• Journal of Life Science
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• v.20 no.11
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• pp.1589-1594
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• 2010

Glutaraldehyde was used to cross-link chitosan beads to immobilize the crude enzyme $\beta$-glucosidase from Exiguobacterium sp. DAU5. The conditions for preparing cross-linking chitosan beads and immobilization such as concentration of glutaradehyde, cross-linking time, immobilization pH and time were optimized. The chitosan beads were cross-linked with 1.5% glutaraldehyde for 1.5 hr. The immobilized $\beta$-glucosidase had an overall yield of 20% and specific activity of 5.22 U/g. The optimized pH and temperature were 9.0 and $55^{\circ}C$, respectively. More than 80% of its activity at pH 7.0-10.0, 80% at $40^{\circ}C$ for 2 hr and 48% at $50^{\circ}C$ for 1 hr, were retained. However, the immobilization product showed higher pH and thermal stabilities than free enzymes. It also showed high hydrolyzing activity on soybean isoflavone glycoside linkage. These results suggest the broad application prospects of immobilization enzymes.

• Journal of the Korean Geotechnical Society
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• v.34 no.7
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• pp.17-27
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• 2018

Sinkholes have occurred in various places around the world and concerns about public safety have been raised in recent years. Particularly, a ground subsidence may occur due to a variety of conditions when developing underground spaces. Ground subsidence refers to the sinking of the Earth's surface caused by the loss of the soil constituting ground due to a certain artificial cause in the ground. Ground subsidence is induced by artificial causes such as the leakage of water supply/sewage pipes and groundwater disturbance, and it is different from a sinkhole, where the sinking of the Earth's surface is induced by the cavity formed due to the melting of limestone in the ground with limestone bedrock. In recent underground development in the urban areas of Korea, damages to surrounding buildings have frequently led to many difficulties with civil complaints and compensation issues, and the collapse of some buildings has resulted in the loss of lives and property. Accordingly, the central government has legislated the Special Act on Underground Safety Management, which will take effect from January 1, 2018. This law specifies an underground safety management system for securing underground safety, under which underground safety impact assessment is performed for projects involving underground excavation work that exceeds a certain size, and safety inspection is regularly performed for underground facilities and the surrounding ground. In this study, the contents of the special act on underground safety management are reviewed, and the direction of development of underground safety policy for preparing preemptive underground safety management preparation and response system is suggested.

• Clean Technology
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• v.17 no.4
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• pp.285-299
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• 2011

As one of the REACH obligations, the extended safety data sheet (eSDS) should be communicated within the supply chain under the REACH Regulation. Based on technical guidance documents published on the ECHAs website and survey of EU's recent REACH-related informations, this paper includes a study on details of how to develop exposure scenarios (ES) such as structure of ES, process of ES develpoment, standard workflows and key input data to develop ES with an introduction of eSDS concept. This paper also contains an overview on operational conditions (OCs) and risk management measures (RMMs) that are what to consider when building an ES. The structure of Chesar (Chemical Safety Assessment and Report tool) developed by European Chemicals Agency (ECHA) is studied with a review of the available exposure estimation tools for workers, environment and consumers. Case example of generic exposure scenario (GES) for organic solvent is presented. To guide Korean EU-exporting companies, their participating roles in three steps of preparing ES are addressed.

• Journal of the Korean Applied Science and Technology
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• v.33 no.4
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• pp.634-646
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• 2016

In this work, modified epoxy resins which were well melted in mild solvent were synthesized and solubility assessment was carried out for synthesized epoxy resins. Bisphenol-A type, phenol novolac type and ortho-cresol novolac type epoxy resins were used and fatty acid, dodecyl phenol (DP) and toluene diisocyanate (TDI) were added for synthesis of modified epoxy resins containing fatty acid (MEFA). Composition was epoxy resin/fatty acid = 1.0/0.5 and fatty acid/DP = 0.25/0.25 by equivalent weight and twelve MEFAs were synthesized according to epoxy resins. Viscosity and solubility were measured for twelve MEFAs. As a result, solubility of MEFA was excellent for mild solvent according to increasement of contents of benzene ring, glycidyl group and carbon number of alkyl group. And physical properties were measured for each coating of paints after preparing transparent paints of MEFA to melt well in mild solvent among twelve MEFAs. As a result, they showed an optimal performance on conditions of equivalent ratio of bisphenol-A type epoxy resin/fatty acid/DP/TDI; 1.0/0.25/0.25/0.5 and equivalent ratio of phenol novolac type epoxy resin/fatty acid/DP; 1.0/0.25/0.25 for drying time, adhesion, hardness, impact resistance and alkali resistance.

