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Adaptive selective ES-FEM limit analysis of cracked plane-strain structures

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Frontiers of Structural and Civil Engineering 2015年第4期9卷 478-490页

作者： H. nguyen-xuan T. RABCZUK Center for Interdisciplinary Research in Technology Ho Chi Minh City University of Technology (HUTECH) vietnam Institute of Structural Mechanics Bauhaus-Universitat Weimar Weimar 99423 Germany

this paper presents a simple and efficient approach for predicting the plastic limit loads in cracked plane-strain structures. We use two levels of mesh repartitioning for the finite element limit analysis. The master level handles an adaptive primal-mesh process through a dissipation-based indicator. The slave level performs the subdivision of each triangle into three sub-triangles and constitutes a dual mesh from a pair of two adjacent sub-triangles shared by common edges of the primal mesh. Applying a strain smoothing projection to the strain rates on the dual mesh, the incompressibility constraint and the flow rule constraint are imposed over the edge-based smoothing domains and everywhere in the problem domain. The limit analysis problem is recast into the compact form of a second-order cone programming (SOCP) for the purpose of exploiting interior-point solvers. The present method retains a low number of optimization variables. It offers a convenient way for designing and solving the large-scale optimization problems effectively. Several benchmark examples are given to show the simplicity and effectiveness of the present method.

关键词： cracked structure limit analysis von Mises criterion edge-based strain smoothing second-order cone programming adaptive

Structural and luminescent properties of (Eu,Tb) PO_4·H_2O nanorods/nanowires prepared by microwave technique

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Journal of Rare Earths 2011年第12期29卷 1170-1173页

作者： nguyen Thanh huong nguyen Duc Van Dinh Manh Tien Do Khanh Tung nguyen Thanh Binh Tran Kim Anh Le Quoc Minh Institute of Materials Science Vietnam Academy of Science and Technology University of Engineering and Technology National University HanoiVietnam

Nanowires/nanorods of europium/terbium orthophosphate monohydrate with Eu^3＋ concentration of 6, 11, and 20 at.% were prepared by microwave synthesis method. The effects of Eu^3＋ doping concentration on structure, morphology and optical properties of nanomaterials were also investigated. The results showed that, for all studied Eu^3＋ doping concentrations, a single-crystalline phase of rhabdophane-type （Eu,Tb）PO4·H2O nanowires/nanorods was obtained by using microwave heating of an aqueous solution of terbium（Ⅲ） nitrate, europium（Ⅲ） nitrate and NH4H2PO4 with pH=2. The length and width of these nanowires/nanorods ranged from 150 to 300 nm and from 10 to 50 nm, respectively. The evidence of energy transfer from Tb^3＋ to Eu^3＋ due to the energy overlap between the donor Tb^3＋ and the acceptor Eu^3＋was observed obviously via a significant enhancement in the luminescent intensity of Eu^3＋. Keywords：

关键词： microwave technique nanowires/nanorods energy transfer fluorescence spectroscopy rare earths

An Efficient Adaptive Hierarchical Sliding Mode Control Strategy Using Neural Networks for 3D Overhead Cranes

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International Journal of Automation and computing 2019年第5期16卷 614-627页

作者： Viet-Anh Le Hai-xuan Le Linh nguyen Minh-xuan Phan Department of Automatic Control Hanoi University of Science and TechnologyHanoi 10000Vietnam Centre for Autonomous Systems University of Technology SydneyNew South Wales 2007Australia

In this paper, a new adaptive hierarchical sliding mode control scheme for a 3D overhead crane system is proposed. A controller is first designed by the use of a hierarchical structure of two first-order sliding surfaces represented by two actuated and un-actuated subsystems in the bridge crane. Parameters of the controller are then intelligently estimated, where uncertain parameters due to disturbances in the 3D overhead crane dynamic model are proposed to be represented by radial basis function networks whose weights are derived from a Lyapunov function. The proposed approach allows the crane system to be robust under uncertainty conditions in which some uncertain and unknown parameters are highly difficult to determine. Moreover, stability of the sliding surfaces is proved to be guaranteed. Effectiveness of the proposed approach is then demonstrated by implementing the algorithm in both synthetic and reallife systems, where the results obtained by our method are highly promising.

