• Korean Journal of Materials Research
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• v.34 no.2
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• pp.72-78
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• 2024

The lightweight and high strength characteristics of aluminum alloy materials make them have promising prospects in the field of construction engineering. This paper primarily focuses on aluminum alloy materials. Aluminum alloy was combined with concrete, wood and carbon fiber reinforced plastic (CFRP) cloth to create a composite column. The axial compression test was then conducted to understand the mechanical properties of different composite structures. It was found that the pure aluminum tube exhibited poor performance in the axial compression test, with an ultimate load of only 302.56 kN. However, the performance of the various composite columns showed varying degrees of improvement. With the increase of the load, the displacement and strain of each specimen rapidly increased, and after reaching the ultimate load, both load and strain gradually decreased. In comparison, the aluminum alloy-concrete composite column performed better than the aluminum alloy-wood composite column, while the aluminum alloy-wood-CFRP cloth composite column demonstrated superior performance. These results highlight excellent performance potential for aluminum alloy-wood-CFRP composite columns in practical applications.

• Nonlinear Functional Analysis and Applications
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• v.29 no.2
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• pp.527-543
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• 2024

In the realm of differential games and bioeconomic modeling, where intricate systems and multifaceted interactions abound, we explore the precision and efficiency of the Chebyshev Tau method (CTM). We begin with the Weierstrass Approximation Theorem, employing Chebyshev polynomials to pave the way for solving intricate bioeconomic differential games. Our case study revolves around a three-player bioeconomic differential game, unveiling a unique open-loop Nash equilibrium using Hamiltonians and the FilippovCesari existence theorem. We then transition to numerical implementation, employing CTM to resolve a Three-Point Boundary Value Problem (TPBVP) with varying degrees of approximation.

• Asian-Australasian Journal of Animal Sciences
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• v.27 no.1
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• pp.93-100
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• 2014

The banning of the use of antibiotics as feed additive has accelerated investigations of alternative feed additives in animal production. This experiment investigated the effect of pure citric acid or acidifier blend supplementation as substitute for antibiotic growth promoters on growth performance, fecal microbial count, and humoral immunity in weaned piglets challenged with Salmonella enterica serover Typhimurium and Escherichia coli KCTC 2571. A total of 60 newly weaned piglets (crossbred, 28-d-old; average 8 kg initial weight) were randomly assigned to four dietary treatments in a completely randomized design. Dietary treatments included NC (negative control; basal diet), PC (positive control; basal diet+0.002% apramycin), T1 (basal diet+0.5% pure citric acid), and T2 (basal diet+0.4% acidifier blend). All piglets were orally challenged with 5 mL of culture fluid containing $2.3{\times}10^8$ cfu/mL of E. coli KCTC 2571 and $5.9{\times}10^8$ cfu/mL of S. typhimurium at the beginning of the experiment. The PC group showed the highest ADG and ADFI, whereas gain:feed was improved in the PC and T1 group (p<0.05). All dietary treatments showed significant reduction in fecal counts of Salmonella and E. coli, compared to NC (p<0.05), with PC being better than T1 and T2. Significant elevation in fecal Lactobacillus spp. counts was shown by treatments with T1, T2, and PC, whereas Bacillus spp. counts were increased by treatment with T1 and T2 compared to NC and PC diet (p<0.05). Serum IgG concentration was increased by T1 diet (p<0.05), whereas IgM and IgA were not significantly affected by any of the dietary treatments (p>0.05). From these above results, it can be concluded that, as alternatives to antibiotics dietary acidification with pure citric acid or acidifiers blend did not fully ameliorate the negative effects of microbial challenges in respect of growth performance and microbial environment, however improved immunity suggested further research with different dose levels.

• Analytical Science and Technology
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• v.6 no.2
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• pp.167-180
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• 1993

The effects of coating variables on the formation of aluminide coating layer with good oxidation resistance on the strongest hot-forged superalloy in the world, KM 1557 developed at KIST by pack cementation process were studied. Pack aluminizing were performed by high-activity process with pure aluminium powders and by low-activity process with codep powders. For high-activity process, Al deposition rate, growth rate of coating layer, and cross-sectional microstructures were influenced by the species and additive amounts of activators and the additive amounts of pure aluminium powders. For low-activity process, Al deposition rate, growth rate of coating layer, and the cross-sectional microstructures were not influenced by the species but additive amounts of activators. Surface structures of coating layer were influenced by the species of activators. Regardless of aluminium activity, Al deposition rate was proportional to the square root of time and parabolic rate constants were different with the species of activators. The activation energy for deposition of aluminium was different with the species of activators for high-activity process. Regardless of the species of activators, the activation energy for deposition of aluminium was 12~14 Kcal/mole for low-activity process.

