• Microbiology and Biotechnology Letters
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• v.26 no.1
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• pp.55-60
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• 1998

For an ideal extractive bioconversion in aqueous two-phase systems, the product has to be preferentially partitioned into the phase opposite to the one in which the biocatalyst is located. Partitioning behaviors of Lactobacillus helveticus IAM 11090 and lactic acid in aqueous two-phase systems composed a polycation, poly(ethylenimine) (PEI), and an uncharged polymer (hydroxyethyl)cellulose (HEC) were investigated. L. helveticus cells were preferentially partitioned to the HEC-rich top phase while about 85% of lactic acid was partitioned to the PEI-rich bottom phase. These results indicate that extraction of charged, low molecular weight products in an aqueous two-phase systems can be promoted by using an oppositely charged polymer as one of the phase-forming polymer. By the ideal partitioning of the cells and lactic acid, an aqueous PEI/HEC two-phase system can be used as a potential system for the extractive lactic acid fermentation of cheese whey.

• Fire Science and Engineering
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• v.26 no.3
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• pp.8-13
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• 2012

This study suggests the water curtain nozzles as the way to protect important wooden cultural properties from an adjacent building fire or a forest fire. They are designed to block off the pyrolysis of timbers which occurs at $200{\sim}250^{\circ}C$ by forming a water curtain with the flow of water that spouts over a certain pressure from the bottom. The existing water curtain nozzles installed at the following sites were examined: NakSan-sa (Temple) in Gangwon-do (Province) and in Muwisa (Temple) in Jeollanam-do (South Province). As a way to improve and complement the system, this study designed nozzles with covers in order not to disrupt the landscape. Connected pipes are elevated and jet water when they are in use. Possible ways to install the connected elevating pipes to jet water effectively were investigated.

• Journal of the Korean Ceramic Society
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• v.41 no.7
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• pp.560-566
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• 2004

To fabricate the continuously porous alumina bodies by multi-extrusion process, carbon powder and ethylene vinyl acetate were used as a pore forming agent and a binder, respectively. As the change of extrusion pass number, reduction ratio as well as the volume fraction of core and tube, the porous alumina bodies having various kind of pore size and porosity could be obtained. The porous bodies showed continuous pore shape, high specific surface as well as high bending strength, which were compared with those of commercial alumina bodies. In-vitro study was carried out using MG-63 osteoblast cells to investigate of their biocompatibility. As a result, the cells grew well on top and bottom as well as inside surface of pore. From the result of in-vivo study of 3-dimensional porous alumina bodies using rats, it was confirmed that any inflammatory response was not found in the subcutaneous tissue around porous body. Also the porous bodies removed from the rats were fully covered with well-developed fibrous tissues and showed the formation of new capillary blood vessels.

• Journal of Technologic Dentistry
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• v.42 no.3
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• pp.281-289
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• 2020

Purpose: This study analyzes the self-efficacy and CAD/CAM practice of dental technology students with the aim of providing data that will be useful for improving CAD/CAM education. Methods: A questionnaire survey on self-efficacy and CAD/CAM practice was given to students who participated in face-to-face classes in the Department of Dental Technology at a college in Daegu and Gyeongsangnam-do. The survey period was two weeks long (June 15, 2020 to July 2, 2020), and 84 students completed the questionnaire. Results: The higher the self-efficacy, the fewer difficulties or mistakes students made in CAD/CAM practice. The most difficult parts of the scanning process were the top and bottom arc operation and the bite match arc insertion. The most difficult part of the design work was the use of (multiple) tools. The difference between the degree of difficulty and the degree of mistakes during the practical course was shown as the margin line setting in the design work. Setting the margin line was not difficult, but the degree of mistakes was nonetheless high. In the CAM process, height control was the most difficult part, but the degree of mistakes did not differ according to students' self-efficacy. Conclusion: Given that higher self-efficacy correlated with fewer difficulties or mistakes in CAD/CAM practice, students should be encouraged to enhance their self-efficacy. This may be done by improving their satisfaction with their major course of study, forming friendly relations with their colleagues, and increasing the ratio of performance rather than observation in CAD/CAM practice.

• The Journal of Engineering Geology
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• v.18 no.4
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• pp.577-586
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• 2008

The formation of acid mine drainage is closely related to water chemistry and ochreous sprecipitates formed at the bottom of creeks because it is initially derived from the possible water-rock interaction in abandoned waste metals at the mine. According to analyses on water, precipitates, and alteration characters of ore metals in Dalseone mine, whitish precipitates formed at pHs above 5 while schwertmannite formed at pH $3{\sim}4$. Water chemistry vary with seasons. The water chemistry of the treatment site measured ir Octoter 2002 is characterized by lower pH, and higher Al, Zn, Cu contents relative to those in March, 2003. In the latter case, As and Cl contents are very high. $^{27}Al$ MAS NMR data show the presence of predominant octahedral Al in whitish precipitates. Metal ore minerals dissolve at margins, cleavage, or comer of crystals where reactive sites are potential. Pyrite dissolves, forming etch pits or smooth faces on the edge.

