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101.
Bongsoo Kim Seungbum Hong Hyunwoo Choi Won‐Hee Ryu Haemin Paik Yoon‐Young Choi Hyuk‐Sang Kwon Kwangsoo No 《Journal of the American Ceramic Society》2013,96(5):1355-1358
Nanoscale ferroelectric honeycombs, comprised of vertically aligned PbTiO3 nanotubes, are fabricated by vapor phase reaction between lead acetate‐infiltrated TiO2 nanotubes and PbO vapor. PbTiO3 nanohoneycombs converted by vapor phase reaction at 550°C showed well‐aligned nanoscale structure with alignment angle less than 1° and well‐defined ferroelectric properties with the effective piezoelectric coefficient of 44 pm/V. This novel nanoscale structure is expected to facilitate high efficiency sensing of electromechanical and electrochemical stimuli. 相似文献
102.
Hanlim Lee Hitoshi Irie Jaeyong Ryu Yugo Kanaya Youngmin Noh Young J. Kim 《Aerosol science and technology》2013,47(12):1208-1217
A recently developed aerosol retrieval algorithm based on O4 slant column densities (SCDs) measured at a visible wavelength (476 nm) was utilized to derive aerosol information (e.g., aerosol optical depth (AOD) and vertical distributions of aerosol extinction coefficients (AECs)) in the lower troposphere during a severe Asian dust period. The MAX-DOAS measurements were carried out at Gwangju, Korea for nearly three months from February through May 2008. Comparison with AOD and surface PM10, measured by collocated sunphotometer and beta gauge sampler, were made to validate the retrieved AODs and AECs in the atmospheric layer surface to 1 km height above ground. On the Asian dust days, temporal variations of the AODs retrieved from MAX-DOAS measurements show similar patterns, but with reduced magnitudes, to those measured by sunphotometer whereas similar AOD magnitude and temporal variation was observed between MAX-DOAS and sunphotometer measurements during the non-episodic days. Smaller correlation was observed between the surface PM10 and AECs at 0.5 km during the Asian dust period compared to the correlation obtained for the non episodic days. This study demonstrates the ability of MAX-DOAS as a remote sensing technique for surface aerosol measurements under conditions of homogeneously distributed pollution in the planetary boundary layer. However, for the measurement of significantly enhanced aerosol loads with heterogeneous vertical distribution (e.g., Asian dust), measured AODs and AECs are underestimated at altitudes above 1 km due to decreased sensitivity of MAX-DOAS measurements at high altitudes. 相似文献
103.
Keisuke Kobayashi Minoru Ryu Yutaka Doshida Youichi Mizuno Clive A. Randall 《Journal of the American Ceramic Society》2013,96(2):531-537
The (1?x)NaNbO3–(x)NaTaO3 solid solution was investigated for x ≤ 0.4 in terms of new high‐temperature and high‐permittivity dielectric system that is suitable for base metal inner electrode capacitor applications. The addition of Ta significantly enhanced the resistivity of the dielectric, resulting in superior resistivity than the dielectrics‐formulated BaTiO3 systems that dominate the multilayer ceramic capacitor dielectric devices. The voltage dependence of the permittivity was also superior to BaTiO3‐based materials, providing higher capacitance at higher temperatures. A transmission electron microscopy study illustrated that the grains had so‐called core‐shell structure. According to the electron diffraction analysis, the core region had an inhomogeneous structure between antiferroelectric and ferroelectric phases, and shell region had an incommensurate ferroelectric‐like structure. The core and shell region had Nb‐ and Ta‐rich composition, respectively, and their interface was compositionally sharp, implying that shell region was formed via a liquid phase during the sintering process with an incongruent Ta dissolution reprecipitation. We anticipate that these or similar materials based on the alkali‐niobate perovskites can be further enhanced to provide capacitor solutions from 150°C to 250°C, which is an important range for a number of new AC–DC invertor and engine control units. 相似文献
104.
Min-Ah Song Sung-In Ha Dea-Young Park Cheol-Hwi Ryu An-Soo Kang Sang-Bong Moon Jang-Hoon Chung 《International Journal of Hydrogen Energy》2013
Covalently cross-linked SPEEK/Cs-TPA/CeO2 composite membrane was prepared for the polymer electrolyte membrane water electrolysis. Tungstophosphoric acid (TPA) with a cesium was added to the SPEEK to increase proton conductivity. CeO2 was used to scavenge free radicals which attack the membrane in the water electrolysis and to improve the durability of the membrane. The composite membrane featured the electrochemical characteristics, such as 0.130 S/cm of proton conductivity at 80 °C, and 2.324 meq./g-dry-memb. of ion-exchange capacity. Pt(NH3)4Cl2, Pd(NH3)4Cl2, RhCl3 and Co(NH6)4Cl3 were used to prepare a variety of the membrane electrode assemblies (MEAs) as electrocatalytic precursors. Electrochemical activity surface area (ESA) of the Pt–Pd electrode prepared with 2 mM Pt(NH3)4Cl2 and 2 mM Pd(NH3)4Cl2 showed the best properties of 26.2 m2/g with CL-SPEEK/Cs-TPA/CeO2 membrane. In water electrolysis performance, the cell voltage of Pd/PEM/Pt–Pd MEA with CL-SPEEK/Cs-TPA/CeO2(1%) composite membrane showed cell property of 1.82 V at 1 A cm−2 and 80 °C. 相似文献
105.
