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Novel Time Series Bagging Based Hybrid Models for Predicting Historical Water Levels in the Mekong Delta Region, Vietnam

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Computer Modeling in Engineering & Sciences 2022年第6期131卷 1431-1449页

作者： nguyen Thanh Hoan nguyen Van Dung Ho Le Thu Hoa Thuy Quynh Nadhir Al-Ansari Tran Van Phong Phan trong Trinh Dam Duc nguyen Hiep Van Le Hanh Bich Thi nguyen Mahdis Amiri Indra Prakash Binh Thai Pham Institute of Geography Vietnam Academy of Science and TechnologyHanoi10000Viet Nam Department of Civil Environmental and Natural Resources EngineeringLulea University of TechnologyLulea97187Sweden Institute of Geological Sciences Vietnam Academy of Science and Technology(VAST)Dong DaHanoi10000Viet Nam University of Transport Technology Thanh XuanHa Noi10000Viet Nam Department of Watershed&Arid Zone Management Gorgan University of Agricultural Sciences&Natural ResourcesGorgan***Iran DDG(R)Geological Survey of India Gandhinagar382010India

Water level predictions in the river,lake and delta play an important role in flood *** year Mekong River delta of Vietnam is experiencing flood due to heavy monsoon rains and high *** subsidence may also aggravate flooding problems in this ***,accurate predictions of water levels in this region are very important to forewarn the people and authorities for taking timely adequate remedial measures to prevent losses of life and *** are so many methods available to predict the water levels based on historical data but nowadays Machine Learning(ML)methods are considered the best tool for accurate *** this study,we have used surface water level data of 18 water level measurement stations of the Mekong River delta from 2000 to 2018 to build novel time-series Bagging based hybrid ML models namely:Bagging(RF),Bagging(SOM)and Bagging(M5P)to predict historical water levels in the study *** of the Bagging-based hybrid models were compared with Reduced Error Pruning Trees(REPT),which is a benchmark ML *** data of 19 years period was divided into 70:30 ratio for the *** data of the period 1/2000 to 5/2013(which is about 70%of total data)was used for the training and for the period 5/2013 to 12/2018(which is about 30%of total data)was used for testing(validating)the *** of the models was evaluated using standard statistical measures:Coefficient of Determination(R2),Root Mean Square Error(RMSE)and Mean Absolute Error(MAE).Results show that the performance of all the developed models is good(R2>0.9)for the prediction of water levels in the study ***,the Bagging-based hybrid models are slightly better than another model such as ***,these Bagging-based hybrid time series models can be used for predicting water levels at Mekong data.

关键词： Computational techniques bagging water level time series algorithms

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Some Factors Affected on Structure, Mechanical of Ni Bulk

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Advances in Materials Physics and Chemistry 2018年第4期8卷 177-192页

作者： nguyen trong Dung nguyen Chinh Cuong Faculty of Physics Hanoi National University of Education Hanoi Vietnam

The article examines the effect of atomic number, temperature and tempering time on microstructure and mechanical of Ni bulk by molecular dynamics simulation and deformation z-axis. Samples Ni with N = 4000, 5324, 6912, and 8788 atoms at 300 K, 6912 atoms at T = 1100, 900, 700, 500, 300 K and 6912 atoms at 900 K after different annealing time. The samples were incubated with the same heating rate . Combined with common neighborhood analysis method shown in sample is always existing four types structure: FCC, HCP, BCC, and Amor. In particular, structural units FCC, HCP and Amor always prevail and BCC are very small and appear only at 300, 500 K with 6912 atoms. When increasing atomic number, lowering temperature or increasing tempering time will facilitate crystallization process leading to increased FCC and HCP units number. The increasing FCC, HCP units number and additional appearance BCC structure led to change microstructure and mechanical of material: When increasing atom, lowering temperature and increasing incubation time lead to an increase in density of atoms that increase mechanical properties of the material.

关键词： Atoms Number Temperature Microstructure Mechanical Ni Bulk

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Facile biphasic catalytic process for conversion of monoterpenoids to tricyclic hydrocarbon biofuels

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Journal of Energy Chemistry 2020年第10期29卷 42-50页

作者： Shaoqu Xie trong HHuynh Peiyong Qin Tianwei Tan Hongfei Lin The Gene and Linda Voiland School of Chemical Engineering and Bioengineering Washington State UniversityPullmanWA 99164 National Energy Research and Development Center for Biorefinery Beijing University of Chemical TechnologyBeijing 100029China

Terpenoids have drawn much attention to scientists in synthesizing high-performance bio-jet fuels due to their ring structures,which feature potential high ***,a facile biphasic catalytic process has been developed for the production of high-density tricyclic hydrocarbon biofuels from a monoterpenoid,1,8-cineole,using sulfuric acid(H2SO4)as the homogeneous catalyst.A^100%conversion of 1,8-cineole and a>40%carbon yield of cyclic dimers were achieved at 100℃within two *** mechanism for the acid-catalyzed conversion of 1,8-cineole to cyclic hydrocarbon dimers were *** particular,the formation of the diene intermediates and the following dimerization of dienes was essential to synthesize tricyclic terpene *** biphasic catalytic process accelerated the deoxygenation rate and enabled the dimerization with the aid of organic solvent while controlling the reaction rates to avoid the formation of solid ***,this process also facilitated the product separation by organic solvent extraction while enabling easy recycle of the homogenous catalysts.

