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931.
Seung Yun Yang Eung-Sam Kim Gumhye Jeon Kwan Yong Choi Jin Kon Kim 《Materials science & engineering. C, Materials for biological applications》2013,33(3):1689-1695
We independently controlled surface topography and wettability of polystyrene (PS) films by CF4 and oxygen plasma treatments, respectively, to evaluate the adhesion and proliferation of human fetal osteoblastic (hFOB) cells on the films. Among the CF4 plasma-treated PS films with the average surface roughness ranging from 0.9 to 70 nm, the highest adhesion of hFOB cells was observed on a PS film with roughness of ~ 11 nm. When this film was additionally treated by oxygen plasma to provide a hydrophilic surface with a contact angle less than 10°, the proliferation of bone-forming cell was further enhanced. Thus, the plasma-based independent modification of PS film into an optimum nanotexture for human osteoblast cells could be appplied to materials used in bone tissue engineering. 相似文献
932.
Dong‐Seon Won Jin‐Hyang Kim Hyo Jin No You Jin Cho Ju‐Yeon Lee Bum Ku Rhee Hee‐Dok Choi 《Polymer International》2010,59(2):162-168
Stabilization of electrically induced dipole alignment is one of the important criteria in the development of nonlinear optical (NLO) polymers for electro‐optic device applications. Polyurethanes for NLO applications have attracted attention because of their high thermal stability due to hydrogen bonding. In the work reported here, we designed and synthesized a new type of NLO polyurethane, in which the pendant NLO chromophores are part of the polymer backbone. This mid‐type NLO polymer is expected to have the merits of both main‐chain and side‐chain NLO polymers, namely stable dipole alignment and good solubility. 1‐[3,4‐Di‐(2‐hydroxyethoxy)phenyl]‐2‐(2‐thienyl)ethene was prepared and condensed with 3,3′‐dimethoxy‐4,4′‐biphenylenediisocyanate to yield a polyurethane. This polyurethane was reacted with tetracyanoethylene to give a novel Y‐type polyurethane (7) containing 1‐(3,4‐dioxyphenyl)‐2‐[5‐(1,2,2‐tricyanovinyl)‐2‐thienyl]ethenes as NLO chromophores, which constitute part of the polymer backbone. Polyurethane 7 is soluble in common organic solvents such as N,N‐dimethylformamide and dimethylsulfoxide. It shows a thermal stability up to 280 °C from thermogravimetric analysis with a glass transition temperature obtained from differential scanning calorimetry of ca 162 °C. The second harmonic generation (SHG) coefficient (d33) of a poled polymer film of he polyurethane at 1560 nm fundamental wavelength is ca 1.11 × 10?18 C. Polymer 7 exhibits an enhanced thermal stability and no significant SHG decay is observed below 150 °C, which is acceptable for NLO device applications. Copyright © 2009 Society of Chemical Industry 相似文献
933.
934.
Culture plays an important role in how an information technology is developed and used. However, few studies attempt to identify the cultural traits most relevant to the specific technology being examined. The main purpose of this study is to develop measures for cultural characteristics of individual users with a specific information technology, the mobile Internet. We propose measures for four cultural characteristics important in the context of the mobile Internet, which are expected to be widely used in the future. The proposed measures were verified empirically through online surveys conducted in seven countries. The results indicate that the measures have high validity and reliability, as well as comparability among the seven countries. The paper ends with a discussion of the study’s limitations and implications. 相似文献
935.
Vo-Gia Loc Se-goh Roh Ig Mo Koo Duc Trong Tran Ho Moon Kim Hyungpil Moon Hyouk Ryeol Choi 《Robotics and Autonomous Systems》2010,58(5):666-675
In this paper, a general study on improving adaptability of quadruped walking and climbing robot in complex environment is presented. First, a sensing system composed of range and gyroscope sensors in a novel arrangement is developed. By combining the sensing signals and the internal state of the robot, the surface geometry of the environment is sufficiently reconstructed in real-time. Secondly, a planning algorithm for the robot to overcome the reconstructed environment is conducted. Based on the reshaped surface, the planning algorithm not only provides the exact body trajectory and foot positions but also the adaptability of the robot in a specific environment. A method to improve the adaptability of the walking and climbing robot is also introduced. Thanks to the adherent ability of the robot, the center of gravity of the robot is allowed to move outside the support polygon to increase the reach-ability of the next swing leg. Finally, the effectiveness of the proposed approach is verified by the performances of the experiments in complex environments using a quadruped walking and climbing robot named MRWALLSPECT IV. 相似文献
936.
