• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.8 s.99
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• pp.815-824
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• 2005

In this paper, we proposed a new DGS(Defected Ground Structure) Doherty amplifier for IMT-2000 band. Originally, active load-pull analysis of a Doherty amplifier assumes ideal harmonic termination condition. However, there have been no papers considering this ideal harmonic termination condition. We obtained excellent improvements of efficiency, gain, maximum output power as well as superior size reduction of a Doherly amplifier by satisfying the overlooked assumption of ideal harmonic termination through the adaptation of DGS at the output transmission line of carrier and peaking amplifier that is essential for Doherty operation. The amount of both the 2nd and the 3rd harmonic rejection of the proposed DGS Doherty amplifier over the conventional one are 44.92 dB and over 23.77 dB, respectively. The acquired improvement in Pl dB, gain, drain efficiency, and ACPR to WCDMA 1FA signal were 0.42 dB, 0.33 dB, $6.4\%$ and 5.4 dBc, respectively. Moreover, electrical length of $90{\circ}$ is reduced at each of the DGS carrier amplifier path and DGS peaking amplifier path, therefore the whole amplifier circuit size is considerably reduced.

• Journal of Digital Contents Society
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• v.13 no.4
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• pp.501-516
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• 2012

The purpose of this study is to explore the fundamental nature and meanings of the experiences of university students with regard to their smartphone usage in order to prevent smartphone addiction and provide guidelines to develop effective interventions. Nine university students who were currently enrolled in an university located in a Korean province participated in this study. In-depth interviews were conducted from June of 2012 to July of 2012, and data were analyzed using Colaizzi's phenomenological qualitative method. As a results, five theme and 40 subthemes of experiences of problematic smartphone usage were identified. Those themes include 1) a desperate try to connect with others(exposing oneself without appropriate self-protection, seeking emotional comfort, hurt and mistrust); 2) excessive use of smartphone and loss of self-control(more smartphone usage over computer/over-immersion/excessive usage/habituation, loss of self-control); 3) psychological difficulties(excessive attachment and dependence, separation anxiety, clingingness, reduced patience) ; 4) threats to daily functioning (changes in priorities, regressed independent daily functioning, irregular daily patterns, health problems, interruptions from free messenger, academic difficulties); 5) potential for recovery(conflictual feelings and doubts over smartphone usage, importance of interpersonal(face-to-face) communications, willingness to cut down the use, hope for recovery). This study provided suggestions for the prevention effort against smartphone addiction.

• Journal of Digital Contents Society
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• v.16 no.2
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• pp.307-316
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• 2015

Although the use of CAD and CAM technologies has been broadly adopted by architecture-engineering- construction-facility management (AEC/FM) industry as the means of producing complex forms, there are still remained issues such as reducing cost, and enhancing quality and manufacturability. In this paper, to resolve given issues, we suggest a process of rationalization in digital architecture design and fabrication as an integrated approach. The rationalization, which is usually used as the term related with the skin panel of free-form architecture, is a process of re-designing a digital model to meet the requirements of manufacturing considering the gap with an original designs. Thus we classified this process and conducted a case study of fabricated models as an exploratory study. As the result, we found that each phase is connected with other phases with the circulation of information and rationalization process can be determined as the circulative process which re-designs digital model by minimally deviating from the original design based on the information deducted from analysis of inter-compatability of software and requirement of hardware.

• Journal of Digital Contents Society
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• v.16 no.2
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• pp.291-298
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• 2015

In a fast-paced information technology environment, consumption of video content is changing from one-way television viewing to VOD (Video on Demand) playing anywhere, anytime, on any device. This video-watching trend gives additional importance to videos with fine-speed-control, in addition to the strength of the digital video signal. Currently, many video players provide a fine-speed-control function which can speed up the video to skip a boring part, or slow it down to focus on an exciting scene. The audio information is just as important as the visual information for understanding the content of the speed-controlled video. Thus, a number of algorithms for fine-speed-control video-playing technologies have been proposed to solve the pitch distortion in the audio-processing area. In this study, well-known techniques for prosodic modification of speech signals, WSOLA (Waveform-Similarity-Based Overlap-Add), have been applied to analyze users' needs for fine-speed-control video playing. By surveying the users' preferred speeds on categorized video content and analyzing the results, this paper proposes that various fine-speed adjustments are needed to accommodate users' preferred video consumption.

• Journal of Digital Contents Society
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• v.16 no.2
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• pp.283-290
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• 2015

This study focused on SNS use of Chinese students who are studying in Korea. Communication media like SNS is strongly related with socialization of foreigners. Thus, it is expected to verify relationship between current SNS use tendency of Chinese students and their settlement in Korea based on analysis on the factor influencing SNS use of Chines students. For the study on the factor influencing to SNS use of Chinese students in Korea TAM model was used as a research frame. Based on TAM theory technological attribute, individual attribute and social attribute were taken out as independent variables. Perceived ease of use and perceived usefulness are applied as mediator variables. In research conclusion, some hypotheses are adopted the same as existing theory, but some hypotheses for example service quality and individual attribute are rejected as variables which influence positively to mediator variable perceived easy of use. For the next research more various variables and nationwide sampling will be needed. Based on this research it is expected to be analysed correlation between foreigners settlement in Korea and communication media like SNS.

