• 한국전자파학회:학술대회논문집
• /
• 한국전자파학회 2003년도 종합학술발표회 논문집 Vol.13 No.1
• /
• pp.224-228
• /
• 2003

In this paper, for phase lock loop(PLL) synthesizer, we introduce a novel but simple and low cost frequency modulation(FM) circuit of a flat peak frequency deviation for modulation signal from high to very low frequency penetrating into the loop-bandwidth of PLL. The FM circuit was basically designed to compensate an amount of feedback of the loop filter in PLL. The circuit also includes the capability of the adjustment of peak frequency deviation and blocking the interference with the loop filter. The designed circuit was successfully implemented and showed the flat frequency deviation as expected in the design.

• 한국전자파학회논문지
• /
• 제15권6호
• /
• pp.599-607
• /
• 2004

이 논문은 PLL주파수 합성기의 루프 대역폭보다 높은 주파수에서 낮은 주파수까지 변화하는 신호에 대한 주파수 변조가 일정한 최대 주파수 편이를 갖도록 하는 단순하면서도 저가의 새로운 주파수 변조회로를 소개하였다. 이 주파수 변조회로는 PLL 안에서의 주파수에 따른 루프 필터의 궤환량을 보상하도록 설계되었고 최대주파수 편이값 조절과 루프와의 상호 간섭을 제거할 수 있도록 설계되었다. 또한 기존의 스펙트럼 분석기로 $\Delta$f(최대 주파수 편이)또는 $\beta$(변조 지수)를 측정하는 방법은 협대역 주파수 변조에서만 유용하여 광대역 주파수에서 측정할 수 있도록 새로운 측정방법을 제안하고 변조 신호 발생기를 이용하여 정확성을 확인하였다. 이런 한 방법으로 설계하여 제작한 회로를 측정하여 기대한 일정한 최대 주파수 편이를 가지는 것을 확인하였다.

• 한국운동역학회지
• /
• 제17권1호
• /
• pp.129-134
• /
• 2007

The purpose of this study was to determine the variability of components of the vertical ground reaction force signal to seek the suitable number of attempt datum to be analyzed during running at 2m/s and 4m/s. For this study, six subjects (height mean:$174.5{\pm}4.4cm$, weight $671.5{\pm}116.4N.$, age:$25.0{\pm}yrs.$) were selected and asked to run at least 3 times each run condition randomly. FFT(fast Fourier transform) was used to analyze the frequency domain analysis of the vertical ground reaction forces signal and an accumulated PSD (power spectrum density) was calculated to reconstruct the certain signal. To examine the deviation of the vertical ground reaction between signals collected from an different number of attempt, variability of frequency, magnitude of passive peak, time up to the passive peak and maximum load rate were determined in a coefficient of variance. The variability analysis revealed that when analyze the vertical reaction force components at 2m/s speed running, which belongs to slow pace relatively, it would be good to calculate these components from signal of one attempt, but 4m/s speed running needs data collected from two attempts to decrease the deviation of signal between attempts. In summary, when analyzing the frequency and passive peak of the vertical reaction force signal during the fast run, it should be considered the number of attempt.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1991년도 하계학술대회 논문집
• /
• pp.744-747
• /
• 1991

In this paper, the design of optimal feedforward regulators with the optimal feedforward filters for improving power frequency deviations in an interconnected system, using a polynominal LQG approach, is proposed. The performances of the regulators with the optimal feedforward filters were compared with the frequency feedback regulator only in power system by simulation. The results show that the optimal feedforward regulators reduce the power frequency standard deviation by 25%-60% in the white noise load and the peak deviation in the step load by 8%-27%.

• 수산해양기술연구
• /
• 제53권4호
• /
• pp.337-348
• /
• 2017

The tension of warp from trawler and sea-floor contact can generate tilt and wake turbulence around otter boards. Preliminary measurements of otter board tilt and 3-D flow velocity during bottom trawl operations were taken using a vector instrument to investigate the effects of wake turbulence at the trailing edge of the otter board. Tilt data (i.e., yaw, pitch, and roll) at 1 Hz and flow data (velocities in the towing, lateral, and vertical directions) at 16 Hz were analyzed to determine their periods and amplitudes using global wavelet and peak event analyses. The mean period (${\pm}standard$ deviation) of the tilt from the peak event analysis ($5{\pm}2s$) was longer or double than that of flow velocity ($3{\pm}2s$). The two periods also had a significant linear relationship. The turbulence rate of flow was 30-50% at the trailing edge and was closely related to roll deviation. The frequency of phase difference ratios (i.e., peak time differences between tilts and flow periods) was significantly different from random occurrence in two trials, possibly due to side tidal effects. However, in the other trials, flow peaks were random, as shown by the even peak times between tilts and flows. Future studies should focus on reducing tilt variation, wake turbulence, and bottom contact to stabilize otter board motion.

