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Study on the tunnel shape and soil-lining interaction influencing the lining behavior under seismic loading

Earthquake Engineering and Engineering vibration 2024年第4期23卷 845-862页

作者： van vi pham Ngoc Anh Do Piotr Osinski Ngoc Thai Do Daniel Dias Sustainable Development in Underground Engineering Research Team Hanoi University of Mining and GeologyHanoiVietnam Department of Underground and Mining Construction Faculty of Civil EngineeringHanoi University of Mining and GeologyHanoiVietnam Department of Geotechnical Engineering Institute of Civil EngineeringWarsaw University of Life Sciences-SGGWWarszawaPoland Laboratory 3SR Grenoble Alpes UniversityGrenoble 38400France

The response of tunnels subjected to seismic loading is a complex mechanism and depends not only on the seismic nature but also on tunnel structure and surrounding soil *** individual behavior of circular,rectangular,and sub-rectangular tunnels subjected to seismic loadings has already been studied in the *** the present research,two case scenarios of circular,rectangular tunnels and four sub-rectangular shaped tunnels,with similar cross-section areas,were adopted to perform a comprehensive numerical *** purpose of the study was to determine the mechanical behavior of tunnels of different shapes,depending upon seismic *** were performed by considering the influence of soil-lining interaction,soil parameters,and lining thickness,as well as lining *** were performed for no-slip and full-slip *** results indicate that the tunnel shape design is of great importance when regarding the mechanical behavior of the surrounding *** concerns no-slip as well as full-slip soil-lining interaction,especially when the lining is subjected to seismic ***,it is shown that changes in incremental bending moments for circular,rectangular and sub-rectangular tunnels that depend upon the soil-lining interaction conditions differ significantly.

关键词： tunnel shape soil-lining interaction seismic loading internal forces numerical analysis

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Prediction of Shear Bond Strength of Asphalt Concrete Pavement Using Machine Learning Models and Grid Search Optimization Technique

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Computer Modeling in Engineering & Sciences 2025年第1期142卷 691-712页

作者： Quynh-Anh Thi Bui Dam Duc Nguyen Hiep van Le Indra Prakash Binh Thai pham Civil Engineering Department University of Transport Technology54 Trieu KhucThanh XuanHanoi100000Vietnam DDG(R)Geological Survey of India Gandhinagar382010India

Determination of Shear Bond strength(SBS)at interlayer of double-layer asphalt concrete is crucial in flexible pavement *** study used three Machine Learning(ML)models,including K-Nearest Neighbors(KNN),Extra Trees(ET),and Light Gradient Boosting Machine(LGBM),to predict SBS based on easily determinable input ***,the Grid Search technique was employed for hyper-parameter tuning of the ML models,and cross-validation and learning curve analysis were used for training the *** models were built on a database of 240 experimental results and three input variables:temperature,normal pressure,and tack coat *** validation was performed using three statistical criteria:the coefficient of determination(R2),the Root Mean Square Error(RMSE),and the mean absolute error(MAE).Additionally,SHAP analysis was also used to validate the importance of the input variables in the prediction of the *** show that these models accurately predict SBS,with LGBM providing outstanding ***(Shapley Additive explanation)analysis for LGBM indicates that temperature is the most influential factor on ***,the proposed ML models can quickly and accurately predict SBS between two layers of asphalt concrete,serving practical applications in flexible pavement structure design.

关键词： Shear bond asphalt pavement grid search optimization machine learning

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New design of single-symbol decodable STBCs for MIMO communication system

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The Journal of China Universities of Posts and Telecommunications 2011年第6期18卷 44-50页

作者： pham van-bien Department of Communication Engineering Nanjing University of Science and Technology

Single-symbol maximum-likelihood （ML） decodable space-time block codes （SSDCs） can achieve a maximal symbol rate of 6/7 for multiple-input multiple-output （MIMO） communication system with five or six transmit antennas by using rate-efficient generalized coordinate interleaved orthogonal designs （RE-GCIODs）. Unfortunately, there are many zero entries in the eodeword matrix of RE-GCIODs. The zero entries result in high peak-to-average power ratio （PAPR） and also impose a severe constraint on hardware implementation. In this paper, for MIMO communication systems with five or six transmit antennas and one receive antenna, a new SSDC is proposed. By combining Alamouti code and orthogonal space-time block code （OSTBC）, desirable properties like RE-GCIODs can be achieved and are derived, including maximal symbol rate up to 6/7, full diversity and single-symbol ML decodability. Moreover, by reducing the number of zero entries in the codeword matrix, the peak-to-average power ratio （PAPR） of our proposed code is lower than RE-GCIODs. Simulation results show that the proposed codes outperform RE-GCIODs under peak power constraint while performing almost same under average power constraint.

