• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.3
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• pp.179-184
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• 2019

In many countries, such as developing countries where electricity is scarce, small wind turbines in the form of Off Grid are an effective solution to solve power supply problems. In some countries, the expansion of power systems and the decline of electricity-intensive areas have led to the use of small wind power in urban road lighting, mobile communications base stations, aquaculture and seawater desalination. With this change, the size of the small wind power industry is expected to have greater potential than large-scale wind power. In the case of small wind power generators, the generator is controlled at a variable speed, and the voltage and current generated by the generator have many harmonic components. To solve this problem, the AC to DC converter to be studied in this paper is a three-phase step-up type converter with a single switch. The inductor current is controlled in discontinuous mode, and has a characteristic of having a unit power factor by eliminating the harmonic of the input current. The proposed converter is composed of LCL filter and three phase rectification boost converter at the input stage and a single phase full bridge for grid connection. It is a control system with energy storage system(ESS) that the system stabilization can be pursued against the electric power.

• The Journal of the Korea Contents Association
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• v.19 no.2
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• pp.516-524
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• 2019

The purpose of this study is to analyze the cases related to the multi-dimensional urban planning and its related systems that can contribute to the urban regeneration as the policies and projects for stereoscopic city increase. Through the case analysis, urban regeneration function and role of multi-dimensional urban planning are identified as connection of places, activation of local economy, expansion of infrastructure and supply of housing. In the institutional sector, private participation is hindered due to the ban on the establishment of the right to hold state property. In addition, it is difficult to utilize the three-dimensional urban space without land securing at a certain rate based on uniform installation standards of the two-dimensional land use plan, and the problem of insufficient interconnection between law and institution is derived. In conclusion, it should actively support and promote the promotion of the three-dimensional facility with the aim of diversifying the regional infrastructure structure and strengthening the urban function. In addition, development of stereoscopic and compound development should be promoted for old urban areas, and parking lots, underground shopping malls, parking lots, etc. should be installed using the subspaces of parks, schools, roads and traditional markets of old residential areas. Finally, cooperation between the central government, the municipalities and the private sector is necessary for the realization of these urban regeneration projects.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.1
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• pp.224-235
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• 2019

The increase in the amount of energy used in the agricultural sector due to the expansion of agricultural machinery and greenhouse horticulture has caused a range of problems, such as an increase in the cost of input, such as heating costs and greenhouse gas emission. To overcome these problems, this study examined the current status of energy use in greenhouse horticulture as well as the change patterns of non-taxable oil and agricultural electricity, and reviewed the current status of the supply of renewable energy and energy saving facilities for agriculture. This study investigated the area of advanced and renewable energy and energy saving facilities implemented, applied the energy saving ratio of advanced and renewable energy and energy saving facilities, and determined the effects of renewable energy in the agricultural sector, such as increase in production, decrease in heating cost, reduction in Government financial expenditure, reduction in greenhouse gas emission, and oil substitution effect.

• Journal of Climate Change Research
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• v.4 no.2
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• pp.141-158
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• 2013

In this study, the projection of future heating and cooling degree days (HDDs and CDDs) has been conducted over South Korea for the period 1996~2005 with 2046~2055 and 2091~2100, using CCSM3 and MM5 simulations driven by the six IPCC SRES emission scenarios (A2, A1B, A1FI, A1T, B1, and B2). Annual mean surface air temperature increases by $1.2{\sim}3.4^{\circ}C$ at the end of the 21st century comparing to the present-day (1996~2005) in South Korea. HDDs decrease by 8~25% and CDDs increase up to 242~1,448% with corresponding changes in temperature. These increases and decreases also change the duration of HDDs and CDDs. HDDs duration decreases by 1 month, while the expansion of CDDs duration is much longer than 2 months. Thus, projected future HDDs and CDDs changes appear that cooling energy demand in summer season would increase and heating energy demand in winter would decrease in the future. Especially, these remarkable changes would be obvious at high mountain area, Gangwon-do and at south area, Jeju island. In the sense of future energy supply and policy, electrical energy for cooling in summer could be getting much more its importance rather than fossil energy used for heating in winter.

• Journal of the Korean Institute of Gas
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• v.23 no.2
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• pp.74-81
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• 2019

Expansion turbine system to recover the electricity energy from natural gas transmission stations is a well-known technique. The turbo-expander efficiency depends on the ratio of the natural gas flow rates to the design flow rate of the turbo-expander. However, if there is a big difference of the natural gas flow rate through the pressure letdown station because of seasonal supply pattern, that is, high flow rate in winter while low flow rate in summer, single turbo-expander system is not so efficient as to recover the pressurized energy from the low flow-rate natural gas. Therefore, we have proposed a new concept of double turbo-expander system: one is a big capacity and the other a small capacity. Here we have theoretically computed the electric powers at the pressure reduction from 18.5 bar to 7.5 bar depending on the inlet conditions of temperature and flow rate. The calculated electricity generation has been increased by 30% from 12.4 MW in a single turbo expander to 16.1 MW in the proposed double turbo-expander system when a minimal design efficiency of 0.72 is applied.

