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Numerical investigation of circle defining curve for two-dimensional problem with general boundaries using the scaled boundary finite element method

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Frontiers of Structural and Civil Engineering 2019年第1期13卷 92-102页

作者： Chung nguyen VAN Department of Civil Engineering Faculty of EngineeringChulalongkorn UniversityThailand Faculty of Civil Engineering Ho Chi Minh City of Technology and EducationVietNam

The scaled boundary finite element method (SBFEM)is applied to the static analysis of two dimensional elasticity problem,boundary value problems domain with the domain completely described by a circular defining curve. The scaled boundary finite element equations is formulated within a general framework integrating the influence of the distributed body force,general boundary conditions,and bounded and unbounded *** paper investigates the possibility of using exact geometry to form the exact description of the circular defining curve and the standard finite element shape function to approximate the defining *** linear elasticity problems are presented to verify the proposed method with the analytical *** examples show the accuracy and efficiency of the proposed method,and the performance is found to be better than using standard linear element for the approximation defining curve on the scaled boundary method.

关键词： exact geometry circular defining curve general boundaries SBFEM

New Results on H_(∞) Control for Nonlinear Conformable Fractional Order Systems

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Journal of Systems Science & Complexity 2021年第1期34卷 140-156页

作者： MAI Viet Thuan nguyen Thi Huyen Thu nguyen Huu Sau nguyen Thi Thanh Huyen Department for Management of Science and Technology Development Ton Duc Thang UniversityHo Chi Minh CityVietnam Faculty of Mathematics and Statistics Ton Duc Thang UniversityHo Chi Minh CityVietnam Faculty of General Science Hanoi University of Natural Resources and EnvironmentHanoiVietnam Faculty of Fundamental Science Hanoi University of IndustryHa NoiVietnam Department of Mathematics and Informatics Thainguyen University of SciencesThainguyenVietnam

This paper deals with H_(∞) control problem for nonlinear conformable fractional order systems. The authors first derive new sufficient condition for exponential stability of nonlinear conformable fractional order systems based on Lyapunov-like function method for conformable fractional order systems and linear matrix inequalities(LMIs) approach. Then, by introducing a new concepts of H_(∞) control problem for nonlinear conformable fractional order systems, the authors study H_(∞) performance analysis and H_(∞) state feedback controller design problems for the considered systems. In terms of LMIs, a sufficient condition is proposed to ensure the nonlinear conformable fractional order systems are not only exponentially stable, but also satisfy H_(∞) performance γ. An explicit expression for state feedback controllers is also designed to make the closed-loop system is exponentially stable with H_∞performance γ. Finally, numerical examples are given to illustrate the validity and effectiveness of the proposed results.

关键词： Conformable fractional-order H_(∞)control problems H_(∞)performance analysis linear matrix inequalities nonlinear systems

An analytical model for cross-Kerr nonlinearity in a four-level N-type atomic system with Doppler broadening

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Chinese Physics B 2022年第2期31卷 314-319页

作者： Dinh Xuan Khoa nguyen Huy Bang nguyen Le Thuy An nguyen Van Phu Le Van Doai Vinh University 182 Le Duan StreetVinh CityVietna

We present an analytical model for cross-Kerr nonlinear coefficient in a four-level N-type atomic medium under Doppler *** model is applied to87 Rb atoms to analyze the dependence of the cross-Kerr nonlinear coefficient on the external light field and the temperature of atomic *** analysis shows that in the absence of electromagnetically induced transparency(EIT)the cross-Kerr nonlinear coefficient is zero,but it is significantly enhanced when the EIT is *** means that the cross-Kerr effect can be turned on/off when the external light field is on or ***,the amplitude and the sign of the cross-Kerr nonlinear coefficient are easily changed according to the intensity and frequency of the external light *** amplitude of the cross-Kerr nonlinear coefficient remarkably decreases when the temperature of atomic medium *** analytical model can be convenient to fit experimental observations and applied to photonic devices.