• Journal of Welding and Joining
• /
• 제16권6호
• /
• pp.52-58
• /
• 1998

The effect of Si content in welding wires on th arc stability was investigate, in the region of short circuit transfer and spray transfer. In the region of short circuit transfer, with increasing Si content, average arcing time and average short circuit time were increased. Therefore, droplet transfer frequency was decreased, due to the increase of arcing time and peak current at the moment of arc-reiginition was increased, due to the increase of short circuit time. In the region of spray transfer, the fluctuations of arc current and arc voltage was the most stable in wire with Si content of about 00.60 wt.%.

• 한국인터넷방송통신학회논문지
• /
• 제19권5호
• /
• pp.129-133
• /
• 2019

넓은 BW를 사용하는 위성 통신 시스템에서 주파수 자원을 최대한 효율적으로 사용하는 것은 매우 중요하다. 주파수 자원의 낭비를 초래하는 원인들 중 하나는 사용 대역의 평탄도가 좋지 못하는 경우이다. 사용 대역의 평탄도가 좋지 못한 위성 단말 송신부는 ACI와 가드밴드로 인해 주파수 자원 효율이 낮아지게 된다. 이를 극복하기 위해 본 논문에서는 위성 단말 송신부의 평탄도를 보정하는 방법을 제안한다. 우선, 선별하여 측정한 데이터로부터 최소 자승법을 만족하는 다항식을 생성하고 측정하지 않은 주파수 응답 특성을 보간 하였다. 그리고 최소 자승법을 만족하는 다항식을 이용하여 모뎀의 출력 레벨을 조절하였다. 시뮬레이션 결과 보정된 데이터는 보정 전 데이터 대비 pk-pk와 표준편차가 낮아졌고 이를 통해 평탄도가 보정되었음을 확인하였다.

• 한국정밀공학회지
• /
• 제30권10호
• /
• pp.1095-1101
• /
• 2013

The purpose of this study was to verify the effect on improvement of muscle strength unbalance according to load deviation protocol during whole body vibration exercise. Seventeen female volunteers (age $22{\pm}3$ years, height $160{\pm}4.9$ cm, weight $49{\pm}.8$ kg) participated in this experiment. The subjects performed squat exercise in WBV platform. Exercise were performed five set a day including 15 time a set, three days a week, and during 4 weeks. Vibration stimulus was 25Hz as frequency and intensity was dominant leg 1mm and non-dominant leg 4mm. The results in WBV group showed that the differences of peak torque in 16% were getting decreasing significantly after 4 weeks from 16.2% to 5.2%. This result means that WBV with load deviation protocol could provide muscle strength exercise for muscle strength balance. Our study found out that WBV of load deviation protocol could provide muscle strength exercise for improving muscle imbalance.

• 한국원자력학회:학술대회논문집
• /
• 한국원자력학회 1996년도 춘계학술발표회논문집(2)
• /
• pp.199-204
• /
• 1996

In the present the mean temperature and the temperature fluctuation of non-isothermal parallel liquid sodium jets were measured and analyzed changing the temperature difference and mean velocity of the hot and cold sodium. The sampling frequency and sampling time were 420Hz and three seconds, respectively. The wave-form characteristics were discussed in regard to the peak-to-peak amplitudes and the periods provided by a wave analysis. And also the correlations of the temperature fluctuation in rms value and the peak amplitude are derived. The overall mean accuracy ratios of the correlations are 1.07 and 1.08 with a standard deviation of 0.17 and 0.15, respectively.

• 정보과학회 논문지
• /
• 제45권3호
• /
• pp.311-320
• /
• 2018

최근 형사 및 모든 분야의 소송에서 디지털 오디오 및 비디오를 증거로써 사용하는 경우가 증가하고 있으며, 이에 디지털 포렌식 기법을 이용한 과학 수사가 발전하고 있다. 컴퓨팅 기능과 파일 편집 기술의 발달로 누구나 간단하게 비디오 파일을 조작할 수 있게 되면서 디지털 데이터를 조작하는 사례는 증가하고 있으며, 이로 인해 디지털 데이터에 대한 감정을 통해 증거의 무결성과 신뢰성을 확보하는 일이 요구되고 있다. 본 연구에서는 디지털 포렌식 기법 중 하나로 전력 공급에 대한 지리적 환경에 따른 전력망 그리드를 통해 전력망 주파수 신호(Electrical Network Frequency: ENF)를 추출하고 QIFFT를 이용해 peak 검출을 위한 신호처리 과정을 거치는 기법에 대해 제안한다. 그리고 표준편차를 이용한 탐지 알고리즘을 통해 73%의 정확도로 비디오 파일의 위변조 여부 확인 및 위변조 지점을 찾는 실험을 진행하고 이를 검증하였다.