• Journal of Power Electronics
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• v.18 no.3
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• pp.702-713
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• 2018

Power loss reduction and total harmonic distortion(THD) minimization are two important goals of improving three-level inverters. In this paper, an optimized pulse width modulation (PWM) strategy that can reduce switching losses and balance the neutral point with an optional THD of three-level neutral-point-clamped inverters is proposed. An analysis of the two-level discontinuous PWM (DPWM) strategy indicates that the optimal goal of the proposed PWM strategy is to reduce switching losses to a minimum without increasing the THD compared to that of traditional SVPWMs. Thus, the analysis of the two-level DPWM strategy is introduced. Through the rational allocation of the zero vector, only two-phase switching devices are active in each sector, and their switching losses can be reduced by one-third compared with those of traditional PWM strategies. A detailed analysis of the impact of small vectors, which correspond to different zero vectors, on the neutral-point potential is conducted, and a hysteresis control method is proposed to balance the neutral point. This method is simple, does not judge the direction of midpoint currents, and can adjust the switching times of devices and the fluctuation of the neutral-point potential by changing the hysteresis loop width. Simulation and experimental results prove the effectiveness and feasibility of the proposed strategy.

• Journal of Service Research and Studies
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• v.2 no.2
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• pp.53-79
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• 2012

According to Electronic Times(2012. 1. 3), "PMO was introduced from 1950s in the USA and as of 2010, PMO participated in 84% of project ordered by public and private sector." And Ministry of public administration and security announced that the Ministry will organize Task Force for arranging "standard for introduction and operation of PMO" for support of project implementation and strengthening specialty of ordering organization, and then, actively launch the Task Force from February, 2012. Thus, necessity of PMO is regarded as natural in some aspect but thesis for doctoral degree written by Kim Gi-yeong(2007) suggested, "performance of several projects begun at the same time cannot be interpreted as high according to whether PMO team exists or not." Martin et al.(2005) asserted, "according to whether PMO team exists or not, but there is no significant difference in other factor." In the contradictory situation, it is necessary to perform more various approaches for performance and necessity of PMO in the academic aspect.

• Journal of Climate Change Research
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• v.8 no.3
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• pp.213-220
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• 2017

The purpose of this study is to analyze effects of Greenhouse Gas (GHG) emission reduction in district energy business mainly based on Combined Heat and Power (CHP) plants. Firstly this paper compares the actual carbon intensity of power production between conventional power plants and district energy plants. To allocate the GHG from CHP plants, two of different methods which were Alternative Generation Method and Power Bonus Method, have been investigated. The carbon intensity of power production in district energy plants ($0.43tonCO_2e/MWh$) was relatively lower than conventional gas-fired power plants ($0.52tonCO_2e/MWh$). Secondly we assessed the cost effectiveness of reduction by district energy sector compared to the other means using TIMES model method. We find that GHG marginal abatement cost of 'expand CHP' scenario (-$134/ton$CO_2$) is even below than renewable energy scenario such as photovoltaic power generation ($87/ton$CO_2$). Finally the GHG emission reduction potential was reviewed on the projected GHG emission emitted when the same amount of energy produced in combination of conventional power plants and individual boilers as substitution of district energy. It showed there were 10.1~41.8% of GHG emission reduction potential in district energy compared to the combination of conventional power plants and individual boilers.

• Journal of Korea Trade
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• v.25 no.3
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• pp.153-168
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• 2021

Purpose - In this study, we aim to explore new distribution strategies for sustainable growth in the era of the 4th industrial revolution, focusing on SMEs (small and medium-sized enterprises) in Korea, and suggest ways to upgrade the government's official distribution channel to the next level. Design/methodology - First of all, this paper explored the prior research, the current status of sales support for SMEs, and the changes in the distribution industry due to COVID-19 pandemic. Based on Moon (2016)'s ABCD strategic model - Agility, Benchmarking, Convergence, and Dedication, the study then derived directions in which official distribution channels should move and the new distribution strategy for Korean SMEs to secure competitive advantage. Findings - First, in terms of 'Agility', in order to upgrade official distribution channels, which are currently at some competitive disadvantages compared to private distribution companies, we must quickly introduce technologies for the 4th industrial revolution, such as AI, Big Data, etc., and establish precise strategies to strengthen the capabilities of SMEs. Second, in terms of 'Benchmarking', the use of "Chamelezones" has been increasing to enhance the competitiveness of offline stores in line with recent ontact trends. Therefore, official distribution channels should also benchmark such cases, strengthening their competitiveness by utilizing offline spaces more efficiently and effectively. Third, in terms of 'Convergence', in line with the rapidly changing trend of the times, official distribution channels should also promote active partnerships with media commerce, e-commerce and ICT platforms, as well as cooperation with private retailers, and focus on creating synergy effects through them. Finally, from the perspective of 'Dedication', digitalization should be promoted step by step, finding the sector that can accelerate digital among the value chains of official distribution channels, and continuing to discuss how to digitize it realistically. Originality/value - Based on this analysis, we have presented strategies and implications for innovating official distribution channels for SMEs, which will contribute to enhancing the competitive advantage of official distribution channels in the post COVID-19 pandemic era.

• Journal of Creative Information Culture
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• v.5 no.3
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• pp.275-283
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• 2019

The fourth industrial revolution is emerging as the talk of the times. The industrial structure is changing greatly from the past, as well as the social scene, changing our daily lives. Especially, the importance of the software sector is growing. For students who have to live in this future society, computational thinking is a key capability. In order to achieve this goal, this study was carried out in the following steps. First, we organized a SW education convergence program based on life-oriented aspects. Second, the configured program was applied to the site to verify the effectiveness of computational thinking. The results of this study show that the experimental group has 32 points better than the pre-test, and the comparative group has about 2 points better. The statistical significance probability was a significant difference of .028. The results of this study may be used as a reference for the training of SW convergence education and future talent in the future.

