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Impact of uneven distribution of grain characteristics on yield strength and martensitic transformation of as-hot-rolled medium-entropy alloys

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Journal of Materials Science & Technology 2024年第10期177卷 234-245页

作者： Jungwan Lee Hyojin Park Sujung Son jae Wung bae Jin You Kim Sung Kyu Kim jae-il Jang Hyoung Seop Kim Department of Materials Science and Engineering Pohang University of Science and Technology(POSTECH)Pohang 37673Republic of Korea Department of Metallurgical Engineering Pukyong National UniversityBusan 48513Republic of Korea Technical Research Laboratories Energy and Shipbuilding Steel Research GroupPOSCOPohangRepublic of Korea Division of Materials Science and Engineering Hanyang UniversitySeoul 04763Republic of Korea Graduate Institute of Ferrous&Eco Materials Technology(GIFT) Pohang University of Science and Technology(POSTECH)Pohang 37673Republic of Korea Center for Heterogenic Metal Additive Manufacturing Pohang University of Science and Technology(POSTECH)Pohang 37673Republic of Korea Advanced Institute for Materials Research(WPI-AIMR) Tohoku UniversitySendai 980-8577Japan

As-hot-rolled medium-entropy alloys(MEAs)with unevenly distributed grain sizes of face-centered cubic grains exhibit better yield strength without uniform elongation loss compared to cold-rolled and an-nealed *** operation of dynamic recrystallization(DRX)during several hot rolling passes leads to a wide range of grain sizes from submicrons to tens of micrometers due to the grain growth after nucleation:early recrystallized grains are coarser than recently recrystallized *** only the grain size but internal dislocation density of the recently recrystallized grain is *** the tensile deformation of the hot-rolled MEAs at-196 ℃,dislocation pile-ups in the relatively soft and fine DRX grains enhance yield stress and hetero-deformation-induced strain *** to the enhanced yield stress of the as-hot-rolled MEAs,stress-induced martensitic transformation easily ***,partially DRXed MEAs hot-rolled at 800 ℃ have lower yield stress than fully DRXed ones,hot-rolled at 900 and 1000 ℃.This is attributed to the softening effect of the stress-induced body-centered cubic martensitic transformation in unrecrystallized coarse grains prior to the yielding,which lowers the yield stress of the partially DRXed *** yielding,the martensitic transformation facilitates strain hard-ening and early necking is *** study presents a fresh outlook on the uneven distribution of grain sizes by hot rolling beneficial to mechanical responses of uniform elongation of~45%despite the as-rolled states with an advantage of simplified thermo-mechanical processes.

关键词： Dynamic recrystallization Nucleation and growth Heterogeneity Grain size distribution Deformation-induced martensitic transformation

Ileocolic intussusception caused by a lipoma in an adult

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World Journal of Clinical Cases 2017年第6期5卷 254-257页

作者： Dong eun Lee jae Young Choe Department of Emergency Medicine School of Medicine Kyungpook National University Department of Pediatrics School of Medicine Kyungpook National University

Intussusception is rarely observed in adults. Adult cases account for only 5% of all cases of intussusceptions and almost 1%-5% of bowel obstruction cases. The etiology, presentation and management of intussusception in adults are different from those in children. The clinical presentation in adults often includes nonspecific signs and symptoms, thereby complicating differential diagnosis from other causes of abdominal pain. We report a 29-year-old Asian woman who visited our emergency department with complaints of fever associated with epigastric pain since one day. Abdominal computed tomography demonstrated ileocolic intussusception, and laparoscopic small bowel luminal mass resection was performed. Histopathology report confirmed a 3.5 cm × 2.7 cm submucosal lipoma in the terminal ileum. Sufficient vigilance and appropriate investigations are important for prompt diagnosis and surgical referral of patients to enable favorable outcomes. A computed tomography scan can be a helpful modality in establishing a diagnosis.

