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Progress in Natural Science:Materials International 2024年第3期34卷 606-613页

作者： Muhammad Zubair Khan Amjad Hussain Seung-bok lee Tak-Hyoung Lim Rak-Hyun Song Department of Materials Science & Engineering Pak-Austria Fachhochschule: Institute of Applied Sciences and Technology Hydrogen Energy Research Division Korea Institute of Energy Research Department of Advanced Energy and System Engineering Korea University of Science and Technology (UST)

In the present study, the operational lifetime of a solid oxide fuel(SOFC) short stack is predicted by investigating the performance degradation of both the short stack and its cells throughout 1000 h at 800°C. The short stack and integral cell voltages are continuously measured during the long-term test, with electrochemical impedance spectroscopy(EIS) conducted every 200 h. The short stack voltage decreased rapidly for the initial 200–300 h and afterwards, it decreased at a slow rate due to the increase in the Ohmic and polarization resistances in the same manner. Scanning electron microscopy results show that there is no delamination or cracking among constituent layers of the short-stack cells. The single degradation effects of the Ni coarsening in the anode, cation migration and surface segregation in cathode and oxide scale growth in metallic interconnect mesh are successfully integrated into a comprehensive lifetime prediction model. The experimentally measured voltage degradation data of the short stack fits well with the developed mathematical model and allows the successful prediction of the lifetime up to 50,000 h.

关键词： SOFC Stack Degradation Impedance Lifetime

Pharmacokinetic comparison with different assays for simultaneous determination of cis-,trans-cefprozil diastereomers in human plasma

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Journal of Pharmaceutical Analysis 2021年第3期11卷 351-363页

作者： Seung-Hyun Jeong Ji-Hun Jang Hea-Young Cho Yong-bok lee College of Pharmacy Chonnam National University77 Yongbong-roBuk-guGwangju61186Republic of Korea College of Pharmacy CHA University335 Pangyo-roBundang-guSeongnam-siGyeonggi-Do13488Republic of Korea

The purpose of this study was to compare pharmacokinetic(PK)parameters obtained using two newly developed assays,HPLC-UV and UPLC-ESI-MS/*** of assay and results obtained therefrom are very important in PK studies and can have a major impact on the PK-based clinical dose and usage *** this study,we developed two new methods that are most commonly used in biosample analysis and focused on PK parameters obtained from *** HPLC-UV equipped with a Luna-C8 column using UV detector,cefprozil diastereomers were separated using water containing 2%(V/V)acetic acid and acetonitrile as a mobile *** UPLC-ESI-MS/MS equipped with a HALO-C18 column,cefprozil diastereomers were separated using 0.5%(V/V)aqueous formic acid containing 5 mM ammoniumformate buffer and methanol as a mobile *** showed high resolution,sensitivity,and selectivity without interference by plasma *** intra-and inter-day precisions(CV,%)were within 8.88%for HPLC-UV and UPLC-ESI-MS/*** of both methods was 95.67%-107.50%.These two analytical methods satisfied the criteria of international guidance and could be successfully applied to PK *** of PK parameters between two assays confirmed that there is a difference in the predicted minimum plasma concentrations at steady state,which may affect clinical dose and usage ***,we confirmed possible correlation between PK parameters and various biochemical parameters after oral administration of 1000 mg cefprozil to humans.

关键词： Cefprozil diastereomers Comparison HPLC-UV UPLC-ESI-MS/MS Pharmacokinetic parameter Biochemical parameters

Bioinspired Segment Robot with Earthworm-like Plane Locomotion

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Journal of Bionic Engineering 2016年第2期13卷 292-302页

作者： Chang-Woo Song dong-Jun lee Seung-Yop lee Department of Mechanical Engineering Sogang University 1 Shinsu-dong Mapo-gu Seoul 121-742 Republic of Korea

In this paper, a miniaturized segment robot using solenoids is developed to mimic the plane locomotion of earthworms. The bioinspired robot is composed of five segmented bodies, and one segment has two solenoid actuators. This robot can move linearly and it can also turn due to the pair of solenoid actuators that facilitate the earthworm-like peristaltic locomotion. We have designed a miniaturized solenoid with a permanent magnet plunger in order to increase the total electromagnetic force. A theoretical analysis is performed to predict the linear and turning motions of each segment, and the optimal profiles of input signals are obtained for fast locomotion. Experiments are then conducted to determine the linear and turning motions of the segment robot. It takes about 0.5 s for the five segments to complete one cycle of the peristaltic locomotion. In experiments, the segment robot is shown to have the linear and angular velocities of 27.2 mm·s^-1 （0.13 body-length per second） and 2 degrees per second, respectively.

