• Journal of Energy Engineering
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• v.23 no.2
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• pp.93-101
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• 2014

How to determine the extent of national energy security? In this paper, we estimate it by comparative analysis of South Korea and other OECD countries in terms of energy diversity (fuel diversity). Energy security consists of 4 key factors such as availability, accessibility, acceptability, affordability. Especially the importance of accessibility can grow as local imbalance of supply and demand increases. As a proxy of the accessibility, fuel diversity can be a significant indicator to estimate a measure of energy security. In this paper, we use Shannon-Wiener index to measure energy diversity. If fuel diversity increases, the stability of energy security also should increase, because of the smoothing effect to lessen dependence on key energy sources. In 2012 Korean growth rate of H-index (energy diversity) is 18.38%, which is higher than other OECD countries. However, Korean H-index itself is 1.93, lesser than other countries. Shift from oil to coals/gas within fossil fuels has more impact on H-index than weight transition from fossil fuels to renewable energies in Korea. We conclude that more renewable energy is an effective solution to achieve higher energy diversity and ultimately higher energy security as the same as the German case.

• Journal of Animal Science and Technology
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• v.50 no.3
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• pp.407-416
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• 2008

본 연구는 CaCl2 용액의 주사량이 품종별 암사슴의 뿔 발생 유도에 미치는 영향을 구명하기 위하여 꽃사슴, 레드디어 및 엘크 암컷 각 6두에 대해 30% CaCl2 용액의 주사량을 1ml?, 1.5ml? 및 2ml?의 3처리구로 나누어 전두골 좌, 우 양쪽 골막에 3월과 7월 두 차례 주사한 후 사슴뿔 발생 유도율, 사슴뿔 생산량, 발육성적을 조사하였다. 품종별 암사슴의 뿔 발생은 꽃사슴이 1ml? 처리구의 한 마리 한쪽에서만 발생하였고, 레드디어는 2ml? 처리구의 한 마리 한쪽에서만 유도되어 꽃사슴과 레드디어의 뿔 발생 유도율은 8.3%였다. 엘크 암사슴은 1ml? 처리구에서는 뿔 발생이 일어나지 않았으며, 1.5ml?와 2ml? 처리구에서는 모두 뿔 발생이 유도되어 유도율은 67%였다. 뿔 생산량은 꽃사슴의 경우 길이 21cm?이고 무게 70g 이었으며, 레드디어는 길이 18.5cm?에 무게 83g의 뿔을 생산하였다. 엘크는 3월 1.5ml? 처리구의 길이가 평균 34±3cm?이었고 무게는 526~1,008g이며, 2ml? 처리구는 길이가 평균 39±8cm?, 무게는 693~1,379g의 범위에 있었다. 엘크의 2ml? 처리구는 7월에 주사한 것이 뿔 길이와 뿔 생산량에서 3월의 것보다 적었다. 암사슴 뿔의 발육은 엘크의 경우 주사 후 20일경에 길이 0.5~1cm? 정도의 돌기로 자랐고, 40일까지는 유발된 상처와 함께 1~3cm?정도의 완만한 성장을 보였다. 본격적인 성장은 처리 후 60일경이 지나야 일어났고, 120일경에 절각을 하였을 때 뿔 길이는 28~44cm?의 범위에 있었다. 생산된 암사슴 뿔을 세로로 절단하였을 때 전체 길이의 위쪽 70%는 골화가 되지 않은 상태였다. 암사슴의 뿔 발생 유도는 번식성적에는 전혀 영향을 미치지 않았다. 봄에 처리한 사슴의 재생 뿔 발생은 불규칙하게 일어났고, 재생 뿔 발생률은 평균 45%였으며, 주기가 진행될수록 길이와 생산량은 줄어드는 경향을 보였다. 결론적으로 30% CaCl2 용액의 주사량을 조절하여 처리하면 꽃사슴, 레드디어 및 엘크의 암컷에서 뿔 발생을 유도할 수가 있으며, 엘크 암사슴의 뿔 발생 유도를 위한 최적 주사량은 1.5~2ml? 범위였다.

• Korean Journal of Organic Agriculture
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• v.23 no.3
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• pp.469-480
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• 2015

The study was conducted on the effects of time of defoliation on fruit quality of pear (Pyrus pyrifolia Nakai) trees, managing with low-pesticides, and regrowth of stem cuttings in vitro. Treatments included for 40% of uniform defoliation at early-August, end-August, and early-September, as well as control (no defoliation). Defoliation at early-September and control increased growth of water sprouts as well as concentrations of carbohydrates, total nitrogen, and free sugar in one-year old shoots. Defoliation at early-September and control increased fruit yield and mean fruit weight, with high soluble solids content and fruit surface color of $a^*$ observed for both defoliation at end-August and early-September. Defoliation at early-August increased rates of electrolyte leakage in stem cuttings at $-18^{\circ}C$ in vitro. There were no significantly different for germination rates of the cuttings between the treatments at -18 and $-21^{\circ}C$ in vitro, with the highest germination of the cuttings observed for defoliation at early-September and control at $-27^{\circ}C$. Therefore, orchard management should be performed to be minimized for defoliation of the spur leaves until end-August, causing from precipitation and pests.

