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Analysis of optical emission spectroscopy data during silicon etching in SF_(6)/O_(2)/Ar plasma

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Plasma Science and Technology 2021年第12期23卷 117-127页

作者： dong hwan kim Jeong Eun CHOI Sang Jeen HONG Department of Electronics Engineering Myongji University116 Myongji-roYongin-siGyeonggi-doRepublic of Korea

Silicon etching is an essential process in various applications,and a major challenge for etching process is anisotropic high aspect ratio etching *** etch profile is determined by the plasma parameters and process *** this study,the plasma state with each process parameters were analyzed through the optical emission spectroscopy(OES)plasma diagnostic sensor by both chemical and physical *** temperature and electron density were additionally acquired using the corona model with OES data that provides chemical species information,and the etch profile was evaluated through scanning electron microscope measurement *** results include changes in profile with gas ratio,bias power,and *** figure out that factors like ion energy and ion angular distribution as well as chemical reaction affect the anisotropic profile.

关键词： silicon etching profile optical emission spectroscopy plasma in-formation corona model

URANS simulations for a free-running container ship:Part 2. Added power

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Journal of Hydrodynamics 2021年第3期33卷 448-467页

作者： dong-hwan kim Yugo Sanada Hamid Sadat-Hosseini Frederick Stern IIHR-Hydroscience and Engineering The University of IowaIowa CityUSA Costal Development and Ocean Energy Research Center Korea Institute of Ocean Science and TechnologyBusanKorea Mechanical Engineering University of North TexasDentonUSA

Part 2 reports the validation,local force and local flow study results for the free-running added power simulations whose conditions are the same as the self-propulsion test except for the increased propeller rotational speed and the presence of *** targeting the same mean Froude number in the wave condition,the propeller requires the increased propeller rotational speed for the operation at the low advance ratio due to the added *** test is performed at five different wavelengths in head waves and four different headings in the oblique *** the validation study,the time series of the validation variables is decomposed with discrete Fourier transform to extract the harmonic *** variables are global parameters,including motions,propeller thrust,and torque coefficients,added power variables,and self-propulsion factors which show reasonable agreement against the experiment results and produces a similar error from the self-propulsion *** local force study shows that the added resistance mostly appears at the bow due to the bow plunging during the short head wave and resonance *** contributions of the gravitational force and the buoyant force are found to increase as the stern motion exceeds the bow motion during the long head wave *** oscillation of the propeller performances shows correlation with the first harmonic amplitude of the propeller ***,pitch,and roll decay tests are performed prior to the main test to assess the natural frequencies of the *** as Part 1,a discretized propeller is used.

关键词： Added power unsteady Reynolds-averaged Navier-Stokes(URANS) KRISO Container Ship(KCS) CFDShip-IOWA

Surface-floating gold nanorod super-aggregates with macroscopic uniformity

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Nano Research 2018年第5期11卷 2379-2391页

作者： Abdul R. Ferhan Youju Huang Anirban Dandapat dong-hwan kim School of Chemical and Biomedical Engineering Nanyang Technological University 62 Nonyang Drive 6374S7 Singapore School of Chemical Engineering Sungkyunkwan University Gyeonggi-do 16419 Republic of Korea

We present a simple method for obtaining high-density two- and three- dimensional assemblies of gold nanorods （AuNRs） on polymer brush, referred to as ＂surface-floating super-aggregates＂, with uniform distribution spanning macroscopic distances. This was achieved via the single-step immersion of a poly（oligo ethylene glycol methacrylate） brush-containing substrate in a AuNR solution without any form of functionalization. Owing to extensive macroscale plasmonic coupling, we observed for the first time the gradual evolution of a unique sharp peak in addition to the transverse and longitudinal peaks, in this case, in the near-infrared （NIR） region. We also highlight the dynamic nature of these surface-floating super-aggregates, in which the AuNRs spread out when immersed in solution and collapse when dried to facilitate the access of probe molecules for biosensing applications. As a proof of concept, the surface-floating super-aggregates were used for surface-enhanced Raman spectroscopy, with which we detected rhodamine 6G at as low as sub-femtomolar concentrations. Owing to the excellent large-area uniform coverage and extreme simplicity of the fabrication method, such AuNR assemblies can easily be mass-produced and incorporated into cheap biosensors suitable for consumer use in the near future.

