• Journal of the Korean Society for Nondestructive Testing
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• v.24 no.4
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• pp.341-347
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• 2004

In order to inspect the piping effectively, one of the important components in the facility of power plants, the ultrasonic guided wave was generated by a tomb transducer and was received in a non-contact fashion by using an air-coupled transducer. The guided wave modes that ran be generated by the comb transducer in piping are predicted from the theoretical dispersion curves and the element spacing of a comb transducer. Moreover, to receive the specific modes, the receiving angle of the air-coupled transducer is calculated from Snell's law between the phase velocities of guided waves and the sound velocity of air. The guided wave modes obtained in experiments are identified from the result of time-frequency analysis such as wavelet transform and two-dimensional fast Fourier transform.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.5
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• pp.772-780
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• 1987

The normal and tangential belt forces for two types of flat belts are measured and compared. From friction theory, ti was assumed that tangential friction is proportional to the actual contact area $A_{a}$ and $A_{a}$ is proportional to normal pressure P; i.e., $A_{a}$ .var.P$^{n}$ . For a flat belt with cloth backing, the n=2/3 is obtained for the constant of belt surface model. For a flat belt with rubber backing, the n=0.9 to n=1.0 is suggested as a surface model constant. The theoretical equation developed in this paper showed agood with the experimental results.

• Journal of the Korean Society of Clothing and Textiles
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• v.28 no.12 s.138
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• pp.1545-1553
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• 2004

This study assumes a bidimensional model of acculturation theory in order to understand the acculturation patterns of Korean-Americans and their fashion and shopping behavior. Bidimensional models of acculturation suggest that acculturating individuals may possess the components of both the heritage culture and the new, host culture. A combination of email and paper and pencil surveys was conducted with a convenience sample of Korean-Americans who are living in Seattle and vicinity area (n=108). The questionnaire included questions related to the respondents' and their parents' demographic information, the respondents perceived relationship with their parents, self-reported ethnic identification, ethnicity-related behaviors/attitudes, clothing involvement, shopping motivations, and fashion reference groups. The results support the bidimensional models of acculturation process as opposed to the linear model. Three different groups among Korean-Americans based on their ethnic identification pattern were found: a group with dominant Korean identity(Segregation group), a group with dominant American identity(Assimilation group), and a group with dual identity(Integration group). According to the results of MANOVA and subsequent Duncan and Scheffe tests, the Integration group showed distinct characteristics from Segregation group or Assimilation group, in terms of their ethnicity-related behaviors/attitudes, clothing involvement, shopping motivations, and fashion reference group influence.

• Journal of the Korean Society of Child Welfare
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• no.58
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• pp.205-229
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• 2017

The purpose of this study was to examine gender differences in the impact of exposure to peer delinquency among elementary school-age students and the mediating effects of aggression. The study utilized 458 cases (220 male students, 238 female students) of data from the 2015 Korea Welfare Panel Study (KoWePS) conducted by the Korea Institute for Health and Social Affairs (KIHASA). The theoretical frameworks used in this study included Bandura's social learning theory, Akers' social learning theory, and Sutherland's differential association theory. The findings were as follows. First, there was no statistically significant effect on peer group's delinquency experience overall, aggression, and delinquency experience by gender. Second, male students' delinquency experience of their peer group had a statistically significant effect on their delinquency, however, this was not true for female students. Third, in the case of male students, aggression was found to mediate the relationship between peer group delinquency experience and their own delinquency, but not for female students. From these findings, we suggest a practical and policy-driven intervention plan, focusing on reducing the contact frequency of delinquency experience and aggression, The purpose of this study was to examine gender differences in the impact of exposure to peer delinquency among elementary school-age students and the mediating effects of aggression. The study utilized 458 cases (220 male students, 238 female students) of data from the 2015 Korea Welfare Panel Study (KoWePS) conducted by the Korea Institute for Health and Social Affairs (KIHASA). The theoretical frameworks used in this study included Bandura's social learning theory, Akers' social learning theory, and Sutherland's differential association theory. The findings were as follows. First, there was no statistically significant effect on peer group's delinquency experience overall, aggression, and delinquency experience by gender. Second, male students'delinquency experience of their peer group had a statistically significant effect on their delinquency, however, this was not true for female students. Third, in the case of male students, aggression was found to mediate the relationship between peer group delinquency experience and their own delinquency, but not for female students. From these findings, we suggest a practical and policy-driven intervention plan, focusing on reducing the contact frequency of delinquency experience and aggression, which was found to adversely affect elementary school students' delinquency.

