• Journal of the Chungcheong Mathematical Society
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• v.32 no.3
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• pp.295-307
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• 2019

In this paper, we investigate Hyers-Ulam-Rassias stability of the functional equation $$f(x+ky)-{\frac{k^2+k}{2}}f(x+y)+(k^2-1)f(x)-{\frac{k^2-k}{2}}f(x-y)\\{\hfill{67}}-f(ky)+{\frac{k^2+k}{2}}f(y)+{\frac{k^2-k}{2}}f(-y)=0.$$

• Journal of the Chungcheong Mathematical Society
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• v.34 no.3
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• pp.209-219
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• 2021

A set {a₁, a₂, ⋯ , a_m} of positive integers is called a Diophantine m-tuple if a_ia_j + 1 is a perfect square for all 1 ≤ i < j ≤ m. Let F_n be the nth Fibonacci number which is defined by F₀ = 0, F₁ = 1 and F_n+2 = F_n+1 + F_n. In this paper, we find the extendibility of Diophantine pairs {F_2k, b} with some conditions.

• Korean Journal of Mathematics
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• v.30 no.2
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• pp.403-412
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• 2022

In this paper, we introduce the following cubic-quartic functional equation of the form $$f(x+4y)+f(x-4y)=16[f(x+y)+f(x-y)]{\pm}30f(-x)+\frac{5}{2}[f(4y)-64f(y)]$$. Further, we investigate the general solution and the Ulam stability for the above functional equation in non-Archimedean spaces by using the direct method.

• The Pure and Applied Mathematics
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• v.2 no.2
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• pp.157-162
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• 1995

Let I be the interval, $S^1$ the circle and let X be a compact metric space. And let $C^{circ}(X,\;X)$ denote the set of continuous maps from X into itself. For any f$f\in\;C\circ(X,\;X),\;let\;P(f),\;R(f),\;\Gamma(f),\;\Lambda(f)\;and\;\Omega(f)$ denote the collection of the periodic points, recurrent points, ${\gamma}-limit{\;}points,{\;}{\omega}-limit$ points and nonwandering points, respectively.(omitted)

• Nonlinear Functional Analysis and Applications
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• v.28 no.3
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• pp.801-812
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• 2023

In this paper, we investigate the superstability for the p-power-radical sine functional equation $$f\(\sqrt[p]{\frac{x^p+y^p}{2}}\)^2-f\(\sqrt[p]{\frac{x^p-y^p}{2}}\)^2=f(x)f(y)$$ from an approximation of the p-power-radical functional equation: $$f(\sqrt[p]{x^p+y^p})-f(\sqrt[p]{x^p-y^p})={\lambda}g(x)h(y),$$ where p is an odd positive integer and f, g, h are complex valued functions. Furthermore, the obtained results are extended to Banach algebras.

• Applied Biological Chemistry
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• v.22 no.2
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• pp.123-134
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• 1979

For the purpose of developing a microbial insecticide utilizing Bacillus thuringiensis Berliner, research was done and the following results were obtained. 1) As the freeze-dried matter of the cocoon-cooked water discarded from the filature contains much crude protein(51.825%) and a lot of inorganic salts, it can make a good nutrition source for the culture cf B. thuringiensis Berliner. 2) Based on the suspensibility, formula F-5 turned out to be the most suitable for insecticidal use. Its composition includes 0.2 g of the cell-spore-crystal mixture, 25 g of 200-mesh kaolin, 2.5 g of New Kalgen-NX-150, and 2.5 g of glycerine admixed with 8 ml of distilled water and granulated in 80-mesh size. 3) All the components of F-5, F-6 and F-7 are identical except that the amounts of cell-spore-crystal mixture of F-5, F-6, and F-7 are 0.2 g, 0.4 g, and 0.6 g, respectively. Accordingly, their physical properties are almost all the same. 4) Formulas F-5, F-6, and F-7 exhibited an excellent toxicity to Anomis mesogona Walker, Dendrolimus spectabilis Butler, and Margaronia perspectalis Walker at the concentration of 5%. 5) Formulas F-8 and F-9 which contain $NaHCO_3$ as one of their components showed a remarkably reduced toxicity to Anomis mesogona Walker and Dendrolimus spectabilis Butler than F-6 which does not contain $NaHCO_3$. 6) A maximum of $2.97{\times}10^9$ spores per ml was obtained by incubating B. thuringiensis in M-3 which has a pH of 7.05 and comprises 0.2% of ammonium sulphate and 0.8% of glucose dissolved in the cocoon-cooked water, with aeration for 96 hours. 7) Formula F-6 exhibited a somewhat reduced toxicity to Anomis mesogona Walker and Dendrolimus spectabilis Butler, when stored at room temperature for 70 days after formulation and it is desirable to keep it in a dark and cold place. 8) In held applications, formula F-6 showed a good activity in controlling Monema flavescens Walker. Margaronia perspectalis Walker, and Macrosiphum ibarae Matsumura.

• Composites Research
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• v.32 no.3
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• pp.148-157
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• 2019

In this study, $C_f/SiC$, $SiC_f/SiC$ and $C_f-SiC_f/SiC$ ceramic composites reinforcing carbon fiber, SiC fiber and hybrid fiber were fabricated by hybrid TGCVI and PIP process. After the thermal shock cycle, 3-point bending and Oxy-Acetylene torch test, their mechanical behavior, oxidation and erosion resistance were evaluated. The $C_f/SiC$ composite showed a decrease in mechanical property along with increasing temperature, a pseudo-ductile fracture mode and a large quantity of erosion. The $SiC_f/SiC$ composite exhibited stronger mechanical property and lower erosion rate compared to the $C_f/SiC$, but brittle fracture mode. On the other hand, hybrid type of $C_f-SiC_f/SiC$ composite gave the best mechanical property, more ductile failure mode than the $SiC_f/SiC$, and lower erosion rate than the $C_f/SiC$. During the Oxy-Acetylene torch test, the $SiO_2$ formed by reaction of the SiC matrix with oxygen prevented further oxidation or erosion of the fibers for $C_f-SiC_f/SiC$ and $SiC_f/SiC$ composites particularly. In conclusion, if a hybrid composite with low porosity is prepared, this material is expected to have high applicability as a high temperature thermo-structural composite under high temperature oxidation atmosphere by improving low mechanical property due to the oxidation of $C_f/SiC$ and brittle fracture mode of $SiC_f/SiC$ composite.

