• Journal of Biosystems Engineering
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• v.41 no.4
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• pp.313-318
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• 2016

Purpose: This study measured and analyzed the PTO (power take off) torque of a transplanter according to the planting conditions during field operation. Methods: A torque measurement system was constructed with torque sensors to measure the torque of a PTO shaft, a measurement device to acquire sensor signals, and a power controller to provide power for a laptop computer. The field operation was conducted at four planting distances (26, 35, 43, and 80 cm) and two planting depths using the transplanter on a field with similar soil conditions. One-way ANOVA with planting distance and Duncan's multiple range test at a significance level of 0.05 were used to analyze the PTO torque. The torque ratio was calculated based on the minimum torque using the average PTO torque measured under each planting condition. Results: The average torques on the PTO shaft for planting distances of 26, 35, 43, and 80 cm at a low planting depth were 11.05, 9.07, 7.04, and 3.75 Nm, respectively; the same for planting distances of 26, 35, 43, and 80 cm at a middle planting depth were 12.20, 9.86, 7.94, and 4.32 Nm, respectively. When the planting distance decreased by 43, 35, and 26 cm, the torque ratio at a low planting depth increased by 88, 142, and 195%, respectively. When the planting distance decreased by 43, 35, and 26 cm, the torque ratio at the middle planting depth increased by 84, 128, and 182%, respectively. Conclusions: PTO torque fluctuated by planting distance and depth. Moreover, the PTO torque increased for short planting distances. Therefore, farmers should determine the planting conditions of the transplanter by considering the load and durability of the machine. The results of this study provide useful information pertaining to the optimum PTO design of the transplanter considering the field load.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.8 no.2
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• pp.91-97
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• 2010

As nuclear power plants are getting older, interests on a decontaminating process are increasingly attracting more attention. Chemical decontamination is crucial to lower the production of radioactive waste and radiation dose rate. Prior to this, oxidizers and detergents for target material should be chosen so as to decontaminate major systems and components of a nuclear power plant chemically. In order to decontaminate it properly, it is crucial to have information about the chemical composition and crystalline structure of CRUD, analyzing its samples from the target or the decontamination system with components. However, there is no program which enables the extraction of samples directly from the object or the decontamination system with components carrying genuine radioactivity. Therefore, it is limited to samples from corrosion products carrying partial radioactivity as a resource. The composition of CRUD varies considerably depending on refueling cycle because it is closely related to the constituent of basic material. After settling a target, it is crucial to analyze and obtain analytical information about CRUD as a decontamination target. In this paper, various technologies for manufacturing simulated CRUD are introduced as alternatives to unattained samples. A metal oxide or metal hydroxide was used to synthesize simulated cruds having chemical compositions and crystalline stricture similar to the actual one by 12 different methods. CRUD 4(metal oxides in the autoclave vessel) and CRUD 10(metal oxides in a crucible after hydrazing pretreatment)were chosen as the best method for Type 1 and Type 2.respectively. As these CRUD can be synthesized easily without using any specialized equipment or reagents in a short time and in large quantities, they are expected to stimulate the development of decontaminating agents and processes.

• Ocean and Polar Research
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• v.40 no.4
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• pp.237-247
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• 2018

This study aims to estimate optimal harvests, fishing efforts, and stock levels of hairtail harvested by the large pair bottom trawl, the large otter trawl, the large purse seine, the offshore long line, and the offshore angling fisheries by using the surplus production models and the current value Hamiltonian method. Processes of this study are as follows. First of all, this study estimates the standardized fishing efforts regarding the harvesting of the hairtail by the above five fishing gears based on the general linear model developed by Gavaris. Secondly, this study estimates environmental carrying capacity (k), intrinsic growth rate (r), and catchability coefficient (q) by applying the Clarke Yoshimoto Pooley (CY&P) model among various surplus production models. Thirdly, this study estimates the optimal harvests, fishing efforts, and stock levels regarding the hairtail by the current value Hamiltonian method, including the average landing price, the average unit cost, and the social discount rate. Finally, this study attempts a sensitivity analysis to figure out changes in optimal harvests, fishing efforts, and stock levels due to changes in the average landing price and the average unit cost. As results induced by the current value Hamiltonian method, the optimal harvests, fishing efforts, and stock levels regarding the hairtail caught by several fishing gears were estimated as 33,133 tons, 901,080 horse power, and 79,877 tons, respectively. In addition, from the results of the sensitivity analysis, first of all, if the average landing price of the hairtail constantly increases, the optimal harvests of it increase at a decreasing rate, and then harvests finally slightly decrease as a result of decreases in stock levels. Secondly, if the average unit cost of fishing efforts continuously increases, the optimal fishing efforts decreases, but optimal stock levels increase. Optimal harvests start climbing and then decrease continuously due to increases in the average unit cost. In summary, this study suggests that the optimal harvests (33,133 tons) were larger than actual harvests (25,133 tons), but the optimal fishing efforts (901,080 horse power) were much less than estimated standardized fishing efforts (1,277,284 horse power), corresponding to the average of the recent three years (2014-2016). This result implies that the hairtail has been inefficiently harvested and recently overfished due to excessive fishing efforts. Efficient management and conservation policies on stock levels need to be urgently implemented. Some appropriate strategies would be to include the hairtail in the Korean TAC species or to extend the closed fishing season for this species.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.94-94
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• 2020

