• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.7
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• pp.434-441
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• 2016

Friction Stir Welding (FSW) is a solid-state joining process involving the frictional heat between the materials and tools. The amount of heat conducted into the workpiece determines the quality of the welded zone. Excessive heat input is the cause of oxides and porosity defects, and insufficient heat input can cause problems, such as tunnel defects. Therefore, analyzing the temperature history and distribution at the center of the Friction Stir Welded zone is very important. In this study, the temperature distribution of the friction stir welding region of an AZ61 magnesium alloy was investigated. To achieve this goal, the temperature and metal flow was predicted using the finite element method. In FE analysis, the welding tool was simplified and the friction condition was optimized. Moreover, the temperature measuring test at the center of the welding region was performed to verify the FE results. In this study, the tool rotation speed was a more dominant factor than the welding speed. In addition, the predicted temperature at the center of the welding region showed good agreement with the measurement results within the error range of 5.4% - 7.7%.

• Proceedings of the Korea Contents Association Conference
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• 2009.05a
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• pp.597-601
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• 2009

The purpose of this study is to closely examine the effect of exercise behavior change of casino securities on their physical self-description. This observation takes place in casino enterprises in Seoul, Busan, Kangwon and Jeju. Within these areas, we have selected companies with more than 30 securities. Among 450 persons sampling unit, we have excluded 77 copied which seem to be insincere, and actually used 373 copies in this study. Evaluation forms are used as a study method; each form consists of continuance 5 points Likert scales and nominal/proportional scaling and used after excluding a test through the analysis of validity and reliability. After encoding and inputting the framing completed data along with each purpose, it was computerized by computer process, making use of SPSS 15.0 version. Through the data analysis according to these methods and procedures, the result on this study is described below. First, the exercise behavior according to socio-demographic characteristics. Second, the decision-making balance according to socio-demographic characteristics. Third, the self-efficacy according to socio-demographic characteristics. Fourth, the physical self-concept according to socio-demographic characteristics. Fifth, the exercise behavior influence indirectly on the physical self-concept throughout the decision-making balance and self-efficacy.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.3
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• pp.249-257
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• 2017

Filtering the data for travel time records obtained from DSRC probes is essential for a better estimation of the link travel time. This study addresses the major deficiency in the performance of TRANSGUIDE in removing anomalous data. This algorithm is unable to handle unstable traffic flow conditions for certain time intervals, where fluctuations are observed. In this regard, this study proposes an algorithm that is capable of overcoming the weaknesses of TRANSGUIDE. If TRANSGUIDE fails to validate sufficient number of observations inside one time interval, another process specifies a new validity range based on the median absolute deviation (MAD), a common statistical approach. The proposed algorithm suggests the parameters, ${\alpha}$ and ${\beta}$, to consider the maximum allowed outlier within a one-time interval to respond to certain traffic flow conditions. The parameter estimation relies on historical data because it needs to be updated frequently. To test the proposed algorithm, the DSRC probe travel time data were collected from a multilane highway road section. Calibration of the model was performed by statistical data analysis through using cumulative relative frequency. The qualitative evaluation shows satisfactory performance. The proposed model overcomes the deficiency associated with the rapid change in travel time.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.40 no.2
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• pp.141-153
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• 2014

This study is about the development of cholesteric liquid crystals (CLCs), which are highly applicable to cosmetics formulation. The CLCs made from non-animal origin were chosen not only because they are free of animal viruses but also because they give a sense of security to the cosmetic consumers. Three kinds of new cholesteric derivatives (CI, CC, CN) were synthesized using non-animal cholesterol [NAB cholesterol (ARCH LONZA)], which was originally made by fermentation process. To develop high applicability to cosmetics formulation, we attempted to find out the optimum compositions in which CLCs can maintain their color over a wide range of temperature. The CLCs in 41 different compositions were prepared by the combinations of three cholesteric derivatives and a visual evaluation method was employed to determine the range of temperature at which the CLCs display their color. The 205 UV-VIS spectral data obtained from 41 CLCs at various temperatures were simultaneously analyzed to investigate the critical factors affecting the characteristics of the CLCs. Results showed that A4, A5, A6 and A7 were the best compositions to cosmetics formulation. A6 composition had a great moisturizing effect by the artificial skin test ($AmoReSkin^{TM}$).

