• The Journal of Fisheries Business Administration
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• v.45 no.1
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• pp.109-119
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• 2014

This study aimed to examine the applicability of a portfolio approach to the ecosystem-based fisheries management targeting the large purse seine fishery. Most fisheries are targeting multispecies and species are biologically and technically interacted each other. It enables a portfolio approach to be applied to find optimal production of each species through expected returns and risk analyses. Under specific assumptions on the harvest quota by species, efficient risk-return frontiers were generated and they showed a combination of optimal production level. Comparisons between portfolio and actual production provided a useful information for targeting strategy and management. Results also showed the possibility of effective multispecies fisheries management by imposing constraints on each species such as total allowable catch quotas.

• KDI Journal of Economic Policy
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• v.39 no.2
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• pp.75-98
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• 2017

This paper aims to estimate the social discount rate (SDR) rather than dig into its theoretical foundation. As SDRs can be derived by investigating both the rate of return on investment and the social time preference rate, we estimate the marginal productivity of both private and public capital and the time preference rate based on the Euler equation. In order to provide a single representative SDR, the weighted averages of the marginal productivity and time preference rate, whose weights are determined by the flow of funds data reflecting the social demand of funds, are presented. Based on the empirical results, we argue that the marginal productivity of private capital stands in the middle of the 3% range while that of public capital varies from 4.5% to 8.6%, with the time preference rate showing a decreasing trend from 3.2% in the early 2000s to 1.2% by around 2030. The single representative SDR or the weighted SDR is estimated to be approximately 3.0~4.5% and expected to continue its downward trend for the foreseeable future.

• Journal of the Society of Naval Architects of Korea
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• v.47 no.3
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• pp.447-453
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• 2010

Response-based approach is getting more preferred in determining the design sea-state for offshore structures because traditional environment-based approach is known to yield a much conservative design condition. This paper introduces the inverse first-order second-moment (IFOSM) method as a response-based approach, which is expected to give a more feasible design condition at the cost of reasonable number of motion analyses. The IFOSM method is based on the theory of probability and adopts an optimization scheme to determine the design point. Both the design maximum response and design sea state can be obtained straightforwardly from the optimum. The IFOSM method has been applied to a turret-moored FPSO's design problem and showed its effectiveness in practical use.

• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.107-110
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• 2008

The price of natural gas import continues to rise, as well as its domestic consumption rate. This research examined the economic feasibility of domestically developing and producing gas hydrate to substitute imported natural gas. Today, the technology to commercially produce gas hydrate is still lacking; however, if the gas hydrate is able to be commercially produced domestically and replace imported natural gas, the annual economic benefit for the Republic of Korea would be 211 - 833 USD/ton. From the industry's point of view, gas hydrate is a high value investment since one can expect an annual profit of over 150USD/ton. The commercial value of gas hydrate development will increase as long as the natural gas market continues to expand and as the increase of natural gas consumption remains steady. With further development of technology, one can anticipate an even higher expected return on the investment.

• Journal of The Korean Society of Agricultural Engineers
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• v.46 no.5
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• pp.89-98
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• 2004

The amount of rice yield reduction due to inundation should be estimated to analyse economic efficiency of the farmland drainage improvement projects because those projects are generally promoted to mitigate flood inundation damage to rice in Korea. Estimation of rice yield reduction will also provide information on the flood risk performance to farmers. This study presented the relationships between inundated durations and rice yield reduction rates for different rice growth stages from the observed data collected from 1966 to 2000 in Korea, and developed the rice yield reduction estimation model (RYREM). RYREM was applied to the test watershed for estimating the rice yield reduction rates and the amount of expected average annual rice yield reduction by the rainfalls with 48 hours duration, 10, 20, 50, 100, 200 years return periods.

• Industrial Engineering and Management Systems
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• v.16 no.1
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• pp.118-128
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• 2017

Uncertain factors in finical markets make the prediction of future returns and risk of asset much difficult. In this paper, a model,assuming the admissible errors on expected returns and risks of assets, assisted in the multiperiod mean variance portfolio selection problem is built. The model considers transaction costs, upper bound on borrowing risk-free asset constraints, cardinality constraints and threshold constraints. Cardinality constraints limit the number of assets to be held in an efficient portfolio. At the same time, threshold constraints limit the amount of capital to be invested in each stock and prevent very small investments in any stock. Because of these limitations, the proposed model is a mix integer dynamic optimization problem with path dependence. The forward dynamic programming method is designed to obtain the optimal portfolio strategy. Finally, to evaluate the model, our result of a meaning example is compared to the terminal wealth under different constraints.

• Journal of The Korean Society of Agricultural Engineers
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• v.47 no.2
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• pp.45-52
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• 2005

Biomass is one of the most competitive renewable energy resource and can be used for heating for rural applications. A economic assessment was made of biomass heating, using the tool BIOH2000 from $RETScreen^{\circledR}$ International Clean Energy Decision Support Centre. For a 260kW heating system for 50 farm houses, the assessment showed a very promising results. Internal rate of return was $19.7\%$ and year-to-positive cash flow was 5.1 years. Relative price of biomass over fossil fuel significantly affected the economic feasibility of the project. Heating demand was directly related to annual demand of biomass and economic feasibility. Relative cost of distribution pipe over the total initial costs also affected the economic feasibility of the project. The economic feasibility was expected to be improved by the probable greenhouse emission reduction credit and reduction of initial costs through utilizing existing heating system for peak or back up heating system.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.4
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• pp.18-23
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• 1998

Approximations inherent in the Cohn synthesis theory, which is generally perferree as a convinient design technique for direct-couple waveguide filter, results in considerable devications from the required responses as the design bandwidth increases. In this paper, two main deviations likely to occur in practice are examined using the mode-matching technique. They are a shift in couoff frquencies and large return loss occuring near coutoff frequencyles. Using the power loss ratio, the first effect is corrected to the resulant filter structure from cohn synthesis. In order to show the validity of the intorduced approackes. Ka-band waveguide filter ahs been designed and manufactored. The experimental curve follow the expected curves after corrections fairly closly.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.10a
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• pp.61-65
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• 2008

In this paper, we studied a ZnO-based film bulk acoustic resonator (FBAR) device fabricated on a specially designed multi-layerd Bragg reflector part. Very thin chromium adhesion layers (0,03um thick) were additionally deposited to improve the quality of the Bragg reflector and some thermal treatments were performed to improve the resonant characteristics of the device. At the operating frequency of ${\sim}2.7GHz$, excellent resonant characteristics were observed in terms of return loss and quality factor, and effective electromechanical coupling coefficient. These findings are expected to be highly promising and effective for improving the performance of the FBAR devices at high frequency.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.12
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• pp.1264-1268
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• 2003

In this paper, we have designed the duplexer using non-radiative dielectric(NRD) guide in millimeter wave band. The designed duplexer is composed of two stepped-impedance filters and T-junction. Stepped-impedance filters we designed with an equivalent circuit model of evanescent waveguide and the T-junction is optimized to minimize return loss of -20 dB or more. The characteristics of duplexer show good agreements with the expected results.