• Journal of the Korean Regional Science Association
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• v.35 no.3
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• pp.7-23
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• 2019

Smart cities are expanding their spatial scope to urban areas and regions. Linking regional economic development strategies beyond the borders with smart city planning can lead to cooperation and economic development between regions and countries as well. The purpose of this study is to suggest cooperation and regional development of the three nations - Korea, North Korea and China - through the Yellow Sea Rim Smart Region. To this end, smart city strategies and economic development plan with implementation status in the three countries including special economic zones have analyzed that could be the spatial basis of the smart region. On the west coast of Korea facing the Yellow Sea, lots of projects related to smart cities are actively underway in Saemangeum, Yellow Sea Free Economic Zone(YESFEZ), and Incheon Free Economic Zone(IFEZ). Although the political situation is still uncertain, North Korea is analyzed to have economic and technical potential in the west coast connecting Haeju, Nampo, and Sinuiju. In Liaoning and Shandong provinces of China, smart city projects have been actively promoted in recent years especially in the state-supporting industrial cities. Restoration of economic cooperation between South Korea and China, linkage of transportation networks, vitalization of cross-border cooperation projects between China and North Korea centered on Dandong and Sinuiju, and the connecting of smart city infrastructure and services for China and South Korea's economic cooperation process will make the Yellow Sea Rim as a world prosperous economic region. However, it is necessary to establish and operate a governance system through long-term planning for transnational consultation and establishment of a promotion organization.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.11 no.4
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• pp.333-349
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• 2013

As the capacity of spent nuclear fuel storage pool at reactor sites becomes saturated in ten years, long term dry storage strategy has been recently discussed as an alternative option in Korea. In this study, we reviewed safety-criteria-related research results on spent nuclear fuel performance and integrity under long-term dry storage and proposed the direction and the scope of future domestic research and development. Creep and hydride effect in relation to the embrittlement are known to be the major degradation mechanisms of the spent fuels during the long term dry storage. However, recent research results showed that hydride reorientation and hydride embrittlement are one of the most critical factors to the spent fuel integrity. Accordingly safety criteria of US and Japan for the storage system are basically founded on those mechanisms. However, in Korea, not only in-pile but out-of-pile experimental data have not been generated to understand fuel cladding degradation and to determine the criteria to ensure the safety. In addition, the transient behavior of the spent fuel during transportation also needs to be thoroughly examined. Therefore, various experimental research and development will be required to establish our own safety criteria for future long-term dry storage of domestic spent fuels.

• Journal of Biosystems Engineering
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• v.33 no.4
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• pp.224-229
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• 2008

This study was aimed to minimize the impact force and vibration transmitted to the transporting materials from the trailer and wheel shaft by installing the leaf spring suspension device at the space between the wheel shaft and frame of power tiller trailer. The developed trailer equipped with leaf spring suspension device was compared to the existing trailer without suspension device, in order to identify the vibration absorption effect of the leaf spring. The results of this study could be summarized as follows; (1) The length and the maximum bending amount of the leaf spring were designed as 1,000 mm and 42 mm, respectively, considering the possible space for installing at below the trailer. When 4 leaf springs were installed on both wheel shafts, the allowable maximum load was identified as 9,418 N. (2) The average vibration accelerations for the frequency less than 20 Hz, where the severe transporting loss could be represented, were $0.017\;m/s^2$ and $0.133\;m/s^2$ for the developed and the existing trailer, respectively, showing the vibration absorption effect of about 87%. And the average vibration accelerations on the driver's seat for the frequency less than 20 Hz were $0.01\;m/s^2$ and $0.20\;m/s^2$ for the developed and the existing trailer, respectively, which showed the similar vibration absorption effect. (3) The change of the average vibration accelerations for the frequency from 20 Hz to 80 Hz showed the similar tendency with the result for the frequency less than 20 Hz, but the effect for developed trailer was reduced slightly. And the effect of vibration absorption for the above 80 Hz was reduced highly. However, by installing the leaf spring suspension device at the trailer, the low frequency below 40 Hz, which could affect on transporting loss severely, could be reduced highly. (4) The maximum vibration acceleration for the frequency less than 20 Hz were $0.027\;m/s^2$ and $1.267\;m/s^2$ for the developed and the existing trailer, respectively. And the change of maximum acceleration between 20 Hz and 120 Hz was showed similar tendency with the result for the frequency less than 20 Hz, but the width of change was reduced highly.

