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Critical review of superplastic magnesium alloys with emphasis on tensile elongation behavior and deformation mechanisms

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Journal of Magnesium and Alloys 2022年第5期10卷 1133-1153页

作者： H.T.jeong W.J.kim Department of Materials Science and Engineering Hongik UniversitySangsu-dong 72-1 Mapo-guSeoul 121-791South Korea

The tensile elongation behavior and deformation mechanisms of superplastic Mg alloys and Mg composites were examined by extensively reviewing the literature published from the time of the first report on the superplasticity of Mg alloys to the present *** on the superplasticity of Mg alloys have been conducted mainly on Mg-Al-Zn(AZ)series alloys,Mg-Zn-Zr(ZK),Mg-Li and Mg-RE(rare earth)alloys,and in recent years,Mg-RE alloys have attracted the greatest *** effect of grain size and the type and amount of secondary phase particles on the superplasticity of Mg alloys was systematically examined and *** alloys processed by severe plastic deformation(SPD)and powder-metallurgy methods have smaller grain sizes and exhibit superior superplasticity compared to conventionally processed(by extrusion and rolling)Mg *** the AZ alloys,as the volume fraction of the Mg17Al12phase increases,smaller grains are obtained,and the low-temperature superplasticity(LTS)and high-strain-rate superplasticity(HSRS)characteristics become *** ZK60 alloy with finely dispersed Mg Zn2particles exhibits excellent LTS,while the Mg-RE alloys with a high fraction of thermally stable particles exhibit excellent ***-Li alloys can exhibit LTS even at room temperature due to the presence of a high-volume fraction of the body centered cubic(BCC)phase where atomic diffusivity is *** boundary diffusion-and lattice diffusion-controlled grain boundary sliding are found to operate as the dominant deformation mechanisms below~473 K and above~673 K,respectively,at small grain *** mechanism maps were constructed based on the analysis of the deformation behavior of superplastic Mg alloys,and from the maps,the critical conditions for achieving LTS,HSRS and simultaneous achievement of LTS and HRSR were calculated and proposed,and their importance was discussed.

关键词： Magnesium alloys Superplastic Grain size Secondary phase Grain boundary sliding

The hot compressive deformation behavior of cast Mg-Gd-Y-Zn-Zr alloys with and without LPSO phase in their initial microstructures

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Journal of Magnesium and Alloys 2022年第10期10卷 2901-2917页

作者： H.T.jeong W.J.kim Departmentof Materials Science and Engineering Hongik UniversityMapo-guSangsu-dong 72-1Seoul 121-791Republic of Korea

Samples of Mg-8.2Gd-3.8Y-1.1Zn-0.4Zr alloy with and without an intragranular lamellae-shaped long period stacking ordered(LPSO)phase were prepared through heat treatment and a series of hot compression tests on these materials were conducted to examine and evaluate the influence of LPSO on the hot compressive deformation behavior and deformation mechanisms at a given alloy *** values of activation energy for plastic flow(Qc)of the solution treated(without LPSO phase)and annealed alloys(with intragranular LPSO phase)were larger than that for pure Mg,indicating that the presence of a high amount of rare earth(RE)elements and LPSO in the Mg matrix significantly increases *** Qcvalue of the annealed alloy was larger than that of the solution treated alloy at all the strain levels(223.3 vs.195.5 k J/mol in average)and the largest difference in Qcbetween the two alloys was recorded at the smallest strain of 0.1 where precipitation of LPSO during deformation was limited in the solution treated *** observations imply that the formation of LPSO phase out of the RE-rich solid solution matrix during deformation increases Qc,but the increment is not so *** of the hot compressive data of the alloys with LPSO phase and the alloys with RE-rich solid solution matrix in literatures indicates the similarity of the effect of the LPSO and RE-rich solid solution matrix phases on Qcand high-temperature strength.

