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Micro-accelerometer Based on Vertically Movable Gate Field Effect Transistor

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Nano-Micro Letters 2015年第3期7卷 282-290页

作者： Heung seok kang kang-Hee lee Dong-Youk Yang Byoung Hee You In-Hyouk Song Korea Atomic Energy Research Institute LOGTECH Co. Ltd 914 Gumgang Hightech Valley 1st Department of Engineering Technology Texas State University601 University Dr. San Marcos TX 78666 USA

A vertically movable gate field effect transistor(VMGFET) is proposed and demonstrated for a microaccelerometer application. The VMGFET using air gap as an insulator layer allows the gate to move on the substrate vertically by external forces. Finite element analysis is used to simulate mechanical behaviors of the designed structure. For the simulation, the ground acceleration spectrum of the 1952 Kern County Earthquake is employed to investigate the structural integrity of the sensor in vibration. Based on the simulation, a prototype VMGFET accelerometer is fabricated from silicon on insulator wafer. According to current–voltage characteristics of the prototype VMGFET, the threshold voltage is measured to be 2.32 V, which determines the effective charge density and the mutual transconductance of1.545910-8C cm-2and 6.59 m A V-1, respectively. The device sensitivity is 9.36–9.42 m V g-1in the low frequency,and the first natural frequency is found to be 1230 Hz. The profile smoothness of the sensed signal is in 3 d B range up to1 k Hz.

关键词： MEMS Micro-accelerometer Suspended gate FET Vertically movable gate FET VMGFET

Do microRNA 96, 145 and 221 expressions really aid in Lhe prognosis of prostate carcinoma？

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Asian Journal of Andrology 2012年第5期14卷 752-757页

作者： Sung Gu kang Young Ran Ha Seo Jin Kim seok Ho kang Hong seok Park Jeong Gu lee Jun Cheon Department of Urology Korea University College of Medicine Seou1136-705 Republic of Korea and 2Department of Pathology Korea University College of Medicine Seoul 136 705 Republic of Korea Department of Pathology Korea University College of Medicine Seoul 136705 Republic of Korea

MicroRNAs （miRs） are small noncoding RNAs that have been reported to be premising diagnostic tools. We used quantitative real-time reverse transcription PCR （RT-qPCR） to analyze differentially expressed miRNAs in prostate tumor samples to determine its prognostic value. From 2007 to 2009, tumor tissues were obtained from 73 radical prostatectomy specimens. Differentially expressed miR-96, -145 and -221 were validated by TaqMan RT-qPCR using all 73 tissues. The prognostic value was assessed in terms of biochemical recurrence using Kaplan-Meier and Cox regression analyses. For our patient cohort, the mean age was 64.7 years （50-76 years） and the mean prostate-specific antigen （PSA） was 7.5 ng m1-1. During the follow-up period （mean, 19.4 months）, 14 of 73 （19.2%） patients developed biochemical recurrence. Expression of miR-96, -145 and -221 correlated strongly with each other, but there were no correlations between miRNA expression and clinicopathologic parameters. Kaplan-Meier survival curves using the log-rank test showed a decreased biochemical recurrence-free interval with pathologic stage （P〈O.O01）. In addition, patients with Gleason scores over 8, compared with those with a Gleason score of 6, showed a decreased biochemical recurrence-free interval in Kaplan-Meier analysis （P=O.O01）. However, expression of miR-96, -145 and -221 did not correlate with the biochemical recurrence interval in Kaplan-Meier survival curves or by multivariate analysis using the Cox proportional hazard regression model, either. In conclusion, we did not observe a significant correlation between the expression of miR-96, -145 and -221 and clinicopathologic parameters. To utilize miRNA as a diagnostic tool in clinical practice, more research is needed to understand miRNA mechanisms, identify miRNA targets, and further characterize miRNA function.

关键词： microRNA prognosis prostate cancer recurrence

Prospect of developing Nd-Fe-B-type magnet with high electrical resistivity

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Rare Metals 2020年第1期39卷 2-12页

作者： Hae-Woong Kwon Min-seok kang Department of Materials Science and Engineering Pukyong National UniversityBusan48547Republic of Korea

Nd-Fe-B-type magnet is exclusively used as a rotor magnet in the traction motor of hybrid electric vehicle(HEV)and electric vehicle(EV),but its overly high operating temperature is a lingering problem attached to the *** major cause of the high operating temperature is eddy current,which is readily generated in the highly conductive metallic magnet under alternating magnetic field from stator *** this article,temperature rise in the Nd-Fe-B-type magnet with varying electrical resistivity under alternating magnetic field is discussed with the intention of highlighting the importance of enhancing the electrical resistivity for reducing the operating temperature of the Nd-Fe-B-type rotor *** rise in the Nd-Fe-B-type magnet(dielectric salt-added die-upset magnet)with high electrical resistivity is noticeably lower compared to the magnet(commercial sintered rotor magnet)with lower electrical resistivity,substantiating the theory that enhancing the electrical resistivity in the rotor magnet is fairly effective for suppressing the over-rise of its operating temperature during ***-upset process is revealed to be particularly pertinent for the fabrication of highly dense salt-added magnet with high electrical resistivity.

