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Numerical simulation and experimental study for rheo-forged component using direct and indirect die system

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Transactions of Nonferrous Metals Society of China 2010年第9期20卷 1799-1804页

作者： h.h.kim C.G.KANG Precision Manufacturing Systems Division Pusan National University School of Mechanical Engineering Pusan National University

Sand casting and die casting processes have been used widely for complex automotive products such as knuckle, arm, ***, a part fabricated by casting has limited strength due to manufacturing defects such as the dendrite structure, segregation and *** an attempt to offer a solution to these problems, forging has been used as an alternative ***, the forging process provides limited formability for complex shape ***-forging of metal offers not only superior mechanical strength but also requires significantly lower machine loads than solid forming *** order to produce semi-solid materials of the desired microstructure, a stirring process is applied during solidification of molten *** results of an A356 aluminum alloy sample, which are obtained by experiment and by simulation using DEFORM 3D, are present.

关键词： rheo-forging A356 alloy formability forming defects

Obturator hernia-a rare etiology of lateral thigh pain:A case report

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World Journal of Clinical Cases 2021年第34期9卷 10728-10732页

作者： jun Young kim Min Cheol Chang Department of Physical Medicine and Rehabilitation College of MedicineYeungnam UniversityTaegu 705-717South Korea

BACKGROUND Lateral thigh pain is a common complaint in patients visiting a pain ***,we describe the case of a patient with lateral thigh pain caused by an obturator *** SUMMARY An 83-year-old woman visited the emergency room with suddenly aggravated right lateral thigh *** resonance imaging of the thigh revealed no abnormal findings in the lateral thigh ***,an obturator hernia between the pectineus and obturator externus muscles was observed by *** computed tomography revealed a herniated small bowel with an incarceration point at the right obturator canal and a dilated loop of the small bowel *** of the right inguinal region revealed a distended bowel loop in the right pectineus *** Our report provides clinicians with information that an obturator hernia can cause lateral thigh pain.

关键词： Obturator hernia Pain Magnetic resonance image Computed tomography Ultrasonography Case report

Understanding secondary phase inclusion and composition variations in the microstructure design of n-type Bi_(2)Te_(3) alloys via selective dissolution of KCl

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Journal of Advanced Ceramics 2023年第12期12卷 2360-2370页

作者： Gwang Min Park Seunghyeok Lee jun-Yun Kang Seung-hyub Baek heesuk kim Jin-Sang kim Seong Keun kim KU-KIST Graduate School of Converging Science and Technology Korea UniversitySeoul 02841Republic of Korea Electronic Materials Research Center Korea Institute of Science and TechnologySeoul 02792Republic of Korea Department of Materials Science and Chemical Engineering Hanyang UniversityAnsan 15588Republic of Korea Ferrous Alloy Department Korea Institute of Materials ScienceChangwon 51508Republic of Korea Soft hybrid Materials Research Center Korea Institute of Science and TechnologySeoul 02792Republic of Korea Institute of Advanced Composite Materials Korea Institute of Science and TechnologyWanju 55324Republic of Korea

This study investigated the effects of KCl treatment on microstructure and thermoelectric properties of n-type Bi_(2)Te_(2.7)Se_(0.3)(BTS)thermoelectric *** innovative KCl treatment was originally intended to introduce nanopores through selective dissolution of KCl from a mixture of thermoelectric materials and ***,it unexpectedly induced substantial variations in material composition and microstructure during the subsequent spark plasma sintering(SPS)*** groups adsorbed on the powder surface during the dissolution resulted in the emergence of a Bi_(2)TeO_(5) secondary phase within the BTS matrix after the SPS process at 450℃.The concentration of Bi_(2)TeO_(5) increased with an increase in the KCl ***,a remarkable grain growth occurred at low KCl concentrations,likely due to the liquid-phase formation in a Te-rich composition during ***,excessive Bi_(2)TeO_(5) at higher KCl concentrations hindered grain *** variations in the microstructure had complex effects on electrical properties:The TeBi antisite defects increased the electron concentration,and Bi_(2)TeO_(5) reduced electron ***,the lattice thermal conductivity decreased due to the presence of Bi_(2)TeO_(5),from 0.8 W·m^(−1)·K^(−1) at 298 K for the pristine BTS to 0.6 W·m^(−1)·K^(−1) at 298 K for BTS treated with 1 wt%*** insights allowed precise adjustments of the electrical and thermal conductivities,leading to an enhancement in the maximum value of figure-of-merit(ZT)from 0.76 to 0.96 through the selective dissolution of KCl *** believe that our observations potentially enable advances in thermoelectric materials by engineering microstructures.

