• Bulletin of the Korean Mathematical Society
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• v.47 no.6
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• pp.1213-1224
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• 2010

Using Ahlfors' covering surface method, some properties on the strong Borel direction of algebroid function of finite order are obtained. The main object of this paper is to prove existence theorem of a strong Borel direction and the existence of filling discs in such direction which briefly extends some results of meromorphic function.

• Structural Engineering and Mechanics
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• v.81 no.4
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• pp.411-428
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• 2022

This paper presents the Campbell diagram analysis of the rotordynamic system using the full order model (FOM) and the reduced order model (ROM) techniques to determine the critical speeds, identify the stability and reduce the computational time. Due to the spin-speed-dependent matrices (e.g., centrifugal stiffening matrix), several model order reduction (MOR) techniques may be considered, such as the modal superposition (MS) method and the Krylov subspace-based MOR techniques (e.g., Ritz vector (RV), quasi-static Ritz vector (QSRV), multifrequency quasi-static Ritz vector (MQSRV), multifrequency/ multi-spin-speed quasi-static Ritz vector (MMQSRV) and the combined Ritz vector & modal superposition (RV+MS) methods). The proposed MMQSRV method in this study is extended from the MQSRV method by incorporating the rotational-speed-dependent stiffness matrices into the Krylov subspace during the MOR process. Thus, the objective of this note is to respond to the question of whether to use the MS method or the Krylov subspace-based MOR technique in establishing the Campbell diagram of the shaft-disc-blade assembly systems in three-dimensional (3D) finite element analysis (FEA). The Campbell diagrams produced by the FOM and various MOR methods are presented and discussed thoroughly by computing the norm of relative errors (ER). It is found that the RV and the MS methods are dominant at low and high rotating speeds, respectively. More precisely, as the spinning velocity becomes large, the calculated ER produced by the RV method is significantly increased; in contrast, the ER produced by the MS method is smaller and more consistent. From a computational point of view, the MORs have substantially reduced the time computing considerably compared to the FOM. Additionally, the verification of the 3D FE rotordynamic model is also provided and found to be in close agreement with the existing solutions.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.15 no.1
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• pp.88-94
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• 2006

A typical disk brake system consists of caliper housing, piston, seal and two pads etc. The configuration of seal groove, dimension of piston and seal, and seal material properties are important ones for brake performance, as these affect the retraction of piston. The rubber seal is designed to perform dual functions of sealing the brake oil at brake-applied and retracting the caliper piston at brake-released. In this paper, the seal stress is analyzed using Finite Element Method and experiment is conducted by Taguchi's Method. We attempt to quantify the critical design factors in the seal groove and evaluate their impact on some of brake performance factors. The investigation obtained from this study can not only enhance the seal groove design optimization, but also reduce product prototype testing and development time.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.10
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• pp.1623-1629
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• 2003

In this paper, the arc beam is considered as a moving disc heat source with a pseudo-Gaussian distribution of heat intensity. The solution for temperature distribution on welds is derived by using the image heat source method and the superposition method. It is general solution in that it can determine the temperature-rise distribution in and around the arc beam heat source, as well as the width and depth of the melt pool (MP) and the heat-affected zone (HAZ) in welding short lengths, where quasi-stationary conditions may not have been established. As a comparative study, the results of this analytical approach has been compared with that of the finite-element modeling. As a result, The theoretical analysis presented here has shown good consistency and is more time/cost-effective method compared with FEM.

• Journal of Life Science
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• v.31 no.10
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• pp.937-943
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• 2021

In this study, antibacterial activity against pathogenic strains and antioxidant activity were measured using the red pine leaf distilled concentrate. The results of the antibacterial activity measured using an emulsion of the red pine leaf distilled concentrate by the paper disc method showed the antibacterial activities against three Gram negative pathogenic strains, E. coli, S. typhi and Vibrio parahaemolyticus and exhibited growth inhibitions of 12 mm, 10 mm and 9 mm at a 5.0% (v/v) concentration, respectively. In addition, all three strains also showed growth inhibitions even at 0.5% (v/v) concentration. However, no antibacterial activity was exhibited against gram positive bacteria. The results of the antibacterial activity using the red pine leaf distilled concentrate measured by the turbidity method, the same antibacterial activities against three gram negative pathogenic strains, E. coli, S. typhi and V. parahaemolyticus as results of the paper disc method. V. parahaemolyticus showed more than 50% growth inhibition compared to the negative control at a concentration of 5% (v/v), E. coli exhibited 33.5% growth inhibition at 4 hr incubation, and S. typhi showed 65.1% and 44.6% growth inhibitions at 4 and 5 hr incubations, respectively. Antioxidant activities of an emulsion of the red pine leaf distilled concentrate were measured by DPPH and ABTS methods. DPPH method showed the highest activity of 55.81% at a 1.0% (v/v) concentration. ABTS method exhibited the highest activity of 18.44% at a 1.0% (v/v) concentration. Through this study, it is expected that the developments of the food and the cosmetics with enhanced functionality by utilizing the antioxidant and antibacterial activities of the red pine leaf distilled concentrate.

