• Journal of Life Science
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• v.23 no.11
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• pp.1365-1370
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• 2013

Immobilized cellulase on weak ion exchange resin showed a typical Langmuir adsorption isotherm. Immobilized cellulase had better stability with respect to pH and temperature than free cellulase. Kinetics of thermal inactivation on free and immobilized cellulase followed first order rate, and immobilized cellulase had a longer half-life than free cellulase. The initial rate method was used to characterize the kinetic parameters of free and immobilized enzyme. The Michaelis-Menten constant $K_m$ was higher for the immobilized enzyme than it was for the free enzyme. The effect of the recirculation rate on cellulose degradation was studied in a recycling packed-bed reactor. In a continuous packed-bed reactor, the increasing flow rate of cellulose decreased the conversion efficiency of cellulose at different input lactose concentrations. Continuous operation for five days was conducted to investigate the stability of long term operation. The retained activity of the immobilized enzymes was 48% after seven days of operation.

• Journal of Environmental Science International
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• v.5 no.3
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• pp.361-367
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• 1996

An inverse fluidized-bed biofilm reactor (IFBBR) was used for the treatment of highly-emulsified oily wastewater. When the concentration of biomass which was cultivated in the synthetic wastewater reached to 6000 mg/1, the oily wastewater was employed to the reactor with a input COD concentration range of 50 mg/1 to 1900 mg/l. Virtually the IFBBR showed a high stability during the long operation period although soma fluctuation was observed. The COD removal efficiency was maintained over 9% under the condition that organic loading rate should be controlled under the value of 1.5 kgCOD/$m^3$/day, and F/M ratio is 1.0 kgCOD/kgVSS/day at $22{\circ}C$ and HRT of 12 hrs. As increasing organic loading rates, the biomass concentration was decreased steadily with decreasing of biofilm dry density rather than biofilm thickness. Based on the experimental jesuits, it was suggested that the decrease in biofilm dry density was caused by a loss of biomass inside the biofilm.

• Journal of Environmental Science International
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• v.4 no.3
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• pp.221-228
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• 1995

Stability of reactor and effect on biofilm characteristics were investigated by varying the hydraulic residence time in an inverse fluidized bed biofilm reactor(IFBBR). The SCOD removal efficiency was maintained above 90 % in the HRT range of 12hr to 2hr, but the TCOD removal efficiency was dropped down to 50% because of biomass detachment from overgrown bioparticles. The reactor was stably operated up to the conditions of HRT of 2hr and F/M ratio of 4.5kgCOD/$m^3$/day, but above the range there was an abrupt increase of filamentous microorganisms. The optimum biofilm thickness and the biofilm dry density in this experiment were shown as $200\mu\textrm{m}$ and $0.08 g/cm^3$, respectively. The substrate removal rate of this system was found as 1st order because the biofilm was maintained slightly thin by the increased hydraulic loading rate.

• Environmental Engineering Research
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• v.19 no.4
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• pp.355-361
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• 2014

The wastewater treatment with a two-phase expanded granular sludge bed (EGSB) system for anaerobic degradation of acetate, benzoate, terephtalate and p-toluate from purified terephtalic acid (PTA) production was studied. The feasibility and effectiveness of the system was evaluated in terms of organic oxidation by chemical oxygen demand (COD), gas production, bacterial adaptability and stability in the granular sludge. Average removal efficiencies 93.5% and 72.7% were achieved in the EGSB reactors under volumetric loading rates of $1.0-15kg-COD/m^3/day$ and terephtalate and p-toluate of 351-526 mg/L, respectively. Gas production reached total methane production rate of 0.30 L/g-COD under these conditions in the sequential EGSB reactor system. Higher strength influent COD concentration above 4.8 g-COD/L related to field conditions was fed to observe the disturbance of the EGSB reactors.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.04a
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• pp.163-167
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• 2007

Silver is widely used for catalytic decomposition of hydrogen peroxide, but start-up at room temperature is difficult and cannot withstand at high temperature. In this paper, to overcome these short-comings, a dual catalytic bed which consists of a vaporizer catalyst and a high temperature catalyst was studied. Platinum was selected as the vaporizer catalyst and perovskite type catalyst was selected for the high temperature catalyst. Preliminary test demonstrated start-up capability with non-preheating at room temperature and good thermal stability at high temperature.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2519-2523
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• 2008

