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Deval Prasad Bhattarai,Ganesh Prasad Awasthi,Bikendra Maharjan,Joshua Lee,김범수,박찬희,김철상 한국공업화학회 2019 Journal of Industrial and Engineering Chemistry Vol.77 No.-
Herein, we report the synthesis of polythiophene nanoparticles (PTh-NPs) by surfactant-free chemicaloxidative polymerization of thiophene at 37 C using ammonium persulphate as oxidant. PTh-NPssynthesized without surfactant were compared to those with surfactant in terms of surface morphology,crystallinity, cytotoxicity and some other aspects. Thermogravimetric analysis showed a good thermalstability of as-synthesized PTh-NPs. In vitro biomineralization revealed the nucleation of calcium andphosphate onto the NPs. Cytotoxicity of PTh-NPs was evaluated by measuring cell viability of preosteoblastMC3T3-E1 and PC12 cell lines. PTh-NPs synthesized without using surfactant exhibited bettercell viability compared to those with surfactant.
Devals, Christophe,Vu, Thi C.,Guibault, Francois Korean Society for Fluid machinery 2015 International journal of fluid machinery and syste Vol.8 No.3
This paper presents a CFD-based methodology for the prediction of guide vane torque in hydraulic turbine distributor for aligned and misaligned configurations. A misaligned or desynchronized configuration occurs when the opening angle of one guide vane differs from the opening angle of all other guide vanes, which may lead to a torque increase on neighbouring guide vanes. A fully automated numerical procedure is presented, that automates computations for a complete range of operation of a 2D or 3D distributor. Results are validated against laboratory measurements.
3D Casing-Distributor Analysis for Hydraulic Design Application
Devals, Christophe,Zhang, Ying,Dompierre, Julien,Vu, Thi C.,Mangani, Luca,Guibault, Francois Korean Society for Fluid machinery 2015 International journal of fluid machinery and syste Vol.8 No.3
Nowadays, computational fluid dynamics is commonly used by design engineers to evaluate and compare losses in hydraulic components as it is less expensive and less time consuming than model tests. For that purpose, an automatic tool for casing and distributor analysis will be presented in this paper. An in-house mesh generator and a Reynolds Averaged Navier-Stokes equation solver using the standard $k-{\omega}$ shear stress transport (SST) turbulence model will be used to perform all computations. Two solvers based on the C++ OpenFOAM library will be used and compared to a commercial solver. The performance of the new fully coupled block solver developed by the University of Lucerne and Andritz will be compared to the standard 1.6ext segregated simpleFoam solver and to a commercial solver. In this study, relative comparisons of different geometries of casing and distributor will be performed. The present study is thus aimed at validating the block solver and the tool chain and providing design engineers with a faster and more reliable analysis tool that can be integrated into their design process.
Bhattarai, Deval Prasad,Shrestha, Sita,Shrestha, Bishnu Kumar,Park, Chan Hee,Kim, Cheol Sang Elsevier 2018 CHEMICAL ENGINEERING JOURNAL -LAUSANNE- Vol.350 No.-
<P><B>Abstract</B></P> <P>In this work, titanium oxide nanotubes (TNTs) have been developed via electrochemical anodization process, followed by potentiostatic electropolymerization of aniline monomer to achieve TNTs coated polyaniline (PANI) substrate using cyclic voltammetry method at low temperature. Prior to PANI decoration, crystallinity of titanium oxide nanotubes (TNTs) was obtained by annealing the substrate at 420 °C for two hours. The physicochemical characterization of the as-prepared TNTs and TNTs/PANI were analyzed using FE-SEM, AFM, XRD and FT-IR techniques. A coating of PANI forms a sheath around the nanotubes and protects them from metallic corrosion. Large surface area to volume ratio of TNTs showed improved properties in biocompatibility, thermal stability, electrical conductivity, biomineralization and hydrophilicity after coating with PANI, an electroactive conducting polymer. In addition, the TNTs/PANI exhibited an effective platform to enhance attachment, development and proliferation of preosteoblast (MC3T3-E1) cells which opens a new avenue in the realm of bone tissue engineering. The cells’ morphology to their surrounding topography, development, or proliferation, and osteogenic-related markers (such as ALP increased level, collagen type I secretion) were also analysed. Such types of surface modification tailoring on titanium nanotubes could offer a potential and a promising scaffold material for biomedical implantation in bone tissue engineering.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A uniform surface topography of titanium nanotubes (TNTs) were fabricated through anodization. </LI> <LI> The TNTs were coated with polyaniline (PANI) via cyclic voltammetric technique. </LI> <LI> The bioinspired TNTs/PANI showed an effective antibacterial property. </LI> <LI> Highly biocompatible TNTs/PANI scaffolds enhanced the proliferation of pre-osteoblast cells. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Hosseinimanesh, Hossein,Devals, Christophe,Nennemann, Bernd,Guibault, Francois Korean Society for Fluid machinery 2015 International journal of fluid machinery and syste Vol.8 No.3
No-load speed is an important performance factor for the safe operation of hydropower systems. In turbine design, the manufacturers must conduct several model tests to calculate the accurate value of no-load speed for the complete range of operating conditions, which are expensive and time-consuming. The present study presents steady and unsteady methods for calculating no-load speed of a Francis turbine. The steady simulations are implemented using a commercial flow solver and an iterative algorithm that relies on a smooth relation between turbine torque and speed factor. The unsteady method uses unsteady RANS simulations that have been integrated with a user subroutine to compute and return the value of runner speed, time step and friction torque. The main goal of this research is to evaluate and compare the two methods by calculating turbine dynamic parameters for three test cases consisting of high and medium head Francis turbines. Overall, the numerical results agreed well with experimental data. The unsteady method provided more accurate results in the opening angle range from 20 to 26 degrees. Nevertheless, the steady results showed more consistency than unsteady results for the three different test cases at different operating conditions.
