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Highly dense and ultrathin gadolinia-doped ceria interlayer for enhanced performance of large-area anode-supported solid oxide fuel cell

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Progress in Natural Science:Materials International 2023年第5期33卷 733-741页

作者： Sang woo Shin Amjad Hussain Muhammad Zubair Khan dong woo joh Tak-Hyung Lim Seung-Bok Lee Jong-Eun Hong Joon Hyung Shim Rak-Hyun Song Hydrogen Energy Research Division Korea Institute of Energy Research Department of Mechanical Engineering Korea University Department of Advanced Energy and System Engineering Korea University of Science and Technology(UST) 4. Department of Materials Science & Engineering Pak-Austria Fachhochschule: Institute of Applied Sciences and Technology

The fabrication of a highly dense and ultrathin Gd doped ceria(GDC) interlayer on a large-area, porous electrolyte-coated planar anode support using vacuum slurry coating is studied for application in solid oxide fuel cells(SOFCs). The electrolyte-coated planar anode support body is fabricated by tape casting and pre-sintering is performed at 1100, 1150, and 1200°C. The GDC interlayer is coated onto the pre-sintered electrolyte-coated anode support using a vacuum slurry coating process with different immersion times(30–60 s). A highly dense and ultrathin GDC interlayer with a thickness of 1.48 μm is produced after co-sintering at 1400°C. The 1200°C pre-sintered electrolyte-coated anode support showed a thin and highly dense GDC interlayer which is attributed to a lower shrinkage difference between the coated GDC interlayer and pre-sintered body. The electrochemical performance of a vacuum slurry-coated GDC interlayer cell is 38 % higher compared to that of the screen-printed GDC-coated cell at 700°C due to the greatly reduced Ohmic and electrode polarization resistances. The considerable improvement in the performance is attributed to the ultrahigh GDC density which has prevented the secondary phase formation between the cathode and electrolyte. This study presents the economical, scalable, and reproducible process for the fabrication of highly robust GDC interlayer for the large-area planar anode-supported SOFCs.

关键词： Solid oxide fuel cell Vacuum slurry coating GDC interlayer Sintering Performance

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A dynamic infiltration technique to synthesize nanolayered cathodes for high performance and robust solid oxide fuel cells

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Journal of Energy Chemistry 2022年第7期31卷 201-210,I0006页

作者： Saeed Ur Rehman Ho-Seon Song Hye-Sung Kim Muhammad Haseeb Hassan dong-woo joh Rak-Hyun Song Tak-Hyoung Lim Jong-Eun Hong Seok-Joo Park Seung-Bok Lee High Temperature Energy Conversion Laboratory Korea Institute of Energy Research152Gajeong-roYuseong-gu.Daejeon34129.Republic of Korea Department of Advanced Energy and System Engineering University of Science and Technology.217 Gajeong-ro.Yuseong-gu.Daejeon 34113.Republicof Korea

Solution infiltration is a popular technique for the surface modification of solid oxide fuel cell(SOFC)***,the synthesis of nanostructured SOFC cathodes by infiltration is a tedious process that often requires several infiltration and high temperature(≥500℃)calcination ***,fabricating large-area nanostructured cathodes via infiltration still requires serious ***,we propose a facile and scalable urea assisted ultrasonic spray infiltration technique for nanofabrication of SOFC *** is demonstrated that by using urea as a precipitating agent,the calcination after each infiltration cycle can be omitted and the next infiltration can be performed just after a drying step(≤100℃).Finally,the precipitates can be converted into a desired catalyst phase in single calcination thus,a nanostructured cathode can be fabricated in a much faster *** is also shown that the low calcination temperature of the cathode(≤900℃)can produce highly durable SOFC performance even without employing a Ce_(0.9)Gd_(0.1)O_(2)(GDC)diffusion barrier layer which provides the ease of SOFC *** coupling with an ultrasonic spray technique,the urea assisted infiltration can be scaled up for any desired cathode ***_(0.6)Sr_(0.4)Co_(0.2)Fe_(0.8)O_(3) nanolayered cathode was fabricated and it was characterized by scanning electron microscope(SEM),X-ray diffraction(XRD),and transmission electron microscopy(TEM)*** showed the formation of a nanolayer cathode just after 5 cycles of the urea assisted infiltration while the XRD and TEM confirmed the phase and stoichiometric uniformity of the 100 nm cathode *** effectiveness of the newly developed technique was further verified by the stable operation of a GDC buffer layer free SOFC having an active cathode area of 25 cm^(2) during a 1200 h durability *** research outcomes propose urea assisted ultrasonic spray infiltration as a facile,scalable,and commercially viable method

关键词： Solid oxide fuel cell(SOFC) Cathode Infiltration Nanolayer Nanofabrication GDC barrier layer free SOFC

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Mechanical alloying of platinum with 5% ZrO_2 nanoparticles for glass making tools

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Transactions of Nonferrous Metals Society of China 2014年第S1期24卷 99-105页

