• Proceedings of the Materials Research Society of Korea Conference
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• 2010.05a
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• pp.3.1-3.1
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• 2010

Water splitting reaction using photocatalysts is of great interest in the utilization of solar energy [1]. In the present work, visible light-responsive $TiO_2$ thin films (Vis-$TiO_2$) were prepared by a radio frequency magnetron sputtering (RF-MS) deposition method and applied for the separate evolution of $H_2$ and $O_2$ from water as well as the photofuel cell. Special attentions will be focused on the effect of HF treatment of Vis-$TiO_2$ thin films on their photocatalytic activities. Vis-$TiO_2$ thin films were prepared by an RF-MS method using a calcined $TiO_2$ plate and Ar as the sputtering gas. The Vis-$TiO_2$ thin films were then deposited on the Ti foil substrate with the substrate temperature at 873 K (Vis-$TiO_2$/Ti). Vis-$TiO_2$/Ti thin films were immersed in a 0.045 vol% HF solution at room temperature. The effect of HF treatments on the activity of Vis-$TiO_2$/Ti thin films for the photocatalytic water splitting reaction have been investigated. Vis-$TiO_2$/Ti thin films treated with HF solution (HF-Vis-$TiO_2$/Ti) exhibited remarkable enhancement in the photocatalytic activity for $H_2$ evolution from a methanol aqueous solution as well as in the photoelectrochemical performance under visible light irradiation as compared with the untreated Vis-$TiO_2$/Ti thin films. Moreover, Pt-loaded HF-Vis-$TiO_2$/Ti thin films act as efficient and stable photocatalysts for the separate evolution of $H_2$ and $O_2$ from water under visible light irradiation in the presence of chemical bias. Thus, HF treatment was found to be an effective way to improve the photocatalytic activity of Vis-$TiO_2$/Ti thin films. Furthermore, unique separate type photofuel cell was fabricated using a Vis-$TiO_2$ thin film as an electrode, which can generate electrical power under solar light irradiation by using various kinds of biomass derivatives as fuel. It was found that the introduction of an iodine ($I^-/{I_3}^-$) redox solution at the cathode side enables the development of a highly efficient photofuel cell which can utilize a cost-efficient carbon electrode as an alternative to the Pt cathode.

• Membrane Journal
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• v.18 no.1
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• pp.103-107
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• 2008

Membrane process has been focused as an alternative separation process because not only it exhibits a high selectivity compared with a traditional distillation process, but also it is known to be an energy saving separation process. Inorganic membrane, especially zeolite membrane, has been studied since it can be operated in severe conditions compared to the organic membranes. Recently, new zeolite materials are tested as an inorganic membrane material to overcome disadvantages of existing zeolite membranes. Kalsilite can be used as an inorganic membrane material for gas separation and selective water separation from water/organic mixtures because it is expected to be hydrophilic resulted from Si/Al ratio of 1 like zeolite 4A and has a narrow pore size of 0.36 nm. In this study, kalsilite was synthesized by a new economical hydrothermal process using Si : Al : K : $H_2O$ mole ratio of 1 : 1 : 8 : 60. The synthesized kalsilite powder was confirmed by XRD and has a mean diameter of $2.73{\mu}m$. The vapor adsorption test showed the synthesized kalsilite is hydrophilic.

• Environmental and Resource Economics Review
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• v.21 no.1
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• pp.175-210
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• 2012

As London and post-Koyto protocols presumably affect emission of organic waste in Korea in 2012, appropriate treatment of organic waste becomes very important. Organic wastes are regarded as non-point pollutants. It has been criticized that direct emission charges on the emission of non-point pollutants are not effective due to the high uncertainty in the relationship between pollution sources and pollution levels. This study suggests indirect emission charges on production of livestocks or consumption on foods. Furthermore, it is assumed that revenue from the emission charges will be recycled to support biogas production. Biogas can be fueled to produce energy. In order to evaluate potential economic and environmental impacts of recycling the indirect emission charges on organic wastes, a static CGE model was developed. Simulation results of emission charges on the production of livestock show that livestock, agriculture, and food industry will confront relatively high burden while emission charges on consumption of food will affect more broadly and consumers will suffer more. Production charge on livestock sector will lead to higher reduction in GDP and total expenditure relative to the consumption charge. GHGs reduction effect was higher for the consumption charge relative to the production charge. Synthetically, consumption charge on food sector is more desirable as an alternative charge for the emission of organic wastes.