关键词： Adult intussusception ILeocolic Laparoscopic surgery Lipoma Computed tomography

Investigating the Calculation of Rotational Viscosity of the Mixture Comprising Different Kinds of Liquid Crystals： Molecular Dynamics Computer Simulation Approach

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Chinese Journal of Chemistry 2011年第1期29卷 48-52页

作者： Kim, Jinsoo Jamil, Muhammad Jung, jae eun Jang, jae eun Farzana, Ahmad Jin, Woo Lee Sang, Woo Park Woo, Min-Kyung Kwak, Ji Yeon Jeon, Young-jae Liquid Crystal Research Centre Department of Chemistry Konkuk University 143-701 Seoul Korea Division of International Affairs University College Konkuk University 143-701 Seoul Korea Samsung Advanced Institute of Technology (SAID) Yongin-shi Gyeonggi-do 446-712 Korea

Molecular dynamics （MD） computer simulation techniques, as a powerful tool commonly utilized by the liquid crystal display （LCD） community, usually are employed for computing the equilibrium and transport properties of a classical many body system, since they are very similar to real experiments in many respects. In this paper we pre- sent molecular dynamics computer simulation results taken for a mixture of the two different kinds of nematic liq- uid crystals （LCs）. We calculated rotational viscosity from Brownian behavior with friction of the mean director of the mixture comprising pentylcyanobiphenol （5CB） and decylcyanobiphenol （10CB） by using molecular dynamics computer simulation, where intermolecular potential parameter is Generalized AMBER force field （GAFF）. Our computed results show a good agreement with the experimental results.

关键词： liquid crystal mixture ab initio calculations rotational viscosity generalized AMBER force field(GAFF) molecular dynamics simulation nematic liquid crystals computer simulation

Electrical and Corrosion Properties of Titanium Aluminum Nitride Thin Films Prepared by Plasma-Enhanced Atomic Layer Deposition

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Journal of Materials Science & Technology 2017年第3期33卷 295-299页

作者： eun-Young Yun Woo-jae Lee Qi Min Wang Se-Hun Kwon School of Materials Science and Engineering Pusan National University School of Electromechanical Engineering Guangdong University of Technology

Titanium-aluminum-nitride（TiAlN） films were grown by plasma-enhanced atomic layer deposition（PEALD）on 316 L stainless steel at a deposition temperature of 200 °C. A supercycle, consisting of one AlN and ten TiN subcycles, was used to prepare TiAlN films with a chemical composition of Ti（0.25）Al（0.25）N（0.50）. The addition of AlN to TiN resulted in an increased electrical resistivity of TiAlN films of 2800 μΩ cm, compared with 475 μΩ cm of TiN films, mainly due to the high electrical resistivity of AlN and the amorphous structure of TiAlN. However, potentiostatic polarization measurements showed that amorphous TiAlN films exhibited excellent corrosion resistance with a corrosion current density of 0.12 μA/cm^2, about three times higher than that of TiN films, and about 12.5 times higher than that of 316 L stainless steel.

关键词： Titanium-aluminum nitride Plasma-enhanced atomic layer deposition Corrosion protection Ternary transition metal nitrides

Development of tenofovir disoproxil fumarate resistance after complete viral suppression in a patient with treatment-na?ve chronic hepatitis B: A case report and review of the literature

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World Journal of Gastroenterology 2018年第17期24卷 1919-1924页

作者： Woo Hee Cho Hyun jae Lee Ki bae Bang Seok bae Kim Il Han Song Department of Internal Medicine Dankook University College of MedicineCheonan 31116South Korea

Tenofovir disoproxil fumarate(TDF) is a potent nucleo-tide analogue that is recommended as first-line therapy for patients with chronic hepatitis B. The results of a longitudinal study of TDF treatment demonstrated no development of resistance. We observed one treatment-na?ve chronic hepatitis B(CHB) patient who developed TDF resistance after complete viral suppression during long-term TDF treatment. A 37-year-old HBe Ag-positive man received TDF 300 mg/d for 43 mo. The hepatitis B virus(HBV) DNA titer was 8 log_(10) copies/m L at baseline and became undetectable at 16 mo after treatment. However, the HBV DNA titer rebounded to 7.5 log_(10) copies/m L at 43 mo after treatment. We performed full sequencing to find mutation sites associated with virologic breakthrough. The results showed 9 mutation sites, most of which had not been well-known as mutation sites. We changed the therapy from tenofovir to entecavir with a regimen of 0.5 mg once daily. After 4 mo, the HBV DNA titer decreased to 267 copies/m L, and the liver enzyme levels were normalized.

