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ITÔDIFFERENTIAL REPRESENTATION OF SINGULAR STOCHASTIC VOLTERRA INTEGRAL EQUATIONS

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Acta Mathematica Scientia 2020年第6期40卷 1989-2000页

作者： nguyen Tien DUNG Division of Computational Mathematics and Engineering Institute for Computational ScienceTon Duc Thang UniversityHo Chi Minh CityVietnam Faculty of Mathematics and Statistics Ton Duc Thang UniversityHo Chi Minh CityVietnam

In this paper we obtain an Itôdifferential representation for a class of singular stochastic Volterra integral *** an application,we investigate the rate of convergence in the small time central limit theorem for the ... 详细信息

关键词： stochastic integral equation Itôformula central limit theorem

Low-tension gas process in high-salinity and low-permeability reservoirs

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Petroleum Science 2020年第5期17卷 1329-1344页

作者： Alolika Das Nhut nguyen Quoc P.nguyen Hildebrand Department of Petroleum and Geosystems Engineering University of Texas at Austin200 E.Dean KeetonAustinTX 78712USA

Polymer-based EOR methods in low-permeability reservoirs face injectivity issues and increased fracturing due to near wellbore plugging,as well as high-pressure gradients in these *** may cause pore blockage and undergo shear degradation and even oxidative degradation at high temperatures in the presence of very hard ***-tension gas(LTG) flooding has the potential to be applied successfully for low-permeability carbonate reservoirs even in the presence of high formation brine *** LTG flooding,the interfacial tension between oil and water is reduced to ultra-low values(10^-3 dyne/cm) by injecting an optimized surfactant formulation to maximize mobilization of residual oil ***(nitrogen,hydrocarbon gases or C02) is co-injected along with the surfactant slug to generate in situ foam which reduces the mobility ratio between the displaced(oil) and displacing phases,thus improving the displacement efficiency of the *** this work,the mechanism governing LTG flooding in low-permeability,high-salinity reservoirs was studied at a microscopic level using microemulsion properties and on a macroscopic scale by laboratory-scale coreflooding *** main injection parameters studied were injected slug salinity and the interrelation between surfactant concentration and injected foam quality,and how they influence oil mobilization and displacement *** assessment of the results was performed by studying oil recovery,oil fractional flow,oil bank breakthrough and effluent salinity and pressure drop characteristics.

关键词： Enhanced oil recovery Foam Microemulsion Carbonate High salinity Low permeability

Numerical investigation of the influence of casting techniques on fiber orientation distribution in ECC

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Frontiers of Structural and Civil Engineering 2022年第11期16卷 1424-1435页

作者： Chung nguyen VAN Hai TRAN THANH Thuc Nhu nguyen Jianchun LI Faculty of Civil Engineering Ho Chi Minh City University of Technology and EducationHo Chi Minh 721400Vietnam School of Civil and Environmental Engineering University of Technology SydneySydneyNSW 2007Australia School of Civil Engineering Hue Industrial CollegeHue 49120Vietnam

Engineered cementitious composites(ECC),also known as bendable concrete,were developed based on engineering the interactions between fibers and cementitious *** orientation of fibers,in this regard,is one of the major factors influencing the ductile behavior of this *** this study,fiber orientation distributions in ECC beams influenced by different casting techniques are evaluated via numerical modeling of the casting *** casting directions and two casting positions of the funnel outlet with beam specimens are modeled using a particle-based smoothed particle hydrodynamics(SPH)*** this SPH approach,fresh mortar and fiber are discretized by separated mortar and fiber particles,which smoothly interact in the computational domain of *** movement of fiber particles is monitored during the casting ***,the fiber orientations at different sections of specimens are determined after the fresh ECC stops flowing in the *** simulation results show a significant impact of the casting direction on fiber orientation distributions along the longitudinal wall of beams,which eventually influence the flexural strength of *** addition,casting positions show negligible influences on the orientation distribution of fibers in the short ECC beam,except under the pouring position.

