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Dual-frequency piezoelectric micromachined ultrasound transducer based on polarization switching in ferroelectric thin films

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Microsystems & Nanoengineering 2023年第5期9卷 233-243页

作者： Jin Soo Park Soo Young Jung dong Hun kim Jung Ho Park Ho won Jang Tae Geun kim Seung-Hyub Baek Byung Chul Lee Bionics Research Center Korea Institute of Science and TechnologySeoul 02792Republic of Korea Department of Electrical Engineering Korea UniversitySeoul 02841Republic of Korea Center for Electronic Materials Korea Institute of Science and TechnologySeoul 02792Republic of Korea Department of Material Science and Engineering Seoul National UniversitySeoul 08826Republic of Korea Division of Bio-Medical Science and Technology KIST SchoolUniversity of Science and Technology(UST)Seoul 02792Republic of Korea KHU-KIST Department of Converging Science and Technology Kyung Hee UniversitySeoul 02447Republic of Korea

Due to its additional frequency response,dual-frequency ultrasound has advantages over conventional ultrasound,which operates at a specific frequency ***,a tunable frequency from a single transducer enables sonographers to achieve ultrasound images with a large detection area and high *** facilitates the availability of more advanced techniques that simultaneously require low-and high-frequency ultrasounds,such as harmonic imaging and image-guided *** this study,we present a novel method for dual-frequency ultrasound generation from a ferroelectric piezoelectric micromachined ultrasound transducer(PMUT).Uniformly designed transducer arrays can be used for both deep low-resolution imaging and shallow high-resolution *** switch the ultrasound frequency,the only requirement is to tune a DC bias to control the polarization state of the ferroelectric *** vibration of the PMUT membrane strongly depends on the polarization state,producing low-and high-frequency ultrasounds from a single excitation *** strategy for dual-frequency ultrasounds meets the requirement for either multielectrode configurations or heterodesigned elements,which are integrated into an ***,this technique significantly reduces the design complexity of transducer arrays and their associated driving circuits.

关键词： piezoelectric ferroelectric enable

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Simple reactor for the synthesis of silver nanoparticles with the assistance of ethanol by gas-liquid discharge plasma

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Plasma Science and Technology 2019年第4期21卷 34-43页

作者： Pan LU dong-Wook kim dong-Wha PARK Department of Chemistry and Chemical Engineering Inha University100 Inha-Ro.Michuhol-guIncheon 22212Republic of Korea Regional Innovation Center for Environmental Technology of Thermal Plasma(RIC-ETTP: Inha University100 Inha-RoMichuhol-gu.Incheon 22212.Republic of Korea

Atmospheric pressure plasma technology is gaining increasing importance because it is a simple and tunable synthesis process for the production of metallic *** addition to the development of the power supply,improving the reactor is also one of the main strategies to enhanee the *** this study,a simple reactor for the gas-liquid discharge plasma induced by argon gas was applied to synthesize silver nanopailicles from silver nitrate(AgNO3)in *** AC power supply with a peak voltage of 3.5 kV was *** frequency and on-time were set to 50 kHz and 2.5“s,*** oscilloscope showed that the rising time was approximately 2“*** ethanol was used as the source for the reactive reducing *** more additional comp on ents existed in the solution during the discharge and neither of the electrodes was in contact with the treated *** temperature in creased by 10°C within 1 min without a cooling *** was the main impurity and was expected to be produced from the decomposition of the organics under the *** elevated temperature decreased the organic by-products by evaporation and could also decrease the production of *** electron microscopy showed that the spherical silver nanoparticles with a size of approximately 10 nm were synthesized with a crystal structure and that a low concentration of ethanol prefers the production of the mono-dispersed colloid.

关键词： silver nanoparticles synthesis nonthermal plasma ethanol reduction gas-liquid discharge

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Vapor-Liquid Equilibrium of Toluene-Polycyclic Aromatic Hydrocarbon System in Sub- and Supercritical State

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Chinese Journal of Chemical Engineering 2002年第6期10卷 657-660页

作者： Cheol-Joong kim dong-Bok won 等 R&Dcenter SKcorporationTaejon305-370Korea DeptartmentofChemicalEngineering ChungnamNationalUniversityTaejon305-765Korea

The phase behaviors of toluene/polycyclic aromatic hydrocarbon mixture systems were investigated with a continuous-flow type apparatus at 573.2, 598.2, 623.2 and 648.2 K, while the pressure changed from 1 to 5MPa. The pseudo-binary phase behaviors were predicted with the Peng-Robinson equation of state with interaction parameters between toluene and pseudo-components considered. The phase diagrams of the system have been classified following the category of phase boundary diagram models. The extraction selectivity and efficiency of tolu-ene as a solvent was discussed by comparing with that of hexane. The prediction model for selectivity was also suggested.

