• Analytical Science and Technology
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• v.21 no.6
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• pp.553-561
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• 2008

$CNT/TiO_2$ composites were prepared by using multiwall carbon nanotubes (MWCNT) and various titanium alkoxide precursors. The composites were comprehensively characterized by scanning electron microscopy (SEM), field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), energy dispersive X-ray analysis (EDX) and UV-vis absorption spectroscopy. The photoactivity of the prepared materials under UV irradiation, was tested using the conversion of MB from model aqueous solution. Finally, according to the results of methylene blue (MB) removal experiment, we could see that sample CTOS have better MB removal effect than samples CTIP and CTPP.

• Journal of Adhesion and Interface
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• v.25 no.1
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• pp.143-151
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• 2024

Organic photovoltaics (OPVs) have shown great potential as a new generation of energy harvesters because they possess many unique properties, including mechanical flexibility, lightweight, semi-transparency, and low-fabrication costs. Recent advancements in molecular structure and device engineering have led to achieving power conversion efficiency (PCE) exceeding 19%. However, these highly efficient active layer materials have been hampered in their commercialization by complex synthesis steps that result in high manufacturing costs. To address this issue, research is actively underway on low-cost active layer materials with simple structures. This paper introduces such cost-effective active layer materials and strategies for their synthesis.

• Korean Journal of Agricultural Science
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• v.50 no.4
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• pp.653-661
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• 2023

Phytase enhances phosphorus availability in pig diets by breaking down phytic acid, which is challenging for animals to digest. This study aimed to assess the impact of dietary phytase supplementation on the growth performance, nutrient digestibility, and fecal score of growing pigs. Sixty-four growing pigs ([Yorkshire × Landrace] × Duroc, average body weight 21.20 ± 0.18 kg) were randomly assigned to one of two treatment groups. The dietary treatments were CON, basal diet, and PHY, basal diet + 0.0025% phytase. Results indicated a tendency for increased average daily gain in the phytase-supplemented diet group (p < 0.10) compared to the control diet group. The average daily feed intake and feed conversion ratio were not affected by the addition of 0.0025% phytase. Furthermore, dry matter digestibility, nitrogen content, and digestible energy were not influenced (p > 0.05) by phytase supplementation. Fecal score remained similar (p > 0.05) in growing pigs fed phytase-supplemented and control diets. These findings suggest that supplementing the diet of growing pigs with 0.0025% phytase may lead to improved average daily gain without adverse effects on nutrient digestibility and fecal score. This implies the potential to enhance growth performance without compromising overall health or digestion in pigs. Further investigations into the optimal levels of phytase supplementation for growing pigs are recommended.

• Fisheries and Aquatic Sciences
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• v.27 no.5
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• pp.283-293
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• 2024

Mahseer (Tor soro) growth performance tends to be slow, necessitating further development and intensification of cultivation. One way to develop aquaculture intensification is to manipulate cultivation containers to create optimal environmental conditions for the mahseer to grow. This study aimed to examine the body performance and growth performance of mahseer reared in different colored containers. Experimental research with completely randomized design was employed, with four colored container treatments namely treatment A (transparent), B (green), C (blue), and D (black), with four replications in each treatment. Findings indicate that different rearing media colors had significant effect on absolute length (4.68 ± 0.24 cm), absolute weight (1.58 ± 0.35 g), specific growth rate (2.17 ± 0.38%), feed conversion ratio (2.87 ± 0.04), survival rate (100 ± 0.00%), gross energy (3,816 ± 65.05 cal/g), and body proximate. Physiologically, mahseer fish bred using blue and black containers tend to be more resistant to stress.The best body performance and growth performance were observed in the blue and black colored containers.

• Korean Journal of Agricultural Science
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• v.50 no.3
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• pp.391-398
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• 2023

Garlic powder (GP) was supplemented in the diet to assess the growth efficiency, nutritional retention, and fecal score of growing pigs. In total, 80 growing pigs ([Yorkshire × Landrace] × Duroc) were arbitrarily allotted (22.04 ± 0.56 kg primary average body weight) to two different trial groups with eight repetitions (three males and two females) in each pen for the 42-day trial. The dietary treatment consisted of control (CON, basal diet), which included 0.2% GP (TRT1). Growing pigs fed the GP diet exhibited an increase (p < 0.05) in body weight on day 42 and a lower (p < 0.05) overall feed conversion ratio compared to the CON pigs; however, the average daily gain and feed intake showed no difference (p > 0.05). Additionally, nutrient utilization of dry matter was greater (p < 0.05) in the GP-supplemented diet group than in the CON group. The feeding methods did not adversely affect the nitrogen and energy utilization and the fecal score significantly (p > 0.05). In summary, growing pigs fed the GP diet showed increased growth and nutritional utilization, and no adverse impact on the fecal score; thus, it could be utilized as a stimulant for improved growth performance.