• Journal of Biosystems Engineering
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• v.43 no.1
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• pp.1-13
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• 2018

Purpose: The development of compact tractors that can be used in dry fields, greenhouses, and orchards for pest control, weeding, transportation, and harvesting is necessary. The development and performance evaluation of power transmission units are very important when it comes to tractor development. This study evaluates the performance of a driving power transmission unit of a 50 kW multi-purpose narrow tractor. Methods: The performance of the transmission and forward-reverse clutch, which are the main components of the driving power transmission unit of multi-purpose narrow tractors, was evaluated herein. The transmission performance was evaluated in terms of power transmission efficiency, noise, and axle load, while the forward-reverse clutch performance was evaluated in terms of durability. The transmission's power transmission efficiency accounts for the measurement of transmission losses, which occur in the transmission's gear, bearing, and oil seal. The motor's power was input in the transmission's input shaft. The rotational speed and torque were measured in the final output shaft. The noise was measured at each speed level after installing a microphone on the left, right, and upper sides. The axle load test was performed through a continuous equilibrium load test, in which a constant load was continuously applied. The forward-reverse clutch performance was calculated using the engine torque to axle torque ratio with the assembled engine and transmission. Results: The loss of power in the transmission efficiency test of the driving power unit was 6.0-9.7 kW based on all gear steps. This loss of horsepower was equal to 11-18% of the input power (52 kW). The transmission efficiency of the driving power unit was 81.5-89.0%. The noise of the driving power unit was 50-57 dB at 800 rpm, 70-77 dB at 1600 rpm, and 76-83 dB at 2400 rpm. The axle load test verified that the input torque and axle revolutions were constant. The results of the forward-reverse clutch performance test revealed that hydraulic pressure and torque changes were stably maintained when moving forward or backward, and its operation met the hydraulic design standards. Conclusions: When comprehensively examined, these research results were similar to the main driving power transmission systems from USA and Japan in terms of performance. Based on these results, tractor prototypes are expected to be created and supplied to farmhouses after going through sufficient in-situ adaptability tests.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.12
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• pp.1069-1075
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• 2017

With the recent development of space technology, the satellite market, especially the small satellite market, is growing globally. As the satellite market continues to grow, the launch vehicle market is also growing, and demand for low-cost launches is increasing. There are a number of options for low-cost launches, including development of engine that uses low-cost propellants, product and transportation cost savings, but the most effective way to reduce launch costs is to reuse the used launch vehicles. USA's Space Shuttle, a famous rocket as manned spacecraft, could be referred as the start of reusable launch vehicle. However, Space Shuttle had limited reusable parts and it was very expensive even though it is a reusable launch vehicle because of its low efficiency. In recent years, aiming at a real reusable launch vehicle, reusable launch vehicle for commercial purposes have been developed around USA's SpaceX and Blue Origin, and re-landing tests were successfully accomplished. In addition, SpaceX successfully did the re-using of first-stage launch vehicle that had been succeeded in re-landing already. In accordance with this trend, countries such as Europe and India are also concentrating on the study of reusable launch vehicles. Including Blue Origin, companies like Virgin Galactic and XCOR in the United States, are also trying to commercialize the same reusable technology as the private manned space tourism. Confirmation of these technology trends is essential, because the re-use technology could change the landscape of the global launch vehicle market.

• Journal of the Korean Applied Science and Technology
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• v.35 no.3
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• pp.865-875
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• 2018

Selection of optimum reaction conditions during deoxygenation process of palm oil is essential factor to obtain the maximum yield of bio-jet fuel. In this context, the deoxygenation of palm oil was carried out in a fixed bed reactor with an internal diameter of 1 inch loaded with a 1 wt.% $Pt/Al_2O_3$ catalyst. The composition of the organic liquid product(OLP), which can be utilized as a transportation fuel through the upgrading process, was analyzed by a gas chromatography method. The palm oil/hydrogen ratio and hydrogen pressure in the feed affected the decarboxylation(DCB) and hydrodeoxygenation(HDO) reactions, resulting in a change in the composition of the OLP. As the reaction temperature increased, the continuous cracking reaction of the deoxygenation product was promoted and the product composition in the $C_5{\sim}C_{14}$ region was increased. Thus, the results can help to understand the characteristics of deoxidation reaction of palm oil as well as the subsequent process, hydro-upgrading, to obtain the maximum yield of bio-jet fuel.

• Journal of Distribution Science
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• v.13 no.2
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• pp.95-104
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• 2015

