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Exact solution for thermal vibration of multi-directional functionally graded porous plates submerged in fluid medium

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Defence Technology（防务技术） 2024年第5期35卷 77-99页

作者： Quoc-Hoa Pham Van Ke Tran phu-cuong Nguyen Faculty of Engineering and Technology Nguyen Tat Thanh UniversityHo Chi Minh CityViet Nam Faculty of Mechanical Engineering Le Quy Don Technical UniversityHanoiViet Nam Advanced Structural Engineering Laboratory Department of Structural EngineeringFaculty of Civil EngineeringHo Chi Minh City Open UniversityHo Chi Minh CityViet Nam

An analytical method for analyzing the thermal vibration of multi-directional functionally graded porous rectangular plates in fluid media with novel porosity patterns is developed in this *** properties of MFG porous plates change according to the length,width,and thickness directions for various materials and the porosity distribution which can be widely applied in many fields of engineering and defence ***,new porous rules that depend on spatial coordinates and grading indexes are proposed in the present *** Hamilton's principle and the refined higher-order shear deformation plate theory,the governing equation of motion of an MFG porous rectangular plate in a fluid medium(the fluid-plate system)is *** fluid velocity potential is derived from the boundary conditions of the fluid-plate system and is used to compute the extra *** GalerkinVlasov solution is used to solve and give natural frequencies of MFG porous plates with various boundary conditions in a fluid *** validity and reliability of the suggested method are confirmed by comparing numerical results of the present work with those from available works in the *** effects of different parameters on the thermal vibration response of MFG porous rectangular plates are studied in *** findings demonstrate that the behavior of the structure within a liquid medium differs significantly from that within a vacuum ***,they offer appropriate operational approaches for the structure when employed in various mediums.

关键词： Plate-fluid contact Galerkin Vlasov's method Multi-directional functionally graded plate Novel porosity Thermal vibration Refined higher-order shear deformation theory

An isogeometric approach to static and transient analysis of fluid-infiltrated porous metal foam piezoelectric nanoplates with flexoelectric effects and variable nonlocal parameters

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Frontiers of Structural and Civil Engineering 2024年第3期18卷 461-489页

作者： Quoc-Hoa PHAM Van Ke Tran phu-cuong Nguyen Faculty of Engineering and Technology Nguyen Tat Thanh UniversityHo Chi Minh City 700000Vietnam Faculty of Mechanical Engineering Le Quy Don Technical UniversityHanoi 100000Vietnam Advanced Structural Engineering Laboratory Department of Structural EngineeringFaculty of Civil EngineeringHo Chi Minh City Open UniversityHo Chi Minh City 700000Vietnam

In this work,a novel refined higher-order shear deformation plate theory is integrated with nonlocal elasticity theory for analyzing the free vibration,bending,and transient behaviors of fluid-infiltrated porous metal foam piezoelectric nanoplates resting on Pasternak elastic foundation with flexoelectric *** analysis(IGA)and the Navier solution are applied to the *** innovation in the present study is that the influence of the in-plane variation of the nonlocal parameter on the free and forced vibration of the piezoelectric nanoplates is investigated for the first *** nonlocal parameter and material characteristics are assumed to be material-dependent and vary gradually over the thickness of *** on Hamilton’s principle,equations of motion are built,then the IGA approach combined with the Navier solution is used to analyze the static and dynamic response of the ***,we investigate the effects of the porosity coefficients,flexoelectric parameters,elastic stiffness,thickness,and variation of the nonlocal parameters on the mechanical behaviors of the rectangular and elliptical piezoelectric nanoplates.

关键词： isogeometric analysis fluid-infiltrated porous piezoelectric nanoplates static and transient analysis flexoelectric effect variable nonlocal parameters

Nonlinear dynamic analysis of functionally graded carbon nanotube-reinforced composite plates using MISQ20 element

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Frontiers of Structural and Civil Engineering 2023年第7期17卷 1072-1085页

作者： Quoc-Hoa PHAM Trung Thanh TRAN phu-cuong NGUYEN Advanced Structural Engineering Laboratory Department of Structural EngineeringFaculty of Civil EngineeringHo Chi Minh City Open UniversityHo Chi Minh City 700000Vietnam Faculty of Mechanical Engineering Le Quy Don Technical UniversityHanoi 100000Vietnam

The main objective of this study is to further extend the mixed integration smoothed quadrilateral element with 20 unknowns of displacement(MISQ20)to investigate the nonlinear dynamic responses of functionally graded carbon nanotube-reinforced composite(FG-CNTRC)plates with four types of carbon nanotube *** smooth finite element method is used to enhance the accuracy of the Q4 element and avoid shear locking without using any shear correction *** method yields accurate results even if the element exhibits a concave quadrilateral shape and reduces the error when the element meshing is ***,the element stiffness matrix is established by integrating the boundary of the smoothing *** motion equation of the FG-CNTRC plates is solved by adapting the Newmark method combined with the Newton–Raphson ***,the calculation program is coded in the MATLAB software and verified by comparing it with other published ***,the effects of the input parameters on the nonlinear vibration of the plates are investigated.