关键词： nanoparticle polymer brush nanocomposites surface-enhanced Raman spectroscopy (SERS)

URANS simulations for a free-running container ship:Part 1. Turning-circle

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Journal of Hydrodynamics 2021年第3期33卷 421-447页

作者： dong-hwan kim Yugo Sanada Sungtek Park Hamid Sadat-Hosseini Frederick Stern IIHR-Hydroscience and Engineering The University of IowaIowa CityUSA Costal Development and Ocean Energy Research Center Korea Institute of Ocean Science and TechnologyBusanKorea Mechanical Engineering University of North TexasDentonUSA

The incompressible unsteady Reynolds-averaged Navier-Stokes(URANS)simulations are performed for a free-running container ship in maneuvering conditions:the starboard and portside turning circle simulations with 35°rudder *** validation variables include trajectory,motions,and propeller performances,and the prediction shows acceptable agreements against the experimental *** the steady-state part of the turning,the inertial forces balancing the local forces are reported to quantitatively assess the centrifugal force which appears from the force equilibrium between the rudder,propeller,and the *** study on the local flow focuses on finding the correlations between the propeller inflow and the propeller performance to investigate the differences in propeller performances during the portside and starboard *** preliminary simulations,performed with the grid triplet,comprise propeller open-water,resistance,and self-propulsion simulations,from which the validation studies and the studies for the local force and the local flow are fulfilled and applied for the main *** propeller and rudder are fully discretized and controlled,mimicking the ***-set,overset approach and Mentor’s SST model are employed for the free-surface capturing,large motion prediction,and turbulence closure.

关键词： Turning-circle unsteady Reynolds-averaged Navier-Stokes(URANS) KRISO Container Ship(KCS) CFDShip-IOWA

Texture development and grain boundary phase formation in Ce-and Ce-La-substituted Nd-Fe-B magnets during hot-deformation process

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Journal of Materials Science & Technology 2022年第31期126卷 71-79页

作者： Ga-Yeong kim Tae-Hoon kim Hee-Ryoung Cha Sang-hyub Lee dong-hwan kim Yang-Do kim Jung-Goo Lee Department of Magnetic Materials Korea Institute of Materials ScienceChangwon 51508Republic of Korea Department of Materials Science and Engineering Pusan National UniversityBusan 46241Republic of Korea R&D Center Star Group Ind.Co.Ltd.Daegu 42714Republic of Korea

In this study,the influence of Ce-and Ce-La-substitution for Nd in Nd-Fe-B magnets on their magnetic and microstructural changes in the course of the hot-deformation process was investigated to gain insight into further reducing the Nd content in fine-grained Nd-Fe-B hot-deformed *** found that the[001]texture and microstructure of the RE-rich grain boundary phases,which are the factors that de-termine the remanence and coercivity of hot-deformed magnets,were deteriorated by the Ce-and *** is because the volume fraction of the RE-rich liquid formed in the grain boundaries during the hot-press and hot-deformation decreased due to the Ce-and Ce-La-substitution,thereby in-creasing the friction between the 2:14:1 grains while the c-axes of grains were aligned by grain rotation and decreasing the RE concentration of grain boundary *** particular,the Ce-La-co-substitution further prevented the liquid formation within the grain boundaries of the magnets during hot-press and hot-deformation because the wettability of the RE-rich liquid on the 2:14:1 grains became poor when La was substituted for Nd in the 2:14:1 *** results indicate that there is room for further im-provement in both the remanence and coercivity of the Ce-and Ce-La-substituted magnets by intro-ducing additional liquid into the grain boundaries prior to hot-press and *** applying the Nd-Cu infiltration process to the melt-spun ribbons(intermediate infiltration,I-infiltration),both the remanence and coercivity of the Nd-saving(Nd 0.7 Ce 0.3)-Fe-B and(Nd 0.7 Ce 0.225 La 0.075)-Fe-B hot-deformed magnets were successfully improved.

关键词： Nd-Fe-B magnets Hot-deformation Nd-saving Ce-substitution La-substitution Infiltration

Vacuum-free lamination via controlled polymer adhesion for selective photogeneration and photodetection

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Carbon Energy 2024年第7期6卷 205-218页

作者： Min Soo kim Jihyun Lim Woongsik Jang dong hwan Wang Department of Intelligent Semiconductor Engineering Chung-Ang UniversitySeoulRepublic of Korea School of Integrative Engineering Chung-Ang UniversitySeoulRepublic of Korea

This study attempts to develop a reproducible thin-film formation technique called vacuum-free(VF)lamination,which transfers thin films using elastomeric polymer-based laminating ***,by controlling the interface characteristics of the mediator based on the work of adhesion,VF lamination is successfully performed for various thicknesses(from 20 to 240 nm)of a conjugated photoactive material composed of poly[(2,6-(4,8-bis(5-(2-ethylhexyl-3-fluoro)thiophen-2-yl)-benzo[1,2-b:4,5-bʹ]dithiophene))-alt-(5,5-(1ʹ,3ʹ-di-2-thienyl-5ʹ,7ʹ-bis(2-ethylhexyl)benzo[1ʹ,2ʹ-c:4ʹ,5ʹ-cʹ]dithiophene-4,8-dione)](a polymer donor)and 2,2ʹ-((2Z,2ʹZ)-((12,13-bis(2-butyloctyl)-3,9-diundecyl-12,13-dihydro-[1,2,5]thiadiazolo[3,4-e]thieno[2ʹʹ,3ʹʹ:4ʹ,5ʹ]thieno[2ʹ,3ʹ:4,5]pyrrolo[3,2-g]thieno[2ʹ,3ʹ:4,5]thieno[3,2-b]indole-2,10-diyl)bis(methanylylidene))bis(5,6-difluoro-3-oxo-2,3-dihydro-1H-indene-2,1-diylidene))dimalononitrile(a nonfullerene acceptor).Interestingly,the organic photovoltaic and photodetecting applications,prepared by the VF lamination process,showed superior performance compared to those of devices prepared by conventional *** is due to the overturned surface morphology,which led to enhanced charge transport ability and blocking of the externally injected ***,the reproducible VF lamination process,exploiting an adhesion-based elastomeric polymer mediator,is a promising thin-film formation technique for developing efficient next-generation organic optoelectronic materials consistent with the solution process.

