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정광섭,곽신영,최인길,임승현,Jung, Kwangsub,Kwag, Shinyoung,Choi, In-Kil,Eem, Seunghyun 한국지진공학회 2020 한국지진공학회논문집 Vol.24 No.2
Seismic responses due to the dynamic coupling between a primary structure and secondary system connected to a structure are analyzed in this study. The seismic responses are compared based on dynamic coupling criteria and according to the error level in the natural frequency, with the recent criteria being reliant on the error level in the spectral displacement response. The acceleration responses and relative displacement responses of a primary structure and a secondary system for a coupled model and two different decoupled models of two degrees-of-freedom system are calculated by means of the time integration method. Errors in seismic responses of the uncoupled models are reduced with the recent criteria. As the natural frequency of the secondary system increases, error in the natural frequency decreases, but seismic responses of uncoupled models can be underestimated compared to that of coupled model. Results in this paper can help determine dynamic coupling and predict uncoupled models' response conservatism.
법적 시각에서 SSM(Super Supermarket) 규제에 관한 연구
정광섭(Jung Kwangsub) 한국공공사회학회 2015 공공사회연구 Vol.5 No.1
작은 골목 상권조차 기존의 소상인들 사이를 파고드는 기업형 유통업체(SSM)에 대한 법적인 제재만이 해결책이 아닌 중소 업체와 대형 업체가 함께 윈윈(win-win)할 수 있는 경쟁에 관한 방법을 생각해 보고자 한다. 신규 기업(SSM)이 기존 기업에 이윤을 분배하는 조건으로 시장에 진입한다면 이는 기존 기업(중소 상인)에 어떤 영향을 미칠 것인가? 직관적으로 진입 기업의 이윤 분배가 반드시 기존 기업에 이득이 되는지는 알 수 없다. 진입에 따라 달라지는 시장 점유율과 균형 가격을 함께 살펴야 하는데 이는 이윤 분배의 정도에 따라 또 다르게 변하기 때문이다. 따라서 자유시장 경제원리 상 경쟁을 최대한 보장하고, 국가의 중소기업 보호원리를 적극적으로 수용하여 대형유통점과 중소유통점의 공존·상생 방안을 모색해보아야 한다. 이와 같이 SSM 규제 법률에 대한 다양한 시각이 존재하는 가운데 SSM규제 법률이 WTO의 서비스무역일반협정 상 금지하고 있는 경제적 수요심사에 해당할 가능성과 유통 선진국들의 유통 산업 발전을 위해 모색했던 방안들을 면밀히 검토하여 앞으로의 발전방향을 수립해야 할 것이다. Currently, the entrance of SSM causes many troubles with the small and mid-sized merchants in the market. This paper gropes for the win-win strategy that SSMand an incumbent merchant coexists, based on fair competition. How the existing small merchants are affected when SSM enters the market on the condition that it shares its profits with them? It could be difficult to intuitively know whether the entry of SSM with profit-sharing policy can be beneficial to the incumbent merchant. This is mainly because the market share and equilibrium price, which should be considered as one, are affected and varied by the level of profit-sharing. This research analyzes how the price, profit and quality of products and consumer surplus are influenced by the entrance of SSM, using Hoteling model. We suggested that profit-sharing of SSM would have a positive influence on incumbent merchants, while it could reduce the surplus of consumer. The various perspectives on SSM regulatory laws exist. Based on this result, we could find the political implications, even though this analysis requires excessive restrictions for applying to the real world.
분자동역학 전산모사를 이용한 반도체 나노와이어의 열기계적 거동 해석
정광섭(Kwangsub Jung),Min Zhou,조맹효(Maenghyo Cho) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
In [0001]-oriented GaN nanowires, initial wurtzite phase transforms to a tetragonal structure under uniaxial tensile loading. Molecular dynamics simulations are carried out to investigate thermomechanical behavior of the nanowire. Thermal conductivity in the nanowire is calculated at each state of the nanowire by using an equilibrium MD method, Green-Kubo approach. As strain increases, thermal conductivities decrease, except for nanowire with small diameter at high temperature, which has fully transformed structure on its surfaces after the phase transformation. Dominant effect on thermal conductivity changing is the structure on surfaces of nanowire, which alters the surface scattering behavior of phonons.