• Journal of Digital Contents Society
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• v.16 no.2
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• pp.227-234
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• 2015

Recently, there is more and more demand on broadcasting display environment that provides a sense of realism basically with high quality and high definition as in UHDTV, so various kinds of 4K cameras have been released. Super 35mm sensor 4K/UHD cameras being generally used can be usefully applied to the single camera-based system such as advertisements, dramas, nature documentaries, and culture programs. However, in the multicamera-based system such as entertaining programs, sports, and concerts, relay broadcasting may face limitations as there are restrictions of close-up or tight shots according to the distance. Besides, 4K lenses are not enough compared with the previous HD lenses' group, so there are limitations in camera photographing shots that have been realized in HD filming. Therefore, to complement this, the use of 2/3 inch sensor 4K/UHD cameras is being demanded, and it is also needed to use various lenses' groups to produce UHD image contents. Accordingly, this study used Grass Valley's LDX 4K/UHD camera to analyze its applicability based on the picture quality test at the use of HD lenses in 2/3 sensors and also the possibility of its efficient application.

• Journal of Digital Contents Society
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• v.16 no.2
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• pp.207-218
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• 2015

This study is to design and implement Smartphone application by applying the principles and processes of narrative therapy for the participants. The application is able for participants to fight out of the difficulty in question centered on the issue, and to be able to find a positive new stories to be evolving the story of their lives as well. Therefore, using the application will help them to live a healthier life out of the problems. As a way of currying the wounded heart of the youth, narrative therapy techniques were applied to Smartphone appliances accustomed to the youth. The youths' wounded minds will not only be easily cured but also can be a important factor in determining the direction of life. In this study, narrative flow was structured into four stages; relationships, externalization, creating new stories and strengthening the new story bsed on Doll & Doll' theory. Based on them, the Smartphone application for curing the wounded heart was designed and developed by utilizing narrative therapy techniques. The application was tested by 30 University students in Jeonbuk province in Korea and the results showed that they were satisfied with the application with relation to improving their heart health.

• Journal of Digital Contents Society
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• v.15 no.4
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• pp.513-520
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• 2014

The Smart Grid is next-generation power system materialized Convergence and Integration of power technologies and Information Technologies. And this system is the next generation power system optimizing energy efficiency via real-time information exchanges grafting the information technologies upon present power networks which are web-net. The introduction of smart grid can be embodied for latitude, distributed and cooperated network by inter-active exchange of energy information between electrical power provider and consumer previous uni-directional electrical power supplement. Therefore in this paper, we proposed Convergence technologies - Smart power grid, Smart Place, Smart Renewable and Smart Electricity Service - to make smart-grid succeed via analyzing the datum. And we scoped on Convergence and Integration technologies, which could be used for smart-power-grid that is most important factor to replace previous power industries. And we brought out the expecting industrialize timing and interesting aspects and analyzed the result with survey of professional worker from institute, research center, power plant and business of power industries. And proposed the essential policies for the government and power-control-business companies based on the datum and survey output.

• Journal of Digital Contents Society
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• v.15 no.4
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• pp.481-489
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• 2014

In this paper, the automatic standby power blocking socket outlet to reduce standby power by blocking power threshold is implemented. Where, the standby power means a flowing power when a disused power electronic is plugged into the socket outlet. The proposed socket outlet can cut off the standby power by establishing a proper block power threshold electronic device according to each electronic device because it can monitor the amount of power through the smart machines such as the real-time PC or mobile phone and directly control the blocking power threshold. The software is implemented by using Visual Studio software, code vision and SN8 C studio, and the hardware is embodied in ATmega128, SN8F27E93S, USB to UART, and relay etc. Through the simulation, we find that the standby power of the proposed method is similar to that of the conventional method in case of the cellular phone but the standby power of the proposed method is much less than that of the conventional method in case of the computer, air conditioning, and set-top box. Therefore, it is proved that the proposed socket outlet has a superior performance in terms of the standby power.

• Journal of Digital Contents Society
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• v.18 no.7
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• pp.1377-1386
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• 2017

We propose a smart ocean meteorological observation system which is capable of real-time measurement of vulnerable marine climate and oceanographic conditions. Besides, imported products have several disadvantages such that they can't be measured for a long time and can't transmit data in real time. In the proposed system, smart ocean observation digging system, it observes real-time ocean weather with data logger methods. Furthermore, we also use existing dataloggers functions with various sensors which are available in the ocean at the same time. Also, we applied the Kalman-filter algorithm to the ocean crest measurement to reduce the noise and increase the accuracy of the real-time wave height measurement. In the experiment, we experimented the proposed system with our proposed algorithms through calibration devices in the real ocean environment. Then we compared the proposed system with and without the algorithms. As a result, the system developed with a lithium iron phosphate battery that can be charged by a system used in the ocean and minimized power consumption by using an RTC based timer for optimal use. Besides, we obtained optimal battery usage and measured values through experiments based on the measurement cycle.