关键词： Chronic hepatitis B Tenofovir Resistance Mutation

Development of a valid and reliable seven emotions impairment questionnaire and assessment of its predictability for phlegm and blood stasis

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Journal of Traditional Chinese Medicine 2016年第4期36卷 547-554页

作者： Byoung-Hee Lee Min-Yong Kim Young-bae Park Young-jae Park Department of Diagnosis and Biofunctional Medicine College of Korean MedicineKyung Hee University Seou102447 Korea Business School Kyung Hee UniversitySeou 102447 Korea Department of Diagnosis and Biofunctional Medicine College of Korean Medicine Kyung Hee University Seoul 02447 Korea Department of Diag-nosis and Biofunctional Medicine Kyung Hee UniversityHospital at Gangdong Seoul 05278 Korea.

OBJECTIVE:To develop and validate a Seven Emotions Impairment questionnaire(SEIQ),to define an optimum cut-off point for the SEIQ,and to examine whether SEI was predictive of Phlegm and Blood Stasis(BS).METHODS:Two hundred outpatients and 75 college students were asked to complete the SEIQ,the Profile of Mood States(POMS),Phlegm Pattern Questionnaire(PPQ),and BS Questionnaire(BSQ).Twelve clinicians determined whether the outpatients exhibited *** data were used to examine the internal consistency and determine validity for the ***,POMS,PPQ,and BSQ data were used to examine concurrent validity and predictability of SEI for Phlegm and BS in the college *** SEIQ scores and the clinicians' diagnoses of the outpatients were considered to define an optimum cut-off score for the ***:The 18-item SEIQ had satisfactory internal consistency(α = 0.905) and concurrent *** the construct validity test,four factors(chest-anxiety,fatigue-depression,working-family-troubles,and sleep-memory) were *** the receiver operator characteristic curve curve analysis,the sensitivity,specificity,and area under the curve of the SEIQ were 67.2%,72.1%,and 73%,*** optimum cut-off score was defined as nine *** scores were strongly predictive of Phlegm and BS(β = 0.862 and 0.673,respectively).CONCLUSION:Based on our results,we concluded that the SEIQ is a reliable and valid instrument for evaluating SEI,and is strongly predictive of Phlegm and BS.

关键词： Seven emotions Intermingled phlegm and blood-stasis Surveys and questionnaires Diagnosis Reference standards Mental health

Process of establishing design requirements and selecting alternative configurations for conceptual design of a VLA

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Chinese Journal of Aeronautics 2017年第2期30卷 738-751页

作者： Bo-Young bae Sangho Kim jae-Woo Lee Nhu Van Nguyen Bong-Cheul Chung Department of Aerospaee Information Engineering Konkuk University Seoul 143-701 Republic of Korea Konkuk Aerospace Design Airworthiness Research Institute Konkuk University Seoul 143-701 Republic of Korea

In this study,a process for establishing design requirements and selecting alternative configurations for the conceptual phase of aircraft design has been *** proposed process uses system-engineering-based requirement-analysis techniques such as objective tree,analytic hierarchy process,and quality function deployment to establish logical and quantitative ***,in order to perform a logical selection of alternative aircraft configurations,it uses advanced decision-making methods such as morphological matrix and technique for order preference by similarity to the ideal *** addition,a preliminary sizing tool has been developed to check the feasibility of the established performance requirements and to evaluate the flight performance of the selected *** present process has been applied for a two-seater very light aircraft（VLA）,resulting in a set of tentative design requirements and two families of VLA configurations：a high-wing configuration and a low-wing *** resulting set of design requirements consists of three categories：customer requirements,certification requirements,and performance *** performance requirements include two mission requirements for the flight range and the endurance by reflecting the customer *** flight performances of the two configuration families were evaluated using the sizing tool developed and the low-wing configuration with conventional tails was selected as the best baseline configuration for the VLA.

