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Microstructural characteristics and low-cycle fatigue properties of AZ91 and AZ91-Ca-Y alloys extruded at different temperatures

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Journal of Magnesium and Alloys 2023年第3期11卷 892-902页

作者： Ye Jin Kim young Min Kim Jun Ho Bae Soo-Hyun joo Sung Hyuk Park School of Materials Science and Engineering Kyungpook National UniversityDaegu 41566Republic of Korea Advanced Metals Division Korea Institute of Materials ScienceChangwon 51508Republic of Korea Department of Materials Science and Engineering Dankook UniversityCheonan 31116Republic of Korea

The commercial AZ91 alloy and nonflammable SEN9(AZ91-0.3Ca-0.2Y,wt%)alloy are extruded at 300°C and 400°*** microstructure,tensile and compressive properties,and low-cycle fatigue(LCF)properties are investigated,with particular focus on the influence of the extrusion *** the AZ91 and SEN9 materials extruded at 300°C(300-materials),numerous fine Mg_(17)Al_(12)particles are inhomogeneously distributed owing to localized dynamic precipitation during extrusion,unlike those extruded at 400°C(400-materials).These fine particles suppress the coarsening of recrystallized grains,decreasing the average grain size of *** the four extruded materials have considerably different microstructures,the difference in their tensile yield strengths is insignificant because strong grain-boundary hardening and precipitation hardening effects in 300-materials are offset almost completely by a strong texture hardening effect in ***,owing to their finer grains and weaker texture,300-materials have higher compressive yield strengths *** the LCF tests,{10-12}twinning is activated at lower stresses in 400-materials than in *** the fatigue damage accumulated per cycle is smaller in 400-materials,they have longer fatigue lives than those of 300-materials.A fatigue life prediction model for the investigated materials is established on the basis of the relationship between the total strain energy density(ΔW_(t))and the number of cycles to fatigue failure(N_(f)),and it is expressed through a simple equation(ΔW_(t)=10·N_(f)-0.59).This model enables fatigue life prediction of both the investigated alloys regardless of the extrusion temperature and strain amplitude.

关键词： AZ91-Ca-Y Extrusion temperature Microstructure Low-cycle fatigue Fatigue life prediction model

Development of a Concentration Measurement Technique for Steady State Solid-liquid Mixing using a Neural Network

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Journal of Thermal Science 2013年第5期22卷 478-483页

作者： Deog Hee Doh joo Ho Yum Gyeong Rae cho Myung Ho Kim Gyong Won Ryu Masahiro Takei Division of Mechanical and Energy Systems Engineering Korea Maritime UniversityYeongdo-gu Busan Korea Graduate School Korea Maritime UniversityYeongdo-gu Busan Korea R&D Institute-5 Agency for Defense DevelopmentJochiwongil 462Yuseong Daejeon 305-152 Korea Graduate School of Mechanical Engineering Artificial Science Division Chiba UniversityJapan

A measurement technique that can measure the concentration of the solid particles in liquid flow was *** measurement system consists of a color camera and three LCD *** solid particles were put at the bottom of a cylindrical mixing tank in which JetA1 oil was *** mixing of the solid particles was performed by rotating a propeller type agitator with three different rotation speed(500,600,700 r/min).Mixing state was visualized by the LCD displays and a color *** color intensity of the glass particles changes with their *** color information was decoded into three principle colors R,G,and B so that,the calibration curve of color-to-concentration was performed using these information.A neural network was used for this *** transient concentration field of the solid particles was quantitatively visualized.

关键词： Solid particles JetA1 oil Transient mixing Neural Network Concentration

Radiolarians from the Pohang Basin,Southeast Korea and Paleoceanographic Implications

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Acta Geologica Sinica(English Edition) 2012年第6期86卷 1426-1433页

作者： young-Suk BAK Jong-Deock LEE Hyesu YUN Jinyong OH Seong-joo LEE Kyungpook National University chonbuk National University Chungnam National University

We identified a total of 101 species and two subspecies of radiolarians belonging to 56 genera from 95 samples collected from the Hagjeon and Duho Formations in the Pohang Basin of the southeastern Korean Peninsula. On the basis of the biostratigraphic range of Cyrtocapsella cornuta and Theocorys redondoensis, the depositional period of the upper Hagjeon and lowest Duho Formations was determined to be early to late Middle Miocene. The occurrence of deep-dwelling radiolarians indicates that the paleobathymetry seems to become gradually progressing toward an upper bathyal environment in the middle part of the Hagjeon Formation. However, we prefer to accept another interpretation for the occurrence of deep-sea indicators in the Hagjeon and the lowest part of the Duho Formations, and consider the presence of a region of upwelling cold water that might have simulated a deep-water environment in relatively shallow water. This interpretation is based on the present upwelling of a cold-water mass off the southeast coast of Korea, the occurrence of upwelling microfossils from the Pohang Basin, and the effect of the closing of the Korea Strait approximately 15 Ma. We also considered that the uppermost part of the studied section represents a shallow-water environment.