关键词： conjugated nonfullerene acceptor photodetectors photovoltaics polymer vacuum-free lamination

Aligning Crystal Orientation of Poly-Crystalline Bi-Te With a High Magnetic Field

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Journal of Iron and Steel Research International 2012年第S2期19卷 1039-1043页

作者： Hoyoung kim dong hwan kim Cham kim Tingju Li DGIST Dalian University of Technology

We investigated the effect of aligning crystal orientation in the microstructures containing sub micro-sized grains on the thermoelectric properties for polycrystalline Bi-Te ***-Te powder,prepared through the conventional pulverization process,was sufficiently dispersed in an appropriate solvent,and then was formed into c-axis aligned green bodies under a designated high magnetic *** green bodies were sintered with spark-plasma-sintering *** degree of crystal alignment of sintered bodies was examined with the electron-back-scatter-diffraction SEM and the X-ray diffraction *** was observed that for both p and n type thermoelectric Bi-Te materials,aligning crystal orientation properly made electrical resistivity decreased with keeping Seebeck coefficient and thermal conductivity remained *** a typical result,the aligned Bi-Te material with the magnetic field of 10 tesla showed 30%enhancement of the thermoelectric performance.

关键词： thermoelectric Bi-Te crystal orientation alignment high magnetic field

Microstructural evolution in lithium plating process and its effect on the calendar storage life

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Nano Research 2024年第10期17卷 8834-8841页

作者： Ki hwan Koh dong Ju Lee Anthony Mu Kangwoon kim Taehee kim Zheng Chen Department of Chemical and Nano Engineering University of California San DiegoLa JollaCA 92093USA Program of Materials Science and Engineering University of California San DiegoLa JollaCA 92093USA Sustainable Power and Energy Center University of California San DiegoLa JollaCA 92093USA

The growing demand for electric vehicles highlights the need for energy storage solutions with higher densities,spotlighting Li metal anodes as potential successors to traditional Li-ion batteries(LIBs).Achieving longer calendar aging life for Li metal anodes is crucial for their practical use,given their propensity for corrosion due to a low redox potential,which leads to compromised cycling stability and significant capacity loss during *** research investigated that this susceptibility is mainly dependent on the surface area of Li metal anode and the properties of the solid electrolyte interphase(SEI),particularly its stability and growth *** research adds to this understanding by demonstrating that the amount of Li plating is a key factor in its corrosion during open-circuit storage,as assessed across various *** discovered that increasing the Li plating amount effectively reduces Coulombic efficiency(C.E.)loss during aging,due to a lower surface area-to-Li *** implies that the choice of electrolyte for optimal storage life should consider the amount of Li plating,with higher capacities promoting better storage characteristics.

关键词： lithium metal batteries anode-free batteries calendar life of batteries lithium anode corrosion

Electrochemical biosensors for point-of-care testing

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Bio-Design and Manufacturing 2024年第4期7卷 548-565页

作者： Jinsol kim Juho Jeong Seung hwan Ko Department of Mechanical Engineering Seoul National UniversitySeoul 08826Republic of Korea Institute of Advanced Machinery and Design(SNU-IAMD) Seoul National UniversitySeoul 08826Republic of Korea

Point-of-care testing(POCT)is the practice of diagnosing and monitoring diseases where the patient is located,as opposed to traditional treatment conducted solely in a medical laboratory or other clinical *** has been less common in the recent past due to a lack of portable medical devices capable of facilitating effective medical ***,recent growth has occurred in this field due to advances in diagnostic technologies,device miniaturization,and progress in wearable *** these developments,electrochemical sensors have attracted interest in the POCT field due to their high sensitivity,compact size,and *** are used in various applications,from disease diagnosis to health status *** this paper we explore recent advancements in electrochemical sensors,the methods of fabricating them,and the various types of sensing mechanisms that can be ***,we delve into methods for immobilizing specific biorecognition elements,including enzymes,antibodies,and aptamers,onto electrode surfaces and how these sensors are used in real-world POCT settings.

关键词： Point-of-care testing(POCT) Electrochemical sensor Enzyme Antibody Health care