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Mg Alloy Foam Fabrication via Melt Foaming Method

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Journal of Materials Science & Technology 2008年第3期24卷 302-304页

作者： changhwan SEO Bo-Young HUR i-Cube Center ERISchool of Nano & Advanced Materials EngineeringGyeongsang National University

For the first time AZ91 （MgAl9Zn1） and AM60 （MgAl6） Mg alloy foams with homogeneous pore structures were prepared successfully via melt foaming method using CaCO3 as blowing agent. It is revealed that the blowing gas to foam the melt is not CO2 but CO, which comes from liquid-solid reaction between Mg melt. The reaction temperature is more than 100℃ lower than CaCO3 decomposition, which makes Mg alloy melts foam into cellular structure much more easily in the temperature range from 690℃ to 750℃.

关键词： Mg alloy foam CaCO3 Blowing gas

Solid-phase Extraction of β-Sitosterol from Oldenlandia diffusa Using Molecular Imprinting Polymer

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Chinese Journal of Chemistry 2011年第6期29卷 1246-1250页

作者： Zhu, Tao Yoon, changhwan Row, Kyungho Department of Chemical Engineering Inha University 253 Yonghyun-Dong Nam-Ku lncheon 402-751 Korea

The β-sitosterol imprinted polymer was prepared for selective extraction and analysis of β-sitosterol from Old-enlandia diffusa （0. diffusa） followed by HPLC with UV detection. The imprinted polymers show high affinity and selectivity to β-sitosterol. Using this molecularly imprinted polymer （MIP） cartridge as solid-phase extraction （SPE） material, the interferences could be quickly washed out and β-sitosterol was selectively retained and enriched. HPLC analysis method was used to evaluate the characteristics of this MIP material. At the condition of mobile phase composed of MeOH/H20/H3PO4 （99/1/0.1, V/V/V, pH=6.0） and the flow rate of 1.0 mL·min -1, a good linear relationship was demonstrated when the concentrations of β-sitosterol were in the range of 0.50--100.0 μg·mL-1. The recoveries ranged from 75.3% to 86.5% and the inter-day and intra-day relative standard deviations were less than 5%. This developed HPLC method was proved to be acceptable for extraction offl-sitosterol from O. diffusa.

关键词： β-sitosterol cartridge extraction molecular imprinting Oldenlandia diffusa

Optimizing the thickness of Ta_(2)O_(5) interfacial barrier layer to limit the oxidization of Ta ohmic interface and ZrO_(2) switching layer for multilevel data storage

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Journal of Materials Science & Technology 2022年第11期106卷 98-107页

作者： Muhammad Ismail Haider Abbas Chandreswar Mahata changhwan Choi Sungjun Kim Division of Electronics and Electrical Engineering Dongguk UniversitySeoul 04620Republic of Korea Division of Materials Science and Engineering Hanyang UniversitySeoul 04763Republic of Korea

The multilevel storage capability of nonvolatile resistive random access memory(ReRAM)is greatly de-sired to accomplish high functioning memory *** this study,Ta_(2)O_(5) thin film with different thick-nesses(2,4,and 6 nm)was exploited as an appropriate interfacial barrier layer for limiting the formation of the interfacial layer between the 10 nm thick sputtering deposited resistive switching(RS)layer and Ta ohmic electrode to improve the switching cycle endurance and *** show that lower form-ing voltage,narrow distribution of SET-voltages,good dc switching cycles(10^(3)),high pulse endurance(10^(6) cycles),long retention time(10^(4) s at room temperature and 100℃),and reliable multilevel resis-tance states were obtained at an appropriate thickness of∼2 nm Ta_(2)O_(5) interfacial barrier layer instead of without Ta_(2)O_(5) and with∼4 nm,and∼6 nm Ta_(2)O_(5) barrier layer,ZrO_(2)-based memristive ***,multilevel resistance states have been scientifically investigated via modulating the compliance current(CC)and RESET-stop voltages,which displays that all of the resistance states were distinct and stayed stable without any considerable deprivation over 10^(4) s retention time and 104 pulse endurance *** I-V characteristics of RESET-stop voltage(from−1.7 to−2.3 V)of HRS are found to be a good linear fit with the Schottky *** can be seen that Schottky barrier height rises by increasing the stop-voltage during RESET-operation,resulting in enhancing the data storage memory window(on/offratio).Moreover,RESET-voltage and CC control of HRS and LRS revealed the physical origin of the RS mecha-nism,which entails the formation and rupture of conducting *** is thoroughly investigated that proper optimization of the barrier layer at the ohmic interface and the switching layer is essential in memristive *** results demonstrate that the ZrO_(2)-based memristive device with an optimized∼2 nm Ta_(2)O_(5) barrier

