The evolutionary dynamics of highly pathogenic avian influenza H5N1 in south-central Vietnam reveals multiple clades evolving from Chinese and Cambodian viruses

Nguyen, T.H.,Than, V.T.,Thanh, H.D.,Nguyen, V.Q.,Nguyen, K.H.,Nguyen, D.T.,Park, J.H.,Chung, I.S.,Jeong, D.G.,Chang, K.T.,Oh, T.K.,Kim, W. Pergamon Press 2015 Comparative immunology, microbiology and infectiou Vol.42 No.-

In Vietnam, highly pathogenic avian influenza (HPAI), such as that caused by H5N1 viruses, is the most highly contagious infectious disease that has been affecting domestic poultry in recent years. Vietnam might be an evolutionary hotspot and a potential source of globally pandemic strains. However, few studies have reported viruses circulating in the south-central region of Vietnam. In the present study, 47 H5N1-positive samples were collected from both vaccinated and unvaccinated poultry farms in the South Central Coast region of Vietnam during 2013-2014, and their genetic diversity was analyzed. A common sequence motif for HPAI virus was identified at HA-cleavage sites in all samples: either RERRRKR/G (clades 2.3.2.1c and 2.3.2.1a) or REGRRKKR/G (clade 1.1.2). Phylogenetic analysis of HA genes identified three clades of HPAI H5N1: 1.1.2 (n=1), 2.3.2.1a (n=1), and 2.3.2.1c (n=45). The phylogenetic analysis indicated that these Vietnamese clades may have evolved from Chinese and Cambodian virus clades isolated in 2012-2013 but are less closely related to the clades detected from the Tyva Republic, Bulgaria, Mongolia, Japan, and Korea in 2009-2011. Detection of the coexistence of virus clades 2.3.2.1 and the very virulent 1.1.2 in the south-central regions suggests their local importance and highlights concerns regarding their spread, both northwards and southwards, as well as the potential for reassortment. The obtained data highlight the importance of regular identification of viral evolution and the development and use of region-specific vaccines.

Structural Monitoring of a Defective Steel Beam Model Based on Image Changes in Power Spectral Density

Thanh Q. Nguyen,Tuan A. Nguyen,Thuy T. Nguyen 한국강구조학회 2022 International Journal of Steel Structures Vol.22 No.4

Using power-spectral density (PSD) analysis for structures, we evaluated defects following a widespread research trend. During the structure’s operation, PSD not only demonstrated its structural integrity at the time of surveying but also predicted future changes in the structure. The present research used changes in PSD as a key feature for monitoring a beam structure’s shearing patterns. Two shearing models—side shearing and shearing under the beam—revealed changes in the shape of PSD images that corresponded to degrees of defect in the diff erent shearing models. We applied these results to the monitoring of simple actual span structures over a long period of time. We monitored the structure’s operational status over time to examine the increased infl uence of structural defects based on signifi cant changes in the PSD regarding spectral amplitude and spectral width. The frequencies initially found in the high-frequency region of PSD tended to shift toward the lower-frequency regions before disappearing entirely. In the future, the results of this research may improve the evaluation of structural integrity through variations of PSD in vibrational spectral shapes.

Detecting Structural Deterioration: Investigating Changes in Power Spectral Density Using Deep Learning on Damaged Steel Beam Structures

Thanh Q. Nguyen,Tuan Anh Nguyen,Thuy T. Nguyen 한국강구조학회 2023 International Journal of Steel Structures Vol.23 No.4

The article focuses on detecting structural deterioration in damaged steel beam structures by investigating changes in power spectral density (PSD) using deep learning. To simulate damage, cracks are introduced to alter the stiffness of the steel beams. The study aims to replicate a realistic traffic scenario over bridges by measuring vibration signals obtained from acceleration sensors distributed along the steel beams. The article proposes a new parameter that tracks the deterioration of structures by analyzing the PSD when a moving load is applied to the steel beams with defects. Features generated from modified forms of the PSD are used to identify structural deterioration via steel beam damage and deep learning in a training dataset. The study found that differences in PSD shape caused by damage are more effective in detecting damage in various beam structures than those in the value of the fundamental beam frequency. Although the PSD method has been utilized in earlier research to identify steel beam defects, the use of deep learning in this study offers numerous novel and advantageous benefits.

Multiphase material topology optimization of Mindlin-Reissner plate with nonlinear variable thickness and Winkler foundation

Thanh T. Banh,Xuan Q. Nguyen,Michael Herrmann,Filip C. Filippou,Dongkyu Lee 국제구조공학회 2020 Steel and Composite Structures, An International J Vol.35 No.1

In typical, structural topology optimization plays a significant role to both increase stiffness and save mass of structures in the resulting design. This study contributes to a new numerical approach of topologically optimal design of Mindlin-Reissner plates considering Winkler foundation and mathematical formulations of multi-directional variable thickness of the plate by using multi-materials. While achieving optimal multi-material topologies of the plate with multi-directional variable thickness, the weight information of structures in terms of effective utilization of the material at the appropriate thickness location may be provided for engineers and designers of structures. Besides, numerical techniques of the well-established mixed interpolation of tensorial components 4 element (MITC4) is utilized to overcome a well-known shear locking problem occurring to thin plate models. The well-founded mathematical formulation of topology optimization problem with variable thickness Mindlin-Reissner plate structures by using multiple materials is derived in detail as one of main achievements of this article. Numerical examples verify that variable thickness Mindlin-Reissner plates on Winkler foundation have a significant effect on topologically optimal multi-material design results.

