• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.36.1-36.1
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• 2011

풍력개발 기술이 발전함에 따라 풍력발전시스템이 점차 대용량화되는 추세이며, 경제성 있는 풍력단지 건설을 위해 점차 대단지화 되어가고 있는 실정이다. 이로 인해 풍력 발전단가(Cost of electricity, COE)도 개선되고 있다. 풍황이 양호한 풍력발전단지의 경우, 풍력발전 COE는 현재 50~60원/kWh 수준으로 타 신재생에너지원에 비해 경쟁력이 높고, 석탄 화력의 COE와 비교해 봐도 동등한 수준 혹은 더욱 경쟁력 있는 수준으로 감소하였다. 풍력발전단지 조성을 위해서는 시스템의 효율과 고효율, 저비용의 풍력발전시스템을 풍황이 좋은 지역에 설치할 때 낮은 COE를 가지는 경제성 있는 발전단지가 가능하다. 동급 용량 풍력발전시스템을 같은 지역에서 설치하여 에너지생산량을 증대시키기 위해서는 블레이드 지름의 증가시켜 유량을 증가시키거나 타워의 높이를 증가시켜 풍속을 증가시키는 방안이 있다. 이 경우 블레이드 길이와 타워 높이 증가에 의한 시스템 비용의 증가가 발생하는데, 에너지생산량 증가에 의한 수익비용과 시스템 비용 증가에 의한 자본비용은 서로 반비례로 영향을 미친다. 이를 위해 최소의 COE의 최대의 순현재가치(Net Present Value, NPV)를 갖는 목적함수로 두고 블레이드의 최적 길이와 타워의 최적 높이를 선정하였다.

• Journal of Educational Research in Mathematics
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• v.27 no.4
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• pp.833-855
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• 2017

This study aims to reinvestigate the reason for introducing radian as a new unit to express the size of angles, what is the meaning of radian measures to use arc lengths as angle measures, and why is the domain of trigonometric functions expanded to real numbers for expressing general angles. For this purpose, it was conducted historical, mathematical and applied mathematical analyzes in order to research at multidisciplinary analysis of the radian concept. As a result, the following were revealed. First, radian measure is intrinsic essence in angle measure. The radian is itself, and theoretical absolute unit. The radian makes trigonometric functions as real functions. Second, radians should be aware of invariance through covariance of ratios and proportions in concentric circles. The orthogonality between cosine and sine gives a crucial inevitability to the radian. It should be aware that radian is the simplest standards for measuring the length of arcs by the length of radius. It can find the connection with sexadecimal method using the division strategy. Third, I revealed the necessity by distinction between angle and angle measure. It needs justification for omission of radians and multiplication relationship strategy between arc and radius. The didactical suggestions derived by these can reveal the usefulness and value of the radian concept and can contribute to the substantive teaching of radian measure.

• Journal of Korean Society of Forest Science
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• v.110 no.4
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• pp.665-677
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• 2021

This study analyzed the optimization method of forest management to enhance economic and public functions, as well as the interrelationship among timber production, carbon storage, and water conservation functions in Mt.Gari leading forest management zone. For these purposes, a forest management planning model was developed using Multi-Objective Linear Programming. The model had an objective function to maximize the total NPV (Net Present Value) of weighted timber production, carbon storage, water conservation, and constraints to limit the rate of change in timber production, percentage of each age-class and tree species area, percentage of conifers and broad-leaved trees area in each management zone, minimum timber production and timber sales amount. Based on the description of forest inventory and the comprehensive plan of Mt.Gari, we analyzed stand information and management constraints of the study area. We compared management alternatives using different weights in the objective function. Therefore, the total NPV was maximized in the alternative considering the three functions in equal proportion, rather than the alternatives of maximizing only one function. When all three functions were considered simultaneously, timber production offset the carbon storage and water conservation, and carbon storage and water conservation interacted synergistically. However, when considering only two of the three functions, all combinations of functions demonstrated tradeoffs with one other. Therefore, we discovered that by considering all three functions equally, rather than only one or two functions, the economic and public values of the study area can be maximized.

• Journal of Korean Society of Transportation
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• v.30 no.1
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• pp.135-147
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• 2012

The benefit of traffic information on variable message sign can be divided into two. At the public level, the benefit of ATIS is the travel time saving, which is not only induced from ATIS, but also mixed with that of ATMS. In the economic appraisal of ITS, the benefit of ATIS has so far been regarded as the derived benefit from ATMS. At the user level, the benefit of ATIS is reduced driver uncertainty through the forward traffic status information. User can benefit from the information on VMS and therefore may have the willingness to pay for it. Recently attempt to qualify the value of information on VMS was increased, but there was a danger of distorting or over-estimates of the ATIS benefit because the related studies didn't consider the time-dependent attributes of traffic information and provided the single value. Estimates of the time-varying value should be needed for a rigorous economic appraisal of ATIS. In this study, we varied the value of information on VMS according to peak and non peak trip and verified the hypothesis that time-varying of value was statistically significant.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.4
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• pp.47-55
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• 2009

This paper estimates interruption cost assessment for industrial load. For executing In this way first, we research customer interruption cost(CIC) for industrial load about 1,026 unit. And to assess industrial load in D/L calculate sector customer damage function(SCDF) using CIC. Second, we compute distribution reliability through annual failure rate, repair time and so on, and then, Third, distribution system that calculate VBDRA for industrial load per alternative assesses interruption cost.

