• Journal of Biosystems Engineering
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• v.36 no.6
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• pp.476-483
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• 2011

The aerial application using an unmanned helicopter has been already utilized and an attitude controller would be developed to enhance the operational convenience and safety of the operator. For a preliminary study of designing flight controller, a state space model for an RC helicopter would be identified. Frequency sweep flight tests were performed and time history data were acquired in the previous study. In this study, frequency response of the flight test data of a small unmanned helicopter was analyzed by using the CIFER software. The time history flight data consisted of three replications each for collective pitch, aileron, elevator and rudder sweep inputs. A total of 36 frequency responses were obtained for the four control stick inputs and nine outputs including linear velocities and accelerations and angular velocities in 3-axis. The results showed coherence values higher than 0.6 for every primary control inputs and corresponding on-axis outputs for the frequency range from 0.07 to 4 Hz. Also the analysis of conditioned frequency response showed its effectiveness in evaluating cross coupling effects. Based on the results, the dynamic characteristics of the model helicopter can further be analyzed in terms of transfer functions and the undamped natural frequency and damping ratio of each critical mode.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.312-316
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• 2002

Recently, mixers are being widely used in the water purification plant in order to increase the filtration efficiency. It has been found that a severe vibration was being felt on a upper structure of a mixer facility during steady state operation. The cause of the excessive vibration of the structure to which the mixer's shaft is supported has been evaluated through modal analysis on the shaft and vibration measurements during operation. The fundamental natural frequency of the mixer's shaft is found to be around 1.8 Hz and the main vibratory frequency around 30 Hz. It has been tuned out that the main vibratory frequency, 30 Hz is coincident with the fundamental holding frequency of the upper structure, and that the acceleration signal of the upper structure and the displacement signal of the mixer's shaft showed highly coherent to each other. Accordingly, it reveals that the main cause of the excessive vibration is due not to the mixer's vibration but to the natural frequency of the upper structure excited by flow turbulence.

• Journal of Korean Society for Atmospheric Environment
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• v.30 no.2
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• pp.139-149
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• 2014

A new technique, namely the combination of satellite and trajectory analysis (CSTA), for exploring the spatio-temporal distribution information of volcanic ash plume (VAP) from volcanic eruption. CSTA uses the satellite derived ash property data and a matching forward-trajectories, which can generate airmass history pattern for specific VAP. In detail, VAP properties such as ash mask, aerosol optical thickness at 11 ${\mu}m$ ($AOT_{11}$), ash layer height, and effective radius from the Moderate Resolution Imaging Spectro-radiometer (MODIS) satellite were retrieved, and used to estimate the possibility of the ash forecasting in local atmosphere near volcano. The use of CSTA for Iceland's Eyjafjallaj$\ddot{o}$kull volcano erupted in May 2010 reveals remarkable spatial coherence for some VAP source-transport pattern. The CSTA forecasted points of VAP are consistent with the area of MODIS retrieved VAP. The success rate of the 24 hour VAP forecast result was about 77.8% in this study. Finally, the use of CSTA could provide promising results for VAP monitoring and forecasting by satellite observation data and verification with long term measurement dataset.

• The Journal of Korean Association of Computer Education
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• v.8 no.2
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• pp.75-83
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• 2005

The problem of adolescents' Internet addiction is getting serious. So, preventive education of Internet addiction that cultivate right Internet use attitude is getting important. The purpose of this study is to offer a suggestion about preventive education of Internet addiction based on characteristics of adolescents' Internet addiction. We analyzed factors affecting Internet addiction by using multidimensional scale of Internet addiction for adolescent. This scale is composed of eleven factors that are mentioned by previous researches. As a result, the significant factors affecting Internet addiction are internet use time, escape from reality, anger-control, depression, family coherence, social competence, impulsivity, self-efficacy. Based on these analysis, we made a suggestion about preventive education of Internet addiction.

• 한국해양학회지
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• v.27 no.3
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• pp.228-236
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• 1992

Internal temperature oscillations of tidal periods were studied using data observed by a thermistor chain in summer of 1980 off Jukbyun on the mid-east coast of korea. The vertical stratification was well established during the observation period. The spectral energy was found to be predominant in the semidiurnal tidal band and its energy increased with depth with maximum near the bottom. The coherence in the semidiurnal band between different depths is high with a small phase difference. The results suggest the existence of the internal tide of semidiurnal period. The amplitude of internal tide was of the order of 10 m and the largest just before the disappearance of the internal tide signal.