关键词： carbon nanotube MISQ20 FG-CNTRC plate nonlinear vibration nonlinear dynamic analysis SFEM

Friction characteristics of mechanically exfoliated and CVD-grown single-layer MoS_2

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Friction 2018年第4期6卷 395-406页

作者： dinh le Cao KY Bien-cuong TRAN KHAC Chinh Tam le Yong Soo KIM Koo-Hyun CHUNG School of Mechanical Engineering University of Ulsan Department of Physics and Energy Harvest Storage Research Center University of Ulsan

In this work, the friction characteristics of single-layer MoS2 prepared with chemical vapor deposition （CVD） at three different temperatures were quantitatively investigated and compared to those of single-layer MoS2 prepared using mechanical exfoliation. The surface and crystalline qualities of the MoS2 specimens were characterized using an optical microscope, atomic force microscope （AFM）, and Raman spectroscopy. The surfaces of the MoS2 specimens were generally flat and smooth. However, the Raman data showed that the crystalline qualities of CVD-grown single-layer MoS2 at 800 ℃ and 850 ℃ were relatively similar to those of mechanically exfoliated MoS2 whereas the crystalline quality of the CVD-grown single-layer MoS2 at 900 ℃ was lower. The CVD-grown single-layer MoS2 exhibited higher friction than mechanically exfoliated single-layer MoS2, which might be related to the crystalline imperfections in the CVD-grown MoS2. In addition, the friction of CVD-grown single-layer MoS2 increased as the CVD growth temperature increased. In terms of tribological properties, 800 ℃ was the optimal temperature for the CVD process used in this work. Furthermore, it was observed that the friction at the grain boundary was significantly larger than that at the grain, potentially due to defects at the grain boundary. This result indicates that the temperature used during CVD should be optimized considering the grain size to achieve low friction characteristics. The outcomes of this work will be useful for understanding the intrinsic friction characteristics of single-layer MoS2 and elucidating the feasibility of single-layer MoS2 as protective or lubricant layers for micro- and nano-devices.

关键词： atomic force microscope chemical vapor deposition grain boundary friction mechanical exfoliation MoS2

Isogeometric analysis for free vibration of bidirectional functionally graded plates in the fluid medium

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Defence Technology（防务技术） 2022年第8期18卷 1311-1329页

作者： Quoc-Hoa Pham phu-cuong Nguyen Van Ke Tran Trung Nguyen-Thoi Faculty of Civil Engineering Ho Chi Minh City Open UniversityHo Chi Minh CityViet Nam Faculty of Mechanical Engineering Le Quy Don Technical UniversityHanoiViet Nam Division of Computational Mathematics and Engineering Institute for Computational ScienceTon Duc Thang UniversityHo Chi Minh CityViet Nam Faculty of Civil Engineering Ton Duc Thang UniversityHo Chi Minh CityViet Nam

This paper for first time proposes an isogeometric analysis (IGA) for free vibration response of bi-directional functionally graded (BDFG) rectangular plates in the fluid medium. Material properties of the BDFG plate change in both the thickness and length directions via power-law distributions and Mori-Tanaka model. The governing equation of motion of BDFG plate in the fluid-plate system is formulated basing on Hamilton's principle and the refined quasi three-dimensional (3D) plate theory with improved function f(z). The fluid velocity potential is derived from the boundary conditions of the fluid-plate system and is used to determine the added mass. The discrete system of equations is derived from the Galerkin weak form and numerically analyzed by IGA. The accuracy and reliability of the proposed solutions are verified by comparing the obtained results with those published in the literature. Moreover, the effects of the various parameters such as the interaction boundary condition, geometric parameter, submerged depth of plate, fluid density, fluid level, and the material volume control coefficients on the free vibration behavior of BDFG plate in the fluid medium are investigated in detail. Some major findings regarding the numerical results are withdrawn in conclusions.