关键词： vapor-liquid equilibrium polycyclic aromatic hydrocarbon mixtures supercritical fluid extraction selectivity*

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Analysis of the Oscillatory Flows of Multiple Shock Waves in a Constant Area Duct

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Journal of Thermal Science 2024年第3期33卷 794-806页

作者： K JAMES Jintu kim Heuy dong Department of Mechanical Engineering Andong National UniversityAndong36729Republic of Korea CAD-IT Korea Co. Ltd.Seoul08591Republic of Korea

The oscillatory response of multiple shock waves to downstream perturbations in a supersonic flow is studied numerically in a rectangular *** shock waves are formed inside the duct at a shock Mach number of *** duct has an exit height of H,and the effect of duct resonance on multiple shock oscillations is investigated by attaching exit ducts of lengths 0H,50H,and *** downstream disturbance frequency varied from 10 Hz to 200 Hz to explore the oscillation characteristics of the multiple shock *** oscillatory response of shock waves under self-excited and forced oscillation conditions are analyzed in terms of wall static pressure,shock train leading-edge location,shock train length,and the size of the separation *** extent of the initial shock location increases with an increase in exit duct length for the self-excited oscillation *** analysis of the shock train leading edge and the spectral analysis of wall static pressure variations are *** variation in the shock train length is analyzed using the pressure ratio method for self-excited as well as forced *** RMS amplitude of the normalized shock train length(ζ_(ST))increases with an increase in the exit duct length for the self-excited oscillation *** the downstream perturbation frequency is increased,ζ_(ST)is decreased for exit duct *** all exit duct designs and downstream forcing frequencies,the size of the separation bubble grows and shrinks during the shock oscillations,demonstrating the dependence on duct resonance and forced oscillations.

关键词： shock train downstream disturbance supersonic flow shock wave boundary layer interaction duct resonance flow separation

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The Effect of Diffuser Angle on the Discharge Coefficient of a Miniature Critical Nozzle

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Journal of Thermal Science 2010年第3期19卷 222-227页

作者： Jae Hyung kim Heuy dong kim Toshiaki Setoguchi School of Mechanical Engineering Andong National UniversityAndong760-749Korea Department of Mechanical Engineering Saga University1HonjoSagaJapan

Many researches on critical nozzles have been performed to accurately measure the mass flow rate of gas flow,and to standardize the performance as a flow ***,much interest is being paid on the measurement of very small mass flow rate in industry fields such as MEMS ***,the design and performance data of the critical nozzles obtained so far have been applied mainly to the critical nozzles with comparatively large diameters,and the works available on miniature critical nozzles are *** the present study,a computational fluid dynamics method has been applied to investigate the influence of the diffuser angle on discharge coefficient of the miniature critical *** computations,the throat diameter of critical nozzle is varied from 0.2 mm to 5.0 mm and the diffuser angle is changed from 2 deg to 8 *** computational results are validated with some experimental data *** results show that the present computational results predict appropriately the discharge coefficient of the gas flows through miniature critical *** is known that the discharge coefficient is considerably influenced by the diffuser angle,as the throat diameter of nozzle becomes small below a certain *** implies that the miniature critical nozzles should be carefully designed.

关键词： Compressible Flow Critical Nozzle Compressible Flow Discharge Coefficient Diffuser Configuration Reynolds Number

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Supersonic Cavity Based Combustion with Kerosene/Hydrogen Fuel

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Journal of Thermal Science 2015年第2期24卷 164-172页

作者： Rajarshi Das Jeong Soo kim Heuy dong kim Department of Mechanical Engineering Andong National University School of Mechanical Engineering Pukyong National University

A comparative study with kerosene and hydrogen fuel in a model scramjet combustor has been carried out nu- merically. The effect of fuel-air equivalence ratio on the flow field properties in a cavity based mixing mechanism at a freestream Math number of 2.08 has been probed. The investigation has been carried out in a two dimension- al numerical model where a cavity of length to depth ratio of 2 is mounted on one of the walls of the flow channel The flow field shock structure is observed to change with the change in fuel-air equivalence ratio. Total pressure loss is observed to depend both on fuel air equivalence ratio and the fuel type. The spread of fuel in the test sec- tion shows marked variation with the equivalence ratio. Performance of injector location on the fuel-air mixing is also probed during the course of the investigation.