• Clean Technology
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• v.24 no.4
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• pp.339-347
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• 2018

In order to cope with environmental problems and climate change caused by fossil fuels, renewable energy supply is increasing year by year. Currently, waste energy accounts for 60% of renewable energy production. However, waste has a lower calorific value than fossil fuels and contains various harmful substances, which causes serious problems when applied to power generation boilers. In particular, the chlorine in the waste fuel increases slagging and fouling of boiler heat exchangers, leading to a reduction in thermal efficiency and the main cause of high temperature corrosion, lowering facility operation rate and increasing operating cost. In this study, the high temperature corrosion experiments of superheater materials (ASME SA213/ASTM A213 T2, T12 and T22 alloy steel) by alkali chlorides were conducted, and their corrosion characteristics were analyzed by the weight loss method and SEM-EDS. Experiments show that the higher the temperature and chloride content, the more corrosion occurs, and KCl further corrodes the materials compared to NaCl under the same condition. In addition, the higher the chromium content of the material, the better the corrosion resistance to the alkali chlorides.

• Korean Journal of Environmental Agriculture
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• v.42 no.3
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• pp.211-219
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• 2023

Nutrient balance is an environmental indicator for assessing the potential of sustainable agriculture. Improving the use of arable land is crucial for reducing the nutrient balance. This study monitored soil water content, seepage water, crop growth, and nutrient balance in weighing lysimeters during forage barley (Hordeum vulgare L., "Yeongyang") cultivation from October to April. The study was conducted from 2020 to 2022, and the treatments included forage barley cultivation (clay loam, CL-FC; sandy loam, SL-FC) and bare soils. During the regeneration period (March to April), the soil moisture contents of bare and forage barley-cultivated soils were approximately 30-40% and 18.1-21.8%, respectively. The daily evapotranspiration of forage barley was 6.09 mm. The nitrogen balances for SL-FC and CL-FC were -0.43 to -2.93 g m^-2 and -0.79 to 0.75 g m^-2, respectively, which can be attributed to the higher nutrient uptake of forage barley in SL-FC than in CL-FC. Consequently, the forage barley cultivation in SL-FC can potentially reduce nutrient leaching during the spring rainy season. Furthermore, nutrient balance can be reduced by cultivating forage crops during the winter season.

• Korean Chemical Engineering Research
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• v.50 no.3
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• pp.492-498
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• 2012

In this study, hydrodynamics such as solid circulation rate and voidage in the desulfurizer and the reaction characteristics of Zn-based solid sorbents were investigated using lab-scale high pressure and high temperature desulfurization process. The continuous HGD (Hot Gas Desulfurization) process consist of a fast fluidized bed type desulfurizer (6.2 m tall pipe of 0.015 m i.d), a bubbling fluidized bed type regenerator (1.6 m tall bed of 0.053 m i.d), a loop-seal and the pressure control valves. The solid circulation rate was measured by varying the slide-gate opening positions, the gas velocities and temperatures of the desulfurizer and the voidage in the desulfurizer was derived by the same way. At the same gas velocities and the same opening positions of the slide gate, the solid circulation rate, which was similar at the temperature of $300^{\circ}C$ and $550^{\circ}C$, was low at those temperatures compared with a room temperature. The voidage in the desulfurizer showed a fast fluidized bed type when the opening positions of the slide gate were 10~20% while that showed a turbulent fluidized bed type when those of slide gate were 30~40%. The reaction characteristics of Zn-based solid sorbent were investigated by different desulfurization temperatures at 20 atm in the continuous operation. The $H_2S$ removal efficiency tended to decrease below the desulfurization temperature of $450^{\circ}C$. Thus, the 10 hour continuous operation has been performed at the desulfurization temperature of $500^{\circ}C$ in order to maintain the high $H_2S$ removal efficiency. During 10 hour continuous operation, the $H_2S$ removal efficiency was above 99.99% because the $H_2S$ concentration after desulfurization was not detected at the inlet $H_2S$ concentration of 5,000 ppmv condition using UV analyzers (Radas2) and the detector tube (GASTEC) which lower detection limit is 1 ppmv.

• Journal of KIISE:Information Networking
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• v.32 no.4
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• pp.483-494
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• 2005

The standard streaming delivery Is mostly based on UDP with no end-to-end congestion control. For this reason, wide usage of multimedia applications in Internet might lead to congested networks. To avoid such a situation, studies on the congestion controlled streaming delivery has been increasingly done after the 1990s. However, by considering only the stability aspect of network, these works ignore the characteristics of multimedia streaming applications. Moreover, most of previous works have no consideration on the network delay which produces an effect on streaming service. In this thesis, in order to overcome limitations of the previous transmission schemes for streaming, we propose a new transmission scheme called 'BEST(Buffer-driven Efficient STreaming)'. The BEST takes a hybrid approach that considers both user-level requirements and network-level requriements. Therefore, the BEST improves the stability of networks by adjusting the sending rate suitable for network status and it also provides the smoothed playback by preventing buffer underflow or overflow. The BEST is designed to consider high-delay networks. Through the simulation, we prove that the BEST satisfies both user-level and network-level requirements in a high-delay network environments.