• Journal of Digital Convergence
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• v.16 no.5
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• pp.213-220
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• 2018

The automobile industry in Korea is a very large industrial sector. Nowadays, as the interest in low carbon green growth grows all over the world, it is time to actively secure future competitiveness of the automobile industry. Therefore, it is essential to study consumer attitudes and intentions for electric vehicles at the time when technological and social changes are expected. This study was conducted to investigate the acceptability and preference of electric vehicle for 250 people. The results are as follows. As the monthly income and the number of residents increased, the decision was made to accommodate the electric vehicle. The larger the effect of the electric vehicle on the consumers, the more the electric car decided to accommodate the electric car. In addition, three demographic characteristics (monthly income, number of residents, residence type) showed that there was a difference in satisfaction of electric vehicles. As a result of analyzing the satisfaction level of the electric vehicle, it was found that the electric vehicle has a satisfactory effect on the consumer, the electric vehicle is about 3.5 times more satisfying, and the larger the interest of the electric car is, the more the electric car is about 2.1 times.

• Journal of the Korean earth science society
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• v.34 no.7
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• pp.645-661
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• 2013

The synoptic, thermodynamic, and dynamic characteristics of a heavy snowfall event that occurred in Seoul metropolitan area on 27 to 28 December 2010 was investigated. During this period there was a distinctive case that was identified as a polar low. We analyzed surface and upper level weather charts, snowfall amount, sea surface temperature, satellite imagery, sounding, and the National Center for Environmental Prediction global $1^{\circ}{\times}1^{\circ}$ reanalysis data. The polar low developed in an area where there was strong baroclinicity in the lower level aided by strong conditional instability due to 925 hPa warm air advection and 700 hPa cold air advection. The development mechanism of polar low is due, in part, to the tropopause folding, which advected stratospheric air increasing potential vorticity in mid-level and inducing cyclonic vorticity and convergence in low-level. Eventually clouds developed and there were snowfall total of 10 cm in Seoul metropolitan area and as much as 20 cm in southern parts of Korea. During the snowfall development, there was a $-45^{\circ}C$ cold core at 500 hPa and shortwave maintained $3-5^{\circ}$ separation with surface trough, which favored the development of polar low located in the warm sector and cyclonic advection area. The height of the dynamical tropopause lowered to 700 hPa during the peak development and increase in potential vorticity allowed strong vertical motion to occur. Overall, there was a close relationship between the development of snowfall and tropopause undulation. The heaviest snowfall occurred east of the tropopause folding where strong cyclonic vorticity, vertical motion, and moisture advection all coincided while the polar low was passing through the Korean peninsula.

• Journal of Korean Society of Forest Science
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• v.95 no.6
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• pp.680-689
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• 2006

Introduction of the Special Account for Balanced National Development (SABND) which was represented top-down in 2005 have previous national budget distribution system between central and local government change. A local autonomous entities can choose freely the favorite programs within the total programs in SABND so they can use limited budget efficiently, After induction of this system, budget of the Forest Programs in SABND in 2006 compare to last year has increased by 24.5 percent. That is three times higher than the average rate of total SABND budget, 8.1 percent. This study surveyed propriety of the Forest Programs and hereafter their budget prospect with local government officials in forest sector, 68.7 percent of the respondents recognized that the inclusion of the Forest Programs in SABND is proper. The most preferred Forest Programs are making Urban Forests and their Management and making Facilities for Forest Recreation. And the most non-preferred Forest Programs are complementing the Lumberyard Facility of the Forestry Association, making the Exhibition of Wood Products and making the Base for the Seedling Production. When Forest Programs are adjusted in the future, these programs above mentioned should be exempted from the SABND. because the non-preferred programs as well as the small budget programs On the prospect of the future budget, 81.1 percent of the local government officials in forest sector answered that it will be the same with the current or increasing, In the short term, the budget of the Forest Program in SABND is expected to increase.

• Journal of Korea Technology Innovation Society
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• v.10 no.3
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• pp.555-579
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• 2007

This study analysed theory and application of holistic innovation policy in the 3rd generation innovation policy with cases of Finland and Korea. Innovation policy areas of both countries are expanding from simple goal of economic development to extensive goals such as sustainable development, quality of life, balanced growth etc. Also administrative system changed in order to let technical innovation on the center of national operation and reorganized relation and structure of relative policies like manpower, education, region policy. Particularly, Korea is in embryo standing for S&T driven society since Noh's government. But, there are differences in embodiment degree and feature between both countries. Finland reinvigorate field of public opinion due to corporatism tradition as a Scandinavian institution. Government support system developed co-program and co-policy beyond territory of individual ministry to raise policy effectiveness. However, concept of the Korean innovation policy is ahead of the times but maintained framework of developing country. And there is no active participation of private sector and civil society because transition process accomplished on the top-down method, It could hardly progress toward transition in spite of various efforts to carry out a reform.

• Journal of Animal Environmental Science
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• v.14 no.1
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• pp.23-30
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• 2008

The objective of this study was to estimate the optimum scale of PLMTP (Public Livestock Manure Treatment Plant) for the efficient management of public sector by long-run cost function. An economic analysis was performed using the survey of 52 PLMTP records collected by Ministry of Environment in 2007. The main results obtained in this study can be summed up as follows. The optimum scale under given environmental conditions turned out to be $180{\sim}200m^3$/day which is almost $1.5{\sim}1.6$ times of the average scale of sample plants, $146m^3$/day. This gap between the optimum and current scale suggests that there remains the possibility of further expansion of scale.