• Ocean and Polar Research
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• v.34 no.4
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• pp.365-384
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• 2012

Microalgae are photosynthetic microorganisms that are highly productive in the presence of basic renewable natural sources (light, $CO_2$, water and nutrients). They can synthesize lipids, carbohydrates and proteins in a small number of days. Subsequently, these carbon-captured products can be processed into both biofuels and valuable co-products. Additionally, microalgae would be an ideal feedstock for replacing land-based food crops with cellular products as high energy density transportation fuels. These microscopic organisms could contribute a significant amount of renewable energy on a global scale. In Korea, microalgae biofuel research was common in the early 1990s. The research activities were unfortunately stopped due to limited governmental funds and low petroleum prices. Interest in algal biofuels in Korea has been growing recently due to an increased concern over oil prices, energy security, greenhouse gas emissions, and the potential for other biofuel feedstock to compete for limited agricultural resources. The high productivity of microalgae suggests that much of the Korean transportation fuel requirements can be met by biofuels at a production cost competitive with the increasing cost of petroleum seen in early 2008. At this time, the development of microlalgal biomass production technology remains in its infancy. This study reviewed microalgae culture systems and biomass production, harvesting, oil extraction, conversion, and technoeconomical bottlenecks. Many technical and economic barriers to using microalgal biofuels need to be overcome before mass production of microalgal-derived fuel substitutes is possible. However, serious efforts to overcome these barriers could become a large-scale commercial reality. Overall, this study provides a brief overview of the past few decades of global microalgal research.

• Clean Technology
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• v.7 no.1
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• pp.43-49
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• 2001

To meet $CO_2$ emission regulation, this study describes the present state of $CO_2$ reduction technology and the effect of the regulation on power industry. In Japan, R&D investment is actively continuing through a long-term R&D project, along with trying to meet the reduction demand by the ways of energy saving and abroad business. EU has made a lot of investments in increasing the efficiency of power generation and developing alternative energy sources. The US is making provision of the portion of reduction by using energy saving program and emission trading, and the current DOE-driven program is addressing the development of cost-effective power systems. In the country, the research to reduce $CO_2$ emission has been mainly driven by the government and research institute supported by the government. Meanwhile, if the reduction obligation imposed on Portugal which is the least strict condition will be enforced in Korea, it is likely that about 50 running power plants should be stopped or shut down after 2015, in spite of voluntary reduction efforts such as conversion to clean fuels, etc. according to the government's long-term electric power need and supply plan.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2002.11a
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• pp.171-184
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• 2002

Approx. 200,000 bpd vacuum residue oil is produced from oil refineries in Korea. These are supplying to use asphalt, high sulfur fuel oil, and upgrading at the residue hydro-desulfurization unit. Vacuum residue oil has high energy content, however high sulfur content and high concentration of heavy metals represent improper low grade fuel. To meet growing demand for effective utilization of vacuum residue oil from refineries, recently some of the oil refinery industries in Korea, such as SK oil refinery and LG Caltex refinery, have already proceeded feasibility study to construct 435-500 MWe IGCC power plant and hydrogen production facilities. Recently, KIER(Korea Institute of Energy Research) are studing on the Vacuum Residue gasification process using an oxygen-blown entrained-flow gasifier. The experiment runs were evaluated under the reaction temperature : 1,100~1,25$0^{\circ}C$, reaction pressure : 1~6kg/$\textrm{cm}^2$G, oxygen/V.R ratio : 0.8~0.9 and steam/V.R ratio : 0.4-0.5. Experimental results show the syngas composition(CO+H$_2$) : 85~93%, syngas flow rate : 50~110Mm$^3$/hr, heating value : 2,300~3,000 ㎉/Nm$^3$, carbon conversion : 65~92, cold gas efficiency : 60~70%. Also equilibrium modeling was used to predict the vacuum residue gasification process and the predicted values were compared reasonably well with experimental data.

• 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.

• Journal of Energy Engineering
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• v.12 no.1
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• pp.49-57
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• 2003

Approx. 200.000 bpd vacuum residue oil is produced from oil refineries in Korea, and is supplied to use asphalt, high sulfur fuel oil and for upgrading at the residue hydro-desulfurization unit. Vacuum residue oil has high energy content, however its high sulfur content and high concentration of heavy metals represent improper low grade fuel. To meet growing demand for effective utilization of vacuum residue oil from refineries, recently some of the oil refinery industries in Korea, such as SK oil refinery and LG Caltex refinery, have already proceeded feasibility study to construct 435~500 MWe IGCC power plant and hydrogen production facilities. Recently, KIER (Korea Institute of Energy Research) are studying on the Vacuum Residue gasification process using an oxygen-blown entrained-flow gasifier. The experiment runs were evaluated under the reaction temperature: 1.100~l,25$0^{\circ}C$, reaction pressure: 1~6 kg/$\textrm{cm}^2$G, oxygen/V.R ratio: 0.8~0.9 and steam/V.R ratio: 0.4~0.5. Experimental results show the syngas composition (CO+H$_2$): 85~93%, syngas flow rate: 50~l10 Nm$^3$/hr, heating value: 2,300~3,000 k㎈/Nm$^3$, carbon conversion: 65~92, cold gas efficiency: 60~70%. Also equilibrium modeling was used to predict the vacuum residue gasification process and the predicted values were compared reasonably well with experimental data.