• International Journal of Highway Engineering
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• v.17 no.6
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• pp.11-18
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• 2015

PURPOSES : The purpose of this thesis is to evaluate the effectiveness of an active noise cancellation (ANC) system in reducing the traffic noise level against frequencies from the predictive model developed by previous research. The predictive model is based on ISO 9613-2 standards using the Noble close proximity (NCPX) method and the pass-by method. This means that the use of these standards is a powerful tool for analyzing the traffic noise level because of the strengths of these methods. Traffic noise analysis was performed based on digital signal processing (DSP) for detecting traffic noise with the pass-by method at the test site. METHODS : There are several analysis methods, which are generally divided into three different types, available to evaluate traffic noise predictive models. The first method uses the classification standard of 12 vehicle types. The second method is based on a standard of four vehicle types. The third method is founded on 5 types of vehicles, which are different from the types used by the second method. This means that the second method not only consolidates 12 vehicle types into only four types, but also that the results of the noise analysis of the total traffic volume are reflected in a comparison analysis of the three types of methods. The constant percent bandwidth (CPB) analysis was used to identify the properties of different frequencies in the frequency analysis. A-weighting was applied to the DSP and to the transformation process from analog to digital signal. The root mean squared error (RMSE) was applied to compare and evaluate the predictive model results of the three analysis methods. RESULTS : The result derived from the third method, based on the classification standard of 5 vehicle types, shows the smallest values of RMSE and max and min error. However, it does not have the reduction properties of a predictive model. To evaluate the predictive model of an ANC system, a reduction analysis of the total sound pressure level (TSPL), dB(A), was conducted. As a result, the analysis based on the third method has the smallest value of RMSE and max error. The effect of traffic noise reduction was the greatest value of the types of analysis in this research. CONCLUSIONS : From the results of the error analysis, the application method for categorizing vehicle types related to the 12-vehicle classification based on previous research is appropriate to the ANC system. However, the performance of a predictive model on an ANC system is up to a value of traffic noise reduction. By the same token, the most appropriate method that influences the maximum reduction effect is found in the third method of traffic analysis. This method has a value of traffic noise reduction of 31.28 dB(A). In conclusion, research for detecting the friction noise between a tire and the road surface for the 12 vehicle types needs to be conducted to authentically demonstrate an ANC system in the Republic of Korea.

• International Journal of Highway Engineering
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• v.13 no.4
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• pp.19-28
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• 2011

This study developed a solar radiation reflection pavement, so called a cool pavement, to lessen the urban heat island effect by coating a pavement surface with acrylic resins mixed with light-colored pigments. From a laboratory test, simulating solar heating process in pavements, the cool pavement reduced more than $12^{\circ}C$ of pavement temperature at $60^{\circ}C$ compared to a control porous pavement. With the increase of the mixing ratio of the pigments to acrylic resins, the temperature reduction effect increased, but its workability became worse due to higher viscosity. As a result, an appropriate mixing ratio was determined as 15%. The cool pavement had better durability than the control pavement: One quarter of Catabro loss and twofold dynamic stability. Its adhesion was also higher enough not to be debonded under traffic loading. In-situ noise and friction tests conducted in two field sites showed that the cool pavement reduced its noise level by 3.7dB in average and increased its friction level by 30% compared to the control pavement. The permeability of the cool pavement was little lower than the control pavement, but higher enough to satisfy the minimum requirement for porous pavements.

• Journal of radiological science and technology
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• v.32 no.2
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• pp.161-168
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• 2009

The carotid intima-media thickness (IMT) is an early structural marker of the atherosclerotic process and is the only non-invasive test that is currently recommended by the American Heart Association for evaluation of the risk. However, use of this parameter has a limitation because it assumes uniform thickness throughout the blood vessel, whereas atherosclerosis is a focal phenomenon that is confined to intima. In fact, plaque can be found along the atherosclerotic blood vessels even though its value is unknown. The aim of this study is to analyze the carotid plaque and IMT in the stroke patients. We investigated the patients with ischemic stroke, who were admitted to the department of neurology at the Stroke Special Hospital from January to March 2008. After the carotid IMT and plaque were assessed by B-mode ultrasonography, IMT and carotid plaque to risk variables (age, sex) were analyzed. The distribution of CCA IMT was significantly different in terms of age (p = 0.004). Likewise, the distribution of carotid plaque was also significantly different in terms of age (p = 0.006). Carotid plaque was 69 and 92% in normal and abnormal CCA IMTs respectively. The results showed that the CCA IMT was closely associated with carotid plaque.

