• JSTS:Journal of Semiconductor Technology and Science
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• v.12 no.1
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• pp.107-116
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• 2012

In this paper, the trade-off related to bandwidth of high-speed common-mode logic frequency divider is analyzed in detail. A method to optimize the operating frequency, band-width as well as power consumption is proposed. This method is based on bipolar device characteristics, whereby a negative resistance model can be used to estimate the optimal normalized upper frequency and lower frequency of frequency dividers under different conditions, which is conventionally ignored in literatures. This method provides a simple but efficient procedure in designing high performance frequency dividers for different applications. To verify the proposed method, a static divide-by-2 at millimeter wave ranges is implemented in 180 nm SiGe technology. Measurement results of the divider demonstrate significant improvement in the figure of merit as compared with literatures.

• Magazine of the Korean Society of Agricultural Engineers
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• v.41 no.5
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• pp.53-67
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• 1999

In this study, regional frequency analysis is used to determine each subbasin drought frequency with watershed runoff which is calculated with Tank Model in Nakdong river basin. L-Monments methd which is almost unbiased and nearly normal distribution is applied to estimate paramers of drought frequency analysis of monthly runoff time series. The duration of '76-77 was the most severe drought year than othe rwater years in this study. To decide drought frequency of each subbasin from the main basin, it is calculated by interpolaing runoff from the frequency-druoght runoff relationship. and the linear regression analysis is accomplished between drought frequency of main basin and that of each subbasin. With the results of linear regression analysis, the drought runoff of each subbasin is calculated corresponing to drought frequency 10,20 and 30 years of Nakdong river basin considering safety standards for the design of impounding facilities. As the results of this study, the proposed methodology and procedure of this study can be applied to water budget analysis considering safety standards for the design of impounding facilities in the large-scale river basin. For this purpose, above all, it is recommanded that expansion of reliable observed runoff data is necessary instead of calculated runoff by rainfall-runoff conceptual model.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.2
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• pp.271-278
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• 1987

The experimental study was carried out to investigate the pressure fluctuation, operating frequency, noise emission and combustion characteristics in an aero-valved pulsating combustor. Measurements of the pressure fluctuation, mean temperature and ion current inside the combustion chamber indicate that combustion phenomena are characteristically similar to those in the diffusion flame. The measured frequency schedue indicates that the acoustic theory of the quarter wave tube can be approximated to give the operating frequency, but correction factor must be involved to estimate the correct operating frequency. The spectral behavior of the noise emission exhibits that frequency bands with high noise intensity are narrowly restricted to the neighborhood of the operating frequency signalling the low-frequency combustion characteristics of the pulsating combustor. Measurements of the operating characteristics as variation of the fuel nozzle diameter and injection angle with 4 fuel nozzles have been made, and it was found that the system produced the stable operating conditions up to the turn down ratio of 3 when the fuel nozzle diameter is 1.2mm, and the optimum fuel injection angle is thought to be in the neighborhood of 30.deg. radially.

• Journal of Power Electronics
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• v.5 no.1
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• pp.11-19
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• 2005

This paper describes the two control techniques to perform the sensorless vector control of a PMSM by injecting the high frequency voltage to the stator terminal. The first technique is the estimation algorithm of the initial rotor position. A PMSM possesses the saliency which produces the ellipse of the stator current when the high frequency voltage is injected into the motor terminal. The major axis angle of the current ellipse gives the rotor position information at a standstill. The second control technique is a sensorless control algorithm that injects the high frequency voltage to the stator terminal in order to estimate the rotor position and speed. The rotor position and speed for sensorless vector control is calculated by appropriate signal processing to extract the position information from the stator current at low speeds or standstill. The proposed sensorless algorithm using the double-band hysteresis controller exhibits excellent reference tracking and increased robustness. Experimental results are presented to verify the feasibility of the proposed control schemes. Speed, position estimation and vector control were carried out on the floating point processor TMS320VC33.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10a
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• pp.165-168
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• 1996

In this paper, we propose a design method of PID adaptive controller based on frequency domain analysis. The method is based on the estimation of a nonparametric process model in the frequency domain and the determination of the PID controller parameters by achieving partial model matching so as to minimize a performance function concerning to relative model error between the loop transfer function of the control system and the desired system. In the design method the process is represented only by a discrete set of points on the Nyquist curve of the process. Therefore it is not necessary to estimate a full order parameterized process model.

