• Title/Summary/Keyword: Thermal forcing

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The Modeling Aging Analysis due to Finite Eliment Method on Epoxy-Mica Composites (에폭시-마이카 복합재료의 FEM에 의한 MODELING 열화 해석)

  • Kim, Hee-Gon;Hyun, Jung-Seob;Kim, Hee-Dong;Jo, Han-Gu
    • Proceedings of the KIEE Conference
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    • 1996.07c
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    • pp.1710-1712
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    • 1996
  • This paper was practiced insulation failure test forcing to accelerate on frequency of 420 HZ. There was manufactured generator stator windings for 500MVA thermal plants and selected accelerating deterioration voltage of 5.5kV/mm for electrical aging. Moreover, so as to verification of this experiments, we carried out modeling analysis due to finite element method using to ANSYS5.0 program for common package and imitated multi-stress aging for analyzing electrical and mechanical stress distribution.

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Collaboration and Confucian Reflexivity in Local Energy Governance: The Case of Seoul's One Less Nuclear Power Plant Initiatives

  • Lee, Youhyun;Bae, Suho
    • Journal of Contemporary Eastern Asia
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    • v.18 no.1
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    • pp.153-174
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    • 2019
  • South Korea's energy policy has been historically established through an energy production structure that relies on thermal and nuclear power generation in relation to a centralized 'Hard Energy System'. However, climate change issues are forcing the transition to renewable energy, and it is crucial for local governments to enable this. This study analyses Seoul city's local energy governance, which is known as One Less Nuclear Power Plant Initiative, by applying the collaborative governance framework inspired by Ansell and Gash (2008) and the Reflexivity framework of Confucianism. It is considered that the local energy governance model of Seoul city can be used as a model by other local governments, and it will eventually lead to a decentralized energy system in this era of energy transition.

Numerical Experiment on the Variation of Atmospheric Circulation due to Wild Fire (산불 발화에 따른 하층 대기 순환장 변화에 관한 수치 실험)

  • Lee, Hwa-Woon;Tak, Sung-Hoon;Lee, Soon-Hwan
    • Journal of Environmental Science International
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    • v.22 no.2
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    • pp.173-185
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    • 2013
  • In order to clarify the impact of wildfire and its thermal forcing on atmospheric wind and temperature patterns, several numerical experiments were carried out using three dimensional atmospheric dynamic model WRF with wildfire parametrization module SFIRE. Since wind can accelerate fire spread speed, the moving speed of fireline is faster than its initial values, and the fireline tends to move the northeast, because of the wind direction and absolute vorticity conservation law associated with driving force induced by terrain. In comparison with non-fire case, the hydraulic jump that often occurs over downwind side of mountain became weak due to huge heat flux originated by surface wildfire and wind pattern over downwind side of mountain tends to vary asymmetrically with time passing. Therefore temporal variation of wind pattern should be catched to prevent the risk of widfire.

Decomposition of HFCs using Steam Plasma (스팀 플라즈마를 이용한 HFCs 분해특성)

  • Kim, Kwan-Tae;Kang, Hee Seok;Lee, Dae Hoon;Lee, Sung Jin
    • Journal of Korean Society for Atmospheric Environment
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    • v.29 no.1
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    • pp.27-37
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    • 2013
  • CFCs (Chlorofluorocarbons) and HCFCs (Hydrochlorofluorocarbons) that are chemically stable were proven to be a greenhouse gases that can destroy ozone layer. On the other hand, HFCs (Hydrofluorocarbons) was developed as an alternative refrigerant for them, but HFCs still have a relatively higher radiative forcing, resulting in a large Global Warming Potential (GWP) of 1,300. Current regulations prohibit production and use of these chemicals. In addition, obligatory removal of existing material is in progress. Methods for the decomposition of these material can be listed as thermal cracking, catalytic decomposition and plasma process. This study reports the development of low cost and high efficiency plasma scrubber. Stability of steam plasma generation and effect of plasma parameters such as frequency of power supply and reactor geometry have been investigated in the course of the development. Method for effective removal of by-product also has been investigated. In this study, elongated rotating arc was proven to be efficient in decomposition of HFCs above 99% and to be able to generate stable steam plasma with steam contents of about 20%.

