• 전력전자학회논문지
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• 제19권2호
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• pp.106-115
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• 2014

This paper proposes ESS DC-DC Converter using Redox Flow Battery (RFB) for stand-alone microgrid. Price, safety, expandability and dynamics are crucial in ESS. Reports show that Zinc-bromine (ZnBr) RFB is the best choice in ESS. Simple electrical ZnBr RFB model is obtained from charging test. DC-DC converter Inductor current-DClink Voltage model is proposed for the DC microgrid. For the controller design in z-domain, the K-factor method is by considering nature of the digital controller. The control performance has been verified with simulation and hardware experiments. Lastly 10kW DC microgrid using RFB test result is shown.

• Animal cells and systems
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• 제10권4호
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• pp.191-196
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• 2006

This study was carried out to evaluate soil carbon cycling of a 36-year-old larch (Larix leptolepis) stand in Korea. The aboveground and soil organic carbon storage, litterfall, and soil respiration rates were measured over twoyear periods. The estimated aboveground biomass carbon storage and increment were 4220 gC $m^{-2}$ and 150 gC $m^{-2}\;yr^{-1}$, respectively. Mean organic carbon inputs by needle and total litterfall were 118 gC $m^{-2}\;yr^{-1}$ and 168 gC $m^{-2}\;yr^{-1}$, respectively. The aboveground carbon increment of the stand was similar to the annual input of carbon from total litterfall. The soil respiration rates correlated exponentially with the soil temperature at a depth of 20 cm ($R^2$ = 0.86). In addition, the exponential regression equation indicated a relatively strong positive relationship between the soil respiration rates and soil temperature, while there was no significant relationship between the soil respiration rates and the soil moisture content. The annual mean and total soil respiration rates were 0.40 g $CO_2\;m^{-2} h^{-1}$ and 3010 g $CO_2\;m^{-2}\;yr^{-1}$ over the two-year study period, respectively.

• Journal of Ecology and Environment
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• 제29권1호
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• pp.23-27
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• 2006

This study was conducted to evaluate forest carbon cycling and soil $CO_2$ efflux rates in a 42-year-old pine (Pinus densiflora) stand located in Hamyang-gun, Korea. Aboveground and soil organic carbon storage, litterfall, litter decomposition, and soil $CO_2$ efflux rates were measured for one year. Estimated aboveground biomass carbon storage and increment in this stand were $3,250gC/m^2\;and\;156gC\;m^{-2}yr^{-1}$, respectively. Soil organic carbon storage at the depth of 30 cm was $10,260gC/m^2$ Mean organic carbon inputs by needle and total litterfall were $176gC\;m^{-2}yr^{-1}\;and\;235gC\;m^{-2}yr^{-1}$, respectively. Litter decomposition rates were faster in nne roots less than 2 mm diameter size ($<220\;g\;kg^{-1}yr^{-1}$) than in needle litter ($<120\;g\;kg^{-1}yr^{-1}$). Annual mean and total soil respiration rates were $0.37g\;CO_2m^{-2}h^{-1}$ and $2,732g\;CO_2m^{-2}yr^{-1}$ during the study period. A strong positive relationship existed between soil $CO_2$ efflux and soil temperature (r=0.8149), while soil $CO_2$ efflux responded negatively to soil pH (r=-0.3582).

• Journal of Ecology and Environment
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• 제29권6호
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• pp.531-537
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• 2006

본 연구는 월악산 국가장기생태연구지소를 중심으로 이 지역에서 다른 개체군에 비하여 상대적으로 광역 우점하는 소나무림, 굴참나무림, 그리고 신갈나무림 등 3개 주요 임분을 대상으로 그들의 종조성과 구조적 특성을 평가하였다. 종 및 개체수는 분포 경향은 흉고직경급이 증가할수록 감소하는 경향을 나타내었으며, 종 풍부성에 있어서 다양한 입지 적응 폭을 가지고 있는 신갈나무림이 다른 두 임분에 비하여 상대적으로 높게 나타남을 알 수 있었다. 천이 경향은 임분별로 천이 단계상 다소 차이가 있지만 장기적으로 보면 임분 유형에 관계없이 모두 신갈나무림으로 변화될 것으로 판단되었다. 각 임분의 우점종을 기준으로 생목과 사목의 개체 밀도 구성비를 보면 신갈나무림에서 신갈나무 개체 75:25, 굴참나무림에서 굴참나무 개체 94:6, 그리고 소나무림에서 소나무 86:14로 신갈나무림에서 개체 고사율이 가장 높고 굴참나무림이 가장 낮게 나타났다. 이것은 각 임분의 천이 단계의 차이에 따른 종간 및 종내 경쟁의 결과로 판단되었다. 한편, 임분별 구성 개체목의 건강 상태를 보면 임분유형에 관계없이 AS형이 75$\sim$85%로 가장 높게 나타났으며 DF형은 전혀 나타나지 않았다. 끝으로 본 연구를 위해 설치한 영구 방형구는 향후 정기적인 조사를 통하여 이 지역 산림 생태계 보전에 적합한 유용 정보를 제공하여 줄 수 있을 것이다.