• Korean Journal of Heritage: History & Science
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• v.45 no.3
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• pp.100-113
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• 2012

In the midst of recent active excavation, lots of Silla(新羅) roof-end tiles are unearthed in Yeongnam area(嶺南地域). These are confirmed the same tile frame as the Silla tiles excavated in Gyeongju(慶州). It is represented by the Silla tiles excavated in Ingaksa Temple(麟角寺) excavation research. Roof-end tile with arabesque design(唐草文平瓦當) etc. including roof-end tile with lotus design(蓮花文圓瓦當) are judged to be the tile frame produced by the same frame of roof-end tile that was excavated in Gyeongju, Wolseong(月城) and Hwangyongsa Temple(皇龍寺址). There are three kinds of cases concerning the transportation of tile manufacture ; the roof-end tile manufactured in Gyeongju directly moved to each region, only tile frame moved to site to be manufactured there, and tile manufacturer moved to site to manufacture there. This article considers the case of the roof-end tile manufactured in Gyeongju that was directly moved to each region. In case of the Silla tiles excavated in region especially Ingaksa Temple, the aspects of tiles in accordance with different era show the repeated coexistence, expansion and maintenance. This situation is significant as a clue to understand the supply from Gyeongju not as temporary, but as continuous. On the other hand, if the Gyeongju tiles flowed directly into each region, and if the road was built of gravels and the means of transportation was cart, the damage from movement must never be prevented. On the contrary, transportation through waterway might be advantageous due to the reduction of labor and damage rate and the easiness of loading. Accordingly, it tells us why the ruins where roof-end tiles were excavated located near big and small rivers or streams. Of course there are some ruins located in a fixed distance, but the distance may be enough to endure the impact put on tiles from the overland movement. Therefore, in case of direct inflow form long distance, transportation must be finished by overland movement after waterway movement.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.4
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• pp.626-631
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• 2019

The policy-making and technological development for the supply expansion of eco-friendly automobiles has been continuing, but the internal combustion engines still accounts for about 95%. Also, in order to meet the stricter emission regulations of internal combustion engines based on fossil fuels, the proportion of after-treatments for vehicles and (ocean going) vessels is gradually increasing. This study is a basic study for the post-Euro-VI exhaust response of CNG buses, and it is to investigate the basic characteristics according to Pd substitution transition metal effect, catalyst volume effect and space velocity. A catalysts was prepared and tested using a model gas reactor. The NGOC catalyst with 3Pd exhibited the highest catalytic activity with 22% at $300^{\circ}C$, 48% at $350^{\circ}C$ and about 75% at $500^{\circ}C$. 3Co NGOC containing 3wt% of transition metal was excellent in oxidation ability, and it was small in size of 2nm, and the degree of catalyst dispersion was improved and de-NO/CO conversion was high. The volume of the NGOC-LNT-SCR catalyst system was optimal in the combination of 1.5+0.5+0.5 with a total score of 165, considering $de-CH_4/NOx$ performance and catalyst cost. For SV $14,000h^{-1}$, the $CH_4$ reduction performance was the highest at about 20%, while the SV $56,000h^{-1}$ was the lowest at about 5%. If the space velocity is small, the flow velocity decreases and the time remaining in the catalyst volume become long, so that the harmful gas was reduced.

• Journal of Korea Society of Industrial Information Systems
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• v.24 no.2
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• pp.57-63
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• 2019

In order to facilitate the supply of gradually increasing power demand, it is also necessary to increase the number of power cables for power transmission as well as generation facilities. However, the expansion of electric power cables for supplying power to most urban areas requires a space for installation of additional cables, and the space for installing cables in domestic downtown areas is insufficient at present. The superconducting power cable, which can transmit more power with the same size, has emerged as an alternative to overcome the insufficient cable installation space. However, superconducting power cables, which have the advantage of large power transmission, have some losses in the AC (Alternating Current) system. Therefore, the design and analysis of AC losses are essential to introduce superconducting power cables in AC power transmission systems. In this paper, we analyze the AC loss of various superconducting power cables and consider the actual superconducting power cables and their application to the system. Although there is a theoretical calculation method of AC loss for single superconducting wire, it is not easy to calculate AC loss of superconducting power cable with large number. Therefore, the authors intend to analyze various kinds of superconducting power cable AC loss by using electromagnetic finite element analysis considering E-J (Electric field-Current density) characteristics of superconductivity. The analysis of the AC loss characteristics of the superconducting power cable will be an important factor in the design and development of the superconducting power cable to be applied to the actual system.

• Food Science and Industry
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• v.54 no.2
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• pp.93-101
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• 2021

Hazard Analysis Critical Control Point (HACCP) systems were developed to ensure a high level of food safety and reduced risk of foodborne illness. This paper focuses on significant issues associated with the implementation of HACCP; it provides an overview on recent literature. The structure of the paper follows six groupings of issues in the international literature of HACCP: (1) comparative studies and unification plan between HACCP and other food safety regulations; (2) verification of the HACCP system's effectiveness in improving food safety; (3) establishment of critical control point (CCP) for various foods HACCP model development; (4) expansion of HACCP application in the various fields and small businesses;(5) the impacts of HACCP on consumer's preferences and firms' financial performance in food industry; (6) HACCP and technological changes. The paper concludes with some suggestions for the future research in order to promote safe food supply chain for global customers.

• Journal of the Korean Society of Marine Environment & Safety
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• v.26 no.7
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• pp.915-921
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• 2020

Thermoacoustic instability caused by air conditioning in a combustion chamber has emerged as a problem that must be solved to establish a stable combustion system. Thermoacoustic instability is largely divided into primary and secondary acoustic instability. In this study, an experimental study of the effects of heat losses was conducted to investigate the mechanism of secondary acoustic instability. To generate the secondary acoustic instability, a quarter-wavelength resonator with one open end and one closed end was used, and the inside of the resonator was filled with premixed gases. Subsequently, secondary acoustic instability with downward-propagating flames could be realized via thermal expansion on the burnt side. To control heat losses qualitatively, an additional co-axial tube was installed in the resonator with air or nitrogen supply. Therefore, additional diffusion flames can be formed at the top of the resonator depending on the injection of the oxidizer into the co-axial tube when rich premixed flames are used. Consequently, secondary acoustic instability could not be achieved by increasing heat losses to the ambient when the additional diffusion flame was not formed, and the opposite result was obtained with the additional diffusion flame.