A constant strain triangle element oriented multi-material topology optimization with a moved and regularized Heaviside function

Xuan Q. Nguyen,Thanh T. Banh,Dongkyu Lee 국제구조공학회 2021 Structural Engineering and Mechanics, An Int'l Jou Vol.79 No.1

This study presents an optimal topology material distribution method in the framework of minimum compliance with a constraint on the total amount of multi-material using constant strain triangle (CST) elements and Moved and Regularized Heaviside Function (MRHF) filters. The sensitivity formulations for objective function and sensitivity for structures are derived in terms of multiphase design variables through triangle elements. Mathematical formulations of topology optimization problem solving the minimum compliance by using multiple materials are an alternating active-phase algorithm with a Gauss-Seidel version as an optimization model of optimality criteria. Moreover, MRHF that has the role of a filter in multiple materials is considered to produce obvious material distributions and improve the convergence of objective values. Some optimal topology results under the influence of rmin and filter are also investigated and verify the CST element-based multi-material topology optimization is appropriate to the use of MRHF and produces reasonable optimal results.

Synthesis of quinazolinones and benzazoles utilizing recyclable sulfated metal-organic framework-808 catalyst in glycerol as green solvent

Yen H. Vo,Thanh V. Le,Hieu D. Nguyen,Tuong A. To,Hiep Q. Ha,Anh T. Nguyen,Anh N.Q. Phan,Nam T.S. Phan 한국공업화학회 2018 Journal of Industrial and Engineering Chemistry Vol.64 No.-

Zirconium-based metal-organic framework MOF-808 was synthesized, and sulfated with aqueous sulfuric acid. Sulfated MOF-808 was utilized as a recyclable heterogeneous catalyst for the synthesis of quinazolinones from β-ketoesters and benzamides, and for the synthesis of benzimidazoles from β-ketoesters and o-phenylenediamines in glycerol as a green solvent. The sulfated MOF-808 catalyst was more active than many heterogeneous and homogeneous catalysts. The combination of the sulfated MOF-808 and glycerol was also effective for the reaction of o-aminothiophenols with β-diketones or cyclic β-diketones to produce benzothiazoles. To our best knowledge, MOF-based catalysts were not previously utilized as heterogeneous catalyst in glycerol as green solvent.

Effect of Process Parameters on Mechanical Strength of Fabricated Parts using the Fused Deposition Modelling Method

Lan P. T. Huynh,Huy A. Nguyen,Huy Q. Nguyen,Loc K. H. Phan,Thanh T. Tran 한국정밀공학회 2019 한국정밀공학회지 Vol.36 No.8

This study investigated the effects of process parameters on mechanical properties of fabricated parts of the Polylactic acid (PLA) materials using fused deposition modeling (FDM) in 3D printing Technology. First, Taguchi method in the design of experiment (DOE) approach was applied to generate a design matrix of three process parameters namely; printing speed, extrusion temperature and layer thickness. A L9 array with 9 specimens was used for fabrication under various process parameters by the Builder 3D printer. Tensile test was implemented and recorded in accordance with ASTM D368 standard. Achieved data were analyzed using the Minitab software to show the effect of each process parameter on mechanical properties. Secondly, a regression model was developed to predict the trend of response in case of change in setting of parameters and estimating the optimal set of process parameters which creates the strongest FDM parts. The achieved optimum parameters were used to validate the fabricated samples for tensile testing. According to the results, the best mechanical strength of fabricated parts was achieved with printing speed of 48 mm/s, extrusion temperature of 220 degree of celsius (C) and the layer thickness of 0.15 mm. Also, the extrusion temperature was the most influencing factor on ultimate tensile stress.

Comparison of various image fusion methods for impervious surface classification from VNREDSat-1

Hung V. Luu,Manh V. Pham,Chuc D. Man,Hung Q. Bui,Thanh T.N. Nguyen 국제문화기술진흥원 2016 International Journal of Advanced Culture Technolo Vol.4 No.2

Impervious surfaces are important indicators for urban development monitoring. Accurate mapping of urban impervious surfaces with observational satellites, such as VNREDSat-1, remains challenging due to the spectral diversity not captured by an individual PAN image. In this article, five multi-resolution image fusion techniques were compared for the task of classifting urban impervious surfaces. The result shows that for VNREDSat-1 dataset, UNB and Wavelet tranformation methods are the best techniques in reserving spatial and spectral information of original MS image, respectively. However, the UNB technique gives the best results when it comes to impervious surface classification, especially in the case of shadow areas included in non-impervious surface group.

Comparison of various image fusion methods for impervious surface classification from VNREDSat-1

Luu, Hung V.,Pham, Manh V.,Man, Chuc D.,Bui, Hung Q.,Nguyen, Thanh T.N. The International Promotion Agency of Culture Tech 2016 International Journal of Advanced Culture Technolo Vol.4 No.2

Impervious surfaces are important indicators for urban development monitoring. Accurate mapping of urban impervious surfaces with observational satellites, such as VNREDSat-1, remains challenging due to the spectral diversity not captured by an individual PAN image. In this article, five multi-resolution image fusion techniques were compared for the task of classifting urban impervious surfaces. The result shows that for VNREDSat-1 dataset, UNB and Wavelet tranformation methods are the best techniques in reserving spatial and spectral information of original MS image, respectively. However, the UNB technique gives the best results when it comes to impervious surface classification, especially in the case of shadow areas included in non-impervious surface group.