• Journal of Industrial Technology
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• v.20 no.A
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• pp.159-167
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• 2000

In the study rainfall frequency analysis attemped the many specific property data record duration it is differance from occur to error-term and probability ditribution of concern manifest. error-term analysis of method are fact sample data using method in other hand it is not appear to be fault that sample data of number to be small random variates. Therefore, day-rainfall data: to randomicity consider of this study sample data to the Monte Carlo method by randomize after data recode duration of form was choice method which compared an assumed maternal distribution from splitting frequency analysis consequence. In the conclusion, frequency analysis of chuncheon region rainfall appeared samll RMSE to the Gamma II distribution. In the rainfall frequency analysis estimate RMSE using random variates great transform, RMSE is appear that return period increasing little by little RMSE incresed and data number incresing to RMSE decreseing.

• Korean Journal of Optics and Photonics
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• v.10 no.1
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• pp.68-72
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• 1999

We demonstrate a new pulse characterization scheme relying on self-heterodyning that uses intracavity frequency shifter in a fiber soliton laser with frequency shifted feedback. By heterodyning the frequency-shifted pulse stream with the unshifted one, and by measuring the beat strength with varying the delay length between two pulse streams, we obtain the amplitude autocorrelation function from which we estimate the pulsewidth. The result is in good agreement with that obtained by the autocorrelation relying on the second harmonic generation.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.3
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• pp.629-631
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• 2007

In hands-free full-duplex communication systems, acoustic signals picked up by the microphones can be mixed with echo signals as well as noises, which may result in poor performance of the corresponding communication system. Also, the system performance may decrease further if the reverberation occurs since it is harder to estimate the impulse response of the demixing system. For blind source separation (BSS) in such cases, a time-frequency masking approach can be employed to separate undesired echo signals and noises, but, permutation ambiguities also should be solved for the echo cancellation. In this paper, we propose a new acoustic echo cancellation (AEC) approach utilizing the time-frequency masking and higher-order statistics, whereby a desired signal selection, based on coherence and third-order statistics (i.e., kurtosis), is introduced along with output signal normalization. Simulation results demonstrate that the proposed approach yields better echo and noise cancellation performances than the conventional AEC approaches.

• Proceedings of the KIPE Conference
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• 2017.11a
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• pp.63-64
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• 2017

This paper proposes a speed estimator for sensorless control of diesel-generator (genset) systems, where the speed of the genset is calculated from the back-EMF frequency of the generator. The back-EMF frequency is extracted from a phase output current by using multiple second-order generalized integrators (SOGIs) connected in parallel and series and separated frequency-locked loops. The proposed method (PS-SOGI-FLL) is able to estimate the fundamental frequency in the distorted output current with high accuracy and strong robustness. Simulation results are shown to verify the validity of the proposed method.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.10
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• pp.1844-1851
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• 2007

This paper presents methods for the compensation of sinusoidal disturbances with unknown amplitude, phase, and time-varying frequency in nonlinear systems. In the previous disturbance accommodation methods, the sinusoidal disturbance with unknown time-invariant frequency was considered. In the proposed method, the disturbance with unknown time-varying frequency is compensated. As for the control structure, two control inputs are designed separately in such a way that one of them is designed for the nonlinear system control without considering the disturbance, and the other one uses the disturbance estimate obtained from the disturbance accommodating observer. The stability analysis is done considering the disturbance estimation error and the numerical simulation demonstrates the proposed approach.