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Investigation on the magnetomechanical behavior of trilayered GM actuator

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Journal of Rare Earths 2008年第2期26卷 264-267页

作者： heung-Shik Lee chongdu cho Department of Mechanical Engineering Inha University Yonghyun-dong Nam-ku Incheon 402-751 South Korea

In this article, it was suggested a TbFe/Co/Dy trilayered GM （Giant Magnetostrictive） film type actuator and investigated the magnetomechanical characteristics of the actuator for micro application. The trilayered films were fabricated at different thickness ratios to get an optimized structure. TbFe had positive GM properties, and cobalt, dysprosium layers made the magnetostriction property of composite film increase in low magnetic field. To fabricate the Si based microactuator with trilayered film, micromachining processes including RIE （Reactive Ion Etching） and selective DC magnetron sputtering techniques were combined. The deposited film thicknesses were measured by X-ray diffraction （XRD）. As a result, the magnetization of the film on the fabricated actuator was observed to characterize the magnetic properties of the TbFe/Co/Dy film using VSM （Vibrating Sample Magnetometer）. The magnetostriction of the actuator was determined by measuring the differences of curvature of the film coated silicon substrates using the optical cantilever method, and the deflections were also estimated under the external magnetic field lower than 0.5T for micro-system applications.

关键词： GM actuator magnetostriction trilayered film magnetron sputtering magnetization rare earths

Optimization of image capturing method of wear particles for condition diagnosis of machine parts

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中国有色金属学会会刊：英文版 2009年第B9期19卷 215-219页

作者： Yon-Sang cho heung-Sik PARK Department of Materials Engineering Dong-A University

Wear particles are inevitably occurred from moving parts, such as a piston-cylinder made from steel or hybrid materials. And a durability of these parts must be evaluated. The wear particle analysis has been known as a very effective method to foreknow and decide a moving situation and a damage of machine parts by using the digital computer image processing. But it is not laid down to calculate shape parameters of wear particle and wear volume. In order to apply image processing method in a durability evaluation of machine parts, it needs to verify the reliability of the calculated data by the image processing and to lay down the number of images and the amount of wear particles in one image. In this work, the lubricated friction experiment was carried out in order to establish the optimum image capture with the 1045 specimen under experiment condition. The wear particle data were calculated differently according to the number of image and the amount of wear particle in one image. The results show that capturing conditions need to be more than 140 wear particles in one image and over 40 images for the reliable data. Thus, the capturing method of wear particles images was optimized for condition diagnosis of machine moving parts.

关键词：计算机图像处理磨损颗粒机械零件优化条件诊断方法拍摄图像处理方法运动部件

Muscular atrophy and weakness in the lower extremities in Behçet’s disease: A case report and review of literature

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World Journal of Clinical Cases 2021年第20期9卷 5647-5654页

作者： koh-Woon Kim Jae-heung cho Department of korean Medicine Rehabilitation College of Korean MedicineKyung Hee UniversitySeoul 02447South Korea

BACKGROUND In Behçet’s disease(BD),very few cases of muscular involvement have been reported *** natural history and therapeutic protocol for muscular involvement in BD are obscure due to the low incidence of peripheral neuropathy or myopathy in *** purpose of our study was to report a rare case of BD with chronic,focal forms of neuromyopathy and review the relevant *** SUMMARY We herein report the case of a 54-year-old man who presented with progressive muscular atrophy and weakness of both thighs 2 years after the presentation of the cardinal symptoms of *** past medical history,electrophysiological study,neurological examination,blood tests,magnetic resonance imaging study,and histological exam were performed for the differential *** literature on muscular involvement in BD was *** examination revealed that muscular involvement was predominantly localized in the proximal parts of the lower *** enhancement of several thigh muscles was observed on magnetic resonance imaging,which corresponded with the clinical *** study of one of the enhanced muscles showed denervation atrophy of the muscle with superimposed myopathic changes,while electrophysiological studies only suggested *** To our knowledge,this is the first case of neurogenic muscular atrophy with a specific set of clinical,radiological,electrophysiological,and histological findings reported in BD.