关键词： thermoelectric materials Bi_(2)Te_(3) Bi_(2)TeO_(5) grain growth n-type KCl

BIOCOMPATIBILITY OF A PDMS-COATED MICRO-DEVICE:BLADDER VOLUME MONITORING SENSOR

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Chinese Journal of Polymer Science 2012年第2期30卷 242-249页

作者： Dong Sup Lee Su Jin kim jun ho Sohn In Gul kim Sae Woong kim Dong Wan Sohn Jong hyun kim Bumkyoo Choi Department of Urology St.Vincent's HospitalCollege of Medicinethe Catholic University of KoreaSuwonKorea Department of Urology Seoul St.Mary's HospitalCollege of Medicinethe Catholic University of KoreaSeoulKorea Department of Urology Yeouido St.Mary's HospitalCollege of Medicinethe Catholic University of KoreaSeoulKorea Department of Mechanical Engineering Sogang UniversitySeoulKorea

We evaluated the biocompatibility of a dimethylpolysiloxane-coated micro-device which had been designed for monitoring real-time bladder volume in previous studies. The extract assay with dimethylpolysiloxane which had been used for coating the micro-device to measure the bladder volume was performed as an in vitro cytotoxicity test. For in vivo biocompatibility testing, the inflammatory responses around the implantation site of the micro-device in subcutaneous tissue of rat were assessed by light microscope with h＆E stain and fluorescence microscope with ED1 stain and von Willebrand factor stain. The averages of cell viability in dimethylpolysiloxane group were 84.6% and 82.3% at 24 h and 72 h incubation, respectively. The qualitative evaluations with light and fluorescence microscope revealed that the inflammatory changes peaked during 2 weeks but almost disappeared at 4 weeks after implantation of devices. The quantitative evaluations for granulation layer formation and neovascularization showed that the thickness of the layer in dimethylpolysiloxane group peaked during 2 weeks but it came to be stabilized at 4 weeks as thin as at 2 weeks in control group, and the frequency of neovascularization was higher in dimethylpolysiloxane group than in control group but it was not increased with time. The dimethylpolysiloxane-coated micro-device is thought be a reliable bio-medical device.

关键词： Dimethylpolysiloxane Devices Biocompatibility testing.

Power management unit chip design for automobile active-matrix organic light-emitting diode display module

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Journal of Central South University 2009年第4期16卷 621-628页

作者： kim J h PARK J h kim J h CAO T V LEE T Y BAN h J YANG K kim h G hA P B kim Y h Department of Electronic Engineering Changwon National University 9 Sarim-Dong Changwon 641-773 Korea Denso PS Electronics Corporation 47 Seongsan-Dong Changwon 641-315 Korea

A power management unit （PMU） chip supplying dual panel supply voltage, which has a low electro-magnetic interference （EMI） characteristic and is favorable for miniaturization, is designed. A two-phase charge pump circuit using external pumping capacitor increases its pumping current and works out the charge-loss problem by using bulk-potential biasing circuit. A low-power start-up circuit is also proposed to reduce the power consumption of the band-gap reference voltage generator. And the ring oscillator used in the ELVSS power circuit is designed with logic devices by supplying the logic power supply to reduce the layout area. The PMU chip is designed with MagnaChip＇s 0.25 μ high-voltage process. The driving currents of ELVDD and ELVSS are more than 50 mA when a SPICE simulation is done.

关键词： DC-DC converter AMOLED charge pumping power management unit (PMU) dual panel supply voltage

Surface plasmon enhancement of photoluminescence in photo-chemically synthesized graphene quantum dot and Au nanosphere

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Nano Research 2016年第6期9卷 1866-1875页

作者： Byeongho Park Sun jun kim Ji Soo Sohn Min Sik Nam Shinill Kang Seong Chan jun School of Mechanical Engineering Yonsei University 50 Yonsei-ro Seodaemun-gu Seou1120-749 Republic of Korea

Graphene quantum dots （GQDs） are promising candidates for potential applications such as novel optoelectronic devices and bio-imaging. however, insufficient light absorption to exhibit their intriguing characteristics. The strong confinement of light caused by the Au nanoparticles as an antenna can considerably boost the light absorption. With the assistance of ultraviolet irradiation, we prepared bluish-green luminescent nanospheres by the hybridiza- tion of GQD and Au nanoparticles （GQD/Au）. These nanospheres showed a photoluminescence quantum yield of up to 26.9%. The GQD/Au nanospheres were synthesized using a solution of GQDs and hAuC14 by a photochemical method with the reduction of GQDs and the formation of metallic Au. The GQDs and Au nanopartides self-assembled and aggregated into nanospheres via aurophilicity and hydrogen bonding interactions. The average size of the GQD/Au nanospheres was found to be in the range of 150-170 nm, which is much larger than that of the pristine GQDs （4-7 nm）. The GQD/Au nanospheres exhibited an absorption band at 541 nm, which indicates the presence of Au in the nanospheres. The typical absorbance features of GQDs were observed near 236 and 303 nrn. The photoluminescence characteristics were investigated using the excitation and emission spectra. The GQD/Au nanospheres exhibited two emission peaks at 468 and 529 nm in the visible range. The green fluorescent peak located at 529 nm was newly generated by the hybridization. The GQD/Au nanospheres showed an emission efficiency which was two times more than that of the intrinsic GQDs. The reason for this increase was the surface plasmon resonance from the Au particles, which improved the fluorescence property of the resulting nanospheres. These nanospheres can be perceived as outstanding candidates for applications such as displays, optoelectronic devices, and imaging of the biological samples with high emission intensity.

