• Journal of Magnetics
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• 제12권2호
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• pp.53-58
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• 2007

Theory of the generation linewidth of a current-driven spin-torque magnetic nano-oscillator in the presence of thermal fluctuations has been developed and a simple analytical formula for the generation linewidth in the supercritical regime of generation has been derived. It is shown that the strong dependence of the oscillator frequency on the precession power leads to substantial broadening of the generation linewidth of a spin-torque oscillator compared to the case of a linear oscillator, i.e. an oscillator with power-independent generation frequency. The relation between the nonlinearity-induced broadening of the generation linewidth and the nonlinearity-induced increase of the phase-locking band of a spin-torque oscillator to an external microwave signal has been revealed. The derived expression for the generation linewidth predicts a linewidth minimum when the nano-contact is magnetized at a certain angle to its plane, at which the nonlinear frequency shift vanishes. This result is in good agreement with recent experiments.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1997년도 춘계학술대회 논문집
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• pp.229-232
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• 1997

A free space transmission method using standard gain horn antennas in the frequency range from 9.0 to 10.5GHz is applied to determine the dielectric properties of grain such as rough rice, brown rife and barley. The dielectric constant and loss factor, which depend on the moisture content of the wetted grain are obtained from the measured attenuation and phase shift by vector network analyzer. The effect of density fluctuation, which is an important parameter governing the dielectric properties of grain, on the dielectric constant and loss factor is presented. A new density-independent model in terms of measured attenuation and moisture density is proposed for reducing the effects of density fluctuation on the moisture content measurement.

• Journal of Electrical Engineering and information Science
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• 제2권4호
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• pp.72-78
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• 1997

A free space transmission method using standard gain horn antennas in the frequency range from 9.0 to 10.5GHz is applied to determine the dielectric properties of grain such as rough rice ,brown rice and barley. The dielectric constant and loss factor, which depend on the moisture content of the wetted grain are obtained from the measured attenuation and phase shift by vector network analyzer. The moisture content of grain varied from 11 to 25% based on this wetted condition. The measured values of dielectric constants as a function of moisture density are compared with values of those obtained using he predicted model for estimating dielectric constants of grain. The effect of density fluctuation, high is an important parameter governing the dielectric properties of grain, on the dielectric constant and loss factor is presented. A new density-independent model in terms of measured attenuation an moisture density is proposed of reducing the effects of density fluctuation on the moisture content measurement.

• Journal of Electrical Engineering and Technology
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• 제12권5호
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• pp.1697-1708
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• 2017

This paper proposes an algorithm for the differential protection of an Indirect Symmetrical Phase Shift Transformer (ISPST) by considering the different behaviors of the compensated differential current under internal fault and magnetizing inrush conditions. In this algorithm, a criterion function is defined which is based on the difference of amplitude of the wavelet transformation over a specific frequency band. The function has been used for the discrimination between three phase magnetizing inrush and internal fault condition and requires less than a quarter cycle after disturbance. This method is independent of any coefficient or threshold values of wavelet transformation. The merit of this algorithm is demonstrated by the simulation of different faults in series and excitation unit and magnetizing inrush with varying switching conditions on ISPST using PSCAD/EMTDC. Due to unavailability of in-field large interconnected transformers for such a large number of destructive tests, the results are further verified by Real Time Digital Simulator (RSCAD/RTDS). The proposed algorithm has been compared with the conventional harmonic restraint based method that justifies the application of wavelet transform for differential protection of ISPST. The proposed algorithm has also been verified for different rating of ISPSTs and satisfactory results were obtained.

• 전자공학회논문지SC
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• 제37권2호
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• pp.85-95
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• 2000

본 논문에서는 입력 신호의 영점 통과점을 특정 위상 값만큼 지연시켜 주는 위상지연기(FIPS)를 사용한 브러쉬 없는 직류 전동기(BLDCM)의 센서리스 제어 방식을 제안한다. 제안한 FIPS의 검출 성능은 주파수에 무관하며 측정 잡음에 대해 강인하다. 제안한 센서리스 제어 방식은 이러한 FIPS를 사용한 것으로 기존방식에 비해 잡음에 대한 강인성과 비용 면에서 효율적이다. 성능 분석과 다양한 구동조건에서의 실험을 통해 제안한 센서리스 제어 방식의 일반성과 유용성을 입증하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1988년도 전기.전자공학 학술대회 논문집
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• pp.709-712
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• 1988

Ultrasonic Doppler Diagnostic System utilizes the Doppler effect for measurement of blood velocity. The sign of the Doppler frequency shift represents blood flow direction. CW(Continuous-Wave) Doppler System uses quadrature detection and phase rotation method to produce simultaneous independent audio and velocity signals for forward and reverse blood flow direction in the time-domain, had been fabricated. But time-domain analyzing such as audio evaluation and zero- crossing detection for instantaneous and mean frequnecy measurement do not provide both an accurate and quantitative result. Therefore, it is necessary to adopt frequency-domain technique to improve system performance. In this paper, we describe a unit which is composed of CW Doppler System and real-time spectrum analyzer (installed TMS 32010 DSP Chip). This unit shows time-dependent spectrum variation and mean velocity of Blood signal.

