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Microstructure and texture evolution of Ti-Nb-Si based alloys for biomedical applications

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Rare Metals 2006年第z2期25卷 163-167页

作者： kim Won-Yong kim Han-Sol Advanced Materials R&D Division Korea Institute of Industrial Technology Incheon 406-130 Korea

Microstructure and texture of Ti-Nb-Si based alloys, prepared by water quenching from β-phase field, cold rolling and recrystallization heat treatment followed by water quenching, were investigated in terms of optical microstructure and analysis of X-ray pole figure result. In as-quenched sample, relatively random distribution of pole figure was detected without showing a specific texture component. In as-cold rolled sample, however, it is found well-developed several texture components consisting of rotated cube, α-fiber and γ-fiber texture components which are frequently observed in bcc-structured metals and alloys were found. Therefore, texture components developed in the present alloys are closely related to the deformation of β-phase even though small amount of α″ phase co-exist in the microstructure. In recrystallized sample, α-fiber texture component is weakly detected while the other texture components, rotated cube and γ-fiber components, appears to be relatively unchanged. No additional texture components were detected besides those texture components observed in the cold rolled samples.

关键词： Ti-Nb-Si based alloys microstructure texture

3D designed battery-free wireless origami pressure sensor

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Microsystems & Nanoengineering 2022年第6期8卷 35-46页

作者： Taeil kim Amirhossein Hassanpoor Kalhori Tae-Ho kim Chao Bao Woo Soo kim Additive Manufacturing Laboratory School of Mechatronic Systems EngineeringSimon Fraser UniversitySurrey V3T 0A3 BCCanada

A pressure monitoring structure is a very useful element for a wearable device for health monitoring and sports *** pressure sensors have been studied extensively,battery-free functions working in wireless detection have not been studied ***,we report a 3D-structured origami-based architecture sensor for wireless pressure *** developed an architectured platform for wireless pressure sensing through inductorcapacitor(LC)sensors and a monopole antenna.A personalized smart insole with Miura-ori origami designs has been 3D printed together with conductive 3D printed sensors *** monitoring of resonant frequency and intensity changes of LC sensors have been demonstrated to monitor foot pressure for different *** sensitivity of the wireless pressure sensor is tunable from 15.7 to 2.1 MHz/kPa in the pressure ranges from 0 to 9 kPa and from 10 to 40 kPa,*** proposed wireless pressure-sensing platform can be utilized for various applications such as orthotics,prosthetics,and sports gear.

关键词： battery free utilized

The Role of Relative Spinal Motion during Feline Galloping for Speed Performance

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Journal of Bionic Engineering 2014年第4期11卷 517-528页

作者： Young Kook kim Jongwon Park Byungho Yoon Kyung-Soo kim Soohyun kim Robotics Program Korea Advanced Institute of Science and Technology (KAIST) Daejeon 305-701 Republic of Korea Department of Mechanical Engineering Korea Advanced Institute of Science and Technology (KAIST) Daejeon 305-701 Republic of Korea

Felines use their spinal column to increase their running speed at rapid locomotion performance. However, its motion profile behavior during fast gait locomotion has little attention. The goal of this study is to examine the relative spinal motion profile during two different galloping gait speeds. To understand this dynamic behavior trend, a dynamic motion of the feline animal （Felis catus domestica） was measured and analyzed by motion capture devices. Based on the experiments at two different galloping gaits, we observed a significant increase in speed （from 3.2 m.s-1 to 4.33 m.s-1） during the relative motion profile synchronization between the spinal （range： 118.86~ to 168.00~） and pelvic segments （range： 46.35~ to 91.13~） during the hindlimb stance phase （time interval： 0.495 s to 0.600 s）. Based on this discovery, the relative angular speed profile was applied to understand the possibility that the role of the relative motion match during high speed locomotion generates bigger ground reaction force.

关键词： feline galloping galloping gait pattern relative spinal motion speed performance phase match

Development of RuS_(2) for near-infrared photodetector by atomic layer deposition and post-sulfurization

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Rare Metals 2022年第9期41卷 3086-3099页

作者： Tatsuya Nakazawa Donghyun kim Jaehyeok kim Yohei Kotsugi Taehoon Cheon Seung-Min Chung Soo-Hyun kim Hyungjun kim School of Electrical and Electronic Engineering Yonsei UniversitySeoul03722Korea Isehara Technical Center Metallic Materials Development DepartmentTANAKA Kikinzoku Kogyo K.KIseharaKanagawa259-1146Japan Institute of Materials Technology Yeungnam UniversityGyeongsan-si38541GyeongbukKorea Chemical Materials Development Department TANAKA Kikinzoku Kogyo K.KTsukuba Technical CenterIbaraki300-4247Japan School of Materials Science and Engineering Yeungnam UniversityGyeongsan-si38541GyeongbukKorea Center for Core Research Facilities Daegu Gyeongbuk Institute of Science&TechnologyDaegu711-873Korea