关键词： graphene quantum dot gold nanosphere photoluminescence UV irradiation

Anomalously Strong Scattering of Spontaneously Produced Laser Radiation in the First Free-Electron Laser and Study of Free-Electron Two-Quantum Stark Lasing in an Electric Wiggler with Quantum-Wiggler Electrodynamics

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Chinese Physics Letters 2006年第6期23卷 1422-1425页

作者： S. h. kim Department of Physics University of Texas at Arlington PO Box 19059 Arlington Texas 76019 USA

We calculate the scattering cross section of an electron with respect to the spontaneously produced laser radiation in the first free-electron laser （FEL） with quantum-wiggler electrodynamics （QWD）. The cross section is 1016 times the Thomson cross section, confirming the result obtained by a previous analysis of the experimental data. A QWD calculation show that spontaneous emission in an FEL using only an electric wiggler can be very strong while amplification through net stimulated emission is practically negligible.

关键词： CLASSICAL ELECTRODYNAMICS RELATIVISTIC ELECTRONS ThERMODYNAMICS EXPLANATION EMISSION

Electric-Wiggler-Enhanced Three-Quantum Scattering and the Output Power Affected by this Scattering in a Free-Electron Laser

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Chinese Physics Letters 2009年第1期26卷 58-61页

作者： S. h. kim 6300 Roundrock Trail #4203 Piano Texas 75023 USA

We derive the cross section of scattering through the three-quantum interaction of an electron with the incident laser field, the emitted photon, and an axial electrostatic field produced by the magnetic wiggler in the magnetic wiggler acting as the sole zeroth-order perturbing classical field in the first free-electron laser （FEL）. In the derivation, we apply quantum-wiggler electrodynamics （QWD）. We find that this scattering predominates the usual two-quantum scattering. The output power of spontaneous free-electron two-quantum Stark emission driven by the above electrostatic field attenuated by the three-quantum scattering agrees within a factor of 10 with the measured power in the case of the first FEL.

关键词： field emission molybdenum dioxide enhancement factor

Virtual Reality-Based Random Dot Kinematogram

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Computers, Materials & Continua 2021年第9期68卷 4205-4213页

作者： jun Ma hyo-jung kim Ji-Soo kim Eek-Sung Lee Min hong Department of Software Convergence Soonchunhyang UniversityAsan31538Korea Research Administration Team Seoul National University Bundang HospitalSeongnam13620Korea Dizziness Center Clinical Neuroscience CenterDepartment of NeurologySeoul National University Bundang HospitalSeongnam13620Korea Department of Neurology Seoul National University College of MedicineSeoul03080Korea Department of Neurology College of MedicineSoonchunhyang UniversityBucheon14584Korea Department of Computer Software Engineering Soonchunhyang UniversityAsan31538Korea

This research implements a random dot kinematogram(RDK)using virtual reality(VR)and analyzes the results based on normal *** motion perception is one of visual functions localized to a specific cortical area,the human motion perception area(human analogue for the middle temporal/middle superior temporal area)located in the parieto–occipito–temporal junction of the human *** RDK measures visual motion perception *** stimuli in conventional RDK methods are presented using a monitor screen,so these devices require a spacious dark room for installation and ***,VR technology has been implemented in different medical *** test method proposed in this study include a VR-based RDK that can independently measure human motion perception abilities without any spatial constraints via a VR head-mounted ***,the VR-based RDK was implemented,and the visual perception abilities of the normal subjects were measured based on varying *** both screen-and VR-based RDK tests,the easier the stimulus is,the higher the correct answer rate and the shorter the reaction *** significant differences in coherence thresholds were observed between the two test *** VRbased RDK proposed in this study can be used as a diagnosis tool for visual motion perception and neurodegenerative disorders affecting the posterior region of the brain.

关键词： Random dot kinematogram virtual reality visual psychophysics diagnostic device