关键词： Behçet’s disease Muscular atrophy Muscular weakness Neuropathy Myopathy Case report

Magnetostrictive Flexible Thin Film Structure for Micro Devices

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Journal of Rare Earths 2007年第S1期25卷 182-185页

作者： heung-Shik Lee chongdu cho Department of Mechanical Engineering Inha University Yonghyun-dong Nam-kuIncheon 402-751 South Korea

Polyimide (Kapton, Dupont Corp.) based magnetostrictive thin film structures were designed and fabricated for micro device applications. In particular the growth of films on flexible substrates was studied to allow a simple integration of the system in miniaturized magnetostrictive devices. The films were fabricated on different substrates to compare their different magnetic and structural properties. It showed much more magnetostriction and higher impact resistance results compared with traditional Si based film type actuators. In the fabrication process, amorphous TbDyFe films with thicknesses of 500 nm, 1 μm, 1.5 μm respectively, were deposited on the designed substrate by DC magnetron sputtering. During sputtering process the substrate holder was maintained at room temperature. After the sputter process, X-ray diffraction studies were also carried out to determine the film structure and thickness of the sputtered film. At last, magnetization from VSM (Vibrating Sample Magnetometer) and magnetostriction from optical cantilever method of each structure were measured to estimate the magneto-mechanical characteristics under the external magnetic field lower than 0.7 T for micro-system applications.

关键词： magnetostrictive thin film micro device flexible polyimide substrate rare earths

Iatrogenic giant pseudomeningocele of the cervical spine:A case report

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World Journal of Clinical Cases 2021年第31期9卷 9686-9690页

作者： koh-Woon Kim Jae-heung cho Department of korean Medicine Rehabilitation College of Korean MedicineKyung Hee UniversitySeoul 02447South Korea

BACKGROUND Only a few cases of giant pseudomeningoceles have been reported in the ***,we report a giant pseudomeningocele of the cervical spine that was found after cervical laminectomy for an epidural hematoma following epidural *** SUMMARY A 47-year-old man presented with recurrent neck pain and posterior neck swelling after spinal *** resonance imaging of the cervical spine revealed fluid collection(5.6 cm×6.6 cm×11.2 cm)at the C3-6 level;this proved to be a *** related to the pseudomeningocele resolved following dural repair and fat graft *** Although rare,pseudomeningocele is a possibility in patients with recurrent back pain,radicular pain,or a persistent headache following spinal *** attention should be paid throughout the spinal procedure,whether conservative or non-conservative.

关键词： Iatrogenic spinal pseudomeningocele Giant pseudomeningocele Cervical spine C3-6 level Cervical laminectomy Case report

Small-scale analysis of brittle-to-ductile transition behavior in pure tungsten

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Journal of Materials Science & Technology 2022年第10期105卷 242-258页

作者： Yeonju Oh Won-Seok ko Nojun Kwak Jae-il Jang Takahito Ohmura heung Nam Han Department of Materials Science and Engineering&Research Institute of Advanced Materials Seoul National UniversitySeoul 08826South Korea School of Materials Science and Engineering University of UlsanUlsan 44610South Korea Division of Materials Science and Engineering Hanyang UniversitySeoul04763South Korea National Institute for Materials Science 1-2-1 SengenTsukubaIbaraki 305-0047Japan

Tungsten as a material exhibits broad and increasingly important applications;however,the characterization of its ductile-to-brittle transition(BDT)is currently limited to large-scale scenarios and destructive *** this study,we overcome this challenge by implementing small-scale techniques to provide a comprehensive understanding of the BDT behavior of pure *** order to predict the failure mode at various temperature ranges,the practical fracture analysis diagram has been proposed to describe the resistance to shear flow and cracking behavior with *** temperature nano-indentation tests have provided the inherent mechanical responses corresponding to the maximum shear stress at various temperatures,which is required for dislocation activities in an atomic scaled activation *** one hand,atomistic simulations have provided the temperature dependence of brittle fracture stress,where the atomic bonds break due to intergranular or intragranular *** considered four tungsten specimens having various microstructures prepared using different processing conditions of cold-rolling and post-annealing,and their BDT ranges were inferred using the obtained fracture analysis diagram with the statistical data *** fracture analysis diagram of each specimen obtained were compared with the direct observation of fracture responses in macroscopic mechanical tests,which conclusively indicated that the small-scale inherent mechanical properties are greatly relevant to the macroscopic BDT behavior in pure *** on the BDT estimations by small-scale characterization,we provided further insights into the factors affecting the BDT behavior of tungsten,focusing on the contributions of different types of dislocations.