• Journal of the Korean Society for Nondestructive Testing
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• v.29 no.4
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• pp.344-350
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• 2009

The goal of this study is to introduce the theoretical background of acoustic nonlinearity in surface wave and to verify its characteristics by experiments. It has been known by theory that the nonlinear parameter of surface wave is proportional to the ratio of $2^{nd}$ harmonic amplitude and the power of primary component in the propagated surface wave, as like as in bulk waves. In this paper, in order to verify this characteristics we constructed a measurement system using contact angle beam transducers and measured the nonlinear parameter of surface wave in an Aluminum 6061 alloy block specimen while changing the distance of wave propagation and the input amplitude. We also considered the effect of frequency-dependent attenuation to the measurement of nonlinear parameter. Results showed good agreement with the theoretical expectation that the nonlinear parameter should be independent on the input amplitude and linearly dependent on the input amplitude and the $2^{nd}$ harmonic amplitude is linearly dependant on the propagation distance.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.8
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• pp.855-861
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• 2011

We predict the rolled-strip profile for a 6-high mill using thin rolling theory and a numerical model. In the numerical model, we calculate the distributions of the contact pressures between the rolls and the rolling pressure between the strip and the work roll in the transverse direction using the geometric structure of the 6-high mill and the boundary conditions. We determine the distribution of the rolling pressure in the rolling direction via a thin-foil rolling model using Fleck's theory. We calculate the three-dimensional elastic deformation of the work roll using the pressures of the width and rolling directions. We then obtain the three-dimensional strip profile via the elastic deformation of the work roll during the rolling process. The profile is verified by a thin cold-rolling test and FE simulation.

• The Journal of the Korea Contents Association
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• v.17 no.5
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• pp.410-422
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• 2017

This study researches PDA (Paralingustic Digital Affordances) in the social media on the basis of Uses and Gratification theory. The study defines PDA as Likes in Facebook and Instagram and Favorites in Twitter. The study inquiries into the motivation of using PDA and interpretational way when Social media users play a role of a sender or a receiver. For this research purpose, the focus group and interview were conducted with 36 college student in the Korea metropolitan area. The research is to comprehend the motivation and satisfaction of using PDA by applying structured theory frame of Uses and Gratification. As a result, it contributes to more satisfactions when PDA users interact each other as a sender and a receiver than mere verbal-communication. Furthermore, PDA in each social media has different meaning and gravity. For instance, Likes in Instagram is considered less important and lighter than Likes in Facebook. Moreover, people use the PDA without any restriction. People favorably use PDA most of the time, but sometimes they use in contradictory or sarcastic way.

• Composites Research
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• v.19 no.2
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• pp.28-34
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• 2006

[ $Cu-TiB_2$ ] metal matrix composites with various weight fractions of $TiB_2$ were fabricated by combination of manufacturing process, SPS (self-propagating high-temperature synthesis) and SPS (spark plasma sintering). The feasibility of $Cu-TiB_2$ composites for welding electrodes and sliding contact material was investigated through experiments on the tensile properties, hardness and wear resistance. To obtain desired properties of composites, composites are designed according to reinforcement's shape, size and volume fraction. Thus proper modeling is essential to predict the effective material properties. The elastic moduli of composites obtained by FEM and tensile test were compared with effective properties from the original Eshelby model, Eshelby model with Mori-Tanaka theory and rule-of-mixture. FEM result showed almost the same value as the experimental modulus and it was found that Eshelby model with Mori-Tanaka theory predicted effective modulus the best among the models.

• 한국체육학회지인문사회과학편
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• v.54 no.5
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• pp.705-716
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• 2015

The purpose of this research is to explore the role of Taekwondo in foreign migrant workers' adaptation process in Korean society, based on segmented assimilation concept by Portes & Zhou(1993) as a theoretical framework. In order to achieve this, an in-depth interview of 13 foreign migrant workers in Gyeonggi-region was carried out by using purpose sampling and theoretical sampling together, and the interview was analyzed using grounded theory method. The analysis result demonstrated that foreign migrant workers understand Korean culture, learn Korean, and interact with Koreans through Taekwondo, which facilitates their acculturation into the mainstream society. Also, they were assimilated into their own subculture of being fascinated by the charms of Taekwondo and trying to become Taekwondo instructors by returning to their home country. Lastly, they built a social network and overcame tough labor and the difficulties of living in a foreign country through Taekwondo. This research is significant as it examined the role of Taekwondo that preserves Korean culture and checked its value, in terms of the adaptation of foreign migrant workers who take a part in the current rearrangement of Korean society into a multicultural society.

• Information Systems Review
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• v.19 no.1
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• pp.25-48
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• 2017

As the number of Internet users has increased, the uses of social networking sites (SNSs) and online games have become universal activities across gender and ages. The extensive distribution and the usage of the Internet are beneficial to our society, but its adverse effects, such as Internet addiction, which refers to uncontrollable excessive Internet use, are becoming prevalent. Relevant social costs are also becoming troublesome. SNS and gaming addictions have negative effects on one's life, causing significant social problems. To illustrate different facets of these addictions, Problem Behavior Theory is adopted in the study. How self-esteem and perceived family environment affect SNS addiction and gaming addiction is addressed. The main subjects are Korean university students in their 20s who use SNS and play online games. The relationship between SNS addiction and gaming addiction is also addressed.