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Printability and physical properties of iron slag powder composites using material extrusion?based 3D printing

Journal of Iron and Steel Research International 2021年第1期28卷 111-121页

作者： Hyungjin Kim Sangkyu lee Graduate Institute of Ferrous Technology Pohang University of Science and TechnologyPohang 37673GyeongbukRepublic of Korea Deogyeong-daero Yeogtong-guSuwon-si 16710Gyeonggi-DoRepublic of Korea

There have been many studies on three-dimensional(3D)printing using metal ***,3D printing using a metal compound has disadvantages in that it increases the cost for supplying metal materials.A method of using slag which is a recyclable material has been proposed to reduce *** the growing demand for additive manufacturing using byproducts,slag has gained attention as a diverse recycling material for 3D printing technologies.A new fabrication approach was analyzed for producing porous bodies via additive manufacturing for blending slag and reinforced ***,because of its low quality due to low strength,low durability,and structural defeats,the amount of slag generated is high,and its usability remains ***,slag is an excellent material with a huge potential for producing structures with high mechanical properties,and limited research in the area of slag recycling has been conducted due to difficulties in sintering the iron *** develop a recycling approach that utilizes slag in 3D printing powders,a study to increase the industrial usability by mixing slag and ceramic beads was described.A method was presented to compare the physical properties of 3D printed slag parts with the physical properties of those generated by blending iron slag,alumina,and *** order to find the mixing ratio with the optimum physical properties,the average particle size,bending stress,and maximum compressive stress were *** combination ratio to obtain the highest strength was when iron slag powder was 40%and alumina was 60%.In addition,the specimens by composition to which the stress test was applied were cut to analyze the tissue under a *** is thought that cracking in the sintered structure decreases and density increases by mixing alumina and zirconium,contributing to increased *** a ceramic bead composed of alumina and zirconium is mixed with slag to form a composite material,a metal compound having a lev

关键词： Slag By-product Mechanical property 3D printing Additive manufacturing

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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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Geochemical evaluation of low salinity hot water injection to enhance heavy oil recovery from carbonate reservoirs

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Petroleum Science 2019年第2期16卷 366-381页

作者： Ji Ho lee Kun Sang lee Department of Earth Resources and Environmental Engineering Hanyang University

Although low salinity water injection(LSWI) has recovered residual oil after the conventional waterflood, highly viscous oil has remained in heavy oil reservoirs. Hot water injection is an economic and practical method to improve oil mobility for viscous oil reservoirs. It potentially controls temperature-dependent geochemical reactions underlying the LSWI mechanism and oil viscosity. Therefore, this study has modeled and evaluated a hybrid process of low salinity hot water injection(hot LSWI) to quantify synergistic effects in heavy oil reservoirs. In comparison to seawater injection(SWI) and LSWI, hot LSWI results in more cation ion-exchange(Ca^(2+) and Mg^(2+)) and more wettability modification. Hot LSWI also reduces oil viscosity. In core-scaled systems, it increases oil recovery by 21% and 6% over SWI and LSWI. In a pilotscaled reservoir, it produces additional oil by 6% and 3% over SWI and LSWI. Probabilistic forecasting with uncertainty assessment further evaluates the feasibility of hot LSWI to consider uncertainty in the pilot-scaled reservoir and observes enhanced heavy oil production. This study confirms the viability of hot LSWI due to synergistic effects including enhanced wettability modification and oil viscosity reduction effects.

关键词： Low salinity water injection Hot water injection Wettability modification Geochemical reaction Viscosity reduction

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Present and Future of Phase‑Selectively Disordered Blue TiO2 for Energy and Society Sustainability

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Nano-Micro Letters 2021年第3期13卷 53-65页

作者： Yongguang Luo Hyoyoung lee Center for Integrated Nanostructure Physics(CINAP) Institute for Basic Science(IBS)2066 SeoburoJangan‑guSuwon 16419Republic of Korea Department of Chemistry Sungkyunkwan University2066 SeoburoJangan‑guSuwon 16419Republic of Korea Creative Research Institute(CRI) Sungkyunkwan University2066 SeoburoJangan‑guSuwon 16419Republic of Korea Department of Biophysics Sungkyunkwan University2066 SeoburoJangan‑guSuwon 16419Republic of Korea

Titanium dioxide(TiO2)has garnered attention for its promising photocatalytic activity,energy storage capability,low cost,high chemical stability,and ***,conventional TiO2 has low energy harvesting efficiency and charge separation ability,though the recently developed black TiO2 formed under high temperature or pressure has achieved elevated *** phase-selectively ordered/disordered blue TiO2(BTO),which has visible-light absorption and efficient exciton disassociation,can be formed under normal pressure and temperature(NPT)*** perspective article first discusses TiO2 materials development milestones and insights of the BTO structure and construction ***,current applications of BTO and potential extensions are summarized and suggested,respectively,including hydrogen(H2)production,carbon dioxide(CO2)and nitrogen(N2)reduction,pollutant degradation,microbial disinfection,and energy ***,future research prospects are proposed for BTO to advance energy and environmental sustainability by exploiting different strategies and *** unique NPT-synthesized BTO can offer more societally beneficial applications if its potential is fully explored by the research community.

