• Korean Journal of Food Science and Technology
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• v.36 no.3
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• pp.432-439
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• 2004

Increase in water vapor barrier properties of sodium alginate films was studied by preparing composite films with fatty acids, i.e., lauric, palmitic, stearic, and oleic acids, and by treatment with 3% $CaCl_{2}$ solution for 3 min. Film thickness, surface color, microstructure, tensile strength (TS), elongation at break (E), water vapor permeability (WVP), water solubility (WS), and sorption isotherm of films were investigated. Microstructure of films observed with SEM was changed by fatty acid and $CaCl_{2}$ treatments. TS decreased 25-70% depending on fatty acid used, and increased 1.5- to 2-fold by $CaCl_{2}$ treatment. E decreased by both fatty acid and $CaCl_{2}$ treatments. Except oleic acid, WVP decreased significantly (p<0.05) by forming composite films with fatty acids, particularly with stearic acid, WVP decreased more than two-fold. WS also decreased by fatty acid and $CaCl_{2}$ treatments. In stearic acid, WS decreased about 30-fold by combined treatment of fatty acid and $CaCl_{2}$. Sorption isotherm showed typical biphasic pattern with deliquescent point of 0.75. Results of isotherms and BET monolayer moisture content indicated hydrophilicity of film decreased by $CaCl_{2}$ treatment.

• Journal of Energy Engineering
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• v.6 no.2
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• pp.176-187
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• 1997

As a way to evaluate the performance of IGCC (Integrated Gasification Combined Cycle) processes, heating values of coal gas as well as plant efficiency were compared for different rank coals and coal feeding methods by employing the static process simulation technique. Performance of the process was compared with coal rank that was varied by three assorted bituminous coals and also by three subbituminous coals, in addition to the two types of feeding techniques, i.e., dry-feeding and slurry-feeding, that are utilized in entrained-bed coal gasifiers. For the verification of the simulation technique, simulated results were compared first with the actual pilot plant data published from Shell and Texaco. The simulation technique was, then, applied to other coals. Result from tests varying coal rank exhibits the trend of improving both heating content of the product gas and plant efficiency with increasing carbon content in coal. The effect of coal rank is more sensitive in slurry-feeding cases compared to the dry-feeding cases. In particular, considering notably lower values in gas heating value and plant efficiency calculated in the slurry-feeding case that uses a subbituminous coal, limited utilization of the slurry-feeding method for subbituminous coals can be expected. From the plant efficiency point of view, dry-feeding method resulted in higher simulated efficiency values by maximum 3% for subbituminous coals and ca. l% for bituminous coals.

• Journal of Environmental Impact Assessment
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• v.16 no.2
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• pp.143-156
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• 2007

This study has researched the management status and the pollution level of water, soil, stream sediments of 11 abandoned coal mines out of a total of 12 within Obong-Dam area except Bukyung mine, which was submerged when constructing Obong-Dam, and selected areas which are in needs to have pollution control facilities in the first place. From the results of examination on the runoff at the waste rock pile and mineheads, the runoff from Sueun mine (pH, Fe, Al), Samwon mine (pH, Al), Wangdo mine (pH, Al), Mose mine (pH, Fe, Al) and Daeryeong mine (pH) exceeded the permissible discharge standards of the water quality, but the water at merging point with Obong-Dam after joined with Doma branch satisfied both Water Quality Standards and Drinking Water Quality Standards. In regard to groundwater contamination, it is found that areas where exceeded the Drinking Water Quality Standards are Wangdo mine (pH), Jangjae mine (pH, Zn), Daeryeong mine (pH) whereas all areas satisfied Soil Contamination Warning Standards of Soil Environmental Conservation Law. When comparing a research result on underwater sediments of branches of abandoned mines to the EPA Guidelines for classification of great lakes harbor sediments, Dongguk Gaerim (Fe), Jungwon mine (Fe), Daebo mine (Mn), Samwon mine (Mn) and Daeryeong mine (Mn) showed mid-level of contamination, whereas Sueun (Fe, Mn), Daebo mine (Fe), Woosung mine (Fe, Mn), Wangdo mine (Fe, Mn), Mose mine (Fe) and Daeryeong mine (Fe) showed high-level of contamination. In addition, contamination levels of underwater sediments in Wangsan and Doma branch where abandoned mine's branches merge together, Wangsan branch showed no contamination at all whereas Doma branch shows mid-level of contamination which reflect the Doma branch is affected by waste rock pile and minehead runoff of the abandoned mines in the Doma branch area. It is concluded that Mose mine and Sueun mine required treatment of acid mine drainage. and Wangdo, Jungwon, and Samwon mines were in need of mine tailing and erosion control work. The Samwon mine additionally required a control system for closed minehead runoff. Although the Samwon mine reached a high concentration of Al, Mn $Ca^{2+}$, $SO{_4}^{2-}$ in the runoff, the levels decreased after it was combined with a tributary. It has been concluded that after further monitoring of the cause of pollution, a preventive measure system may be needed to be built.