作者： Taek-Kyun JUNG dong-woo joh Seung-Yub LEE Myung-Sik CHOI Soong-Keun HYUN Hyo-Soo LEE Korea Institute of Industrial Technology 7-47 Songdo-dong Yenosu-gu Incheon 406-840 Korea Department of Applied Physics and Applied Mathematics Columbia University School of Materials Science and Engineering Inha University 253 Yonghyun-Dong Incheon 405-751 Korea

Synthesis and characterization of mechanically alloyed Pt-5%ZrO2(volume fraction) for structural components in the glass industry were described. Zirconia(ZrO2) nanoparticles(<100 nm) were produced by the electrical explosion of zirconium(Zr) wires, and blended with platinum(Pt) powders(<44 ?m) for 2-72 h in ambient atmosphere. The Pt particle size followed the typical decreasing trend of the normal ball milling process up to 48 h, but particle agglomeration was observed at 72 h. The grain size evolution was similar to that of the particle size, dropping down to around 50 nm at 48 h. The root mean square strain of the Pt crystallites showed the opposite behavior, maximizing at 48 h with a subsequent relaxation process. For the 48 h ball milled powders, spark plasma sintering was carried out to form a bulk disk. The measured mass loss of the sintered bulk sample shows a decent thermal stability despite its relatively low density.

关键词： platinum zirconia nanoparticle electrical wire explosion mechanical alloying

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Potential reduction in carbon fixation capacity under climate change in a Pinus koraiensis forest

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Forest Ecosystems 2024年第2期11卷 152-161页

作者： dong Kook woo Department of Civil Engineering Keimyung UniversityDaegu42601Republic of Korea

There has been an increasing recognition of the crucial role of forests, responsible for sequestering atmospheric CO_(2), as a moral imperative for mitigating the pace of climate change. The complexity of evaluating climate change impacts on forest carbon and water dynamics lies in the diverse acclimations of forests to changing environments. In this study, we assessed two of the most common acclimation traits, namely leaf area index and the maximum rate of carboxylation(V_(cmax)), to explore the potential acclimation pathways of Pinus koraiensis under climate change. We used a mechanistic and process-based ecohydrological model applied to a P. koraiensis forest in Mt. Taehwa, South Korea. We conducted numerical investigations into the impacts of(i) Shared Socioeconomic Pathways 2–4.5(SSP2-4.5) and 5–8.5(SSP5-8.5),(ii) elevated atmospheric CO_(2) and temperature, and(iii) acclimations of leaf area index and V_(cmax)on the carbon and water dynamics of P. koraiensis. We found that there was a reduction in net primary productivity(NPP) under the SSP2-4.5 scenario, but not under SSP5-8.5, compared to the baseline, due to an imbalance between increases in atmospheric CO_(2) and temperature. A decrease in leaf area index and an increase in V_(cmax)of P. koraiensis were expected if acclimations were made to reduce its leaf temperature. Under such acclimation pathways, it would be expected that the well-known CO_(2) fertilizer effects on NPP would be attenuated.

关键词： Climate change NEP Pinus koraiensis Warming Acclimation

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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

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Calculation of the Transition Temperature for Partitioned Growth of Proeutectoid Ferrite in Fe-C Base Multicomponent Alloys

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Journal of Iron and Steel Research International 2011年第S1期18卷 530-534页

作者： SUH dong-woo Graduate Institute of Ferrous Technology Pohang University of Science and TechnologyPohang 790-784Republic of Korea

According to the local equilibrium theory,the ferrite growth from alloyed austenite could be divided into the partition local equilibrium (PLE) mode and negligible partition local equilibrium (NPLE) mode.A graphical construction method proposed earlier by Hillert using in Fe-C-X ternary alloys was extended into Fe-C base multicomponent alloys to calculate the PLE/NPLE transition *** method utilize the carbon component ray,in which the substitutional alloy elements content is constant,to determine PLE/NPLE transition *** the method,the PLE/NPLE transition temperature in several alloy systems are calculated and compared with the formerly reported results.

关键词： phase transformation local equilibrium kinetics ferrite PLE/NPLE transition

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Improvement in Background Error Covariances Using Ensemble Forecasts for Assimilation of High-Resolution Satellite Data

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Advances in Atmospheric Sciences 2011年第4期28卷 758-774页

作者： Seung-woo LEE dong-Kyou LEE School of Earth and Environmental Sciences Seoul National University

Satellite data obtained over synoptic data-sparse regions such as an ocean contribute toward improving the quality of the initial state of limited-area models. Background error covariances are crucial to the proper distribution of satellite-observed information in variational data assimilation. In the NMC （National Meteorological Center） method, background error covariances are underestimated over data-sparse regions such as an ocean because of small differences between different forecast times. Thus, it is necessary to reconstruct and tune the background error covariances so as to maximize the usefulness of the satellite data for the initial state of limited-area models, especially over an ocean where there is a lack of conventional data. In this study, we attempted to estimate background error covariances so as to provide adequate error statistics for data-sparse regions by using ensemble forecasts of optimal perturbations using bred vectors. The background error covariances estimated by the ensemble method reduced the overestimation of error amplitude obtained by the NMC method. By employing an appropriate horizontal length scale to exclude spurious correlations, the ensemble method produced better results than the NMC method in the assimilation of retrieved satellite data. Because the ensemble method distributes observed information over a limited local area, it would be more useful in the analysis of high-resolution satellite data. Accordingly, the performance of forecast models can be improved over the area where the satellite data are assimilated.

