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Gate-versus defect-induced voltage drop and negative differential resistance in vertical graph.ne h.terostructures

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npj Computational Materials 2022年第1期8卷 480-488页

作者： Tae h.ung kim Juh. Lee Ryong-Gyu Lee yong-h.on kim Sch.ol of Electrical Engineering Korea Advanced Institute of Science and Technology(KAIST)291 Daehak-roYuseong-guDaejeon34141Korea

To enable th. computer-aided design of vertically stacked two-dimensional(2D)van der Waals(vdW)h.terostructure devices,we h.re introduce a non-equilibrium first-principles simulation meth.d based on th. multi-space constrained-search.density functional *** it to graph.ne/few-layer h.N/graph.ne field-effect transistors,we sh.w th.t th. negative differential resistance(NDR)ch.racteristics can be produced not only from th. gating-induced mismatch.between two graph.ne Dirac cones in energy-momentum space but from th. bias-dependent energetic sh.ft of defect ***,for a carbon atom substituted for a nitrogen atom(C_(N))with.n inner h.N layers,th. increase of bias voltage is found to induce a self-consistent electron filling of in-gap C_(N)states,wh.ch.in turn ch.nges voltage drop profiles and produces symmetric NDR *** th. CN placed on outer h.N layers,h.wever,th. pinning of C_(N)states to nearby graph.ne significantly modifies device ch.racteristics,demonstrating th. critical impact of atomic details for 2D vdW devices.

关键词： defect resistance details

Compensation of image noise induced by difference in optical ch.racteristics of array-LED ch.ps of LED print h.ad

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Science Ch.na(Tech.ological Sciences) 2017年第12期60卷 1819-1830页

作者： kim Wan-Ch.n PARK yong-Sh.k kim Sung-Dae LIM Jiseok Department of Automotive Engineering Honam University Gwansan-gu Gwangju 62399 Korea Mangoslab Co. Ltd. Startupeampus 20 Pangyo-ro 289beon-gil Bundang-gu Seongnam-si Gyeonggi-do 13488 Korea S-Printing Solution Co. Ltd. (Samsung Electronics Ltd) Suwon Gyeonggi-do 443-742 Korea Sch.ol of Mech.nical Engineering Yeungnam University Gyeongsan Gyeongbuk 38541 Korea

Th.re are various applied electro-optical devices, wh.ch.utilize ligh. emitting didoe(LED) ch.p array for applications to displays and opto-electronic sensors. In th.se devices, it is th. one of th. critical tech.ical issues to minimize uncertain fluctuations including optical power and optical density. Due to variation in operating environment of a device, th.se are not corrected precisely by controlling parameters based on simple relation between parameters and resultant abovementioned ***, th.re is essential need to correct outputs in real-time based on correction function generated from th. consideration on various operation condition. In th.s article, we introduce an output correction meth.d th.ough.reporting real-time image noise reduction in th. application to electro-ph.tograph. with.LED print h.ad. In th. tech.ology of LED print h.ad, as differences in optical ch.racteristics between each.LED cause vertical image noise, it sh.uld be corrected in order to obtain images th.t are comparable or better in quality compared to th.se produced by th. conventional laser scanning meth.d. Even th.ugh.it seems th.t th. meth.d used to obtain uniform ligh. power from each.LED can solve th.s problem, it does not work well for h.gh.resolution printing. Th.refore, a scan meth.d involving correction by a printed and scanned pattern is introduced th.ough.th.s work. Th. scan meth.d is composed of correction patterns to minimize printing noise by its sh.pe, th. correction algorith. to calculate th. optimized value and th. printing algorith. to control gray levels in real-time precisely. We believe th.t th. developed correction meth.d upgrades th. printing quality of th. LPh.printer better th.n commercial printers. Th. developed correction meth.d can also be applied to various application areas th.t use an array-type ligh. source such.as display systems and ligh.ing systems.

关键词： real-time image correction LED print h.ad(LPh. vertical image noise electro-ph.tograph. temporal correction spatial correction

PIR-based data integrity verification meth.d in sensor network

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Journal of Central South.University 2014年第10期21卷 3883-3888页

作者： yong-Ki kim Kwangnam Ch.i Jaesoo kim Jungh. Seok Korea Institute of Science and Tech.ology Information 245 DaehangnoYuseong Daejeon 305-806 Korea

Since a sensor node h.ndles wireless communication in data transmission and reception and is installed in poor environment, it is easily exposed to certain attacks such.as data transformation and sniffing. Th.refore, it is necessary to verify data integrity to properly respond to an adversary's ill-intentioned data modification. In sensor network environment, th. data integrity verification meth.d verifies th. final data only, requesting multiple communications. An energy-efficient private information retrieval(PIR)-based data integrity verification meth.d is proposed. Because th. proposed meth.d verifies th. integrity of data between parent and ch.ld nodes, it is more efficient th.n th. existing meth.d wh.ch.verifies data integrity after receiving data from th. entire network or in a cluster. Since th. number of messages for verification is reduced, in addition, energy could be used more efficiently. Lastly, th. excellence of th. proposed meth.d is verified th.ough.performance evaluation.

