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Pham T.M.,University of Wollongong | Pham T.M.,HCMC University of Technology | Hadi M.N.S.,University of Wollongong
Journal of Composites for Construction | Year: 2014

The paper uses the membrane hypothesis to formulate the confining behavior of fiber-reinforced polymer (FRP) confined rectangular columns. A model was developed to calculate the strength of FRP confined rectangular concrete columns. The model was verified using a database of 190 FRP confined rectangular concrete columns. The database covers unconfined concrete strength between 18.3 and 55.2 MPa, and specimens with dimensions ranging from 79-305 mm and 100-305 mm for short and long sides, respectively. The performance of the proposed model shows a very good correlation with the experimental results. In addition, the strain distribution of FRP around the circumference of the rectangular sections was examined to propose an equation for predicting the actual rupture strain of FRP. The minimum corner radius of the sections is also recommended to achieve sufficient confinement. © 2013 American Society of Civil Engineers.


Pham T.M.,University of Wollongong | Pham T.M.,HCMC University of Technology | Hadi M.N.S.,University of Wollongong
Journal of Composites for Construction | Year: 2013

A new model is presented for calculating the axial strain of carbon fiber-reinforced polymer (CFRP)-confined concrete columns. An energy-balance approach is introduced to establish a relationship of the energy absorption between a confined concrete column and CFRP. The proposed model was verified using a large database collected from 167 CFRP-confined plain concrete specimens. This database contains 98 circular specimens with diameters ranging between 100 and 152 mm, and 69 square specimens having a side length ranging between 100 and 152 mm. The database covers unconfined concrete strengths from 20 to 50 MPa. The proposed model shows very good correlation with the experimental results. In addition, the proposed model also provides a comparative prediction of the strain of CFRP-confined concrete columns in two extreme cases, i.e., (1) insufficient confinement, and (2) heavy confinement, which are not usually well predicted by other models. © 2013 American Society of Civil Engineers.


Tran U.P.N.,HCMC University of Technology | Le K.K.A.,HCMC University of Technology | Phan N.T.S.,HCMC University of Technology
ACS Catalysis | Year: 2011

A highly porous zeolite imidazolate framework (ZIF-8) was synthesized by a solvothermal method, and used as an efficient heterogeneous catalyst for the Knoevenagel reaction. The solid catalyst was characterized using a variety of different techniques, including X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), dynamic laser light scattering (DLS), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), atomic absorption spectrophotometry (AAS), and nitrogen physisorption measurements. Quantitative conversion was achieved under mild conditions. The ZIF-8 catalyst could be facilely separated from the reaction mixture, and could be reused without significant degradation in catalytic activity. Furthermore, no contribution from homogeneous catalysis of active species leaching into reaction solution was detected. © 2011 American Chemical Society.


Phan N.T.S.,HCMC University of Technology | Le H.V.,HCMC University of Technology
Journal of Molecular Catalysis A: Chemical | Year: 2011

Superparamagnetic nanoparticles were synthesized following a microemulsion method, and functionalized with Schiff-base groups on the surface to form immobilized bidentate ligands. The functionalized nanoparticles were complexed with palladium acetate, affording the immobilized palladium complex catalyst with a palladium loading of 0.24 mmol/g. The catalyst was characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM), thermogravimetric analysis (TGA), Fourier transform infrared (FT-IR), atomic absorption spectrophotometry (AAS), and nitrogen physisorption measurements. The immobilized palladium complex was used as an efficient catalyst for the Sonogashira reaction of iodobenzene and phenylacetylene to form diphenylacetylene as the principal product without added phosphine ligands. Recovery of catalyst was facilely achieved by simple magnetic decantation. The immobilized palladium complex catalyst could be reused several times without significant degradation in catalytic activity. No contribution from homogeneous catalysis of active palladium species leaching into reaction solution was detected. © 2010 Elsevier B.V. All rights reserved.


Phan N.T.S.,HCMC University of Technology | Vu P.H.L.,HCMC University of Technology | Nguyen T.T.,HCMC University of Technology
Journal of Catalysis | Year: 2013

A crystalline porous metal-organic framework Cu2(BPDC) 2(BPY) was synthesized and characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), Fourier transform infrared (FT-IR) spectra, atomic absorption spectrophotometry (AAS), hydrogen temperature-programmed reduction (H2-TPR), and nitrogen physisorption measurements. The Cu-MOF could be used as an efficient heterogeneous catalyst for the copper-catalyzed cross-dehydrogenative coupling reaction of ethers with 2-carbonyl-substituted phenols. The Cu2(BPDC)2(BPY) exhibited significantly higher catalytic activity than that of other Cu-MOFs such as Cu3(BTC)2, Cu(BDC), and Cu(BPDC). The Cu-MOF also offered advantages over several copper salts such as CuCl2, CuCl, CuI, Cu(NO3)2, and Cu(OAc)2 in terms of the catalytic activity as well as the catalyst reusability. To the best of our knowledge, the cross-dehydrogenative coupling reaction of ethers with 2-carbonyl-substituted phenols via C-H activation under oxidative conditions using a heterogeneous catalyst was not previously mentioned in the literature. © 2013 Elsevier B.V. All rights reserved.