• Journal of the Korean Association of Geographic Information Studies
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• v.18 no.2
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• pp.161-173
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• 2015

The guarantee of transportation for elderly and handicapped people is increasingly necessary owing to their growing social and economic activity. In March of 2013, a partial amendment to the law for transportation of the vulnerable was made by the government, to make more convenient transport a legal requirement. The amendment describes standards for the installation of transport facilities, and its support available. However, the adjustment of low-floor bus routes is not included. Therefore, low-floor buses are operating without consideration for the handicapped. This study evaluates the current low-floor bus system user experience by considering the residential distribution of vulnerable customers and analyzing their reasons for using public transport. As a result of this work, adjustments to current bus routes are proposed. The residential distribution of vulnerable people has been assessed using the supporting materials of the urban renewal project in Busan City, and their reasons for using public transport have been collected by a survey of the target user groups. The results show that group A, which has good accessibility, was in high demand, but provided the most limited service. Whereas group C, which also has good accessibility but was in low demand, provided its service most frequently. The data show the supply and demand inconsistencies of low-floor buses, and the inefficiency of bus route allocation. Therefore, this study proposes improvements to current methods for the effective operation of low-floor buses.

• Korean Journal of Plant Tissue Culture
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• v.25 no.1
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• pp.63-68
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• 1998

Multiple shoots obtained in MS medium suppler with 5.0 mg/L BA though shoot-tip culture. The frequency of vitrified shoot was lower on Bacto-agar medium than on Gelrite as gelling agent. Addition of activated charcoal at concentrations of 0.1~0.3% reduced vitrification and markedly increased shoot growth, and formation and growth of roots, but significantly reduced the number of shoots formed. The ratio of fresh weight to dry weight was decreased by increasing light intensity and agar concentration. Eight-tenths times of macroelement of MS medium was observed to be effective for shoot formation. Addition of IAA effectively promoted shoot formation in both shoot tip and node-bud explants. Supplement of 5.0 mg/L BA, 0.3 mg/L IAA to MS medium was most effective in shoot proliferation on shoot tip and node-bud explants.Multiple shoots obtained in MS medium suppler with 5.0 mg/L BA though shoot-tip culture. The frequency of vitrified shoot was lower on Bacto-agar medium than on Gelrite as gelling agent. Addition of activated charcoal at concentrations of 0.1~0.3% reduced vitrification and markedly increased shoot growth, and formation and growth of roots, but significantly reduced the number of shoots formed. The ratio of fresh weight to dry weight was decreased by increasing light intensity and agar concentration. Eight-tenths times of macroelement of MS medium was observed to be effective for shoot formation. Addition of IAA effectively promoted shoot formation in both shoot tip and node-bud explants. Supplement of 5.0 mg/L BA, 0.3 mg/L IAA to MS medium was most effective in shoot proliferation on shoot tip and node-bud explants.

• Journal of the Korean Vacuum Society
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• v.16 no.3
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• pp.161-166
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• 2007

Photovoltaic (PV) technology permits the transformation of solar light directly into electricity. For the last five years, the photovoltaic sector has experienced one of the highest growth rates worldwide (over 30% in 2006) and for the next 20 years, the average production growth rate is estimated to be between 27% and 34% annually. Currently the cost of electricity produced using photovoltaic technology is above that for traditional energy sources, but this is expected to fall with technological progress and more efficient production processes. A large scale production of solar grade silicon material of high purity could supply the world demand at a reasonably lower cost. A shift from crystalline silicon to thin film is expected in the future. The technical limit for the conversion efficiency is about 30%. It is assumed that in 2030 thin films will have a major market share (90%) and the share of crystalline cells will have decreased to 10%. Our research at Sungkyunkwan University of South Korea is confined to crystalline silicon solar cell technology. We aim to develop a technology for low cost production of high efficiency silicon solar cell. We have successfully fabricated silicon solar cells of efficiency more than 16% starting with multicrystalline wafers and that of efficiency more than 17% on single crystalline wafers with screen printing metallization. The process of transformation from the first generation to second generation solar cell should be geared up with the entry of new approaches but still silicon seems to remain as the major material for solar cells for many years to come. Local barriers to the implementation of this technology may also keep continuing up to year 2010 and by that time the cost of the solar cell generated power is expected to be 60 cent per watt. Photovoltaic source could establish itself as a clean and sustainable energy alternate to the ever depleting and polluting non-renewable energy resource.