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Formation of interfacial brittle phases sigma phase and IMC in hybrid titanium-to-stainless steel joint

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Transactions of Nonferrous Metals Society of China 2011年第A1期21卷 7-11页

作者： Min Ku lee jung gu lee Jong Keuk lee Sung Mo HONG Sang Hoon lee Jin Ju PARK Jae Woo KIM Chang Kyu RHEE Nuclear Materials Research Division Korea Atomic Energy Research Institute Daejeon 305-353 Korea

The microstructures of the brazed joints for commercially pure Ti and stainless steel were investigated by the applications of various filler alloys including Ag-, Ti-, Zr- and Ni-based alloys. Generally, the dissimilar joints between Ti and stainless steel were dominated by the Ti-based intermetallic compounds （IMCs）, e.g. （Ti, Zr）2（Fe, Ni）, TiFe, TiCu, and Ti2（Fe, Ni）, due to a significant dissolution of Ti from the base metal. The （Fe-Cr） cr phase was also observed near the stainless steel due to a segregation of Cr into the interface region. This research demonstrates empirically that the brittleness of the Ti and stainless steel joint can not be avoided only by applying single braze alloy or single insert metal, and thus an introduction of additional suitable interlayer between the filler alloy and the base metal is necessary to prevent the brittleness of the joint.

关键词： brazing titanium stainless steel intermetallic compounds (IMCs)

Fabrication of high-strength duplex nanoporous Cu by dealloying a dual-phase Mg-Cu precursor alloy

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Journal of Magnesium and Alloys 2020年第3期8卷 910-916页

作者： Si-Young lee Soo-Min Baek Eun-Ji Gwak Na-Ri Kang Ju-Young Kim Su-Hyeon Kim jung gu lee Sung Soo Park School of Materials Science and Engineering Ulsan National Institute of Science and TechnologyUlsan 44919Republic of Korea Korea Institute of Materials Science Changwon 51508Republic of Korea School of Materials Science and Engineering University of UlsanUlsan 44610Republic of Korea

Duplex nanoporous Cu was successfully fabricated by dealloying a dual-phase Mg-Cu precursor alloy consisting of intermetallic Mg2Cu and *** duplex nanoporous Cu with embedded nanoporous struts exhibited highly enhanced strength compared to the typical monolithic nanoporous Cu under both compressive and flexural test conditions at room temperature;the duplex np-Cu sample exhibited a 12 times higher compressive strength and a 40 times greater flexural strength than the monolithic np-Cu *** responsible for the strength enhancement in the duplex nanoporous Cu are discussed.

关键词： Mg-Cu alloy Nanoporous Cu Dealloying Duplex structure Strength

An Effective Threat Detection Framework for Advanced Persistent Cyberattacks

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Computers, Materials & Continua 2023年第5期75卷 4231-4253页

作者： So-Eun Jeon Sun-Jin lee Eun-Young lee Yeon-Ji lee jung-Hwa Ryu jung-Hyun Moon Sun-Min Yi Il-gu lee Department of Future Convergence Technology Engineering Sungshin Women’s UniversitySeoul02844Korea Department of Convergence Security Engineering Sungshin Women’s UniversitySeoul02844Korea

Recently,with the normalization of non-face-to-face online environments in response to the COVID-19 pandemic,the possibility of cyberattacks through endpoints has *** endpoint devices are managed meticulously to prevent cyberattacks and ensure timely responses to potential security *** particular,because telecommuting,telemedicine,and teleeducation are implemented in uncontrolled environments,attackers typically target vulnerable endpoints to acquire administrator rights or steal authentication information,and reports of endpoint attacks have been increasing *** persistent threats(APTs)using various novel variant malicious codes are a form of a sophisticated ***,conventional commercial antivirus and anti-malware systems that use signature-based attack detectionmethods cannot satisfactorily respond to such *** this paper,we propose a method that expands the detection coverage inAPT attack *** this model,an open-source threat detector and log collector are used synergistically to improve threat detection *** the scope of attack log collection through interworking between highly accessible open-source tools can efficiently increase the detection coverage of tactics and techniques used to deal with APT attacks,as defined by MITRE Adversarial Tactics,Techniques,and Common Knowledge(ATT&CK).We implemented an attack environment using an APT attack scenario emulator called Carbanak and analyzed the detection coverage of Google Rapid Response(GRR),an open-source threat detection tool,and Graylog,an open-source log *** proposed method expanded the detection coverage against MITRE ATT&CK by approximately 11%compared with that conventional methods.

