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Journal of Materials Science & Technology 2006年第4期22卷 500-510页

作者： minh-quy le Seock-Sam KIM Department of Mechanics of Materials and Structures Faculty of Mechanical EngineeringHanoi University of TechnologyDai Co Viet RoadHanoiVietnam School of Mechanical Engineering Kyungpook National UniversityDaegu 701-702Korea

Spherical indentation of ceramic coatings with metallic interlayer was performed by means of axisymmetric finite element analysis （FEA）. Two typical ceramic coatings with relatively high and low elastic modulus deposited on aluminum alloy and carbon steel were considered. Various combinations of indenter radius-coating thickness ratios and interlayer thickness-coating thickness ratios were used in the modeling. The effects of the interlayer, the coating and the substrate on the indentation behavior, such as the radial stress distribution along the coating surface as well as the coating interface, and the plastic deformation zone evolution in the substrate were investigated in connection with the above mentioned ratios. The coating cracking dominant modes were also discussed within the context of the peak tensile stresses on the coating surface and on the coating interface.

关键词： Finite element analysis Ceramic coatings Indentation Interlayer

Element Analysis of Instrumented Sharp Indentations into Pressure-sensitive Materials

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Journal of Materials Science & Technology 2007年第2期23卷 277-282页

作者： minh-quy le Seock-Sam KIM Department of Mechanics of Materials & Structures Faculty of Mechanical EngineeringHanoi University of TechnologyDai Co Viet RoadHanoi Vietnam School of Mechanical Engineering Kyungpook National UniversityDaegu 702-701South Korea

Finite element analysis was carried out to investigate the conical indentation response of elastic-plastic solids within the framework of the hydrostatic pressure dependence and the power law strain hardening. A large number of 40 difierent combinations of elasto-plastic properties with n ranging from 0 to 0.5 and σy/E ranging from 0.0014 to 0.03 were used in the computations. The loading curvature C and the average contact pressure Pave were considered within the concept of representative strains and the dimensional *** functions associated with these two parameters were formulated for each studied value of the pressure sensitivity. The results for pressure sensitive materials lie between those for Von Mises materials and the elastic model.

关键词： Finite element analysis Indentation Mechanical Properties Pressure-sensitive materials

Element Analysis of Ceramic Coatings under Spherical Indentation with Metallic Interlayer: PartⅡRing Crack

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Journal of Materials Science & Technology 2006年第5期22卷 594-598页

作者： minh-quy le Seock-Sam KIM Department of Mechanics of Materials & Structures Faculty of Mechanical Engineering Hanoi University of TechnologyDai Co Viet RoadHanoiVietnam School of Mechanical Engineering Kyungpook National University Daegu 701-702Korea

Spherical indentation of ceramic coatings with metallic interlayer was performed by means of axisymmetric finite element analysis （FEA）. Two typical ceramic coatings with relatively high and low elastic modulus deposited on aluminum alloy and carbon steel were considered. The fracture mechanics of the ceramic coatings mechanisms due to occurrence of surface ring cracks extending traverse the coating thickness under spherical indentation are investigated within the framework of linear fracture mechanics. The J-integral associated to such cracks was computed. The evolution of J-integral vs the crack length and the indentation depth was studied. The effects of the interlayer, the coating and the substrate on the J-integral evolution were discussed. The results show that a suitable metallic interlayer can improve the fracture resistance of the coating systems under the same indentation conditions through reducing the J-integral.

关键词： Finite element analysis Ceramic coatings Indentation Interlayer Crack

Atomistic simulation of free transverse vibration of graphene,hexagonal SiC, and BN nanosheets

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Acta Mechanica Sinica 2017年第1期33卷 132-147页

作者： Danh-Truong Nguyen minh-quy le Thanh-Lam Bui Hai-le Bui School of Mechanical Engineering Hanoi University of Science and Technology Hanoi 10000 Vietnam International Institute for Computational Science and Engineering Hanoi University of Science and TechnologyHanoi 10000 Vietnam Faculty of Mechanical Engineering Hanoi University of Industry Hanoi 10000 Vietnam

Free transverse vibration of monolayer graphene, boron nitride (BN), and silicon carbide (SiC) sheets is investigated by using molecular dynamics finite element method. Eigenfrequencies and eigenmodes of these three sheets in rectangular shape are studied with different aspect ratios with respect to various boundary conditions. It is found that aspect ratios and boundary conditions affect in a similar way on natural frequencies of graphene, BN, and SiC sheets. Natural frequencies in all modes decrease with an increase of the sheet’s size. Graphene exhibits the highest natural frequencies, and SiC sheet possesses the lowest ones. Missing atoms have minor effects on natural frequencies in this study.

