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Finite element analysis of functionally graded sandwich plates with porosity via a new hyperbolic shear deformation theory

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Defence Technology（防务技术） 2022年第3期18卷 490-508页

作者： Pham Van vinh le Quang Huy Department of Solid Mechanics Le Quy Don Technical University236 Hoang Quoc VietHanoiViet Nam Institute of Techniques for Special Engineering Le Quy Don Technical University236 Hoang Quoc VietHanoiViet Nam

This study focusses on establishing the finite element model based on a new hyperbolic sheareformation theory to investigate the static bending,free vibration,and buckling of the functionally graded sandwich plates with *** novel sandwich plate consists of one homogenous ceramic core and two different functionally graded face sheets which can be widely applied in many fields of engineering and defence *** discrete governing equations of motion are carried out via Hamilton’s principle and finite element *** computation program is coded in MATLAB software and used to study the mechanical behavior of the functionally graded sandwich plate with *** present finite element algorithm can be employed to study the plates with arbitrary shape and boundary *** obtained results are compared with available results in the literature to confirm the reliability of the present ***,a comprehensive investigation of the effects of several parameters on the bending,free vibration,and buckling response of functionally graded sandwich plates is *** numerical results shows that the distribution of porosity plays significant role on the mechanical behavior of the functionally graded sandwich plates。

关键词： Functionally graded sandwich plates Porous plates Hyperbolic shear deformation theory Bending analysis Free vibration analysis Buckling analysis

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

On the derivation of the entropy of ideal quantum gases confined in a three-dimensional harmonic potential

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Communications in Theoretical Physics 2020年第4期72卷 106-111页

作者： le Tri Dat vinh N T Pham Laboratory of Applied Physics Advanced Institute of Materials ScienceTon Duc Thang UniversityHo Chi Minh City 756636Vietnam Faculty of Applied Sciences Ton Duc Thang UniversityHo Chi Minh City 756636Vietnam Ho Chi Minh City University of Education Ho Chi Minh City 748342Vietnam

In this work,the entropy functions of ideal quantum gases in a three-dimensional harmonic trap are analytically calculated using temperature as an explicit ***,the applicability of the analytical formulas is validated by comparison with the numerical *** results illustrate that the obtained functions could be applied for the whole temperature regime with a maximum relative deviation of less than 7.5%in the vicinity of the critical temperature Tcin the case of Bose ***,for Fermi gases,although the analytical formula fits well at very low-and high-temperature regimes,it cannot be applied at temperature in the range[0.3-0.5]T_F,where T_F is the Fermi *** addition,the consistency between our formulas and classical ones at significantly high temperatures is also discussed.

关键词： thermodynamic properties entropy 3D harmonic trap ideal quantum gases

Investigation of Punch Resistance of the Allomyrira dichtoloma Beetle Forewing

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Journal of Bionic Engineering 2018年第1期15卷 57-68页

作者： Ngoc San Ha vinh Tung le Nam Seo Goo Smart Microsystem Research Laboratory Department of Advanced Technology Fusion Division of Interdisciplinary Studies Konkuk University Seou105029 Republic of Korea Faculty of Science Engineering and Technology Swinburne University of Technology Hawthorn VIC 3122 Australia

In this study, the punch resistance of the beetle forewing was investigated to address the ability of the forewing against the external force. The punch resistance of the forewing was measured for different sizes and sexes of beetles using a conventional testing method in conjunction with the Digital Image Correlation （DIC） technique. The results showed that the maximum fracture load was measured around 23 N for the female beetle and around 20.2 N for the male beetle in the front-side punch test. Moreover, the fracture load in the front-side punch test was higher than that in the back-side punch test for both male and female beetles. This means that the beetle forewing plays a protection role against external loads. Furthermore, the puncture energy in the front-side punch test for the female beetle （6.91 m J） was a little higher than that for the male beetle （5.27 mJ）. In addition, the DIC results revealed that the first crack occurred along the trachea line and the second crack then appeared in the direction that was perpendicular to the direction of the first crack. This study provides a com- prehensive understanding of the mechanical protection properties of the beetle forewing and offers a good lesson for studying lightweight bio-inspired composite material.

关键词： beetle forewing punch test punch energy digital image correlation

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

Investigation of the hydro-mechanical behaviour of fouled ballast

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2013年第4期14卷 244-255页

作者： Yu-jun CUI trong vinh DUONG Anh Minh TANG Jean-Claude DUPLA Nicolas CALON Alain ROBINET Laboratoire Navier/CERMES Ecole des Ponts ParisTechBlaise PascalCité DescartesChamps-sur-Marne 77455 Marne-la-Vallée Cedex-France French National Railway Company 93574La Plaine St DenisFrance

In this study,a fouled ballast taken from the site of Sénissiat,France,was *** the hydraulic behaviour,a large-scale cell was developed allowing drainage and evaporation tests to be carried out with monitoring of both suction and volumetric water content at various positions of the *** was observed that the hydraulic conductivity of fouled ballast is decreasing with suction increase,as for common unsaturated *** effect of fines content was found to be *** the mechanical behaviour,both monotonic and cyclic triaxial tests were carried out using a large-scale triaxial *** water contents were *** results were interpreted in terms of shear strength and permanent axial *** appeared that the water content is an important factor to be accounted for since any increase of water content or degree of saturation significantly decreases the shear strength and increases the permanent *** modelling has been attempted based on the experimental *** model in its current state is capable of describing the effects of stress level,cycle number and water content.

关键词： Fouled ballast Degree of saturation Hydraulic behaviour Mechanical behaviour Fines content Constitutive modelling

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

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

Fabrication and characterization of YVO_4:Eu^(3+) nanomaterials by the microwave technique

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Journal of Rare Earths 2011年第12期29卷 1137-1141页

作者： Tran Thu Huong Vu Duc Tu Tran Kim Anh le Thi vinh le Quoc Minh Institute of Materials Science Vietnamese Academy of Science and Technology University of Engineering and Technology National University Hanoi Departments of Chemistry Hanoi University of Mining and Geology

Fabrication and characterization of YVO4：Eu^3＋ nanophosphors prepared by microwave （MW） irradiation assisted soft template synthesis were reported. The effects of synthesis conditions such as different powers of MW irradiation, pH values and concentration of reac- tion materials on properties of nanophosphor were also investigated to obtain the controllable size, morphology and high luminescence efficiency. Morphology, crystalline structure, and optical properties were characterized by field emission scanning electron microscopy （FE-SEM）, X-ray diffraction （XRD） and fluorescence spectroscopy, respectively. The results showed that YVOa：Eu^3＋ nanophosphors were obtained by using diethyleneglycol （DEG） as soft template, with pH values in the range of 4 to 12, upon microwave irradiation from 300 to 900 W, at temperature of 80 ℃. The high fluorescent YVOa：Eu^3＋ nanocrystals obtained with size from 15 nm down to 8 nm are more effective to develop an ultrahigh sensitive fluorescent label for biomolecule, cell and tissue.

关键词： microwave synthesis method DEG soft template YVO4:Eu^3+ nanophosphor luminescence rare earths