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Porous FeS nanofibers with numerous nanovoids obtained by Kirkendall diffusion effect for use as anode materials for sodium-ion batteries

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Nano Research 2017年第3期10卷 897-907页

作者： jung Sang Cho Jin-Sung Park Yun chan Kang Department of Materials Science and Engineering Korea University Anam-Dong Seongbuk-Gu Seou1136-713 Republic of Korea Department of Engineering Chemistry Chungbuk National University Chungbuk 361-763 Republic of Korea

Porous FeS nanofibers with numerous nanovoids for use as anode materials for sodium-ion batteries were prepared by electrospinning and subsequent sulfidation. The post-treatment of the as-spun Fe（acac）3-polyacrylonitrile composite nanofibers in an air atmosphere yielded hollow Fe2O3 nanofibers due to Ostwald ripening. The ultrafine Fe2O3 nanocrystals formed at the center of the fiber diffused toward the outside of the fiber via Ostwald ripening. On sulfidation, the Fe2O3 hollow nanofibers were transformed into porous FeS nanofibers, which contained numerous nanovoids. The formation of porosity in the FeS nanofibers was driven by nanoscale Kirkendall diffusion. The porous FeS nanofibers were very structurally stable and had superior sodium-ion storage properties compared with the hollow Fe2O3 nanofibers. The discharge capacities of the porous FeS nanofibers for the Ist and 150th cycles at a current density of 500 mA.g-1 were 561 and 592 mA.h-g-1, respectively. The FeS nanofibers had final discharge capacities of 456, 437, 413, 394, 380, and 353 mA-h.g-1 at current densities of 0.2, 0.5, 1.0, 2.0, 3.0, and 5.0 A.g-1, respectively.

关键词： iron sulfide sodium-ion batteries Kirkendall effect nanofibers electrospinning

In situ infrared, Raman and X-ray spectroscopy for the mechanistic understanding of hydrogen evolution reaction

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Journal of Energy Chemistry 2024年第3期90卷 632-651,I0014页

作者： Andi Haryanto Kyounghoon jung chan Woo Lee Dong-Wan Kim Department of Chemistry Kookmin UniversitySeoul 02707Republic of Korea School of Civil Environmental and Architectural EngineeringKorea UniversitySeoul 02841Republic of Korea

Hydrogen production by water reduction reactions has received considerable attention because hydrogen is considered a clean-energy carrier,key for a sustainable energy *** methods have been widely used to study the reaction mechanism of the hydrogen evolution reaction(HER),but the calculation results need to be supported by experimental results and direct evidence to confirm the mechanistic *** this review,we discuss the fundamental principles of the in situ spectroscopic strategy and a theoretical model for a mechanistic understanding of the *** addition,we investigate recent studies by in situ Fourier transform infrared(FTIR),Raman spectroscopy,and X-ray absorption spectroscopy(XAS) and cover new findings that occur at the catalyst-electrolyte interface during *** spectroscopic strategies provide practical ways to elucidate catalyst phase,reaction intermediate,catalyst-electrolyte interface,intermediate binding energy,metal valency state,and coordination environment during HER.

关键词： Hydrogen evolution reaction Infrared spectroscopy Raman spectroscopy X-ray absorption spectroscopy Reaction mechanism

Global warming related carbon dioxide abatement proposals

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Journal of Environmental Sciences 1993年第3期5卷 269-278页

作者： jung sik Koh UN ESCAP Bangkok 10200 Thailand

The relationship between man-made CO2 emission and atmospheric CO2 concentration has been established. The factors that affect CO2 reduction allotment and the impacts on future energy demand and supply were discussed, in order to help energy policy makers both in developed countries and in developing countries for understanding the fundamental constraint on energy sector resulted from global warming related CO2 reduction, and hopefully in finding a common objective starting point to deal with global warming negotiation in energy sector, and to investigate the optimum stabilization goal and process acceptable to all sovereign countries that based on equity and applicability.

关键词： global wanning carbon dioxide abatement optimum CO2 stabilization.