关键词： electromagnetically induced transparency Kerr nonlinear effect Doppler effect

Fuzzy MCDM Model for Selection of Infectious Waste Management Contractors

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Computers, Materials & Continua 2022年第8期72卷 2191-2202页

作者： nguyen Van Thanh nguyen Hoang Hai nguyen Thi Kim Lan Faculty of Commerce Van Lang UniversityHo Chi Minh CityVietnam International Education Institute Van Lang UniversityHo Chi Minh CityVietnam

Healthcare supply chains are under pressure to drive down costs because of digital business,shifting customer needs and new *** waste generated from medical facilities includes medical activities and daily-life activities of patients and their family *** to statistics of the Department of Health EnvironmentalManagement,Vietnam currently has more than 13,500 medical facilities,including hospitals from central to provincial and district levels and private hospitals and medical *** medicine generates about 590 tons of medical waste/day and is estimated to be about 800 tons/*** waste includes ordinary medical waste and hazardous medical waste;in which ordinary medical waste accounts for about 80%–90%,only about 10%–20%is hazardous medical waste including infectious waste and non-infectious hazardous *** is an environmental and occupational health issue that needs attention in developing countries like *** large amounts of medical waste to ensure environmental and personal hygiene,doing so inefficiently creates potential hazards to the environment and increases operating ***,hospitals lack objective criteria and methods to evaluate and select the most optimal infectious medical waste,relying instead on their own subjective assessment and prior ***,the author proposed a fuzzy multicriteria decision making(MCDM)model including Fuzzy Analytic hierarchy process(FAHP)and the Weighted Aggregated Sum-Product Assessment(WASPAS)for infectious medical waste contractors’selection in this *** proposed Fuzzy MCDM method is in-tended to provide a more efficient,accurate method in the selection of infectious medical waste contractors than subjective assessment methods,thus reduce potential risks to *** results of this study can be applied to evaluate and select contractors in other industries.

关键词： MCDM model fuzzy theory fuzzy AHP WASPAS medical waste contractors

Parameters Effecting on Head Brown Rice Recovery and Energy Consumption of Rubber Roll and Stone Disk Dehusking

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Journal of Agricultural Science and Technology(B) 2015年第6期5卷 383-388页

作者： nguyen Duc Canh nguyen Thanh Nghi nguyen Van hung Center for Agricultural Energy and Machinery Nong Lam University Ho Chi Minh City 700000 Vietnam Crop and Environmental Science Division International Rice Research Institute Metro Manila 1301 Philippines

Application of improper methods on rice processing affects rice quality and head rice recovery. In Vietnam, paddy with different moisture contents （from 13% to 17%） is dehusked by both rubber roll and stone disk. Thus, objective of this research was to evaluate the technical and economic aspects of the two methods. Optimization was conducted with 20 experiments for input factors （moisture content） and output factors （head brown rice recovery, specific energy consumption）. Besides, other factors were also monitored, such as the gap between the two disks, speed of disk and roll, and pressure of rubber roll on paddy. Test results showed that the maximum value of head brown rice （77.4%） and the minimum value of specific energy consumption （0.66 kWh/ton） corresponding to moisture content of paddy of 13.7% for stone disk dehusker. At similar moisture content （13.7%）, head brown rice recovery and specific energy consumption were 77.2% and 1.04 kWh/ton for rubber roll dehusker, respectively. As the result, specific energy consumption of rubber roll dehusker was higher than that of stone disk dehusker, corresponding to the higher dehusking efficiency.

关键词： Paddy moisture content rubber roll dehusker stone disk dehusker head mill rice recovery energy consumption.

Orange G degradation by heterogeneous peroxymonosulfate activation based on magnetic MnFe_(2)O_(4)/α-MnO_(2) hybrid

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Journal of Environmental Sciences 2023年第2期124卷 379-396页

作者： Le Thi Thao To Van nguyen Van Quy nguyen Ngoc Man Phan Ki Jae Kim nguyen Nhat Huy nguyen Trung Dung Faculty of Physical and Chemical Engineering Le Quy Don Technical UniversityHanoi 100000Vietnam Department of Energy Engineering Konkuk UniversitySeoul 05029Korea School of Chemical Engineering College of EngineeringSungkyunkwan UniversityJangan-guSuwon 16419Korea Faculty of Environment and Natural Resources Ho Chi Minh City University of Technology(HCMUT)Ho Chi Minh City 700000Vietnam Vietnam National University Ho Chi Minh City Linh Trung WardThu Duc CityHo Chi Minh City 700000Vietnam