关键词： ECC fiber orientation distribution casting direction casting position

Overexpression of Arabidopsis Sorting Nexin AtSNX2b Inhibits Endocytic Trafficking to the Vacuole

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Molecular Plant 2008年第6期1卷 961-976页

作者： nguyen Q. Phan Department of Genetics Development and Cell Biology Iowa State University Ames IA 50011 USA Interdepartmental Genetics Program Iowa State University Ames IA 50011 USA Plant Sciences Institute Iowa State University Ames IA 50011 USA

Sorting nexins are conserved proteins that function in vesicular trafficking and contain a characteristic phox homology （PX） domain. Here, we characterize the ubiquitously expressed Arabidopsis thaliana sorting nexin AtSNX2b. Sub-cellular fractionation studies indicate that AtSNX2b is peripherally associated with membranes. The AtSNX2b PX domain binds to phosphatidylinositol 3-phosphate in vitro and this association is required for the localization of GFPAtSNX2b to punctate structures in vivo, identified as the trans-Golgi network, prevacuolar compartment and endosomes. Overexpression of GFP-tagged AtSNX2b produces enlarged GFP-labeled compartments that can also be labeled by the endocytic tracer FM4-64. Endocytic trafficking of FM4-64 to the vacuole is arrested in these GFP-AtSNX2b compartments, and similar FM4-64-accumulating compartments are seen upon overexpression of untagged AtSNX2b. This suggests that exit of membrane components from these enlarged or aggregated endosomes is inhibited. Vacuolar proteins containing an N-terminal propeptide, but not those with a C-terminal propeptide, are also present in these enlarged compartments. We hypothesize that AtSNX2b is involved in vesicular trafficking from endosomes to the vacuole.

关键词： phox homology Overexpression Vacuole

A stable CS-FEM for the static and seismic stability of a single square tunnel in the soil where the shear strength increases linearly with depth

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Journal of Rock Mechanics and Geotechnical Engineering 2022年第4期14卷 1253-1265页

作者： H.C.nguyen L.nguyen-Son Department of Civil and Environmental Engineering Imperial College LondonLondonUK Department of Civil Engineering and Industrial Design University of LiverpoolLiverpoolUK Faculty of Civil Engineering Ho Chi Minh City University of Technology(HUTECH)Ho Chi Minh CityViet Nam

A numerical procedure using a stable cell-based smoothed finite element method(CS-FEM)is presented for estimation of stability of a square tunnel in the soil where the shear strength increases linearly with *** kinematically admissible displacement fields are approximated by uniform quadrilateral elements in conjunction with the strain smoothing technique,eliminating volumetric locking issues and the singularity associated with the MohreCoulomb ***,a rich set of simulations was performed to compute the static stability of a square tunnel with different geometries and soil *** presented results are in excellent agreement with the upper and lower bound solutions using the standard finite element method(FEM).The stability charts and tables are given for practical use in the tunnel design,along with a newly proposed formulation for predicting the undrained stability of a single square ***,the seismic stability number was computed using the present numerical *** results reveal that the seismic stability number reduces with an increasing value of the horizontal seismic acceleration(a_(h)),for both cases of the weightless soil and the soil with unit ***,the link between the static and seismic stability numbers is described using corrective factors that represent reductions in the tunnel stability due to seismic *** is shown from the numerical results that the corrective factor becomes larger as the unit weight of soil mass increases;however,the degree of the reduction in seismic stability number tends to reduce for the case of the homogeneous ***,this advanced numerical procedure is straightforward to extend to three-dimensional(3D)limit analysis and is readily applicable for the calculation of the stability of tunnels in highly anisotropic and heterogeneous soils which are often encountered in practice.

关键词： Tunnels Stability Limit analysis Cell-based smoothed finite element method (CS-FEM) Second-order cone programming(SOCP)

Examination of n-T_(9) conditions required by N=50,82,126 waiting points in r-process

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Communications in Theoretical Physics 2021年第10期73卷 147-157页

作者： nguyen Duy Ly nguyen Ngoc Duy nguyen Kim Uyen Vinh N T Pham Faculty of Fundamental Sciences Vanlang UniversityHo Chi Minh City 700000Vietnam Department of Physics Sungkyunkwan UniversitySuwon 16419Republic of Korea Department of Physics Ho Chi Minh City University of EducationHo Chi Minh City 700000Vietnam

