• Journal of Korea Port Economic Association
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• v.38 no.3
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• pp.69-86
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• 2022

This study analyses the necessity of the large-size shipyard and explores competitiveness factors of it. Furthermore, the competitiveness is evaluated and the economic feasibility of building and operation of shipyard is examined. As a result of AHP analysis of the determining factors of the competitiveness of the repairing shipyard, the importance of the factors was found in the order of arrival and departure safety, repair technology, dock and wharf facilities, repair cost, repair period (on time delivery), and repair parts supply. Moving distance, repair service quality, repair parts supply, arrival and departure safety, repair technology, dock and quay wall facilities, and repair period (on time delivery) were identified as key factors in the AHP analysis for competitiveness of the Busan Port repair shipyard to be built in the future. As a result of the analysing economic feasibility, the net present value of the Busan Port repair shipyard construction and operation investment project was KRW 435.6 billion, and the internal rate of return was 9.8%, higher than the social discount rate (4.5%), and the cost-benefit ratio (B/C) was high at 1.167. As a result of the study, the necessity and economic feasibility of the Busan Port repair shipyard are sufficiently ensured, and the competitiveness assessment was highly positive.

• Progress in Superconductivity and Cryogenics
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• v.20 no.4
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• pp.60-64
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• 2018

As the offshore wind farms increase, interest in the efficient power system configuration of submarine cables is increasing. Currently, transmission system of the offshore wind farm uses almost AC system. High temperature superconducting (HTS) power cable of the high capacity has long been considered as an enabling technology for power transmission. The HTS cable is a feasible way to increase the transmission capacity of electric power and to provide a substantial reduction in transmission losses and a resultant effect of low CO2 emission. The HTS cable reduces its size and laying sectional area in comparison with a conventional XLPE or OF cable. This is an advantage to reduce its construction cost. In this paper, we discuss the economic feasibility of the 22.9 kV HTS power cable and the conventional AC power cables for an offshore wind farm connections. The 22.9 kV HTS power cable cost for the offshore wind farm connections was calculated based on the capital expenditure and operating expense. The economic feasibility of the HTS power cable and the AC power cables were compared for the offshore wind farm connections. In the case of the offshore wind farm with a capacity of 100 MW and a distance of 3 km to the coast, cost of the 22.9 kV HTS power cable for the offshore wind farm connections was higher than 22.9 kV AC power cable and lower than 70 kV AC power transmission cable.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.4
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• pp.273-279
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• 2021

Winglets are specialized wingtip devices to reduce induced drag, and they have been installed on Boeing-made aircraft since the 1980s, Airbus has also developed a winglet named 'Sharklet' since 2009 and has started providing them as an option to the A320 Family. The winglet has the effect of improving take-off performance, reducing fuel consumption, increasing payload, and increasing flight distance by reducing the induced drag generated at the tip of the wing. The purpose of this study is to analyze the actual flight data of the sharklet-installed and non-sharklet-installed models of the A321 aircraft to verify the fuel efficiency improvement due to the winglet installation, and to analyze the economic analysis accordingly. Through this, it can be used to determine the winglet installation when introducing an aircraft or to make a decision for upgrading the existing aircraft. To this end, a case study on the aerodynamic characteristics and effects of the winglet installation was conducted, and the economic analysis was verified.

• KDI Journal of Economic Policy
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• v.36 no.1
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• pp.43-80
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• 2014

This study suggests a model for calculating total benefit rigorously to use the contingent valuation method (CVM) in cost-benefit analysis (CBA). Estimating households' willingness to pay through survey method, the study attempts to demonstrate if a respondent's income and the distance between a respondent's residence and the location of a target facility affect her willingness to pay. The estimation results from a structural model show that income and distance-decay effects exist and that the calculated total benefit varies largely when these effects are ignored. The study emphasizes the effects of income and distance-decay on the total benefit must be carefully considered in using CVM for CBA. Even though the total project cost is precisely estimated, the benefit/cost (B/C) ratio may differ largely when the total benefit is not correctly calculated. Also, an ad hoc model generates significantly different estimates from the utility difference model this study adopted. The difference in estimates suggests that the total benefit has to be estimated by a structural model. Finally, simulations are performed to check the validity of the model as well as to predict consequences when income and distance-decay effects are not properly treated. The results from simulations reveal it is not desirable to ignore those effects considering the perspectives of balanced regional development.