Effect of Pile Driving on Three Layered Pipeline according to Soil Properties Variation (지반 물성값에 따른 항타 진동이 지중 삼중관에 미치는 거동 분석)

  • Yoo, Han-Kyu;Choi, Joung-Hyun;Won, Jong-Hwa;Kim, Moon-Kyum
    • Proceedings of the Korean Geotechical Society Conference
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    • 2010.03a
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    • pp.765-770
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    • 2010
  • In this study, the behavior of underground pipeline subjected to pile driving is examined using the verified finite element model based on the field experiment. Young's modules of surface soil is varied and elastic modulus of the other soil layer is fixed. The pile driving force model proposed by Mounir E. Mabsout in 1999 was used and it was functions of time and of force. The forcing function applied on this study considers the kinetic energy of ram located at 1.2m height with 7 tonf. The 3-layered pipeline is composed of steel(inner) pipe, PUR(Polyurethane Resin, filler) and HDPE(outer) pipe, and the length/diameter of main steel pipe is 20m/0.8m(O.D). It is used for district heating pipes in Korea. The results are expressed in terms of Von Mises stress, displacement, and vibration velocity for each soil condition. From the results of the analyses, PUR which is originally intended as a thermal insulation of inner pipe shows performance as a structural member which distributes external pressure.

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Study of the Method of Calculating Maximum Voltage for Flux-Weakening Operation of Interior Permanent Magnet Synchronous Motor (매입형 영구자석 동기전동기의 약계자 제어를 위한 최대전압 선정에 관한 연구)

  • Kim, Jang-Mok;Kim, Su-Yeol;Ryu, Ho-Seon;An, Yong Ho;Yoon, Gi Gab;Lim, Ik-Hun;Jun, Hyang-Sig
    • Journal of the Korean Society of Safety
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    • v.15 no.2
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    • pp.63-69
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    • 2000
  • The constraint conditions are the stator voltage and the stator current to operate the motor in the flux weakening region. The maximum current is limited by the inverter current rating and the machine thermal rating. Given DC link voltage to control the motor in the flux weakening the maximum voltage is determined by considering PWM strategy, dead time, voltage drop of the inverter switching device, and the margin of the voltage for current forcing. In this paper, the new method to determine the available maximum voltage is derived by the quantitative method and by considering the factors of the voltage drop. The proposed method to determine the maximum voltage is very useful to improve the stability of the motor system and to enlarge the speed operation region in the flux weakening operation. Therefore the utility of the maximum voltage is increased.

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A Numerical Study of The Motion of a Circular Cylinder Suspended in a Square Enclosure (사각 밀폐계 내 자연대류에 의한 원형 실린더의 운동 특성에 관한 수치적 연구)

  • Son, Seong-Wan;Jeong, Hea-Kown;Ha, Man-Yeong;Yoon, Hyun-Sik
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.22 no.11
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    • pp.727-734
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    • 2010
  • The present study numerically investigates the motion of a solid body suspended in the square enclosure with natural convection. A two-dimensional circular cylinder levitated thermally has been simulated by using thermal lattice Boltzmann method(TLBM) with the direct-forcing immersed boundary method. To deal with the ascending, falling or levitation of a circular cylinder in natural convection, the immersed boundary method is expanded and coupled with the TLBM. The circular cylinder is located at the bottom of a square enclosure with no restriction on the motion and freely migrates due to the Boussinesq approximation which is employed for the coupling between the flow and temperature fields. For different density ratio between the cylinder and the fluid, the motion characteristics of the circular cylinder for various Grashof numbers have been carried out. The Prandtl number is fixed as 0.7.

