• The Korean Journal of Ceramics
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• v.5 no.1
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• pp.1-11
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• 1999

The effect of aliovalent dopents, $Nb_3O_5$ and MnO, on the grain growth kinetics of 12 mol% ceria stabilized tetragonal zirconia polycrystals (Ce-TZP) was studied. All specimens were sintered at $1550^{\circ}C$ for 20 minutes prior to annealing at different temperatures to study grain growth kinetics. Grain growth kinetics of Ce-TZP and 1 mol% $Nb_2O_5$ doped Ce-TZP (Ce-TZP/$Nb_3O_5$) during annealing at 1475, 1550, and $1600^{\circ}C$ adequately matched with square law $(D^2-D_\;o^2=k_at)$. However, grain growth in 1 mol% MnO suppressed grain growth in Ce-TZP by drag force exerted by $Mn^{+2}$ ions which segregated strongly to the positively-charged grain boundaries of Ce-TZP, $Nb_2O_5$ enhanced grain growth by increasing the concentration of vacancies of $Zr^{+4}$ ion and $Ce^{+4}$ ions. Surface analysis with X-ray photoelectron spectroscopy (XPS) showed the segregation of Mn+2 ions to grain boundaries. The kinetics of grain growth obtained in the base Ce-TZP and the Ce-TZPs with the aliovalent dopants were examined in the context of impurity drag effect and space charge effect.

• Journal of Microbiology and Biotechnology
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• v.25 no.11
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• pp.1928-1935
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• 2015

Microbial growth kinetics is often used to optimize environmental processes owing to its relation to the breakdown of substrate (contaminants). However, the quantification of bacterial populations in the environment is difficult owing to the challenges of monitoring a specific bacterial population within a diverse microbial community. Conventional methods are unable to detect and quantify the growth of individual strains separately in the mixed culture reactor. This work describes a novel quantitative PCR (qPCR)-based genomic approach to quantify each species in mixed culture and interpret its growth kinetics in the mixed system. Batch experiments were performed for both single and dual cultures of Pseudomonas putida and Escherichia coli K12 to obtain Monod kinetic parameters (μ_max and K_s). The growth curves and kinetics obtained by conventional methods (i.e., dry weight measurement and absorbance reading) were compared with that obtained by qPCR assay. We anticipate that the adoption of this qPCR-based genomic assay can contribute significantly to traditional microbial kinetics, modeling practice, and the operation of bioreactors, where handling of complex mixed cultures is required.

• Journal of the Korean Institute of Telematics and Electronics
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• v.23 no.6
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• pp.820-832
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• 1986

In contrast to conventional liquid phase epitaxy of GaAs, surface kinetics limited growth is predominant in selective liquid phase epitaxy. For the stripe openings in the high-index crystal-lographic directions, the well-known facet formations and the decompositions into the low index planes or smooth circular surfaces are observed depending on the growth kinetics. For the low index direction stripe, surface kinetics limited growth is evident. By a numerical calcualtion we show that these phenomena are due to the enhanced masstransport by two dimensional diffusion and growth rate anisotropy which is found to be very stdrong with cusped minima for some singular planes in the solution growth as well as in vapor phase epitaxy. Morphological stability is briefly treated in terms of diffusion and its implications on device application are stated. Tese phenomena may be common to III-V compound semiconductors as well as GaAs.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.5 no.3
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• pp.197-208
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• 1995

An experiment study of the dendrite growth of ice crystals growing in quiescent pure subcooled water was made at small subcoolings of 0.035 K < ${\Delta}T$ < 1.000 K. It was observed that the growth kinetics and morphology are functions of not only subcooling but also thermal convection. When the subcooling is less than 0.35K, it was found that effect of thermal convection on growth kinetics of ice dendrites becomes important. Quantitiative measurements of growth velocity, $V_{G}$, and tip radii of the edge and basal planes, $R_{1}$ and $R_{2}$, were made simultaneously as a function of subcooling.

• Biotechnology and Bioprocess Engineering:BBE
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• v.11 no.3
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• pp.223-229
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• 2006

In this study, we have conducted kinetics and modelling studies of Centella asiatica cell growth and substrate uptake, in an attempt to evaluate cell growth for a better understanding and control of the process. In our bioreactor cultivation experiment, we observed a growth rate of 0.18/day, a value only 20% higher than was seen in the shake flask cultivation trial. However, the observed maximum cell dry weight in the shake flask, 10.5g/L, was 14% higher than was achieved in the bioreactor. Ninety seven percentage confidence was achieved via the fitting of three unstructured growth models; the Monod, Logistic, and Gompertz equations, to the cell growth data. The Monod equation adequately described cell growth in both cultures. The specific growth rate, however, was not effectively predicted with the Logistic and Gompertz equations, which resulted in deviations of up to 73 and 393%, respectively. These deviations in the Logistic and Gompertz models may be attributable to the fact that these models were developed for substrate-independent growth and fungi growth, respectively.