• Safety and Health at Work
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• 제6권1호
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• pp.25-29
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• 2015

Background: Shift work has been associated with occupational stress in health providers and in those working in some industrial companies. The association is not well established in the law enforcement workforce. Our objective was to examine the association between shift work and police work-related stress. Methods: The number of stressful events that occurred in the previous month and year was obtained using the Spielberger Police Stress Survey among 365 police officers aged 27-66 years. Work hours were derived from daily payroll records. A dominant shift (day, afternoon, or night) was defined for each participant as the shift with the largest percentage of total time a participant worked (starting time from 4:00 AM to 11:59 AM, from 12 PM to 7:59 PM, and from 8:00 PM to 3:59 AM for day, afternoon, and night shift, respectively) in the previous month or year. Analysis of variance and covariance were used to examine the number of total and subscale (administrative/professional pressure, physical/psychological danger, or organizational support) stressful events across the shift. Results: During the previous month and year, officers working the afternoon and night shifts reported more stressful events than day shift officers for total stress, administrative/professional pressure, and physical/psychological danger (p < 0.05). These differences were independent of age, sex, race/ethnicity, and police rank. The frequency of these stressful events did not differ significantly between officers working the afternoon and night shifts. Conclusion: Non-day shift workers may be exposed to more stressful events in this cohort. Interventions to reduce or manage police stress that are tailored by shift may be considered.

• 대한전자공학회논문지TC
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• 제42권1호`
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• pp.29-37
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• 2005

다중반송파 변조방식의 주요한 문제점중의 하나는 도플러 천이에 의한 주파수 옵셋에 민감하다는 점이다. 주파수 옵셋은 다중반송파 변조된 신호의 주파수 중첩으로 인한 반송파간의 간섭을 야기시킨다. 그러나 채널변화에 따른 도플러 천이는 또 다른 다이버시티 이득을 제공할 수 있는 요소가 될 수 있다. 본 논문에서는 변형된 다중반송파 코드분할 다중접속(multicarrier CDMA) 시스템을 제안함으로써 다중경로 다이버시티외에 도플러 다이버시티를 이용할 수 있게 하였다. 이를 위하여 이동 무선채널을 독립적인 시간 및 주파수 페이딩 채널로 분해하고 시간 다이버시티를 이용하는 레이크 수신기를 주파수영역으로 확장하므로써 다중경로 및 도플러 다이버시티 이득을 동시에 얻을 수 있도록 하였다.

• Transactions on Electrical and Electronic Materials
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• 제9권1호
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• pp.38-43
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• 2008

Using an arterial pressure-volume (APV) model, we performed an analysis of the conventional blood pressure estimation method using an oscillometric sphygmomanometer with computer simulation. Traditionally, the maximum amplitude algorithm (MAA) has been applied to the oscillation waveforms of the APV model to obtain the mean arterial pressure and the characteristic ratio. The estimation of mean arterial pressure and characteristic ratio was significantly affected by the shape of the blood pressure waveforms and the cutoff frequency of high-pass filter (HPF) circuitry. Experimental errors result from these effects when estimating blood pressure. To determine an algorithm independent of the influence of waveform shapes and parameters of HPF, the volume oscillation of the APV model and the phase shift of the oscillation with fast Fourier transform (FFT) were tested while increasing the cuff pressure from 1 mmHg to 200 mmHg (1 mmHg/s). The phase shift between ranges of volume oscillation was then only observed between the systolic and the diastolic blood pressures. The same results were obtained from simulations performed on two different arterial blood pressure waveforms and one hyperthermia waveform.

• 한국직업건강간호학회지
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• 제23권2호
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• pp.89-96
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• 2014

Purpose: The purpose of this study is to discover the influence of the working conditions on women workers' occupational stress. Methods: Descriptive method is used to identify women's stress depending on their general working features and conditions by conducting a survey of them in women-dominated service industries. SPSS 18.0 program is used for data analysis and descriptive statistics is presented with standard deviation, frequency and percentage. ${\chi}^2$-test is used as an analysis tool. To figure out factors that influence their stress, logistic regression analysis is used for general features and working conditions as independent variables, and occupational stress as a dependent variable. Results: As a result, among the independent variables, employment status, weekly working hours, career, shiftwork, and work-family-balance are meaningful factors that influence their stress. Temporary workers' stress is 3.65 times higher (p<.001), and workers working over 48 hours a week have 1.97 times higher stress (p<.003). Workers with over 5 years' career are under 1.73 times higher stress (p<.046) and shift workers are under 3.51 times higher stress (p<.001). Work family balance results in 1.93 times higher stress (p<.009). Conclusion: It is necessary to seek how to prevent and manage women workers' stress considering features.