关键词： 3D overhead crane adaptive control hierarchical sliding mode control neural network radial basis function

A New Species of Rhacophorus(Amphibia:Anura:Rhacophoridae)from Vietnam

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Asian Herpetological Research 2017年第4期18卷 221-234页

作者： Tao thien nguyen Cuong The PHAM Truong Quang nguyen Hoa thi NINH Thomas ZIEGLER Vietnam National Museum of Nature Vietnam Academy of Science and Technology18 Hoang Quoc Viet RoadHanoiVietnam Institute of Ecology and Biological Resources Vietnam Academy of Science and Technology18 Hoang Quoc VietHanoiVietnam Graduate University of Science and Technology Vietnam Academy of Science and Technology18 Hoang Quoc VietCau GiayHanoiVietnam The Kyoto University Museum Kyoto UniversityYoshida HonmachiSakyokuKyoto 606-8501Japan Hanoi National University of Education 136 Xuan ThuyCau GiayHanoiVietnam AG Zoologischer Garten K6ln Riehler Strasse 173D-50735 CologneGermany Institute of Zoology University of CologneZiilpicherStrafle 47bD-50674 CologneGermany

We describe a new species of Rhacophorus based on two adult specimens collected from Hoa Binh Province, northern Vietnam. Rhacophorus hoabinhensis sp. nov. is distinguishable from its congeners on the basis of a combination of the following morphological characters： size small （SVL 31.1-32.5 mm in males）; head slightly longer than wide; vomerine teeth absent; snout short （SNL/SVL 0.16）; dorsal skin smooth; forearm and tarsus with dermal fringes; dermal appendage at vent present; webbing formula on fingers I12/3-12/3II1-2III1-1IV and on toes I3/4-1II1/2- IIII1/2-1IVI-1/2V; dorsal surface grey yellow with brown spots; lower jaw region dark grey, throat, chest and belly cream; anterior and posterior thighs, as well as ventral surface of tibia orange. The interspecific uncorrected genetic distances （16S rRNA gene） between the new species from Hoa Binh and other analyzed congeners varied from 9.8% to 17.4%. In the phylogenetic analyses, the new species revealed to be a representative of Rhacophorus and was nested within the R. hoanglienensis-orlovi species group.

关键词： Rhacophorus hoabinhensis sp.nov karst forest molecular phylogeny taxonomy Hoa Binh Province

Clinical Trial of Measles and Rubella Combined Vaccine Produced by POLYVAC in Vietnam

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Open Journal of Pediatrics 2018年第2期8卷 178-188页

作者： nguyen Dang Hien nguyen Thuy huong Ngo Thu huong Pham thi Phuong Thao Dinh Hong Duong nguyen xuan Dong Tomio Lee Takashi Ito Tetsuo Nakayama Center for Research and Production of Vaccines and Biologicals (POLYVAC) Hanoi Vietnam Military Academy of Medicine Hanoi Vietnam Kitasato Vaccine Plant Kitasato Daiichi Sankyo Vaccine Saitama Japan Laboratory of Viral Infection I Kitasato Institute for Life Sciences Tokyo Japan

A clinical trial of measles and rubella combined vaccine (MR: MRVAC) produced by POLYVAC was conducted in Vietnam in 2016. A total of 756 subjects were enrolled, and 504 were allocated to MRVAC and 252 to control MR vaccine groups. Paired sera were obtained in 733, and the number of subjects was 403 aged 1 - 2 years, 164 aged 2 - 18 years, and 166 aged 18 - 45 years. Antibodies against measles and rubella viruses were evaluated by EIA. Most subjects had been immunized with a single dose of Expanded Programme on Immunization (EPI) measles vaccine at 9 months of age. Only 41 of 403 subjects aged 1 - 2 years were negative for measles antibody before vaccination, and all became seroconverted. A serological response of more than a 2-fold increase against measles was noted in 214 (47%, 95% CI;42.4% - 51.6%) of 458 initially seropositive individuals immunized with MRVAC and 65 (28%, 95% CI;22.3% - 33.8%) of 234 in the control group, and geometric mean titer (GMT) after vaccination was 25.49-5.60 in MRVAC and 25.03-5.24 in control group. Seroconversion against rubella virus after immunization with MRVAC was noted in 267 (98.5%, 95% CI;97.1% - 100%) of 271 initially seronegative subjects, similar to that after immunization with control group. GMT after immunization with MRVAC was 24.88-5.11 significantly lower than that after immunization with control vaccine (25.59-5.80). Most subject ≥ 2 years of age had rubella antibody because of MR vaccination campaign and no significant serological response was observed in initially seronegatives. MRVAC was highly immunogenic and safe vaccine and the domestic production of MR vaccine would contribute to realizing the goal of eliminating measles and rubella.

