• 한국환경과학회지
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• 제6권2호
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• pp.113-124
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• 1997

The basic mechanism of the granular sludge formation which is the most important factor in the start-up and stable operators is not confirmed yet. In this study, the effect of granular sludge formation was investigated with the different substrate concentrations and the various ratios of substrate supply/deficiency. The granular sludge formation in the UASB reactor was closely related to the substrate concentrations and the ratio of substrate supply/deficlency The granular sludge formation was not accelerated at low substrate concentration. It was convinced that granular sludge formation was accelerated when the substrate supply with high concentration was stopped at UASB reactor. From this experiment, it was estimated that granular sludge was formed by the combination of hydrogen utilizing bacteria that form hydrogen condition and acid forming bacteria at substrate deficit condition by mutual symbiosis. Though the removal efficiency of organic matter was decreased as the influent substrate concentration was Increased, the higher the influent substrate the better the granular sludge formation.

• 생명과학회지
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• 제5권4호
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• pp.155-161
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• 1995

The effects of substrate concentration, enzyme concentration, reaction temperature, and water content were investigated in intramolecular esterification. This study used cyclohexane as organic solvent, power lipase as enzyme, and benzyl alcohol and octanoic acid as substrate. The initial reaction rate was found to be proportional to enzyme concentration; followed Michaelis-Menten equation for octanoic acid; and was inhibited by benzyl alcohol . The observed initial reaction rate first increased, then decreased with increasing reaction temperature, giving rise to the maximum rate at 20$\circ$. The drop in the reaction rate at higher temperature was to partition equilibrium change of substrate between organic solvent and hydration layer of enzyme molecule in addition to the deactivation by enzyme denaturation. Water layer surrounding enzyme molecule seemed to activate in organic solvent and the realistic reaction was done in the water layer. In the enzymatic reaction in organic solvent, the initial reaction rate was influenced by partition quilibrium of substrate, so the optimum condition of substrate concentration, enzyme concentration, reaction temperature, and water content would give a good design tool.

• Applied Biological Chemistry
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• 제38권3호
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• pp.248-253
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• 1995

참깨박 단백질의 기능개선을 위한 가수분해 조건을 검토한 결과 분리된 참깨박단백질에 대한 각 효소의 최적작용조건은 papain의 경우 pH 6.0, $60^{\circ}C$,효소 대 기질의 비는 기질량에 대해 3%, 기질농도 1.5%에서 최적이었으며, pepsin은 pH 2.0, $50{\sim}60^{\circ}C$, 효소의 농도는 기질량에 대해 3%, 기질농도 1%에서 최적이었다. 그리고 trypsin은 pH 9.0, $60^{\circ}C$, 효소의 농도는 기질량에 대해 1%, 기질의 농도 1%에서 가장 높은 효소작용을 보였다.

• BMB Reports
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• 제37권5호
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• pp.533-537
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• 2004

Previously published kinetic data on the interactions of seventeen different enzymes with their physiological substrates are re-examined in order to understand the connection between ground state binding energy and transition state stabilization of the enzyme-catalyzed reactions. When the substrate ground state binding energies are normalized by the substrate molar volumes, binding of the substrate to the enzyme active site may be thought of as an energy concentration interaction; that is, binding of the substrate ground state brings in a certain concentration of energy. When kinetic data of the enzyme/substrate interactions are analyzed from this point of view, the following relationships are discovered: 1) smaller substrates possess more binding energy concentrations than do larger substrates with the effect dropping off exponentially, 2) larger enzymes (relative to substrate size) bind both the ground and transition states more tightly than smaller enzymes, and 3) high substrate ground state binding energy concentration is associated with greater reaction transition state stabilization. It is proposed that these observations are inconsistent with the conventional (Haldane) view of enzyme catalysis and are better reconciled with the shifting specificity model for enzyme catalysis.

• Journal of Microbiology and Biotechnology
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• 제13권3호
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• pp.332-337
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• 2003

Enzyme kinetics data play a vital role in the design of reactors and control of processes. In the present study, kinetic studies on pectinases were carried out. Partially purified polymethylgalacturonase (PMG) and polygalacturonase (PG) were the two pectinases studied. The plot of initial rate vs. initial substrate concentration did not follow the conventional Michaelis-Menten kinetics, but substrate inhibition was observed. For PMG, maximum rate was attained at an initial pectin concentration of 3 g/l, whereas maximum rate was attained when the initial substrate concentration of 2.5 g/l of polygalacturonic acid for PG I and PG II. The kinetic data were fitted to five different kinetic models to explain the substrate inhibition effect. Among the five models tested, the combined mechanism of protective diffusion limitation of both high and inhibitory substrate concentrations (semi-empirical model) explained the inhibition data with 96-99% confidence interval.

