• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1998.11a
• /
• pp.17-20
• /
• 1998

Thermal behavior of Flow Pattern Defect (FPD) and Large Pit (LP) in Czochralski Silicon crystals was investigated by applying high temperature ($\geq$1100$^{\circ}C$) annealing and non-agitation Secco etching. For evaluation of the effect of LP upon device performance / yield, DRAM and ASIC devices were fabricated. The results indicate that high temperature annealing generates LPs whereas it decreases FPD density drastically, and LP does not have detrimental effects on the performance /

• Korean Chemical Engineering Research
• /
• v.60 no.3
• /
• pp.468-471
• /
• 2022

The influence of the central axis and the strut supporting the helical ribbon was investigated in a helical ribbon impeller mixing tank through experiments and visualization. As a result, the strut, which is in the transverse direction, turned out to have a significant adverse effect on the mixing performance such as the occurrence of incomplete mixing region from the change of the liquid level. In contrast, the central axis, which in the longitudinal direction, did not show much adverse effects.

• KSBB Journal
• /
• v.4 no.3
• /
• pp.221-228
• /
• 1989

Celluose is an insoluble substrate, therefore, a proper mixing of the cellulose suspension is essential for an effective enzymatic hydrolysis. To study the effect of mixing motion of various enzyme reactors on enzymatic hydrolysis of cellulose, three distinct types of biroreator: vertical impeller type bioreator(VITB), horizontal paddle type bioreactor(HPTB), and tumbling drum type bioreactor(TDTB), were assembled and their performance was compared. The optimal agitation speed was 100rpm for VITB and HPTB, 200rpm for TDTB. The saccharification efficiency of each reactor was compared under the optimal agitation intensity. The highest degree of saccharification was achieved in the case of VITB, especially, at high cellulose concentration. The VITB seems to be the most suitable type of bioreactor that can maintain proper mixing pattern for effective enzyme reaction. In the view of energy consumption, the TDTB showed the lowest value: however, the energy consumption was rapidly increased at high concentration of celluose. To dertermine the most suitable type of bioreactor, the entire process, including substrate cost, substrate concentration, and feasibility of scale-up, needs to be evaluated.

• Journal of Environmental Science International
• /
• v.26 no.6
• /
• pp.711-717
• /
• 2017

Dielectric Barrier Discharge (DBD) plasma is a new technique for use in environmental pollutant degradation, which is characterized by the production of hydroxyl radicals as the primary degradation species. Due to the short lifetime of the chemically active species generated during the plasma reaction, the dissolution of the plasma gas has a significant effect on the reaction performance. The plasma reaction performance can be enhanced by combining the basic plasma reactor with a homogenizer system in which the bubbles are destroyed and turned into micro-bubbles. For this purpose, the improvement of the dissolution of plasma gas was evaluated by measuring the RNO (N-dimethyl-4-nitrosoaniline, an indicator of the generation of OH radicals). Experiments were conducted to evaluate the effects of the diameter, rotation speed, and height of the homogenizer, pore size, and number of the diffuser and the applied voltage on the plasma reaction. The results showed that the RNO removal efficiency of the plasma reactor combined with a homogenizer is two times higher than that of the conventional one. The optimum rotor size and rotation speed of the homogenizer were 15.1 mm, and 19,700 rpm, respectively. Except for the lowest pore size distribution of $10-16{\mu}m$, the pore size of the diffuser showed little effect on RNO removal.

• 한국생물공학회:학술대회논문집
• /
• 2000.04a
• /
• pp.569-571
• /
• 2000

A fiber optic oxygen sensor has been employed to monitor the concentrations of dissolved oxygen in a bioreactor. The characteristics of fiber optic oxygen sensor was investigated, e.g. the dependency of agitation rate on the oxygen measurement and also the dependence of temperature on the performance of fiber optic oxygen sensor etc. We have also applied to monitor the concentrations of dissoved oxygen in real cultivation processes by using the fiber optic oxygens sensor. The fiber optic oxygen sensor can be applied to measure the concentration of metabolites by immobilizing some enzymes, e.g. glucose oxidase and also employed for the environmental technology.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
• /
• 2004.04a
• /
• pp.354-357
• /
• 2004

The addition of oxygenates to diesel fuel can significantly reduce particulate emissions. Dibutyl maleate (DBM) and tripropylene glycol methyl ether (TGME) have been identified as possible additives based on their physicochemical characteristics and performance in engine test. However, their potential environmental impacts are unknown. therefore, practical considerations in the selection of an oxygenate additives should include cost, availability, compatibility with engines and fuel, and, particularly, its overall environmental impact. This study was investigated to determine optimal condition for the analysis of potential diesel oxygenates using SPME technique with GC-FID. Four fibers were compared and CAR/PDMS fiber was found to be the most sensitive when used direct-sampling. An absorption time of 30min and a desorption time of 5min provided to be the most sensitivity. The effects of experimental parameters such as the addition of salts, agitation, absorption time, compositon on the analysis were investigated. Analytical parameter such as linearity was also evaluated.