关键词： Measles Vaccine Rubella Vaccine MR Combined Vaccine Elimination of Measles and Rubella

The Basis for Design and Manufacture of a DSP-Based Coincidence Spectrometer

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Journal of Analytical Sciences, Methods and Instrumentation 2013年第3期3卷 152-157页

作者： nguyen xuan Hai Pham Ngoc Tuan nguyen Nhi Dien Dang Lanh Tuong thi Thu huong Pham Dinh Khang Nuclear Research Institute Dalat Vietnam Nuclear Research Institute Dalat Vietnam 2Nuclear Training Center Hanoi Vietnam Nuclear Research Institute Dalat Vietnam 2Nuclear Training Center Hanoi Vietnam. Nuclear Training Center Hanoi Vietnam

The coincidence technique and the coincidence spectroscopy have been developed and applied for over 40 years. Most of popular coincidence measurement systems were based on analog electronics techniques such as time to amplitude conversion (TAC) or logic selecting coincidence unit. The above-mentioned systems are relatively cumbersome and complicated to use. With the strong growth of digital electronics techniques and computational science, the coincidence measurement systems will be constructed simpler but more efficient with the sake of application. this article presents the design principle and signal processing of a simple two-channel coincidence system by a technique of digital signal processing (DSP) using Field Programmable Gate Arrays (FPGA) devices at Nuclear Research Institute (NRI), Dalat.

关键词： Coincidence Spectrometer Digital Signal Processing FPGA

Predicting roof displacement of roadways in underground coal mines using adaptive neuro-fuzzy inference system optimized by various physics-based optimization algorithms

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Journal of Rock Mechanics and Geotechnical Engineering 2021年第6期13卷 1452-1465页

作者： Chengyu Xie Hoang nguyen xuan-Nam Bui Van-thieu nguyen Jian Zhou School of Environment and Resources Xiangtan UniversityXiangtan411105China Mining Faculty Hanoi University of Mining and GeologyHanoi100000Viet Nam Innovations for Sustainable and Responsible Mining(ISRM)Group Hanoi University of Mining and GeologyHanoi100000Viet Nam Artificial Intelligence Independent Research Group Hanoi100000Viet Nam School of Resources and Safety Engineering Central South UniversityChangsha410083China

Due to the rapid industrialization and the development of the economy in each country,the demand for energy is increasing *** coal mines have to pace up the mining operations with large production to meet the energy *** requirement has led underground coal mines to go deeper with more difficult conditions,especially the mining hazards,such as large deformations,rockburst,coal burst,roof collapse,to name a ***,this study aims at investigating and predicting the stability of the roadways in underground coal mines exploited by longwall mining method,using various novel intelligent techniques based on physics-based optimization algorithms(***-verse optimizer(MVO),equilibrium optimizer(EO),simulated annealing(SA),and Henry gas solubility optimization(HGSO)) and adaptive neuro-fuzzy inference system(ANFIS),named as MVO-ANFIS,EO-ANFIS,SA-ANFIS and HGSOANFIS ***,162 roof displacement events were investigated based on the characteristics of surrounding rocks,such as cohesion,Young’s modulus,density,shear strength,angle of internal friction,uniaxial compressive strength,quench durability index,rock mass rating,and tensile *** MVO-ANFIS,EO-ANFIS,SA-ANFIS and HGSO-ANFIS models were then developed and evaluated based on this dataset for predicting roof displacements in roadways of underground *** results indicated that the proposed intelligent techniques could accurately predict the roof displacements in roadways of underground mines with an accuracy in the range of 83%-92%.Remarkably,the SA-ANFIS model yielded the most dominant accuracy(i.e.92%).Based on the accurate predictions from the proposed techniques,the reinforced solutions can be timely suggested to ensure the stability of roadways during exploiting coal,especially in the underground coal mines exploited by the longwall mining.