• Korean Journal of Environment and Ecology
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• v.23 no.3
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• pp.258-271
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• 2009

Various environmental parameters change and ecological succession often lead to decline of Pinus densiflora forest in Seoul. Due to decline of it, we proposed the ecological management for conserving and improving from decrease of its dominant area on there. We analysed the P. densiflora forest's classification and suggested its ecological management that based on relation to competition between dominant species in the upper tree layer, the presence of competitive species in shrub layer and vegetation management standard. The Pinus densiflora forest types has been classified 6 types by ecological characteristics. The results from categorized its types are following as; 1) Pinus densiflora pure forest type; edaphic climax Pinus densiflora forest(26.1%), Pinus densiflora pure forest(21.5%). 2) the forest of Pinus densiflora and other species that compete with each other type; Pinus densiflora-Quercus mongolica forest(28.0%), Pinus densiflora-Pinus rigida forest(13.1%), Pinus densiflora-Quercus acutissima(4.2%). We conclude that the results in these kind of 4 types; Pinus densiflora pure forest type where possible to maintain the forest by edaphic climax, human trampling damage, vegetation management(e.x. remove the competition species, shrub layers management etc.) are mainly need to negative management. Whereas, the others 4 types; Pinus densiflora and other species(Quercus variabilis, foreign species, naturalized species etc.) that compete with each other types are need to positive management such as manage the same niche competition species, shrub layers management, remove the foreign species, naturalized species etc.. In these kinds of ecological management are very necessary to maintain Pinus densiflora forest.

• Asian Pacific Journal of Cancer Prevention
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• v.16 no.18
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• pp.8259-8263
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• 2016

Background: Nano-therapy has the potential to revolutionize cancer therapy. Chrysin, a natural flavonoid, was recently recognized as having important biological roles in chemical defenses and nitrogen fixation, with anti-inflammatory and anti-oxidant effects but the poor water solubility of flavonoids limitstheir bioavailability and biomedical applications. Objective: Chrysin loaded PLGA-PEG-PLGA was assessed for improvement of solubility, drug tolerance and adverse effects and accumulation in a gastric cancer cell line (AGS). Materials and Methods: Chrysin loaded PLGA-PEG copolymers were prepared using the double emulsion method (W/O/W). The morphology and size distributions of the prepared PLGA-PEG nanospheres were investigated by 1H NMR, FT-IR and SEM. The in vitro cytotoxicity of pure and nano-chrysin was tested by MTT assay and miR-34a was measured by real-time PCR. Results: 1H NMR, FT-IR and SEM confirmed the PLGA-PEG structure and chrysin loaded on nanoparticles. The MTT results for different concentrations of chrysin at different times for the treatment of AGS cell line showed IC50 values of 68.2, 56.2 and $42.3{\mu}M$ and 58.2, 44.2, $36.8{\mu}M$ after 24, 48, and 72 hours of treatment, respectively for chrysin itslef and chrysin-loaded nanoparticles. The results of real time PCR showed that expression of miR-34a was upregulated to a greater extent via nano chrysin rather than free chrysin. Conclusions: Our study demonstrates chrysin loaded PLGA-PEG promises a natural and efficient system for anticancer drug delivery to fight gastric cancer.

• Journal of Korean Society of Forest Science
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• v.98 no.6
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• pp.772-779
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• 2009

This study was conducted to estimate the carbon (C) contents in pure and mixed stands of pine (Pinus densiflora) and oak (Quercus spp.) trees for establishing the C inventory of forest ecosystems. A total of fifteen 20 m${\times}$20 m pure and mixed stands of pine and oak trees were chosen in natural forests in Hoengseong, Kangwon based on the basal area of all trees ${\geq}$ 5 cm DBH: three of 95% of pine and 5% oak trees [pine stand], three of 100% of oak trees [oak stand], and nine of 20 to 70% of pine and 80 to 30% of oak trees [mixed stand]. To estimate C contents in the study stands, biomass in vegetation, forest floor and coarse woody debris (CWD) were calculated and C concentrations in vegetation, forest floor, CWD and soil (0-30 cm) were analyzed. There was no significant difference in vegetation C contents among the stands; 147.6 Mg C/ha for the oak stand, 141.4 Mg C/ha for the pine stand and 115.8 Mg C/ha for the mixed stand. Forest floor C contents were significantly different among the stands (p<0.05); 12.7 Mg/ha for the pine stand, 9.9 Mg/ha for the oak stand, and 8.4 Mg/ha for the mixed stand. However, CWD C contents were not significantly different among the stands (p>0.05); 2.2 Mg/ha for the mixed stand, 1.7 Mg/ha for the oak stand, and 1.1 Mg/ha for the pine stand. Soil C contents up to 30 cm depth were not significantly different among the study stands; 44.4 Mg C/ha for the pine stand, 41.6 Mg C/ha for the mixed stand, and 33.3 Mg C/ha for the oak stand. Total ecosystem C contents were lower in the mixed stand than those in the pure stands, because vegetation C contents which occupied almost total ecosystem C contents were lower in the mixed stand than those in the pure stands; 199.6 Mg C/ha for the pine stand, 192.5 Mg C/ha for the oak stand and 169.1 Mg C/ha for the mixed stand. Lower vegetation C contents in the mixed stand might be influenced by interspecific competition between pine and oak trees and intraspecific competition among the oak trees resulted from high stand density. We suggest that forest management such as thinning to enhance C storage is indispensible for minimizing the competition in forest ecosystems.