• Fire Science and Engineering
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• v.22 no.1
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• pp.99-104
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• 2008

It is important to understand thermal characteristic as a method to estimate the new materials, because spontaneous ignition characterized by causing combustion in the low temperature without ignition source. If can not find out the thermal characteristics of materials, it is frequent that causes of fires could not be found. The danger level of spontaneous ignition material should be estimated and by closely studying its thermal characteristic. However, RPF(Refuse Paper & Plastic Fuel) is a solid matter and getting increasesa year by year because it is an economy profit as alternative energy for limited fossil fuels. Some time RPF occur a fire in the cases of its production process and conservation. Therefore study for thermal stability and critical ignition temperature of RPF was so imperative that the experiment by means of Bombe Calorimeter, TG-DTA, MS80, SIT-II, and Wire Basket Test was implemented. As a result, RPF had a caloric value 26.4-28.3 MJ/kg, and its initial pyrolysis temperature was $192^{\circ}C$ at heating rate 2 K/min. With the result of analysis by MS 80 which is an instrument measuring microscopic calory, pure RPF not containing water has higher caloric value than RPF containing 20% water. Also, SIT-II which is an instrument of insulated auto-ignition was ignited by $118.5^{\circ}C$. This temperature is lower than that of Wire Basket Test. The critical ignition temperature was calculated by Frank-Kamenetskii equation can cause ignition at $80^{\circ}C$ when conserved in the height of 10 m by the standard of infinity slab.

• International Journal of Highway Engineering
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• v.8 no.3 s.29
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• pp.105-114
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• 2006

A popular alternative to extend the life of aged pavement is asphalt overlay. However, it has a very serious and inherent shortcoming in deterring a reflection crack. Although joint-rehabilitation and stress-relief techniques have been applied to deter such reflection cracks in aged pavement, the techniques had a limited success only in slowing down the progress of a reflection crack. Rubblization technique rubblizes the concrete pavement slab in situ and uses the rubblized slab as the base material. Then, pavement overlay is applied to finish off the rehabilitation of aged pavement. This rubblization technique has the advantage of solving the problem of reflection cracking completely. When rubblization technique is applied, the upper layer of aged concrete pavement is rubblized between 40mm-70mm in depth. However, the lower layer is typically rubblized more than 100mm in depth. Nevertheless, it is difficult to turn the entire concrete pavement of more than 30cm in depth into rubblized aggregate of appropriate size. Thus, a simulation experiment was carried out to find the appropriate rubblized depth, which avoids the reflection cracking and still maintains the function of subbase, by varying the depth of rubblized depth in loom increments of 0cm, 10cm, and 20cm. The result indicated the optimum rubblized depth was 10cm (Lee, 2006). Additionally, a small rubblizinge equipment was developed in order to derive the rubblization technique appropriate for thick concrete pavement. This equipment was tested out on an experimental pavement, which was constructed with the same standard and specification for the road in actual use, by varying its rubblizing head shape and energy as well as the effective area of rubblization. This experiment led to a prototype equipment for rubblization of thick concrete pavement. The prototype was put into use on a highway, undergoing a test construction and monitoring afterwards. This entire process was necessary for the validation of the proposed rubblization technique.

• Journal of Wetlands Research
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• v.13 no.2
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• pp.343-353
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• 2011

Variations of load in both DOM and RDOM of inflowing rivers to lakes were in the range of 5.01-7.29(${\times}10^2$ kg/day) for AD lake and 1.23-3.75(${\times}10^3$ kg/day) for JY lake during the research period excluding the period directly affected by the strong rainy season and the monsoon and typhoon season. We observed a good relationship($R^2$ > 0.8) between SS load and DOM load (including RDOM) in both inflowing rivers to JY lake. Therefore, it was determined that SS would be an alternative parameter with a rapid and energy-efficient method for the analysis of both DOC and RDOC, which require the analytical equipment and a long time period. Both AD lake and JY lake may act as a DOM(including RDOM) source through primary production in the fall season. Because AD lake and JY lake may not act as a DOM buffer zone, both lakes couldn't control the DOM and RDOM in spring before the rainy season. Therefore to improve water quality in downstream rivers is needed to remove pollutants such as DOM and RDOM before inflowing to these lakes in upstream rivers, or to have the unique landscape of wetlands as a buffer zone.

