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991.
Jung‐Jae Park Do‐Yeon Kim Jong‐Gun Lee Donghwan Kim Joon‐Ho Oh Tae‐Yeon Seong Maikel F.A.M. van Hest Sam S. Yoon 《Journal of the American Ceramic Society》2013,96(5):1596-1601
Photocatalytic and hydrophilic TiO2 thin‐film applications include water purification, cancer therapy, solar energy conversion, self‐cleaning devices, and antifogging windows. We demonstrate superhydrophilicity of aerosol‐deposition (AD) TiO2 films on a glass substrate without use of a carrier solvent, thereby removing the possibility of impurity contamination. AD films exhibit high visible light transmittance (greater than 80%) and superhydrophilicity (0° contact angle) with even minimal UV‐light irradiation exposure. This AD method represents a significant step toward the realization of economically viable, functional thin films for the aforementioned applications. 相似文献
992.
Kong Ping Oh 《摩擦学汇刊》2013,56(2):111-116
A gradient method is described which can be used to solve problems in elastohydrodynamics. The method involves the minimization of an error function, and is compatible with such numerical schemes of solving continuum problems as the finite element or the finite difference method. A finite length slider bearing is used to illustrate the method, and numerical results for the elastohydrodynamic pressure distribution are presented. 相似文献
993.
Cheol-Hong Hwang Chang Bo Oh Chang-Eon Lee 《International Journal of Thermal Sciences》2009,48(7):1423-1431
We carried out numerical simulations to understand how CO2 dilution in either fuel or oxidizer stream changes the flame-vortex interactions in terms of hydrodynamic effects in CH4–air nonpremixed jet flames. The simulation used a time-dependent, axisymmetric computational model and a low Mach number approximation. Reaction rates were calculated from a two-step global reaction mechanism that considered six species. Studies were conducted with fixed initial velocities for three different cases of CO2 introduction: (1) without dilution, (2) dilution in a fuel stream, and (3) dilution in an oxidizer stream. A single vortex was generated by an axisymmetric jet driven of cold fuel, after a flame development was reached to quasi steady-state condition. The simulation shows that CO2 dilution in a fuel stream leads to a slightly increased vortex radius and more entrainment of surrounding fluids compared to the other dilution methods tested. Thus, dilution of CO2 in a fuel stream enhances the mixing inside a single vortex and increases the stretching of the flame surface. The vorticity transport equation budgets were examined to reveal the mechanisms of vortex formation in the presence of CO2. In the stage of vortex formation, vortex production due to baroclinic torque and vortex destruction due to volumetric expansion were found to be greater in the case of CO2 dilution in a fuel stream than in the other dilution cases. However, after vortex formation, there terms showed the opposite tendencies. 相似文献
994.
K.-H. Kim H.-J. Kim K.-Y. Lee J.H. Jang S.-Y. Lee E. Cho I.-H. Oh T.-H. Lim 《International Journal of Hydrogen Energy》2008
The role of Nafion® binder in the electrodes was evaluated by changing its content for the membrane electrode assembly (MEA) fabrication. In the study, we prepared MEAs that have two different compositions of catalyst layers in electrodes. One layer which is close to the electrolyte membrane has the higher Nafion® content. The other which is near the gas diffusion media (GDM) has the lower one. Also, we changed the thickness of two layers to find the ideal composition of the binder and Pt/C in the electrode. The dual catalyst layer coated MEA showed higher cell performance at high current density region than the pristine MEA. 相似文献
995.
J. K. Lee S. H. Kim D. M. Wee K. Sharvan Kumar M. H. Oh 《Metals and Materials International》2008,14(6):713-720
The most pertinent coating materials in the Al−Ti−Cr alloy system to improve the high temperature oxidation resistance of
a TiAl alloy, with respect to oxidation properties, resistance to thermal stress, and chemical compatibility, are the two-phase
alloys of Al−21Ti−23Cr (L12+Cr2Al) and Al−37Ti−12Cr (γ+TiAlCr). In this study, cyclic oxidation tests at 1000 °C and 1200 °C were performed for the specimens
coated with both materials of 10 im thickness. Furthermore, breakaway oxidation caused by the formation of a rutile TiO2 scale was observed, though both bulk alloys showed very stable oxidation behavior. This phenomenon was resulted from the
depleted Al content in the coating layer due to Al2O3 oxide growth and interdiffusion with the substrate. Considering the decrease of Al content due to oxide growth, the Al−21Ti−23Cr
coating with the initial higher Al content was more effective for long-term oxidation protection of the TiAl alloy. On the
other hand, when the Al content changes due to the interdiffusion with the substrate, the Al−37Ti−12Cr coating with a smaller
compositional gradient with the TiAl substrate was more effective than the Al−21Ti−23Cr coating. Cyclic oxidation tests at
1000 °C and 1200 °C confirmed that for the longer lifetime of coating materials the initial Al content was more important
than the smaller compositional gradient with the substrate. Consequently, the Al−21Ti−23Cr coating was considered as more
effective one for the long-term oxidation resistance of TiAl alloys. 相似文献
996.