Purpose - This is a comparative study of the market development and characteristics of Ulsan in South Korea, Fukuoka in Japan, and Yanji in China, which are major East Sea Rim cities with adjacent areas of similar natural characteristics of the sea and the country. Particularly, it considers these aspects while focusing on the evolution of networks that appear in the distribution system and at the same time examining the institutions of market activation and regulations that are handled by the central and the local government and the changing logistics due to the development of transportation and the concern of food safety, using a meso-analysis approach. Research design, data, and methodology - The study used a historical and comparative approach with a focus on case studies. It made use of various materials such as local newspaper articles, reports, literature, interviews with experts, discussions with local merchants, discussions with customers, and so forth. Results - In the case of Fukuoka, from the 1960s, due to the entry of supermarkets, supermarkets expanded and they have now come to a dominant market position in the current market. They offer a convenient and comfortable environment while providing a large mall offering a variety of educational and cultural activities for customers to meet the customers' needs, such as the preferences of Korean tourists, who appear to prefer Japanese foods. The Fukuoka City Central Wholesale Market has been exporting fruits and vegetables as well as seafood products to Korea, China, and so forth. In the case of Ulsan, as in the early 2000s, due to the expansion of supermarkets, the traditional markets have been shrinking and further, the modernization of traditional markets was conducted under the auspices of the Small Business Administration. In addition to the large discount malls, the expansion of SSM is expected to further drive the small trader bay. Shopping malls, department stores, and traditional markets contend with each other in Yanji, China, but a large number of citizens appear to prefer traditional markets and imported milk in the supermarket after the melamine scandal in China. Recently, the WanYuan (萬源) wholesale market has been partially completed and made an attempt to become a logistics hub in Northeast Asia. Conclusions - For the development of Korea's retail industry, it is important to offer the government with proposals regarding desired regulation. On the other hand, in order to enable the business of traditional markets, it requires an association for cultural tourism. At present, it would be better to provide a venture fund for the youth rather than infrastructure support. This study emphasizes the importance of institutions and policy to develop networks in the East Sea Rim. Future studies should conduct a survey on customers, managers, and merchants more carefully and systematically to understand the market situation while considering the size of the city and its evolution of markets, as well as policies and institutions.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.5
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• pp.146-152
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• 2018

In this study, to improve the performance of asphalt mixtures for plastic deformation occurring mainly in Korea, complex modifiers were prepared by mixing powders and liquid type modifiers. The main constituents were powdery diatomaceous earth, mica and carbon black, and liquid type solid 70% SBR latex. The tensile strength ratios for the two asphalt mixtures used in the test were above 0.80 for the Ministry of Land Transportation (2017) asphalt mixture production and construction guidelines. The effects of increasing the tensile strength in the dry state was more than 14% when the composite modifier was added. The deformation rate per minute by the wheel tracking test load was an average of 0.07 to 0.147 for each mixture. The strain rate per minute was improved by the modifier, and the dynamic stability was improved by almost 100% from 295 to 590. In addition, the final settling was reduced from 11.38 mm to 9.57 mm. A plastic deformation test using the triaxial compression test showed that the amount of deformation entering the plastic deformation failure zone at the end of the second stage section and in the third stage plastic deformation section was 1.76 mm for the conventional mixture and 1.50 mm for the complex modifier mixture. The average slope of the complex modifier asphalt mixture mixed with the multi-functional modifier was 0.005 mm/sec. The plastic deformation rate is relatively small in the section where the road pavement exhibits stable common performance, i.e. the traffic load.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.2
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• pp.28-36
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• 2018

Islands are supplied with power from diesel generation or from photovoltaic power generation, and problems with offshore environmental impacts (age deterioration, salt pollution), environmental pollution (exhaust gas, noise, dust) and power generation costs (installation, maintenance) have increasingly emerged. In 2016, the cost recovery rate was only 27%, and deficits reached 73% on 65 islands managed by KEPCO. In terms of deficits, the costs incurred in the power generation sector accounted for 91%, with the ratio of fixed costs at about 60%. Analysis suggests that operating costs can be reduced with an optimal power supply system that improves power generation efficiency and makes operating systems more efficient. Therefore, it is possible to simplify fuel transportation and facility maintenance, because one island integrates the power plants of remote islands, and offshore cable is used to supply power to the other islands. From the economic evaluations in this paper, an algorithm deciding offshore cable layout validity for an integrated power supply between adjacent islands is presented. Simulation results based on the proposed algorithm confirmed that an integrated power supply is economical for existing stand-alone operations on islands having diesel generation, low peak power, and near distances.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.1
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• pp.12-17
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• 2018

In order to enhance the realism of a virtual environment, a method of maximizing the stiffness of the virtual environment model is needed, which maintains the stability of the haptic system. In our previous research, we proposed a haptic system with a first order hold, instead of a zero order hold, and showed that the maximum available stiffness of a virtual spring with the first-order hold is larger than that with the zero-order hold. However, in terms of real system implementation, the zero order hold is a more common and easy method. In this paper, we propose an extrapolation method and a high frequency zero-order-hold output method in order to obtain the stability region using a zero order hold, which is equivalent to the method using the first-order-hold. The simulation results shows that the stability range of the virtual spring becomes almost the same as that of the method using the first order hold when the sampling period of the high frequency zero-order-hold method is decreased. Moreover, the stability range of the proposed method is several times to several tens of times greater than that of the method using the zero order hold only. Therefore, it is expected that the proposed method can enhance the realism of rigid bodies in a virtual environment.