关键词： Resistive switching Ta_(2)O_(5)/ZrO_(2)bilayer film Barrier layer thickness Multilevel resistance states RESET-stop voltage

Reconstructing the post-LGM deglacial history of Hollingsworth Glacier on Ricker Hills,Transantarctic Mountains,Antarctica

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Journal of Mountain Science 2022年第5期19卷 1217-1230页

作者： RHEE Hyun-Hee SEONG Yeong-Bae WOO Ju-Sun Oh changhwan YU Byung-Yong Division of Glacial Environment Research Korea Polar Research InstituteIncheon 21990Republic of Korea Department of Geography Education Korea UniversitySeoul 02841Republic of Korea School of Earth and Environmental Sciences Seoul National UniversitySeoul 08826Republic of Korea Department of Earth and Environmental Science Chungbuk National UniversityCheongju 28644Republic of Korea AMS laboratory Korea Institute of Science and TechnologySeoul 02792Republic of Korea

The Transantarctic Mountains are an important corridor between the East Antarctic Ice Sheet and the Western Ross Sea,where most current ice streams and outlet glaciers *** investigated Ricker Hills,the largest exposed mountainous region between Southern Victoria Land and Terra Nova Bay,and dated the glacial landforms using in-situ cosmogenic-nuclide 10 Be surface exposure dating to reconstruct the paleo-glacial *** surface of the Hollingsworth glacier lowered since the middle of Marine Isotope Stage(MIS)2(22.1 ka);therefore,the Last Glacial Maximum(LGM)occurred before that ***,geomorphic,and climatic records constrained the glacial surface slope to be between 5.4°and 6.8°.The ice was 270-320 m thicker at the LGM(MIS 2)than presently but did not override the top surface of the Benson ***,previous glacial periods such as the local LGM(MIS 4)or Penultimate Glacial Maximum(MIS 6)maintained thicker ice than the LGM(MIS 2).The Ross Ice Shelf opening during the mid-Holocene(~6 ka)caused the rapid collapse of the terminal outlet glaciers and supplied notable snow accumulation upstream,which stagnated *** greatest lowering and retreat occurred during the late Holocene(2.3~0.8 ka),when elephant seal colonies thrived in the Ross Embayment.

关键词： East Antarctic Ice Sheet Last Glacial Maximum Deglaciation Holocene Cosmogenic nuclide exposure dating Glacier reconstruction

Anti-inflammatory effects of natural volatile organic compounds from Pinus koraiensis and Larix kaempferi in mouse model

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The Journal of Biomedical Research 2019年第5期33卷 343-350页

作者： changhwan Ahn Jae-Woo Kim Mi-Jin Park Seung Ryul Kim Sung-Suk lee Eui-Bae Jeung Laboratory of Veterinary Biochemistry and Molecular Biology Veterinary Medical Center and College of Veterinary MedicineChungbuk National UniversityCheongjuChungbuk 28644Republic of Korea Division of Wood Chemistry&Microbiology Department of Forest ProductsNational Institute of Forest ScienceSeoul 02455Republic of Korea Laboratory of Biochemistry School of MedicineChungbuk National UniversityCheongjuChungbuk 28644Republic of Korea.

Natural volatile organic compounds(VOCs) extracted from conifers such as P. koraiensis and L. kaempferi have long been studied for their anti-oxidant, anti-proliferative, and anti-inflammatory effects. To evaluate the anti-inflammatory effects of VOCs from P. koraiensis and L. kaempferi, lipopolysaccharide(LPS) was administered to generate a mouse model for inflammation by the nasal route to the lungs and intraperitoneally to the whole body. VOCs of P. koraiensis and L. kaempferi were exposed to the mice by standardized wood panels with closed system. Increased levels of serum IgE and PGE2 were observed after exposure to dexamethasone and VOCs. We further determined the expression levels of inflammatory cytokine mRNA in the LPS-induced inflammation model by the reverse transcription quantitative polymerase chain reaction. Furthermore, the levels of cyclooxygenase-2, tumor necrosis factor-α, interleukin-1β, and interleukin-13 were determined in peripheral blood mononuclear cells. Those inflammatory cytokines and the key enzyme for inflammation cyclooxygenase-2 expression in PBMCs were strongly reversed by dexamethasone and VOCs. Lung tissues after nasal LPS exposure showed increased cytokine mRNA expressions which were suppressed by treatment with dexamethasone and VOCs. Furthermore, the damage induced by LPS was attenuated by dexamethasone and VOCs. In conclusion, the results from the present study indicate that VOCs of P. koraiensis and L. kaempferi have a therapeutic potential in the treatment or prevention of local and systemic inflammation due to their immunosuppressive effects.