关键词： Atomistic simulation Hexagonal sheet Transverse vibration Molecular dynamics finite element method

Derivation of FFT numerical bounds of the effective properties ofcomposites and polycristals

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Theoretical & Applied Mechanics letters 2021年第2期11卷 94-101页

作者： minh-Tan Nguyen quy-Dong To Vincent Monchiet Univ Gustave Eiffel Univ Paris Est CreteilCNRSMSME UMR 8208F-77454 Marne-la-VallÃl’eFrance

In this paper,we provide exact fast Fourier transform(FFT)-based numerical bounds for the elastic prop-erties of composites having arbitrary *** bounds,an upper and a lower,are derivedby considering usual variational principles based on the strain and the stress *** bounds arecomputed by solving the Lippmann-Schwinger equation together with the shape coefficients which al-low an exact description of the microstructure of the *** coefficients are the exact Fouriertransform of the characteristic functions of the *** this study,the geometry of the microstructureis approximated by polygonals(two-dimensional,2D objects)and by polyhedrons(three-dimensional,3Dobjects)for which exact expressions of the shape coefficients are *** applications are pre-sented in the paper showing the relevance of the *** the first benchmark example,we considerthe case of a composite with *** effective elastic coefficients ares derived and compared,consider-ing the exact shape coefficient of the circular inclusion and its approximation with a ***,thehomogenized elastic coefficients are derived for a composite reinforced by 2D flower-shaped inclusionsand with 3D toroidal-shaped ***,the method is applied to polycristals considering Voronoitessellations for which the description with polygonals and polyhedrons becomes *** comparisonwith the original FFT method of Moulinec and Suquet is provided in order to show the relevance of thesenumerical bounds.

关键词： Composites Homogenization Fast Fourier transform Numerical bounds

Upconversion luminescence of Gd2O3:Er3+and Gd2O3:Er3+/silica nanophosphors fabricated by EDTA combustion method

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Journal of Rare Earths 2019年第11期37卷 1126-1131页

作者： le Quoc minh Tran Kim Anh Nguyen Duy Hung Pham Thi minh Chau Nguyen Thi quy Hai Ho Van Tuyen Vu Thi Thai Ha Vu Duc Tu Wieslaw Strek Institute of Theoretical and Applied Research Duy Tan UniversityDa Nang 55000Viet Nam Advanced Institute for Science and Technology Hanoi University of Science and Technology1 Dai Co VietHai Ba TrungHanoiViet Nam Institute of Materials Science Vietnam Academy of Science and Technology18 Hoang Quoc Viet RoadCau Giay DistrictHanoiViet Nam Institute of Low Temperature and Structure Research Polish Academy of Science 2 OkolnaWroclawPoland

Gd2O3:Er^3+nanophosphors were fabricated by the combustion method in presence of Na2 ethylene diamine tetra acetic acid(EDTA-Na2)as fuel at not high temperature(≤350℃)within a very short time of 5 *** added concentration of Er^3+ions in Gd2O3 matrix was changed from 0.5 mol%to 5.0 mol%.The X-ray diffraction pattern of samples indicates the monoclinic structure of Gd2O3:Er^3+.The morphology and chemical composition analysis of the Gd2O3:Er^3+samples are characterized by a field emission scanning electron microscope(FESEM)and a Fourier-transform infrared spectrometer(FTIR).The photoluminescence(PL),photo luminescence excitation(Ple)and upconversion(UC)at room temperature of the prepared materials with different concentrations of Er^3+were *** PL of Gd2O3:Er^3+nanomaterials are shown in visible at 545,594,623,648,688 nm under excitation at 275 *** emission bands from transitions of Er^3+from 2P3/2 to 4F9/2 are observed,UC luminescent spectra of the Gd2O3:Er^3+/silica nanocomposites under 976 nm excitation show the bands at 548 and 670 *** influence of excitation power at 980 nm for transitions were measured and *** results indicate that the upconversion process of Gd2O3:Er^3+/silica is two photons absorption *** low temperature dependence of UC luminescent intensities of the main bands of Gd2O3:Er^3+was investigated towards development of a nanotemperature sensor in the range of 10-300 K.

关键词： Upconversion luminescence Gd2O3:Er3+ Gd2O3:Er3+/silica Nanophosphors EDTA combustion Rare earths

Discrete-time sliding mode control with power rate exponential reaching law of a pneumatic artificial muscle system

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Control Theory and Technology 2022年第4期20卷 514-524页

作者： quy-Thinh Dao Trung-Kien le Tri Van-Anh Nguyen Manh-Linh Nguyen School of Electrical and Electronic Engineering Hanoi University of Science and TechnologyDai Co VietHanoi 11615Vietnam

This paper develops a discrete-time sliding mode controller with a power rate exponential reaching law approach to enhance the performance of a pneumatic artificial muscle system in both reaching time and chattering *** proposed method dynamically adapts to the variation of the switching function,which is based on an exponential term and a power rate term of the sliding ***,the controlled system can achieve high tracking performance while still obtain chattering-free ***,the effectiveness of the proposed method is validated through multiple experimental tests,focused on a dual pneumatic artificial muscle ***,experimental results show the effectiveness of the proposed approach in this paper.