关键词： Contact plate-fluid Refined quasi 3D plate theory Mori-Tanaka model Isogeometric analysis Bidirectional functionally graded plate

A novel approach for synthesis of hierarchical mesoporous Nd2O3 nanomaterials

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Journal of Rare Earths 2017年第7期35卷 677-682页

作者： le Huu Trinh dinh Quang Khieu Hoang Thai Long Tran Thai Hoa Duong Tuan Quang Nguyen Duc cuong College of Sciences Hue University 77 Nguyen Hue Hue City Viet Nam Faculty of Hospitality and Tourism Hue University 22 Lam Hoang Hue CityViet Nam College of Education Hue University 34 Le LoL Hue City Viet Nam

A novel route to the fabrication of hierarchical mesoporous Nd_2O_3 nanostructures including nanospheres and nanoporous network was described. Their structure and morphology evolution of the as-synthesized materials were determined by various techniques such as scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy, Fourier transforminfrared spectra, nitrogen adsorption/desorption isotherm, and a formation mechanism was proposed. The results revealed that the Nd_2O_3 nanospheres had the diameter of 300 nm, which were composed of small primary nanoparticles（NPs） with the size of 10 nm. The nanoporous structure also formed the NPs of ca. 10 nm which were connected with each other to form a three-dimensional（3D） texture. This simple and mild approach to fabricate hierarchical mesoporous Nd_2O_3 nanostructures could be easily scaled up and potentially extended to synthesize other oxide hierarchical structures.

关键词： Nd2O3 hierarchical nanostructures nanospheres nanoporous network rare earths

Eye Strain Detection During Online learning

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Intelligent Automation & Soft Computing 2023年第3期35卷 3517-3530页

作者： le Quang Thao Duong Duc cuong Vu Manh Hung le Thanh Vinh Doan Trong Nghia dinh Ha Hai Nguyen Nhan Nhi Faculty of Physics VNU University of ScienceHanoi100000Vietnam University of Science Vietnam National UniversityHanoi100000Vietnam VNU-HUS High School for Gifted StudentsHanoi100000Vietnam Hanoi-Amsterdam High School for the Gifted Hanoi100000Vietnam

The recent outbreak of the coronavirus disease of 2019(Covid-19)has been causing many disruptions among the education systems worldwide,most of them due to the abrupt transition to online *** sudden upsurge in digital electronic devices usage,namely personal computers,laptops,tablets and smart-phones is unprecedented,which leads to a new wave of both mental and physical health problems among students,for example eye-related *** overexpo-sure to electronic devices,extended screen time usage and lack of outdoor sun-light have put a consequential strain on the student’s ophthalmic health because of their young age and a relative lack of responsibility on their own *** to take appropriate external measures to mitigate the negative effects of this pro-cess could lead to common ophthalmic illnesses such as myopia or more serious *** remedy this situation,we propose a software solution that is able to track and capture images of its users’eyes to detect symptoms of eye illnesses while simultaneously giving them warnings and even offering *** meet the requirements of a small and light model that is operable on low-end devices without information loss,we optimized the original MobileNetV2 model with depth-wise separable convolutions by altering the parameters in the last layers with an aim to minimize the resizing of the input image and obtained a new model which we call *** with applying the knowledge distillation tech-nique and ResNet-18 as a teacher model to train the student model,we have suc-cessfully increased the accuracy of the EyeNet model up to 87.16%and support the development of a model compatible with embedded systems with limited computing power,accessible to all students.

关键词： Digital eye strain Covid-19 online study knowledge distillation eye care EyeNet

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

Technical Procedure Determination of Thoron Indoor Concentration by LR-115 Type II

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Journal of Environmental Science and Engineering(B) 2016年第3期5卷 109-114页

作者： Nguyen Thi Thu Ha Frinh Van Giap le dinh cuong Center for Environmental Radiation Monitoring and Impact Assessment Institute for Nuclear Science and Technology (INST)Vietnam Atomic Energy Institute (VINATOM) Hanoi 100000 Vietnam

Thoron （Rn-220） is an invisible, odorless radioactive gas and nine times heavier than air. Purpose of project is to set up procedure to determine Rn-220 concentration which has been carried out in laboratory using Solid State Nuclear Track Detector （SSNTD） based passive detector technique. In this study, technical procedure has been applied in Karlsruhe diffusion chamber and LR-115, Type II strippable （Kodak Pathe, France） detector. The results have investigated how LR-115 work for Rn-220 by using Monazite ore to simultaneously measure Rn-222 and Rn-220. To carry out experiment, Karlsruhe diffusion chamber is used to with and without Poly-Ethylene （PE） membrane. Karlsruhe diffusion chamber with PE membrane only detect Rn-222, without PE membrane detect total Rn-222 and Rn-220. Precision evaluation by duplicate measure at 8 cm detector-source distance with relative standard deviation is less than 2.54%. Testing technical procedure, detectors have been sent to National Institute of Radiological Science （NIRS） for Rn-220 calibration exposure. After detectors have been calibration exposure at NIRS, it carried out all the following steps of procedure which set up at laboratory in 1NST, Vietnam. Finally, calibration factor calculated is 0.21 （tracks-cm2/Bq·m3·h） and constructed curve between integrated Tn-220 concentration and tracks density with factor R2 = 0.975.

关键词： LR-115 type-II (SSNTDs) Rn-220 spark counter.