• Journal of the Korean Society of Industry Convergence
• /
• v.2 no.2
• /
• pp.73-81
• /
• 1999

Shake mixing has been widely used in cell culture. The mixing performance for shake mixing, however, has not been reported quantitatively. The critical circulating frequency and the power consumption for complete suspension of particles, based on the definition of Zwietering, were measured in a shaking vessel containing a solid-liquid system. The critical suspension frequency was correlated by the equation from Baldi's particle suspension model modified with the physical properties of the particles. Critical suspension frequency was correlated as following ; $$N_{JS}={\frac{0.58\;d{_p}^{0.06}(g{\Delta}{\rho}/{\rho}_L)^{0.004}X^{0.03}}{D^{0.35}d^{0.17}{\upsilon}^{0.04}}}$$ The power consumption at the critical suspension condition in the shaking vessel was less than that in an agitated vessel with impeller.

• Microbiology and Biotechnology Letters
• /
• v.21 no.4
• /
• pp.348-353
• /
• 1993

The optimal conditions for operating a moving-aeration bioreactor were determined as 30rpm and 150 (ml/min) of air flow rate, which can yield ca. 7.3 (l/h)of maximum mass transfer coefficient. It was also found that the agitation speed played much much important role than air input rate in oxgen transfer into the medium. $2.6{\times}10^6$ (cells/ml) and 0.6 (ml/l) of maximum cell denisty and IL-2 production were observed in batch cultivation of IL-2 producing BHK cell line. 0.53 (mM/l/h) of oxygen uptake rate was also estimated. The performance of a moving-aeration bioreactor (specific growth rate and oxygen uptake rate, etc.) was superior to other culture systems, such as cell-life and static membrane aeration bioreactors. Ii must be useful to apply this reactor to many culture processes by improving structural limitations in scaling-up the system.

• Journal of Microbiology and Biotechnology
• /
• v.6 no.1
• /
• pp.30-35
• /
• 1996

Distillery wastewater was used in a thermophilic laboratory-scale two stage anaerobic digester to test the effects of the redox potential of the first acidogenic reactor on the performance of the system. The digester consisted of first a acidogenic reactor and the an upflow anaerobic sludge blanket (UASB) reactor. The digestor was operated at a hydraulic retention time (HRT) of 48 h. Under these conditions, about 90% of the chemical oxygen demand as measured by the chromate method ($COD_{cr}$) was removed with a gas production yield of 0.4 l/g-COD removed. The redox potential of the acidogenic reactor was increased when the reactor was purged with nitrogen gas or agitation speed was increased. The increase in reduction potential was accompanied by an increase in acetate production and a decrease in butyrate formation. A similar trend was observed when a small amount of air was introduced into the acidogenic reactor. It is believed that the hydrogen partial pressure in the acidogenic reactor was decreased by the above mentioned treatments. The possible failure of anaerobic digestion processes due to over-loading could be avoided by the above mentioned treatments.

• Journal of Biosystems Engineering
• /
• v.41 no.3
• /
• pp.201-207
• /
• 2016

Purpose: A water-spraying type automatic glochids removal system for cactus (Opuntia humifusa) stem was developed, and its performance was evaluated. The system was developed to reduce intensive human labor in removing glochids from cactus stem skin without inducing damage prior to further processing into value-added products. Methods: The developed system consists of conveyor and water-spraying systems. The conveyor system delivers cactus stems through water-spraying compartments and finally to a collecting box. In order to remove the glochids, rotating nozzles spray water over all areas (i.e., front and back faces and sides) of the cactus skin under controlled water pressure. Operating conditions such as conveyor speed, water pressure, angle of water-spraying nozzles, distance between conveyor belt and rotating nozzles, and angle of cactus flipping slide were adopted from our previous study and applied on the system design and manufacturing. The performance of glochids removal was evaluated by counting the number of glochids on the cactus stem before and after processing on the system. Results: The developed system performed efficiently and effectively under the pre-studied operating conditions except for the angle of cactus flipping slide. The new system had a glochids removal ratio of 94.1% without damaging the cactus skin. Considering the original number (approximately 30-60) of glochids, the remaining number was low (1-4), and most of them were found at the side edge of the cactus stem. This system can remove glochids from 360 cactus stems in 1 hr regardless of cactus size. Conclusions: The performance of the new system in glochids removal without damaging cactus skin is superior to any other existing device (i.e., brush type, rubber-friction type, and agitation type). The system is expected to be applied in cactus (O. humifusa) processing facilities.