Emission of particulate and gaseous pollutants from household laser processing machine

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Journal of Environmental Sciences 2021年第5期33卷 148-156页

作者： Hyun sik Ko Sang Bin Jeong Sooyeol Phyo Jiwon Lee Jae Hee jung Department of Mechanical Engineering Sejong UniversitySeoul 05006Republic of Korea Center for Environment Healthand Welfare ResearchKorea Institute of Science and Technology(KIST)Seoul 02792Republic of Korea Graduate School of Energy and Environment Korea UniversitySeoul 02841Republic of Korea Department o f Materials Science and Engineering Korea UniversitySeoul 02841Republic of Korea

Indoor air quality(IAQ) directly affects the health of occupants. Household manufacturing equipment(HME) used for hobbies or educational purposes is a new and unexplored source of air pollution. In this study, we evaluated the characteristics of particulate and gaseous pollutants produced by a household laser processing equipment(HLPE). Various target materials were tested using a commercial HLPE under various operating conditions of laser power and sheath air flow rate. The mode diameters of the emitted particles gradually decreased as laser power increased, while the particle number concentration(PNC) and particle emission rate(PER) increased. In addition, as the sheath air flow rate quadrupled from 10 to 40 L/min, the mode diameter of the emitted particles decreased by nearly 25%, but the effect on the PNC was insignificant. When the laser induced the target materials at 53 m W, the mode diameters of particles were 2.0 × 10^(4) particles/cm^(3). Particularly, analyses of sampled aerosols indicated that harmful substances such as sulfur and barium were present in particles emitted from leather. The carcinogenic gaseous pollutants such as acrylonitrile, acetaldehyde, 1,3-butadiene, benzene, and C 8 aromatics(ethylbenzene) were emitted from all target materials. In an actual indoor environment, the PNC of inhalable ultrafine particles(UFPs) was > 5 × 10^(4) particles/cm^(3) during 30 min of HLPE operation. Our results suggest that more meticulous control methods are needed, including the use of less harmful target materials along with filters or adsorbents that prevent emission of pollutants.

关键词： Indoor air quality(IAQ) Emission Laser processing Ultrafine particles(UFPs) Volatile organic compounds(VOCs)

Day-ahead electricity price forecasting using back propagation neural networks and weighted least square technique

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Frontiers in Energy 2016年第1期10卷 105-113页

作者： S. Surender REDDY chan-Mook jung Ko Jun SEOG Department of Railroad and Electrical Engineering Woosong University Daejeon 300718 Republic of Korea Department of Raikoad and Civil Engineering Woosong University Daejeon 300718 Republic of Korea Korea Rail Network Authority Daejeon 300718 Republic of Korea

This paper proposes the day-ahead electricity price forecasting using the artificial neural networks （ANN） and weighted least square （WLS） technique in the restructured electricity markets. Price forecasting is very important for online trading, e-commerce and power system operation. Forecasting the hourly locational marginal prices （LMP） in the electricity markets is a very important basis for the decision making in order to maximize the profits/benefits. The novel approach pro- posed in this paper for forecasting the electricity prices uses WLS technique and compares the results with the results obtained by using ANNs. To perform this price forecasting, the market knowledge is utilized to optimize the selection of input data for the electricity price forecasting tool. In this paper, price forecasting for Pennsylvania-New Jersey-Maryland （PJM） interconnec- tion is demonstrated using the ANNs and the proposed WLS technique. The data used for this price forecasting is obtained from the PJM website. The forecasting results obtained by both methods are compared, which shows the effectiveness of the proposed forecasting approach. From the simulation results, it can be observed that the accuracy of prediction has increased in both seasons using the proposed WLS technique. Another important advantage of the proposed WLS technique is that it is not an iterative method.

关键词： day-ahead electricity markets price forecast-ing load forecasting artificial neural networks load servingentities

Quantitative analysis of mechanical properties associated with aging treatment and microstructure in Mg-Al-Zn alloys through machine learning

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Journal of Materials Science & Technology 2022年第12期107卷 52-63页

作者： Joung sik Suh Byeong-chan Suh Sang Eun Lee Jun Ho Bae Byoung Gi Moon Advanced Metals Division Korea Institute of Materials ScienceChangwon 51508Republic of Korea

The present study proposes a methodology for predicting the mechanical properties of AZ61 and AZ91alloys associated with microstructure,texture and aging parameters and estimating predictor *** this,we investigate quantitative correlations between microstructure,texture and mechanical properties of aged AZ61 and AZ91 rods through machine *** regression analysis focuses on the precipitation behavior of Mg17Al12as the main second phase of Mg-Al-Zn alloys with respect to aging *** simplify data generation,only SEM images were used to quantify the features of discontinuous and continuous *** overcome the lack of data and make the most of the measured data,we devised a method to extend the existing dataset by a factor of 9 using the mean and standard deviation of the measured *** neural networks predicted tensile and compressive yield strengths and resultant yield asymmetry with a high accuracy of over 98%using 11 predictors for a total of *** tree learning quantitatively assessed the importance of predictors in determining the mechanical properties of aged AZ61 and AZ91 rods.