Tick Hui Oh 《Renewable & Sustainable Energy Reviews》2010,14(9):2697-2709
Secure, reliable and affordable energy supplies are necessary for sustainable economic growth, but increases in associated carbon dioxide (CO2) emissions, and the associated risk of climate change are a cause of major concern. Experts have projected that the CO2 emissions related to the energy sector will increase 130% by 2050 in the absence of new policies or supply constraints as a result of increased fossil fuel usage. To address this issue will require an energy technology revolution involving greater energy efficiency, increased renewable energies and nuclear power, and the near-decarbonisation of fossil fuel-based power generation. Nonetheless, fossil fuel usage is expected to continue to dominate global energy supply. The only technology available to mitigate greenhouse gas (GHG) emissions from large-scale fossil fuel usage is carbon capture and storage (CCS), an essential part of the portfolio of technologies that is needed to achieve deep global emission reductions. However, CCS technology faces numerous issues and challenges before it can be successfully deployed. With Malaysia has recently pledged a 40% carbon reduction by 2020 in the Copenhagen 2009 Climate Summit, CCS technology is seen as a viable option in order to achieve its target. Thus, this paper studies the potential and feasibility of coal-fired power plant with CCS technology in Malaysia which includes the choices of coal plants and types of capture technologies possible for implementation. 相似文献
997.
Sun-Ae Oh Gil-Su Lee Jeong-Hui Park Hae-Won Kim 《Journal of materials science. Materials in medicine》2010,21(11):3019-3027
Calcium phosphate cements (CPCs) have recently gained great interest as injectable bone substitutes for use in dentistry and
orthopedics. α-tricalcium phosphate (α-TCP) is a popularly used precursor powder for CPCs. When mixed with appropriate content
of liquid and kept under aqueous conditions, α-TCP dissolves to form a calcium-deficient hydroxyapatite and then hardens to
cement. In this study, α-TCP based cement (CP) and its composite cement with chitosan (Ch-CP) were prepared and the osteoclastic
responses to the cements and their elution products were evaluated. Preliminary evaluation of the cements revealed that the
CP and Ch-CP hardened within ~10 min at an appropriate powder-to-liquid ratio (PL) of 3.0. In addition, CP and Ch-CP were
transformed into an apatite phase following immersion in a saline solution. Moreover, the osteoblastic cells were viable on
the cements for up to 10 days. Mouse-derived bone marrow cells were isolated and activated with osteoclastic differentiation
medium, and the effects of the CP and Ch-CP substrates and their ionic eluants on the osteoclastic activity were investigated.
Osteoclastic cells were viable for up to 14 days on both types of cements, maintaining a higher cell growth level than the
control culture dish. Multi-nucleated osteoclastic cells that were tartrate-resistant acid phosphatase (TRAP)-positive were
clearly observed when cultured on the cement substrates as well as treated with the cement eluants. The TRAP activity was
found to be significantly higher in cells influenced by the cement substrates and their eluants with respect to the control
culture dish (Ch-CP > CP ≫ control). Overall, the osteoclastic differentiation was highly stimulated by the α-TCP based experimental
cements in terms of both the substrate interaction and their elution products. 相似文献
998.
Oh J. Woolley S.I. Arvanitis T.N. Townend J.N. 《IEEE transactions on medical imaging》2001,20(12):1352-1361
This paper describes a multistage perceptual quality assessment (MPQA) model for compressed images. The motivation for the development of a perceptual quality assessment is to measure (in)visible differences between original and processed images. The MPQA produces visible distortion maps and quantitative error measures informed by considerations of the human visual system (HVS). Original and decompressed images are decomposed into different spatial frequency bands and orientations modeling the human cortex. Contrast errors are calculated for each frequency and orientation, and masked as a function of contrast sensitivity and background uncertainty. Spatially masked contrast error measurements are then made across frequency bands and orientations to produce a single perceptual distortion visibility map (PDVM). A perceptual quality rating (PQR) is calculated from the PDVM and transformed into a one to five scale, PQR(1-5), for direct comparison with the mean opinion score, generally used in subjective ratings. The proposed MPQA model is based on existing perceptual quality assessment models, while it is differentiated by the inclusion of contrast masking as a function of background uncertainty. A pilot study of clinical experiments on wavelet-compressed digital angiogram has been performed on a sample set of angiogram images to identify diagnostically acceptable reconstruction. Our results show that the PQR(1-5) of diagnostically acceptable lossy image reconstructions have better agreement with cardiologists' responses than objective error measurement methods, such as peak signal-to-noise ratio A Perceptual thresholding and CSF-based Uniform quantization (PCU) method is also proposed using the vision models presented in this paper. The vision models are implemented in the thresholding and quantization stages of a compression algorithm and shown to produce improved compression ratio performance with less visible distortion than that of the embedded zerotrees wavelet (EZWs). 相似文献
999.
The ray-optics approach based on the rigorous coupled wave theory, called rigorous ray-optics method (RROM), is developed for the calculation of backward coupling coefficients of grating waveguide devices. The coupling coefficients of several grating structures, such as rectangular, sinusoidal, triangular, and trapezoidal shapes, are evaluated by the RROM, and they are compared with those obtained by two conventional methods of the ray-optics method (ROM) and the coupled-mode method (CMM). In the case of rectangular gratings, the coupling coefficients are evaluated in more detail by varying grating depth and duty-cycle. We have found that the RROM gives us more exact solutions for the backward coupling coefficients of even arbitrary shapes of diffractive grating waveguides than the other two conventional methods 相似文献
1000.
Seongtaek Hwang Kwan-Woong Song Hyung-Jin Kwon Junho Koh Yun-Je Oh Kyuman Cho 《Photonics Technology Letters, IEEE》2001,13(12):1289-1291
We demonstrate a broad-band silica-based erbium-doped fiber amplifier (EDFA) with double-pass configuration. The signal gain and noise figure are obtained more than 24 dB and less than 6 dB, respectively, for 1526-1562 nm and 1569-1605 nm. The same signal gain can be achieved with 53% less pump power and 45% shorter erbium-doped fiber length, compared to a conventional parallel type EDFA. Furthermore, the noise figure and power conversion efficiency are improved for the wavelength range 相似文献