• Land and Housing Review
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• v.3 no.4
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• pp.423-431
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• 2012

The trends of Green growth and environmentally-friendliness came to be the key development indicator for sustaining global environment for the future. Korean government reflected these trends in the main flows of the national development index. Korean construction industry is concentrating investment on fields related to these trends such as technologies for carbon dioxide deduction, materials or products for environmentally-friendly building and alternative energy development, as well. However, efforts to follow these trends during the construction process as a step for production phrase are not being considered enough. In this study, we analysed current status and points to be improved of on-site environment management by surveying major project owners and representatives of the environmental affairs in the leading companies of those fields. Also, we suggested organizational structure and operation model as a solution for enhancing environmentally-friendliness for systematic approach to manage on-site environment in public construction sites. In addition to these solutions, further approaches such as shifting paradigm of project owners and contractors, securing workforce and practical budget for efficient management activities, developing environmental management manuals, setting standards for evaluation of activities are needed for the stable settlement of on-site environmental management.

• Korean Journal of Microbiology
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• v.48 no.3
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• pp.192-199
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• 2012

Microalgal biotechnology has gained prominence because of the ability of microalgae to produce value-added products including biodiesel through photosynthesis. However, carbon and nutrient source is often a limiting factor for microalgal growth leading to higher input costs for sufficient biomass production. Use of municipal wastewater as a low cost alternative to grow microalgae as well as to treat the same has been demonstrated in this study using mini raceway open ponds. Municipal wastewater was collected after primary treatment and microalgae indigenous in the wastewater were encouraged to grow in open raceways under optimum conditions. The mean removal efficiencies of TN, TP, COD-$_{Mn}$, $NH_3$-N after 6 days of retention time was 80.18%, 63.56%, 76.34%, and 96.74% respectively. The 18S rRNA gene analysis of the community revealed the presence of Chlorella vulgaris and Scenedesmus obliquus as the dominant microalgae. In addition, 16S rRNA gene analysis demonstrated that Rhodobacter, Luteimonas, Porphyrobacter, Agrobacterium, and Thauera were present along with the microalgae. From these results, it is concluded that microalgae could be used to effectively treat municipal wastewater without aerobic treatment, which incurs additional energy costs. In addition, municipal wastewater shall also serve as an excellent carbon and nitrogen source for microalgal growth. Moreover, the microalgal biomass shall be utilized for commercial purposes.

• Journal of Animal Science and Technology
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• v.62 no.2
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• pp.180-186
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• 2020

The objective of this study was to determine the effect of replacing corn with soy hulls on nutrient digestibility of growing pigs. Three experimental diets were tested using a 3 × 3 Latin square design using three barrows per group (Landrace × Yorkshire × Duroc, average initial body weight of 36.9 ± 4.0 kg) in individual metabolic cages. The dietary treatments were the control (CON) basal diet (corn-soybean meal based diet), whereas in the test diets, soy hulls were included at 5% (H1), 10% (H2), gradually replacing corn. The daily feed allowance was adjusted to 2.7 times the maintenance requirement for digestible energy (DE) (2.7 × 110 kcal of DE/kg BW^0.75). Intake of crude fiber (CF) was different among treatments (p < 0.05). Pigs fed with H2 diet excreted higher concentrations of dry matter (DM), and CF than pigs fed with H1 diet and basal diet (p < 0.05). Pigs fed with H1 and H2 diets excreted higher concentrations of crude protein (CP) than pigs fed with CON diet (p < 0.05). The apparent total tract digestibility (ATTD) of CF from H1 and H2 diets were higher than CON diet (p < 0.05). Pigs fed with H2 diets were significantly lower (p < 0.05) the ATTD of CP than the pigs fed with CON and H1 diets. The current data suggest that 10% inclusion soy hulls can slightly decrease CP digestibility. However, soy hulls considerably increased CF digestibility.It is concluded that 5% soy hulls may be a usable alternative to corn in growing pig diets.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.32 no.4
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• pp.262-272
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• 2020

A large number of studies on wave breaking have been carried out, and many experimental data have been documented. Moreover, on the basis of various experimental data set, many empirical or semi-empirical formulas based primarily on regression analysis have been proposed to quantitatively estimate wave breaking for engineering applications. However, wave breaking has an inherent variability, which imply that a linear statistical approach such as linear regression analysis might be inadequate. This study presents an alternative nonlinear method using an neural network, one of the machine learning methods, to estimate breaking wave height and breaking depth. The neural network is modeled using Tensorflow, a machine learning open source platform distributed by Google. The neural network is trained by randomly selecting the collected experimental data, and the trained neural network is evaluated using data not used for learning process. The results for wave breaking height and depth predicted by fully trained neural network are more accurate than those obtained by existing empirical formulas. These results show that neural network is an useful tool for the prediction of wave breaking.