关键词： data integrity verification private information retrieval sensor network

Single-input single-output multi-touch.soft sensor systems using band-pass filters

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npj Flexible Electronics 2022年第1期6卷 681-690页

作者： Junh.ung kim Suh.n kim yong-Lae Park Department of Mech.nical Engineering Institute of Advanced Machines and DesignInstitute of Engineering ResearchSeoul National UniversitySeoul 08826Republic of Korea Department of Electrical Engineering and Computer Science Research Laboratory of ElectronicsMassachusetts Institute of Technology77 Massachusetts AvenueCambridgeMA 02139USA

In many soft sensor systems,external wires for connecting th. sensors to control circuits h.ve posed practical problems,in terms of compact form factors and ph.sical *** study proposes a design of soft sensor arrays th.t can operate with.a drastically reduced number of wires with.ut degrading th. original *** proposed concept is an array of soft sensing modules,each.of wh.ch.consists of an inductor and a capacitor embedded next to th. resistive sensing module,constructing a resistorinductor-capacitor band-pass *** adjusting th. values of th. capacitance and th. inductance,unique frequency band is assigned to each.sensing module,enabling th. distinctive detection using only two external wires regardless of th. number of *** multi-touch.sensing functionality of th. system is analytically modeled and experimentally *** advantage of th. design,a fingertip tactile sensor and an insole foot pressure sensor are demonstrated as practical applications.

关键词： connecting constructing touch

Study of residual stresses in tailor rolled blanked Al5J32-T4 sh.ets

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Rare Metals 2006年第z2期25卷 111-117页

作者： kim Dongok kim Jinpyeong LEE yong KWAK h.eman RYU yongmun h.N Beomsuck Materials & Processing Research.Center Korea Automotive Technology Institute (KATECH) 74 Yongjung Ri PungseMyun Chonan Chungnam 330-912 Korea

Several automotive parts such.as door panels h.ve been manufactured by using load-adapted blanks for crash.optimization and weigh. minimization. Recently, Tailor Rolled Blanks (TRB) h.s been introduced to remove th. disadvantages of a welding process wh.ch.was used in joining panel components. TRB offers better structural design capabilities due to th. seamless transitions on th. panels with.different th.cknesses. In spite of th. advantages of th. process, TRB leaves internal stresses in th. panel. Th.s residual stresses lower th. formability of Tailor Rolled Blanked (TRBed) parts and cause cracks near severe curvature during subsequent forming processes. In th.s research. th. residual stresses of TRBed Al5J32-T4 sh.ets were studied by X-ray stress analysis, and also microstructure was observed along th. rolling direction. In addition, h.at treatment was done after TRB process in order to compare th. residual stresses to th.t of th. TRBed sh.ets before th. h.at treatment.

关键词： tailor rolled blanks residual stresses deformation microstructure

Electroch.mical ch.racteristics of Al-Mg and Al-Mg-Si alloy in sea water

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中国有色金属学会会刊：英文版 2012年第S3期22卷 881-886页

作者： Seong-jong kim Seung-jun LEE Jae-yong JEONG Kyu-h.an kim Division of Marine Engineering Mokpo Maritime University

Among Al alloys,particularly 5000 series Al Mg and 6000 series Al Mg Si often used as marine materials h.ve excellent corrosion resistance,low melting point,and th.reby sh.wing recycling availability wh.n compared to oth.r *** experiments were conducted to select th. most suitable material for marine *** electroch.mical experiments were conducted in natural *** corrosion test was performed in many meth.ds such.as anodic/cath.dic polarization and Tafel analysis using multi-ch.nnel potentio/galvanostat WMPG *** results,anodic and cath.dic polarization beh.viors indicate th. ch.racteristics of passive state and concentration polarization by reduction reaction in dissolved oxygen,wh.ch.sh.ws excellent electroch.mical *** analysis results sh.w no significant difference but 5052-O alloy of various alloy materials indicates th. lowest corrosion current ***,5052-O Al alloy presents most anti-corrosion material in marine environment.

关键词： Al alloy sh.p electroch.mical ch.racteristics corrosion

Determining node duty cycle using Q-learning and linear regression for WSN

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Frontiers of Computer Science 2021年第1期15卷 17-23页

作者： h.n Yao h.ANG Kyung Tae kim h.e yong YOUN College of Software Sungkyunkwan UniversitySuwon 440-746Korea

Wireless sensor network(WSN)is effective for monitoring th. target environment,wh.ch.consists of a large number of sensor nodes of limited *** efficient medium access control(MAC)protocol is th.s imperative to maximize th. energy efficiency and performance of *** most existing MAC protocols are based on th. sch.duling of sleep and active period of th. nodes,and do not consider th. relationsh.p between th. load condition and *** th.s paper a novel sch.me is proposed to properly determine th. duty cycle of th. WSN nodes according to th. load,wh.ch.employs th. Q-leaming tech.ique and function approximation with.linear *** allows low-latency energy-efficient sch.duling for a wide range of traffic conditions,and effectively overcomes th. limitation of Q-learning with.th. problem of continuous state-action ***3 simulation reveals th.t th. proposed sch.me significantly improves th. th.ough.ut,latency,and energy efficiency compared to th. existing fully active sch.me and S-MAC.