3D Casing-Distributor Analysis for Hydraulic Design Application
François Guibault,Christophe Devals,Ying Zhang,Julien Dompierre,Thi C Vu,Luca Mangani 한국유체기계학회 2015 International journal of fluid machinery and syste Vol.8 No.3
Nowadays, computational fluid dynamics is commonly used by design engineers to evaluate and compare losses in hydraulic components as it is less expensive and less time consuming than model tests. For that purpose, an automatic tool for casing and distributor analysis will be presented in this paper. An in-house mesh generator and a Reynolds Averaged Navier-Stokes equation solver using the standard k-ω shear stress transport (SST) turbulence model will be used to perform all computations. Two solvers based on the C++ OpenFOAM library will be used and compared to a commercial solver. The performance of the new fully coupled block solver developed by the University of Lucerne and Andritz will be compared to the standard 1.6ext segregated simpleFoam solver and to a commercial solver. In this study, relative comparisons of different geometries of casing and distributor will be performed. The present study is thus aimed at validating the block solver and the tool chain and providing design engineers with a faster and more reliable analysis tool that can be integrated into their design process.
François Guibault,Christophe Devals,Thi C. Vu 한국유체기계학회 2015 International journal of fluid machinery and syste Vol.8 No.3
This paper presents a CFD-based methodology for the prediction of guide vane torque in hydraulic turbine distributor for aligned and misaligned configurations. A misaligned or desynchronized configuration occurs when the opening angle of one guide vane differs from the opening angle of all other guide vanes, which may lead to a torque increase on neighbouring guide vanes. A fully automated numerical procedure is presented, that automates computations for a complete range of operation of a 2D or 3D distributor. Results are validated against laboratory measurements.
Hossein Hosseinimanesh,Christophe Devals,Bernd Nennemann,François Guibault 한국유체기계학회 2015 International journal of fluid machinery and syste Vol.8 No.3
No-load speed is an important performance factor for the safe operation of hydropower systems. In turbine design, the manufacturers must conduct several model tests to calculate the accurate value of no-load speed for the complete range of operating conditions, which are expensive and time-consuming. The present study presents steady and unsteady methods for calculating no-load speed of a Francis turbine. The steady simulations are implemented using a commercial flow solver and an iterative algorithm that relies on a smooth relation between turbine torque and speed factor. The unsteady method uses unsteady RANS simulations that have been integrated with a user subroutine to retrieve the runner speed, time step and friction torque. The main goal of this research is to evaluate and compare the two methods by calculating turbine dynamic parameters for three test cases consisting of high and medium head Francis turbines. Overall, the numerical results agreed well with experimental data. The unsteady method provided more accurate results in the opening angle range from 20 to 26 degrees. Nevertheless, the steady results showed more consistency than unsteady results for the three different test cases at different operating conditions.
Steady and unsteady flow computation in an elbow draft tube with experimental validation
Vu, Thi C.,Devals, Christophe,Zhang, Ying,Nennemann, Bernd,Guibault, Francois Korean Society for Fluid machinery 2011 International journal of fluid machinery and syste Vol.4 No.1
Steady state computations are routinely used by design engineers to evaluate and compare losses in hydraulic components. In the case of the draft tube diffuser, however, experiments have shown that while a significant number of operating conditions can adequately be evaluated using steady state computations, a few operating conditions require unsteady simulations to accurately evaluate losses. This paper presents a study that assesses the predictive capacity of a combination of steady and unsteady RANS numerical computations to predict draft tube losses over the complete range of operation of a Francis turbine. For the prediction of the draft tube performance using k-${\varepsilon}$ turbulence model, a methodology has been proposed to average global performance indicators of steady flow computations such as the pressure recovery factor over an adequate number of periods to obtain correct results. The methodology will be validated using two distinct flow solvers, CFX and OpenFOAM, and through a systematic comparison with experimental results obtained on the FLINDT model draft tube.
Ganesh Prasad Awasthi,Deval Prasad Bhattarai,Bikendra Maharjan,김경석,박찬희,김철상 한국공업화학회 2019 Journal of Industrial and Engineering Chemistry Vol.72 No.-
Herein, we proposed, for thefirst time, a novel activated carbon (AC) material synthesized from Wisteriasinensis (WS) seeds biomass. Characterizations of the material were carried out by Field-emissionscanning electron microscopy, Transmission electron microscopy, X-ray diffraction, Raman spectroscopy,Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and Brunauer-Emmett-Teller specific surface area analysis. As-synthesized AC was employed as an electrode material to evaluateits applicability in energy storage devices. Results showed enhanced capacitive performance in an acidicelectrolyte compared to the neutral electrolyte at similar current density. Thus, as-synthesized AC couldbe a suitable material for energy storage applications.