• Journal of Periodontal and Implant Science
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• v.45 no.3
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• pp.120-126
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• 2015

Purpose: With the significance of stable adhesion of alveolar bone and peri-implant soft tissue on the surface of titanium for successful dental implantation procedure, the purpose of this study was to apply microgrooves on the titanium surface and investigate their effects on peri-implant cells and tissues. Methods: Three types of commercially pure titanium discs were prepared; machined-surface discs (A), sandblasted, large-grit, acid-etched (SLA)-treated discs (B), SLA and microgroove-formed discs (C). After surface topography of the discs was examined by confocal laser scanning electron microscopy, water contact angle and surface energy were measured. Human gingival fibroblasts (hGFs) and murine osteoblastic cells (MC3T3-E1) were seeded onto the titanium discs for immunofluorescence assay of adhesion proteins. Commercially pure titanium implants with microgrooves on the coronal microthreads design were inserted into the edentulous mandible of beagle dogs. After 2 weeks and 6 weeks of implant insertion, the animal subjects were euthanized to confirm peri-implant tissue healing pattern in histologic specimens. Results: Group C presented the lowest water contact angle ($62.89{\pm}5.66{\theta}$), highest surface energy ($45{\pm}1.2mN/m$), and highest surface roughness ($Ra=22.351{\pm}2.766{\mu}m$). The expression of adhesion molecules of hGFs and MC3T30E1 cells was prominent in group C. Titanium implants with microgrooves on the coronal portion showed firm adhesion to peri-implant soft tissue. Conclusions: Microgrooves on the titanium surface promoted the adhesion of gingival fibroblasts and osteoblastic cells, as well as favorable peri-implant soft tissue sealing.

• Journal of Microbiology and Biotechnology
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• v.27 no.1
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• pp.92-100
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• 2017

Acetoin (AC) is a volatile platform compound with various potential industrial applications. AC contains two stereoisomeric forms: (3S)-AC and (3R)-AC. Optically pure AC is an important potential intermediate and widely used as a precursor to synthesize novel optically active materials. In this study, chiral (3R)-AC production from meso-2,3-butanediol (meso-2,3-BD) was obtained using recombinant Escherichia coli cells co-expressing meso-2,3-butanediol dehydrogenase (meso-2,3-BDH), NADH oxidase (NOX), and hemoglobin protein (VHB) from Serratia sp. T241, Lactobacillus brevis, and Vitreoscilla, respectively. The new biocatalyst of E. coli/pET-mbdh-nox-vgb was developed and the bioconversion conditions were optimized. Under the optimal conditions, 86.74 g/l of (3R)-AC with the productivity of 3.61 g/l/h and the stereoisomeric purity of 97.89% was achieved from 93.73 g/l meso-2,3-BD using the whole-cell biocatalyst. The yield and productivity were new records for (3R)-AC production. The results exhibit the industrial potential for (3R)-AC production via whole-cell biocatalysis.

• Asian Pacific Journal of Cancer Prevention
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• v.16 no.17
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• pp.7785-7788
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• 2015

Utilization of high energy photons (>10MV) with an optimal weight using a mixed energy technique is a practical way to generate a homogenous dose distribution while maintaining adequate target coverage in intact breast radiotherapy. This study represents a model for estimation of this optimal weight for day to day clinical usage. For this purpose, treatment planning computed tomography scans of thirty-three consecutive early stage breast cancer patients following breast conservation surgery were analyzed. After delineation of the breast clinical target volume (CTV) and placing opposed wedge paired isocenteric tangential portals, dosimeteric calculations were conducted and dose volume histograms (DVHs) were generated, first with pure 6MV photons and then these calculations were repeated ten times with incorporating 18MV photons (ten percent increase in weight per step) in each individual patient. For each calculation two indexes including maximum dose in the breast CTV ($D_{max}$) and the volume of CTV which covered with 95% Isodose line ($V_{CTV,95%IDL}$) were measured according to the DVH data and then normalized values were plotted in a graph. The optimal weight of 18MV photons was defined as the intersection point of $D_{max}$ and $V_{CTV,95%IDL}$ graphs. For creating a model to predict this optimal weight multiple linear regression analysis was used based on some of the breast and tangential field parameters. The best fitting model for prediction of 18MV photons optimal weight in breast radiotherapy using mixed energy technique, incorporated chest wall separation plus central lung distance (Adjusted R2=0.776). In conclusion, this study represents a model for the estimation of optimal beam weighting in breast radiotherapy using mixed photon energy technique for routine day to day clinical usage.