关键词： radiolarian depositional environment upweHing Pohang Basin

Septic thrombophlebitis of the porto-mesenteric veins as a complication of acute appendicitis

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World Journal of Gastroenterology 2008年第28期14卷 4580-4582页

作者： Yeon Soo Chang Sun young Min Sun Hyung joo Suk- Hwan Lee Department of Surgery Kyung Hee University College of MedicineSeoul 134-727South Korea

Pylephlebitis, a rare complication of acute appendicitis, is defined as thrombophlebitis of the portal venous system. Pylephlebitis usually occurs due to secondary infection in the region drained into the portal system. We report a case of pylephlebitis caused by acute appendicitis. The patient was transferred from a private clinic 1 wk after appendectomy with the chief complaints of high fever and abdominal pain. He was diagnosed with pylephlebitis of the portal vein and superior mesenteric vein by CT-scan. The patient was treated with antibiotics and anticoagulation therapy, and discharged on the 25th day and follow-up CT scan showed a cavernous transformation of portal thrombosis.

关键词： Acute appendicitis Pylephlebitis Antibiotics Anti-coagulation therapy

Collusion-resistant convertible ring signature schemes

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Science China(Information Sciences) 2015年第1期58卷 134-149页

作者： HWANG Jung Yeon CHANG Ku-young cho Hyun Sook SONG Boyeon SUSILO Willy Electronics and Telecommunications Research Institute(ETRI) DaejeonKorea Korea Institute of Science and Technology Information (KISTI) DaejeonKorea Centre for Computer and Information Security Research School of Computer Science and Software EngineeringUniversity of WollongongAustralia

A ring signature scheme provides signer ambiguity by hiding a signer in a ring of arbitrary members appropriately. A convertible ring signature scheme is an extension of a ring signature scheme that authenticates a signer and proves that a real signer and no one else generated a ring signature. In this paper, we first show that the recent convertible ring signature scheme proposed by Jeong et al. is vulnerable to collusion ***, we present a formal security model for a convertible ring signature with collusion resistance. The security notion of a convertible ring signature is intrinsically different from that of an ordinary ring signature due to the conversion property. For our collusion resistance, we consider full key exposure, that is, even an adversary who knows all secret keys will not be able to break the collusion resistance. Finally, we construct a novel convertible ring signature scheme with collusion resistance and prove the security of the scheme in the presented security model. We also compare our scheme with the existing ring signature schemes in the literature to show its advantages.

关键词： authentication ring signature anonymity convertibility collusion-resistance

Mitochondria-targeting drug conjugates for cytotoxic, anti-oxidizing and sensing purposes:current strategies and future perspectives

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Acta Pharmaceutica Sinica B 2018年第6期8卷 862-880页

作者： Gantumur Battogtokh Yeon Su choi Dong Seop Kang Sang Jun Park Min Suk Shim Kang Moo Huh Yong-Yeon cho joo young Lee Hye Suk Lee Han Chang Kang Department of Pharmacy Integrated Research Institute of Pharmaceutical Sciences and BK21 PLUS Team for Creative Leader Program for Pharmacomics-based Future Pharmacy College of Pharmacy The Catholic University of Korea Division of Bioengineering Incheon National University Department of Polymer Science and Engineering Chungnam National University

mitochondrial-targeting moieties to anticancer drugs, antioxidants and sensor molecules. Among them, the most widely applied mitochondrial targeting moiety is triphenylphosphonium(TPP), which is a delocalized cationic lipid that readily accumulates and penetrates through the mitochondrial membrane due to the highly negative mitochondrial membrane potential. Other moieties, including short peptides,dequalinium, guanidine, rhodamine, and F16, are also known to be promising mitochondrial targeting agents. Direct conjugation of mitochondrial targeting moieties to anticancer drugs, antioxidants and sensors results in increased cytotoxicity, anti-oxidizing activity and sensing activity, respectively,compared with their non-targeting counterparts, especially in drug-resistant cells. Although many mitochondria-targeted anticancer drug conjugates have been investigated in vitro and in vivo, further clinical studies are still needed. On the other hand, several mitochondria-targeting antioxidants have been analyzed in clinical phases I, II and III trials, and one conjugate has been approved for treating eye disease in Russia. There are numerous ongoing studies of mitochondria-targeted sensors.