关键词： Magnesium alloys LPSO Deformation mechanism Dynamic recrystallization Activation energy for plastic flow Processing maps

Analytical evaluation and experimental validation on dynamic rocking behavior for shallow foundation considering structural response

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Earthquake Engineering and Engineering Vibration 2022年第1期21卷 37-51页

作者： Kil-Wan Ko jeong-Gon Ha Dong-Soo kim Department of Civil and Environmental Engineering UC BerkeleyCalifornia 94720USA Advanced Structures and Seismic Safety Research Division Daejeon 34057Korea Department of Civil and Environmental Engineering KAISTDaejeon 34141Korea

The challenge in the practical application of rocking foundations is the estimation of its performance,particularly the rotation angle,during a strong *** this study,the dynamic rocking behavior for a shallow foundation considering structural response was evaluated through two analytical approaches:the conventional soil-foundation-structure interaction(SFSI)governing equation of a single-degree-of-freedom(SDOF)structure on a rocking shallow foundation,and the Housner rocking model(i.e.,a rocking rigid block on a rigid base).Both approaches were validated with dynamic centrifuge *** test models consisted of a soft soil deposit,a shallow rectangular foundation,and an SDOF structure dominated by a bending behavior.A total of 11 foundation-structure systems and six seismic waves,including recorded earthquake signals and sinusoidal waves,were *** results showed that the conventional SFSI equation well predicted the maximum rotation during strong ***,this method was less accurate regarding the rotational phase information and maximum rotation of the foundation during weak *** the other hand,although the modified Housner′s rocking model required five parameters relevant to a soil-foundation-structure system,it overestimated the maximum rotation of the foundation when compared with the results from dynamic centrifuge tests.

关键词： soil-foundation-structure interaction maximum rotation angle rocking foundation Housner rocking model dynamic centrifuge test

Uncontrolled high blood pressure under total intravenous anesthesia with propofol and remifentanil:A case report

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World Journal of Clinical Cases 2022年第26期10卷 9411-9416页

作者： Min Jung Jang Jee Hee kim Hae jeong jeong Anesthesiology and Pain Medicine National Cancer CenterGoyang 10408South Korea

BACKGROUND Although propofol generally reduces blood pressure,rarely,it causes ***,the mechanism by which propofol increases blood pressure has not been established,and so far,there are only a few reported *** SUMMARY A 46-year-old woman,diagnosed with thyroid cancer,was administered general anesthesia with propofol and remifentanil for a thyroid *** increase in the concentrations of intravenous anesthetics further increased her blood *** blood pressure remained stable when anesthesia was maintained with sevoflurane and remifentanil after the interruption of propofol *** We concluded that propofol administration was the cause of increased blood pressure.

关键词： Anesthesia Intravenous Hypertension Propofol Remifentanil Tachycardia Case report

Rhamnus crenata leaf extracts exhibit anti-inflammatory activity via modulating the Nrf2/HO-1 and NF-κB/MAPK signaling pathways

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Asian Pacific Journal of Tropical Biomedicine 2022年第10期12卷 430-436页

作者： Hyun Ji Eo Da Som kim Gwang hun Park Special Forest Resources Division Department of Forest Bio-ResourcesNational Institute of Forest ScienceSuwon 16631Korea Forest Medicinal Resources Research Center National Institute of Forest ScienceYeongju 36040Korea

Objective:To elucidate the potential anti-inflammatory mechanisms of Rhamnus crenata leaf extracts using RAW264.7 ***:We used 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide assay to measure cell *** oxide(NO)production was measured using Griess *** blotting and RT-PCR assays were carried out for analyzing the protein and gene expressions of pro-inflammatory mediators,***,PD98059(ERK1/2 inhibitor),SB203580(p38 inhibitor),SP600125(JNK inhibitor),and BAY11-7082(NF-κB inhibitor)were used to evaluate the anti-inflammatory mechanism of Rhamnus crenata leaf ***:Rhamnus crenata leaf extracts significantly inhibited the production of the pro-inflammatory mediators such as NO,iNOS,COX-2,IL-1β,and TNF-αin lipopolysaccharide(LPS)-stimulated RAW264.7 *** crenata leaf extracts also suppressed LPS-induced degradation of IκB-αand nuclear accumulation of p65,which resulted in the inhibition of NF-κB activation in RAW264.7 ***,the extracts attenuated the phosphorylation of p38,ERK1/2,and JNK in LPS-stimulated RAW264.7 ***,HO-1 expression induced by Rhamnus crenata leaf extracts was significantly downregulated by SB230580,PD98059,SP600125 and ***:Rhamnus crenata leaf extract may upregulate HO-1 expression through inhibition of p38,ERK1/2,and NF-κB activation,which may contribute to the anti-inflammatory activity of the *** crenata leaf extracts may have great potential for the development of anti-inflammatory drugs to treat acute and chronic inflammatory diseases.