关键词： 3DVAR background error covariances retrieved satellite data assimilation ensemble forecasts.

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Beach stabilization by the laying of a drainage layer

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Science China(Technological Sciences) 2012年第9期55卷 2625-2639页

作者： HUR dong-Soo LEE woo-dong CHO Won-Chul Department of Ocean Civil Engineering(Institute of Marine Industry) Gyeongsang National University445 Inpyeong-dongTongyeong 650-160Korea Department of Ocean Civil Engineering Gyeongsang National University445 Inpyeong-dongTongyeong 650-160Korea Department of Civil and Environmental Engineering Chung-Ang University221 Heuksuk-dong Dongjak-guSeoul 156-756Korea

In the present study, the stabilization effects of the laying of a drainage layer in a sandy beach were analyzed. The numerical model developed by Hur et al. （2011） was used to examine the characteristics of wave-sandy beach interaction with/without a drainage layer. This numericai model directly simulates Wave-Structure-Seabed/Sandy （WASS） beach interaction by consid- ering flow through a porous medium with inertia, laminar and turbulent resistances, and determines the eddy viscosity with the Large Eddy Simulation （LES） turbulent model in a 3-D wave field （LES-WASS-3D）. Based on the numerical results, it ap- pears that the installation of a drainage layer in the beach results in a decrease in both the mean groundwater level around the foreshore and the flow moving offshore on the beach surface. Spatial distributions of the mean groundwater level and wave setup around the foreshore with various arrangements of the drainage layer and conditions of the incident wave are also discussed in this paper.

关键词： drainage layer groundwater level foreshore LES-WASS-3D (3-D numerical simulation) beach stabilization swash zone

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Impact of Horizontal Resolution and Cumulus Parameterization Scheme on the Simulation of Heavy Rainfall Events over the Korean Peninsula

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Advances in Atmospheric Sciences 2011年第1期28卷 1-15页

作者： Seung-woo LEE dong-Kyou LEE dong-Eon CHANG School of Earth and Environmental Sciences Seoul National University National Institute of Meteorological Research Korea Meteorological Administration

In this paper, we present the results from high-resolution numerical simulations of three heavy rainfall events over the Korean Peninsula. The numerical results show that the prediction accuracy for heavy rainfall events improved as horizontal resolution increased. The fine-grid precipitation fields were much closer to the real precipitation fields in the case of large synoptic forcing over the Korean Peninsula. In the case of large convective available potential energy and weak synoptic forcing, it seems that even when using a high resolution, the models still showed poor performance in reproducing the observed high precipitation amounts. However, activation of the cumulus parameterization scheme in the intermediate resolution of 9 km, even at a grid spacing of 3 km, had a positive impact on the simulation of the heavy rainfall event.

关键词： high resolution cumulus parameterization scheme heavy rainfall numerical simulation

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Laparoscopic cholecystectomy in patients with anesthetic problems

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World Journal of Gastroenterology 2013年第29期19卷 4832-4835页

作者： Bum-Soo Kim Sun-Hyung Joo Jin-Hyun joh Jae-woo Yi Department of Surgery School of Medicine Kyung Hee University Seoul 134-727 South Korea Departments of Surgery and Anesthesiology and Pain Medicine School of Medicine Kyung Hee University Seoul 134-727 South Korea

Laparoscopic cholecystectomy is a standard operation for benign gallbladder disease. As experience with laparoscopic cholecystectomy has increased, the procedure has become possible in patients with anesthetic problems. Patients with ankylosing spondylitis or severe kyphosis represent a challenging group to anesthesiologists and laparoscopic surgeons since these diseases are associated with difficult intubation, restrictive ventilatory defects, and cardiac problems. The relatively new approach of awake fiberoptic intubation is considered to be the safest option for patients with anticipated airway difficulties. Laparoscopic cholecystectomy is usually performed under general anesthesia but considerable difficulties in anesthetic management are encountered during laparoscopic surgery; for example, hemodynamic instability may develop in patients with cardiopulmonary dysfunction due to pneumoperitoneum and position changes during the operation. Nonetheless, regional anesthesia can be considered as a valid option for patients with gallbladder disease who are poor candidates for general anesthesia due to cardiopulmonary problems. We report three cases of laparoscopic cholecystectomy successfully performed in patients with anesthetic problems that included cardiopulmonary disease, severe kyphosis, and ankylosing spondylitis.

关键词： Laparoscopic cholecystectomy Kyphosis Ankylosing spondylitis Anesthetic problems

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