• Preventive Nutrition and Food Science
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• v.8 no.2
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• pp.166-172
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• 2003

Calcium lactate (CL) prepared from powdered black snail (PBS) or its ashed powder (ABS), was investigated for ideal manufacturing conditions to optimize color, solubility and sensory quality. Based on the amount of PBS and 100 mL lactic acid (LA), the yields of PBS-CL were 300% and 15 g in 10% LA and 260% and 20 g in 20% LA. Yields of ABS-CL based on the amount ABS and 100 mL LA were 400% and 60 g in 10% LA and 329% and 66 g in 20% LA. Both of the yields were decreased with an increase of the LA concentration on the basis of PBS and ABS amounts, but proportionally increased with the increment in the LA concentration on the basis of LA volume. Optimal preparation times of the dehydrated PBS-CL and ABS-CL were, respectively, 4 hr and 5 hr at 10$0^{\circ}C$, 3 hr and 4 hr at 12$0^{\circ}C$, and 1 hr and 2 hr at 15$0^{\circ}C$, which showed shorter time in preparing the dehydrated ABS-CL. PBS-CL and ABS-CL were confirmed to be Ca($CH_3$CHOH$CO_2$)$_2$ by the analysis results of IR and $^1$H-NMR. Calcium contents of the anhydrous PBS-CL and ABS-CL were individually 15.4% (w/w) and 17.3% (w/w) representing 84.2% and 94.5% or each theoretical value. Colors or PBS-CL and ABS-CL were light yellow and light-greenish white each. Solubilities of PBS- CL and ABS-CL in distilled water at pH 3~8 were 5.43 and 6.11 g/100 mL, respectively, which demonstrated higher mean solubilities rather than the 4.74 g/100 mL of standard CL. Solubilities of PBS-CL (3.14~5.03 g/100 mL) and ABS-CL (4.69~6.05 g/100 mL) against soup soy sauce, 3% brine, Soju (Korean distilled liquor), thick soy sauce, grape juice and orange juice were higher than those of standard CL (2.94~5.84 g/100 mL). ABS-CL was believed to have a wide use range due to its low sourness while different applications of PBS-CL in food are expected due to its mild astringent taste and strong savory taste despite its strong bitter taste as estimated by sensory evaluation.

• Journal of the Korean Society of Food Science and Nutrition
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• v.16 no.3
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• pp.27-34
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• 1987

The present paper was attempted to obtain the basic date concerning a reasonable preparing method and optimum fermentation conditions of Kochujang (Red pepper paste). To establish the standard quality of Kochujang, the chemical compositions and the volatile components of Kochujang was discussed. The native Kochujang collected from 80 households contained 40.51% of moisture, 6.00% of salts, 3.25 % of crude fat, 10.30 % of crude ash, pH 4.79, 9.28ml of tillable acidity. 19.60% of reducing sugar, 179.51 mg/100g of amino nitrogen and 4.43% of total nitrogen. The volatiles of Kochujang were extracted by a steam-distillation under the reduced pressure and determined by gas chromatography-mass spectrometry (GC-MS). Total volatile components identified in the native Kochujang were 46 components, i. e., 30 components in neutral fraction, 8 components in phenolic fraction and 8 components in acidic fraction, respectively. But no components were detected basic fraction.

• The Journal of the Korea Contents Association
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• v.17 no.9
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• pp.449-465
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• 2017

Small and medium-sized company workers are ill-prepared for retirement due to low wages and poor working conditions, as result, are likely to get into poverty in retirement. The purpose of this study is to conduct a case study on the current status of financial and non-financial retirement preparation of the small and medium-sized company workers. The main findings are as follows. First, the small and medium-sized company workers show the anxiety about retirement. Many pre-retirees worry that their retirement savings may not generate enough income in retirement, and the level of benefits paid in public pension is inadequate. Second, they are preparing for retirement in the areas of finance, health, working after retirement and social activity. Third, they are realistic and practical in retirement decisions makings. they are considering household budget downsizing, cutting education costs, the low-waged job choice and cash flow preference in retirement. The safety and reality in preparation for retirement are top considerations. In conclusion, this case study shows that pre-retirees of small and medium-sized companies are seeking diverse retirement solutions. We need to design integrated and practical retirement planning programs to support their specific retirement needs.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.44-45
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• 2010

