• Journal of the Korean Vacuum Society
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• v.14 no.3
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• pp.153-158
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• 2005

The effective mean free path model was adopted to examine the thickness effect on the thermoelectric properties of flash-evaporated n-type $Bi_2Te_{2.4}Se_{0.6}$ thin films. Annealing effects on the electron concentration and mobility were also studied, and their variations were analyzed in conjunction with antisite defects. Seebeck coefficient and electrical resistivity versus inverse thickness showed a linear relationship, and the mean free path was found to be $5120\AA$ Electron mobility was increased by annealing treatment and electron concentration was decreased considerably due to reduction of antisite defects, so that electrical conductivity was decreased and Seebeck coefficient was increased. When annealed at 473k for 1 hour, Seebeck coefficient and electrical conductivity were $-200\;\mu V/k\;and\;510\omega^{-1}cm^{-1}$, respectively. Therefore, the thermoelectric power factor was improved to be $20\times10^{-4}\;W/(mK^2)$.

• Applied Chemistry for Engineering
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• v.23 no.3
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• pp.253-258
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• 2012

The effects of active sites and valence states were investigated over $Pd/TiO_2$ catalyst on simultaneous oxidation of $CH_4$ and CO. The Pd species (PdO) crystallite size increased with increasing Pd loadings, which results in enhancement of the activity of $CH_4$ oxidation. Different results from the activity of $CH_4$ and CO oxidation were shown to be dependent on the Pd valence state on the surface of the catalyst prepared through a thermal treatment. XRD and $H_2-TPR$ analysis confirmed that $Pd^{2+}$species was predominated in the calcination catalyst, while $Pd^0$species was predominated in the reduction catalyst. Additionally, it could be found that the valence state of Pd was a more important factor on the catalytic activity than that of factors as the surface area and pore volume. The reaction mechanism of $CH_4$ and CO followed by the valence state of Pd could be identified using FT-IR analysis.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.1
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• pp.54.2-54.2
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• 2014

IGRINS (Immersion GRating Infrared Spectrograph) is a high spectral resolution near-infrared spectrograph that has been developed in a collaboration between the Korea Astronomy & Space Science Institute and the University of Texas at Austin. By using a silicon immersion echelle grating, the size of the fore optics is reduced by a factor of three times and we can make a more compact instrument. One exposure covers the whole of the H- and K-band spectrum with R=40,000. While the operation of and data reduction for this instrument is relatively simple compared to other grating spectrographs, we still need to operate three infrared arrays, cryostat sensors, calibration lamp units, and the telescope during astronomical observations. The IGRINS Instrument Control Software consists of a Housekeeping Package (HKP), Slit Camera Package (SCP), Data Taking Package (DTP), and Quick Look Package (QLP). The SCP will do auto guiding using a center finding algorithm. The DTP will take the echellogram images of the H and K bands, and the QLP will confirm fast processing of data. We will have a commissioning observations in 2014 March. In this poster, we present the performance of the software during the test observations.

• Journal of the Korean Solar Energy Society
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• v.39 no.6
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• pp.127-135
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• 2019

In this study, we analyzed the relationship between five factors: long-wave radiation, short-wave radiation, cloudiness, SVF and summer shelters. In the previous study, we recognized the correlation between single building SVF and long-wave radiation. Furthermore, this study attempted to confirm the relationship at the summer shelter with high solar radiation blocking rate. The observations are as follows. ① Cooling in summer shelters was not the effect of temperature but the effect of radiation reduction due to short-wave radiation shielding. ② In the case of the canopy tent with low heat capacity, the long-wave radiation was observed to be 16.7% higher per hour than the comparison control point due to the increase in surface temperature. ③ The long-wave radiation increase rate was different according to SVF, but showed very similar pattern according to the material characteristics of the summer shelters. ④ Passive Cooling effect on the type of summer shelters are determined by the size of the total long and short-wave radiation at that point.

• Journal of Society of Preventive Korean Medicine
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• v.14 no.1
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• pp.97-110
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• 2010

The wound healing process can be categorized as follows : inflammation, fibroplasia, neovascularization, collagen deposition, epithelialization, and wound contraction. During the healing process, various growth factors are secreted to accelerate wound healing. Previous studies have demonstrated that endogenous growth factors, such as vascular endothelial growth factor(VEGF) are the important regulatory polypeptides for coordinating the healing process. They are released from macrophages, fibroblasts, and keratinocytes at the site of injury and participate in the regulation of reepithelization, granulation tissue formation, collagen synthesis and neovascularization. Onchung-Um has been used clinically to treat various skin diseases. In addition, Onchung-Um has been also used for congestive inflammations. In the present study, we evaluated the effects of Onchung-Um on wound healing process and wound size reduction in rats. Full-thickness skin wounds ($15mm\;{\times}\;15mm$) were created on the back of rats. Rats were then divided into 2 groups : The Onchung-Um treated group that was orally administered with a dose of 193.9mg/100g of Onchung-Um extract per day for 15 days and Control group without Onchung-Um administration. Moreover, the histological changes and VEGF immunoexpressions of two groups were estimated. In results, wound closures were significantly accelerated by oral administration of Onchung-Um extract. Furthermore, in Onchung-Um treated group, there were significant increases in fibroblast migration, epithelialization compared with the Control group. VEGF expressions were also increased in Onchung-Um treated group. This study has therefore demonstrated the Onchung-Um can significantly improve the quality of wound healing and scar formation and the oral administration of Onchung-Um extract may increase early tissue angiogenesis in the incisional wound of an experimental animal model.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.6
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• pp.3692-3697
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• 2015

A screw is a type of fastener characterized by a helical ridge known as thread. The demands for screws with the miniaturization and weight reduction are increasing for the trend of small size of mobile devices. The successful designs of mold and process are very important to obtain screws with good mechanical properties and high precision. In this study, the design of cold forging process of micro screw was carried out by using finite element method. In particular, in order to investigate the effects of die geometries and friction, design of experiment method was adopted and it was revealed that the friction was the dominant factor of folding defects. From these results, the design of die was modified and experiments were carried out with the modified die. From the experimental results, it was found that the folding defects disappeared.