关键词： Scramjet fuel-air mixing kerosene hydrogen equivalence ratio

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Sperm hyaluronidase is critical to mammals'fertilization for its ability to disperse cumulus-oocyte complex layer

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Asian Journal of Andrology 2022年第4期24卷 411-415页

作者： dong-won Seol Sang Hoon Joo Young-Hyun kim Bong-Seok Song Bo-Woong Sim Sun-Uk kim Soojin Park Gabbine Wee Ekyune kim Laboratory Animal Center Daegu-Gyeongbuk Medical Innovation Foundation(DGMIF)Daegu 41061Korea College of Pharmacy Catholic University of DaeguGyeongbuk 38430Korea National Primate Research Center(NPCR) Korea Research Institute of Bioscience and BiotechnologyChungcheongbuk-do 28116Korea Futuristic Animal Resource and Research Center Korea Research Institute of Bioscience and BiotechnologyChungcheongbuk-do 28116Korea Department of Biochemistry and Molecular Biology Melvin and Bren Simon Comprehensive Cancer CenterIndiana University School of MedicineIndianapolisIN 46202USA

Glycosylphosphatidylinositol-anchored sperm hyaluronidases have long been believed to assist in sperm penetration through the cumulus-oocyte complex(COC);however,their role in mammalian fertilization remains ***,we have shown that hyaluronidase 5(Hyal5)/Hyal7 double-knockout(dKO)mice produce significantly fewer offspring than their wild-type(WT)counterparts because of defective COC *** infertility is mainly caused by a low sperm *** can be further exacerbated by the deficiency of sperm hyaluronidase,which disperses the cumulus cells of the outer layer of the *** the current study,we evaluated the effects of a low count of Hyal-deficient sperm and conditions of ovulated oocytes on the fertilization rate using a mouse *** results demonstrated that a low sperm count further decreases the in vitro fertilization(IVF)rate of Hyal-deficient dKO *** addition,the dKO spermatozoa resulted in a fertilization rate of 12.5%upon fertilizing COCs with a thick cumulus layer,whereas the IVF rate was comparable to that of WT spermatozoa when oocytes with a thin or no cumulus layer were ***,we proved that the IVF rate of dKO spermatozoa could be recovered by adding rat spermatozoa as a source of sperm *** results suggest that a deficiency of proteins involved in fertilization,such as sperm hyal,has a vital role in fertilization.

关键词： HYAL5 HYAL7 cumulus-oocyte complex fertilization infertility sperm hyaluronidase

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Boosted Lithium-Ion Transport Kinetics in n-Type Siloxene Anodes Enabled by Selective Nucleophilic Substitution of Phosphorus

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Nano-Micro Letters 2024年第10期16卷 618-637页

作者： Se In kim Woong-Ju kim Jin Gu Kang dong-Wan kim School of Civil Environmental and Architectural EngineeringKorea University02841 SeoulSouth Korea Nanophotonics Research Center Korea Institute of Science and Technology02792 SeoulSouth Korea

Doped two-dimensional(2D)materials hold significant promise for advancing many technologies,such as microelectronics,optoelectronics,and energy ***,n-type 2D oxidized Si nanosheets,namely n-type siloxene(n-SX),are employed as Li-ion battery *** thermal evaporation of sodium hypophosphite at 275℃,P atoms are effectively incorporated into siloxene(SX)without compromising its 2D layered morphology and unique Kautsky-type crystal ***,selective nucleophilic substitution occurs,with only Si atoms being replaced by P atoms in the O_(3)≡Si-H *** resulting n-SX possesses two delocalized electrons arising from the presence of two electron donor types:(i)P atoms residing in Si sites and(ii)H *** doping concentrations are varied by controlling the amount of precursors or their mean free *** at 2000 mA g^(-1),the n-SX electrode with the optimized doping concentration(6.7×10^(19) atoms cm^(-3))delivers a capacity of 594 mAh g^(-1) with a 73%capacity retention after 500 *** improvements originate from the enhanced kinetics of charge transport processes,including electronic conduction,charge transfer,and solid-state *** approach proposed herein offers an unprecedented route for engineering SX anodes to boost Li-ion storage.