关键词： Advanced persistent threat cybersecurity endpoint security MITRE ATT&CK open-source threat detector threat log collector

Next High Performance and Low Power Flash Memory Package Structure

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Journal of Computer Science & Technology 2007年第4期22卷 515-520页

作者： jung-Hoon lee ERI Control Instrumentation EngineeringGyeongSang National UniversityJinju660-701Korea

In general, NAND flash memory has advantages in low power consumption, storage capacity, and fast erase/write performance in contrast to NOR flash. But, main drawback of the NAND flash memory is the slow access time for random read operations. Therefore, we proposed the new NAND flash memory package for overcoming this major drawback. We present a high performance and low power NAND flash memory system with a dual cache memory. The proposed NAND flash package consists of two parts, i.e., an NAND flash memory module, and a dual cache module. The new NAND flash memory system can achieve dramatically higher performance and lower power consumption compared with any conventionM NAND-type flash memory module. Our results show that the proposed system can reduce about 78% of write operations into the flash memory cell and about 70% of read operations from the flash memory cell by using only additional 3KB cache space. This value represents high potential to achieve low power consumption and high performance gain.

关键词： flash memory NAND-type NOR-type memory localities buffer or cache memory

Aligned Ion Conduction Pathway of Polyrotaxane‑Based Electrolyte with Dispersed Hydrophobic Chains for Solid‑State Lithium–Oxygen Batteries

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Nano-Micro Letters 2025年第2期17卷 169-186页

作者： Bitgaram Kim Myeong‑Chang Sung Gwang‑Hee lee Byoungjoon Hwang Sojung Seo Ji‑Hun Seo Dong‑Wan Kim Department of Materials Science and Engineering Korea University145 Anam‑RoSeongbuk‑GuSeoul 02841Republic of Korea School of Civil Environmental and Architectural EngineeringKorea University145 Anam‑RoSeongbuk‑GuSeoul 02841Republic of Korea Materials Science and Chemical Engineering Center Institute for Advanced Engineering(IAE)Yongin 17180Republic of Korea

A critical challenge hindering the practical application of lithium–oxygen batteries(LOBs)is the inevitable problems associated with liquid electrolytes,such as evaporation and safety *** study addresses these problems by proposing a modified polyrotaxane(mPR)-based solid polymer electrolyte(SPE)design that simultaneously mitigates solvent-related problems and improves ***-SPE exhibits high ion conductivity(2.8×10^(−3)S cm^(−1)at 25℃)through aligned ion conduction pathways and provides electrode protection ability through hydrophobic chain *** this mPR-SPE into solid-state LOBs resulted in stable potentials over 300 *** situ Raman spectroscopy reveals the presence of an LiO_(2)intermediate alongside Li_(2)O_(2)during oxygen *** situ X-ray diffraction confirm the ability of the SPE to hinder the permeation of oxygen and moisture,as demonstrated by the air permeability *** present study suggests that maintaining a low residual solvent while achieving high ionic conductivity is crucial for restricting the sub-reactions of solid-state LOBs.

关键词： Solid polymer electrolyte Lithium-oxygen batteries Polyrotaxane ion conductivity Hydrophobic chain

Topic Modeling Based Warning Prioritization from Change Sets of Software Repository

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Journal of Computer Science & Technology 2020年第6期35卷 1461-1479页

作者： jung-Been lee Taek lee Hoh Peter In College of Informatics Korea UniversitySeoul 02841Korea College of Knowledge-Based Services Engineering Sungshin UniversitySeoul 02844Korea

Many existing warning prioritization techniques seek to reorder the static analysis warnings such that true positives are provided first. However, excessive amount of time is required therein to investigate and fix prioritized warnings because some are not actually true positives or are irrelevant to the code context and topic. In this paper, we propose a warning prioritization technique that reflects various latent topics from bug-related code blocks. Our main aim is to build a prioritization model that comprises separate warning priorities depending on the topic of the change sets to identify the number of true positive warnings. For the performance evaluation of the proposed model, we employ a performance metric called warning detection rate, widely used in many warning prioritization studies, and compare the proposed model with other competitive techniques. Additionally, the effectiveness of our model is verified via the application of our technique to eight industrial projects of a real global company.