When constructing a high-speed railroad, the reduction of the distance between track centers and the width of track bed will save the construction cost. However the shortening the distance between track centers may cause the stability problems due to higher wind pressure. Therefore the extensive technical review and aerodynamical study should be performed to determine the adequate distance between track centers. In this study, the impact that the increase in wind pressure due to the change of aerodynamic phenomena with the change of the distance between track centers may have on two trains passing by each other was predicted, and the stability of train operation was analyzed in order to review the distance between track centers suitable to Honam HSR trains. We conducted the parametric study of the effects of train wind on the running stability.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.119-123
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• 2010

Causes of the levee collapse are directly or indirectly associated with geotechnical engineering as well as hydraulics. In this paper, literature survey and analysis were conducted to present the alternatives in geotechnical engineering issues for rational levee design. The alternatives include the reasonable river-bed soil utilization and precautions of numerical analysis and slope stability analysis, disruption type and improvement method of drainage facility.

• Journal of the Korean Society for Precision Engineering
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• v.11 no.1
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• pp.89-96
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• 1994

This study is to develop a new composite material, a mixture of epoxy resin and granite aggergates which is called Expoxy-Granite, to overcome the inherent disadvantages of conventional materials commonly used as a bed structure material of long-term dimensional/ thermal stability. Under the various manufacturing conditions which could be formulated through experimental investigation, we have constructed 6 kinds of Epoxy-Granite structure models having one fifth the size of the ultra-precision machine tool bed structure. They are compared with cast iron and pure granite models through the dynamic test and the thermal deformation test. Both in the steel ball dropping test and in the forced vibration test, three types of epoxy-granite models made in this study have shown much better dynamic characteristics than the cast iron model and almost the same characteristics as compared with the pure granite model. In the thermal deformation test the above composite materials have also represented lower thermal displacements in the vertical direction of each model as compared with other specimens. It is therefore seen that the epoxy-granite complsite material can be applied to the construction of high-precision machine tool bed, instead of cast iron or pure granite.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.113-116
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• 2003

To maximize the productivity in machining molds and dies, machine tools should operate at high speeds. During the high speed operation of moving frames or spindles, vibration problems are apt to occur if the machine tool structures are made of conventional steel materials with inferior damping characteristics. However, self-excited vibration or chatter is bound to occur during high speed machining when cutting speed exceeds the stability limit of machine tool. Chatter is undesirable because of its adverse effect on surface finish, machining accuracy, and tool lift. Furthermore, chatter is a major cause of reducing production rate because, if no remedy can be found, metal removal rates have to be lowered until vibration-free performances is obtained. Also, the resonant vibration of machine tools frequently occurs when operating frequency approaches one of their natural frequencies because machine tools have several natural frequencies due to their many continuous structural elements. However, these vibration problems are closely related to damping characteristics of machine tool structures. This paper presents the use of polymer concrete and sandwich structures to overcome vibration problems. The polymer concrete has high potential for machine tool bed due to its good damping characteristics with moderate stiffness. In this study, a polymer concrete bed combined with welded steel structure i.e., a hybrid structure was designed and manufactured for a high-speed gantry-type milling. Also. its dynamic characteristics were measured by modal tests.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.12 no.3
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• pp.83-97
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• 2009

The objects of study is to propose criteria for physical river disturbance assessment and as case study to show the application results for river improvement. For this purpose, the river disturbance assessment method for past disturbance process and the present-day potential natural state of stream is proposed. To assess the disturbance of the Youngcheon River caused by river improvement, One ares of Nam River was selected for the reference reach and two areas of Youngcheon River were selected for the comparison reach. And these reaches were surveyed and analyzed according to applying criteria of the river disturbances assessment. The assessment indices were physical factors as like epifaunal (bottom), embededness, velocity/depth regime, sediment deposition, channel flow status, channel alteration, frequency of riffles, bank stability, vegetative protection and riparian zone etc. The results showed that physical river environment in Youngcheon River area was disturbed by artificial revetment and bed excavation, consequently this disturbance give rise to impact of ecosystem in river. Hereafter, the criteria for river disturbance assessment are needed to consider various river characters as bed materials and bed slop etc.