Phan N.T.S.,HCMC University of Technology | Nguyen T.T.,HCMC University of Technology | Vu P.H.L.,HCMC University of Technology
ChemCatChem | Year: 2013

A crystalline porous metal-organic framework Cu2(BPDC)2(BPY) (BPDC=4,4'-biphenyldicarboxylate, BPY=4,4'-bipyridine) was synthesized and characterized by several techniques including XRD, SEM, TEM, thermogravimetric analysis, FTIR, atomic absorption spectrophotometry, hydrogen temperature-programmed reduction, and nitrogen physisorption measurements. The Cu2(BPDC)2(BPY) could be employed as a heterogeneous catalyst for the copper-catalyzed cross-dehydrogenative coupling reaction of DMF with 2-substituted phenols to form organic carbamates through CH activation under oxidative conditions. The Cu2(BPDC)2(BPY) offered higher catalytic activity than common copper salts such as Cu(OAc)2, CuCl, CuCl2, CuI, and Cu(NO3)2 as well as other Cu-MOFs such as Cu3(BTC)2, Cu(BDC), and Cu(BPDC). The Cu2(BPDC)2(BPY) catalyst could be facilely separated from the reaction mixture, could be recovered and reused several times without significant degradation in catalytic activity. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Nguyen T.T.,HCMC University of Technology | Truong A.V.,HCMC University of Technology
International Journal of Electrical Power and Energy Systems | Year: 2015

This paper proposes a reconfiguration methodology based on a cuckoo search algorithm (CSA) for minimizing active power loss and the maximizing voltage magnitude. The CSA method is a new meta-heuristic algorithm inspired from the obligate brood parasitism of some cuckoo species which lay their eggs in the nests of other host birds of other species for solving optimization problems. Compared to other methods, CSA method has fewer control parameters and is more effective in optimization problems. The effectiveness of the proposed CSA has been tested on three different distribution network systems and the obtained test results have been compared to those from other methods in the literature. The simulation results show that the proposed CSA can be an efficient and promising method for distribution network reconfiguration problems. © 2014 Elsevier Ltd.


Nguyen L.T.L.,HCMC University of Technology | Le K.K.A.,HCMC University of Technology | Truong H.X.,HCMC University of Technology | Phan N.T.S.,HCMC University of Technology
Catalysis Science and Technology | Year: 2012

Crystalline zeolite imidazolate framework ZIF-9 was synthesized from the reaction of cobalt nitrate hexahydrate and benzimidazole by a solvothermal method, and was used as an efficient heterogeneous catalyst for the low temperature liquid phase Knoevenagel reaction. The solid catalyst was characterized by various techniques, including X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), dynamic laser light scattering (DLS), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), atomic absorption spectrophotometry (AAS), and nitrogen physisorption measurements. Excellent conversions were achieved under mild conditions. The ZIF-9 catalyst was easily isolated from the reaction mixture by simple filtration and reused several times without a significant degradation in activity. Moreover, there was no contribution from leached active species and conversion was only being possible in the presence of the solid catalyst. © 2012 The Royal Society of Chemistry.


Phan N.T.S.,HCMC University of Technology | Nguyen T.T.,HCMC University of Technology | Nguyen C.V.,HCMC University of Technology
Applied Catalysis A: General | Year: 2013

A highly porous metal-organic framework (MOF-199) was synthesized, and characterized by several methods including XRD, SEM, TEM, TGA, FT-IR, AAS, and nitrogen physisorption measurements. The MOF-199 was used as an efficient recyclable solid catalyst for the Ullmann-type reaction between aryl iodides and phenols to form diaryl ethers. High conversions were achieved for the transformation at the catalyst concentration of 5 mol%, in the presence of MeONa as a base. Due to the rare availability and the high cost, Cs 2CO3 should only be used for the case of deactivated aryl iodides or deactivated phenols. The MOF-199 catalyst could be facilely separated from the reaction mixture by simple filtration, and could be reused several times without a significant degradation in catalytic activity. The Ullmann-type reaction could only proceed in the presence of the solid MOF-199 catalyst, and the contribution from leached active species in the liquid phase, if any, was negligible. © 2013 Elsevier B.V.


Phan N.T.S.,HCMC University of Technology | Le K.K.A.,HCMC University of Technology | Phan T.D.,HCMC University of Technology
Applied Catalysis A: General | Year: 2010

A highly porous metal-organic framework (MOF-5) was synthesized by a solvothermal method, and used as an efficient heterogeneous acid catalyst for Friedel-Crafts alkylation reactions. The solid acid catalyst was characterized using a variety of different techniques, including X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), atomic absorption spectrophotometry (AAS), and nitrogen physisorption measurements. Quantitative conversion was achieved under mild conditions without the need for an inert atmosphere. The MOF-5 catalyst could be facilely separated from the reaction mixture, and could be reused several times without significant degradation in catalytic activity. Furthermore, no contribution from homogeneous catalysis of active acid species leaching into reaction solution was detected. © 2010 Elsevier B.V. All rights reserved.

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