The Effect of Atmospheric Flow Field According to the Urban Roughness Parameter and the Future Development Plan on Urban Area (도심 실제 거칠기 적용과 장래 도심 개발계획에 따른 국지 기상장 변화 수치 모의)

  • Choi, Hyun-Jung;Lee, Hwa-Woon;Kim, Min-Jung
    • Journal of Environmental Science International
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    • v.19 no.6
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    • pp.703-714
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    • 2010
  • In this study, we analyzed the impact of orographic and thermal forcing on the atmospheric flow field over the urban metropolitan areas on urban artificial buildings and future development plan. Several numerical experiments have been undertaken in order to clarify the impacts of the future development plan on urban area by analyzing practical urban ground conditions, we revealed that there were large differences in the meteorological differences in each case. The prognostic meteorological fields over complex areas of Seoul, Korea are generated by the PSU/NCAR mesoscale model(MM5). we carried out a comparative examination on the meteorological fields of topography and land-use that had building information and future development plan. A higher wind speed at daytimes tends to be forecasted when using new topography and land use data that have a high resolution with an appropriate limitation to the mixing height and the nocturnal boundary layer(NCB). During nighttime periods, since radiation cooling development is stronger after development plan, the decreased wind speed is often generated.

A Numerical Study on the Formation Mechanism of a Mesoscale Low during East-Asia Winter Monsoon

  • Koo, Hyun-Suk;Kim, Hae-Dong;Kang, Sung-Dae;Shin, Dong-Wook
    • Journal of the Korean earth science society
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    • v.28 no.5
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    • pp.613-619
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    • 2007
  • Mesoscale low is often observed over the downstream region of the East Sea (or, northwest coast off the Japan Islands) during East-Asia winter monsoon. The low system causes a heavy snowfall at the region. A series of numerical experiments were conducted with the aid of a regional model (MM5 ver. 3.5) to examine the formation mechanism of the mesoscale low. The following results were obtained: 1) A well-developed mesoscale low was simulated by the regional model under real topography, NCEP reanalysis, and OISST; 2) The mesoscale low was simulated under a zonally averaged SST without topography. This implies that the meridional gradient of SST is the main factor in the formation of a mesoscale low; 3) A thermal contrast ($>10^{\circ}C$) of land-sea and topography-induced disturbance served as the second important factor for the formation; 4) Paektu Mountain caused the surface wind to decelerate downstream, which created a more favorable environment for thermodynamic modification than that was found in a flat topography; and 5) The types of cumulus parameterizations did not affect the development of the mesoscale low.

A Coupled Three-Dimensional Hydrodynamic and Water Quality Modeling of Yongdam Reservoir using ELCOM-CAEDYM (ELCOM-CAEDYM을 이용한 용담호 3차원 수리-수질 연동 모델링)

  • Chung, Se Woong;Lee, Jung Hyun;Ryu, In Gu
    • Journal of Korean Society on Water Environment
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    • v.27 no.4
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    • pp.413-424
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    • 2011
  • The study was aimed to evaluate the applicability of a three-dimensional (3D) hydrodynamic and water quality model, ELCOM-CAEDYM for Yongdam Reservoir, Korea. The model was applied for the simulations of hydrodynamics, thermal stratification processes, stream density flow propagation, and water quality parameters including dissolved oxygen, nutrients, organic materials, and algal biomass (chl-a) for the period of June to December, 2006. The field data observed at four monitoring stations (ST1~ST4) within the reservoir were used to validate the models performance. The model showed reasonable performance nevertheless low frequency boundary forcing data were provided, and well replicated the physical, chemical, and biological processes of the system. Simulated spatial and temporal variations of water temperature, nutrients, and chl-a concentrations were moderately consistent with the field observations. In particular, the model rationally reproduced the succession of different algal species; i.e., diatom dominant during spring and early summer, after then cyanobacteria dominant under warm and stratified conditions. ELCOM-CAEDYM is recommendable as a suitable coupled 3D hydrodynamic and water quality model that can be effectively used for the advanced water quality management of large stratified reservoirs in Korea.