• 한국생산제조학회지
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• 제7권6호
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• pp.117-125
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• 1998

The paper attempts to estimate the incubation time of a cavity in the interface between a power law creep particle and an elastic matrix subjected to a uniaxial stress. Since the power law creep particle is time dependent, the stresses in the interface relax. The volume free energy associated with Helmholtz free energy includes strain energies caused by applied stress and dislocations piled up in interface(DPI). The energy due to DPI is found by modifying the result of Dundurs and Mura[4]. The volume free energies caused by both applied stress and DPI are a function of the cavity size(r) and elapsed time(t) and arise from stress relaxation in the interface. Critical radius $r^*$ and incubation time $t^*$ to maximise Helmholtz free energy is found in present analysis. Also, kinetics of cavity formation are investigated using the results obtained by Riede [7]. The incubation time is defined in the analysis as the time required to satisfy both the thermodynamic and kinetic conditions. Through the analysis it is found that 1) strain energy caused by the applied stress does not contribute significantly to the thermodynamic and kinetic conditions of a cavity formation, 2) in order to satisfy both thermodynamic and kinetic conditions, critical radius $r^*$ decreases or holds constant with increase of the time until the kinetic condition(eq. 2.3) is satisfied. there for the cavity may not grow right after it is formed, as postulated by Harris [15], and Ishida and Mclean [16], 3) the effects of strain rate exponent (m), material constant $\sigma$0, volume fraction of the particle to matrix(f)and particle size on the incubation time are estimated using material constants of the copper as matrix.

• 한국물환경학회지
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• 제24권1호
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• pp.63-68
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• 2008

This study was performed to assess the potential use of ozone or UV radiation for the treatment of water contaminated with sulfamethoxazole (SMX), which is frequently used antibiotic in human and veterinary medicines, especially focusing on the kinetic study and effect of pH. In a study using ozone alone, kinetic study was performed to determine second-order rate constant ($k_{O3,SMX}$) for the reactions of SMX with ozone, which was found to be $1.9{\times}10^6M^{-1}s^{-1}$ at pH 7. The removal efficiencies of SMX by ozone were decreased with increase of pH due to rapid decomposition of ozone under the condition of various pH (2.5, 5.3, 7, 8, 10). In a UV irradiation study at 254 nm, a kinetic model for direct photolysis of SMX was developed with determination of quantum yield ($0.08mol\;Einstein^{-1}$) and molar extinction coefficient ($15,872M^{-1}cm^{-1}$) values under the condition of quantum shielding due to the presence of reaction by-products formed during photolysis. For effect of pH on photolysis of SMX, SMX in the anionic state ($S^-$, pH > 5.6), most prevalent form at environmentally relevant pH values, degraded more slowly than in the neutral state (SH, 1.85 < pH < 5.6) by UV radiation at 254 nm.

• 생명과학회지
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• 제15권1호
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• pp.15-20
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• 2005

동충하초 Paecilomyces tenuipes C240의 균사체 배양과정에서 균사체 성장, 세포외 다당체 생산, 기질감소 속도를 표현할 수 있는 동력학적 모델을 제시하였다. 균사체 성장은 Logistic식을, 세포외 다당체 생산은 Luedeking-Piret 식을, 기질소모는 Luedeking-Piret 유사식을 각각 적용함으로써, 전체 균사체 배양과정을 예측할 수 있었다. 모델식에서 사용된 주요 kineti, constant들은 다음과 같다: 균사체의 최대 비성장속도${\mu}m,\;0.7281\;h^{-1};$; 다당체 생산에서의 growth-associated constant $(\alpha),\;0.1743g(g\;cells)^{-1}$; non-growth-associated constant $(\beta),\;0.0019g(g\;cells)^{-1}\;;$ maintenance coefficient ($(m_s),\;0.0572g\;(g\;cells)^{-1}$·5L 발효조에서 얻은 균사체 성장, 세포외 다당체 생산, 기질감소 속도자료들을 모델에서 예측한 결과와 비교한 결과 서로 잘 일치하는 것으로 보아, 본 연구에서 제안된 모델식은 이 동충하초 균사체 배양공정의 scale-up등의 프로세스 설계에 응용가능 할 것이며, 다른 종류의 동충하초 균사체 배양공정에도 적용가능 할 것으로 판단된다.

• 한국연초학회지
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• 제4권2호
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• pp.57-61
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• 1982

For evaluating kinetic parameters of various reactions and materials a straight- forward method has been studied by the variable heating rate method in DSC analysis. Based on the linear relationship between the logarithm of the heating rate and reciprocal Peak temperature, this method allows calculation of activation energy and the Arrhenius frequency factor by only one observation of the peak temperature versus the heating rate. According to tile D function, D=-In P(x)/dx, to x(=$\frac{E}{RT}$) we can calculate reasonably accurate activation energy, tile Arrhenius factor and the rate constant, and predict half-life times of various materials from the kinetic calculation.