关键词： Brittle-to-ductile transition Nano-indentation Molecular dynamics Dislocation Tungsten

Material properties of friction stir spot welded joints of dissimilar aluminum alloys

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中国有色金属学会会刊：英文版 2012年第S3期22卷 605-613页

作者： Chi-Sung JEON Sung-Tae HONG Yong-Jai KWON Hoon-Hwe cho heung Nam HAN Technical Research Center Hyundai Steel Company School of Mechanical Engineering University of Ulsan Department of Materials Science and Engineering University of Ulsan Department of Materials Science and Engineering Seoul National University

Mechanical properties and material mixing patterns of friction stir spot welded (FSSW) joints of dissimilar aluminum alloys were *** aluminum alloys typically used in automotive applications,5052-H32 and 6061-T6,were *** the experiment,the process parameters including the z-axis force and torque histories were measured as a function of the tool *** mechanical properties were investigated by microhardness measurements of the joint,and the material mixing in the stir zone was investigated by *** experimental results illustrate different process parameter histories,material mixing in the stir zone and material properties including microhardness distributions for FSSW joints of dissimilar aluminum alloys,likely due to different mechanical behaviors of the selected aluminum alloys in the FSSW process temperature range.

关键词： friction stir spot welding dissimilar aluminum alloys force histories torque histories microhardness

Multi-Bandgap Monolithic Metal Nanowire Percolation Network Sensor Integration by Reversible Selective Laser-Induced Redox

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Nano-Micro Letters 2022年第3期14卷 216-228页

作者： Junhyuk Bang Yeongju Jung Hyungjun Kim Dongkwan Kim Maenghyo cho Seung Hwan ko Applied Nano and Thermal Science Lab Department of Mechanical EngineeringSeoul National University1 Gwanak‑roGwanak‑guSeoul 151‑742Republic of Korea Department of Mechanical Engineering Seoul National University1 Gwanak‑roGwanak‑guSeoul 08826Republic of Korea Institute of Advanced Machines and Design Institute of Engineering ResearchSeoul National UniversitySeoul 08826Republic of Korea

Active electronics are usually composed of semiconductor and metal electrodes which are connected by multiple vacuum deposition steps and photolithography ***,the presence of interface of dissimilar material between semiconductor and metal electrode makes various problems in electrical contacts and mechanical *** ideal electronics should not have defective interfaces of dissimilar *** this study,we developed a novel method to fabricate active electronic components in a monolithic seamless fashion where both metal and semiconductor can be prepared from the same monolith material without creating a semiconductor-metal interface by reversible selective laser-induced redox(rSLIR)***,rSLIR can control the oxidation state of transition metal(Cu)to yield semiconductors with two different bandgap states(Cu_(2)O and CuO with bandgaps of 2.1 and 1.2 eV,respectively),which may allow multifunctional sensors with multiple bandgaps from the same *** novel method enables the seamless integration of single-phase Cu,Cu_(2)O,and CuO,simultaneously while allowing reversible,selec-tive conversion between oxidation states by simply shining laser ***,we fabricated a flexible monolithic metal-semiconduc-tor-metal multispectral photodetector that can detect multiple *** unique monolithic characteristics of rSLIR process can provide next-generation electronics fabrication method overcoming the limitation of conventional photolithography methods.

关键词： Monolithic integration Seamless interface Multi-bandgap nanowire Laser-induced redox Multispectral photodetector

MYB46-Mediated Transcriptional Regulation of Secondary Wall Biosynthesis

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Molecular Plant 2012年第5期5卷 961-963页

作者： Jae-heung ko Won-Chan Kim Joo-Yeol Kim Sung-Ju Ahn Kyung-Hwan Han Department of Plant and Environmental New Resources Kyung Hee University Yongin Korea Bioenergy Center Kyung Hee University Yongin Korea Department of Horticulture and Department of Forestry Michigan State University East Lansing MI 48824-1222 USA DOE-Great Lakes Bioenergy Research Center Michigan State University East Lansing MI 48824-1222 USA Department of Bioenergy Science and Technology (WCU) Chonnam National University 333 Yongbongro Buk-gu Gwangju 500-757 Korea

Formation of secondary wall requires coordinated transcrip- tional regulation of the genes involved in the biosynthesis of major secondary wall components （e.g. cellulose, hemicellu- lose, and lignin）. Even though many aspects of plant biology have been extensively elucidated using various model spe- cies, our current understanding of secondary wall formation is limited.

关键词： Biosynthesis Regulation Wall