• Clean Technology
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• v.26 no.1
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• pp.65-71
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• 2020

Various solar hybrid energy conversion processes, which have both the advantages of renewable energy sources and fossil energy sources, have been developed in the world because stable and predictable energy supplies, such as electricity and natural gas, are necessary for modern societies. In particular, a solar hybrid energy conversion process based on a dual fluidized bed process concept has been expected as the promising solution for sustainable energy supply via thermochemical conversions, such as pyrolysis, combustion, gasification, and so on, because solar thermal energy could be captured and stored in fluidized bed materials. Therefore, the attrition and heat transfer characteristics of silicon carbide and alumina particles used for fluidized bed materials for the solar hybrid energy conversion process were studied in an ASTM D5757 reactor and a bubbling fluidized bed reactor with 0.14m diameter and 2m height. These characteristics of novel fluidized bed materials were compared with those of sand particles which have widely been used as a fluidized bed material in various commercial fluidized bed reactors. The attrition resistances of silicon carbide and alumina particles were higher than those of sand particles while the average values of heat transfer coefficient in the bubbling fluidized bed reactor were in the range of 125 ~ 152 W m^-2K^-1.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.26 no.4
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• pp.233-239
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• 2013

Recently, a number of wind turbines are being installed due to the increase of interest in renewable, environment-friendly energy. Especially, an offshore wind turbine is being watched with keen interest in that it has no difficulty in securing a site and can get high quality of wind, as compared with a wind turbine on land. The offshore wind turbine is transferred to and installed on the site by an offshore floating crane after it was made in a factory on land such as shipyard. At this time, it is important to secure the safety of the turbine because of its huge size and expensive cost. Thus, a dynamic analysis of the offshore wind turbine which is connedted with the offshore floating crane was performed based on the multibody systems dynamics in this study. As a result. it is shown that the analysis can be applied to verify the safety of a method for the transportation and installation of the offshore wind turbine suspended by the crane.

• Journal of Korea Soil Environment Society
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• v.3 no.3
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• pp.55-62
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• 1998

Soils contaminated with hydrocarbons and residual metals can be effectively treated by soil washing. In developing the soil washing process several major effects for separating contaminants from coarse soils progressively improved upon combinations of mining and chemical processing approaches. The pilot-scale soils washing process consists of the four major parts : 1) abrasive scouring, 2) scrubbing action using a washwater that is sometimes augmented by surfactants or other agents, 3) rinsing, and 4) regenerating the contaminated washwater. The plant was designed based upon the treatment capacity > 5 ton/hr on site. The lumpy contaminated soil fractions first experience deagglomeration and desliming passing through a rolling mill pipe. In the second unit the attrition scrubbing module equipped with paddles uses high-energy to remove contaminants from the soils. And a final rinsing system is assembled to separate the washwater containing the contaminants and very fine soils from the washed coarse soils. For recycling the contaminated washwater passes through a washwater clarifier specifically designed for flocculation, sedimentation and gravity separation of fine as well as flotation and separation of oils from the washwater. In order to more rapidly assess the applicability of soil washing at a potential site while minimizing the expense of mobilization and operation, a mobile-type soil washing process which is self-contained upon a trailer will be further developed.

• Journal of the korean academy of Pediatric Dentistry
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• v.41 no.1
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• pp.85-92
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• 2014

Dentigerous cyst is the most common developmental odontogenic cyst of the jaw which is associated with unerupted teeth. Treatment modalities range from enucleation to marsupialization. Enucleation is the process in which the cyst is completely removed, and this is usually indicated for smaller lesions. Larger cysts can be treated by marsupialization, which is a process that consists of making a surgical cavity on the wall of the cyst, emptying its content and maintaining the continuity between the cyst and the oral cavity. This procedure allows decompression of the cyst, regeneration of the bone-defected area, and also lets the wall of the cyst change into normal mucosa. This technique will protect adjacent structures and will promote spontaneous eruption of succedaneous teeth previously surrounded by the cyst. These are two case reports of a 5-year-old and an 11-year-old boy with dentigerous cysts found regarding supernumerary tooth and pulpotomized mandibular primary molars, respectively. Due to the large size of the cysts, both cases were treated with marsupialization. This case report shows that in cases regarding large-sized dentigerous cysts, marsupialization can be an effective surgical technique that promotes spontaneous eruption of cyst-involved succedaneous teeth and the preservation of adjacent teeth.