최근 정부의 신북방정책 추진에 따라 수자원분야에서는 동북아지역 국제 공유하천을 중심의 물 정보 및 연구협력 기회 확보와 지정학적 특성을 고려한 지역 현안해결 중심의 연구가 재조명 되고 있다. 두만강은 이러한 동북아의 중심에 위치하고 있으며, 중국, 북한, 러이사의 국경을 따라 흐르며 지역 수자원의 대부분을 공급하는 국제하천이다. 또한, 지난 2018년 5월에는 하구유역이 람사르(Ramsar) 습지로 승인됨에 따라 철새 등을 포함한 생태가치의 중요성도 크게 증가하였다. 하지만 이 지역은 유역의 지정학적 민감성과 접근이 제한된 관측 정보들로 인해 그 수자원·환경 효용성을 정확하게 파악할 수 없을 뿐만 아니라, 최근 기후변화에 따른 영향으로 홍수, 가뭄 등의 수재해와 수질오염 등의 문제가 발생하고 있어 가용한 기술기반의 직·간접적 접근을 통한 장기수문 및 환경변화 등에 대한 분석과 관리방안 수립 등의 연구가 필요하다. 본 연구에서는 이러한 미계측 두만강 유역을 대상으로 우선, 가용한 위성자료 및 광역지표모형(MERRA-2) 기반 NASA POWER(Prediction of Worldwide Energy Resource) 수문기상 자료와 SWAT(Soil and Water Assessment Tool) 모형을 활용하여 장기 수문영향을 평가하고자 한다. SWAT 모형은 전 지구적으로 활용 가능한 격자 해상도 약 30m의 위성기반 수치표고모형(DEM), 광역 토양도, 지역 토지이용도 자료를 활용하여 두만강 유역을 전체 19개 소유역 및 18개 하도, 138개 HRUs의 수문분석 단위로 구축하였으며, 모의는 미국 NOAA NCDC(National Climate Data Center) 및 중국 CMDC(China Meteorological Data Service Center)의 주요 관측지점에서 선별한 총 13개소의 위치에 대해 재분석된 기후/기상자료들(NASA POWER 강수, 기온, 풍속, 상대습도 및 일사량)을 적용, 1990년에서 2019년까지의 30개년도 연속자료를 구축활용 하였다. 한편, 모형의 검·보정은 앞서 언급한 관측 자료의 부재로 과거 문헌 등을 통해 파악할 수 있는 연 단위 수자원 총량 등을 활용해 진행코자한다. 아울러, 향후는 최근 활용 가능한 장기 위성관측 강수량을 적용, 재분석 자료 결과와의 비교를 통해 상호 분석 오류를 줄여나갈 수 있을 것으로도 판단된다.

• The Journal of Bigdata
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• v.8 no.2
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• pp.165-175
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• 2023

LNG is a representative imported cargo at Incheon Port and has a relatively high contribution to the increase/decrease in overall cargo volume at Incheon Port. In addition, in the view point of nationwide, LNG is the one of the most important key resource to supply the gas and generate electricity. Thus, it is very essential to identify the factors that have impact on the demand fluctuation and build the appropriate forecasting model, which present the basic information to make balance between supply and demand of LNG and establish the plan for power generation. In this study, different to previous research based on macroscopic annual data, the weekly demand of LNG is converted from the cargo volume unloaded by LNG carriers. We have identified the periodicity and correlations among internal and external factors of demand variability. We have identified the input factors for predicting the LNG demand such as seasonality of weekly cargo volume, the peak power demand, and the reserved capacity of power supply. In addition, in order to predict LNG demand, considering the characteristics of the data, time series prediction with weekly LNG cargo volume as a dependent variable and prediction through an artificial neural network model were made, the suitability of the predictions was verified, and the optimal model was established through error comparison between performance and estimates.

• Environmental and Resource Economics Review
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• v.12 no.4
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• pp.637-661
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• 2003

This paper analyzes the impact of import liberalization of petroleum product market in 1997 on the behavior of a domestic industry, regarded as a typical oligopoly. Based on the theory of implicit cartel, two regression equations were formulated and estimated for domestic production and refinery margin using monthly data for the period from Jan. 1994 to June 2003. Estimation results show that not only did domestic production rise sharply but also the refining cost fell substantially throughout 1996 before the actual liberalization of imports, Such a response is clearly consistent with the implicit cartel theory, which suggests that once the difficulty of maintaining a cartel in the future is recognized, the cartel immediately collapses and anticipation of import liberalization can cause immediately lowering market price as well as an immediate expansion of the supply by a domestic industry. However, the significant reduction of refinery cost accompanied by a large contraction in domestic output after the actual implementation of import liberalization can be explained by the collapse of implicit cartel caused by the anticipated liberalization of imports. Thus, import liberalization in the sense of allowing entry of foreign producers into domestic market has seemed to be an effective means to weaken market power and induce more competitive conduct of domestic firms.