关键词： Cineole High-density biofuels Biphasic catalytic process Diels-Alder reaction Dehydration

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Adaptive control for an uncertain robotic manipulator with input saturations

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Control Theory and Technology 2016年第2期14卷 113-121页

作者： trong-Toan TRAN Shuzhi Sam GE Wei HE Center for Robotics and School of Automation Engineering University of Electronic Science and Technology of China (UESTC) Chengdu Sichuan 611731 China Department of Electrical and Computer Engineering National University of Singapore Singapore 117576 Faculty of Electronic Technology Industrial University of rio Chi Minh City Ho Chi Minh City Vietnam School of Automation and Electrical Engineering University of Science and Technology Beijing Beijing 100083 China

In this paper, we address the control problem of an uncertain robotic manipulator with input saturations, unknown input scalings and disturbances. For this purpose, a model reference adaptive control like （MRAC-like） is used to handle the input saturations. The model reference is input to state stable （ISS） and driven by the errors between the required control signals and input saturations. The uncertain parameters are dealt with by using linear-in-the-parameters property of robotic dynamics, while unknown input scalings and disturbances are handled by non-regressor based approach. Our design ensures that all the signals in the closed-loop system are bounded, and the tracking error converges to the compact set which depends on the predetermined bounds of the control inputs. Simulation on a planar elbow manipulator with two joints is provided to illustrate the effectiveness of the proposed controller.

关键词： Robotic manipulator adaptive control uncertain parameter input saturation trajectory tracking

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Facile Preparation, Characterization of Flexible Organic Solar Cells Using P3HT-MWCNTS Composite Photoactive Layer

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Journal of Materials Science and Chemical Engineering 2020年第10期8卷 1-10页

作者： Tran Si trong Khanh nguyen Phuong Hoai Nam nguyen Nang Dinh Advanced Research Group of Nano-Semiconducting Materials and Devices (ARGD) University of Engineering and Technology VNU in Hanoi Hanoi Vietnam

Multiwalled carbon nanotubes (MWCNTs) mixed in poly(3-hexylthiophene) (P3HT) were used as a photoactive layer for organic solar cells (OSC). The flexible OSCs of a structure of PET/rGO-P3HT/P3CT/PCBM/LiF-Al were prepared by spincoating. The UV-Vis absorption spectra of the photoactive films and current-voltage characteristics of the OSCs showed the advantage of the composite devices above the pristine-polymeric ones. Under illumination of light with a 100 mW/cm2-powerdensity, the photoelectrical conversion efficiency (PCE) of the OSCs with 3.0 wt% MWNCTs embedded in the photoactive layer possess a value as large as 2.35%. The obtained results suggest further useful applications of the flexible large-area solar cells.

关键词： P3HT-MWCNTs Composite Photovoltage UV-Vis Absorption Photoluminescence (PL) Quenching J-V Characteristics Photoelectrical Conversion Efficiency (PCE)

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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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Forest Change and Its Effect on Biomass in Yok Don National Park in Central Highlands of Vietnam Using Ground Data and Geospatial Techniques

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Advances in Remote Sensing 2015年第2期4卷 108-118页

作者： nguyen Viet Luong Ryutaro Tateishi nguyen Thanh Hoan To trong Tu Space Technology Institute Vietnam Academy of Science and Technology Hanoi Vietnam Center for Environmental Remote Sensing Chiba University Chiba Japan Institute of Geography Vietnam Academy of Science and Technology Hanoi Vietnam

This paper assesses the changes in forest cover in Yok Don National Park of Vietnam between 2004 and 2010, and the implications of such changes on the biomass stocks of this national park. Remote sensing and GIS tools along with the ground truth data collected from the field were employed for classifying the forest types of the study area from SPOT HRV satellite imagery for years 2004 and 2010. The total area considered in this study is 115.5 thousand ha. Five different categories of forests were identified. The results demonstrated that between 2004 and 2010, the Evergreen broad leaved rich quality forest decreased by 11.2 thousand ha (3.5 Mega tons of biomass) and the Dry open dipterocarps medium quality forest decreased by 15.3 thousand ha (2.5 Mega tons of biomass). In that time period, the Evergreen broad leaved medium quality forest increased by 3.2 thousand ha (0.8 Mega tons of biomass), the Evergreen broad leaved poor quality forest increased by 2.5 thousand ha (0.24 Mega tons of biomass), and the Dry open dipterocarps poor quality forest increased by 3.2 thousand ha (0.69 Mega tons of biomass). Total biomass of the study area decreased by 4.3 Mega tons.