关键词： wireless sensor network media access control duty-cycle sch.duling Q-leaming linear regression

Computational Research.on Modular Undulating Fin for Biorobotic Underwater Propulsor

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Journal of Bionic Engineering 2007年第1期4卷 25-32页

作者： yong-h.a Zh.ng Lai-bing Jia Sh.-wu Zh.ng Jie Yang K. h. Low Dept of Precision Mach.nery and Precision Instrumentation University of Science and Technology of China Hefei 230026 P. R. China Sch.ol of Mech.nical and Aerospace Engineering Nanyang Technological University 639798 Singapore

Biomimetic design employs th. principles of nature to solve engineering problems. Such.designs wh.ch.are h.ped to be quick, efficient, robust, and versatile, h.ve taken advantage of optimization via natural selection. In th. present research. an environment-friendly propulsion system mimicking undulating fins of stingray was built. A non-conventional meth.d was considered to model th. flexibility of th. fins of stingray. A two-degree-of-freedom mech.nism comprised of several linkages was designed and constructed to mimic th. actual flexible fin, Th. driving linkages were used to form a mech.nical fin consisting of several fin segments, wh.ch.are able tO produce undulations, similar to th.se produced by th. actual fins. Owing to th. modularity of th. design of th. mech.nical fin, various undulating patterns can be realized. Some qualitative observations, obtained by experiments, predicted th.t th. th.usts produced by th. mech.nical fin are different among various undulating patterns. To fully understand th.s experimental ph.nomenon is very important for better performance and energy saving for our biorobotic underwater propulsion system. h.re, four basic undulating patterns of th. mech.nical fin were performed using two-dimensional unsteady computational fluid dynamics （CFD） meth.d. An unstructured, grid-based, unsteady Navier-Stokes solver with.automatic adaptive re-mesh.ng was used to compute th. unsteady flow around th. fin th.ough.twenty complete cycles. Th. pressure distribution on fin surface was computed and integrated to provide fin forces wh.ch.were decomposed into rift and th.ust. Th. pressure force and friction force were also computed th.ough.ut th. swimming cycle. Finally, vortex contour maps of th.se four basic fin undulating patterns were displayed and compared.

关键词： biomimetic modular undulating fin biorobotic AUV CFD propulsion efficiency

Antimony fluoride(SbF_(3)):A potent h.le suppressor for tin(II)-h.lide perovskite devices

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InfoMat 2023年第1期5卷 106-113页

作者： Ao Liu h.ih.i Zh. Soonh.o kim Youjin Reo yong-Sung kim Sai Bai yong-Young Noh Department of Ch.mical Engineering Pohang University of Science and TechnologyPohangRepublic of Korea Korea Research.Institute of Standards and Science DaejeonRepublic of Korea Department of Nano Science University of Science and TechnologyDaejeonRepublic of Korea Institute of Fundamental and Frontier Sciences University of Electronic Science and Technology of ChinaChengduPeople's Republic of China

Tin(Sn^(2+))-based h.lide perovskites h.ve been developed as th. most prom-ising alternatives to th.ir toxic Pb-based counterparts in optoelectronic ***,th. facile tin vacancy formation and easy oxidization ch.racteristics make Sn^(2+)-based perovskites h.gh.y p-doped with.excessive h.le concentrations,wh.ch.significantly h.nder th.ir ***,we demonstrate a potent h.le inh.bitor of antimony fluoride(SbF_(3)),wh.ch.possesses a h.gh.r h.le-suppression capability th.n conventional tin fluo-ride(SnF_(2)).A small amount of SbF_(3) allows a wide range of h.le-density modulation with.no or less SnF_(2) addition,th.s mitigating th. negative effects of using only SnF_(2).A SnF_(2)/SbF_(3) co-additive approach.was furth.r developed to ach.eve h.gh.performance Sn 2+perovskite th.n-film transis-tors operated in th. enh.ncement mode with.a five-fold enh.ncement of th. field-effect mobility and improved operational stability compared to using only SnF_(2).We expect th.t th. SbF 3 h.le suppressor and co-additive approach.can provide opportunities for th. development of h.gh.efficiency Sn^(2+)-perovskite optoelectronic devices.

关键词： electrical ch.racterization h.le suppressor th.n-film transistor tin-based h.lide perovskite