The chalcogenides of platinum-group metals(PGMs)have been known to be present in minerals and the intermediate products of *** recent years,their applications in various fields,including catalysis,have been *** that certain PGM chalcogenides behave as compound semiconductors,they can be used as materials for *** this study,RuS_(2),featuring a bandgap suitable for near-infrared photodetectors,was prepared by forming Ru on a SiO_(2)/Si substrate via the atomic layer deposition method using[Ru(TMM)(CO)_(3)]as the *** was conducted at 800℃ for 1 h under H_(2)S ***-resolution transmission electron microscopy(HRTEM)and X-ray diffraction(XRD)analysis clearly confirmed that the as-deposited hexagonal close-packed(hcp)Ru transformed to cubic RuS_(2) after *** surface morphologies,chemical states,and electrical and optical properties of RuS_(2) were *** influence of the metallic Ru surface morphology prior to sulfurization on the reaction between Ru and H_(2)S was also *** evaluate the potential of using RuS_(2) as a photodetector,a photodetector was fabricated by forming electrodes on RuS_(2) to measure its photocurrent under near-infrared ***,RuS_(2) was proven to exhibit a short response time(59μs)and generate a photocurrent of 84 nA under near-infrared light at 940 nm.

关键词： RuS_(2) Sulfurization Atomic layer deposition Photodetector

A systematic correlation between morphology of porous carbon cathode and electrolyte in lithium-sulfur battery

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Journal of Energy Chemistry 2021年第10期30卷 561-573,I0014页

作者： Jihyeon Park Seoyoung Yoon Seoyeah Oh Jiyoon kim Dongjun kim Geonho kim Jiyeon Lee Myeong Jun Song Ilto kim Kwonnam Sohn Jiwon kim School of Integrated Technology College of EngineeringYonsei University85 Songdogwahak-roYeonsu-guIncheon 21983Republic of Korea Integrated Science and Engineering Division Underwood International CollegeYonsei University85 Songdogwahak-roYeonsu-guIncheon 21983Republic of Korea Integrated Biotechnology and Translational Medicine Graduate SchoolYonsei University85 Songdogwahak-roYeonsu-guIncheon 21983Republic of Korea LG Chem. LG Science Park30 Magokjungang 10-roGangseo-guSeoul 07796Republic of Korea

Porous carbon has been applied for lithium-sulfur battery cathodes,and carbonized metal-organic framework(MOF)is advantageous in tuning the ***,we have systematically synthesized water-distorted MOF(WDM)derived porous carbon via controlling the proportion of both water in a mixed solvent(dimethylformamide and water)and ligand in MOF-5 precursors(metal and ligand),which is categorized by its morphology(*** stone(closed),Tassel(open)and Intermediate(semi-open)).For example,decrease in water and increase in ligand content induce Cracked stone WDMs which showed the highest specific surface area(2742-2990 m^(2)/g)and pore volume(2.81-3.28 cm^(3)/g)after *** effect of carbonized WDMs(CWDMs)on battery performance was examined by introducing electrolytes with different sulfur reduction mechanisms(***/DME and ACN_(2) LiTFSITTE):Closed framework effectively confines polysulfide,whereas open framework enhances electrolyte *** initial capacities of the batteries were in the following order:Cracked stone>Intermediate>Tassel for DOL/DME and Intermediate>Tassel>Cracked stone for ACN_(2) *** note,Intermediate CWDM exhibited the highest initial capacity and retained capacity after 100 cycles(1398 and 747 mAh/g)in ACN_(2) LiTFSI-TTE electrolyte having advantages from both open and closed *** sum,we could correlate cathode morphology(openness and pore structure)and electrolyte type(*** solubility)with lithium-sulfur battery performance.