• The Journal of Korean Society for Radiation Therapy
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• v.8 no.1
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• pp.41-54
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• 1996

The secondary electrons developed by interaction between primary beam and a tray mounted for blocks in Megavoltage irradiation result in excess soft radiation dose to the surface layer. To reduce this electron contamination, electron filters have been used to be attached under a tray. Various filters with Cu and Al plates in six different thickness and Cu/Al combined plates in 3 different thickness were tested to measure the reduction rate of secondary electron contamination to the surface layer. The measurement to find optimal filter was performed on 6MV linear accelerator in $10 cm{\times}10 cm$ field size and fixed 78.5cm source to measurement points distance from surface to maximum build up point in 2mm intervals. The result was analyzed as the ratio of measured doses with using filters, to standard doses of measured open beam. The result of this study was fellowing : 1. The contaminated low energy radiation were mainly produced by blocking tray. 2. The surface absorbed dose was slowly increased by increasing irradiation field size but rapidly increased at field size above $15cm{\times}15cm$. 3. Al plate upto 2.5mm thickness used as a filter was found to be inadequate due to the failure of reduction of the surface absorbed dose below doses of the under surface upto the maximal build up. Cu 0.5mm plate and Cu 0.28mm/A1 1.5mm compound plate were found to be optimal filters. 4. By using these 2 filters, the absorbed dose to the surface were effectively reduced $5.5\%$ in field size $4cm{\times}4cm,\;11.3\%$ in field size $10cm{\times}10cm,\;22.3\%$ in field size $25cm{\times}25cm$. 5. In field size $10cm{\times}10cm$, the absorbed dose to the surface of irradiation was reduced by setting TSD 20cm at least,. but effective and enough dose reduction could be achieved by setting TSD 30cm as 2 optimal filters used. 6. More surface dose absorbed at TSD less than 7.4cm with a tray and filters together indicated that soft radiation was also developed by filters. 7. The variation of PDD by the different size of irradiation field was minimal as 2 optimal filters used. There was also not different in variation of PDD according to using any of two different filters. 8. PDD was not effected either by various TSD or by using the different filter among two.

• Journal of Korean Society for Atmospheric Environment
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• v.17 no.5
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• pp.425-437
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• 2001