• Journal of the Korean institute of surface engineering
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• v.34 no.3
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• pp.231-239
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• 2001

The structure and composition of Cr-nitrides formed on an electroplated hard Cr layer during an ionnitriding process was analyzed, and the growth kinetics of the Cr-nitrides was examined as a function of the ion-nitriding temperature and time in order to establish a computer simulation model prediction the growth behavior of the Cr-nitride layer. The Cr-nitrides formed during the ion-nitriding at $550~770^{\circ}C$ were composed of outer CrN and inner $Cr_2$N layers. A nitrogen diffusion model in the multi-layer based on fixed grid FDM (Finite Difference Method) was applied to simulate the growth kinetics of Cr-nitride layers. By measuring the thickness of each Cr-nitride layer as a function of the ion-nitriding temperature and time, the activation energy for growth of each Cr-nitride was determined; 82.26 KJ/mol for CrN and 83.36 Kj/mol for $Cr_2$N. Further, the nitrogen diffusion constant was determined in each layer; $9.70$\times$10^{-12}$ /$m^2$/s in CrN and $2.46$\times$10^{-12}$ $m^2$/s in $Cr_2$N. The simulation on the growth kinetics of Cr-nitride layers was in good agreements with the experimental results at 550~72$0^{\circ}C$.

• Journal of Welding and Joining
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• v.20 no.5
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• pp.78-86
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• 2002

A metallurgical model for the prediction of prior austenite grain size considering the dissolution kinetics of M$_3$C precipitates at the heat affected zone of SA508-cl.3 was proposed. The isothermal kinetics of grain growth and dissolution were respectively described by well-known equation, $dD/dT=M({\Delta}F_{eff})^M$ and Whelan's analytical model. The isothermal grain growth experiments were carried out for measure the kinetic parameters of grain growth. The precipitates of the base metal and the specimens exposed to thermal cycle were examined by TEM-carbon extraction replica method. The model was assessed by the comparison of BUE simulation experiments and showed good consistencies. However, there was no difference between the model considering and ignoring $M_3C$ precipitates. It seems considered that pinning force exerted by $M_3C$ Precipitates was lower than driving force for grain growth due to large size and small fraction of precipitates, and mobility of grain boundary was low in the lower temperature range.

• Journal of the Korean Chemical Society
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• v.54 no.4
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• pp.380-386
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• 2010

We have investigated the growth kinetics of Al oxide film by anodization in sulfuric acid solution and the electronic properties of this film using electrochemical impedance spectroscopy. Al oxide film consisted $Al_2O_3$ was grown based on the point defect model and shown the eclctronic properties of n-type semiconductor.

• Food Science and Biotechnology
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• v.15 no.5
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• pp.664-671
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• 2006

Modeling the growth kinetics of lactic acid bacteria (LAB), one of the most valuable microbial groups in the food industry, has been actively pursued in order to understand, control, and optimize the relevant fermentation processes. Most modeling approaches have focused on the development of single population models. Primary single population models provide fundamental kinetic information on the proliferation of a primary LAB species, the effects of biological factors on cell inhibition, and the metabolic reactions associated with cell growth. Secondary single population models can evaluate the dependence of primary model parameters, such as the maximum specific growth rate of LAB, on the initial external environmental conditions. This review elucidates some of the most important single population models that are conveniently applicable to the LAB fermentation analyses. Also, a well-defined mixed population model is presented as a valuable tool for assessing potential microbial interactions during fermentation with multiple LAB species.

• Journal of Microbiology and Biotechnology
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• v.21 no.6
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• pp.652-658
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• 2011

The growth kinetics of Streptomyces noursei NRRL 5126 was investigated under different aeration and agitation combinations in a 5.0 l stirred tank fermenter. Poly-${\varepsilon}$-lysine biosynthesis, cell mass formation, and glycerol utilization rates were affected markedly by both aeration and agitation. An agitation speed of 300 rpm and aeration rate at 2.0 vvm supported better yields of 1,622.81 mg/l with highest specific productivity of 15 mg/l.h. Fermentation kinetics performed under different aeration and agitation conditions showed poly- ${\varepsilon}$-lysine fermentation to be a growth-associated production. A constant DO at 40% in the growth phase and 20% in the production phase increased the poly-${\varepsilon}$-lysine yield as well as cell mass to their maximum values of 1,992.35 mg/l and 20.73 g/l, respectively. The oxygen transfer rate (OTR), oxygen utilization rate (OUR), and specific oxygen uptake rates ($qO_2$) in the fermentation broth increased in the growth phase and remained unchanged in the stationary phase.