• Proceedings of the Korea Information Processing Society Conference
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• 2023.11a
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• pp.1234-1236
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• 2023

광대역(Wideband) 통신은 신호 대역폭이 채널의 상관 대역폭(Coherence Bandwidth)를 크게 초과하는 시스템을 나타낸다. 이때, 큰 대역폭을 갖을수록 반송 주파수대역과 사용대역의 최대 및 최소 주파수 간 차이가 커지며, 통신 시스템이 겪는 채널의 주파수 선택적 페이딩 또한 커지게 된다. 수중에서 광대역 통신을 성능을 확인하기 위한 실험을 수행하였다. 실험환경으로는 송·수신기 간 수평 이격거리는 약 10m, 수직 이격거리는 약 190m로 설정하였다. 광대역 신호의 성능을 확인하기 위하여 14kHz와 30kHz의 주파수 대역과 협대역신호와의 비교를 위해 16kHz와 4kHz 대역폭 등 파라메타를 달리하여 설정하였다. x축을 Repetition Freq.와 Repetition Time의 조합으로 설정하였으며, y축을 BER(Bit Error Rate)로 성능결과를 나타내었다.

• Electronics and Telecommunications Trends
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• v.39 no.5
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• pp.98-107
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• 2024

Applications such as artificial intelligence continue to grow in complexity and scale. Thus, the demand for scalable computing is increasing for achieving faster data processing and improved efficiency. This requirement has led to the development of memory-centric computing and high-speed fabric interconnection technologies. Memory-centric computing reduces the latency and enhances the system performance by shifting the focus from the central processing unit to the memory, whereas high-speed fabric interconnects enable efficient data transfer across various computing resources. Technologies such as Gen-Z, OpenCAPI, and CCIX have been integrated into the CXL (Compute Express Link) standard since 2019 to improve communication and cache coherence. Ethernet-based interconnects such as RoCE, InfiniBand, and OmniXtend also play a crucial role in providing high-speed data transfer and low latency. We explore the latest trends and prospects of these technologies, highlighting their benefits and applications.

• Korean Journal of Childcare and Education
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• v.11 no.1
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• pp.153-171
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• 2015

The purposes of this study were to explore the relations of preschoolers' narrative representation profile types to diurnal cortisol regulation pattern at home. Fourteen story stems from the MacArthur Story Stem Battery (MSSB, Bretherton, et al., 1990) were administered to 40 preschoolers(22 boys, 18 girls, aged 5) recruited from 8 kindergartens in the Seoul and Gyeonggi areas. And also, their saliva cortisol was collected. The children's responses were aggregated into 5 dimensions, based on content themes and performance scores, which included emotions expressed and narrative coherence using the MacArthur Narrative Coding System(Robinson, et al., 2004). Data were analyzed by means of cluster analysis. Five response profiles emerged over the course of this research: Prosocial, Anxiety, Dyregulated aggression, Restricted, and Avoidance profiles. Cortisol at home showed decrease diurnal cortisol regulation patterns, however it showed a difference according to narrative response profiles. Restricted, Prosocial, and Avoidance profiles showed decrease diurnal cortisol regulation patterns. Anxiety profiles showed flat pattern, and Dyregulated aggression profile showed rising diurnal cortisol regulation pattern. These results show the preschoolers' internal representation may affect the diurnal cortisol reaction in daytime.

• Archives of design research
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• v.16 no.2
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• pp.219-232
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• 2003

Frank O. Gehry is hewn to be an architect whose design 1anguage is so arbitrary and so unexpectedly changing that it seems to be almost impossible to trace any common language or my coherence over his entire career and works. To provide a counter-argument to this conception, this study explores the transformation pattern of the design language commanded by Gehry through his works. To pursue this study, Gehry's career was divided into four periods according to the design characteristics, and thorough analysis was conducted on the transformation pattern of the language both synchronically and diachronically. Based on the analysis, it was found that Gehry had been always trying to metaphorically embody the synchronic context of any given Period into his works, and the vehicles of this embodiment were materiality and morphology. Finally the argument of this study is that the changing process of Gehry's design language is not any "revolutionary change," as it was known to be, but 〃evolutionary transformation. "on."

• The Journal of the Acoustical Society of Korea
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• v.19 no.7
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• pp.59-65
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• 2000

This paper describes the analysis of vibration characteristics through the human body as the research for voice therapy and diagnosis. The oscillation signal is not external forces but the self-voice to be pronounced the vowels ('a', 'e', 'i', 'o', 'u'). The experiment system consists of microphones, accelerometers and amplifiers. The input data are stored by the computer. At the same time, the voice is stored by the microphone and the vibration signal of the human body is stored by accelerometer. The 63 points are appointed in head, neck, trunk of human body. The positions and number of times are changeable by the purpose. The analysis parameters are amplitude, phase, fundamental. frequency, formant and the correlation of vibration signal and voice is measured by coherence function. The results show that the vibration signals have characteristic vibration in the positions of human body.