关键词： Pinus koraiensis Larix kaempferi inflammation cytokine lungs

Stabilization of the Anatase Phase of Ti_(1-x)Sn_(x)O_(2) (x < 0.5) Nanofibers

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Nano Research 2010年第4期3卷 256-263页

作者： Kandasami Asokan Jae Young Park Sunwoo Choi changhwan Chang Sang Sub Kim School of Materials Science and Engineering Inha UniversityIncheon 402-751Republic of Korea Inter-University Accelerator Centre Aruna Asaf Ali MargNew Delhi 110067India Department of Materials Test and Analysis Research Institute of Industrial Science and TechnologyPohang 790-600Republic of Korea

We experimentally investigate the stabilization of the anatase phase of Ti_(1-x)Sn_(x)O_(2)(x<0.5)nanofibers when synthesized by an electrospinning *** as-spun nanofibers became nano-grained,polycrystalline nanofibers after calcination and the diameters of the nanofibers depend on Sn *** of the anatase phase in Ti-rich compositions and incorporation of Sn ions were confirmed by X-ray diffraction,Raman,X-ray absorption near-edge structure,and photoluminescence(PL)*** from the PL study also demonstrated the tunable nature of the optical properties,with the emission maximum shifting towards higher wavelength with increasing Sn concentration.

关键词： Electrospinning nanofiber Ti_(1-x)Sn_(x)O_(2) X-ray absorption near-edge structure(XANES)

Ultra-stable and tough bioinspired crack-based tactile sensor for small legged robots

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npj Flexible Electronics 2023年第1期7卷 339-350页

作者： Taewi Kim Insic Hong Minho Kim Sunghoon Im Yeonwook Roh changhwan Kim Jongcheon Lim Dongjin Kim Jieun Park Seunggon lee Daseul Lim Junggwang Cho Seokhaeng Huh Seung-Un Jo changhwan Kim Je-Sung Koh Seungyong Han Daeshik Kang Multiscale Bio-inspired Technology Lab Department of Mechanical EngineeringAjou University206 World cup-roYeongtong-guSuwon-siGyeonggi-do 16499South Korea Weldon School of Biomedical Engineering Purdue UniversityWest LafayetteINUSA LIG Nex1 333Pangyo-roBundang-guSeongnam-siGyeonggi-do 13488Republic of Korea Defense Industry Technology Center Agency for Defense Development61Yeouidaebang-roDongjak-guSeoulRepublic of Korea

For legged robots,collecting tactile information is essential for stable posture and efficient ***,mounting sensors on small robots weighing less than 1 kg remain challenges in terms of the sensor’s durability,flexibility,sensitivity,and *** sensors featuring ultra-sensitivity,small-size,and flexibility could be a promising candidate,but performance degradation due to crack growing by repeated use is a stumbling *** paper presents an ultra-stable and tough bio-inspired crack-based sensor by controlling the crack depth using silver nanowire(Ag NW)mesh as a crack stop *** Ag NW mesh inspired by skin collagen structure effectively mitigated crack *** sensor was very thin,lightweight,sensitive,and ultra-durable that maintains its sensitivity during 200,000 cycles of 0.5%*** demonstrate sensor’s feasibility by implementing the tactile sensation to bio-inspired robots,and propose statistical and deep learning-based analysis methods which successfully distinguished terrain type.