关键词： Blue TiO2(BTO) Phase-selective disordering Visible-light-driven photocatalyst Charge separation Energy and society sustainability

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Crown Fuel Characteristics and Carbon Emission from Japanese Red Pine Stands Burned by Crown Fire in Mt. Palgong, South Korea

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Journal of Mountain Science 2012年第5期9卷 656-664页

作者： Byungdoo lee Myoung Soo WON Yohan lee Myung Bo lee Division of Forest Disaster Management Korea Forest Research Institute College of Forestry Oregon State University

Carbon emissions from forest fires are considered an important factor of ecosystem carbon balance and global climate change. Carbon emissions from Japanese red pine stands （Pinus densiflora S. et Z.） burned by crown fire were estimated at Mt. Palgong in Daegu Metropolitan City, and crown fuel characteristics, including crown bulk density, crown base height, and fuel moisture content of Japanese red pine, were analyzed. Total biomass combusted was calculated by subtracting the biomass of burned stands from that of unburned stands exhibiting similar stand structures and site environments. Ten trees in the unburned area and five trees in the burned area were cut by using direct harvesting techniques to estimate crown layer biomass. All biomass sampled was oven-dried and weighed. The dry weight ratios of stems, branches, and needles were 7o%, 21%, and 9%, respectively. The available fuel load susceptible to combustion during the crown fire spread was equivalent to 55% of the crown layer biomass. The crown bulk density was 0.24 kg/m3 on average. The estimated amount of CO2 was 23,454 kg CO2/ha for the crown layer. These results will be useful for calculating the amount of CO2 emitted from forest fires and for developing a forest carbon model in P. densiflora forests.

关键词： Biomass burning Crown fire Fuelcharacteristics Bulk density Pinus densiflora

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Micro-precision surface finishing using magneto-rheological fluid

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Science China(Technological Sciences) 2012年第1期55卷 56-61页

作者： CHOI SeungBok lee DeukWon lee ChulHee Department of Mechanical Engineering Inha UniversityIncheon 402-751Korea

In order to improve the surface quality of machining workpiece, this paper studied a micro-precision surface finishing method by applying magneto-rheological fluid to the machined surface. A pin-on-disc testing apparatus was used to carry out surface finishing experiment of steel under different magnetic fields. Magneto-rheological fluid is colloidal suspension and stiffens in- to semi-solid when subjected to a magnetic field. Thus, the surface roughness of the finished surface could be controlled by magneto-rheological fluid under the different magnetic fields. Several sets of tests were performed with various normal loads, finishing speeds and magnetic fields. Removal rate was calculated by the removal loss monitored by testing apparatus, while microstmctures of the finished surface of pin and disk were observed by scanning electron microscope. The micro-precision roughness of finished surface was analyzed by surface profilorneter. The obtained test results showed different surface charac- teristics of the test material under different magnetic fields and proved the feasibility of this micro-precision surface finishing method to reduce the surface roughness of machining workpiece efficiently. At the same time, the effects of the various ap- plied normal loads and rotating speeds on the finishing surface by rnagneto-rheological fluid were investigated.

关键词： magnetorheological fluid surface fmishing removal rate surface roughness

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Correlation of microstructure with tensile behavior and properties of API X70 pipeline steels subjected to strain aging

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Journal of Iron and Steel Research International 2020年第3期27卷 319-324页

作者： Sang-in lee Byoungchul Hwang Department of Materials Science and Engineering Seoul National University of Science and TechnologySeoul 01811Republic of Korea

Variations in tensile behavior and properties after pre-strain and thermal aging were differently affected by strain aging phenomenon dependent on *** increasing polygonal ferrite fraction,decrement in uniform elongation is increased,and the increment in yield-to-tensile ratio is slightly decreased after pre-strain and thermal ***,it can be concluded that the polygonal ferrite has contradictory effects on strain aging resistance although the polygonal ferrite still contributes to improvement of uniform elongation after strain aging.

