University of Technical Education Hochiminh City

Vân Tùng, Vietnam

University of Technical Education Hochiminh City

Vân Tùng, Vietnam

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Hwang H.-Y.,National Taipei University of Technology | Nghiem N.Q.,National Taipei University of Technology | Nghiem N.Q.,University of Technical Education Hochiminh city
Applied Mechanics and Materials | Year: 2013

Spot welds have been widely used in vehicle body assembly, and can affect the performance of a vehicle. This paper studies the mechanical properties of spot weld and utilizes those properties in the numerical simulation to predict the failure behavior of a spot-welded component. The mechanical properties of a spot weld are not easy to obtain due to the size of spot weld, and the non-uniformity around the weld zone. The study utilized the hardness measured on and around the spot weld, heat treated samples with the same hardness, and then performed the tensile tests on those heat treated specimens to obtain the corresponding mechanical properties. With those testing data, the numerical simulation model was then created based on the properties obtained. A single-spot-welded part was used to correlate the results of hardware tests and numerical simulation. The study compared the results of three different modeling schemes with those of the hardware test. The results showed that the simulation model with material properties assigned to their corresponding region provided better correlation with the hardware testing results. © (2013) Trans Tech Publications, Switzerland.


Duong T.,Hunan University | Duong T.,Industry University of Hochiminh City | Jiangang Y.,Hunan University | Truong V.,University of Technical Education Hochiminh City
International Journal of Electrical Power and Energy Systems | Year: 2013

In the deregulated power industry, private power producers are increasing rapidly to meet the increase demand. The purpose of the transmission network is to pool power plants and load centers in order to supply the load at a required reliability, maximum efficiency and at lower cost. As power transfer increases, the power system becomes increasingly more difficult to operate and insecure with unscheduled power flows and higher losses. FACTS devices such as Thyristor Controlled Series Compensator (TCSC) can be very effective to power system security. Proper location of TCSC plays key role in optimal power flow solution and enhancement of system performance without violating the security of the system. This paper applied min cut algorithm to select proper location of TCSC for secured optimal power flow under normal and contingencies operating condition. Proposed method requires a two-step approach. First, the optimal location of the TCSC in the network must be ascertained by min cut algorithm and then, the optimal power flow (OPF) with TCSC under normal and contingencies operating condition is solved. The proposed method was tested and validated for locating TCSC in Six bus, IEEE 14-, IEEE-30 and IEEE-118 bus test systems. Results show that the proposed method is good to select proper location of TCSC for secured OPF.


Dao P.T.A.,University of Technical Education Hochiminh City | Hai N.X.,University of Science | Nhan N.T.,University of Science | Le Quan T.,University of Science | Mai N.T.T.,University of Science
Natural Product Sciences | Year: 2012

Among 90 Vietnamese medicinal plant extracts investigated for their antioxidant activity by DPPH assay at various concentrations from 10 - 100 μg/mL, 67 showed an inhibition rate over 50% at 100 μg/mL; 47 had greater than 50% inhibition at 50 μg/mL; 17 showed over 50% inhibition at 25 μg/mL. 8 extracts which exhibited strong inhibitory activity more than 50% inhibition at 10 μg/mL were further tested for lipid peroxidation inhibition by TBA assay. They displayed activity with IC50 values from 30.6 to 158.9 μg/mL. Until now, this is the first report on antioxidant activity of the female flower of Borassus flabellifer, and the stem of Combretum latifolium, Embelia ribes, Spatholobus parviflorus, and Tetrastigma erubescens. Fractionations of the EtOAc extract prepared from S. parviflorus led to the isolation of protocatechuic acid (1), ferulic acid (2), epicatechin (3), and gallic acid (4). These compounds showed significant DPPH inhibitory activity with IC50 values from 6.5 to 23.6 μM.


Dao P.T.A.,University of Technical Education Hochiminh City | Quan T.L.,University of Science | Mai N.T.T.,University of Science
Natural Product Sciences | Year: 2014

A new natural product, tetrastigmol A (1), and several known compounds as flavonoids (2 - 8), steroids (9 - 10), bergenin and its derivative (11 - 12), stilbens (13 - 15), lignan (16), benzenecarboxylic derivative (17) and two norisoprenoid (18 - 19) were isolated from the stem of Tetrastigma erubescens Planch. (Vitateae). Their structures were determined on the basis of NMR spectroscopic data. This is the first report on chemical constituents of this plant. Compounds 1, 6 - 8 and 12 - 15 showed strong antioxidant activity using two methods including DPPH (1,1-diphenyl-2-picrylhydrazyl) free radical scavenging and lipid peroxidation inhibitory assays.


Duong T.,Hunan University | Duong T.,Ho Chi Minh City University of Technology | Jiangang Y.,Hunan University | Truong V.,University of Technical Education Hochiminh City
International Journal of Electrical Power and Energy Systems | Year: 2014

Due to the growth of electricity demands and transactions in power markets, existing power networks need to be improved in order to increase their loadability. Series FACTS devices such as Thyristor controlled series compensators (TCSC) can be installed on transmission lines to enhance the system loadability through changing line reactance. The proper location and the best setting of TCSC is a key for achieving maximum system loadability and optimal installation cost of TCSC devices. This paper has applied the minimum cut methodology on the power system to determine the most suitable locations for the installed TCSC as well as using Kirchhoff's law of current to establish clearly formulation for determining the best setting of TCSC devices. Simulations are performed on IEEE 6-bus, IEEE 30-bus and IEEE 118-bus systems. The results obtained show that the proposed method is capable of finding the location, quantity and size of TCSC in such effective way for enhancing system loadability and minimum installation cost of TCSC devices. Using this method, search space and the number of TCSC devices required will be significantly decreased. © 2014 Elsevier Ltd. All rights reserved.

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