• Microbiology and Biotechnology Letters
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• v.18 no.4
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• pp.394-400
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• 1990

Maximization of productivity of recombinant cell fermentations requires consideration of the inverse relationship between the host cell growth rate and product formation rate. The problem of maximizing a weighted performance index was solved by using optimal control theory for recombinant E. coli fermentation. Concentration of a growth inhibitor was used as a control variable to manipulate the specific growth rate, and consequently the cloned-gene expression rate. Using a simple unstructured model to describe the main characteristics of this system, theoretical analysis showed that the optimal control profile results in an initial high growth rate phase followed by a low growth rate and high product formation rate phase. Numerical calculations were done to determine optimal switching times from the growth to the production stage for two representative cases corresponding to different dependency of the product formation rate on the growth rate. For the case when product formation rate is sensitive to the specific growth rate, the optimized operation yields about 60% increase in the final product concentration compared with a simple batch fermentation.

• Korean Journal of Environmental Biology
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• v.22 no.3
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• pp.376-380
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• 2004

In August 2003, the water quality of offshore waters along the Incheon coast of Korea was evaluated by biological evaluation using gametes, embryos and early development systems of a starfish species (Asterina pectinifera). As the result of performing biological evaluations on seawater samples from a total thirteen sites, the formation rate of normal larva was 16-68%. At seawater sample from site 5 and 13, formation rate of normal larva averaged 16%, the most abnormal rate hindering the early embryo development of the experimental animal, while that of site 3 averaged 68%, the highest formation rate of normal larva. At seawater sample from site 2, 4, 7, 9, 10, 11, 12, formation rate of normal larva averaged 33-54%, those which damage the development of early embryos slightly. At seawater sample from site 1, 5, 6, 8, 13, formation rate of normal larva averaged 16-28%, those which damage the development of early embryos strongly.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.2
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• pp.37.1-37.1
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• 2021

Observations suggest the star formation in nuclear rings of barred galaxies proceeds episodically in time and sometimes asymmetrically in space. Existing theories and numerical simulations suggest that the episodic star formation is perhaps due to either supernova feedback combined with fluid instabilities or time-varying mass inflow rate. However, it has been challenging to discern what dominates in shaping the star formation history because the effects of the inflow and feedback are blended in global simulations of nuclear rings. To understand their effects separately, we construct semi-global models of nuclear rings, which treat the mass inflow rate as a model parameter. By running simulations with the inflow rates kept constant or oscillating in time, we find that the star formation rate (SFR) of the rings varies coherently with the inflow rate, while the feedback is responsible only for stochastic fluctuations of the SFR within a factor of two. The feedback instead plays an important role in maintaining the vertical dynamical equilibrium and setting the depletion time. While the asymmetry in the inflow does not necessarily lead to the asymmetry in the star formation, we find that the rings undergo a transient period of lopsided star formation when the inflow rate of only one dust lane is suddenly increased.

• Journal of the Korean Ceramic Society
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• v.30 no.6
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• pp.433-440
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• 1993

The bioactivity of glasses in the CaO-SiO2 system and CaO-P2O5-SiO2 system with less than 10mol% of P2O5 was investigated by in vitro test in simulated body flood(SBF). The formation of Ca.P film and hydroxyapatite on the surface of glasses after in vitro test was analysed by X-ray photoelectron spectoscopy (XPS), fourier transform infrared reflection spectroscopy (FT-IRRS), energy dispersive X-ray spectroscopy (EDS), and scanning electron microscopy (SEM) observation. In the early stage of Ca.P film formation after in vitro test for CaO-SiO2 and CaO-P2O5-SiO2 glasses, the rate of Ca.P film formation on the surface of the glasses was dependent of structural parameter (Y) evaluated from the glass composition. First, in the case of the glasses having Y value below 2, Ca.P film and SiO2-rich layer were formed simultaneously, and there were no differences of the rate of Ca.P film formation in terms of the Y values. Second, in the case of the glasses having Y value above 2, the SiO2-rich layer was formed, and then Ca.P.Si mixed layer was formed in the silica gel structure of the SiO2-rich layer, and finally the Ca.P film on the surface of SiO2-rich layer. The rate of Ca.P film formation delayed as the Y values increased. The rate of hydroxyapatite formation of glasses (the rate of transformation from Ca.P film to hydroxyapatite) seems to be propotional to the rate of Ca.P film formation and Y value. The rate of hydroxyapatite formation of glasses belonging to the second group was delayed as structural parameter increased, and the hydroxyapatite crystal showed spherical growth in the early reaction stage, and then showed silkworm-like linear growth as the reaction time increased.

• Journal of Periodontal and Implant Science
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• v.38 no.3
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• pp.535-542
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• 2008

Purpose: The aim of this retrospective study is to evaluate survival rate of implant and bone formation, to analyze failure contribution factor. Material and Methods: A total of 52 consecutive patients(35 male, 17 female, mean age 49 years) with 104 osseous defects were treated during the period from October 2004 to June 2007 with a simultaneous or staged GBR approach using non-resorbable or resorbable membranes combined with autogenous bone grafts or xenograft(Bio-Oss, Bio-cera, BBP). Result: A total of 32(30,8%) of 104 GBR-treated sites failed the bone formation and a total of 5(5.6%) of 89 implants were removed. Early exposure of the membrane has significantly affected bone formation(p<0.05). Non-resorbable membrane showed more exposure of the membrane and low success rate of bone formation than resorbable membrane(p<0.05). There were no difference between success rate of bone formation and using autogenous bone or graft materials. There were no statistically significant difference between success rate of bone formation and smoking or using PRP. Mandible showed more success rate of bone formation than maxilla(p<0.05). Conclusion: Early exposure of the membrane, membrane type and maxilla/mandible type have influence on success rate of bone formation during GBR.