We are currently conducting studies on culturing and biocompatibility assessment of various cells such as neural stem cells and induced pluripotent stem cells(IPS cells) on carbon nanotube (CNT), on nerve regeneration electrodes, and on silicon wafers with a focus on developing nerve integrated CNT based bio devices for interfacing with living organisms, in order to develop brain-machine interfaces (BMI). In addition, we are carried out the chemical modification of carbon nanotube (mainly SWCNTs)-based bio-nanosensors by the plasma ion irradiation (plasma activation) method, and provide a characteristic evaluation of a bio-nanosensor using bovine serum albumin (BSA)/anti-BSA binding and oligonucleotide hybridization. On the other hand, the researches in the case of "novel plasma" have been widely conducted in the fields of chemistry, solid physics, and nanomaterial science. From the above-mentioned background, we are conducting basic experiments on direct irradiation of body tissues and cells using a micro-spot atmospheric pressure plasma source. The device is a coaxial structure having a tungsten wire installed inside a glass capillary, and a grounded ring electrode wrapped on the outside. The conditions of plasma generation are as follows: applied voltage: 5-9 kV, frequency: 1-3 kHz, helium (He) gas flow: 1-1.5 L/min, and plasma irradiation time: 1-300 sec. The experiment was conducted by preparing a culture medium containing mouse fibroblasts (NIH3T3) on a culture dish. A culture dish irradiated with plasma was introduced into a $CO_2$-incubator. The small animals used in the experiment involving plasma irradiation into living tissue were rat, rabbit, and pick and are deeply anesthetized with the gas anesthesia. According to the dependency of cell numbers against the plasma irradiation time, when only He gas was flowed, the growth of cells was inhibited as the floatation of cells caused by gas agitation inside the culture was promoted. On the other hand, there was no floatation of cells and healthy growth was observed when plasma was irradiated. Furthermore, in an experiment testing the effects of plasma irradiation on rats that were artificially given burn wounds, no evidence of electric shock injuries was found in the irradiated areas. In fact, the observed evidence of healing and improvements of the burn wounds suggested the presence of healing effects due to the growth factors in the tissues. Therefore, it appears that the interaction due to ion/radicalcollisions causes a substantial effect on the proliferation of growth factors such as epidermal growth factor (EGF), nerve growth factor (NGF), and transforming growth factor (TGF) that are present in the cells.

• Journal of Wetlands Research
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• v.8 no.3
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• pp.79-89
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• 2006

The survival rate and tube number of Monocorophium uenoi, one of the dominant species in Lake Sihwa, was investigated under laboratory condition with salinity gradients (1, 5, 10, 15, 20, 25, 30, 35, 40‰). Another laboratory experiments were conducted to investigate the survival rate of Monocorophium uenoi in sulphide-rich sediment with oxic overlying water, and the effect of amphipod bioturbation on sulphide and oxygen profiles. The survival rate and tube-forming number of the amphipod were high in salinity range of 20 to 30‰. The amphipod survival rate was also high in sulphidic sediment when the water column was oxic. The amphipod bioturbation affected the oxygen and sulphide content in the sediment; oxygen conditions in the upper sediment layers were improved, and simultaneously the concentrations of sulphide were reduced. And their depth was clearly dependent on amphipod density. In Lake Sihwa, previously anoxic bottoms with sulphidic sediment during summer turn oxic with pycnocline disappearance during autumn. Amphipods seem to have the capability to quickly invade such areas, and their tubing of the sediment may play an important role in preparing the sediment for further recolonisation of other macrobenthos.

• Journal of Korean Tunnelling and Underground Space Association
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• v.22 no.3
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• pp.277-291
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• 2020

Shield TBM is a tunnelling method that has a wider range of applications in the poor ground condition compared to conventional tunnels (Drill and Blast). Currently, a 13.3 m large-diameter slurry shield TBM is preparing for construction to pass under the Han River. Shield TBM is divided into slurry and EPB shield TBM, and management items during construction are different depending on each characteristic. In this paper, the equipment type, origin, application case and trouble case were analyzed for slurry shield TBM, which is mainly constructed in soft ground. In addition, 2D and 3D model tests were conducted on the condition of soil depth for the possibility of slurry leakage into front of the equipment, with appropriate chamber pressure. Based on this paper, it proposed to provide basic and reference data for proper excavation surface pressure and chamber pressure during construction of slurry shield TBM under soft ground conditions, and proposed measures to minimize stability and environmental decline due to slurry ejection.