关键词： Li-ion battery Two-dimensional N-type siloxene Doping mechanism Kinetics

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Highly Aligned Ternary Nanofiber Matrices Loaded with MXene Expedite Regeneration of Volumetric Muscle Loss

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Nano-Micro Letters 2024年第4期16卷 269-292页

作者： Moon Sung Kang Yeuni Yu Rowoon Park Hye Jin Heo Seok Hyun Lee Suck won Hong Yun Hak kim dong‑Wook Han Department of Cogno‑Mechatronics Engineering College of Nanoscience and NanotechnologyPusan National UniversityBusan 46241Republic of Korea Medical Research Institute School of MedicinePusan National UniversityYangsan 50612Republic of Korea Department of Anatomy School of MedicinePusan National UniversityYangsan 50612Republic of Korea Engineering Research Center for Color‑Modulated Extra‑Sensory Perception Technology Pusan National UniversityBusan 46241Republic of Korea Department of Biomedical Informatics School of MedicinePusan National UniversityYangsan 50612Republic of Korea Periodontal Disease Signaling Network Research Center and Dental and Life Science Institute School of DentistryPusan National UniversityYangsan 50612Republic of Korea BIO‑IT Fusion Technology Research Institute Pusan National UniversityBusan 46241Republic of Korea Present Address:Osstem Implant Inc. Seoul 07789Republic of Korea

Current therapeutic approaches for volumetric muscle loss(VML)face challenges due to limited graft availability and insufficient *** overcome these limitations,tissue-engineered scaffolds have emerged as a promising *** this study,we developed aligned ternary nanofibrous matrices comprised of poly(lactide-co-ε-caprolactone)integrated with collagen and Ti_(3)C_(2)T_(x)MXene nanoparticles(NPs)(PCM matrices),and explored their myogenic potential for skeletal muscle tissue *** PCM matrices demonstrated favorable physicochemical properties,including structural uniformity,alignment,microporosity,and *** vitro assays revealed that the PCM matrices promoted cellular behaviors and myogenic differentiation of C2C12 ***,in vivo experiments demonstrated enhanced muscle remodeling and recovery in mice treated with PCM matrices following VML *** insights from next-generation sequencing revealed that MXene NPs facilitated protein and ion availability within PCM matrices,leading to elevated intracellular Ca^(2+)levels in myoblasts through the activation of inducible nitric oxide synthase(i NOS)and serum/glucocorticoid regulated kinase 1(SGK1),ultimately promoting myogenic differentiation via the m TOR-AKT ***,upregulated i NOS and increased NO–contributed to myoblast proliferation and fiber fusion,thereby facilitating overall myoblast *** findings underscore the potential of MXene NPs loaded within highly aligned matrices as therapeutic agents to promote skeletal muscle tissue recovery.

关键词： Ti_(3)C_(2)T_(x)MXene nanoparticle Ternary nanofibrous matrices Myogenesis Regeneration of volumetric muscle loss Next generation sequencing

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Cycloaddition of CO_2 and propylene oxide by using M(HBTC)(4,4'-bipy)·3DMF(M=Ni,Co,Zn) metal-organic frameworks

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Chinese Journal of Catalysis 2018年第8期39卷 1311-1319页

作者： Seol-Hee kim Robin Babu dong-Woo kim wonjoo Lee Dae-won Park Division of Chemical and Biomolecular Engineering Pusan National University Busan 609-735 Korea Korea Research Institute of Chemical Technology Ulsan 681-802 Korea

Three pillar-layered metal-organic frameworks（MOFs） based on M（HBTC）（4,4＇-bipy）.3DMF（M =Ni, Co, and Zn; HBTC = 1,3,5-benzenetricarboxylic acid, 4,4＇-bipy = 4,4′-bipyridine） were synthesized using a solvothermal method. Zn（HBTC）（4,4＇-bipy）.3DMF was synthesized for the first time using both a solvothermal and microwave method, and subsequently characterized by various physicochemical methods. The structure of M（HBTC）（4,4＇-bipy）.3DMF consisted of honeycomb grid layers of M2＋ ions and BTC units, which were further linked by the 4,4＇-bipy pillars to form a three-dimensional highly porous framework. All the MOFs displayed excellent synergistic catalytic properties with alkyl ammonium halides（TBAX） in the solventless fixation of CO_2 with epoxides to produce cyclic carbonates. The catalytic activities of these MOFs followed the trend Zn Co Ni,which was explained by the acid-base bifunctional properties. The microwave-synthesized Zn（HBTC）（4,4＇-bipy）.3DMF material exhibited physical, chemical, and catalytic properties that were similar to those of the catalyst obtained using a conventional solvothermal synthesis. The scope of various parameters, including recyclability, was studied, and a plausible reaction mechanism was suggested.

关键词： M(HBTC)(4,4'-bipy)·3DMF(M=Ni,Co,Zn) Microwave method Carbon dioxide Epoxide Cyclic carbonate

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