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91.
Well-aligned anodic tungsten oxide (WO3) nanotubes with lengths approaching 600 nm was successfully synthesised via electrochemical anodisation of tungsten (W) film at 40 V in a bath with electrolyte (pH 3) consisted of 1 M of sodium sulphate (Na2SO4) and 0.7 wt-% ammonium fluoride (NH4F) for 15 min. It was found that the production of dense compact oxide layer on pure W film could be explained with high concentration of H+ ions accelerated the hydrolysis ability on the W surface to form thick WO3 layer under acidic condition (pH: 3). The photocatalytic activity performance was increased by ≈15% for the dense WO3 nanostructures film as compared to the thin and irregular WO3 nanostructures film because of the high active surface area to absorb more photons from solar irradiation for triggering the charge carriers separation and then improvement of internal and external diffusion of the reactants. 相似文献
92.
Kap Seung Yang Dong Joon Lee Seung Kon Ryu Yozo Korai Yong Joong Kim Isao Mochida 《Korean Journal of Chemical Engineering》1999,16(4):518-524
A precursor for a general purpose carbon fiber was prepared from coal tar pitch (CP) modified with 10 % p-benzoquinone (BQ) at 380 ?C for 3 hours. Such a modification raised the softening of the pitch from 85 ?C to 271 ?C at a yield of 43 %. The modified pitch was spun smoothly at a rate of 480 m/min into a fiber of 20 Μm diameter. The fiber was stepwise stabilized at 236 ?C (5 ?C/min) and 312 ?C (1 ?C/min) for 3 hours at each temperature. Successively,carbonization and graphitization were performed at 1,000 ?C and 2,400 ?C, respectively, for one hour. Both the carbonized and graphitized fibers exhibited tensile strength of 570 MPa. The structural parameters of carbon and graphite fibers were their orientation values of 56.2 and 58.1 %, relatively low Lc(002) of 11.24 and 25 å, and large interlayer spacing (d002) of 3.86 and 3.49 å, respectively. 相似文献
93.
The surface of a commercial Li[Ni0.4Co0.3Mn0.3]O2 cathode is modified using Li3PO4-based coating materials. The electrochemical properties of the coated materials are investigated as a function of the pH value of the coating solution and the composition of coating materials. The Li3PO4 coating solution with pH 2 is found to be favorable for the formation of stable coating layers having enhanced electrochemical properties. The Li3PO4, Li1.5PO4, and PO4 coating layers are formed as amorphous phases. However, the Li3−xNix/2PO4 coating layers are composed of small particles with a crystalline phase covered with an amorphous phase. Li3PO4 and Li1.5PO4 coatings considerably enhance the rate capability of the Li[Ni0.4Co0.3Mn0.3]O2 electrode. In contrast, the Li3−xNix/2PO4 coating material, which contained Ni, has an inferior rate capability compared to the LixPO4 series (x = 1.5 and 3), although the LiNiPO4-coated electrode shows a better rate capability than a pristine one. Li3PO4-based coating materials are effective at enhancing the cyclic performance of the electrode in the voltage range of 3.0-4.8 V. DSC analysis also confirms the improved thermal stability attained by coating the cathode with Li3PO4-based materials. 相似文献
94.
Joon Sang Lee 《International Journal of Heat and Mass Transfer》2004,47(3):437-446
The goal of the present study was to perform a large eddy simulation of vertical turbulent annular pipe flow under conditions in which fluid properties vary significantly, and to investigate the effects of buoyancy on the turbulent structures and transport. Isoflux wall boundary conditions with low and high heating are imposed. The compressible filtered Navier-Stokes equations are solved using a second order accurate finite volume method. Low Mach number preconditioning is used to enable the compressible code to work efficiently at low Mach numbers. A dynamic subgrid-scale stress model accounts for the subgrid-scale turbulence. Comparisons were made with available experimental data. The results showed that the strong heating and buoyant force caused distortions of the flow structure resulting in reduction of turbulent intensities, shear stress, and turbulent heat flux, particularly near the wall. 相似文献
95.
In this study, a numerical investigation has been performed on the spreading and solidification of a coating material droplet onto the rigid substrate in the thermal spray process. The computational model is validated through the comparison of the predicted numerical result and the experimental data for flat substrate. An analysis of the deposition formation on a substrate with small concentric grooves or ridges was performed. To examine the characteristic of the impact and solidification of a liquid droplet on the substrate with concentric grooves or ridges, a parametric study was conducted with various shapes and sizes of concentric grooves or ridges. 相似文献
96.
