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Acta Mathematica Scientia 2022年第2期42卷 795-812页

作者： nguyen Xuan LINH duong Viet THONG Prasit CHOLAMJIAK Pham Anh TUAN Luong Van LONG Department of Mathematics Mathematics Falcuty of Information TechnologyNational University of Civil Engineering Division of Applied Mathematics Thu Dau Mot UniversityBinh Duong ProvinceVietnam School of Science University of PhayaoPhayao 56000Thailand Paculty of Mathematical Economics National Economics UniversityHanoi CityVietnam

In this work,we investigate a classical pseudomonotone and Lipschitz continuous variational inequality in the setting of Hilbert space,and present a projection-type approximation method for solving this *** method requires only to compute one projection onto the feasible set per iteration and without any linesearch procedure or additional projections as well as does not need to the prior knowledge of the Lipschitz constant and the sequentially weakly continuity of the variational inequality mapping.A strong convergence is established for the proposed method to a solution of a variational inequality problem under certain mild ***,we give some numerical experiments illustrating the performance of the proposed method for variational inequality problems.

关键词： Inertial method Tseng’s extragradient viscosity method variational inequality problem pseudomonotone mapping strong convergence

Chebyshev polynomial-based Ritz method for thermal buckling and free vibration behaviors of metal foam beams

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Applied Mathematics and Mechanics(English Edition) 2024年第5期45卷 891-910页

作者： N.D.nguyen T.N.nguyen Faculty of Civil Engineering Ho Chi Minh City University of Technology and EducationHo Chi Minh City 71309Viet Nam Faculty of Engineering and Technology Kien Giang UniversityChau Thanh 92000Viet Nam

This study presents the Chebyshev polynomials-based Ritz method to examine the thermal buckling and free vibration characteristics of metal foam *** analyses include three models for porosity distribution and two scenarios for thermal *** material properties are assessed under two conditions,i.e.,temperature dependence and temperature *** theoretical framework for the beams is based on the higher-order shear deformation theory,which incorporates shear deformations with higher-order *** governing equations are established from the Lagrange equations,and the beam displacement fields are approximated by the Chebyshev *** simulations are performed to evaluate the effects of thermal load,slenderness,boundary condition(BC),and porosity distribution on the buckling and vibration behaviors of metal foam *** findings highlight the significant influence of temperature-dependent(TD)material properties on metal foam beams'buckling and vibration responses.

关键词： Ritz method Chebyshev function buckling vibration metal foam beam higher-order beam theory(HOBT)

Transient response of doubly-curved bio-inspired composite shells resting on viscoelastic foundation subject to blast load using improved first-order shear theory and isogeometric approach

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Defence Technology（防务技术） 2024年第8期38卷 171-193页

作者： Thuy Tran Thi Thu Tu nguyen Anh Hue nguyen Thi Hong nguyen Thi School of Mechanical and Automotive Engineering Hanoi University of IndustryHanoiViet Nam Faculty of Technical Fundamental University of Transport TechnologyHanoiViet Nam Faculty of Mechanical Engineering Thuyloi University175 Tay SonDong DaHanoiViet Nam

Investigating natural-inspired applications is a perennially appealing subject for scientists. The current increase in the speed of natural-origin structure growth may be linked to their superior mechanical properties and environmental resilience. Biological composite structures with helicoidal schemes and designs have remarkable capacities to absorb impact energy and withstand damage. However, there is a dearth of extensive study on the influence of fiber redirection and reorientation inside the matrix of a helicoid structure on its mechanical performance and reactivity. The present study aimed to explore the static and transient responses of a bio-inspired helicoid laminated composite(B-iHLC) shell under the influence of an explosive load using an isomorphic method. The structural integrity of the shell is maintained by a viscoelastic basis known as the Pasternak foundation, which encompasses two coefficients of stiffness and one coefficient of damping. The equilibrium equations governing shell dynamics are obtained by using Hamilton's principle and including the modified first-order shear theory,therefore obviating the need to employ a shear correction factor. The paper's model and approach are validated by doing numerical comparisons with respected publications. The findings of this study may be used in the construction of military and civilian infrastructure in situations when the structure is subjected to severe stresses that might potentially result in catastrophic collapse. The findings of this paper serve as the foundation for several other issues, including geometric optimization and the dynamic response of similar mechanical structures.