• 대한화학회지
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• 제62권2호
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• pp.79-86
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• 2018

This study reported the adsorption of Cu(II) ions onto activated carbon prepared from Myristica Fragrans shell (MFS AC) over independent variables of contact time, activating chemical (NaOH) concentration, initial adsorbate concentration, initial pH of adsorbate solution and adsorption temperature. The MFS AC structure, morphology and total surface area were characterized by FTIR, SEM and BET techniques, respectively. The Cu(II) ions adsorption on the MFS AC (activated using 0.5 M NaOH) fitted best to Freundlich adsorption isotherm (FAI), and the FAI constant obtained was 0.845 L/g at $30^{\circ}C$ and pH 4.5. It followed the pseudo first order of adsorption kinetic (PFOAK) model, and the PFOAK based adsorption capacity was 107.65 mg/g. Thermodynamic study confirmed the Cu(II) ions adsorption should be exothermic and non-spontaneous process, physical adsorption should be taken place. The total surface area and pore volume based on BET analysis was $99.85m^2/g$ and 0.086 cc/g, respectively.

• 한국지반공학회논문집
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• 제18권5호
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• pp.159-167
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• 2002

아연의 주물사에 대한 분배계수는 주물사에 포함된 TOC, 점토 함량, 총 철 함량 등에 따라 변하고 특히 용액 PH에 큰 영향을 받는 것을 관찰하였다. Batch 실험으로부터 얻어진 경험식으로부터분배계수와 제거상수를 예측할 수 있었다. Batch kinetic 실험과 batch sorption 실험으로부터 얻어진 분배계수는 용액 pH가 같을 시 거의 같은 값을 보이고 있다.

• 한국미생물·생명공학회지
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• 제17권6호
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• pp.552-555
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• 1989

Corynebacterium glutamicum의 NADPH-specific glutamate dehydrogenase를 이용하여 NADPH, NH$_4$Cl, $\alpha$-ketoglutarate의 기질에 대한 kinetics를 고찰하였다. 이들의 kinetic constants를 측정함으로서 정반응에로의 효소반응 기작은 첫번째 효소와 반응하는 기질이 NADPH 임을 확인할 수 있었다. Glutamate dehydrogenase 활성의 조절을 위한 metabolites의 효과를 고찰하여 본 결과 malate와 citrate 만이 효소에 억제 효과를 나타내었으며, potassium chloride는 효소활성에 가장 많은 영향을 주었다.

• 한국환경과학회지
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• 제9권3호
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• pp.261-266
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• 2000

A kinetic study for nitrate removal by anion exchange resin was performed using continuous column reactors. Kinetic approach from the packed bed showed the reaction rate constant k$_1$ was 0.07~0.17 $\ell$/mgㆍhr and maximum exchange quantity q$_{o}$ was 27.75~31.81 mg/g. The results from the continuous column well agreed with that from the batch reactor. An economic analysis of the water treatment plant by anion exchange resin with a regenerating system was performed to design plant and process. Based on the treatment of 20 mg/$\ell$ nitrate-contained wastewater of 10,000 gallons per day to 2 mg/$\ell$, total capital cost and total annual cost are estimated to be 836 million wons and 211 million wons, respectively.y.

• Membrane and Water Treatment
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• 제8권1호
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• pp.73-88
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• 2017

Adsorption kinetics of aqueous ferric ion ($Fe^{3+}$) onto bio-natural rice grains (BRG) have been studied in a batch system. The influence of contact time (0-180 minutes), the dosage of BRG adsorbent (10, 20, 40, and $60gL^{-1}$), and ambient temperature (27, 37, 47, and $57^{\circ}C$) for the adsorption system have been reported. The equilibrium time achieved after 20 minutes of adsorption contact time. The maximum removal of ferric ion is 99% by using $60gL^{-1}$ of BRG, $T=37^{\circ}C$, and $50mgL^{-1}$ ferric ion solution. Adsorption kinetic and diffusion models, such as pseudo-first order, pseudo-second order, and Weber-Morris intra-particle diffusion model, have been used to describe the adsorption rate and mechanism of the ferric ion onto BRG surface. The sorption data results are fitted by Lagergren pseudo-second order model ($R^2=1.0$). The kinetic parameters, rate constant, and sorption capacities have been calculated. The new information in this study suggests that BRG could adsorb ferric ion from water physiosorption during the first 5 minutes. Afterward, the electrostatic interaction between ferric ion and BGR-surface could take place as a very weak chemisorptions process. Thus, there is no significant change could be noticed in the FTIR spectra after adsorption. I recommend producing BGR as a bio-natural filtering material for removing the ferric ion from water.

• Journal of Welding and Joining
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• 제25권4호
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• pp.42-48
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• 2007

An inert gas atomized NiTiZrSiSn bulk metallic glass feedstock was sprayed onto the copper plate using vacuum plasma spraying process. In order to change the in-flight particle energy, that is, thermal energy, the hydrogen gas flow rate in plasma gas mixture was increased at the constant flow rate of argon gas. Coating and single pass spraying bead were produced with the least feeding rate. Regardless of the plasma gas composition, fully melted through unmelted particle could be observed on the overlay coating. However, the frequency of the unmelted particle number density was increased with the decrease of the hydrogen gas flow rate. The amorphous phase fraction within coating was also affected by the number density of the unmelted particle.