Ho Chi Minh City University of Natural Sciences

www.hcmus.edu.vn
Ho Chi Minh City, Vietnam

Ho Chi Minh City University of Science was re-founded in March 1996 following a split from Đại học Tổng hợp . The school has since been a member university of Vietnam National University, Ho Chi Minh City. It is entrusted with providing education at undergraduate and postgraduate levels and undertaking scientific research as well as technological transfer. Wikipedia.

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Nhan L.C.,Ho Chi Minh City University of Natural Sciences | Truong L.X.,University of Economics Ho Chi Minh City
Computers and Mathematics with Applications | Year: 2017

The main goal of this work is to study an initial-boundary value problem for a nonlinear pseudoparabolic equation with logarithmic nonlinearity. By using the potential well method and a logarithmic Sobolev inequality, we obtain results of existence or nonexistence of global weak solutions. In addition, we also provide sufficient conditions for the large time decay of global weak solutions and the finite time blow-up of weak solutions. © 2017 Elsevier Ltd.


Phong V.Q.,Ho Chi Minh City University of Natural Sciences | Van V.T.,Ho Chi Minh City University of Natural Sciences | Long H.N.,Vietnam Academy of Science and Technology
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

The electroweak phase transition is considered in the framework of the reduced minimal 3-3-1 model. The structure of the phase transition in this model is divided into two parts. The first part is the phase transition SU(3)→SU(2) at the TeV scale, and the second is SU(2)→U(1), which is like the standard model electroweak phase transition. When the mass of the neutral Higgs boson (h1) is taken to be equal to the LHC value, mh1=125 GeV, these phase transitions are first-order transitions; the mass of Z2 is about 4.8 TeV, and we find the region of parameter space with the first-order phase transition at the vρ0=246 GeV scale, leading to an effective potential where the mass of the charged Higgs boson is in the range 3.258 TeV


Cuong T.V.,University of Ulsan | Pham V.H.,University of Ulsan | Tran Q.T.,Ho Chi Minh City University of Natural Sciences | Hahn S.H.,University of Ulsan | And 3 more authors.
Materials Letters | Year: 2010

Photoluminescence (PL) and Raman studies have been performed to investigate the optical properties of graphene thin films prepared by chemical and thermal reductions of graphene oxide (GO). The G peak in Raman spectra red-shifted after reduction of GO. Thermal reduction resulted in a more red-shift of the G peak than chemical reduction. A strong intensity of the D peak indicated that the prepared graphene films have significant structural disorders. A blue-shifted emission in PL spectra suggested that sp2 clusters are embedded in a sp3 matrix that acts as a tunnel barrier, causing a strong fluctuation in the local band gap. © 2009 Elsevier B.V. All rights reserved.


Phuong N.L.,Ho Chi Minh City University of Natural Sciences | Ito K.,Kyushu University
Building and Environment | Year: 2015

Breathing is one of the most essential processes in the human body. The basic functions of breathing are to exchange gases (supplying oxygen from ambient air and removing carbon dioxide from the blood) and also to exchange heat and moisture through mucous surfaces of the airway. During an average lifetime, human beings experience significant exposure to indoor air and countless of contaminants/particles via inhalation. In this study, experimental and numerical results of flow fields in a realistic respiratory model were obtained. Flow patterns in a realistic replica model of the human respiratory tract were investigated with particle image velocimetry (PIV) under three constant breathing conditions; 7.5, 15 and 30 L/min. Computational fluid dynamics (CFD) analyses were conducted on turbulent models with boundary conditions corresponding to the experimental models. We used four RANS turbulence models to predict airflow in a realistic human airway model: two low Reynolds (Re) number-type k-ε turbulence models, RNG k-ε model, and the SST k-ω model. The CFD results were compared with PIV data and showed relatively good agreement in trachea region in all cases. © 2015.