• Journal of Korea Water Resources Association
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• v.50 no.11
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• pp.795-802
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• 2017

This study shows the assessment methodology for the water resources of subsurface dams. The study area is SSangcheon subsurface dam. It is at the estuary of SSangcheon watershed forming the unconfined alluvial aquifer. there are several candidate area which are geologically similar to it at East coast. The groundwater level was computed by a 2-D FDM model, where the watershed discharge is the input as the infiltration term. The baseflow computed as the mean value of 3 watershed dischrge model is $0.5m^3/sec$. And considering the inflow near the baseflow as the dry season inflow, The groundwater level according to the change of inflow and pumping rate was computed. Specifically, Using the real pumping rate $28000m^3/day$ which is equal to the supply amount of drinking water to Sokcho city, The inflow which induce the descended groundwater level to the bottom of aquifer or the ascended groundwater level that cause the surface flow was eatimated. The simulation for increased pumping rate and additional well construction to increase the water resources, was executed. And at the extreme dry season, available pumping rate was estimated.

• Food Engineering Progress
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• v.14 no.1
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• pp.41-48
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• 2010

An optical method was introduced to investigate the dispersion stability of Saengshik beverages (SB) containing 3.7-11.7% Saengshik powder (SP). Time course changes in backscattering light flux (BSLF) from SB were monitored by a Turbiscan. BSLF in the bottom and top layers of SB increased by forming sediment and foam, respectively, while that in the middle layer decreased by clarifying. With SP levels, sedimentation in SB was retarded, but the height of total sedimentation layer was increased. A logarithmic model was developed to fit to the changes in BSLF with time, showing determination coefficients of 0.979-0.988. The levels of SP in SB influenced the migration speed of the clarification front as well as the numbers of separated layers; 2 layers in SB containing 3.7% SP, 3 in 5.7-9.7%, and 4 in 11.7%. Formation of clear layers started after 17-29 min and continued for 22-53 min. The clarification was retarded most in SB containing 7.7% SP, indicating the most stable SP level for the SB preparation.

• Journal of The Geomorphological Association of Korea
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• v.23 no.3
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• pp.79-92
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• 2016

Samples from two boreholes of coastal dune field at Jangho-ri coast, Gochang was studied. These were analyzed by grain size analysis geochemical analysis, and the application of OSL dating method to understand the development during the Holocene. The boreholes SB8 and SB9 were classified into three different sedimentary layers by their mean grain size and geochemical characteristics. The results revealed that the upper sand layer is equivalent to the present coastal dune layer, which developed since 1,200 years ago; the silt layer in the middle to the dune slack or lagoon sedimentation layer, which developed between 1,200 and 6,000 years ago; and the sand layer at the bottom to the paleo coastal dune that developed between 6,000 and 7,000 years ago. It was proposed that the forming material of current coastal dune was supplied from the sandy flat in coastal area, while the middle silt layer was supplied from the weathered soil of a bed rock by the comparison with material of surrounding area. In the case of coastal dune, concentrated layer of sands were identified which were buried about 300 and 1,200 years ago, which is identified as the little ice age. This study confirmed the development of Jangho-ri coastal dunes after Holocene Climate Optimum period, and it is likely to assist in the understanding of coastal dunes development.

• The Journal of the Korea Contents Association
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• v.22 no.1
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• pp.1-9
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• 2022

The purpose of this study is to comprehensively consider the challenge contents enjoyed based on SNS through the concept of Gamification and MDA framework. Regardless of the top-down and bottom-up divisions, in common, the participants show an active figure leading the creation and enjoyment of contents. As a result of analyzing the challenge contents using the MDA framework, the mechanics of 'relative level', 'challenge with expressive purpose', and 'Paidia rules' were found. This leads to the dynamics of participants who express an inner sense of achievement such as 'selection and competition for better expression' and 'selflessness and superiority', creating an environment where they can continuously participate in the challenge contents. Lastly, looking at the aesthetics of the challenge contents, it can be seen that participants are actively forming a play culture that leads the creation and enjoyment of contents. This phenomenon has resulted in breaking down the hegemony of content creation and distribution, which was the responsibility of society in the field of information transmission and commercial advertising.

• Design & Manufacturing
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• v.16 no.1
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• pp.27-35
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• 2022

Thermoforming is a plastic manufacturing process that applies a force to stretch a film of heated thermoplastic material over an engineered mold to create a 3-dimensional shape. After forming, the shaped part can then be trimmed and finished to specification to meet an end-user's requirements. The process and thermoplastic materials are extremely versatile and can be utilized to manufacture parts for a very wide range of applications. In this study, based on K-BKZ nonlinear viscoelastic model, thermoforming process analysis was performed for an interior room-lamp. The predicted thickness was minimum at the corner of a molded film, and maximum at the center of the bottom. By using the Taguchi method of design of experiments, the effects of process conditions on residual stresses were investigated. The dominant factors were the liner thickness and the film heating time. As the thickness of the liner increased, the residual stress decreased. And it was found that the residual stress decreased significantly when the film heating temperature was higher than the glass transition temperature. A thermoforming mold and a trimming mold were manufactured, and the spring back was investigated through experiments. The dominant factors were film heating time, liner thickness, and lower mold temperature. As the film heating time and liner thickness increased, the spring back decreased. In addition, it was found that the spring back decreased as the lower mold temperature increased.