• 한국환경보건학회지
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• 제15권2호
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• pp.59-68
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• 1989

This study was performed employing the two stage aerated submerged biofilter of media pore size 1.5cm and 2cm, and infiuent substrate concentrations were 30.25mg COD/l, 50.1mg COD/l respectively. The purpose was to determine the treatment efficiency at the low concentration infiuent, reaction order and substrate flux with application of variable-order model that was presented by Rittmann and McCarty. . The results are as follows. 1. Treatment efficiency of 1st reactor was about BOD 82% and COD 76%, when effluent concentration was BOD 3.9 ~ 6.8, COD 7.1 ~ 12.5 mg/l, and this effluent concentration didn't satisfy the water quality grade I, II of river and lake. But as treated effluent of 1st reactor with 2nd reactor, we could achieve appropriate water quality, since instillation of 2nd reactor was needed. 2. Difference of media pore size between 1.5cm and 2cm didn't effect significantly to treatment efficiency and since this of 2nd reactor was about BOD 60%, COD 50%, an consideration of economic point of view should be carried out in field application. 3. Reaction order and substrate flux was varied 0.9851~0.9956 and 0.0028~0.0405 mg/$cm^{2} \cdot day$, and the substrate flux was increased as infiuent substrate concentration increased.

• 대한전자공학회논문지
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• 제27권6호
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• pp.895-900
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• 1990

With the MOS device scailing down, the substrate concentration must increase in order to avoid punchthrough leakage current due to the DIBL(Drain Induced Barrier Lowering) effect. However the enhancement of the substrate concentration increases source, drain juntion capacitances and substrate current due to hot elelctron, degrading the speed characteristics and reliability of the MOS devices. In this paper, a new device, called CODE(Channel Only Dopant Enhancement) MOS, an its fabrication are proposed. By comparing the fabricated CODE MOSFET with the conventional device, the improvements on DIBL, substrate current and source, drain juntion capacitances are realized.

• 한국표면공학회지
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• 제52권6호
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• pp.342-349
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• 2019

Titanium nitride(TiN) thin films have been deposited on PEN(Polyethylene naphthalate) substrate by reactive RF(13.56 MHz) magnetron sputtering in a 25% N₂/Ar mixed gas atmosphere. The pulsed DC bias voltage of -50V on substrates was applied with a frequency of 350 kHz, and duty ratio of 40%(1.1 ㎲). The effects of pulsed DC substrate bias voltage on the crystallinity, color, electrical properties of TiN_x films have been investigated using XRD, SEM, XPS and measurement of the electrical properties such as electrical conductivity, carrier concentration, mobility. The deposition rates of TiN_x films was decreased with application of the pulsed DC substrate bias voltage. The TiN_x films deposited without and with pulsed bias of -50V to substrate exhibits gray and gold colors, respectively. XPS depth profiling revealed that the introduction of the substrate bias voltage resulted in decreasing oxygen concentration in TiN_x films, and increasing the electrical conductivities, carrier concentration, and mobility to about 10 times, 5 times, and 2 times degree, respectively.

• 대한환경공학회지
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• 제28권9호
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• pp.911-916
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• 2006

혐기성 미생물에 의한 수소 생산에 있어서 기질 농도와 HRT의 영향에 대하여 3계열로 구분하여 실험을 수행하였다. 계열 I는 HRT가 8시간에서 기질농도를 3에서 27 g-glucose/L로 증가시키면서 실험을 수행하였고, 계열 II는 HRT가 16시간, 계열 3은 HRT가 24시간으로 설정하여 실험을 수행하였다. 연구결과, 수소 생성 수율에 미치는 HRT와 기질 농도의 영향에 대하여 표면분석법에 의하여 분석하였다. 최대 수소 생성 수율은 기질농도 15.4 g/L 및 HRT 9.6시간에서 2.05 mol $H_2/mol$ 글루코오스의 값을 구할 수 있었다. 2 mol $H_2/mol$ 글루코오스의 수소 생성 수율을 얻기 위한 기질농도 및 HRT는 각각 $13{\sim}17$ g/L 및 $5{\sim}14$시간임을 알 수 있었다. 글루코오스의 소모에 따라 유기산의 농도는 증가하였고, 주요 대사산물은 아세트산과 부틸산이었다.

• Electronic Materials Letters
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• 제14권6호
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• pp.749-754
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• 2018

Previous studies have reported on the mechanical robustness and chemical stability of flexible amorphous indium gallium zinc oxide (a-IGZO) thin-film transistors (TFTs) on plastic substrates both in flat and curved states. In this study, we investigate how the polyimide (PI) substrate affects hydrogen concentration in the a-IGZO layer, which subsequently influences the device performance and stability under bias-temperature-stress. Hydrogen increases the carrier concentration in the active layer, but it also electrically deactivates intrinsic defects depending on its concentration. The influence of hydrogen varies between the TFTs fabricated on a glass substrate to those on a PI substrate. Hydrogen concentration is 5% lower in devices on a PI substrate after annealing, which increases the hysteresis characteristics from 0.22 to 0.55 V and also the threshold voltage shift under positive bias temperature stress by 2 ${\times}$ compared to the devices on a glass substrate. Hence, the analysis and control of hydrogen flux is crucial to maintaining good device performance and stability of a-IGZO TFTs.