937.
Jong-Jin Choi Joo-Hee Lee Dong-Soo Park Byung-Dong Hahn Woon-Ha Yoon Hua-Tay Lin 《Journal of the American Ceramic Society》2007,90(6):1926-1929
Conductive La0.8 Sr0.2 MnO3 (LSM) and La0.6 Sr0.4 Co0.2 Fe0.8 O3 (LSCF) layers with a thickness of ∼10 μm were deposited on ferritic stainless steel (SS) by the aerosol deposition method, for use as an oxidation resistance-coating layer in the metallic interconnector of a solid oxide fuel cell. The coated layers were fairly dense without pores or cracks, and maintained good adhesion even after oxidation at 800°C for 100 h. The surface of the bare SS after annealing at 800°C for 100 h was covered with Cr2 O3 and Fe3 O4 oxide scales, and the electrical conductivity was sharply decreased. However, the LSM- and LSCF-coated SSs showed a surface microstructure with almost no oxidation and maintained good electrical conductivity after annealing at 800°C for 100 h. The area-specific resistance (ASR) of LSM- and LSCF-coated alloys after 100 h of oxidation at 800°C was 20.6 and 11.7 mΩ·cm2 , respectively. 相似文献
938.
The purpose of this study is to propose simplified strength equations that can be conveniently used to establish a P–M interaction curve of square concrete filled tubes (CFTs) with concrete strength of up to 100 MPa. The method presented in the author's previous study [Choi Y-H, Foutch DA, LaFave JM. New approach to AISC P–M interaction curve for concrete filled tube beam-columns. Eng Struct 2006;28(11):1586–98] was used as a basic unified formula for pure steel members and CFT ones, and a parametric study was performed to determine the contribution of the concrete, which were expressed by two variables: a normalized maximum moment, α, and the axial load ratio at the maximum moment, β. The two variables were formulated with respect to tube width-to-thickness ratio (b/t) and relative concrete compressive strength to yield strength of the steel tube (f′c/Fy). Then, the proposed method were compared to experimental data found in literatures, which showed greatly improved results in terms of accuracy and amount of computation, when compared to the current AISC design methods. 相似文献
939.
Geun-Pyo Hong Sang-Gi Min Se-Hee Ko & Mi-Jung Choi 《International Journal of Food Science & Technology》2008,43(8):1484-1491
This study investigated the effects of high pressure processing and κ-carrageenan on cold-set binding in restructured pork meat. High pressure (>200 MPa) combined with carrageenan level higher than 1.5% caused increased breaking force and tensile strength ( P < 0.05). Increasing the pressure level caused a continuous κ-carrageenan network in the junctions between meat particles, as confirmed by scanning electron microscopy imaging. With regard to the water binding properties, all treatments showed moisture content ranging between 74% and 76%. Increases in pressure levels and holding times tended to improve the water-holding capacity (WHC) of restructured pork; however, the κ-carrageenan concentration showed no relation with WHC. Cooking loss decreased significantly ( P < 0.05) with increases in both pressure level and κ-carrageenan concentration. By increasing pressure levels, both the L * - and a * -values increased, but the b * -value showed no significant difference ( P > 0.05) among the treatments, with the exception of 100 MPa for 30 min. The addition of κ-carrageenan had no effect on colour ( P > 0.05). Therefore, the results indicate that pressure above 200 MPa and addition of 1.5% carrageenan has potential use in cold-set meat restructuring. 相似文献
940.
Je-Eun Choi Masahiro Takei Hyo-Jae Jo Javier Ortiz-Villafuerte 《Nuclear Engineering and Design》2008,238(8):2055-2063
Currently, wavelet transforms are widely used for the analyses of particle image velocimetry (PIV) velocity vector fields. This is because the wavelet provides not only spatial information of the velocity vectors, but also of the time and frequency domains. In this study, a discrete wavelet transform is applied to real PIV images of bubbly flows. The vector fields obtained by a self-made cross-correlation PIV algorithm were used for the discrete wavelet transform. The performances of the discrete wavelet transforms were investigated by changing the level of power of discretization. The images decomposed by wavelet multi-resolution showed conspicuous characteristics of the bubbly flows for the different levels. A high spatial bubble concentrated area could be evaluated by the constructed discrete wavelet transform algorithm, in which high-leveled wavelets play dominant roles in revealing the flow characteristics. 相似文献