This study is based on the uses meta-analysis methodology to examine the statistical consistency and importance of random variation among results of epidemiologic studies between air pollutants exposure and childhood asthma. Studies for this meta-analysis were conducted by reviewing previous results and by asking researcher active in this field for recommendations. Overall, 10 cases of air pollutants exposures and childhood asthma were reviewed. A variety of statistical methods for meta-analysis have been used to assess the combined effects, to identify heterogeneity, and to provide a single summary risk estimate based on a set of simiar epidemiologic studies. In this study, classification of exposure metircs on air environmental epidemiologic studies are reported for (1) aggravation of childhood asthma by a 50 ppb increase SO$_2$(6 individual studies); (2) aggravation of childhood asthma by a 50 ppb increase NO$_2$(5 individual studies); (3) aggravation of childhood asthma by a 50 ppb increase $O_3$(7 individual studies); (4) aggravation of childhood asthma by a 10$\mu\textrm{g}$/m$^3$increase PM$_{10}$ (4 individual studies); (5) aggravation of childhood asthma by a 1 ppm increase CO (2 individual studies); and (6) comparison of results between a Korean study results and this meta-analytic study. Results of this study indicated that an inverse-variance weighted pooling of the hospital admission risk at a 1ppm increment of CO levels was 1.12% (95% CI : 1.01 ~ 1.24). The hospital admission risk was estimated to increase 5% (95% CI : 1.02~1.08), 6%(95% CI : 1.04~1.09), and 5% (95% CI : 1.02~1.09) with each 50ppb increase of SO$_2$, NO$_2$, and $O_3$, respectively. In addition, our results lead to a small but significant elevation in risk of 2% (RR = 1.02, 95% CI = 1.01~1.04) with each 10$\mu\textrm{g}$/m$^3$increase of PM$_{10}$ among 4 individual studies. We found a small elevation in risk of childhood asthma, and pooled results of 10 epidemiologic studies of childhood asthma using increase a cut-off-point levels of air pollutants showed a few pieces of evidence. The results of this meta-analysis suggested that air pollution associated with an increased incidence of childhood asthma. According to this study, relationship between exposure to air pollutants and childhood asthma in Korea seem to be high than results of this meta-analysis.sis.

• The Journal of the Korea Contents Association
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• v.20 no.7
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• pp.302-315
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• 2020

The issue concerning how to integrate with the needs of sustainable development according to Crime Prevention Through Environmental Design(CPTED) theory still continues in the development process of the third-generation theory at the present stage. In addition, the issue is under worldwide controversy and discussion. What is more noteworthy is that the viewpoints under debate and discussion have an influence on the mutual effect and relationship between the theoretical model and the principles in the theoretical model, and the influence can never be underestimated. After a mastery of the overall context of theoretical development, it is believed in this study that the identity of CPTED theory development can provide a diverse understanding dimension and a communication method between the environment and environmental users. On the basis of identity the development of CPTED theory, the crime prevention design mode of CPTED needs to connect different dimensions of sustainability, with the design goal of livability as the starting point, the Top-down model to adjust the safety of the environment. By no means can the environmental condition be improved by solely relying on the previous physical design method in virtue of Bottom-up model. Therefore, in this study, the identity of CPTED will be set as the core combined with Top-down crime prevention design model to propose a visual proposal for the reconstitution of the theoretical model, rather than supplementing the application of the contents or principles at a certain stage. Hence, it is expected to provide reference and enlightenment for the sustainable development of CPTED theory.

• Tunnel and Underground Space
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• v.24 no.2
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• pp.176-186
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• 2014

Roughness, aperture and filling material of rock joint are widely considered to affect the hydraulic characteristics of joint. Among these factors, in this study, the joint roughness was examined with artificial joint profiles generated by Monte Carlo simulating on the original profiles suggested by Barton and Choubey(1977). Original profiles and revised profiles were combined to establish flow channel models, in which the hydraulic characteristics were analyzed numerically on the basis of minimum aperture changes and flow channel shapes. Maximum flow rate was identified at the growing point of flow area after passing through minimum aperture generated by the two profiles, and it was resulted that maximum flow rate is inversely proportional to minimum aperture. Maximum flow rate per unit area showed different values because flow channel shapes and minimum aperture locations are different in each model. In flow channel, mechanical aperture showed approximately 1.07 ~ 3.00 times larger than hydraulic aperture. In this study, mechanical and hydraulic aperture were concluded to be closely related to $A_i$ value, and their relations can be denoted by $e_m=0.519A^{0.7169_i}$ and $e_h=0.6182A^{0.239}_i$, respectively.