关键词： Rare-earth magnet Nd-Fe-B-type magnet Rotor magnet Operating temperature Eddy current Electrical resistivity

Inhibitory effects of rapamycin on the different stages of hepatic fibrosis

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World Journal of Gastroenterology 2014年第23期20卷 7452-7460页

作者： Yun Jeung Kim Eaum seok lee seok Hyun Kim Heon Young lee Seung Moo Noh Dae Young kang Byung seok lee Department of Internal Medicine Chungnam National University School of MedicineDaejeon 301-721South Korea Department of Surgery Chungnam National University School of MedicineDaejeon 301-721South Korea Department of Pathology Chungnam National University School of MedicineDaejeon 301-721South Korea

AIM: To investigate and compare the inhibitory effects of rapamycin in the different stages of liver fibrosis.

关键词： Liver cirrhosis Sirolimus Transforming growth factor beta Platelet-derived growth factor Ribosomal protein S6 kinases

Fe-based high-entropy alloy with excellent mechanical properties enabled by nanosized precipitates and heterogeneous grain distribution

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Journal of Materials Science & Technology 2024年第14期181卷 71-81页

作者： Heechan Jung Sangwon lee Taehyeok kang Alireza Zargaran Pyuck-Pa Choi seok Su Sohn Department of Materials Science and Engineering Korea UniversitySeoul 02841Republic of Korea Department of Materials Science and Engineering Korea Advanced Institute of Science and TechnologyDaejeon 34141Republic of Korea Graduate Institute of Ferrous and Energy Materials Technology Pohang University of Science and TechnologyPohang 37673Republic of Korea

High-entropy alloys(HEAs)consisting of CoCrFeNiAlTi systems,with a face-centered cubic(FCC)matrix reinforced by ordered L12 precipitates,have demonstrated exceptional strength-ductility ***,the current compositional design of HEAs heavily relies on high Ni and Co contents,compro-mising the balance between properties and ***,it is crucial to optimize the cost-performance trade-offby fine-tuning the range of Fe,Co,and Ni,while maintaining excellent strength-ductility *** this study,we propose a novel Fe-based HEA with nanosized precipitates and a heteroge-neous grain distribution,achieving a strength-ductility combination comparable to state-of-the-art Ni-or Co-based *** alloy benefits from both precipitation hardening and hetero-deformation-induced strengthening attributed to the heterogeneous grain distribution,resulting in excellent yield strength of 1433 MPa,tensile strength of 1599 MPa,and ductility of 22%.The microstructural evolution and its in-fluence on mechanical properties are unraveled with respect to the observation of precipitate-dislocation interaction and hetero-deformation-induced stress(HDI stress)*** study suggests that the challenge of balancing properties and cost can be addressed through optimized compositional and mi-crostructural design.

关键词： High-entropy alloys Precipitation Heterogeneous microstructure Mechanical property HDI stress

Wire-Shaped 3D-Hybrid Supercapacitors as Substitutes for Batteries

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Nano-Micro Letters 2020年第2期12卷 211-223页

作者： Kyeong‑Nam kang Ananthakumar Ramadoss Jin‑Wook Min Jong‑Chul Yoon Deokjung lee seok Ju kang Ji‑Hyun Jang School of Energy and Chemical Engineering Low Dimensional Carbon Materials CenterUlsan National Institute of Science and TechnologyUlsan 44919Republic of Korea Laboratory for Advanced Research in Polymeric Materials Central Institute of Plastic Engineering and TechnologyBhubaneswar 751024India School of Mechanical Aerospace and Nuclear EngineeringUlsan National Institute of Science and TechnologyUlsan 44919Republic of Korea

We report a wire-shaped three-dimensional(3D)-hybrid supercapacitor with high volumetric capacitance and high energy density due to an interconnected 3D-configuration of the electrode allowing for large number of electrochemical active sites,easy access of electrolyte ions,and facile charge transport for flexible wearable *** interconnected and compact electrode delivers a high volumetric capacitance(gravimetric capacitance)of 73 F cm−3(2446 F g−1),excellent rate capability,and cycle *** 3D-nickel cobalt-layered double hydroxide onto 3D-nickel wire(NiCo LDH/3D-Ni)//the 3D-manganese oxide onto 3D-nickel wire(Mn3O4/3D-Ni)hybrid supercapacitor exhibits energy density of 153.3 Wh kg−1 and power density of 8810 W kg−*** red lightemitting diode powered by the as-prepared hybrid supercapacitor can operate for 80 min after being charged for tens of seconds and exhibit excellent electrochemical stability under various deformation *** results verify that such wire-shaped 3D-hybrid supercapacitors are promising alternatives for batteries with long charge–discharge times,for smart wearable and implantable devices.