Different amino acid derivatives were synthesized during cultivation of a Monascus species. Derivatives exhibiting an inhibitory activity against HMG-CoA reductase were screened by in vitro tests. The threonine derivative had a high inhibitory activity of 38% while four other derivatives showed a greater than 23% activity. The orange monascus pigment showed a high activity of 36%. In vivo tests using female C57BL/6 mice were performed with the threonine derivative and orange pigment. Changes in the cholesterol and lipid levels in mice due to addition of the pigments were investigated. The total cholesterol (TC) level of mouse serum was reduced by 8–9% with the threonine derivative and by 16% with orange pigment. Supplementation with the threonine derivative and orange pigment decreased the LDL cholesterol level by 18–26% and increased the HDL cholesterol level by 1–9%. The atherogenic index (AI) value was reduced by 23–27% with pigment supplementation. The anti-atherosclerosis effect of monascus pigments can be induced by control of the lipid content in the serum rather than in the liver of mice. 相似文献
97.
Ho Keun Song Soo Gil Kim Hyeong Joon Kim Suk Ki Kim Ki Wan Kang Jung Chul Leeand Kyung Hoon Yoon 《Solar Energy Materials & Solar Cells》2003,75(1-2):145-153
CuIn1−xGaxSe2 polycrystalline thin films were prepared by a two-step method. The metal precursors were deposited either sequentially or simultaneously using Cu–Ga (23 at%) alloy and In targets by DC magnetron sputtering. The Cu–In–Ga alloy precursor was deposited on glass or on Mo/glass substrates at either room temperature or 150°C. These metallic precursors were then selenized with Se pellets in a vacuum furnace. The CuIn1−xGaxSe2 films had a smooth surface morphology and a single chalcopyrite phase. 相似文献
98.
Man Gu Kang Nam-Gyu Park Yong Joon Park Kwang Sun Ryu Soon Ho Chang 《Solar Energy Materials & Solar Cells》2003,75(3-4):475-479
The transparent electric windows based on dye-sensitized nanocrystalline TiO2 solar cells have been prepared. The solar cell consists of dye-sensitized TiO2 electrode with a TiO2 layer of an about 8 μm thickness and of a 80×80 mm2 active area, Pt counter electrode and redox electrolyte. The solar cell shows a transmittance of approximately 60% in the visible range and an open-circuit voltage (Voc) of 0.64 V and a short-circuit photocurrent (Jsc) of 250 mA. A moderately transparent electric window composed of nine unit solar cells in series generates Voc of 5.7 V and Jsc of 220 mA at one sun light intensity. 相似文献
99.
Sun Kyoung Kim Woo Il Lee Joon Sik Lee 《Journal of Mechanical Science and Technology》2002,16(5):710-719
This study investigates a nonlinear inverse convection problem for a laminar-forced convective flow between two parallel plates. The upper plate is exposed to unknown heat flux while the lower plate is insulated. The unknown heat flux is determined using temperature measured on the lower plate. The thermophysical properties of the fluid are temperature dependent, which renders the problem nonlinear. The sequential gradient method is applied to this nonlinear inverse problem in order to solve the problem efficiently. The function specification method is incorporated to stabilize the sequential estimation. The corresponding adjoint formalism is provided. Accuracy and stability have been examined for the proposed method with test cases. The tendency of deterministic error is investigated for several parameters. Stable solutions are achieved even with severely impaired measurement data. 相似文献
100.
Seong-Ku Kim Joon Kyu Lee Yong-Mo Kim Jae-Hyun Ahn 《Journal of Mechanical Science and Technology》2002,16(7):1009-1018
The Representative Interactive Flamelet (RIF) concept has been applied to numerically simulate the combustion processes and
pollutant formation in the direct injection diesel engine. Due to the ability for interactively describing the transient behaviors
of local flame structures with CFD solver, the RIF concept has the capabilities to predict the auto-ignition and subsequent
flame propagation in the diesel engine combustion chamber as well as to effectively account for the detailed mechanisms of
soot formation, NOX formation including thermal NO path, prompt and nitrous NOX formation, and reburning process. Special emphasis is given to the turbulent combustion model which properly accounts for
vaporization effects on the mixture fraction fluctuations and the pdf model. The results of numerical modeling using the RIF
concept are compared with experimental data and with numerical results of the commonly applied procedure which the low-temperature
and high-temperature oxidation processes are represented by the Shell ignition model and the eddy dissipation model, respectively.
Numerical results indicate that the RIF approach including the vaporization effect on turbulent spray combustion process successfully
predicts the ignition delay time and location as well as the pollutant formation. 相似文献