关键词： Blast load Modified first-order shear theory Biological composite structures

Thermodynamic Simulation on the Change in Phase for Carburizing Process

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Computers, Materials & Continua 2021年第7期68卷 1129-1145页

作者： Anh Tuan Hoang Xuan Phuong nguyen Osamah Ibrahim Khalaf Thi Xuan Tran Minh Quang Chau Thi Minh Hao Dong duong Nam nguyen Ho Chi Minh city University of Technology(HUTECH) HoVietnam Ho Chi Minh city University of Transport Ho Chi Minh cityVietnam Al-Nahrain University Al-Nahrain Nanorenewable Energy Research CenterBaghdadIraq Hanoi University of Science and Technology HanoiVietnam Industrial University of Ho Chi Minh City(IUH) Ho Chi Minh cityVietnam Vietnam Maritime University HaiphongVietnam

The type of technology used to strengthen the surface structure of machine parts,typically by carbon-permeation,has made a great contribution to the mechanical engineering industry because of its outstanding advantages in corrosion resistance and enhanced mechanical and physical ***,carbon permeation is considered as an optimal method of heat treatment through the diffusion of carbon atoms into the surface of alloy *** study presented research results on the thermodynamic calculation and simulation of the carbon permeability *** Fick’s law,the paper calculated the distribution of carbon concentration in the alloy steel after it is absorbed from the surface into the internal of the *** the SYSWELD software,an analysis was performed on the carbon permeability process to determine the distribution of carbon concentrations in 20CrMo steel that was then followed by a detailed analysis of the microstructure of the sample post the carburizing *** to the calculation results,the surface carbon content was 0.9%and steadily decreased into the *** 3 hours,the depth of the absorbent layer was measured at 0.5 mm for both the cylindrical and cubic *** analyzing the phase,the distribution of martensite phases such as ferrite/pearlite and residual austenite was also determined after the carburizing process.

关键词： Carburizing process 20CrMo steel thermodynamic analysis microstructure formation carbon concentration

Effects of parental age on offspring growth and survival in both wild and domesticated strains of bighead catfish(Clarias macrocephalus Günther,1864)

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Aquaculture and Fisheries 2023年第2期8卷 141-147页

作者： Thuy Yen duong Thet Su Win Thi Ngoc Tran nguyen College of Aquaculture and Fisheries Can Tho UniversityCan Tho920000Viet Nam International Master Program in Aquaculture Course 4Can Tho UniversityCan Tho920000Viet Nam

Understanding the relationship between fish parental age and offspring performance over their life cycle is crucial for *** study investigates the effect of parental age for both 1-and 2-year-old fish on the growth and survival rates of their larval to grow-out stages for two wild and domesticated strains of bighead catfish(Clarias macrocephalus).Fish were sampled from the Vietnamese Mekong Delta where wild adult fish were collected from a conservation area in Ca Mau Province and domesticated fish were taken from a hatchery in Can *** offspring treatments of 1-and 2-year-old broodstock strains were reared for 3 successive periods:40 days for fingerling rearing in static tanks with water exchange,60 days for juveniles,and 90 days for grow-out in recirculating *** final weight of fish at 190 days varied from 96.7 to 144.7 *** growth of offspring was not affected by parental age(P>0.05),over the 3 rearing ***,the domesticated fish strain showed significantly better growth rates than the wild fish strain(P<0.05).Feed conversion ratios were comparable across fish *** rates did not differ at the fingerling(21.8%-36.4%)and juvenile(69.0%-73.3%)***,significant differences were found at the grow-out stage(69.3%-84.0%),with offspring from 2-year-old parents of both strains having greater survival ***,1-and 2-year-old fish appear to be suitable for bighead catfish breeders.

关键词： Parental age Clarias catfish Fish growth Strain evaluation Wild broodstock

A Chemical Reactor Network for Oxides of Nitrogen Emission Prediction in Gas Turbine Combustor

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Journal of Thermal Science 2014年第3期23卷 279-284页

作者： nguyen Thanh Hao Industrial University of HoChiMinh City

This study presents the use of a new chemical reactor network(CRN) model and non-uniform injectors to predict the NOx emission pollutant in gas turbine combustor. The CRN uses information from Computational Fluid Dynamics(CFD) combustion analysis with two injectors of CH4-air mixture. The injectors of CH4-air mixture have different lean equivalence ratio, and they control fuel flow to stabilize combustion and adjust combustor's equivalence ratio. Non-uniform injector is applied to improve the burning process of the turbine combustor. The results of the new CRN for NOx prediction in the gas turbine combustor show very good agreement with the experimental data from Korea Electric Power Research Institute.

关键词： Chemical Reactor Networks (CRN) Computational Fluid Dynamics (CFD) Perfectly Stirred Reactor (PSR) Plug Flow Reactor (PFR) Gas Turbine Combustor Oxides of Nitrogen Emission (NOx).

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