关键词： Roof displacement Longwall mining Underground mine Physics-based optimization Risk assessment Mining hazards

Ecoregional variations of aboveground biomass and stand structure in evergreen broadleaved forests

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Journal of Forestry Research 2020年第5期31卷 1713-1722页

作者： Tran Van Do Mamoru Yamamoto Osamu Kozan Vo Dai Hai Phung Dinh Trung nguyen Toan Thang Lai Thanh Hai Vu Thanh Nam Trieu Thai Hung Hoang Van Thang Tran Duc Manh Cao Chi Khiem Vu Tien Lam nguyen Quang Hung Tran Hoang Quy Pham Quang Tuyen Trinh Ngoc Bon nguyen thi Thu Phuong Ninh Viet Khuong nguyen Van Tuan Dang thi Hai Ha Tran Hai Long Dang Van Thuyet Dang thinh Trieu nguyen Van thinh Tran Anh Hai Duong Quang Trung nguyen Van Bich Dinh Hai Dang Pham Tien Dung nguyen Huy Hoang Le thi Hanh Phan Minh Quang nguyen thi Thuy huong Hoang Thanh Son nguyen Thanh Son nguyen thi Van Anh nguyen thi Hoai Anh Pham Dinh Sam Hoang thi Nhung Hoang Van Thanh nguyen Huu thinh Tran Hong Van Ho Trung Luong Bui Kieu Hung Research Institute for Sustainable Humanosphere Kyoto UniversityUjiKyotoJapan Silviculture Research Institute Vietnamese Academy of Forest SciencesNorth Tu LiemHanoiVietnam Center for Southeast Asian Studies Kyoto UniversityKyotoJapan Vietnamese Academy of Forest Sciences North Tu LiemHanoiVietnam Vietnam Administration of Forestry No.2 Ngoc HaBa DinhHanoiVietnam

Biotic and abiotic factors control aboveground biomass(AGB)and the structure of forest *** study analyses the variation of AGB and stand structure of evergreen broadleaved forests among six ecoregions of Vietnam.A data set of 1731-ha plots from 52 locations in undisturbed old-growth forests was *** results indicate that basal area and AGB are closely correlated with annual precipitation,but not with annual temperature,evaporation or hours of *** area and AGB are positively correlated with trees>30 cm *** areas surveyed(52.6%)in these old-growth forests had AGB of 100–200 Mg ha^-1;5.2%had AGB of 400–500 Mg ha^-1,and 0.6%had AGB of>800 Mg ha^-*** percent of the areas surveyed had stand densities of 300–600 ***^-1,and 64%had basal areas of 20–40 m^2 ha^-*** is an important factor influencing the AGB of old-growth,evergreen broadleaved forests in *** causing the loss of large-diameter trees(e.g.,>100 cm DBH)affects AGB but may not seriously affect stand density.

关键词： Aboveground biomass Carbon storage Climatic variables Ecoregion Edaphic variables Oldgrowth forest

Studying Cosmological Time Variability of the Fine-Structure Constant from the Analysis of Quasar Spectra

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Journal of Modern Physics 2011年第6期2卷 533-537页

作者： Le Duc Thong nguyen thi Thu huong 不详

The article has been retracted due to the investigation of complaints received against it. The substantial portions of the text came from Le Duc Thong’s former article, 'New method of searching for cos-mological time variation of the fine-structure constant', which has also been retraced by Prog. Theor. Phys. because of plagiarism. The scientific community takes a very strong view on this matter and we treat all unethical behavior such as plagiarism seriously. this paper published in Vol.2 No.6 533-537, 2011, has been removed from this site.

关键词： Determination of Fundamental Constants Observation Cosmology