Tran A.,University of Dalat | Truong T.,University of Dalat | Le B.,Ho Chi Minh City University of Natural Sciences
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2012

This paper shows a mathematical foundation for almost important features in the problem of discovering knowledge by association rules. The class of frequent itemsets and the association rule set are partitioned into disjoint classes by two equivalence relations based on closures. Thanks to these partitions, efficient parallel algorithms for mining frequent itemsets and association rules can be obtained. Practically, one can mine frequent itemsets as well as association rules just in the classes that users take care of. Then, we obtain structures of each rule class using corresponding order relations. For a given relation, each rule class splits into two subsets of basic and consequence. The basic one contains minimal rules and the consequence one includes in the rules that can be deducted from those minimal rules. In the rest, we consider association rule mining based on order relation min. The explicit form of minimal rules according to that relation is shown. Due to unique representations of frequent itemsets through their generators and corresponding eliminable itemsets, operators for deducting all remaining rules are also suggested. Experimental results show that mining association rules based on relation min is better than the ones based on relations of minmin and minMax in terms of reduction in mining times as well as number of basic rules. © 2012 Springer-Verlag.


Thanh Thuy H.T.,Ho Chi Minh City University of Natural Sciences | Nguyen T.D.,Ho Chi Minh City University of Natural Sciences
Environmental Science and Pollution Research | Year: 2013

Presently, many pharmaceuticals are listed as emerging contaminants since they are considered to be great potential threats to environmental ecosystems. These contaminants, thus, present significant research interest due to their extensive use and their physicochemical and toxicological properties. This review discusses a whole range of findings that address various aspects of the usage, occurrence, and potentially environmental risks of pharmaceuticals released from various anthropogenic sources, with emphasis on the aquatic systems in Vietnam. The published information and collected data on the usage and occurrence of antibiotics and synthetic hormone in effluents and aquatic systems of Vietnam is reported. This is followed by a potential ecological risk assessment of these pollutants. The extensive use of antibiotics and synthetic hormones in Vietnam could cause the discharge and accumulation of these contaminants in the aquatic systems and potentially poses serious risks for ecosystems. Vietnam is known to have extensively used antibiotics and synthetic hormones, so these contaminants are inevitably detected in aquatic systems. Thus, an appropriate monitoring program of these contaminants is urgently needed in order to mitigate their negative effects and protect the ecosystems. © 2013 Springer-Verlag Berlin Heidelberg.


Le T.H.,Ho Chi Minh City University of Natural Sciences | Van H.T.,Ho Chi Minh City University of Technology
Pattern Recognition | Year: 2012

Reference point plays an important role in fingerprint identification systems. The reference point is widely used for the fingerprint retrieval in large-scale databases. This paper proposes a novel algorithm for detecting a convex core point as a unique reference point consistently and accurately for all types of fingerprints. In order to detect robust core point candidates, a modified complex filter, called semi-radial symmetry filter, is proposed to detect correctly rotational symmetries of core points. Moreover, a vertical orientation variation feature, called VORIV feature, is proposed to remove spurious core points and concave core points. Therefore, the proposed technique computes the Variation and Symmetry Combined Energy (VSCOME). Then, the reference point is located by searching the global VSCOME maximum. The experimental results on the public database (FVC2004 DB1 set A) show that the proposed technique exhibits a very high robustness and gets the best performance in comparing with other approaches in literature. © 2012 Elsevier Ltd. All rights reserved.