Young Cheol Ryu Tae Gun Kim Guem-Seok Seo Jin Hwan Park Cha Soo Suh Seong-Soo Park Seong-Soo Hong Gun Dae Lee 《Journal of Industrial and Engineering Chemistry》2008,14(2):213-218
The TiO2/substrate pearlescent pigments were prepared by the hydrolysis of TiOCl2 on the substrate followed by a calcinations process. The natural mica (muscovite), synthetic mica (fluorophlogopite) and -alumina flake were selected as the substrates for pearlescent pigments. The effect of substrate on the anatase to rutile (A–R) phase transformation of TiO2 was studied. The A–R phase transformation of TiO2 during the preparation of pearlescent pigments and their proportion in the TiO2 layer have been analyzed by XRD measurements. The phase compositions of TiO2 layer in each pearlescent pigment are quite different depending on the substrates. The TiO2 layer deposited on -alumina has higher rutile fraction than those on the natural and synthetic mica. The XPS analysis showed that the cations originally present in the substrates diffused into the TiO2 layer. The TiO2 layer deposited on -alumina contains Al, while those on the natural and synthetic mica substrates contain Si and K in addition to Al. The metal cations diffusing from the substrate into TiO2 layer might retard the A–R phase transformation of TiO2. The suppressing effect on the A–R transformation of TiO2 by mixed cations seems to be much stronger than that of single cation, resulting in relatively higher rutile fraction in the case of TiO2 layer deposited on -alumina. 相似文献
106.
In this study, polymer‐clay nanocomposites of various concentrations were prepared by ultrasonically assisted polymerization and melt‐mixing processes. A sonication process using power ultrasonic waves was employed to enhance nano‐scale dispersion during melt‐mixing of polymer blends and organically modified clay. We expected enhanced breakup of layered silicate bundles and further reduction in the size of the dispersed phase, with better homogeneity compared to the different immiscible blend pairs. X‐ray diffraction (XRD) and Transmission Electron Microscopy (TEM) were used to characterize the structures of the nanocomposites. The rheological behaviors of the obtained nanocomposites were measured with parallel plate rheometry. It was found that the ultrasound‐assisted process successfully generated exfoliated nanocomposites and promoted in‐situ compatibilization of the matrix comprising an immiscible pair of polymers in a blend. The resulting nanocomposite exhibited superior thermal stability and elastic modulus compared to the base polymer. Polym. Eng. Sci. 44:1198–1204, 2004. © 2004 Society of Plastics Engineers. 相似文献
107.
Sunwoo Park Hueseok Choi Kihong Ryu Sayup Kim Youngho Kim 《Journal of Mechanical Science and Technology》2009,23(1):204-211
In this study, biomechanical characteristics during the whole process of gait initiation for twenty normal healthy volunteers
were determined by the motion analysis with six near-infrared cameras, four forceplates, and an EMG system. Gait initiation,
a transitional movement phenomenon from quiet stance to steady-state walking, involves a series of muscular activities, GRFs,
movements of COP and COM, and joint motions. Results showed that the location of the net COP to be most lateral during double
limb stance at the beginning of gait initiation. During gait initiation, changes in anteroposterior components of GRFs were
first found and then changes in vertical components followed. Hip and knee motions were found before the ankle joint motion.
Walking speed, step length, and stride length gradually increased until the second step. The interaction between the COM and
COP is tightly regulated to control the trajectory of the COM and thereby control total body balance.
This paper was recommended for publication in revised form by Associate Editor Hong Hee Yoo
Sun-Woo Park received a B.S. degree in Biomedical Engineering from Yonsei University in 2006. He is currently a M.S. candidate in the
Department of Biomedical Engineering, Yonsei University, Korea. His research interests in the area of Human Movement and detection
of gait phase using motion sensors.
Hue-Seok Choi received a B.S. degree in Computer Engineering from Daejeon University in 2004. He is currently a P.D. candidate at the Department
of Biomedical Engineering at Yonsei University, Korea. His research interests are in the area of Human Movement and Rehabilitation
Engineering.
Ki-Hong Ryu received a B.S. and M.S. degrees in Biomedical Engineering from Yonsei University in 1998 and 2001, respectively. He is currently
a P.D. candidate in the Department of Biomedical Engineering, Yonsei University, Korea. His research interests are in the
area of Human Movement and Gait Training System using Functional Electrical Stimulation.