• Journal of Bio-Environment Control
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• v.31 no.1
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• pp.8-13
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• 2022

This study was carried out to investigate the proper wattage and installation distance for the efficient use of nano-carbon fiber infrared heating lamp (NCFIHL), a heating device advantageous for heating energy saving, when the production of watermelon plug seedlings in the plug seedling nursery in winter season. Six small beds were divided into plastic film, and 700 W and 900 W nano-carbon fiber infrared heating lamps were installed at 100 cm above the bed. 1 lamp at central (control), 60 cm interval (2 lamps), and 40 cm interval (3 lamps) heating lamps were installed in each bed inside the greenhouse. All treatments, except the control, were set to keep the night air temperature at 20℃ after lighting the NCFIHL. The leaf temperature showed a tendency to increase fast as the install distance was narrow. The leaf length and leaf width tended to increase as the installation distance of the 700 W heating lamp was narrow. The compactness was high in 700 W heating lamp with 40 cm of installation distance. Therefore, in consideration of maintaining the set temperature at night, installing 700 W electric lamps at 40 cm was an efficient power and installation distance for watermelon grafted seedlings considering economic feasibility.

• Journal of the Korean Institute of Gas
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• v.28 no.1
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• pp.19-26
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• 2024

In workplaces handling flammable gas such as hydrogen, hazardous area is determined through KS C IEC 60079-10-1 standard. Because this standard determines the hazardous distance based on the release characteristic regardless of the type of gas, indoor/outdoor conditions, and atmospheric conditions, concerns are being raised about the effectiveness. In this study, simulations (PHAST, HyRAM) were performed to calculate the hazardous distance for hydrogen under various release characteristics and atmospheric conditions, and compared these results to IEC standard log-log graph. Also, we performed regression analysis according to each result. we found that the simulation results were 0.6 to 3.8 times less than the IEC standard, presented convenient linear regression equations. In addition, We confirmed that the results of hazardous distance varied based on wind velocity and atmospheric stability at the same release characteristic. In addition, we derived linear regression equations for release characteristics and hazardous distance that can be conveniently utilized. So, when classifying hazardous area in workplaces where they handle the hydrogen, the integrated graph and linear regression equation are helpful for confirming the hazardous area. Moreover, it is expected that the economic burden will be minimized by being able to classify reasonable hazardous area and to greatly reduce the risk of hydrogen explosion.

• The Journal of Engineering Geology
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• v.12 no.1
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• pp.1-21
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• 2002

Recently, the rapid industrialization and urbanization of the country due to a high economic growth, require optimization, usage and the expansion of underground space. Therefore the consturction of large and deep basements takes place in braced excavated area where their earth retaining structures cause many problems such as settlement and damages of nearby buildings and underground utilities. this study deals with the influence distance of settlement and the amount for settlement based on the measurement which were obtained at five excavation construction sites. Maximum ground surface settlement, (0.28∼0.3)(%)H utilizing depth, is similar to the measurement and the value by Clough's method. It was found that the settlement and the influence distance of settlement calculated by Clough's method were rational.

• Archives of design research
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• v.17 no.2
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• pp.463-470
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• 2004

This paper studied tangible interaction design of VR platform and its applications that are economic In development process and cost, flexible by contents and installation conditions, and that has business potential for consumer market. The design solution uses video based virtual world and tangible interaction by motion tracking. Our platform enables a user to monitor their action and to collaborate with other users of remote place within attractive interaction feedback. We developed two design applications, Glass Xylophone 2003 and VR Class, in our platform. Glass Xylophone 2003 provides interactive music performance and helps self practice of glass xylophone. VR Class gives more serious distance learning experience with tutoring and group collaboration. They are presented in public exhibitions and tested by exhibition visitors. They showed application potential of this design solution in interactive game, distance learning, and entertainment field.

• Journal of Power System Engineering
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• v.15 no.2
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• pp.55-60
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• 2011

The popularity of diesel engines is derived primarily from their higher thermal efficiency resulting from higher compression ratio. NOx removal from the diesel emissions is very important to meet stringent emission regulations. NOx emission from diesel engines is removed by an urea-SCR or an LNT system. The urea-SCR system needs the urea-solution supply system with concentration and level sensor. This study was carried out to develop a sensor for the measurement of urea-solution concentration by an electric conductivity method. Considering experimental parameters were the material of electrode, two kinds of electric power(AC or DC), the distance between two electrodes, and the length of electrode. It was found that the AC electric power was more useful to measure the urea-solution concentration compared to DC, because it prevented an ionization of the urea-solution. The silver rod coated with Pt is the most useful electrode, tendency of which is similar to Pt rod, and the cost is more economic. We could also find out the optimum distance between two electrodes and the length of electrode was 10mm and 3mm, respectively.

• The Journal of Engineering Geology
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• v.17 no.2 s.52
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• pp.197-204
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• 2007

Tunnel deformation happens by excavation. After installation of support, tunnel is gradually stabilized over time. Effect of excavation on tunnel behavior decreases as increase of distance from face. If the time that the displacement converges by tunnel stabilization is estimated, processes after stabilization can be advanced and economic loss can be reduced. In this study, the distance of displacement convergent point from face in the tunnel constructed on sedimentary rock is estimated using control chart method. As the results of analysis using a control of chart, displacements in a sedimentary rock tunnel are converged within 100 m from each tunnel face.