关键词： bioinspired robot earthworm peristaltic locomotion solenoid segmented robot

Difference in extrusion temperature dependences of microstructure and mechanical properties between extruded AZ61 and AZ91 alloys

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Journal of Magnesium and Alloys 2023年第5期11卷 1683-1696页

作者： dong Hee lee Gyo Myeong lee Sung Hyuk Park School of Materials Science and Engineering Kyungpook National UniversityDaegu 41566Republic of Korea

The effects of extrusion temperature on the microstructure and tensile properties of extruded AZ61 and AZ91 alloys are investigated by subjecting them to hot extrusion at 300 and 400℃.Although the average grain size of the extruded AZ61 alloy slightly increases from 9.5 to 12.6μm with increasing extrusion temperature,its resultant microstructural variation is *** contrast,the average grain size of the extruded AZ91 alloy significantly increases from 5.7 to 22.5μm with increasing extrusion temperature,and the type of Mg17Al12 precipitates formed in it changes from fine dynamic precipitates with a spherical shape to coarse static precipitates with a lamellar *** the extrusion temperature increases,the tensile yield strength of the extruded AZ61 alloy increases from 183 to 197 MPa while that of the extruded AZ91 alloy decreases from 232 to 224 *** tensile elongations of the extruded AZ61 and AZ91 alloys decrease with increasing extrusion temperature,but the degree of decrease is significant in the latter *** different extrusion temperature dependences of the tensile properties of the extruded AZ61 and AZ91 alloys are discussed in terms of their microstructural characteristics,strengthening mechanisms,and crack initiation sites.

关键词： Mg-Al-Zn alloys Extrusion temperature Precipitation Strengthening mechanism Tensile properties

The genetic variation in Monocarboxylic acid transporter 2 （MCT2） has functional and clinical relevance with male infertility

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Asian Journal of Andrology 2014年第5期16卷 694-697,I0007页

作者： Jinu lee dong Ryul lee Suman lee Yonsei Institute of Pharmaceutical Sciences College of Pharmacy Yonsei University Incheon Department of Biomedical Science CHA University Seongnam-si Korea

Monocarboxylic acid transporter 2 （MCT2） transports pyruvate and lactate outside and inside of sperms, mainly as energy sources and plays roles in the regulation of spermatogenesis. We investigated the association among genetic variations in the MCT2 gene, male infertility and MCT2 expression levels in sperm. The functional and genetic significance of the intron 2 （＋28201A 〉 G, rs10506398） and 3＇ untranslated region （UTR） single nucleotide polymorphism （SNP）（＋2626G 〉 A, rs10506399） of MCT2 variants were investigated. Two MCT2 polymorphisms were associated with male infertility （n = 471, P 〈 0.05）. In particular, the MCT2-3＇ UTR SNP （＋2626 G 〉 A） had a strong association with the oligoasthenoteratozoospermia （OAT） group. The ＋2626GG type had an almost 2.4-fold higher sperm count than that of the ＋2626AA type （＋2626GG; 66 x 106 vs ＋2626AA; 27 x 106, P 〈 0.0001）. The MCT2-3＇ UTR SNP may be important for expression, as it is located at the MCT2 3＇ UTR. The average MCT2 protein amount in sperm of the ＋2626GG type was about two times higher than that of the ＋2626AA type. The results suggest that genetic variation in MCT2 has functional and clinical relevance with male infertility.

关键词： 3' UTR male infertility monocarboxylic acid transporter 2 single nucleotide polymorphism sperm

Mixed-dimensional stacked nanocomposite structures for a specific wavelength-selectable ambipolar photoresponse

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Nano Research 2024年第6期17卷 5549-5558页