关键词： Anti-inflammatory activity Heme oxygenase-1 Nrf2 Mitogen-activated protein kinase Nuclear factor kappa B Rhamnus crenata

Appetite for Natech Risk Information in Japan:Understanding Citizens'Communicative Behavior Towards Risk Information Disclosure Around Osaka Bay

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International Journal of Disaster Risk Science 2022年第3期13卷 372-390页

作者： Dimitrios Tzioutzios jeong-Nam kim Ana Maria Cruz Department of Urban Management Graduate School of EngineeringKyoto UniversityKyoto615-8540Japan Gaylord College of Journalism and Mass Communication University of OklahomaNormanOK73019USA Disaster Prevention Research Institute Kyoto UniversityKyoto611-0011Japan

Effective risk communication is essential for disaster risk *** from empowering communities to make informed risk choices,risk information disclosure can also drastically enhance their disaster preparedness,especially concerning conjoint scenarios of technological and natural hazards(Natech).A fundamental precondition is the actual demand for such *** study ventures to assess whether residents around Osaka Bay have this demand,or"appetite,"for risk information disclosure,as well as to understand their communicative behavior and perceived challenges in the Japanese context through the prism of the Situational Theory of Problem *** test this framework under realistic conditions,data were collected through a household questionnaire survey from two urban areas near industrial complexes in Osaka *** results show that identifying Natech risk information deficiency as a problem was not a statistically significant predictor for individuals'motivation to ***,their motivation increased as their perceived personal involvement with the situation rose,while the perceived obstacles in doing something about it exerted a negative influence on their ***'motivation intensified their communicative actions to solve this *** segmentation underscored the elevated public perceptions concerning the issue of risk information deficiency in nearly nine out of ten *** findings indicate a strong community appetite for chemical and Natech risk information,which subsequently led to high situational motivation to engage in communicative action,particularly information *** management policy is suggested to focus on introducing chemical risk information disclosure regulatory initiatives to encourage citizen engagement.

关键词： Japan Natech risk information Participatory risk management Risk communication Situational Theory of Problem Solving(STOPS)

Bioinspired magnetic cilia:from materials to applications

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Microsystems & Nanoengineering 2023年第6期9卷 107-128页

作者： Seongjin Park Geonjun Choi Minsu Kang Woochan kim Jangho kim Hoon Eui jeong Department of Mechanical Engineering Ulsan National Institute of Science and Technology(UNIST)Ulsan44919Republic of Korea Department of Convergence Biosystems Engineering Chonnam National UniversityGwangju61186Republic of Korea Interdisciplinary Program in IT-Bio Convergence System Chonnam National UniversityGwangju61186Republic of Korea

Microscale and nanoscale cilia are ubiquitous in natural systems where they serve diverse biological *** artificial magnetic cilia have emerged as a highly promising technology with vast potential applications,ranging from soft robotics to highly precise *** this review,we comprehensively discuss the roles of cilia in nature and the various types of magnetic particles utilized in magnetic cilia;additionally,we explore the top-down and bottom-up fabrication techniques employed for their ***,we examine the various applications of magnetic cilia,including their use in soft robotics,droplet and particle control systems,fluidics,optical devices,and ***,we present our conclusions and the future outlook for magnetic cilia research and development,including the challenges that need to be overcome and the potential for further integration with emerging technologies.