关键词： automated static analysis topic modeling warning prioritization

Nonlinear Electrical Impedance Tomography Method Using a Complete Electrode Model for the Characterization of Heterogeneous Domains

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Computer Modeling in Engineering & Sciences 2023年第3期134卷 1707-1735页

作者： Jeongwoo Park Bong-gu jung Jun Won Kang Department of Civil and Environmental Engineering Hongik UniversitySeoul04066Korea

This paper presents an electrical impedance tomography(EIT)method using a partial-differential-equationconstrained optimization *** forward problem in the inversion framework is described by a complete electrodemodel(CEM),which seeks the electric potential within the domain and at surface electrodes considering the contact impedance between *** finite element solution of the electric potential has been validated using a commercial *** inverse medium problem for reconstructing the unknown electrical conductivity profile is formulated as an optimization problem constrained by the *** method seeks the optimal solution of the domain’s electrical conductivity to minimize a Lagrangian functional consisting of a least-squares objective functional and a regularization *** the stationarity of the Lagrangian leads to state,adjoint,and control problems,which constitute the Karush-Kuhn-Tucker(KKT)first-order optimality ***,the electrical conductivity profile of the domain is iteratively updated by solving the KKT conditions in the reduced space of the control *** results show that the relative error of the measured and calculated electric potentials after the inversion is less than 1%,demonstrating the successful reconstruction of heterogeneous electrical conductivity profiles using the proposed EIT *** method thus represents an application framework for nondestructive evaluation of structures and geotechnical site characterization.

关键词： Electrical impedance tomography complete electrode model inverse medium problem Karush-Kuhn-Tucker(KKT)optimality conditions nondestructive evaluation of structures

Determination of diffusion coefficient by image-based fluorescence recovery after photobleaching and single particle tracking system implemented in a single platform

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Journal of Innovative Optical Health Sciences 2021年第2期4卷 93-101页

作者： Donghee lee Jeonghoon lee jung Kyung Kim Department of Genetics Cell Biology and Anatomy University of Nebraska Medical CenterOmahaNE 68198USA School of Mechanical Engineering KOREA TECH Cheonan 31253Republic of Korea School of Mechanical Engineering and Department of Integrative Biomedical Science and Engineering Graduate School Kookmin University Seoul 02707Republic of Korea

Fluorescence recovery after photobleaching(FRAP)and single particle tracking(SPT)techni-ques determine the diffusion coefficient from average diffusive motion of high-concentration molecules and from trajectories of low-concentration single molecules,*** dif-fusion coefficients measured by FRAP and SPT techniques for the same biomolecule on cell membrane have exhibited inconsistent values across laboratories and platforms with larger dif-fusion coefficient determined by FRAP,but the sources of the inconsistency have not been investigated ***,we designed an image-based FRAP-SPT system and made a direct comparison between FRAP and SPT for diffusion coefficient of submicron particles with known theoretical values derived from Stokes-Einstein equation in aqueous *** combined iFRAP-SPT technique allowed us to measure the diffusion coefficient of the same fluorescent particle by utilizing both techniques in a single platform and to scrutinize inherent errors and artifacts of *** results reveal that diffusion coefficient overestimated by FRAP is caused by inaccurate estimation of the bleaching spot size and can be corrected by simple image *** iFRAP-SPT technique can be potentially used for not only cellular membrane dynamics but also for quantitative analysis of the spatiotemporal distribution of the solutes in small scale analytical devices.

关键词： Diffusion coefficient fluorescence recovery after photobleaching(FRAP) single particle tracking(SPT)

Generation of acoustic waves in the hypersonic boundary layer over a wavy wall

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Science China(Physics,Mechanics & Astronomy) 2022年第3期65卷 62-70页

作者： WenKai Zhu DingWei gu YiDing Zhu CunBiao lee State KeyLaboratory of Turbulence and Complex Systems Collaborative Innovation Center of Advanced Aero-EnginePeking UniversityBeijing 100871China

The effects of a wavy wall on a hypersonic boundary layer of a flared cone are investigated using experimental measurements and direct numerical simulations(DNSs). Non-contact optical measurements using a focused laser differential interferometer(FLDI) show that a wavy wall can significantly suppress the second mode, and multiple perturbations of new frequencies are generated over the wavy surface, which agrees well with numerical results. Using Lagrangian tracking of marked particles, it is demonstrated that the wavy wall geometry can induce mean flow oscillations while exciting acoustic waves. The frequencies of the excited disturbances over a wavy wall agree with the classical Rossiter model. The superposition of a disturbance propagating downstream and an acoustic wave propagating upstream at the same frequency but with different amplitudes and propagation velocities results in a spatial distribution with a streamwise-oscillatory pattern over the wavy surface. A simple two-wave superposition model that takes into account the phase velocities and wavenumbers of the convective disturbance and acoustic wave can well describe the modal behavior of excited disturbances over a wavy wall.

关键词： instability of boundary layers compressible flows hypersonic flows

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