• Journal of Korean Institute of Industrial Engineers
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• v.33 no.2
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• pp.237-245
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• 2007

In this paper, a modified PCF (Point Coordination Function) MAC (Medium Access Control) Protocol is proposed to support the multiple direct link communication between STAs (STAtions) in infrastructure mode IEEE 802.11 wireless LANs. By the proposed MAC protocol, the direct link communication between STAs, which are located within the communication range of each other, is allowed without the use of AP (Access Point) as a relay. Moreover, when multiple direct data communication between STAs can be simultaneously performed with a sufficiently small interference, multiple simultaneous direct link communication is allowed for the efficient use of radio bandwidth. AP polls STAs to grant the transmission opportunities using the direct link communication by transmitting the polling frames to STAs. An efficient polling method for granting the transmission opportunities to STAs is proposed to reduce the number of the polling frame transmissions and enhance the PCF MAC performance.

• Journal of Families and Better Life
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• v.31 no.6
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• pp.23-38
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• 2013

The purpose of this study was to investigate the effects of family differentiation from the family of origin, marital communication, and marital intimacy on the family strengths of married women in their twenties and thirties. The subjects were 237 married women in their twenties and thirties who live in D city. The questionnaire was consisted of measures on the family differentiation from the family of origin, marital communication, marital intimacy, and family strengths. Structural equational models were conducted with Amos 18.0. The major findings were as follows. 1) Family differentiation from the family of origin had both direct and indirect influences on the perceived family strengths of married women in their twenties and thirties. 2) Family differentiation from the family of origin had a direct effect on marital communication but no direct effect on marital intimacy. 3) Marital communication had a direct effect on marital intimacy but no direct effect on married women's perceived family strengths. 4) Marital intimacy had a direct effect on married women's perceived family strengths.

• Korean Journal of Child Studies
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• v.37 no.5
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• pp.65-82
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• 2016

Objective: The main purpose of this study was to examine the direct and indirect effects of parent-adolescent communication (through adolescent optimism) on adolescent conflict-coping styles. Methods: A total of 337 high school students participated in this study. They completed questionnaires about communications with their parents and their own optimism and conflict-coping styles. Data were analyzed using t-tests, correlations, and SEM. Results: Neither father- nor mother-adolescent communication had direct effects on adolescent conflict-coping styles. However, mother-adolescent communication had an indirect effect on conflict-coping styles, mediated by adolescent optimism. Adolescents who had open communication with mothers displayed higher levels of optimism, which led to more positive conflict-coping styles. In addition, multigroup analyses revealed that there were significant gender differences in direct and indirect effects. For boys, mother-adolescent communication directly influenced adolescent conflict-coping styles; however, father-adolescent communication did not directly or indirectly affect adolescent conflict-coping styles. For girls, neither father- nor mother-adolescent communication had direct effects on conflict-coping styles; only optimism had a significant effect on conflict-coping styles. Conclusion: The findings from this study suggest that communication with mothers and fathers have different effects on adolescents' conflict-coping styles. These findings have implications for future research and practice by emphasizing the importance of parent-adolescent communication and optimism in designing conflict-coping programs for adolescents.

• Korean Journal of Child Studies
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• v.38 no.2
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• pp.149-164
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• 2017

Objective: The purpose of the study was to examine the direct effects of parent-adolescent communication and its indirect effects through adolescent friendship quality on happiness among both middle and high school students. Methods: Participants in this study were 1,126 adolescents (667 middle school students and 459 high school students) in Seoul and Gyoung-gi Do. Data were collected through self-report questionnaires for adolescents, which included measures of parent-adolescent communication, friendship quality and happiness. Data were analyzed by t-tests, correlations, and SEM using SPSS 22.0 and Mplus 6.0. Results: For middle school students, father-adolescent communication had direct and indirect effects on happiness. However, mother-adolescent communication did not directly or indirectly affect adolescent happiness. Specifically, only father-adolescent communication had an significant indirect effect through friendship quality on adolescent happiness. For high school students, father-adolescent communication had direct effects on happiness, while mother-adolescent communication had significant indirect effects on adolescent happiness via friendship quality. Conclusion: This study underscores the importance of parent-adolescent communication and friendship quality in predicting adolescent happiness with differences in direct and indirect paths between middle and high school students. These findings emphasize the role of parent-adolescent communication and friendship quality in developing programs to improve the happiness of adolescents.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.4
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• pp.668-675
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• 2001