• International Journal of Highway Engineering
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• v.9 no.2 s.32
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• pp.51-62
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• 2007

Recently, the pavement distresses in the bridge deck have seriously affected the durability of bridge deck and driver's safety. The existing asphalt materials have the limitations in reducing the pavement distresses of brides deck. To protect the bridge deck and withstand the high deflection, it is necessary to develop the asphalt materials with good fatigue resistance for bridge deck pavement. The asphalt binder combined with SBS and two other admixtures has been developed for improving the resistance to fatigue cracking, productivity, and workability for bridge deck pavement. Based on the various binder test results, the developed binder is found to be PG 70-34 indicating very higher resistance against fatigue cracking. Fatigue testing, wheel tracking testing, and moisture susceptibility testing have been conducted to evaluate the performance of asphalt mixtures developed in this study. Laboratory test results show that the developed asphalt material has three times higher fatigue lives than the typical modified asphalt mixture. Full scale accelerated testing was also performed on the typical asphalt mixture and newly developed asphalt mixture to evaluate the full scale performance of asphalt mixtures. Test results indicate that the length of cracking on the new materials is only 38% of the typical material at the 250,000 load repetitions.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.2 s.332
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• pp.61-74
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• 2005

Digital Multimedia Broadcasting(DMB) is a reliable multi-service system for reception by mobile and portable receivers. DMB system allows interference-free reception under the conditions of multipath propagation and transmission errors using COFDM modulation scheme, simultaneously, needs powerful channel error's correction ability. Viterbi Decoder for DMB receiver uses punctured convolutional code and needs lots of computations for real-time operation. So, it is desired to design a high speed and low-power hardware scheme for Viterbi decoder. This paper proposes a combined add-compare-select(ACS) and path metric normalization(PMN) unit for computation power. The proposed PMN architecture reduces the problem of the critical path by applying fixed value for selection algorithm due to the comparison tree which has a weak point from structure with the high-speed operation. The proposed ACS uses the decomposition and the pre-computation technique for reducing the complicated degree of the adder, the comparator and multiplexer. According to a simulation result, reduction of area $3.78\%$, power consumption $12.22\%$, maximum gate delay $23.80\%$ occurred from punctured viterbi decoder for DMB system.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.35 no.1
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• pp.13-20
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• 2009

Background In contrast to defects of the mandible and mouth floor region, in the defect of maxilla, the availability of firmly attached oral and nasal mucosal linings is needed. In addition to it, in consider of operation field, operating convenience, and esthetics, reconstruction using prelaminated flap is strongly recommended. Therefore we consider the prelaminated flap through the cases that is reconstructed using prelaminated forearm flap and prelaminated scapular flap. Patients and Methods From 2001 to 2008, in OMFS SNUDH, there were 6 cases that had reconstruction using prelaminated forearm free flap and other 3 cases that had reconstruction using prelaminated scapular flap of maxilla. The average age of patients that were reconstructed using prelaminated forearm free flap was 47.5 years, the average prelaminated period (after $1^{st}$ operation ${\sim}$ until $2^{nd}$ operation) was 51.8 days and the average follow-up period after $2^{nd}$ operation was 35.3 months. As well, the average age of patients that were reconstructed using prelaminated scapular free flap was 37 years, the average prelaminated period (after $1^{st}$ operation ${\sim}$ until $2^{nd}$ operation) was 57 days and the average follow-up period after $2^{nd}$ operation was 42.3 months. Results Except 1 case that were reconstructed using prelaminated scapular flap, we could get firmly attached oral and nasal stable skin(mucosal like) lining, more adequate thickness flap than any other flap and improved esthetic and functional results in the other 8 cases that were reconstructed using prelaminated flap. The complications of the prelaminated forearm flap cases were inconvenient swallowing, sputum, limitation of mouth opening and difficult mastication. It came from flap shrinkage of the flap in some aspect, as well as other combined operations such as mass resection or RND. The difficult point of the reconstruction of prelaminated scapular flap was the possibility of vascular damage at preparation of flap in $2^{nd}$ surgery. The damage could cause the failure of the prelaminated scapular flap. And the skin-lining of the prelaminated flap had limitations, so it is needed to study about the cultured oral epithelium-lining flap instead of the skin-lining flap. Conclusion We considered about advantages, complications and notable things of prelaminated flap through maxillary reconstruction cases using prelaminated forearm flap and prelaminated scapular flap so far. Furthermore, we should go on studying for functional reconstruction of prelaminated fasciomucosal flap using cultured oral epithelium.