• Journal of the Economic Geographical Society of Korea
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• v.10 no.4
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• pp.414-426
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• 2007

The purpose of this study is to analyze whether the spatial externalities of agglomeration economy of manufacturing has been changed or not, from 1991 to 2005. To find this spatial SUR model was used to consider covariance of each equation and it was estimated by 3SLS. This paper found that spatial externalities has been decreased and there is economy of scale in same sector. As a result, we can conclude that there is industrial specialization in region whereas interregional linkage are weaken. This finding supports the desirability of creating supra-regional agencies promoting interregional linkage because supra-regional agencies can internalize spatial externality of agglomeration economy.

• Environmental and Resource Economics Review
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• v.29 no.3
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• pp.335-362
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• 2020

Using the Hedonic pricing model using Box-Cox transformation, this paper estimated the marginal effect (implicit price) of odors from landfill in the metropolitan area on housing prices and the willingness to pay for changes in certain odor conditions. This paper utilized the proximity from the landfill in the metropolitan area as a environmental variable, and analyzed the effect of various housing characteristic variables on the sale price of apartments within a radius of 5 km from the landfill. In particular, because odors factor have various heterogeneity, we applied hedonic price models instead of stated-preference methods with various types of functional forms through Box-Cox transformation, considering the heterogeneity of each region. Estimates show that the marginal value (implicit price) for the distance from the odor source was 0.227 to 0.533 depending on the function type of the estimated model. In addition, when other house factors are the same, the marginal willingness to pay for a distance of 1km from the odor source was calculated to be 16.79 to 51.76 thousand dollar depending on the type of function. Finally for the general Box-Cox model, the annual WTP was estimated to be 3,229dollar.

• Journal of the Korean Wood Science and Technology
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• v.45 no.5
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• pp.629-639
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• 2017

Tripitaka Koreana in Haein Temple, Hapcheon Province is the most historical and largest heritage in this country, however the species of their blocks have yet been unknown. A nondestructive test method is necessary to investigate their species. The oven-dry density of wood was measured by inversely using the principle of high frequency moisture meter. The oven-dry densities of more than 100 domestic species of specimens estimated by measurement method and high frequency moisture meter were compared and following conclusions were obtained. There was highly close correlation between the oven-dry density estimated by measurement method and the oven-dry density estimated by high frequency moisture meter. The densities of Tripitaka Koreana that was a global cultural heritage could be correctly estimated by using high frequency moisture meter and the equilibrium moisture content under which Tripitaka Koreana equilibrated, thus, it was expected to provide the key to species identification.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2021.10a
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• pp.143-145
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• 2021

The Sihwa River was first planned to be a fresh water lake, but it failed due to serious environment pollution. During times of destruction and regeneration, changes of ecosystem of Sihwa River was visible, especially the algal ecosystem. It's because many seasonal birds pass through the place. This paper analyzes the changes of algal ecosystem of Sihwa River based on eight ecosystem indices. Moreover, using gradient descent, COD is expressed has a function of three ecosystem indices selected from above which is newly defined as SEI, Sihwa Ecosystem Index. In conclusion, we can observe the current ecosystem more easily without its actual data, but only with informations of the ecosystem.

• Korean Journal of Environment and Ecology
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• v.25 no.5
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• pp.787-798
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• 2011

An arboretum is defined as a collection of facilities that conserve plant species by surveying, collecting, and proliferating and preserving the plants in nature, perform diverse researches on plants and display the plants in exhibition spaces or outdoors as well as provide the public with educational programs and refreshment spaces according to the laws concerned. The public, however, recognizes the exhibition and education functions on plants of arboretum more importantly compared with the roles to survey, collect, and proliferate plants as regulated by the laws. In particular, arboretum plays a role to offer a pivotal educational place in urban area where the public can obtain an hands-on experience and understanding on a wide range of plant species and natural environment. The study aims to estimate the non market environmental values of Daegu Arboretum operated by Daegu Metropolitan City government by using the Contingent Valuation Methods (CVM), which yields the current monetary estimates for the arboretum. The value estimation was undertaken by using the Double-Bound Dichotomous Choice (DBDC) method, and each estimated value was derived from respective functions based on a logit distribution known to include relatively stable estimates according to the shape of the distribution. Considering the statistical fitness test results, the author estimated the amounts of the Willingness To Pay (WTP) such as mean WTP of 12,718 KRW, median WTP of 11,033 KRW, and truncated mean WTP of 11,468 KRW, which represented the annual recreational values per a person visiting Daegu Arboretum respectively. The analysis showed that Daegu Arboretum created the annual environmental values which were estimated to be approximately 16 to 19 billion KRW. The study also has an implication that the valuation method for the environment of Daegu Arboretum may be effectively applied for estimating the values of other types of environmental goods by altering the locations or goods to be analyzed.