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Verification of Beam Models for Ionic Polymer-Metal Composite Actuator

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Journal of Bionic Engineering 2009年第3期6卷 232-238页

作者： Hoon Cheol Park Quoc Viet Nguyen Jang woo Lee Young tai Yoo Artificial Muscle Research Center Konkuk University Department of Advanced Technology Fusion Konkuk University Department of Materials Chemistry and Engineering Konkuk University

Ionic Polymer-Metal Composite (IPMC) can work as an actuator by applying a few voltages.A thick IPMC actuator,where Nafion-117 membrane was synthesized with polypyrrole/alumina composite filler,was analyzed to verify the equivalent beam and equivalent bimorph beam *** blocking force and tip displacement of the IPMC actuator were measured with a DC power supply and Young's modulus of the IPMC strip was measured by bending and tensile tests *** calculated maximum tip displacement and the Young's modulus by the equivalent beam model were almost identical to the corresponding measured *** element analysis with thermal analogy technique was utilized in the equivalent bimorph beam model to numerically reproduce the force-displacement relationship of the IPMC *** results by the equivalent bimorph beam model agreed well with the force-displacement relationship acquired by the measured *** is confirmed that the equivalent beam and equivalent bimorph beam models are practically and effectively suitable for predicting the tip displacement,blocking force and Young's modulus of IPMC actuators with different thickness and different composite of ionic polymer membrane.

关键词： jonic polymer-metal composite beam model displacement force

Sintering effect on ageing behavior of rare earths (Pr_6O_(11)-Er_2O_3-Y_2O_3 )-doped ZnO varistor ceramics

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Journal of Rare Earths 2012年第10期30卷 1028-1033页

作者： Choon-woo Nahm Semiconductor Ceramics Laboratory Department of Electrical Engineering Dongeui University

The electrical properties and ageing behavior of the rare earths （Pr6O11-Er2O3-Y2O3）-doped ZnO varistor ceramics were systematically investigated at sintering temperature range of 1335-1350°C. With an increase in the sintering temperature, the sintered density increased from 5.41 to 5.64g/cm3 and the average grain size increased from 5.8 to 7.9μm. The varistor properties and ageing behavior were significantly affected by small sintering temperature range of 1335-1350°C. The breakdown field noticeably decreased from 5767 to 3628V/cm with an increase in the sintering temperature. The varistor ceramics exhibited the highest nonlinear coefficient （43.2） at the sintering temperature of 1340°C. The varistor ceramics sintered at 1350°C exhibited a surprisingly excellent stability by exhibiting 0.3% in the variation rate of the breakdown field and 0.3% in the variation rate of the nonlinear coefficient for ageing stress of 0.95 E1mA/150°C/24 h.

关键词： sintering rare earths nonlinear properties ageing varistors

Characteristics of machined surface controlled by cutting tools and conditions in machining of brittle material

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中国有色金属学会会刊：英文版 2009年第B9期19卷 194-201页

作者： Yong-woo KIM Soo-Chang CHOI Jeung-woo PARK Deug-woo LEE Department of Nano Fusion Technology Pusan National University Department of Mechanical Design Engineering Chosun University Department of Nanosystem and Nanoprocess Engineering Pusan National University

One of the ultra-precision machining methods was adapted for brittle material as well as soft material by using multi-arrayed diamond tips and high speed spindle. Conventional machining method is too hard to control surface roughness and surface texture against brittle material because the particles of grinding tools are irregular size and material can be fragile. Therefore, we were able to design tool paths and machine controlled pattern on surface by multi-arrayed diamond tips with uniform size made in MEMS fabrication and high speed spindle, and the maximum speed was about 3×105 r/min. We defined several parameters that can affect the machining surface. Those were multi-array of diamond tips (n×n), speed of air spindle and feeding rate. The surface roughness and surface texture can be controlled by those parameters for micro machining.