关键词： Pneumatic artificial muscle Discrete-time sliding mode control Exponential reaching law Chattering

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

Results of Testing Maize Hybrids on Lands Shifting from Rice-Growing Areas of less Efficiency in the Mekong Delta

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Journal of Agricultural Science and Technology(B) 2015年第4期5卷 241-246页

作者： le quy Kha Institute of Agricultural Sciences for Southern Vietnam 121 Nguyen Binh Khiem Street District 1 Ho Chi Minh City Vietnam

Forecasters predict that by 2020 there will be 4.5 or 5 million tons per annum maize supply deficiency in Vietnam. As a result of this projection, the government responded by shifting 80,000 ha of low-efficiency rice production areas into maize production （2014-2015） and this area of production for maize is expected to increase to 150,000 ha by 2016-2020. Nevertheless, not all commercial maize hybrids could be suitable for rice-growing land in the Mekong Delta and a national project of hybrid maize development for Mekong Delta has been conducted since early 2014. In the project, yield trials of 20 maize hybrids, sourced from Vietnamese institutions and the private sector including Syngenta （NK67） and Dekalb （DK9901）, were sown in Dong Thap, Hau Giang and Long An provinces situated in the Mekong Delta, in minor acid sulphate soils with a pH of 5.0-5.5. The trial included three replications in an Alpha lattice design conducted during spring-summer in 2014. The hybrids flowered at 50-52 d after planting and physiologically matured between 93-97 d after planting. This suggested they would be suitable for cropping systems, which was comprised of three seasons per year. To determine which hybrid is best suited for the region, researchers evaluated yield and ear characteristics. The average yield of the genotypes across locations was 52.03, 54.92 and 57.60 quintals/ha, respectively, and the heritability of genotypes in each location was 0.51, 0.81 and 0.61, respectively. The mean yield of DK9901 was 58.19 quintals/ha, ranking the 7th among 20 hybrids, and NK67 was 47.58 quintals/ha, ranking the 19th. The grand mean was 54.92 quintals/ha and heritability for all genotypes was 0.79. The highest yield was produced by the Southern seed company hybrid SSC474 （69.39 quintals/ha）, which yielded significantly more maize than DK9901 （58.19 quintals/ha） at P 〈 0.05, followed by VS71 from National Maize Research Institute （NMRI） at 63.52 quintals/ha, and LCH9A from NMRI at 63.39 quin

关键词： Maize (Zea mays L.) hybrid Mekong Delta rice-growing land yield trials.

Application of Remote Sensing and GIS Technology in Mapping Partition Saline Intrusion to Paddy Land:A Case Study at Phu Vang District,Thua Thien Hue Province

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Journal of Agricultural Science and Technology(A) 2017年第B10期7卷 48-59页

作者： Nguyen Hoang Khanh Linh le Ngoc Phuong quy Truong Do minh Phuong Nguyen Trac Ba An Faculty of Land Resources and Agricultural Environment University of Agriculture and ForestryHue University102 Phung Hung StreetHue 530000Vietnam

Adapting and restricting salinity intrusion in Vietnam is being concerned by more researchers as well as the local *** study aimed to use remote sensing and geographic information system(GIS)technology for mapping paddy areas and salinity intrusion in spring crop 2015 at Phu Vang district,thereby helping precondition for assessing and monitoring changes in salinity intrusion to serve for salinization management in study *** on acquisition imagery,land use map and normalized difference vegetation index(NDVI)were extracted to interpolate the salinity of area by combining the laboratory analysis of collected soil samples from the *** result showed that there were 1,067.107 ha of salinity land area accounting for 10.04%of the rice land in Phu Vang district,where the moderate salinity level was 180.67 ha and low salinity level was 866.431 *** salinity rice land was mainly distributed in Vinh Ha commune,Phu An commune and Phu Dien *** salinity in this area ranged from 0.4 mS/cm to 1.41 mS/cm and the moderate salinity was approximately 0.9 mS/***,this research also showed that the salinity(electrical conductivity)and the development of vegetation(NDVI)were closely related with each other up to 61.4%.

关键词： GIS remote sensing normalized difference vegetation index salinity intrusion paddy land