关键词： Anticancer agents Antioxidants Direct conjugation Mitochondria-targeting Sensing agents

Obesity promotes oxidative stress and exacerbates blood-brain barrier disruption after high-intensity exercise

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Journal of Sport and Health Science 2017年第2期6卷 225-230页

作者： Hee-Tae Roh Su-Youn cho Wi-young So Department of Physical Education Dong-A University Busan 604-714 Republic of Korea School of Taekwondo College of Creative Human ResourcesYoungsan UniversityYangsan-si 626-790Republic of Korea Sports and Health Care Major College of Humanities and ArtsKorea National University of TransportationChungju-si 380-702Republic of Korea

Purpose: The purpose of this study was to investigate the effects of obesity and high-intensity acute exercise on oxidant-antioxidant status,neurotrophic factor expression, and blood-brain barrier(BBB) ***: Twenty-four healthy, untrained men(12 non-obese(mean 14.9% body fat) and 12 obese subjects(mean 29.8% body fat)) performed20 min of continuous submaximal aerobic exercise at 85% maximal oxygen consumption. Blood sampling was performed to examine the oxidant-antioxidant status(reactive oxygen species(ROS) and superoxide dismutase(SOD)), neurotrophic factors(brain-derived neurotrophic factor(BDNF) and nerve growth factor(NGF)), and BBB disruption(S100β and neuron-specific enolase) before and after acute ***: The obese group showed significantly higher pre-exercise serum ROS levels and significantly lower pre-exercise serum SOD levels than the non-obese group(p < 0.05). Serum ROS, SOD, BDNF, NGF, and S100β levels were significantly increased post-exercise compared with pre-exercise levels in both the non-obese and the obese groups(p < 0.05). The obese group showed significantly higher serum ROS, BDNF, NGF,and S100β levels post-exercise compared to the non-obese group(p < 0.05).Conclusion: Our study suggests that episodic vigorous exercise can increase oxidative stress and blood neurotrophic factor levels and induce disruption of the BBB. Moreover, high levels of neurotrophic factor in the blood after exercise in the obese group may be due to BBB disruption,and it is assumed that oxidative stress was the main cause of this BBB disruption.

关键词： Antioxidant enzyme Blood-brain barrier Exercise Neurotrophic factor Obesity Oxidative stress

Ternary Forecast of Heavy Snowfall in the Honam Area, Korea

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Advances in Atmospheric Sciences 2009年第2期26卷 327-332页

作者： Keon Tae SOHN Jeong Hyeong LEE young Seuk cho Department of Statistics Pusan National University Division of Management Information Science Dong-A University

The objective of this study is to improve the statistical modeling for the ternary forecast of heavy snowfall in the Honam area in Korea. The ternary forecast of heavy snowfall consists of one of three values, 0 for less than 50 mm, 1 for an advisory （50-150 ram）, and 2 for a warning （more than 150 mm）. For our study, the observed daily snow amounts and the numerical model outputs for 45 synoptic factors at 17 stations in the Honam area during 5 years （2001 to 2005） are used as observations and potential predictors respectively. For statistical modeling and validation, the data set is divided into training data and validation data by cluster analysis. A multi-grade logistic regression model and neural networks are separately applied to generate the probabilities of three categories based on the model output statistic （MOS） method. Two models are estimated by the training data and tested by the validation data. Based on the estimated probabilities, three thresholds are chosen to generate ternary forecasts. The results are summarized in 3 × 3 contingency tables and the results of the three-grade logistic regression model are compared to those of the neural networks model. According to the model training and model validation results, the estimated three-grade logistic regression model is recommended as a ternary forecast model for heavy snowfall in the Honam area.

关键词： ternary forecast of heavy snow MOS multi-grade logistic regression neural networks threshold

Enhancement of photoresponsive electrical characteristics of multilayer MoS2 transistors using rubrene patches

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Nano Research 2015年第3期8卷 790-800页

作者： Eun Hei cho Won Geun Song Cheol joon Park Jeongyong Kim Sunkook Kim Jinsoo joo Department of Physics Korea University Seou1136-713 R. O. Korea Department of Electronics and Radio Engineering Institute for Laser Engineering Kyung Hee University Yongin Gyeonggi-do 446-70 I R. O. Korea Center for Integrated Nanostructure Physics (CINAP) Institute for Basic Science (IBS) Department of Energy Science Sungkyunkwan University Suwon 440-746 R. O. Korea

Multilayer MoS2 is a promising active material for sensing, energy harvesting, and optoelectronic devices owing to its intriguing tunable electronic band structure. However, its optoelectronic applications have been limited due to its indirect band gap nature. In this study, we fabricated a new type of phototransistor using multilayer MoS2 crystal hybridized with p-type organic semiconducting rubrene patches. Owing to the outstanding photophysical properties of rubrene, the device characteristics such as charge mobility and photoresponsivity were considerably enhanced to an extent depending on the thickness of the rubrene patches. The enhanced photoresponsive conductance was analyzed in terms of the charge results of the nanoscale laser confocal time-resolved PL measurements. transfer doping effect, validated by the microscope photoluminescence （PL） and

关键词： MoS2 rubrene transistor photoresponsivity charge transfer