• Journal of Ecology and Environment
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• 제30권4호
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• pp.347-356
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• 2007

The structure and dynamics of Korean red pine stands established in the riparian zone were studied in the Tsang stream in Mt. Seorak National Park, in east-central Korea. Pine stands were classified into four successional stages, the initial, establishing, competitive, and stabilizing stages, based on the age distribution of a dominant tree, Pinus densiflora, the vegetation stratification, and the microtopography of the riverine environment. The stages usually corresponded to disturbance frequencies, depending on the horizontal and vertical distances from the watercourse. Stands of the initial and establishing stages lacked tree or subtree layers, or both. As stands progressed through the developmental stages, soil particle size became finer and moisture retention capacity was improved. The stand ordination reflected the developmental stage, and the species ordination differentiated species specializing in relatively dry and wet habitats. The results of the analysis of vegetation dynamics provided ecological information which will be useful for understanding the developmental processes of vegetation established in riparian zones. Species diversity indices usually increased across developmental stages, following the typical pattern for successional processes. We discuss the importance and necessity of riparian vegetation in Korea, where most riparian forests have disappeared due to excessive human land use.

• 한국시스템다이내믹스연구
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• 제14권3호
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• pp.105-134
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• 2013

Electrical construction business has public and professional characters. It may require appropriate interventions of the government because these business activities stand for not only profit-seeking competition, but also supplies of one of the key functions in our society. In other words, public benefit and private benefit are still in existence. The government therefore considers such an aspect of public importance of the business sector and needs to plan to adjust technical and engineering manpower of this market. This study focuses on the imbalance for labor supply and demand of technical engineer in electrical construction business. A system dynamics analysis is applied to understand and simulate the imbalance as a soft approach. It has the merit of causal loop diagram to alleviate the limitation of data lack problem. We find that excess demand is expected from 2010 to 2011, and excess supply is predicted from 2012 to 2021 about the manpower of technical engineer. It shows considerable disagreement between the supply and demand of human resource. So we suggest that it is strong necessity to construct statistics infrastructure for a manpower supply and demand plan.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2013년도 춘계학술대회 논문집
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• pp.1515-1516
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• 2013

• 산업공학
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• 제13권3호
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• pp.328-338
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• 2000

This paper reviews the general concept and application area of Supply Chain Management (SCM). Then, the general concept, function, modeling methodology, and operation methodology of Supply Chain Simulation are also reviewed. SCM software solutions and their modules developed by popular IT companies are introduced and compared. The role of simulation in SCM is emphasized as a strategic decision making solution for modeling and analyzing dynamics of a supply chain. Several stand-alone supply chain simulators are introduced and compared.

• 한국산림과학회지
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• 제101권4호
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• pp.592-598
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• 2012

본 연구에서는 임분 수확 예측모델을 이용하여 우리나라 6개 주요 수종(강원지방소나무, 중부지방소나무, 잣나무, 낙엽송, 상수리나무, 신갈나무)에 대해 간벌 시업에 따른 임분의 생장변화와 수확량을 예측하였다. 간벌 시나리오를 설정하기 위해 15년에서 40년까지 5년 단위로 간벌시기를 구분하되 간벌주기는 10년 이상이 되도록 하였으며, 간벌에 의해 제거되는 전체 비율이 60%를 넘지 않도록 제한하였다. 이러한 제한조건을 적용하여 10가지 간벌 시나리오를 설정하고 수종별, 지위지수별 수확량을 비교 분석하였다. 연구결과 강원지방소나무, 잣나무, 신갈나무는 20년과 40년, 2회에 걸쳐 30% 강도로 간벌을 시행하는 것이 수확량이 가장 높았으며, 중부지방소나무, 낙엽송은 20년, 30년, 40년, 3회에 걸쳐 20% 강도로 간벌을 시행하는 것이 가장 수확량이 높았다. 상수리나무는 두 시나리오 모두 동일한 수확량을 보였다. 또한 간벌을 시행하는 것이 시행하지 않는 것보다 수확량의 증대를 가져오는 것으로 나타났으며, 지위지수가 높아짐에 따라 수확량 증대효과도 높아지는 것으로 분석되었다. 수종별로는 강원지방소나무(28%)와 낙엽송 임분(25%)에서 간벌로 인한 수확량 증대 효과가 높게 나타났으며, 잣나무(12%)는 상대적으로 효과가 낮았다. 본 연구에 이용된 임분 수확 예측모델은 간벌시업에 따른 임분의 생장변화를 예측하는데 매우 효과적이었으나, 수확표 자료를 토대로 함에 따라 현장적용성에 한계가 있을 수 있다. 따라서 간벌효과에 대한 실측 자료와 비교 검증하는 연구가 뒤따라야 할 것이다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권9호
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• pp.4379-4397
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• 2017

Three different improvements of the Velocity-based model were proposed in a minimal velocity-based pedestrian model. The improvements of the models are based on the different agent forms. The different representations of the agent lead to different results, in this paper, we simulated the pedestrian movements in some typical scenes by using different agent forms, and the agent forms included the circles with different radiuses, the ellipse and the multi-circle stand for one pedestrian. We have proposed a novel model of pedestrian dynamics to optimize the simulation. Our model specifies the pedestrian behavior using a dynamic ellipse, which is parameterized by their velocity and can improve the simulaton accuracy. We found a representation of the pedestrian much closer to the reality. The phenomena of the self-organization can be observable in the improved models.