• Journal of Forest and Environmental Science
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• v.36 no.4
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• pp.290-297
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• 2020

This study analyzed and compared the damage rate, natural parasitic rate, and the morphological characteristics of Thecodiplosis japonensis larvae, which inhabit forest areas as control areas to large urban areas in 2018 and 2019. This research was conducted to provide basic data for the management of Thecodiplosis japonensis, which harm pine needles, and the results were as follows. First, the gall formation rate of Thecodiplosis japonensis collected from urban areas was upper-crown 35.59% and 34.25%, mid-crown 25.57% and 27.95%, and lower-crown 25.34% and 26.61%; the gall formation rate of Thecodiplosis japonensis was in the order of upper-crown>mid-crown>lower-crown in 2018 and 2019, respectively. In the control areas, the gall formation rates of Thecodiplosis japonensis in mountain villages in 2018 and 2019 were upper-crown 17.72% and 21.78%, mid-crown 13.85% and 16.97%, and lower-crown 15.12% and 15.79%; thus, in the order of upper-crown>lower-crown>mid-crown. The number of larvae in the galls of needles damaged by Thecodiplosis japonensis was as follows: the average number of larvae in the pine trees of urban areas was 9 and 8 in the upper-crown, 7 and 8 in the mid-crown, and 6 and 7 in the lower-crown respectively. This shows that the number of larvae was fewer in the lower-crown than the upper-crown, and that the number of larvae was higher in 2018 than in 2019. For natural parasitic rate of Thecodiplosis japonensis, the gall formation rate and natural parasitic rate of Thecodiplosis japonensis were surveyed; the natural parasitic rate was 12.5% and 11.8% in urban areas while the rate was 21.7% and 20.9% in mountain villages in respectively in 2018 and 2019.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.1
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• pp.51.2-51.2
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• 2021

Nuclear rings are sites of intense star formation at the center of barred spiral galaxies. A straightforward but unanswered question is what controls star formation rate (SFR) in nuclear rings. To understand how the ring SFR is related to mass inflow rate, gas content, and background gravitational field, we run a series of semi-global hydrodynamic simulations of nuclear rings, adopting the TIGRESS framework to handle radiative heating and cooling as well as star formation and supernova feedback. We find: 1) when the mass inflow rate is constant, star formation proceeds in a remarkably steady fashion, without showing any burst-quench behavior suggested in the literature; 2) the steady state SFR has a simple linear relationship with the inflow rate rather than the ring gas mass; 3) the midplane pressure balances the weight of the overlying gas and the SFR surface density is linearly correlated with the midplane pressure, consistent with the self-regulated star formation theory. We suggest that the ring SFR is controlled by the mass inflow rate in the first place, while the gas mass adjusts to the resulting feedback in the course of achieving the vertical dynamical equilibrium.

• Fibers and Polymers
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• v.2 no.1
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• pp.140-143
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• 2001

To better understand the formation of necking in drawing processes of fibers, strain distributions during drawing processes have been analyzed. For simplicity, one-dimensional incompressible steady flow at a constant temperature was assumed and quasi-static model was used. To describe mechanical properties of solid polymers, non-linear visco-plastic material properties were assumed using the power law type hardening and rate-sensitive equation. The effects of various parameters on the neck formation were matematically analyzed. As material property parameters, strain-hardening parameter, visco-elastic coefficient and strain-rate sensitivity were considered and, for process parameters, the drawing ratio and the process length were considered. It was found that rate-insensitive materials do not reach a steady flow state and the rate-sensitivity plays a key role to have a steady flow. Also, the neck formation is mainly affected by material properties, especially for the quasi-static model. If the process length changes, the strain distribution was found to be proportionally re-distributed along the process line by the factor of the total length change.

• Journal of Environmental Health Sciences
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• v.35 no.6
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• pp.486-490
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• 2009

In January 2009, the water quality of offshore around the Incheon coast was evaluated by bioassay using early development systems of a sea urchin species, Hemicentrotus pulcherrimus. The results of performing biological evaluations on seawater samples from total of thirteen sites, showed that the formation rates of normal pluteus larva varied from 18% to 71%. In site 5 the seawater sample led to an averaage formation rate of normal larva of 18%, the highest abnormal formation rate hindering the early embryo development of the experimental animal, while that of site 3 averaged 71%, the highest formation rate of normal larva. Seawater samples from site 1, 2, 4, 7, 9, 10, 11 and 12, resulted in average formation rates of normal larva from 33% to 56%, which indicates the developmental damage of early embryos is not severe. Seawater samples from site 5, 6, 8 and 13, resulted in average formation rates of normal larva from 18% to 21% which there was strong damage to the development of early embryos.

• Plant Resources
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• v.7 no.1
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• pp.7-14
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• 2004

Allium wakegi was cultured shoot tip in the condition of light culture. The Allium wakegi added plant growth regulator was observed of plant regeneration and bulblet formation. Callus Induction and growing rate was the best of 78％ when added alone 2,4-D 0.5mg/L. In the formation of shoot, its regeneration rate was 96％ when added BA 0.5mg/L in the light culture condition. When BA 0.5mg/L and NAA 0.5mg/L mixed and BA 0.5 mg/L and NAA 1.0mg/L mixed, the rates were 99％ and 97％ respectively, and these conditions were suitable for forming shoot. In the formation of roots, when added NAA 2.0mg/L in the light culture condition, the regeneration rate was 90.6 ％ and the roots were abnormal. When added NAA 1.0mg/L, the rate was 82 ％ and the highest. In the formation of bulbs, when BA 05mg/L and NAA 1.0mg/L mixed, the root generantion and its size in the bulbs was the best compare to other treatment experiments.