关键词：加工表面脆性材料条件控制刀具路径表面粗糙度特征高速主轴加工方法

The Effect of Plasma Surface Treatment on a Porous Green Ceramic Film with Polymeric Binder Materials

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Plasma Science and Technology 2013年第6期15卷 521-527页

作者： Jeong woo YUN School of Applied Chemical Engineering Chonnam National University

To reduce time and energy during thermal binder removal in the ceramic process, plasma surface treatment was applied before the lamination *** adhesion strength in the lamination films was enhanced by oxidative plasma treatment of the porous green ceramic film with polymeric binding *** oxygen plasma characteristics were investigated through experimental parameters and weight loss *** experimental results revealed the need for parameter analysis,including gas material,process time,flow rate,and discharge power,and supported a mechanism consisting of competing ablation and deposition *** weight loss analysis was conducted for cyclic plasma treatment rather than continuous plasma treatment for the purpose of improving the film’s permeability by suppressing deposition of the ablated *** cyclic plasma treatment improved the permeability compared to the continuous plasma treatment.

关键词： plasma surface treatment oxidative plasma green ceramic film ablation deposition

Potential reduction in carbon fixation capacity under climate change in a Pinus koraiensis forest

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Forest Ecosystems 2024年第2期11卷 152-161页

作者： Dong Kook woo Department of Civil Engineering Keimyung UniversityDaegu42601Republic of Korea

There has been an increasing recognition of the crucial role of forests, responsible for sequestering atmospheric CO_(2), as a moral imperative for mitigating the pace of climate change. The complexity of evaluating climate change impacts on forest carbon and water dynamics lies in the diverse acclimations of forests to changing environments. In this study, we assessed two of the most common acclimation traits, namely leaf area index and the maximum rate of carboxylation(V_(cmax)), to explore the potential acclimation pathways of Pinus koraiensis under climate change. We used a mechanistic and process-based ecohydrological model applied to a P. koraiensis forest in Mt. Taehwa, South Korea. We conducted numerical investigations into the impacts of(i) Shared Socioeconomic Pathways 2–4.5(SSP2-4.5) and 5–8.5(SSP5-8.5),(ii) elevated atmospheric CO_(2) and temperature, and(iii) acclimations of leaf area index and V_(cmax)on the carbon and water dynamics of P. koraiensis. We found that there was a reduction in net primary productivity(NPP) under the SSP2-4.5 scenario, but not under SSP5-8.5, compared to the baseline, due to an imbalance between increases in atmospheric CO_(2) and temperature. A decrease in leaf area index and an increase in V_(cmax)of P. koraiensis were expected if acclimations were made to reduce its leaf temperature. Under such acclimation pathways, it would be expected that the well-known CO_(2) fertilizer effects on NPP would be attenuated.

关键词： Climate change NEP Pinus koraiensis Warming Acclimation

Nonlinear behavior of Tb_4O_7-modified ZnO-Pr_6O_(11)-based ceramics with high breakdown field

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Journal of Rare Earths 2013年第3期31卷 276-280页

作者： Choon-woo Nahm Semiconductor Ceramics Laboratory Department of Electrical EngineeringDongeui UniversityBusan 614-714Korea

The effect of Tb407 on electrical behavior of the ZnO-Pr6Oll-based varistor ceramics was investigated. Microstructural analysis indicated that the addition of Tb407 decreased average grain size from 3.6 to 3.2 and increased the sintered density from 5.58 to 5.68 g/cm3. As the amount ofTb407 increased, the breakdown field increased from 9393 to 12437 V/cm and the nonlinear coefficient increased from 50 to 65. The varistor ceramics added with 0.5 mol.% in the amount of Tb407 exhibited an excellent stability by exhibiting 0. 1% in the variation rate of the breakdown field, 0% in the variation rate of the nonlinear coefficient, and 8.8% in the variation rate of the leakage current density for DC-accelerated aging stress of 0.85 E1 mA/115 ℃/24 h.

