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Thủ Dầu Một, Vietnam

Hai N.M.,Thu Dau Mot University | Fellenius B.H.,2475 Rothesay Avenue
Geotechnical Special Publication | Year: 2014

Static loading tests using single-level O-cells were carried out in mid-2008 on two bored piles constructed at the Binh Loi Bridge, crossing the Saigon River at Ho Chi Minh City, Vietnam. The soils consist of surficial layers of soft clay and silt to 11 and 15 m depth on compact silty sand to about 55 m depth followed by dense to very dense silty sand. Two bored piles, 2.0 m and 1.5 m in diameter, were installed to 73.5 m and 73.0 m depth, respectively, and constructed using reverse circulation technique and bucket drill with casing advanced ahead of the hole. Drilling slurry was composed of polymer slurry for the 2.0-m diameter pile and bentonite slurry for the 1.5-m diameter pile. For both piles, the O-cell assembly was attached to a reinforcing cage lowered into the stabilized hole to 11.4 and 11.6 m, respectively, above the pile toe, five and two days after completing drilling and cleaning, respectively. Each reinforcing cage was instrumented with two pairs of diametrically opposed vibrating wire strain gauges at three levels below and five levels above the O-cell level. The static loading tests were performed 49 and 28 days, respectively, after the piles had been concreted. The strain-gauge records, when based on the nominal pile diameters, indicated Young's modulus values of about 25 GPa for the nominal cross-sections of the piles. Analysis of the records showed that residual load had developed during the wait time. The unit shaft resistance above the O-cell for the 2.0 m diameter, polymer-slurry constructed pile was moderately larger than that for the 1.5-m diameter, bentonite-slurry constructed pile. Detailed analysis showed the shaft resistance to be post-peak softening. The pile toe stress-movement responses were essentially linear and almost identical for the two piles. © 2014 American Society of Civil Engineers.

Hoang N.-T.D.,Ho Chi Minh City University of Pedagogy | Nguyen D.-A.P.,Thu Dau Mot University | Hoang V.-H.,Ho Chi Minh City University of Pedagogy | Le V.-H.,Ton Duc Thang University
Physica B: Condensed Matter | Year: 2016

Explicit expressions are given for analytically describing the dependence of the energy of a two-dimensional exciton on magnetic field intensity. These expressions are highly accurate with the precision of up to three decimal places for the whole range of the magnetic field intensity. The results are shown for the ground state and some excited states; moreover, we have all formulae to obtain similar expressions of any excited state. Analysis of numerical results shows that the precision of three decimal places is maintained for the excited states with the principal quantum number of up to n=100. © 2016 Elsevier B.V. All rights reserved.

Tang X.,Northwest University, China | Pang Y.,Northwest University, China | Ji P.,Northwest University, China | Gao P.,Northwest University, China | And 3 more authors.
Ecotoxicology and Environmental Safety | Year: 2016

Because of its high Cd uptake and translocation, lettuce is often used in Cd contamination studies. However, there is a lack of information on Cd accumulation in the above-ground parts of lettuce during the entire growing season. In this study, a field experiment was carried out in a Cd-contaminated area. Above-ground lettuce parts were sampled, and the Cd content was measured using a flame atomic absorption spectrophotometer (AAS). The results showed that the Cd concentration in the above-ground parts of lettuce increased from 2.70 to 3.62 mg kg-1 during the seedling stage, but decreased from 3.62 to 2.40 mg kg-1 during organogenesis and from 2.40 to 1.64 mg kg-1 during bolting. The mean Cd concentration during the seedling stage was significantly higher than that during organogenesis (a=0.05) and bolting (a=0.01). The Cd accumulation in the above-ground parts of an individual lettuce plant could be described by a sigmoidal curve. Cadmium uptake during organogenesis was highest (80% of the total), whereas that during bolting was only 4.34%. This research further reveals that for Rome lettuce: (1) the highest Cd content of above-ground parts occurred at the end of the seedling phase; (2) the best harvest time with respect to Cd phytoaccumulation is at the end of the organogenesis stage and (3) the organogenesis stage is the most suitable time to enhance phytoaccumulation efficiency by adjusting the root:shoot ratio. © 2015 Elsevier Inc.

Dinh T.T.H.,Thu Dau Mot University | Chu T.H.,Hanoi University | Nguyen Q.U.,Hanoi University
2015 IEEE Congress on Evolutionary Computation, CEC 2015 - Proceedings | Year: 2015

Transfer learning is a process in which a system can apply knowledge and skills learned in previous tasks to novel tasks. This technique has emerged as a new framework to enhance the performance of learning methods in machine learning. Surprisingly, transfer learning has not deservedly received the attention from the Genetic Programming research community. In this paper, we propose several transfer learning methods for Genetic Programming (GP). These methods were implemented by transferring a number of good individuals or sub-individuals from the source to the target problem. They were tested on two families of symbolic regression problems. The experimental results showed that transfer learning methods help GP to achieve better training errors. Importantly, the performance of GP on unseen data when implemented with transfer learning was also considerably improved. Furthermore, the impact of transfer learning to GP code bloat was examined that showed that limiting the size of transferred individuals helps to reduce the code growth problem in GP. © 2015 IEEE.

Nguyen T.-K.,Ho Chi Minh City University of Technology and Education | Nguyen B.-D.,Thu Dau Mot University
Journal of Sandwich Structures and Materials | Year: 2015

This paper presents a new higher-order shear deformation theory for static, buckling and free vibration analysis of functionally graded sandwich beams. In this theory, the axial displacement accounts for a third-order and inverse trigonometric distribution, and the transverse shear stress satisfies the traction-free boundary conditions on the top and bottom surfaces of the beams. Governing equations of motion are derived from the Hamilton’s principle for sandwich beams with homogeneous hardcore and softcore. Navier-type solution for simply-supported beams is developed to solve the problem. Numerical results are obtained to investigate effects of the power-law index, span-to-height ratio and thickness ratio of layers on the displacements, stresses, critical buckling load and frequencies. © 2015, © The Author(s) 2015.

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