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Ground Penetrating Radar Imaging of a Circular Patterned Ground near King Sejong Station, Antarctica
( Kwansoo Kim ),( Hyeontae Ju ),( Joohan Lee ),( Changhyun Chung ),( Hyoungkwon Kim ),( Sunjoong Lee ),( Jisoo Kim ) 대한지질공학회 2021 지질공학 Vol.31 No.3
Constraints on the structure and composition of the active layer are important for understanding permafrost evolution. Soil convection owing to repeated moisture-induced freeze-thaw cycles within the active layer promotes the formation of self-organized patterned ground. Here we present the results of ground penetrating radar (GPR) surveys across a selected sorted circle near King Sejong Station, Antarctica, to better delineate the active layer and its relation to the observed patterned ground structure. We acquire GPR data in both bistatic mode (common mid-points) for precise velocity constraints and monostatic mode (common-offset) for subsurface imaging. Reflections are derived from the active layer-permafrost boundary, organic layer-weathered soil boundary within the active layer, and frozen rock-fracture-filled ice boundary within the permafrost. The base of the imaged sorted circle possesses a convex-down shape in the central silty zone, which is typical for the pattern associated with convection-like soil motion within the active layer. The boundary between the central fine-silty domain and coarse-grained stone border is effectively identified in a radar amplitude contour at the assumed active layer depth, and is further examined in the frequency spectra of the near- and far-offset traces. The far-offset traces and the traces from the lower frequency components dominant on the far-offset traces would be associated with rapid absorption of higher frequency radiowave due to the voids in gravel-rich zone. The presented correlation strategies for analyzing very shallow, thin-layered GPR reflection data can potentially be applied to the various types of patterned ground, particularly for acquiring time-lapse imaging, when electric resistivity tomography is incorporated into the analysis.
Kwansoo Kim,Donghwan An,Kwangseok Chae 한국농업경제학회 2007 農業經濟硏究 Vol.48 No.4
This paper tests whether exogenous shocks including agricultural policies, trade liberalization and financial crisis have impacts on the structural changes in the farm or farm household income. Unlike previous studies that specify break points prior to the estimation of regression, this paper estimates break points by fitting time series models. Tests for the structural breaks show that there is no structural break in the real farm household income whereas real farm income has five break points. Especially the break at 1997 can be interpreted as the impacts of financial crisis. The break points of 1983, 1987 and 1992 approximately match with the timings of agricultural policies that aimed better structure of agriculture and rural area were implemented. The assessed impacts of exogenous shocks at 1970, 1983, 1987 and 1992 are all positive. However, the assessed impacted of the shock at 1997 is negative. The impacts of the shock at 1997 are assessed within the range between -1,141,432 won and -3,167,804 won.
Regional Concentration of Agricultural Production and Supply Variability
Kim, Kwansoo(김관수),Ha, Yonghyun(하용현),An, Donghwan(안동환) 한국지역개발학회 2018 韓國地域開發學會誌 Vol.30 No.2
이 논문에서는 기존의 집적경제(agglomeration economies) 효과에 대한 논의가 평균 생산 측면에만 국한되어 이루어져 왔다는 점에 착안하여, 생산의 지역집중이 생산의 변동성에 미치는 효과에 대한 실증 분석을 시도하였다. 이를 통해 생산성의 평균 효과에 국한된 집적경제의 논의를 분산(변동성) 효과로 확장할 수 있었다. 본 연구에서 활용된 이론적방법론은 변이계수 분해법이며, 이를 통하여 생산의 변동성을 순수 생산성 효과, 재배면적 효과, 그리고 이 두 가지의 교차효과 등 세 부분으로 분해하였다. 본 연구의 실증분석으로는 농업부문을 대상으로 하여 특정 농산물 생산의 지역 집중이 생산의 변동성에 미치는 영 향을 분석하였다. 본 연구는 배추, 고랭지배추, 무, 양파, 파, 마늘 등 6가지 품목의 지역별 생산량 및 재배면적 자료를 이용하여 생산의 변동성을 순수 생산성 효과, 재배면적 효과, 그리고 이 두 가지의 교차효과 등 세 부분으로 분해하였다. 분석결과, 총공급(총생산)의 변동성은 품목별로 유사한 변화 패턴을 보이는 반면, 생산 변동성의 요인은 품목에 따라 매우다른 양상을 보이는 것으로 나타났다. 특히 생산의 지역집중도가 증가할수록 순수 생산성 변화에 따른 생산의 변동성이 커지는 것으로 분석되었다. 이러한 결과는 농업생산의 경우 생산의 지역집중에 따라 변동성(위험)이 함께 증가할 수 있다는 것을 의미한다. 이에 따라,본 연구는 농업생산에는 지역집중에 따른 평균효과를 나타내는 집적경제적 측면이외에도 분산효과를 나타내는 집적불경제(agglomeration diseconomies)적 측면이 있음을 실증적으로 보였다는 점에서 시사하는 바가 크다고 할 수 있다.
( Kwansoo Kim ),( Donghwan An ),( Kwangseok Chae ) 한국농업경제학회 2007 KOREAN JOURNAL OF AGRICULTURAL ECONOMICS(KJAT) Vol.48 No.3
This paper tests whether exogenous shocks including agricultural policies, trade liberalization and financial crisis have impacts on the structural changes in the farm or farm household income. Unlike previous studies that specify break points prior to the estimation of regression, this paper estimates break points by fitting time series models. Tests for the structural breaks show that there is no structural break in the real farm household income whereas real farm income has five break points. Especially the break at 1997 can be interpreted as the impacts of financial crisis. The break points of 1983, 1987 and 1992 approximately match with the timings of agricultural policies that aimed better structure of agriculture and rural area were implemented. The assessed impacts of exogenous shocks at 1970, 1983, 1987 and 1992 are all positive. However, the assessed impacted of the shock at 1997 is negative. The impacts of the shock at 1997 are assessed within the range between -1,141,432 won and -3,167,804 won.
Development of a Time-Domain Simulation Tool for Offshore Wind Farms
Kim, Hyungyu,Kim, Kwansoo,Paek, Insu,Yoo, Neungsoo The Korean Institute of Power Electronics 2015 JOURNAL OF POWER ELECTRONICS Vol.15 No.4
A time-domain simulation tool to predict the dynamic power output of wind turbines in an offshore wind farm was developed in this study. A wind turbine model consisting of first or second order transfer functions of various wind turbine elements was combined with the Ainslie's eddy viscosity wake model to construct the simulation tool. The wind turbine model also includes an aerodynamic model that is a look up table of power and thrust coefficients with respect to the tip speed ratio and pitch angle of the wind turbine obtained by a commercial multi-body dynamics simulation tool. The wake model includes algorithms of superposition of multiple wakes and propagation based on Taylor's frozen turbulence assumption. Torque and pitch control algorithms were implemented in the simulation tool to perform max-Cp and power regulation control of the wind turbines. The simulation tool calculates wind speeds in the two-dimensional domain of the wind farm at the hub height of the wind turbines and yields power outputs from individual wind turbines. The NREL 5MW reference wind turbine was targeted as a wind turbine to obtain parameters for the simulation. To validate the simulation tool, a Danish offshore wind farm with 80 wind turbines was modelled and used to predict the power from the wind farm. A comparison of the prediction with the measured values available in literature showed that the results from the simulation program were fairly close to the measured results in literature except when the wind turbines are congruent with the wind direction.