We examined the conditions of neutron density(n) and temperature(T9) required for the N = 50, 82,and 126 isotopes to be waiting points(WP) in the r-process. The nuclear mass based on experimental data presented in the AME2020 database(AME and AME ± Δ) and that predicted using FRDM,WS4, DZ10, and KTUY models were employed in our estimations. We found that the conditions required by the N = 50 WP significantly overlap with those required by the N = 82 ones, except for the WS4 model. In addition, the upper(or lower) bounds of the n-T9 conditions based on the models are different from each other due to the deviations in the two-neutron separation *** standard deviations in the nuclear mass of 108 isotopes in the three N = 50, 82, and 126 groups are about rms = 0.192 and 0.434 Me V for the pairs of KTUY-AME and WS4-KTUY models,respectively. We found that these mass uncertainties result in a large discrepancy in the nn-T_(9) conditions, leading to significant differences in the conditions for simultaneously appearing all the three peaks in the r-process abundance. The newly updated FRDM and WS4 calculations can give the overall conditions for the appearance of all the peaks but vice versa for their old versions in a previous study. The change in the final r-process isotopic abundance due to the mass uncertainty is from a few factors to three orders of magnitude. Therefore, accurate nuclear masses of the r-process key nuclei, especially for 76 Fe,81Cu,127Rh,132Cd,192Dy, and 197Tm, are highly recommended to be measured in radioactive-ion beam facilities for a better understanding of the r-process evolution.

关键词： neutron capture r-process nuclear mass isotopic abundance precise mass measurement

On a Monotone Ⅲ-posed Problem

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Acta Mathematica Sinica,English Series 2005年第5期21卷 1001-1004页

作者： nguyen BUONG Vietnamese Academy of Science and Technology Institute of Information Technology18Hoang Quoc Viet.q.Cau GigyHa NoiVietnam

A class of a posteriori parameter choice strategies for the operator version of Tiknonov regularization （including variants of Morozov＇s and Arcangeli＇s methods） is proposed and used in investigating the rate of convergence of the regularized solution for ill-posed nonlinear equation involving a monotone operator in Banach space.

关键词： Monotone operators Tikhonov regularization

Hyperstatic reaction method for calculations of tunnels with horseshoe-shaped cross-section under the impact of earthquakes

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Earthquake Engineering and Engineering Vibration 2020年第1期19卷 179-188页

作者： Thanh nguyen Chi Gospodarikov Alexandr Saint Petersburg Mining University Saint PetersburgRussia Federation Hanoi University of Mining and Geology HanoiVietnam

Tunnels are now an integral part of the infrastructure in major cities around the world. For many reasons, these tunnels have horseshoe-shaped cross-sections with round top and flat bottom. This paper presents some improvements to the use of the Hyperstatic Reaction Method-HRM for analysing tunnels with horseshoe-shaped cross-sections when these tunnels operate under the influence of earthquakes, particularly in cases when the tunnel lining is a continuous lining. The analysis used parameters of a tunnel from the Hanoi metro system, as well as parameters of the strongest earthquake that may occur in the central Hanoi area in the improved HRM and 2 D numerical methods using the ABAQUS software. On the basis of the results obtained, the paper gives conclusions about the HRM methodology when it is used to calculate tunnels that have horseshoe cross-sections operating under the influence of earthquakes.

关键词： hyperstatic reaction method earthquake horseshoe cross-section impact tunnel

Modeling bending behavior of shape memory alloy wire-reinforced composites: Semi-analytical model and finite element analysis

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Chinese Journal of Aeronautics 2021年第8期34卷 176-191页

作者： nguyen Van VIET Wael ZAKI Department of Mechanical Engineering Khalifa University of Science and TechnologyAbu DhabiUnited Arab Emirates

In this study,we propose a novel and simple exact semi-analytical model for superelastic Shape Memory Alloy(SMA)wire reinforced composites subjected to bending *** order to study the mechanical response of the composite during loading/unloading,a Representative Volume Element(RVE)is extracted to examine the bending response of the *** moment–curvature,and shear force-shear strain relations are derived based on a 3-Dimensional(3 D)thermomechanical SMA model and Timoshenko beam *** composite Simpson’s rule is adopted to numerically solve the exact analytical moment–curvature and shear force-shear strain *** including the moment–curvature response,axial stress distribution along the vertical and longitudinal directions,martensite volume fraction,and the tip deflection are reported and validated against 3 D finite element *** influence of temperature,martensite volume fraction distribution,and matrix stiffness on the mechanical performance of the composite is also *** particular,the composite is found to behave superelastically under certain conditions of temperature,SMA volume fraction,and elastic stiffness of the *** behavior is advantageous in applications requiring large recoverable strains or high energy dissipation density.

关键词： Bending Finite element analysis Modelling Phase transformation Shape memory alloy reinforced composite Superelasticity