• Environmental and Resource Economics Review
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• v.24 no.2
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• pp.311-342
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• 2015

We evaluate two main rationales of massive policy intervention of Lee Administration in the Korean transportation fuel market: high market share of domestic refineries, perceived by the Administration as the result of high market concentration, and asymmetry in price adjustment, perceived as the result of collusion. Domestic refineries, huge in capacity and located at seaports, maintain international competitiveness in price. Considering market openness offering preferential treatment to importers, they set domestic prices competitively on the basis of MOPS prices. Yet, the price competitiveness of domestic refineries is so high that they are able to sustain high market share. We confirm that the Korean before-tax consumer prices of gasoline and diesel are lower than Japan's and the weighted averages of 27 EU countries by as much as 159KRW and 21KRW per liter in the case of gasoline and 170KRW and 63KRW in the case of diesel. Price asymmetry is caused by diverse economic and managerial reasons and, as FTC (2005) states, price asymmetry does not immediately imply exercise of market power or collusion. We analyzed price asymmetry in Korea, Japan and 14 EU countries, and found asymmetry in Korea and 11 EU countries in the case of gasoline and in Korea and 8 EU countries in the case of diesel.

• Environmental and Resource Economics Review
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• v.13 no.2
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• pp.271-300
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• 2004

We investigate the two recent simulations of the proto-type domestic carbon emission trading system in Korea and draw some policy implications. The first simulation includes the 5 electric power companies based on baseline and credit. But the second one is with the 7 energy-intensive companies based on cap and trade. The voluntary approaches in this paper revealed the instability of market equilibrium, i.e., price volatility or distortion, excess supply or demand. These phenomena stems from excess incentives to the players, asymmetric information, players' irresponsible strategic behaviors, and non acquaintance of trading system. This paper suggests the basic design for domestic carbon trading system in future and a stepwise introduction strategy for it including the incentive auction scheme, the total quantity of incentive needed, and how to finance it. Meantime, the further simulations on the various sectors based on voluntary participation must be essential for learning experiences and better policy design.

• Environmental and Resource Economics Review
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• v.16 no.1
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• pp.27-63
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• 2007

Using the CGE model, this paper investigates economic impacts of a shortage in crude oil resulting from voluntary export restraints, OPEC's agreement of a cut in oil production, and/or a storing on speculation. Unlike most previous studies considering oil price as the unpredictable variable, this study constructs the model to determine the oil price endogenously under the condition of an insufficient supply of crude oil. According to IEA's extraordinary steps for a shortage of crude oil, we investigate an economic impact of 7~12% shortage below the level of business as usual. The results show that oil price soars by 17.3~33.5%, the rate of economic growth falls by 0.52~0.96%p, and the consumer price index(CPI) rises by 0.8~1.51%p. These results imply that increasing in 1%p of oil price results in decreasing in 0.03%p of economic growth and increasing in 0.045%p of consumer price index. The production of electricity declines because of the increase in production cost. A shortage of crude oil has an effect on sources of electricity. Most reduction in electricity generation occurs from the reduction in the thermal power generation which is highly dependent on crude oil. The shortage of crude oil causes demand for petroleum to significantly decline but demand for coal and heat to increase because of the substitution effect with petroleum. Demand for gas rise in the first year but falls from the second year.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.1
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• pp.68-78
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• 2013

In this paper, we propose an early spectrum sensing(ESS) as an advance preparation for radio-access trial, which enables multi-mode terminals to access the most appropriate radio-access system in a cloud-conceptual base station system where multiple radio access technologies(RATs) coexist. Prior to a random access to one of RATs, a multi-mode terminal conducts a spectrum sensing over entire frequency bands of whole RATs, then select the RAT with the lowest sensing power, that is likely to have the most available spectrum. Thus, an access failure caused by that the selected RAT has no available radio spectrum could be avoidable in advance. In computer simulation, we consider as various RATs as possible. First, circuit and packet systems are taken into consideration. In addition, the packet systems are classified according to the feasibility of carrier aggregation(CA). In case of terminal, three modes are considered with circuit-only, packet-only, and multi-mode. Subsequently, packet traffic is classified into real-time and non-real-time traffic with three different tolerable delay levels. The simulation includes a call process starting with a call generation and ending up with a resource allocation reflecting individual user's QoS requirements and evaluates the proposed scheme in terms of the successful access probability, system access time, system balancing factor and packet loss probability.