关键词： magnetic overcome precise

A compact polymer–inorganic hybrid gas barrier nanolayer for flexible organic light-emitting diode displays

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npj Flexible Electronics 2022年第1期6卷 204-209页

作者： Seung hun kim Seung Yong Song Soo Youn kim Moon Won Chang Hyo jeong Kwon Kwan Hyuck Yoon Woo Yong Sung Myung Mo Sung Hye Yong Chu Display Research Center Samsung DisplayYongin-siGyeonggi-do 17113Republic of Korea Department of Chemistry Hanyang UniversitySeoul 04763Republic of Korea

Atomic layer infiltration technology allows the formation of a nanometer-thick polymer-inorganic hybrid barrier layer in polymer material for flexible organic light-emitting diode(OLED)*** this study,according to transmission electron microscopy and secondary-ion mass spectrometry analysis results under various process conditions,a compact polymer-inorganic hybrid nanolayer was successfully formed in a polymer and good barrier performance was revealed with a low water vapor transmission rate under optimal process ***,through gas chromatography-mass spectrometry measurements after ultra-violet radiation testing,polymer out-gassing decreased compared to bare *** on barrier properties,the polymer with a polymer-inorganic hybrid barrier nanolayer was applied to a flexible OLED display as a *** storage tests and folding tests,the flexible OLED display exhibits good reliability and better flexibility compared to those with an inorganic barrier *** results confirm that the polymer-inorganic hybrid nanolayer is suitable for barrier layer formation in flexible OLED displays.

关键词： diode barrier layer

Improvement in tensile strength of extruded Mg-5Bi alloy through addition of Sn and its underlying strengthening mechanisms

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Journal of Magnesium and Alloys 2022年第11期10卷 3100-3112页

作者： Sang-Cheol Jin Jae Won Cha jeong hun Lee Taekyung Lee Sang-Ho Han Sung Hyuk Park School of Materials Science and Engineering Kyungpook National UniversityDaegu 41566Republic of Korea Ulsan Regional Division Korea Institute of Industrial TechnologyUlsan 44413Republic of Korea School of Mechanical Engineering Pusan National UniversityBusan 46241Republic of Korea Department of Materials Analysis Korea Institute of Materials ScienceChangwon 51508Republic of Korea

Through an investigation of the microstructure and mechanical properties of extruded Mg–5Bi–x Sn(BT5x, x = 0, 2, 4, and 6 wt%) alloys,this study demonstrates that the addition of Sn to an Mg–5Bi binary alloy significantly improves the tensile strength of the extruded *** the extruded alloys exhibit a typical basal fiber texture and a partially dynamically recrystallized(DRXed) microstructure consisting of fine DRXed grains and coarse un DRXed grains. As the Sn content increases from 0 wt% to 6 wt%, the average size of the DRXed grains decreases from 4.2 to 2.8 μm owing to the increase in the amount of precipitates via their grain-boundary pinning effect. The extruded B5 and BT52 alloys contain numerous Mg_(3)Bi_(2) precipitates, but their size and number density are smaller and higher, respectively, in the latter *** Mg_(2)Sn precipitates as well as Mg_(3)Bi_(2)precipitates are present in the extruded BT54 and BT56 alloys, and the number density of the Mg_(2)Sn precipitates is higher in the latter alloy because of its higher Sn content. The addition of 2 wt% Sn to the B5 alloy significantly improves the yield strength(YS) and ultimate tensile strength(UTS) of the extruded alloy—by 76 and 57 MPa, respectively. This drastic improvement is the combined outcome of enhanced grain-boundary hardening, precipitation hardening, and solid-solution hardening effects induced by the refined DRXed grains, numerous precipitates, and Sn solute atoms, respectively. The further addition of 2 wt% or 4 wt% Sn to the BT52 alloy leads to moderate increments in the YS and UTS of the extruded alloy. Specifically, each addition of 2 wt% Sn increases the YS and UTS by ~26 and ~20 MPa, respectively, which is attributed mainly to the additional precipitation hardening effect induced by the Mg_(2)Sn precipitates.

关键词： Mg-Bi-Sn alloy Extrusion Precipitation Microstructure Tensile property