关键词： doping ZnO breakdown field electrical properties varistor ceramics rare earths

Diamond machining of sinusoidal grid surface using fast tool servo system for fabrication of hydrophobic surface

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中国有色金属学会会刊：英文版 2012年第S3期22卷 787-792页

作者： Hong LU Deug-woo LEE Sang-Min LEE Jeong-woo PARK Department of Nano Fusion Technology Pusan National University Department of Nano Mechatronics Engineering Pusan National University Department of Mechanical Design Engineering Chosun University

Ultra-precision diamond machining with piezoelectric-assisted fast tool servo (FTS) was used to produce various free-form surfaces.A low cost,rapid and large area fabrication of uniform hydrophobic surface at room temperature which transfers the FTS fabricated sinusoidal grid surface to the flat film with UV-moulding process was described.A piezoelectric-assisted FTS with high band width of 2 kHz,travel range up to 16 μm and the compact mechanism structure was designed for the sinusoidal grid surface machining and the dynamic performance testing of FTS was described in *** results indicate that the dimensions of sinusoidal grid change with the variation of the FTS machining *** properties of UV-moulded surface were evaluated,the best contact angle was measured to be 120.5° on the sinusoidal grid surface with profile wavelength of 350 μm and peak-to-valley amplitude of about 16 μm.

关键词： fast tool servo system diamond turning sinusoidal grid surface UV-moulding contact angle

Contrast evaluation methods for natural color images in display systems: within- and cross-content evaluations

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Journal of Zhejiang University-Science C(Computers and Electronics) 2011年第11期12卷 897-909页

作者： Choon-woo KIM School of Information and Communication Engineering Inha University

Contrast evaluation can be used as a criterion to evaluate performance of contrast enhancement algorithms and to compare contrast capability of display systems. This paper deals with contrast evaluation models for natural color images. Two separate models are defined for within- and cross-content evaluations. The former is to differentiate the perceived contrast of the images with the same content. The latter is to discriminate the differences in contrast among the images with different contents. Perception mechanisms are quite different for within- and cross-content evaluations. Local contrast plays an important role in within-content evaluation. In contrast, global contrast dominates the contrast perception for cross-content evaluation. Results of human visual experiments show that the proposed evaluation models outperform previous methods for both within- and cross-content evaluations.

关键词： Contrast evaluation Global contrast Local contrast Within content Cross content Statistical significance

Fragile histidine triad gene alterations are not essential for hepatocellular carcinoma development in South Korea

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World Journal of Gastroenterology 2008年第22期14卷 3526-3533页

作者： Chang woo Nam Jung woo Shin Neung Hwa Park Department of Surgery University of Ulsan College of Medicine Biomedical Research Center Ulsan University Hospital Ulsan 682-714 South Korea Internal Medicine University of Ulsan College of Medicine Biomedical Research Center Ulsan University Hospital Ulsan 682-714 South Korea

AIM: To establish the role of FHIT in the pathogenesis hepatocellular carcinoma (HCC). METHODS: We examined genomic alterations, as well as, mRNA and protein expression patterns from the FHIT gene, in 48 surgically resected hepatocellular carcinoma (HCC) tissues. Additionally, p53 mutations were analyzed. RESULTS: Aberrant FHIT transcripts were detected in 11 of 48 surrounding non-tumor liver tissues and 27 of 48 HCC samples (22.9% vs 56.3%, P = 0.002). No point mutations were identified within the open reading frame region of FHIT. Loss of heterozygosity (LOH) of the FHIT locus was detected in 4 of 42 informative cases for D3S1300, and 3 of 29 informative cases for D3S1313. Reduced expression of FHIT protein (Fhit) was observed in 8 (16.7%) of 48 HCC samples, with complete loss of Fhit in only 1 case. There were no associations with abnormal transcripts, LOH, and Fhit expression. p53 mutations were identified in 9 of the 48 HCC cases. However, none of the cases displayed a G to T transversion at p53 codon 249. CONCLUSION: Aberrant FHIT transcripts were more common in HCC tissues as compared to non-cancerous liver tissues. However, Fhit expression was lost or reduced in a minor fraction of HCC tissues, while it was strongly expressed in non-cancerous liver ***, our study suggests that FHIT plays a role in relatively few HCC cases in South Korea.

关键词： Fragile histidine triad Aberrant transcripts Microsatellite instability Protein expression Hepatocellular carcinoma