Recently, the performance of the commercial PCS(Personal Communication Service) system has been improved to the uppermost limit and ultimately the next generation mobile communication is to be realized by IMT-2000 (International Mobile Communication-2000) to provide multimedia services. Therefore, the new type receiving system is researched actively and one of the most important part in a receiver is direct conversion method. The direct conversion method is suitable for low power consumption, small size, MMIC, and low price, which is to be adopted to the next generation mobile communication systems. In this case, however, several problems occur due to DC-offset. The DC-offset suppresses amplification of the required signal because of the leakage signal of frequency synthesizer in the system. In this thesis, the removing method of DC-offset was considered. There are four removing techniques of DC-offset, which are AC-coupling, large capacitor, DC-feedback loop, and DC-free coding. Among these, the AC-coupling method is the most simplest method and the DC-feedback loop method has the best performance. Then, the performance of the AC-coupling method and DC-feedback loop method are evaluated by HP's ADS simulation tool. As a result, the AC-coupling method cannot be used to the digital communication systems due to data loss. On the other hand, it was confirmed that the DC-feedback loop method is suitable for the direct conversion receiver.

• Proceedings of the KIEE Conference
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• 2003.04a
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• pp.310-313
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• 2003

This paper is proposed new fuzzy controller for high performance of interior permanent magnet synchronous motor (IPMSM) drive New fuzzy controller take out appropriate amounts of accumulated control input according to fuzzy described situations in addition to the incremental control input calculated by conventional direct fuzzy controller. The structures of the proposed controller is motivated by the problems of direct fuzzy controller. The direct controller generally give inevitable overshoot when one tries to reduce rise time of response especially when a system of order higher than one is under consideration. The undesirable characteristics of the direct fuzzy controller are caused by integrating operation of the controller, even though the integrator itself is introduced to overcome steady state error in response. Proposed controller fuzzy clear out integrated quantities according to situation. This paper attempts to provide a thorough comparative insight into the behavior of IPMSM drive with direct and new fuzzy speed controller. The validity of the comparative results is confirmed by simulation results for IPMSM drive system.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.14 no.3
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• pp.13-19
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• 2014

Improvement of performances of potable communication devices such as laptops, tablets, and smart-phones enables people to do group meetings in any place. However, even though group members in a meeting locate close, data or information to be shared in the group are exchanged through the cellular networks. This increases unnecessary traffic loads in the wireless/backbone networks and as consequence it increase delays in communications. To resolve the problem, an android-based application is developed in this paper. The application utilizes Wi-Fi Direct so that all members in the meeting can direct exchange materials for the meeting without using cellular networks.

• Journal of the Korean Home Economics Association
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• v.48 no.7
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• pp.33-48
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• 2010

The purpose of this study was to explore the effects of family structure(parentral marital status and socioeconomic status), parental communication, academic problems, and peer relationship on juvenile delinquency. The participants were 1009 middle school and high school students in Seoul city and Gyeonggi Province. The major results were as follows: 1) Parental marital status(divorced/seperated) had both direct and indirect positive effects and lower class in socioeconomic status had an indirect positive effect on academic problems and peer relationship on juvenile delinquency rates. 2) Open maternal communication had a direct negative effect on juvenile delinquency rates. However, open paternal communication had both direct and indirect negative effects. 3) Academic problems had both direct and indirect positive effects on juvenile delinquency rates. 4) Peer relationship had a direct positive effect on juvenile delinquency rates. 5) The level of effects that each variable had differed by delinquency types. Based on these results, implications for preventing juvenile delinquency were discussed.

• Human Ecology Research
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• v.53 no.5
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• pp.531-542
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• 2015

This study examined the structural relationships among 4- and 5-year-old children's playfulness, communication skills, and creative characteristics. This research analyzed the direct and indirect influence of child's playfulness on communication skills and creative characteristics. The study subjects were 249 children who attend kindergartens located in the Seoul and Gyeonggi-do area. A survey questionnaire was distributed to the children's mothers and teachers. The sample was analyzed using SPSS 21.0 and AMOS 21.0 program. The parameters were estimated by maximum likelihood method. The significance of indirect effect was tested by bootstrapping at .05 level. The results of this study were: (1) in both ages 4 and 5, playfulness had a direct and positive influence on communication skills, (2) in both ages, communication skills had a direct and positive effect on creative characteristics, and (3) the 5-year-old children's playfulness had a direct effect on creative characteristics, the 4-year-old children's playfulness did not exert direct influence onto creative characteristics. Communication skills 5-year-old children were seen to precipitate a partial mediation effect between playfulness and creative characteristics. At age 4, communication skills played a full mediation variable role between playfulness and creative characteristics. Discussions include suggestions to prosper creative characteristics through enhancing a child's playfulness and communication skills.

• Journal of information and communication convergence engineering
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• v.6 no.1
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• pp.91-93
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• 2008

To realize high-speed over GHz bps, it is needed to reduce and suppress the pulse width because of dispersion effect in fiber. We analyzed the performance and waveform due to chirping effect in fiber.