关键词： crack tough durability

Thickness-dependent monochalcogenide GeSe-based CBRAM for memory and artificial electronic synapses

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Nano Research 2022年第3期15卷 2263-2277页

作者： Asif Ali Haider Abbas Muhammad Hussain Syed Hassan Abbas Jaffery Sajjad Hussain changhwan Choi Jongwan Jung HMC(Hybrid Materials Center)and Department of Nanotechnology and Advanced Materials Engineering Sejong UniversitySeoul 143–747Republic of Korea Division of Materials Science and Engineering Hanyang UniversitySeoul 04763Republic of Korea

Investigating the promising chalcogenide materials for the development of memory and advanced neuromorphic computing applications is a critical step in realizing electronic memory and synaptic devices that can efficiently emulate biological synaptic ***,the assessment of monochalcogenide materials for the fabrication of highly scalable memory and electronic synaptic devices that can accurately mimic synaptic functions remain *** the present study,we investigated the thickness-dependent resistive switching(RS)behavior of conductive bridge random access memory(CBRAM)based on a monochalcogenide GeSe switching medium for its possible application in high-performance memory and electronic *** thin films of different thicknesses(6,13,24,35,47,and 56 nm)were deposited via sputtering to fabricate CBRAM devices with a stacking sequence of Ag/GeSe/Pt/Ti/SiO_(2).The devices exhibited compliance current(CC)-free and electroforming-free RS with highly stable endurance and retention characteristics with no major *** devices with a thickness of 6 nm had a low-resistance state(LRS),which required an initial reset to ensure reliable switching *** devices with a thickness of 47 nm and above exhibited the co-existence of unipolar resistive switching(U-RS)and bipolar resistive switching(B-RS)with the CC-controlled transition between the two switching *** resistance states in the 24-nm device between a high-resistance state(HRS)and an LRS were achieved by controlling the set-CC(from 5 mA to CC-free)and the reset stop voltage(from–0.5 to–1.0 V)during the set and reset processes,*** analog RS behavior of the device was further investigated with appropriate pulse measurements to emulate vital synaptic functions,including long-term potentiation(LTP),long-term depression(LTD),spike-rate-dependent plasticity(SRDP),spike-timing-dependent plasticity(STDP),paired-pulse facilitation(PPF),paired-pulse depression(PPD)and

关键词： conductive bridge random access memory(CBRAM) resistive memory switching monochalcogenide material bipolar and unipolar resistive switching multilevel resistive switching electronic synapses

Spider-inspired tunable mechanosensor for biomedical applications

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npj Flexible Electronics 2023年第1期7卷 444-452页

作者： Taewi Kim Insic Hong Yeonwook Roh Dongjin Kim Sungwook Kim Sunghoon Im changhwan Kim Kiwon Jang Seongyeon Kim Minho Kim Jieun Park Dohyeon Gong Kihyeon Ahn Jingoo lee Gunhee lee Hak-Seung lee Jeehoon Kang Ji Man Hong Seungchul lee Sungchul Seo Bon-Kwon Koo Je-sung Koh Seungyong Han Daeshik Kang Department of Mechanical Engineering Ajou UniversitySuwonKorea Department of Mechanical Engineering Pohang University of Science and TechnologyPohangKorea Department of Sustainable Environment Research Korea Institute of Machinery&MaterialsDaejeonKorea Department of Internal Medicine and Cardiovascular Center Seoul National University HospitalSeoulKorea Department of Neurology and Neurosurgery Ajou University School of MedicineSuwonKorea Department of Nano-chemical Biological and Environmental EngineeringSeokyeong UniversitySeoulKorea Institute on Aging Seoul National UniversitySeoulKorea

The recent advances of wearable sensors are remarkable but there are still limitations that they need to be refabricated to tune the sensor for target ***,biological sensory systems have the inherent potential to adjust their sensitivity according to the external environment,allowing for a broad and enhanced ***,we developed a Tunable,Ultrasensitive,Nature-inspired,Epidermal Sensor(TUNES)that the strain sensitivity was dramatically increased(GF~30k)and the pressure sensitivity could be tuned(10–254 kPa^(−1))by preset membrane *** sensor adjusts the sensitivity to the pressure regime by preset tension,so it can measure a wide range(0.05 Pa–25 kPa)with the best performance:from very small signals such as minute pulse to relatively large signals such as muscle contraction and *** verified its capabilities as a wearable health monitoring system by clinical trial comparing with pressure wire which is considered the current gold standard of blood pressure(r=0.96)and home health care system by binary classification of Old’s/Young’s pulse waves via machine learning(accuracy 95%).

关键词： Sensor adjust Spider