作者： Young Jae Park Jaeho Shim Joo Song lee Kyu Seung lee Ji-Yeon Kim Kang bok Ko Sang-Youp Yim Seongjun Kim Hoon-Kyu Shin donghee Park Yong Ju Yun dong Ick Son Institute of Advanced Composite Materials Korea Institute of Science and TechnologyJeollabuk-do 55324Republic of Korea National Institute for Nanomaterials Technology Pohang University of Science and TechnologyGyeongsangbuk-do 37673Republic of Korea Department of Semiconductor Science and Technology Semiconductor Physics Research CenterJeonbuk National UniversityJeonju 54896Republic of Korea Advanced Photonics Research Institute Gwangju Institute of Science and TechnologyGwangju 61005Republic of Korea Center for Opto-Electronic Materials and Devices Post-Silicon Semiconductor InstituteKorea Institute of Science and TechnologySeoul 02792Republic of Korea Graduate School of Energy and Environment(KU-KIST Green School) Korea UniversitySeoul 02841Republic of Korea KIST School Department of Nanomaterials and Nano ScienceUniversity of Science and Technology(UST)Daejeon 34113Republic of Korea

Mixed-dimensional composite structures using zero-dimensional(0D)quantum dots(QDs)and two-dimensional(2D)transition metal dichalcogenides(TMDs)materials are expected to attract great interest in optoelectronics due to the potential to generate new optical ***,we report on the unique optical characteristics of a devices with mixed dimensional vertically stacked structures based on tungsten diselenide(WSe_(2))/CdSeS QDs monolayer/molybdenum disulfide(MoS_(2))(2D/0D/2D).Specifically,it exhibits an ambipolar photoresponse characteristic,with a negative photoresponse observed in the 400-600 nm wavelength range and a positive photoresponse appeared at 700 nm *** resulted in the high negative responsivity of up to 52.22 mA·W^(−1)under 400 nm,which is 163 times higher than that of the photodetector without CdSeS *** also demonstrated the negative photoresponse,which could be due to increased carrier collision probability and non-radiative *** modeling and simulation reveal that Auger recombination among the types of non-radiative recombination is the main cause of negative photocurrent ***,we discovered ambipolar photoresponse near a specific wavelength corresponding to the energy of quantum *** study revealed interesting phenomenon in the mixed low-dimensional stacked structure and paved the way to exploit it for the development of innovative photodetection materials as well as for optoelectronic applications.

关键词： mixed-dimension quantum dot heterostructure photodetector ambipolar photoresponse

Safety and efficacy of tenofovir in chronic hepatitis B-related decompensated cirrhosis

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World Journal of Gastroenterology 2017年第13期23卷 2396-2403页

作者： Soon Kyu lee Myeong Jun Song Seok Hyun Kim Byung Seok lee Tae Hee lee Young Woo Kang Suk Bae Kim Il Han Song Hee bok Chae Soon Young Ko Jae dong lee Division of Hepatology Department of Internal MedicineDaejeon St.Mary's HospitalCollege of MedicineThe Catholic University of Korea Department of Internal Medicine Chungnam University Hospital Department of Internal Medicine Konyang University Hospital Department of Internal Medicine Dankook University Hospital Department of Internal Medicine Chung Buk University Hospital Department of Internal Medicine Konkuk University Chungju Hospital

AIM To evaluate the safety and efficacy of tenofovir disoproxil fumarate(TDF) as a first-line therapy in decompensated liver disease. METHODS We enrolled 174 chronic hepatitis B-related liver cirrhosis patients treated with 300 mg/d TDF at six Korean centers. Of the 174 cirrhosis patients, 57 were assigned to the decompensated cirrhosis group and 117 were assigned to the compensated cirrhosis group. We followed the patients for 12 mo and evaluated clinical outcomes, including biochemical, virological, and serological responses. We also evaluated changes in hepatic and renal function and compared the decompensated and compensated cirrhosis groups. RESULTS The 1-year complete virological response(CVR) and Hepatitis B e antigen(HBe Ag) seroconversion were seen in 70.2% and 14.2% in the decompensated cirrhosis group, respectively. The rates of HBe Ag seroconversion/loss and ALT normalization at month 12 were similar in both groups. TDF treatment was also effective for decreasing the level of hepatitis B virus(HBV) DNA in both groups, but CVR was higher in the compensated group(88.9% vs 70.2%, P = 0.005). Tenofovir treatment for 12 mo resulted in improved Child-Turcotte-Pugh(CTP) and model for end-stage liver disease(MELD) scores in decompensated group(P < 0.001). Of the 57 decompensated patients, 39(68.4%) achieved CTP class A and 27(49.1%) showed improvement in the CTP score of 2 points after 12 mo of TDF. The observed rate of confirmed 0.5 mg/d L increases in serum levels of creatinine in the decompensated and compensated cirrhosis group were 7.0% and 2.5%, respectively(P < 1.000).CONCLUSION TDF therapy in decompensated cirrhosis patients was effective for decreasing HBV DNA levels and improving hepatic function with relatively lower CVR than in compensated cirrhosis. Thus, physicians should carefully monitor not only renal function but also treatment responses when using TDF in decompensated cirrhosis patients.