Nguyen H.D.,Ho Chi Minh City University of Natural Sciences | Trinh B.T.D.,Ho Chi Minh City University of Natural Sciences | Nguyen L.-H.D.,Ho Chi Minh City University of Natural Sciences
Phytochemistry Letters | Year: 2011

Three new polyisoprenylated benzophenones, guttiferones Q-S, the known guttiferone I and four xanthones, dulxanthone A, 1,3,5-trihydroxy-6-methoxy-7- (3-methylbut-2-enyl)xanthone, 1,3,5-trihydroxy-13,13-dimethyl-2H-pyran[7,6-b] xanthen-9-one and 1,3-dihydroxy-5,6-dimethoxy-7-(3-methylbut-2-enyl)xanthone, as well as trimethyl citrate, were isolated from the pericarp of Garcinia cochinchinensis collected in Vietnam. Their structures were elucidated using spectroscopic methods (mainly 1-D and 2-D NMR). All the guttiferones were tested for their cytotoxicity towards three human cancer cell lines, MCF-7, Hela, and NCI-H460. Among the tested compounds, guttiferone Q showed potent cytotoxicity, having IC50 values in the range of 2.74-4.04 μg/ml, against the investigated cells. © 2011 Phytochemical Society of Europe.


Noh S.,Gwangju Institute of Science and Technology | Choi M.,Gwangju Institute of Science and Technology | Kim E.,Gwangju Institute of Science and Technology | Dan N.P.,Ho Chi Minh City University of Technology | And 4 more authors.
Geochimica et Cosmochimica Acta | Year: 2013

The lower Mekong and Saigon River Basins are dominated by distinctive monsoon seasons, dry and rainy seasons. Most of the Mekong River is a freshwater region during the rainy season, whereas during the dry season, salt water intrudes approximately 70km inland. To understand the role of salinity intrusion controlling Hg behavior in the Mekong and Saigon River Basins, Hg and monomethylmercury (MMHg) in surface water and sediment of the Mekong River and in sediment of the Saigon River were investigated in the dry season. Sediment Hg distribution, ranging from 0.12 to 0.76nmolg-1, was mainly controlled by organic carbon distribution in the Mekong River; however, the location of point sources was more important in the Saigon River (0.21-0.65nmolg-1). The MMHg concentrations in Mekong (0.16-6.1pmolg-1) and Saigon (0.70-8.7pmolg-1) sediment typically showed significant increases in the estuarine head, with sharp increases of acid volatile sulfide. Unfiltered Hg (4.6-222pM) and filtered Hg (1.2-14pM) in the Mekong River increased in the estuarine zone due to enhanced particle loads. Conversely, unfiltered MMHg (0.056-0.39pM) and filtered MMHg (0.020-0.17pM) was similar between freshwater and estuarine zones, which was associated with mixing dilution of particulate MMHg by organic- and MMHg-depleted resuspended sediment. Partitioning of Hg between water and suspended particle showed tight correlation with the partitioning of organic carbon across study sites, while that of MMHg implied influences of chloride: enhanced chloride in addition to organic matter depletion decreased particulate MMHg in the estuarine zone. Primary production was an important determinant of inter-annual variation of particulate Hg and sediment MMHg. The bloom year showed relatively low particulate Hg with low C/N ratio, indicating biodilution of Hg. In contrast, the percentage of MMHg in sediment increased significantly in the bloom year, likely due to greater availability of metabolizable fresh organic matter. The overall results emphasize that Hg behavior in the lower Mekong River Basin is strongly connected to the local monsoon climate, via alterations in particle loads, biological productivity, and availability of sulfate, chloride and organic matter. © 2012 Elsevier Ltd.


Cuong T.V.,University of Ulsan | Pham V.H.,University of Ulsan | Shin E.W.,University of Ulsan | Chung J.S.,University of Ulsan | And 5 more authors.
Applied Physics Letters | Year: 2011

Temperature-dependent photoluminescence (PL) of graphene oxide (GO) reduced with hydrazine and heat has been measured to investigate the effect of reduction type on the bandgap of the reduced GO. Nitrogen functionalities formed in the hydrazine-treated GO were responsible for a strong localization of carriers that caused in a fluctuation in PL peak position with temperature. The intensity of C-OH peak was relatively low in the heat-treated GO, indicating that raising temperature facilitated the removal of hydroxyl groups, resulting in larger sp2 domain size and smaller bandgap energy. © 2011 American Institute of Physics.

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