순환적으로 결합되는 정온기들을 갖는 NoT 분자동역학 전산모사에 관한 연구
정광섭(Kwangsub Jung),조맹효(Maenghyo Cho) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5
The recursive multiple thermostat chained fully flexible cell (RMT-NσT) molecular dynamics method has been proposed for isothermal-isobaric simulation by combining RMT Nose-Poincare and Parrinello-Rahman method. The RMT method is known to have advantages in achieving the ergodicity required for canonical sampling of the harmonic oscillator. In this article, we examine the ergodicity for various parameters of RMT-NσT using a practical nano structures of different numbers of copper atoms (864~13,500 atoms) in different environments. Through the numerical simulations, we conclude that RMT-NσT method has advantage in the cases of lower temperature.
정광섭(Kwangsub Jung),조맹효(Maenghyo Cho) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.11
Single crystalline copper nanowires are subjected to bending tests using molecular dynamics simulations and the embedded atom method. To observe behaviors of nanowire, bending tests are performed for various rates of deflection and different boundary conditions: fixed-free and fixed-fixed. When the deflection of nanowire becomes large, twinnings and dislocations appear, and 〈100〉 crystal structure transforms to 〈110〉. At high rates, phase transformation occurs in whole nanowire. But, at low rates, atomic structure changes to 〈110〉 phase partially. The final deformed structures are affected by the rate of deflection and boundary conditions. These effects can be important design parameters at nanoscale.
순환적으로 결합되는 정온기들을 갖는 NσT 분자동역학 전산모사에 적용한 외연적 적분기법
정광섭(Kwangsub Jung),조맹효(Maenghyo Cho) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5
In the previous development of the recursive thermostat chained fully flexible cell molecular dynamics simulation, implicit time integration method such as generalized leapfrog integration is used. The implicit algorithm is very much complicated and not easy to show time reversibility because it is solved by the nonlinear iterative procedure. Thus we develop simple, explicit symplectic time integration formula for the recursive thermostat chained fully flexible unit cell simulation. Uniaxial tension test is performed to verify the present explicit algorithm. We check that the present simulation satisfies the ergodic hypothesis for various values of fictitious mass and coefficient of multiple thermostat system. The proposed method should be helpful to predict mechanical and thermal behavior of nano-scale structure.
최진복(Jinbok Choi),정광섭(Kwangsub Jung),조맹효(Maenghyo Cho) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5
The classical continuum theory-based thin film model is independent of their size and the surface effect can be ignored. But the surface to bulk ratio becomes very large in nano-size structures such as nano film, nano wire and nano beam. In this case, surface effect plays an important role and its contribution of the surface effect must be considered. Molecular dynamics simulation has been a conventional way to analyze these ultra-thin structures but structures in the range between submicro and micro are difficult to analyze by classical molecular dynamics due to the restriction of computing resources and time. Therefore, in present study, the continuum-based method is considered to predict the overall physical and mechanical properties of the structures in nano-scale, especially, for the thin-film. The proposed continuum based-thin plate finite element is efficient and reliable for the prediction of nano-scale film behavior.
이상진(Sangjin Lee),정광섭(Kwangsub Jung),이종민(Jongmin Lee) 대한기계학회 2014 대한기계학회 춘추학술대회 Vol.2014 No.11
The structural integrity of the pool door for the research reactor is analyzed by using the finite element model. The pool door should withstand the external loads and maintain its structural integrity during the seismic event. The modal analysis and seismic analysis are carried out to evaluate the structural integrity. Fluid-structure interaction is also considered to reflect hydrostatic and hydrodynamic loads because the pool door is installed in water. Different dimension and boundary conditions for the pool door are used in these analyses.