关键词： Tenofovir Decompensated liver cirrhosis Compensated liver cirrhosis Virological response Renal safety

Effect of Length Scale Tuning of Background Error in WRF-3DVAR System on Assimilation of High-Resolution Surface Data for Heavy Rainfall Simulation

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Advances in Atmospheric Sciences 2012年第6期29卷 1142-1158页

作者： Ji-Hyun HA dong-Kyou lee Atmospheric Sciences Program School of Earth and Environmental SciencesSeoul National UniversitySeoul 151-747Korea

We investigated the impact of tuning the length scale of the background error covariance in the Weather Research and Forecasting （WRF） three-dimensional variational assimilation （3DVAR） system. In particular, we studied the effect of this parameter on the assimilation of high-resolution surface data for heavy rainfall forecasts associated with mesoscale convective systems over the Korean Peninsula. In the assimilation of high-resolution surface data, the National Meteorological Center method tended to exaggerate the length scale that determined the shape and extent to which observed information spreads out. In this study, we used the difference between observation and background data to tune the length scale in the assimilation of high-resolution surface data. The resulting assimilation clearly showed that the analysis with the tuned length scale was able to reproduce the small-scale features of the ideal field effectively. We also investigated the effect of a double-iteration method with two different length scales, representing large and small-length scales in the WRF-3DVAR. This method reflected the large and small-scale features of observed information in the model fields. The quantitative accuracy of the precipitation forecast using this double iteration with two different length scales for heavy rainfall was high; results were in good agreement with observations in terms of the maximum rainfall amount and equitable threat scores. The improved forecast in the experiment resulted from the development of well-identified mesoscale convective systems by intensified low-level winds and their consequent convergence near the rainfall area.

关键词： WRF 3DVAR tuning surface data heavy rainfall

Creep and tensile properties of press molding joined GMT-sheets

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Transactions of Nonferrous Metals Society of China 2011年第A01期21卷 170-174页

作者： Jin-Woo KIM dong-Gi lee Center for NDE Iowa State University Department of Mechatronics Engineering Chosun University

GMT-sheet is used in automobile bumper with high rigidity and strength, and its joining strength is influenced by lap length, one of the joined molding conditions. Fracture strength was calculated by dividing fracture load with cross-sectional area. Total five repeated measurements were made to obtain the average value. Tensile test was conducted at room temperature for 10 specimens. In addition, the effect of compression ratio on creep and tensile performance during lap joined molding was discussed. With increasing lap length, the lap joining efficiency of GMT-sheet was increased. However, higher compression ratio reduced the joining efficiency. Creep test on GMT-sheet showed abrupt fracture without tertiary creep. This can be explained by the weak thermal resistance of the resin. If GMT-sheet was exposed to high temperature for a long time, it was easily failed by external force.

关键词： GMT-sheet randomly oriented composite unidirectional oriented composite compression ratio lap joint

Rolling Stability Enhancement via Balancing Tail for a Water-running Robot

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Journal of Bionic Engineering 2015年第3期12卷 395-405页

作者： HyunGyu Kim dong Gyu lee TaeWon Seo School of Mechanical Engineering Yeungnam University Gyeongsan 712-749 Republic of Korea

Running on water produces very energy-efficient and fast motion in water environments. Many studies have been performed to develop bio-inspired water-running robots. To achieve good performance, the lifting force is very important for a robot to be able to run on water. The loss of lifting force is associated with the rolling stability of the robot on water. The purpose of this study is to improve the rolling stability of a water-running robot through the periodic motion of a balancing tail. Kinematic analysis was performed to calculate the motions of the legs and the tail, and static analysis was performed to calculate the balancing effect of the tail motion. A numerical model was suggested to determine the dynamic performance of the robotic platform based on kinematic and static results. A simulation based on the numerical model was performed, and the results were compared with empirical data from a robot prototype. The simulation results are in good agreement with the experimental data in terms of rolling stability The lifting force has only a slight effect. The results of this study can be used as a guideline for designing a stable water-running robot.

关键词： water-running robot balancing tail rolling stability lifting force basilisk lizard