关键词： Three-dimensional(3D)metal current collector Flexible hybrid supercapacitor Wire-shaped supercapacitor High energy density device Fast charging energy storage system

Tyrosine-mediated analog resistive switching for artificial neural networks

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Nano Research 2023年第1期16卷 858-864页

作者： Min-Kyu Song seok Daniel Namgung Hojung lee Jeong Hyun Yoon Young-Woong Song kang Hee Cho Yoon-Sik lee Jong-seok lee Ki Tae Nam Jang-Yeon Kwon School of Integrated Technology Yonsei UniversityIncheon 21983Republic of Korea Department of Mechanical Engineering Massachusetts Institute of TechnologyMA 02139USA Research Laboratory of Electronics Massachusetts Institute of TechnologyMA 02139USA Department of Materials Science and Engineering Seoul National UniversitySeoul 08826Republic of Korea Soft Foundry Seoul National UniversitySeoul 08826Republic of Korea School of Chemical and Biological Engineering Seoul National UniversitySeoul 08826Republic of Korea

The fourth industrial revolution indispensably brings explosive data processing and storage;thus,a new computing paradigm based on artificial intelligence-enabling device structure is urgently *** have received considerable attention in this regard because of their ability to process and store data at the same ***,fundamental problems with abrupt switching characteristics limit their practical *** address this problem,we utilized the concept of metaplasticity inspired by biosystems and observed gradual switching in the peptide-based memristor at high proton *** unexpectedly high slope value>1.7 in the logI–V curve at low voltage(≤400 mV)was considered the main origin,and it might arise from the modulatory response of proton ions on the threshold of Ag ion migration in the peptide *** the obtained gradual switching property at high proton conductivity,the device showed significantly increased accuracy of image recognition(~82.5%).We believe that such a demonstration not only contributes to the practical application of neuromorphic devices but also expands the bioinspired functional synthetic platform.

关键词： artificial synapse neuromorphic computing proton conductor peptide materials artificial neural network

Comparative study on discharge conditions in micro-hole electrical discharge machining of tungsten carbide (WC-Co) material

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中国有色金属学会会刊：英文版 2009年第B09期19卷 114-118页

作者： Hyun-seok TAK Chang-Seung HA Dong-Hyun KIM Ho-Jun lee Hae-June lee Myung-Chang kang National Core Research Center for Hybrid Materials Solution Pusan National University Department of Electrical Engineering Pusan National University

WC-Co is used widely in die and mold industries due to its unique combination of hardness, strength and wear-resistance. For machining difficult-to-cut materials, such as tungsten carbide, micro-electrical discharge machining(EDM) is one of the most effective methods for making holes because the hardness is not a dominant parameter in EDM. This paper describes the characteristics of the discharge conditions for micro-hole EDM of tungsten carbide with a WC grain size of 0.5 μm and Co content of 12%. The EDM process was conducted by varying the condenser and resistance values. A R-C discharge EDM device using arc erosion for micro-hole machining was suggested. Furthermore, the characteristics of the developed micro-EDM were analyzed in terms of the electro-optical observation using an oscilloscope and field emission scanning electron microscope.

关键词：电火花加工碳化钨钴难切削材料硬质合金放电扫描电子显微镜微孔模具行业

Characteristic evaluation of Al_2O_3/CNTs hybrid materials for micro-electrical discharge machining

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Transactions of Nonferrous Metals Society of China 2011年第A01期21卷 28-32页

作者： Hyun-seok TAK Chang-Seung HA Ho-Jun lee Hyung-Woo lee Young-Keun JEONG Myung-Chang kang National Core Research Center for Hybrid Materials Solution Pusan National University Department of Electrical Engineering Pusan National University

The characteristic evaluation of aluminum oxide （A1203）/carbon nanotubes （CNTs） hybrid composites for micro-electrical discharge machining （EDM） was described. Alumina matrix composites reinforced with CNTs were fabricated by a catalytic chemical vapor deposition method. A1203 composites with different CNT concentrations were synthesized. The electrical characteristic of A1203/CNTs composites was examined. These composites were machined by the EDM process according to the various EDM parameters, and the characteristics of machining were analyzed using field emission scanning electron microscope （FESEM）. The electrical conductivity has a increasing tendency as the CNTs content is increased and has a critical point at 5% A1203 （volume fraction）. In the machining accuracy, many tangles of CNT in A1203/CNTs composites cause violent spark. Thus, it causes the poor dimensional accuracy and circularity. The results show that conductivity of the materials and homogeneous distribution of CNTs in the matrix are important factors for micro-EDM of A1203/CNTs hybrid composites.

关键词： A1203/CNTs hybrid materials micro-electrical discharge machining micro-hole electrical conductivity