Wastewater containing an azo dye Orange G(OG)causes massive environmental pollution,thus it is critical to develop a highly effective,environmental-friendly,and reusable catalyst in peroxymonosulfate(PMS)activation for OG *** this work,we successfully applied a magnetic MnFe_(2)O_(4)/α-MnO_(2) hybrid fabricated by a simple hydrothermal method for OG removal in *** characteristics of the hybrid were investigated by Xray diffraction,scanning electron microscopy,energy-dispersive X-ray spectroscopy,Fourier transform infrared spectroscopy,Brunauer–Emmett–Teller method,vibrating sample magnetometry,electron paramagnetic resonance,thermogravimetric analysis,and X-ray photoelectron *** effects of operational parameters(i.e.,catalytic system,catalytic dose,solution pH,and temperature)were *** results exhibited that 96.8% of OG degradation was obtained with MnFe_(2)O_(4)/α-MnO2(1:9)/PMS system in 30 min regardless of solution pH ***,the possible reaction mechanism of the coupling system was proposed,and the degradation intermediates of OG were identified by mass *** radical quenching experiments and EPR tests demonstrated that SO_(4)•̶,O_(2)•̶,and 1O2 were the primary reactive oxygen species responsible for the OG *** hybrid also displayed unusual stability with less than 30%loss in the OG removal after four sequential ***,magnetic MnFe2O4/α-MnO2 hybrid could be used as a high potential activator of PMS to remove orange G and maybe other dyes from wastewater.

关键词： MnFe_(2)O_(4)/α-MnO_(2) Peroxymonosulfate Orange G Catalytic degradation Reusability

STABILITY ANALYSIS OF A COMPUTER VIRUS PROPAGATION MODEL WITH ANTIDOTE IN VULNERABLE SYSTEM

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Acta Mathematica Scientia 2016年第1期36卷 49-61页

作者： nguyen Huu KHANH nguyen Bich HUY Department of Mathematics College of Natural SciencesCan Tho University Departmet of Mathematics Ho Chi Minh University of Education

We study a proposed model describing the propagation of computer virus in the network with antidote in vulnerable system. Mathematical analysis shows that dynamics of the spread of computer viruses is determined by the threshold Ro. If Ro 〈 1, the virusfree equilibrium is globally asymptotically stable, and if R0 〉 1, the endemic equilibrium is globally asymptotically stable. Lyapunov functional method as well as geometric approach are used for proving the global stability of equilibria. A numerical investigation is carried out to confirm the analytical results. Through parameter analysis, some effective strategies for eliminating viruses are suggested.

关键词： computer virus virus-free equilibrium endemic equilibrium global stability antidote

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

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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

Rudder Roll Damping Autopilot Using Dual Extended Kalman Filter–Trained Neural Networks for Ships in Waves

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Journal of Marine Science and Application 2019年第4期18卷 510-521页

作者： Yuanyuan Wang hung Duc nguyen National Center for Maritime Engineering and Hydrodynamics Australian Maritime College University of Tasmania

The roll motions of ships advancing in heavy seas have severe impacts on the safety of crews,vessels,and cargoes;thus,it must be *** study presents the design of a rudder roll damping autopilot by utilizing the dual extended Kalman filter(DEKF)trained radial basis function neural networks(RBFNN)for the surface *** autopilot system constitutes the roll reduction controller and the yaw motion controller implemented in *** analyzing the advantages of the DEKF-trained RBFNN control method theoretically,the ship’s nonlinear model with environmental disturbances was employed to verify the performance of the proposed stabilization *** sailing scenarios were conducted to investigate the motion responses of the ship in *** results demonstrate that the DEKF RBFNN based control system is efficient and practical in reducing roll motions and following the path for the ship sailing in waves only through rudder actions.

关键词： Rudder roll damping Autopilot Radial basis function Neural networks Dual extended Kalman filter training Intelligent control Path following Advancing in waves