• Communications for Statistical Applications and Methods
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• 제29권2호
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• pp.225-238
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• 2022

In this paper, we propose a clustering method for advanced metering infrastructure (AMI) data in Korea. As AMI data presents non-stationarity, we consider time-dependent frequency domain principal components analysis, which is a proper method for locally stationary time series data. We develop a new clustering method based on time-varying eigenvectors, and our method provides a meaningful result that is different from the clustering results obtained by employing conventional methods, such as K-means and K-centres functional clustering. Simulation study demonstrates the superiority of the proposed approach. We further apply the clustering results to the evaluation of the electricity price system in South Korea, and validate the reform of the progressive electricity tariff system.

• 대한기계학회논문집
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• 제9권5호
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• pp.539-547
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• 1985

본 논문에서는 이상과 같은 연구현상을 배경으로 응력비 R.geq.0인 사인응력파 에서도 사이클의존형 크랙전파가 공존하는가, 공존한다면 그 전이를 결정짓는 조건을 구하기 위해, 대표적인 고온용 재료인 SUS 304강을 이용하여 온도 650.deg. C, 대기중에서 반복속도 .nu., 응력비 R, 응력레벨 .sigma.$_{maxo}$등의 실험조건을 바꾸어 고온저사이클 피로실험을 하였다. 또 이 현상의 기초과정을 이해하는데 도움을 주기 위하여 파면 관찰을 행하였다.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2005년도 High Temperature Superconductivity Vol.XV
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• pp.37-37
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• 2005

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2005년도 춘계학술대회논문집
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• pp.303-306
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• 2005

This paper presents the frequency-dependent characteristics of leakage currents flowing through ZnO surge arrester block. The leakage current-voltage (I-V) characteristic curves of the commercial ZnO surge arrester blocks were measured. The resistive leakage current was found to increase with increasing frequency in the low conduction region. The capacitance of ZnO block was independent of the magnitude and frequency of the applied voltage. The power losses of ZnO block increase as the frequency of applied voltage increases, because of the dielectric loss related to the frequency of the test voltage.

• 대한의용생체공학회:의공학회지
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• 제4권1호
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• pp.29-36
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• 1983

In this paper, center frequency down slift of ultrasonic echo signals which for the measurements of frequency dependent attenuation in the biological tissue are estimated. Center frequency down shift of echo-signals are estimated after signal spectrum analysis of whole echo-signals. In case of signal spectrums are simple, estimation of down shift frequency is very simple and in case of complicate spectrum, estimation of down shift frequency is depend on spectral shape. In case of unable to estimate, frequency dependence of medium is nonlinear(n) 1), in which upper shift of spectrums are presented. In case of unable to estimate, spectrum analysis are performed at local position. At consquence, we know that spectral dispersions are caused complicately by biological tissue layer.

• Journal of information and communication convergence engineering
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• 제7권1호
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• pp.62-65
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• 2009

In this paper, the temperature characteristics of full CMOS FLL(frequency locked loop) re analyzed. The FLL circuit is used to generate an output signal that tracks an input efference signal. The locking time of FLL is short compared to PLL(phase locked loop) circuit because the output signal of FLL is synchronized only in frequency. Also the FLL s designed to allow the circuit to be fully integrated. The FLL circuit is composed two VCs, two buffers, a VCO and two frequency dividers. The temperature variation of frequency divider, FVC and buffer cancelled because the circuit structure. is the same and he temperature effect is cancelled by the comparator. Simulation results are shown to illustrate the performance of the designed FLL circuit with temperature.

• KIEE International Transactions on Electrophysics and Applications
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• 제2C권5호
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• pp.273-278
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• 2002

Even though the modulating signal frequency of the light is too high to detect directly, the signal can be extracted by frequency conversion at the same time as the detection by means of the non-linearity of the APD. An analysis is presented for super-high-speed optical demodulation by an APD with electronic mixing. A normalized gain is defined to evaluate the performance of the frequency conversion demodulation. The nonlinear effect of the internal capacitance was included in the small signal circuit analysis. We showed theoretically and experimentally that the normalized gain is dependent on the down converted difference frequency component. In the experiment, the down converted different frequency outputs became larger than the directly detected original signal for the applied local signal of 20㏈m.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집B
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• pp.609-614
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• 2000

This numerical study investigate resonance frequency of natural convection for steady state, periodic flow and chaotic flow in two-dimensional direct numerical simulations, differentially heated, vertical cavities having aspect ratios near unity. The enclosure cavity has isothermal and time dependent temperature side walls and adiabatic top/bottom walls. The aspect ratio is 1/3, 1/2, 1, 2, and 3 for the varying Rayleigh number. Resonance frequency for AR=1 has decrease as the aspect ratio and the Rayleigh number are increasing.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2008년도 춘계학술대회 논문집
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• pp.57-60
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• 2008

A design criterion of grounding systems is commonly based on low frequency resistance in Korea. When lightning surges which have high frequency components are injected into the grounding system, the grounding impedance is greatly different from the static grounding resistance. This paper presents the grounding adimittance and phase on the frequency range from 100 [Hz] to 15 [MHz] using water tank simulating the grounding system in different water resistivities. As a result, capacitive effect is dominant over the frequency of 100 [kHz] at the water resistivity of 1,000 [$\Omega$ m]. On the other hand, the inductive characteristics appear at the low water resistivity. Consequently, dependence of grounding impedances on the frequency of injected current is strongly related to resistivity.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 춘계 학술발표회
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• pp.146-153
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• 2009

One dimensional site response analysis is widely used in prediction of the ground motion that is induced by earthquake. Equivalent linear analysis is the most widely used method due to its simplicity and ease of use. However, the equivalent linear method has been known to be unreliable since it approximates the nonlinear soil behavior within the linear framework. To consider the nonlinearity of the ground at frequency domain, frequency dependent algorithms that can simulate shear strain - frequency dependency have been proposed. In this study, the results of the modified equivalent linear analysis are compared to evaluate the degree of improvement and the applicability of the modified algorithms. Results show the novel smoothed curve that is proposed by this study indicates the most stable prediction and can enhance the accuracy of the prediction.