• Journal of Korea Entertainment Industry Association
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• v.13 no.4
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• pp.217-228
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• 2019

This study was designed to investigate the effect of exercise prescription service on user satisfaction and reuse intention of fitness center users in C region, Gangwon-do. The subjects of this study were 250 fitness center users aged 20 and over. Survey was conducted to examine users satisfaction and reuse intention. The final analysis data is 227 copies and the results are as follows. First, there was a significant difference in sex at the facility of satisfaction of use(t=2.308, p=.022). The marriage showed a significant difference in the price among user satisfaction(t=2.490, p=.014) and reuse intention(t=-1.968, p=.05). Age showed significant differences in the duration of participation(F=7.117, p=.000), frequency (F=6.171, p=.000), and intensity(F=2.791, p=.027). User satisfaction showed significant differences according to price(F=6.171, p=.000), leader(F=3.083, p=.017) and reuse intention(F=2.699, p=.032). There was a significant difference in education groups in terms of duration of participation(F=3.656, p=.007) and frequency(F=3.164, p=.015). leader(F=5.170, p=.001) and price(F=2.899, p=.023) were different in user satisfaction. Jobs showed a significant difference in the duration of participation(F=4.685, p=.000), intensity(F=2.373, p=.023) and reuse intention(F=4.840, p=.000). Monthly income showed a significant difference in user satisfaction(F=4.651, p=.001) and facility(F=2.606, p=.037). Second, there was a significant difference in the duration of participation according to presence or absence of exercise prescription service(t=-4.410, p=.000). There was also significant differences in the user satisfaction(t=-7.951, p=.000), leader(t=5.304, p=.000), facility(t=2.033, p=.043) and reuse intention(t=4.640, p=.000) in terms of the presence of exercise prescription service. Third, in the relation between exercise prescription service and the participation level, there was a significant effect of the leader(β=.221, p=.001) and the price(β=.135, p=.045) of user satisfaction, and the reuse intention(β=.182, p=.007). Fourth, among the user satisfaction influenced by exercise prescription service, facilities(β=.178, p=.005) and leader(β=.497, p=.000) were found to affect reuse intention.

• Journal of Life Science
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• v.28 no.3
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• pp.284-292
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• 2018

The melanin-concentrating hormone (MCH), a cyclic hypothalamic peptide composed of 17 amino acids, was initially identified in chum salmon (Oncorhynchus keta) as a regulator of pigmentation. Mammalian MCHs are cyclic hypothalamic peptides composed of 19 amino acids that regulate food intake and energy homeostasis. The present study examined not only MCH expression of different tissues but also the melanohore aggregation and intracellular $Ca^{2+}$ influx of fMCH and the other MCH. Real-time qPCR showed that MCH expressed specially in the brain, gonad, and ovary, and expression of MCH was observed during the developmental stages. In the application of synthetic fMCH and both types of synthetic fMCH, dN-fMCH and dC-fMCH, scale melanophore induced significant changes in aggregation activity with various concentrations of MCH. Also, compared to hMCH and sMCH, fMCH exhibited a 36~99.85% increase in relative potency (%), whereas aggregation of dN-fMCH and dC-fMCH remained in a high concentration. However, dispersion was induced rapidly according to be low concentration of dN-fMCH and dC-fMCH. We show that fMCH and its derivates were bound human MCHR1 and rat MCHR expressed in HEK293T cells with nano-molar affinity and are likely to be ligand-induced to mobilize intracellular $Ca^{2+}$. These results may provide new ligands for binding assay with MCHew ligands, as a structure similar to the mammalian MCH structure was discovered in fish. Once the fMCH receptor system is in place, it can be compared to the MCH system of mammals in terms of MCH function.

• Journal of the Korean Society of Food Science and Nutrition
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• v.45 no.2
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• pp.174-180
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• 2016

In this study, the effects of fermented goat milk (F-GM) on immunological activity and physical strength were examined. Splenocytes obtained from mice administered with F-GM showed increased responsinveness to mitogens, concanavalin-A (ConA), and lipopolysaccharide (LPS). Treatment with F-GM also significantly augmented production of interleukin (IL)-2 and interferon (IFN)-${\gamma}$, but not IL-4 or IL-10 from ConA-stimulated splenocytes. The activity of F-GM administration to enhance production of IL-2 and IFN-${\gamma}$ was confirmed based on mRNA expression of these cytokines by reverse transcription polymerase chain reaction. After immunization with keyhole limpet hemocyanin (KLH, 20 mg/mouse), mice administered F-GM showed significantly higher antibody titers against KLH than those of phosphate-buffered saline-treated mice, and showed the highest titer 5 weeks after KLH immunization. Analysis for determining isotypes of antibodies revealed that administration of F-GM elicited KLH-specific antibody titers of IgG1, IgG2a, and IgM. In a delayed type hypersensitivity (DTH) test carried out 7 weeks after the primary immunization, F-GM-treated mice showed a higher DTH reaction than the control mice. Furthermore, the swimming test found that administration of F-GM significantly increased swimming time. These results suggest that administration of F-GM enhances not only immune responses against antigens but also physical strength.