关键词： space-time block code (STBC) full diversity MIMO PAPR

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New design of no-zero-entry single symbol ML decodable STBCs based on group precoding

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The Journal of China Universities of Posts and Telecommunications 2011年第4期18卷 70-75页

作者： pham van-bien Department of Communication Engineering Nanjing University of Science and Technology

In multiple-input multiple-output （MIMO） systems, space-time block codes （STBCs） from orthogonal designs （ODs） and coordinate interleaved orthogonal designs （CLOD） have been attracting wider attention due to their amenability for fast （single symbol） maximum-likelihood （ML） decoding, and full-rate with full-rank over quasi-static fading channels. However, most of these codes, for transmitting antennas more than 4, have large number of zero entries in their codeword matrix. Due to the zero entries in the design, the transmitting antennas need to be switched on and off imposing severe hardware constraints. To solve this problem, we propose a method to generate a new class of no-zero-entry single symbol maximum likelihood decodable STBCs （NZESSDCs）, which is based on coordinate interleaving and group precoding technique. The ability of the proposed group precoding based NZESSDCs （called G-NZESSDCs） on single symbol ML Decoding and full diversity are analyzed and derived. The performance evaluation is accomplished by numerical simulation and is compared with recently reported NZESSDCs （called C-NZESSDCs）. Compared with C-NZESSDCs, the proposed G-NZESSDCs have same bit-error-rate （BER） performance and better peak-to-average ratio （PAPR） performance.

关键词： space time block code full diversity MIMO

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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

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Numerical simulation of hydrodynamic characteristics and bedload transport in cross sections of two gravel-bed rivers based on one-dimensional lateral distribution method

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International Journal of Sediment Research 2020年第2期35卷 203-216页

作者： Chien pham van vivien Chua Department of River Engineering and Disaster Management Faculty of Hydrology and Water ResourcesThuyloi University Unite de Mod'elisation Mathematiques et Informatiquedes Systemesco Complexes (UMMISCO) JEAI WARMIRDSorbonne Universit'e Department of Civil and Environmental Engineering Faculty of EngineeringNational University of Singapore

Accurate evaluation and prediction of bedload transport are crucial in studies of fluvial hydrodynamic characteristics and river *** paper presents a one-dimensional numerical model based on the one-dimensional lateral distribution method(1 D-LDM) and six classic bedload transport formulae that can be used to simulate hydrodynamic characteristics and bedload transport discharge in cross *** gravel-bed rivers,*** Danube River located approximately 70 km downstream from Bratislava in Slovakia and the Tolten River in south of Chile are used as *** the 1 D-LDM,gravity,bed shear stress,turbulent diffusion,and secondary flow are included to allow for accurate predictions of flow velocity and consequently bed shear stress in the cross *** classic formulae were applied to evaluate the non-dimensional bedload transport rate,and the bedload transport discharge through a river cross section is obtained by integrating the bedload transport rate over the width of the cross *** results show that the root mean square error(RMSE) and mean absolute error(MAE) of velocity and water discharge were less than 8% of the observed magnitude,while the correlation coefficient between model predictions and observations was close to *** formulae proposed by Ashida and Michiue(1972),in which particle collision with the bed is taken into account,and by Camenen and Larson(2005),which allows for yielding a non-zero bedload transport rate even when the bed shear stress is smaller than the critical bed shear stress value,appeared to be more appropriate for predicting the observed bedload transport rate in the studied cross sections of two gravel-bed *** non-uniform sediment mixtures were considered,the bedload transport discharge through a cross-section could change considerably by up to 22.5% of the observed *** relations proposed by Ashida and Michiue(1972) and Egiazaroff(1965) for parameterizing the hiding factor yielded more

关键词： Bedload Gravel-bed river One-dimensional lateral distribution method Bedload transport discharge

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vibration characteristics of sandwich plates with an auxetic honeycomb core and laminated three-phase skin layers under blast load

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Defence Technology（防务技术） 2023年第6期24卷 148-163页

作者： Quoc-Hoa pham van Ke Tran Trung Thanh Tran Faculty of Engineering and Technology Nguyen Tat Thanh UniversityHo Chi Minh CityViet Nam Faculty of Mechanical Engineering Le Quy Don Technical UniversityHanoiViet Nam

In this article,vibration characteristics of sandwich plates with an auxetic honeycomb core and laminated three-phase skin layers subjected to blast load are ***-order ES-MITC3 element based on higher-order shear deformation theory(HSDT)to achieve the governing *** sandwich plates with the ultra-light feature of the auxetic honeycomb core layer(negative Poisson’s ratio)and reinforced by two laminated three-phase skin *** obtained results in our work are compared with other previously published to confirm accuracy and *** addition,the effects of parameters such as geometrical and material parameters on the vibration characteristics of sandwich plates with an auxetic honeycomb core and laminated three-phase skin layers are fully investigated.

关键词： Laminated three-phase Sandwich plate Auxetic honeycomb ES-MITC3 element High-order shear deformation theory

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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

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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

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Off-the-shelf mesenchymal stem cells from human umbilical cord tissue can significantly improve symptoms in COviD-19 patients: An analysis of evidential relations

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World Journal of Stem Cells 2020年第8期12卷 721-730页

作者： Phuc van pham Ngoc Bich Vu Stem Cell Institute University of ScienceHo Chi Minh 08000Viet Nam vietnam National University Ho Chi Minh 08000Viet Nam

Coronavirus disease-2019(COviD-19)has affected more than 200 countries *** disease has hugely affected healthcare systems as well as the economy to an extent never seen *** date,COviD-19 infection has led to about 165000 deaths in 150 *** present,there is no specific drug or efficient treatment for this *** this analysis based on evidential relationships of the biological characteristics of MSCs,especially umbilical cord(UC)-derived MSCs as well as the first clinical trial using MSCs for COviD-19 treatment,we discuss the use of UC-MSCs to improve the symptoms of COviD-19 in patients.

关键词： Coronavirus COviD-19 Mesenchymal stem cells Umbilical cord-derived mesenchymal stem cells

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