• Journal of Drive and Control
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• v.14 no.4
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• pp.1-8
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• 2017

The Down-the-Hole hammer is one of the pneumatic drill equipment used for grinding, drilling, and mining. One the advantages of which is that a reduction work efficiency at deep site are relatively small compared to other drilling methods. Due to the large vibration in the underground area, it is difficult to measure the performance of the hammer, and hammer testing requires substantial production cost and operating expenses so research on the development of the hammer is insufficient. Therefore, this study has developed a dynamic simulation model that apprehends the operating principles of an 8-inch DTH hammer and calculates performance data such as performance impact force, piston speed, and BPM. By using the simulation model, design factors related to strike force and BPM were selected, and the influence of each design factors on performance was analyzed through ANOVA analysis. As a result, be the most important for BPM and the strike force are position of upper port that push the piston in the direction of the bit and in BPM, the size of the empty space between the bits and the piston is the second most important design factor.

• Journal of the Korea Society of Computer and Information
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• v.24 no.5
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• pp.93-102
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• 2019

The nation's fraternity and elite players who have built up a global bicycle infrastructure often find it to be a problem with the bicycle's speed and speed reduction, pain in knees and hip joints, or even with the bike itself, or with the bike's own physical defects or a riding posture. However, we found that most cases of cleat adjustment errors were likely to be true. Accurate adjustment of the cleats is the most important of the entire fitting process and can be the basis for improving the ability of the bicycle rider and preventing injury. Therefore, the study was intended to give a prior study of bicycle fitting, which can improve bicycle efficiency and prevent injury when riding bicycle, and specific ways of adjusting bicycle shoe cleats, and the following results were obtained. First, the cleat characteristics of Shimano, LOOK and Speedplay, which are currently used in public, and the characteristics during the cleat adjustment process, were derived. In addition, the structure and characteristics of dedicated shoes using cleats and the method of using pedalling by the structure of shoes after adjusting the cleats were derived. Second, the position of the shoe and its relationship with torque in pedalling was discussed, and the method of adjusting front and back of cleats was derived. Third, leg length, ASIS, Q-Angle and Q-factor etc. were analyzed and the method of setting and adjusting cleat left and right values were derived. Fourth, the relationship between walking angle and cleat rotation was analyzed, the method was derived, and the torque size and angle behind the cleat adjustment were compared and analyzed using the spinner to indicate the torque and the effective mean torque angle after the cleat adjustment.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.9
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• pp.801-811
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• 2021

Lightning can deliver large amounts of energy to the aircraft in a short period of time, resulting in catastrophic consequence. In particular, lightning strikes accompanied by high temperature heat and current can damage aircraft surface and internal electronic equipment, seriously affecting flight safety. Lightning experiments to analyze this effect use a Component A waveform with a maximum current of 200 kA as specified in SAE ARP 5412B. However, the actual lightning occurs mostly below 35kA and lightning indirect tests are conducted by reducing waveforms to prevent damage to internal electronic equipment. In this study, we examine previous methods to plot the Component A reduced waveform and identify their limitations. We then propose a new method to plot the reduced waveform based on adjusting the correction factor of the aircraft lightning Component A waveform. Finally, the electromagnetic analysis software EMA3D was used to compare the internal induced current size reduction ratio of the internal cable harness of the EC-155B helicopter.

• The Korean Journal of Franchise Management
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• v.13 no.4
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• pp.39-48
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• 2022

Purpose: COVID-19 has negatively influenced the financial performance of restaurant firms. Previous literature suggests that the franchising strategy effectively helps restaurant firms recover from difficult business conditions through various methods for expanding business size and enhancing business efficiency. According to risk-sharing theory, restaurant franchisors may minimize operational risks by sharing the risks with their franchisees. For instance, restaurant franchisors could generate more stable cash flow using franchise fees from their franchisees. However, research on the effect of franchise's risk reduction factor on business performance during pandemic is scarce. Thus, this study aims to examine the positive moderating effect of franchising between COVID-19 and restaurants' financial performance. Research design, data, and methodology: Panel data including financial information and franchising status of restaurant firms were collected for analysis. In order to control for unobserved firm-specific factors, generalized least squared estimation in fixed effects model was conducted. Huber-White robust standard errors were used to deal with heteroscedasticity issues. Results: It was found that COVID-19 pandemic has a negative effect on the restaurants' financial performance such as ROA (return on assets), ROE (return on equity), and PM (profit margins), which confirms the findings from existing literature. More importantly, results show that the degree of franchising has a positive moderating effect on the relationship between COVID-19 and financial performance of restaurant firms. This suggests that more active engagement in franchising may decrease negative impacts of COVID-19 on the restaurants' financial performance. Conclusions: The study supports existing literature related to risk-sharing theory, by confirming that pandemics, such as COVID-19, negatively affect financial performance of the restaurants. Furthermore, it was found that franchising strategy can help lessen negative impacts of pandemics on the firm performance. These findings can contribute to the franchise and restaurant management literature by suggesting the role of franchising in reducing business risks, thereby positively affecting financial performance. Moreover, this study offers business managers of franchisors and franchisees insights for utilizing franchising in restaurant risk management. Policymakers may also gain information on aiding restaurant firms during global crisis, such as COVID-19.