• Journal of the Korean Wood Science and Technology
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• v.52 no.2
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• pp.134-144
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• 2024

This study aimed to analyze the anti-termite properties of tamanu (Calophyllum inophyllum L.) stem bark extracts against subterranean termites, specifically, Coptotermes curvignathus. The bark powder of C. inophyllum was extracted using different solvents, such as n-hexane, ethyl acetate, and methanol, using the maceration method. Anti-termite testing was performed using two paper disc methods: no- and two-choice tests. Whatman test paper was dripped with the extract solutions at concentrations of 4%, 6%, 8%, and 10% (w/v). Subsequently, the treated paper disc was placed into an acrylic tube, and the subterranean termite was added. The parameters utilized in the test included termite mortality and the weight loss of the test paper. The results revealed that the total extract yield of C. inophyllum stem bark was 30.24%. Furthermore, the extractive substances from C. inophyllum bark exhibited anti-termite activity. The most favorable outcomes were obtained with the n-hexane and ethyl acetate extracts at a concentration of 10%. The termite mortality and weight loss of the test paper were respectively 66% and 5.67% for the n-hexane extract and 66.67% and 6.19% for the ethyl acetate extract. In addition, the n-hexane extract contained friedelan-3-one, while the ethyl acetate extract contained 1,2-benzene dicarboxylic acid, dinonyl ester, and friedelan-3-one. The results suggested that these compounds are responsible for the observed anti-termite activity.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.34 no.4
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• pp.325-331
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• 2008

This study was carried to investigate the efficiency of antimicrobial plant extracts as natural preservative in the cosmetic formulations. Ethanol extracts of different plants were tested using the disc diffusion (paper disc) method and the minimum inhibitory concentration (MIC) method for their antimicrobial activity against the common poultry pathogens. Terminalia chebula and Rhus japonica (gallut) extracts exhibited antibacterial activity against Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli. Cinnmomum cassia extract exhibited antifungal activity against Candida albicans and Aspergillus niger while the remaining plant extracts showed no activity. A study of the preservative efficacy of the cosmetic formular containing the T. chebula, R. japonica and C. cassia extracts demonstrated sufficient preservative efficacy against bacteria and eukaryotic test microbes. Also, the cosmetic formulations containing antimicrobial plant extracts more effectively inhibited the microoranisms than the mixture of traditional chemical preservatives. These results suggest that the mixture of antimicrobial plant extracts, T. chebula, R. japonica and C. cassia is incorporated as preservative in the cosmetic formulation and the mixture have considerable effect on its efficacy.

• Journal of the Korean Applied Science and Technology
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• v.32 no.4
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• pp.731-739
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• 2015

We conducted this study to investigate possibilities of applying cosmetic material about extrats from Sparassis crispa. The extracts of Sparassis crispa conducted a antibacterial activity against Straphylococcus epidermidis, Straphylococcus aureus, Escheri chia coli, Candida albicans by the paper disc method and antioxidative effect and Nitric oxide production inhibitory activity were performed in Raw 264.7 cells. Also, we evaluated of pH, viscosity, particle observation stability of emulsion that are applied of extracts from Sparassis crispa. The antimicrobial activity showed by the paper disc method against Straphylococcus aureus, Candida albicans. The physical stability were stable of pH, viscosity in emulsion included extracts from Sparassis crispa. Emulsion containing Sparassis crispa extracts did not change particles into optical microscope. These results suggest that extracts from Sparassis crispa may have value as the potential cosmetic formulations.

• Journal of Animal Science and Technology
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• v.48 no.5
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• pp.709-718
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• 2006

In order to know the effects of Garlic, Scallion, Flavonoid, Urushiol, Anthocyanidin and Bio-MOS?? on pathogenic microbes and rumen anaerobic microbes, the growth rate of pathogens (including Escherichia coli O157, Salmonella paratyphi, Listeria monocytogenes and Staphylococcus aureus) and in vitro rumen microbial growth, gas production, ammonia concentration, carboxymethylcellulase(CMCase) activity, and microbial populations were investigated.The growth of pathogens was inhibited by supplementation of 0.1% Flavonoid, Scallion or Bio-MOS?? as biological active materials. And Scallion and Flavonoid had powerful antimicrobial properties on the pathogens applied in paper disc method.Although few effects by biological active materials disappeared in rumen fermentation in vitro, CMCase activity removed with supplementation of 1% of Flavonoid which had antimicrobial property in paper disc method. Scallion, having powerful antimicrobial property on pathogens and no inhibiting on rumen fermentation, might be a source in development of natural antimicrobial agent for ruminants.

• Journal of Life Science
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• v.29 no.7
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• pp.785-791
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• 2019

In this study, we investigated the biological antioxidant and antibacterial activity of Chamaecyparis obtusa (C. obtuse) extracts by measuring DPPH radical scavenging and ABTS radical scavenging, and SOD-like activities. The DPPH and ABTS radical scavenging activities were increased in a dose-dependent manner, with maximum activities of 78% and 62% at an extract concentration of $50{\mu}l/ml$. The C. obtusa extracts also showed high SOD-like activity, with a maximum activity of 92.85% at a concentration of $50{\mu}l/ml$. The antibacterial activities of C. obtusa extracts were measured against six types of bacteria known to cause food poisoning and disease. Antibacterial activity was investigated against three gram-positive and three gram-negative bacteria using the paper disc agar diffusion method. The C. obtusa extracts showed antibacterial activities against B. cereus, E. coli, L. monocytogenes, S. aureus, S. typhi and V. parahaemolyticus, among which the activity against B. cereus was greatest. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of C. obtusa extracts were $30-40{\mu}l/ml$ for the 6 strains that showed an antimicrobial response by the paper disc agar diffusion method. These results suggest that C. obtusa extracts could serve as potential antibacterial agents to inhibit the growth of pathogens responsible for food poisoning and disease.