• Korean Chemical Engineering Research
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• v.47 no.2
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• pp.230-236
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• 2009

Sewage sludge cake(SSC) is seriously concerned because ocean dumping, which is the cheapest treatment method now, will be banned in 2012. On the basis of this reason, recycling of SSC is emphasized to convert the treatment method. One of the method to recycling SSC could be carbonization process which also can be reduced greenhouse gas effectively. And carbonization residue of SSC produced by carbonization process can become a renewable energy source. However, carbonization process has not been evaluated by considering basic operating data such as heating value, yield and fuel ratio. In this study, the basic characteristics of SSC such as proximate analysis, elementary analysis and heating value are analyzed. In carbonization process, the effect of carbonization temperature and time on the residue of SSC are estimated. And the analysis is carried out to obtain basic properties of the residue of SSC. From the result of chemical composition of SSC residue, there is 27% of phosphate in SSC. Phosphate will take a role of reductant to convert from hazardous substance to non-hazardous material. As increased carbonization temperature and time, heating value and yield are decreased but fuel ratio(fixed carbon/volatile combustible) of the residue is increased. In the carbonization process, the optimum temperature and time in carbonization test for SSC can be decided by $250^{\circ}C$ and 15 min, respectively. However, the carbonization residue of SSC can not be deserved to use one of renewable energy sources because the heating value at the optimum condition is relatively low. Hence, it is desirable that SSC can be mixed with other organic waste to carbonize.

• Journal of Korean Society of Forest Science
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• v.70 no.1
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• pp.38-44
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• 1985

These surveys were conducted for the purpose of fundamental data of environmental ecology to save the damage of the fieldmice at the National Park of Mt. Jiri, shown especially in the 5 areas of Jang-dang, U-pyung, Jung-san-ri, Sea-seok and Dae-sung area from October, 1983 to September, 1984 during which the fieldmice were very active. The results were summarized as follows; 1) Fieldmice observed were 3 species: Clethrionomys rufocanus regulus, Apodemus speciosus peninsulae and Apodemus agrarius coreae. 2) Types of fieldmice hole were of 5 types; around the roots of trees, at fallen trees, between rocks and the ground, on the surface of the slope ground, on the surface of the ground. The holes were found mostly around the trees (33.2%). 3) Inhabitant ratio was the highest at Dae-sung area (22.6%). Breeding was the most active in July. 4) Females found in July at Sea-seok area were the most in the number (6.6%). Males found at U-pyung area were the most in July in the number, at Sea-seok area in May, at Dae-sung area in July (5.4%). 5) The weight ranged between 20.3g and 57.4g. Clethrionomys rufocanus regulus was the heaviest (37.8g), Apodemus speciosus peninsulae the next and Apodemus agrarius coreae the highest. The heaviest were those found at Dae-sung area.

• The korean journal of orthodontics
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• v.28 no.3 s.68
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• pp.419-429
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• 1998

This study was carried out in order to study early histologic changes and repair reaction appling to extrusive force for 3rd premolar of adult dogs. After 1 week of extrusive force with elastic chain, one of dogs was sacrified and after 3 weeks retention period, another dog was sacrified. The paraffin sections of samples were stained with Hematoxylin - Eosin and Masson's Trichrome and were examed by light microscopy . The obtained results as follows 1. In Hematoxylin - Eosin and Masson Trichrome stain of control group , the periodontal ligament width was constant from apical third to cervical third of the root and periodontal fiber arrangement was horizontal or oblique in cervical third. oblique in middle third, oblique in apical third of root. in alveolar bone, smooth appearance was shown 2. In Group 1, all periodontal fiber arrangement was oblique toward tooth, and the periodontal ligament width increased Partially PDL was ruptured in apex. In MT stain, immature bone formation was seen at alveolar crest area. Active bone formation was observed along the one side of alveolus, and apical portion of pulp was involved with blood vessel rupture , vacuolization of pulp tissue and hyperemia 3. In Group 2, most periodontal ligament arrangement and PDL width was repaired and fiber density increased. In MT stain, mineralization of immature bone on the alveolar crest was progressed. In pulp, vacuole and hyperemia was diminished and fibrotic change was diminished 4. After 3 week periodontal ligament has more repair ability than pulp tissue. pulp was involved with vacuolization and fibrosis, so it takes more time for repair.