• Journal of the Korean Wood Science and Technology
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• v.45 no.6
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• pp.836-845
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• 2017

Gravimetric method is usually used to evaluate air-dry density, which is governing physical or mechanical properties of wood. Although it had high evaluation accuracy, the method is time consuming process. Thus, this study was conducted to estimate air-dry density of wood with high accuracy by using polychromatic X-ray and digital detector as alternative of gravimetric method. To quantify polychromatic X-ray projection for evaluating air-dry density, Lambert-Beer's law with the integral value of probability function was used. The integral value was used as weighting factor in the law, and it was determined by conducting simple test at various penetration depths and tube voltage. Mass attenuation coefficient (MAC) of wood also calculated by investigating polychromatic X-ray projection according to species, penetration depth and tube voltage. The species had not an effect on change of MAC. Finally, an air-dry density of wood was estimated by applying the integral value, MAC and Lambert-Beer's law to polychromatic X-ray projection. As an example, the relation of the integral value (${\alpha}$) according to penetration depth (t, cm) at tube voltage of 35 kV was ${\alpha}=-0.00091t{\times}0.0184$ while the regression of the MAC (${\mu}$, $cm^2/g$) was ${\mu}=0.5414{\exp}(-0.0734t)$. When calculation of root mean squared error (RMSE) was performed to check the estimation accuracy, RMSE at 35, 45 and 55 kV was 0.010, 0.013 and $0.009g/cm^3$, respectively. However, partial RMSE in relation to air-dry density was varied according to tube voltage. The partial RMSE below air-dry density of $0.41g/cm^3$ was $0.008g/cm^3$ when tube voltage of 35 kV was used. Meanwhile, the partial RMSE above air-dry density of $0.41g/cm^3$ decreased as tube voltage increased. It was conclude that the accuracy of estimation with polychromatic X-ray and digital detector was quite high if the integral value and MAC of wood were determined precisely or a condition of examination was chosen properly. It was seemed that the estimation of air-dry density by using polychromatic X-ray system can supplant the gravimetric method.

• Journal of Environmental Science International
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• v.20 no.12
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• pp.1585-1598
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• 2011

Emission reduction program for in-use diesel vehicles (ERPDV) has been enacted since 2004 over the Seoul metropolitan area, and diesel emission reduction is forced to fulfill this regulation. This study was performed to evaluate the ERPDV using $PM_{10}$ concentrations of both road-side monitoring and national background network during the period of 2004-2010. In order to assess the pure road emission, we first eliminated the long range transport effect by deducting the trend of annual national background concentrations from the road-side $PM_{10}$ concentrations, and then analyzed the time series of the resultant $PM_{10}$ concentrations over Seoul metropolitan area. The annual rates of variations of road-side $PM_{10}$ with the deduction of trend of background level show -3.2, +0.4, and -2.4 ${\mu}g/m^3$/year, in Seoul, Incheon, and Gyonggi province, respectively. There are steadily decreasing trend in Seoul with all of statistic parameters such as mean, mediam, 5%ile, 10%ile, 25%ile, 75%ile, 90%ile, and 95%ile concentrations. Incheon shows some fluctuations with positive with no significant trend, and Gyonggi province shows overall decreasing but not consistent. Student-t test shows 95% significant level of ERPDV effect in Seoul, but there exists no significant level greater than 90% in both Incheon, and Kyonggi province. Total annual averaged trend over the whole Seoul metropolitan area is estimated to lie in approximately $-2.9{\mu}g/m^3$/year in this study, implying the intimate involvement of ERPDV to a large extent. This is also suggesting that the further research cost-effectiveness of ERPDV with consideration of the long range transport process would be needed over the Seoul metropolitan area.

• Journal of Life Science
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• v.19 no.10
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• pp.1389-1395
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• 2009

Generally, it takes a long time to purify wood vinegar, and it contains toxic compounds such as tar, methanol, phenol and benzopyrene. To reduce the toxicity of wood vinegar itself, we have developed a new purification method of wood vinegar using an oxidation-cohesion reaction and distillation with an active carbon. We have investigated the physico-chemical change (pH, specific gravity, refractive index and dissolved tar), the change of amount of toxic compounds (carbonyl group, phenol, benzopyrene and residual solvents) and organic acids (formic acid (FA), acetic acid (AA), propionic acid (PA)) of the purified wood vinegar under the long term and accelerated storage conditions. Also, we have evaluated the effect of the purified wood vinegar on hair growth using an alopecia model of C57BL/6 mice. As a result, we could find out that the purified wood vinegar was stable and remained without decay under the storage conditions and benzopyrene, a carcinogenic agent, was not detected in the purified wood vinegar. After topical treatment of the purified wood vinegar solution or minoxidil (MXD) for 2 weeks to dorsal skin, the hair regrowth of the mice accelerated faster than that of the control, with no clinical signs. In conclusion, we could suggest a guideline for quality control of process to reduce the toxic compounds in wood vinegar and it might be a useful hair growth promoter in the treatment of baldness or alopecia.