关键词： Magnesium alloy Aging treatment Microstructure Mechanical properties Machine learning

Value of controlled attenuation parameter in fibrosis prediction in nonalcoholic steatohepatitis

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World Journal of Gastroenterology 2019年第33期25卷 4959-4969页

作者： jung Il Lee Hyun Woong Lee Kwan sik Lee Department of Internal Medicine Gangnam Severance Hospital Yonsei University College of Medicine

BACKGROUND Liver stiffness measurement(LSM)tends to overestimate fibrosis stage in nonalcoholic fatty liver disease(NAFLD).Controlled attenuation parameter(CAP),provided by LSM device,has been introduced for noninvasive quantification of hepatic *** To determine the role of CAP values in predicting liver fibrosis stage by LSM in nonalcoholic steatohepatitis(NASH).METHODS One hundred eighty-four patients with biopsy proven NASH had LSM and CAP evaluated at *** them,130 patients had 1-year follow up LSM and analyzed for the changes of LSM after pioglitazone or ursodeoxycholic acid(UDCA)*** In Kleiner fibrosis stage F0-1,LSM values increased at higher CAP tertile(P=0.001),and in F2,at middle and higher tertiles(P=0.027).No difference across CAP tertiles was noticed in F3-4(P=0.752).Receiver operating characteristic curve for LSM cutoff in diagnosis of F≥2 identified 8.05 kPa for lower CAP tertile,9.35 kPa for middle,and 10.55 kPa for high *** changes in proportion of significant fibrosis(F≥2)were assessed among pioglitazone and UDCA treated patients considering CAP values,pioglitazone treated patients demonstrated decrease in proportion of high *** In patient with NAFLD,interpretation of LSM in association with CAP scores may provide helpful information sparing unnecessary liver biopsy.

关键词： Fibroscan Controlled attenuation parameter Liver stiffness Nonalcoholic steatohepatitis Liver fibrosis

Optimal operation of microgrid using hybrid differential evolution and harmony search algorithm

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Frontiers in Energy 2016年第3期10卷 355-362页

作者： S. SURENDER REDDY Jae Young PARK chan Mook jung Department of Railroad and Electrical Engineering Woosong University Republic of Korea Department of Railroad and Civil Engineering Woosong UniversityRepublic of Korea

This paper proposes the generation scheduling approach for a microgrid comprised of conventional generators, wind energy generators, solar photovoltaie （PV） systems, battery storage, and electric vehicles. The electrical vehicles （EVs） play two different roles： as load demands during charging, and as storage units to supply energy to remaining load demands in the MG when they are plugged into the microgrid （MG）. Wind and solar PV powers are intermittent in nature; hence by including the battery storage and EVs, the MG becomes more stable. Here, the total cost objective is minimized considering the cost of conventional generators, wind generators, solar PV systems and EVs. The proposed optimal scheduling problem is solved using the hybrid differential evolution and harmony search （hybrid DE-HS） algorithm including the wind energy generators and solar PV system along with the battery storage and EVs. Moreover, it requires the least investment.

关键词： battery storage electric vehicles (EVs),microgrid (MG) optimal scheduling solar photovoltaic(PV) system wind energy conversion system

Three-dimensional porous graphene-metal oxide composite microspheres： Preparation and application in Li-ion batteries

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Nano Research 2015年第5期8卷 1584-1594页

作者： Seung Ho Choi jung-Kul Lee Yun chan Kang Department of Materials Science and Engineering Korea University Anam-Dong Seongbuk-Gu Seou1136-713 Republic of Korea Department of Chemical Engineering Konkuk University 1 Hwayang-Dong Gwangjin-Gu Seou1143-701 Republic of Korea

The use of new three-dimensional （3D） porous graphene-metal oxide composite microspheres as an anode material for Li-ion batteries （LIBs） is first introduced here. 3D graphene microspheres are aggregates of individual hollow graphene nanospheres composed of graphene sheets. Metal oxide nanocrystals are uniformly distributed over the graphene surface of the microspheres. The 3D porous graphene-SnO2 microspheres are selected as the first target material for investigation because of their superior electrochemical properties. The 3D porous graphene-SnO2 and graphene microspheres and bare SnO2 powders deliver discharge capacities of 1,009, 196, and 52 mAh·g^-1, respectively, after 500 cycles at a current density of 2 A·g^-1 .The 3D porous graphene-SnO2 microspheres exhibit uniquely low charge transfer resistances and high Li-ion diffusivities before and after cycling.

关键词： graphene metal oxide nanostructures electrode material batteries