关键词： Lithium-sulfur battery Metal-organic framework Hierarchical porous carbon cathode Morphology control Electrolyte Lithium polysulfide solubility

N-doped carbon-embedded TiN nanowires as a multifunctional separator for Li–S batteries with enhanced rate capability and cycle stability

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Journal of Energy Chemistry 2021年第6期30卷 10-18,I0001页

作者： Yoongon kim Yuseong Noh Jaejin Bae Hyunwoo Ahn Minho kim Won Bae kim Department of Chemical Engineering Pohang University of Science and Technology(POSTECH)77 Cheongam-roNam-guPohang 37673South Korea

Lithium-sulfur(Li-S)batteries have attracted considerable attention as next-generation energy storage devices owing to their high theoretical specific capacity and ***,the commercialization of Li-S batteries is hindered by critical issues,including the migration of the dissolved lithium polysulfides(LiPSs)from the sulfur electrode to the lithium metal anode,resulting in poor cycling ***,we report a multifunctional interlayer configured with an N-doped carbon framework and titanium nitride nanowires on a polypropylene separator(NC/TiN NWs@PP)to suppress the polysulfide shuttling ***/TiN NWs@PP can be obtained by electrospinning and the subsequent scalable solution-based vacuum *** one-dimensional structure of the TiN NWs can shorten the Li-ion diffusion distance with large electrode/electrolyte ***,the N-doped carbon framework in the NWs enables facile electron transportation and allows the suppression of the shuttle effect to improve the electrochemical reaction *** Li-S battery with a NC/TiN NWs@PP separator exhibited enhanced cycling stability and rate capability,indicating that this could be a new research direction for Li-S batteries.

关键词： Li-S battery Shuttle effect Interlayer Separator TiN N-doped carbon 1D Nanowire

A Novel Transparent and Auditable Fog-Assisted Cloud Storage with Compensation Mechanism

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Tsinghua Science and Technology 2020年第1期25卷 28-43页

作者： Donghyun kim Junggab Son Daehee Seo Yeojin kim Hyobin kim Jung Taek Seo Department of Computer Science Kennesaw State UniversityMariettaGA 30060USA Department of Information Security Engineering Soonchunhyang UniversityAsan 31538South Korea

This paper introduces a new fog-assisted cloud storage which can achieve much higher throughput compared to the traditional cloud-only storage architecture by reducing the traffics toward the cloud storage. The fog-storage service providers are transparency to end-users and therefore, no modification on the end-user devices is necessary. This new system is featured with(1) a stronger audit scheme which is naturally coupled with the proposed architecture and does not suffer from the replay attack and(2) a transparent and efficient compensation mechanism for the fog-storage service providers. We provide rigorous theoretical analysis on the correctness and soundness of the proposed system. To the best of our knowledge, this is the first paper to discuss about a storage data audit scheme for fog-assisted cloud storage as well as the compensation mechanism for the service providers of the fog-storage service providers.

关键词： fog computing cloud computing network storage data audit merkle hash tree integer factorization payment transparency

DYNAMIC PROPERTIES OF AL-ALLOY FOAM BEAM DAMAGED BY COMPRESSIVE FATIGUE

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Acta Mechanica Solida Sinica 2008年第3期21卷 241-246页

作者： Sung-Gaun kim Ilhyun kim Amkee kim Seung-Joon kim Junhong Park Division of Mechanical and Automotive Engineering Kongju National University 275 Budae-dongCheonan Chungnam 330-717 Korea Department of Mechanical Engineering Hanyang University Seongdong-Gu Seoul 133-791 Korea

The permanent residual strain in aluminum （Al） alloy foams induced by compressive fatigue gradually increases with the increasing number of loading cycles. Consequently, the progressive shortening of Al-alloy foam degrades the dynamic material performance by the failure and ratcheting of multi-cells in the foam. In this paper, the dynamic properties of Al-alloy foams damaged by compressive fatigue were studied. The beam specimens with various residual strains were made by cyclic compression-compression stress. The dynamic bending modulus and loss factor were evaluated by using a beam transfer function method. As a result, the dynamic bending stiffness of Al-alloy foam turned out to be decreased due to damage while the loss factor was improved because of the increasing energy dissipation of such factors as cracked cell walls formed during the shortening process of the foam. The loss factor shows a manifest dependence on the fatigue residual strain.

关键词： Aluminum foam fatigue dynamic stiffness loss factor

Some identities of Bell polynomials

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Science China Mathematics 2015年第10期58卷 2095-2104页

作者： kim Dae San kim Taekyun Department of Mathematics Sogang University Department of Mathematics Kwangwoon University

We investigate Bell polynomials, also called Touchard polynomials or exponential polynomials, by using and without using umbral calculus. We use three different formulas in order to express various known families of polynomials such as Bernoulli polynomials, poly-Bernoulli polynomials, Cauchy polynomials and falling factorials in terms of Bell polynomials and vice versa. In addition, we derive several properties of Bell polynomials along the way.

关键词： Bell-polynomial umbral calculus poly-Bernoulli polynomial higher-order Bernoulli polynomial Cauchy polynomial