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Nanostructure controlled MoS2 anode material for sustainable sodium ion batteries
정종엽,박종혁 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.1
Inspired by the success of graphite anodes in lithium-ion batteries, anode materials capable of inserting sodium ions within the layer structure are considered to provide stable and reversible electrochemical Na<sup>+</sup> storage for sodium-ion battery applications. Among various anode materials for sodium-ion batteries, MoS<sub>2</sub> attracted attention due to its layer structure and insertion properties. Here, we present MoS<sub>2</sub> grown vertically on nitrogen reduced graphene oxide (N-RGO) with sheet density and controlled sheet density and MoS<sub>2</sub> sheet height as a negative electrode active material for sodium-ion batteries. By adjusting the nucleation and growth process, we control the height and density of the MoS<sub>2</sub> sheet. High sheet density can prevent additional SEI layers, and the shortened sheet length of MoS<sub>2</sub> reduces the resistance of Na<sup>+</sup> diffusion. Growth of MoS<sub>2</sub> sheets on N-RGO was observed by scanning electron microscopy and high resolution transmission electron microscopy.
정종엽,Sunil Nijhawan 한국압력기기공학회 2023 한국압력기기공학회 논문집 Vol.19 No.1
Pressure tubes are the main components of PHWR core and serve as the pressure boundary of the primary heat transport system. However, because pressure tubes have changed their geometrical dimensions under the severe operating conditions of high temperature, high pressure and neutron irradiation according to the increase of operation time, all dimensional changes should be predicted to ensure that dimensions remain within the allowable design ranges during the operation. Among the deformations, the diameter expansion due to creep leads to the increase of bypass flow which may not contribute to the fuel cooling, the decrease of critical channel power and finally the deration of the power to maintain the operational safety margin. This study is focused on the modeling of the expansion of the pressure tube diameter based on the operating conditions and measured diameter data. The pressure tube diameter expansion was modeled using the neutron flux and temperature distributions of each fuel channel and each fuel bundle as well as the measured diameter data. Although the basic concept of the current modeling approach is simple, the diameter prediction results using the developed methodology showed very good agreement with the real data, compared to the existing methodology.
정종엽,임용택,Jeong, Jong-Yeop,Im, Yong-Taek 대한기계학회 2000 大韓機械學會論文集A Vol.24 No.11
Thickness control of hot-rolled strips has become an important issue in recent years because of the need for improving the quality of the hot-rolled strip. In this study, a modifying method of rolling force set-up with consideration of spread was developed to improve the thickness uniformity at the finishing rolling units in hot rolling. Through the analysis of real production data it was found that the accuracy of the rolling force determined from the finishing mill set-up (FSU) model dominantly governed the thickness uniformity in rolled plates at the front. Based on this analysis , several examples were selected to calculate the spread of rolled plate using three dimensional rigid thermo-viscoplastic finite element program. FE analysis results were used to train the neural network system that can predict the spread hot-rolled plate and the rolling force was modified based on the predicted value of spread. The modified rolling forces were closer to the measured rolling force so it can be expected that the accuracy of thickness uniformity of hot-rolled plate will be improved.
정종엽,임용택,진철제,이해영 대한기계학회 1994 대한기계학회논문집 Vol.18 No.2
In this study, a fuzzy theory is introduced to control the cross-sectional strip shape in cold rolling. A fuzzy controller is developed based on the production data and the operational knowledge. The cold rolled products are characterized into several types based on their irregularities. For each type of irregular strip shape, fuzzy controller calculates the changes of bender forces of work and intermediate rolls using fuzzy control algorithm. To simulate the continuous shape control, fuzzy controller is linked with emulator which is developed using neural network. The developed fuzzy controller and emulator simulate the cold rolling process until the irregularities converge to the tolerable range to produce unifrom cross-sectional strip shape. The results from this simulation are reasonable for various irregular strip shapes.
정종엽,임용택,Jung, Jong-Yeob,Im, Yong-Taek 대한기계학회 1996 大韓機械學會論文集A Vol.20 No.3
In this study, a fuzzy control algorithm was developed for the randomly irregular shape of cold-rolled strip. Currently developed fuzzy control algorithm consists of two parts: the first part calculates the changes of work and intermediate roll bender forces based on the symmetric part of the irregular strip shape, and the second part calculates the weighting factors based on the asymmetric part and modifies the pre-determined roll bender forces according to the weighting factors. As a result of this, bender froces applied at the both sides of the cold-rolled strip were different. In order to simulate the continuous shape control. fuzzy controller developed was linked with emulator which was developed based on neural network. The fuzzy controller and emulator developed simulated the cold rolling process until irregular shape converged to a tolerable range in producing uniform cross-sectional strip shape. The results obtained from the simulation were reasonable for various irregular strip shapes.
300-400℃에서 시효 처리된 Zr-2.5%Nb CANDU 압력관 재료에서 중성자 회절을 이용한 dimensional change 분석
정종엽,김형섭,김성수,김영석 대한금속·재료학회 2022 대한금속·재료학회지 Vol.60 No.5
The primary boundary of the CANDU reactor consists of Zr-2.5%Nb alloy pressure tubes and SA106 alloy feeder pipes. The pressure tubes are exposed to fast neutron (E>1Mev) irradiation during reactor operation, and experience dimensional changes. The actual dimensional change in the pressure tube during in-service operation is greater than the design estimate. It is not fully understood what is responsible for the dimensional changes in the pressure tubes. In this study, to accelerate the aging effect on the pressure tube material, aging was performed at 300-400°C for up to 20,000 hours and neutron diffraction was used to track variation in lattice spacing, thereby identifying the reason for the dimensional change. The analysis result showed that α-Zr, the main phase of Zr-2.5%Nb, had little dimensional change at 350°C or lower. On the other hand, the aging treatment at 400°C resulted in anisotropic expansion in the α-Zr of the HCP crystal, of 0.02% and 0.08% in the (1010) and (0002) directions, respectively. It was confirmed that above 350oC the β-phase in the Zr-2.5%Nb alloy was decomposed to precipitate β-Nb . The driving force of the lattice expansion may be due to the diffusing out tendency of the super saturated Nb in α-Zr and due to the residual cold working effect applied during the manufacturing process. The enhancing effects of fast neutron irradiation on lattice diffusion are discussed in detail.