关键词： Satellite Data SPOT HRV Land Cover Change Tropical Forest Biomass

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Identifying high-risk individuals for gastric cancer surveillance from western and eastern perspectives: Lessons to learn and possibility to develop an integrated approach for daily practice

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World Journal of Gastroenterology 2019年第27期25卷 3546-3562页

作者： Duc trong Quach Toru Hiyama Takuji Gotoda Department of Internal Medicine University of Medicine and Pharmacy at Hochiminh CityHo Chi Minh 70000Vietnam Health Service Center Hiroshima UniversityHigashihiroshima 739-8514Japan Division of Gastroenterology and Hepatology Department of MedicineNihon University School of MedicineTokyo 101-8309Japan

Current evidence shows that individuals with gastric dysplasia, severe and extensive gastric atrophy, extensive gastric intestinal metaplasia and the incomplete subtype of intestinal metaplasia are at high risk for gastric cancer(GC) development. There are several approaches to identifying these subjects,including noninvasive methods, esophagogastroduodenoscopy and *** main approach in Western countries is histology-based while that in Eastern countries with a high prevalence of GC is endoscopy-based. Regarding asymptomatic individuals, the key issues in selecting applicable approaches are the ability to reduce GC mortality and the cost-effectiveness of the approach. At present, population-based screening programs have only been applied in a few Asian countries with a high risk of GC. Pre-endoscopic risk assessment based on demographic and clinical features, such as ethnicity, age, gender, smoking and Helicobacter pylori status, is helpful for identifying subjects with high pre-test probability for a possibly cost-effective approach, especially in intermediate-and low-risk countries. Regarding symptomatic patients with indications for esophagogastroduodenoscopy, the importance of opportunistic screening should be emphasized. The combination of endoscopic and histological approaches should always be considered as endoscopy provides a real-time assessment of the patient’s risk level. In addition, imaging enhanced endoscopy(IEE) has been shown to facilitate targeted biopsies resulting in better correlation between endoscopic and histological findings. Currently, the use of IEE is recommended for endoscopic examinations, and the Operative Link for Gastric Intestinal Metaplasia or Operative Link on Gastritis Assessment grading systems are recommended for histological examinations whenever available. However,resource limitations are an important barrier in many regions worldwide. Thus,for an approach to be applicable in real-life practice, it should be not only

关键词： Gastric cancer Precancerous gastric lesions Dysplasia Gastric atrophy Chronic atrophic gastritis Intestinal metaplasia Surveillance Screening Costeffective

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GLOBALLY ATTRACTING SOLUTIONS TO IMPULSIVE FRACTIONAL DIFFERENTIAL INCLUSIONS OF SOBOLEV TYPE

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Acta Mathematica Scientia 2017年第5期37卷 1295-1318页

作者： Van Hien LE Dinh Ke TRAN trong Kinh CHU Department of Mathematics Hanoi National University of Education 136 Xuan ThuyCau GiayHanoiVietnam Department of Mathematics Hanoi Pedagogical University No.2VinhphucVietnam

We study a generalized Cauchy problem associated with a class of impulsive fractional differential inclusions of Sobolev type in Banach spaces. Our aim is to prove the existence of a compact set of globally attracting solutions to the problem in question. An application to fractional partial differential equations subject to impulsive effects is given to illustrate our results.

关键词： globally attracting solution impulsive condition nonlocal condition condensing map measure of non-compactness MNC-estimate

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Effects of NaOH Concentrations on Properties of the Thermal Power Plant Ashes-Bricks by Alkaline Activation

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Journal of Wuhan University of Technology(Materials Science) 2020年第1期35卷 131-139页

作者： Ngo Si-Huy Le Thi Thanh-Tam Huynh trong-Phuoc Department of Engineering and Technology Hong Duc UniversityNo.565Quang Trung StreetDong Ve WardThanh Hoa City 440000Viet Nam Department of Rural Technology College of Rural DevelopmentCan Tho UniversityCampus II3/2 StreetNinh Kieu DistrictCan Tho City 900000Viet Nam

The use of the thermal power plant ashes including fly ash(FA) and bottom ash(BA) for producing unfired building bricks(UBB) using sodium hydroxide(NaOH) solution as an alkaline activator was investigated. A low applied forming pressure of 0.5 MPa and various NaOH concentrations of 5, 8, 10, and 12 M were used for the preparation of brick samples with different solution-to-binder(S/B) ratios of 0.35 and 0.40. The bricks were subjected to various test programs with reflecting the effect of both NaOH concentrations and S/B ratios on the brick’s properties. The compressive strength, unit weight, ultrasonic pulse velocity, and thermal conductivity of bricks increased with increasing NaOH concentration, whereas the contrary trend was found with increasing S/B ratio. Also, the water absorption of bricks was observed to reduce with increasing NaOH concentration and decreasing S/B ratio. As the results, the combined utilization of both low forming pressure and coal power plant ashes can produce the UBBs with low unit weight, low heat conductivity, and acceptable strength and water absorption rate as stipulated by TCVN 6477-2016. Furthermore, the outcomes of chemical analysis and microstructure observation also demonstrate that a high concentration of the Na OH promoted the geopolymerization process. Notably, the use of NaOH solution of either 10 M or above is recommended for the production of UBBs, which are classified as grade M5.0 or higher.

关键词： unfired building brick fly ash bottom ash thermal power plant ashes sodium hydroxide solution low forming pressure

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