Sa-Yup Kim received a B.S. degree in Electrical Engineering from Yeungnam University in 2002 and M.S. degrees in Biomedical Engineering
from Yonsei University in 2006. He is currently working from Korea Institute of Industrial Technology in Cheonan, Korea.
Young-Ho Kim received a B.S. degree in Mechanical Engineering from Hanyang University in 1982. He then went on to receive his M.S. and
Ph.D. degrees from University of Iowa in 1989 and 1991, respectively. He is currently a Professor in the Department of Biomedical
Engineering, Yonsei University, Korea. His research interests are in the area of Human Movement, Rehabilitation Engineering,
and Biomechanics. 相似文献
108.
Yin Zhong Shen Sung Ho Kim Hai Dong Cho Chang Hee Han Woo Seog Ryu 《Nuclear Engineering and Design》2009,239(4):648-68
One of the reasons that ferritic/martenstic steels have been considered as candidate materials for nuclear power reactors is their superior creep resistance at elevated temperature. The creep rupture strength of 9% chromium steel could be improved by a fine dispersion of secondary precipitate phase. The precipitate phases in extra-low carbon 9% chromium steel with tempered conditions were investigated by transmission electron microscope and energy-dispersive X-ray analysis. The steel specimens were normalized and then tempered at different temperatures. Niobium-rich MN nitrides (Nb0.6V0.3Cr0.1)N, and two kinds of vanadium nitrides, (V0.6Nb0.2Cr0.2)N and (V0.45Nb0.45Cr0.1)N having a f.c.c. crystal structure, were identified in the steel specimens tempered at 600-780 °C, and 750 or 780 °C respectively. Hexagonal chromium-rich M2N precipitate phases with different lattice parameters, a = 2.80 Å/c = 4.45 Å and a = 7.76 Å/c = 4.438 Å, were determined in the tempered steel specimens. The M2N phase showed a decrease/an increase in its chromium/vanadium content as the tempering temperature was increased. The influence of precipitates and heat treatment conditions on the high temperature properties of 9% Cr steel was discussed. 相似文献
109.
Yin Zhong Shen Sung Ho Kim Chang Hee Han Hai Dong Cho Woo Seog Ryu 《Journal of Nuclear Materials》2009,384(1):48-55
The investigations on the precipitate phases in a 9%Cr ferritic/martensitic steel under different normalization conditions have been made by using a transmission electron microscope and an energy-dispersive X-ray spectroscopy. Hot-rolled steel samples were normalized at 1050-1200 °C for 1-2 h followed by an air cooling to room temperature. MN vanadium nitride precipitates with a plate-like morphology and a chemical formula of about (V0.4Nb0.4Cr0.2)N have been observed at triple junctions, grain boundaries and within matrix in the steel samples normalized at 1050-1150 °C for 1-2 h, but they were dissolved out at 1200 °C within 1 h. Vanadium nitride is a stable phase at 1050 °C according to thermocalc prediction of equilibrium phases in the steel. With increasing normalizing temperature and time, there was no a striking change in the chemical composition of metallic elements in the MN phase, but a considerable increase in the size of the MN precipitate. 相似文献
110.
Jina Ryu Mats Brittberg Bomi Nam Jinyeong Chae Minju Kim Yhan Colon Iban Martin Magneli Eiji Takahashi Bharti Khurana Charles R. Bragdon 《International journal of molecular sciences》2022,23(5)
Cartilage lesions are difficult to repair due to low vascular distribution and may progress into osteoarthritis. Despite numerous attempts in the past, there is no proven method to regenerate hyaline cartilage. The purpose of this study was to investigate the ability to use a 3D printed biomatrix to repair a critical size femoral chondral defect using a canine weight-bearing model. The biomatrix was comprised of human costal-derived cartilage powder, micronized adipose tissue, and fibrin glue. Bilateral femoral condyle defects were treated on 12 mature beagles staged 12 weeks apart. Four groups, one control and three experimental, were used. Animals were euthanized at 32 weeks to collect samples. Significant differences between control and experimental groups were found in both regeneration pattern and tissue composition. In results, we observed that the experimental group with the treatment with cartilage powder and adipose tissue alleviated the inflammatory response. Moreover, it was found that the MOCART score was higher, and cartilage repair was more organized than in the other groups, suggesting that a combination of cartilage powder and adipose tissue has the potential to repair cartilage with a similarity to normal cartilage. Microscopically, there was a well-defined cartilage-like structure in which the mid junction below the surface layer was surrounded by a matrix composed of collagen type I, II, and proteoglycans. MRI examination revealed significant reduction of the inflammation level and progression of a cartilage-like growth in the experimental group. This canine study suggests a promising new surgical treatment for cartilage lesions. 相似文献