv10 for real-time applications through model fine-tuning techniques and data *** core work of the research involves creating a diverse fire image dataset specifically suited for fire detection applications in buildings and factories,freezing the initial layers of the model to retain general features learned from the dataset by applying the Squeeze and Excitation attention mechanism and employing the Stochastic Gradient Descent(SGD)with a momentum optimization algorithm to enhance accuracy while ensuring real-time fire *** results demonstrate the effectiveness of the proposed fire prediction approach,where the YOLOv10 small model exhibits the best balance compared to other YOLO family models such as nano,medium,and ***,the study provides an experimental evaluation to highlight the effectiveness of model fine-tuning compared to the YOLOv10 baseline,YOLOv8 and Faster R-CNN based on two criteria:accuracy and prediction time.

关键词： Fire detection accuracy prediction time fine-tuning real-time YOLOv10 Faster R-CNN

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Determination of Helmert transformation parameters for continuous GNSS networks:a case study of the Géoazur GNSS network

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Geo-Spatial Information Science 2023年第1期26卷 125-138页

作者： Dinh trong Tran Jean-Mathieu Nocquet Ngoc Dung Luong Dinh Huy nguyen Department of Geodesy and Geomatics Engineering Hanoi University of Civil EngineeringHanoiVietnam UniversitéCôte d’Azur CNRSObservatoire de la Côte d’AzurIRDValbonneFrance

In this paper,we propose an approach to determine seven parameters of the Helmert transfor-mation by transforming the coordinates of a continuous GNSS network from the World Geodetic System 1984(WGS84)to the International Terrestrial Reference *** includes(1)convert-ing the coordinates of common points from the global coordinate system to the local coordinate system,(2)identifying and eliminating outliers by the Dikin estimator,and(3)estimating seven parameters of the Helmert transformation by least squares(LS)estimation with the“clean”data(*** removed).Herein,the local coordinate system provides a platform to separate points’horizontal and vertical ***,the Dikin estimator identifies and eliminates outliers in the horizontal or vertical component *** is significant because common points in a continuous GNSS network may contain *** proposed approach is tested with the Géoazur GNSS network with the results showing that the Dikin estimator detects outliers at 6 out of 18 common points,among which three points are found with outliers in the vertical compo-nent ***,instead of eliminating all coordinate components of these six common points,we only eliminate all coordinate components of three common points and only the vertical component of another three common ***,the classical LS estimation is applied to“clean”data to estimate seven parameters of the Helmert transformation with a significant accuracy *** Dikin estimator’s results are compared to those of other robust estimators of Huber and Theil-Sen,which shows that the Dikin estimator performs ***,the weighted total least-squares estimation is implemented to assess the accuracy of the LS estimation with the same *** inter-comparison of the seven estimated parameters and their standard deviations shows a small difference at a few per million levels(E-6).

关键词： Continuous GNSS tectonic geodesy Dikin estimation Helmert transformation

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