• Journal of Korean Ophthalmic Optics Society
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• v.8 no.1
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• pp.65-71
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• 2003

The corneal epithelium is constantly being shed. The mechanism of corneal desquamation is not fully understood. Apoptosis, programmed cell death, may play a role. Apoptosis can be induced by a number of factors and different mechanisms. The study was performed to examine the apoptotic index induced in human corneal epithelial cells maintained in tissue culture by various apoptotic inducers. Various inducers, recombinant human cytokines($INF{\gamma}$, $TNF{\alpha}$, FASAb), actinomycin D. camptothecin, cycloheximide, dexamethasone and etoposide, were purchased from commercial suppliers. Inducers at manufacturer-recommended concentration were added to the corneal epithelial cells for 48 hours. Cell viability was measured using MTT assay. The cells were then assessed for the level of apoptosis. Morphologic changes and quantification of apoptotic cells were determined and counted under fluorescence microscope after inducers-treated human corneal epithelial (HCE) cells for 48 hours with Hoechst 33342 staining. Annexin V-FITC/PI staining and DePsipher assay. The expression of Fas protein was studied by immunocytochemistry. All inducers induced apoptosis in HCE cells in a dose dependent manner. Actinomycin D. camptothecin and etoposide induced apoptosis at lower than manufacturer-recommended concentration, while cytokines, cycloheximide and dexamethasone induced apoptosis at higher concentrations at the end of 48 hours. All inducers elicited typical apoptotic morphologic changes (chromatin condensation, nucleus fragmentations non-orange-red colored mitochondria) and expresses Fas protein highly. Apoptotic index of HCE cells by these inducers was different from the other cell lines. RNA synthesis inhibitor and topoisomerase inhibitors induced apoptosis at lower concentration than manufacturer-recommended concentration. Cytokines, cycloheximide and dexamethasone were able to produce apoptosis at 10 times higher concentrations. RNA synthesis inhibitor and topoisomerase inhibitors are more sensitive than intracellular receptor-activators in apoptotic induction of HCE cells.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.12
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• pp.804-815
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• 2019

Due to the depletion and environmental problems of fossil fuel, biomass has arisen as an alternative energy source. Biomass is a renewable and carbon-neutral source. However, it is moister and has lower energy density. Therefore, biomass needs thermal chemical conversion processes like gasification, and it does not only produce a flammable gas, called 'syngas', which consists of CO, H2, and CH4, but also some unwanted byproducts such as tars and some particulates. These contaminants are condensed and foul in pipelines, combustion chamber and turbine, causing a deterioration in efficiency. Thus this work attempted to find a method to remove tars and particles from syngas with a filter which adopts a pre-coating technology for preventing blockage of the filter medium. Hydrated limestone powder and activated carbon(wood char) powder were used as the pre-coat materials. The removal efficiency of the tars was 86 % and 80 % with activated carbon(wood char) coating and hydrated limestone coating, respectively.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.4
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• pp.568-574
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• 2020

Recently, the installation of energy storage systems (ESSs) that have a range of functions, such as power stabilization of renewable energy sources, demand control, and frequency regulation, has been increasing annually. On the other hand, since the fire accident of ESS occurred at Gochang Power Test Center in August 2017, 29 fire accidents with significant property losses have occurred, including the Gyeongsan substation and Kunsan PV power plant. Because these fire accidents of ESS are arisen regardless of the season and capacity of ESS, an analysis of the fault characteristics in ESS is required to confirm the causes of the fire accidents accurately and ensure the safety of the ESS. This paper proposes the modeling of ESS using PSCAD/EMTDC S/W to identify the fault characteristics and ensure the safety of the ESS. From the simulation results of fault characteristics based on various scenarios, it is clear that the insulation of ESS may be breakdown due to the largely occurring CMV (common mode voltage). Furthermore, the CMV between the PCS and battery can be reduced, and the insulation breakdown of ESS can be prevented if an SPD (surge protect device) is installed in the battery and PCS sides, respectively.