关键词： Aircraft configuration Conceptional design Design requirements Requirement analysis Very light aircraft (VLA)

Effects of Al addition on microstructure and mechanical properties of extruded Mg-3Bi alloy

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Journal of Magnesium and Alloys 2022年第7期10卷 1887-1898页

作者： Sang-Cheol Jin jae Won Cha Jun Ho bae Hui Yu Sung Hyuk Park School of Materials Science and Engineering Kyungpook National UniversityDaegu 41566Republic of Korea Implementation Research Division Korea Institute of Materials ScienceChangwon 51508Republic of Korea School of Materials Science and Engineering Hebei University of TechnologyTianjin 300130China

Effects of Al addition to a Mg±Bi binary alloy on its microstructural characteristics and tensile properties after extrusion are investigated via extrusion of Mg-3Bi±x Al(x=0,1,and 2 wt%)billets and analysis of the extruded *** Al addition negligibly affects the second-phase particles of the extruded alloy;however,an increase in the Al content causes significant decreases in the average grain size and maximum texture intensity of the extruded material owing to an increase in the area fraction of dynamically recrystallized(DRXed)*** Al addition improves the strength of the extruded alloy;this improvement is attributed to the enhanced grain-boundary hardening and solid-solution hardening effects induced by grain refinement and Al solute atoms,*** the Al content increases from 0 wt%to 1 wt%and 2 wt%,the tensile elongation increases substantially from 2.8%to 9.4%and 16.9%,*** reduction in the number and size of un DRXed grains with increasing Al content suppresses the formation and coalescence of cracks in the un DRXed grains during tension,which results in a significant improvement in the tensile ductility of the extruded *** tensile deformation,large undesirable twins that act as crack initiation sites are locally formed in the un DRXed grains of the Mg-3Bi alloy,whereas relatively smaller twins are uniformly formed in both the DRXed and the un DRXed grains of the Mg-3Bi-2Al ***,the extruded Mg-3Bi-2Al alloy has a substantially higher tensile yield strength±elongation product(2924 MPa%)than the extruded Al-free B3 alloy(381 MPa%).

关键词： Mg-Bi-Al alloy Extrusion Microstructure Strength Ductility

Variability of the Dokdo Abyssal Current observed in the Ulleung Interplain Gap of the East/Japan Sea

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Acta Oceanologica Sinica 2013年第1期32卷 12-23页

作者： KIM Yun-bae CHANG Kyung-Il PARK jae-Hun PARK Jong Jin East Sea Research Institute Korea Institute of Ocean Science and Technology Research Institute of Oceanography School of Earth and Environmental Sciences Seoul National University Ocean Science Research Department Korea Institute of Ocean Science and Technology Department of Oceanography Kyungpook National University

Subinertial fluctuation of a strong northward deep current, which is referred to the Dokdo Abyssal Current （DAC） by Chang et al. （2009）, is investigated from current records for about 16.5 and 8.0 months in the Ulle- ung Interplain Gap of the East/lapan Sea. The current below 300 m is bottom-intensified and has nearly depth-independent flow. Near bottom, the spectral peaks of the current were found near 10, 20, and 60 d. The DAC variability near 10 d and 20 d is reasonably consistent with the linear theory of topographic Rossby waves （TRWs） in the following aspects：（1） The motion is columnar and bottom-intensified; （2） the theo- retical cutoff frequency is similar to the observation; （3） The observation-based angles of the wavenumber vector are in good agreement with the theoretical ones. The wavelengths of the TRWs with periods of near 10 d and 20 d near Dokdo are significantly shorter than those with similar timescales in the open oceans （100-250 km）. It is primarily due to the weak stratification below 300 m in the East Sea. The deep cur- rent fluctuations with periods of near 10 d and 20 d were accompanied by warm events in the upper layer resulting from eddying processes and/or meandering of the Tsushima Warm Current.

关键词： East/Iapan Sea Ulleung Interplain Gap Deep currents Topographic Ressby waves