关键词： Steel Microstructure Strain aging Deformability Pipeline

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Study on the transaction linkage technique combined with the designated terminal for 5G-enabled IoT

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Digital Communications and Networks 2022年第2期8卷 124-131页

作者： Kyungroul lee Kangbin Yim School of Computer Software Daegu Catholic UniversityGyeongsan38430South Korea Department of Information Security Engineering Soonchunhyang UniversityAsan31538South Korea

With the growth of the scale of the market for Internet banking and e-commerce,the number of Internet-based financial markets has been ***,hacking incidents continuously affect Internet-banking *** this reason,a countermeasure is required to improve the security of the online identification *** current security and authentication mechanisms applied to financial services,such as Internet banking services for 5G-enabled IoT,do not ensure *** this paper,a transaction-linkage technique with which the designated terminal is combined is proposed to solve this fundamental *** technique improves the security of online identification mechanisms because it is possible to counteract all of the existing security *** proposed technique supports mutual authentication and is safe from eavesdropping attacks,replay attacks,spoofing attacks,and service-denial ***,the technique supports non-repudiation by storing the transaction history in a transaction-linkage *** believe that the security of Internet-banking services for 5G-enabled IoT will be increased through the utilization of the proposed technique.

关键词： Transaction-linkage technique Designated terminal Internet banking Online-authentication mechanism 5G-enabled IoT

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Iridium oxide fabrication and application: A review

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Journal of Energy Chemistry 2020年第7期29卷 152-172,I0005页

作者： Hansaem Jang Jaeyoung lee Electrochemical Reaction&Technology Laboratory(ERTL) School of Earth Sciences and Environmental EngineeringGwangju Institute of Science and Technology(GIST)Gwangju 61005Republic of Korea Ertl Center for Electrochemistry and Catalysis GRIGISTGwangju 61005Republic of Korea

Despite the scarcity and cost of iridium oxide,it is still the material of choice in numerous fields of science and applications,including capacitors,electrochromism,sensors,and various oxidation electrocatalysis(e.g.,chlorine evolution reaction,detoxification,and oxygen evolution reaction).Such versatility is attributed to the distinct features of iridium oxides,such as their activity,biocompatibility,conductivity,and *** features and properties of iridium oxides are strongly dependent on the fabrication *** this review,methodologies relating to the synthesis and fabrication of solid-state iridium oxides have been thoroughly collected and *** and crystallization techniques for iridium oxides are also *** the end of the review,the effects of utilizing a certain fabrication method on the characteristics of the iridium oxide product are recapitulated,together with the recommended application of the product in various fields.

关键词： Iridium oxide Iridium dioxide Electrode Electrocatalyst Electrochromism pH sensor Oxygen evolution reaction

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Block Incremental Dense Tucker Decomposition with Application to Spatial and Temporal Analysis of Air Quality Data

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Computer Modeling in Engineering & Sciences 2024年第4期139卷 319-336页

作者： SangSeok lee HaeWon Moon lee Sael Department of Artificial Intelligence Ajou UniversitySuwon-si16499Korea Department of Software and Computer Engineering Ajou UniversitySuwon-si16499Korea

How can we efficiently store and mine dynamically generated dense tensors for modeling the behavior of multidimensional dynamic data?Much of the multidimensional dynamic data in the real world is generated in the form of time-growing *** example,air quality tensor data consists of multiple sensory values gathered from wide locations for a long *** data,accumulated over time,is redundant and consumes a lot ofmemory in its raw *** need a way to efficiently store dynamically generated tensor data that increase over time and to model their behavior on demand between arbitrary time *** this end,we propose a Block IncrementalDense Tucker Decomposition(BID-Tucker)method for efficient storage and on-demand modeling ofmultidimensional spatiotemporal *** that tensors come in unit blocks where only the time domain changes,our proposed BID-Tucker first slices the blocks into matrices and decomposes them via singular value decomposition(SVD).The SVDs of the time×space sliced matrices are stored instead of the raw tensor blocks to save *** modeling from data is required at particular time blocks,the SVDs of corresponding time blocks are retrieved and incremented to be used for Tucker *** factor matrices and core tensor of the decomposed results can then be used for further data *** compared our proposed BID-Tucker with D-Tucker,which our method extends,and vanilla Tucker *** show that our BID-Tucker is faster than both D-Tucker and vanilla Tucker decomposition and uses less memory for storage with a comparable reconstruction *** applied our proposed BID-Tucker to model the spatial and temporal trends of air quality data collected in South Korea from 2018 to *** were able to model the spatial and temporal air quality *** were also able to verify unusual events,such as chronic ozone alerts and large fire events.

关键词： Dynamic decomposition tucker tensor tensor factorization spatiotemporal data tensor analysis air quality

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