• 한국철도학회:학술대회논문집
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• 한국철도학회 1998년도 창립기념 춘계학술대회 논문집
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• pp.287-290
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• 1998

Wheel impact due to the joint discontinuity is a major source of uncomfortable vibration in the railway vehicles. Since the impact signal is measured using sensors attached to the bogie and its energy content is small compared to the other vibrations from the machineries such as motors and gear systems, the seperation of the impact signal is generally difficult. In this study a technique using an evolutionary spectrum is proposed in order to estimate the impact signal due to the rail joint discontinuity.

• Structural Engineering and Mechanics
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• 제17권3_4호
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• pp.409-428
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• 2004

In this paper, a Holder exponent, a measure of the degree to which a signal is differentiable, is presented to detect the presence of a discontinuity and when the discontinuity occurs in a dynamic signal. This discontinuity detection has potential applications to structural health monitoring because discontinuities are often introduced into dynamic response data as a result of certain types of damage. Wavelet transforms are incorporated with the Holder exponent to capture the time varying nature of discontinuities, and a classification procedure is developed to quantify when changes in the Holder exponent are significant. The proposed Holder exponent analysis is applied to various experimental signals to reveal underlying damage causing events from the signals. Signals being analyzed include acceleration response of a mechanical system with a rattling internal part, acceleration signals of a three-story building model with a loosing bolt, and strain records of an in-situ bridge during construction. The experimental results presented in this paper demonstrate that the Holder exponent can be an effective tool for identifying certain types of events that introduce discontinuities into the measured dynamic response data.

• 한국지반공학회논문집
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• 제23권1호
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• pp.51-65
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• 2007

본 논문의 목적은 초음파 탐사 방법을 이용하여 지반내의 불연속 물질을 탐측할 수 있는 고해상도의 시스템을 개발하고 실내에서 적용하는 것이다. 초음파 탐측 방법은 불연속면의 경계면에서 반사되어온 반사파를 탐측하고, 이를 배열하여 불연속면의 존재를 찾는 방법이다. 본 논문은 암반내 초음파의 전달 양상, 최적화된 트랜스듀서의 선택, 데이터 획득, 신호처리 방법, 영상화 기법, 그리고 실내 적용실험을 포함하고 있다. 실내실험은 수평이동장치와 회전이동장치를 이용하여 수행된다. 수중에서 수평이동 및 회전실험 결과, 불연속면의 위치와 크기가 정확하게 평가 되었다. 또한 석고시료에서 회전실험결과 석고 내에 존재하는 균열과 공동이 비교적 정확하게 영상화됨을 알 수 있다. 본 논문은 새롭게 제시된 방법이 암반 불연속면 탐측에 매우 경제적이고 효과적인 방법이 될 수 있음을 보여준다.

• 한국항해학회지
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• 제22권1호
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• pp.15-22
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• 1998

In this paper, discontinuity parts in microstrip line with $\lambda$/4 open stub and one in crank type have been anlayzed by using FDTD(Finite-Difference Time-Domain) analysis method. The noise components, in this case, are occred at the discontinuites of the given microstrip lines, the complex poles were extracted by the analysis using GPOF (Generalized Pencil-of Function) method from electric field of time domain. It has, then, been found that the noise level and the noise frequency components included in signal could be derived.

• 한국통신학회논문지
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• 제32권12C호
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• pp.1149-1155
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• 2007

본 논문에서는 음성신호의 정현파 합성방법 중 하나인 선형위상을 사용한 중첩합산방법에 대하여 합성응성의 연속성을 개선시킨 새로운 방법을 제안한다. 기존의 중첩합산 정현파 합성방법은 프레임의 중간 지점에 대한 위상 값을 예측하기 위해 합성 파형의 경계면에 대한 위상 차이를 최소화하는 방법을 사용하였으나, 제안된 방법은 중간지점의 위상만이 아닌 최종 합성된 신호들 간의 차이를 최소화하는 방법을 사용한다. 이러한 합성신호의 오차 함수를 최소화하는 과정은 정현파 크기 값을 가중치로 사용한 위상오차 함수로 근사화 될 수 있다. 제안된 합성 방법의 연속성에 대한 성능을 검증하기 위해 합성신호의 전 구간에 대한 합성 신호들 간의 평균 오차 값 및 청취자 테스트를 하였다. 기존의 위상 오차함수와 비교하여 개선된 연속성 성능을 얻을 수 있었다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 추계종합학술대회 논문집(1)
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• pp.279-282
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• 2000

As digital systems continue to use components with faster edge rates and clock speeds, transmission of the digital information in these systems approaches the microwave realm. At these speeds digital signal fidelity becomes both a critical success factor and design challenge. The noise sources in digital systems include the noise in power supply, ground and packaging media due to simultaneous switching of drivers, signal reflections and distortions on single and multiple transmission lines. This paper presents theory, case studies and design considerations of gigabit interconnection for network and communication systems. The case studies show HSPICE and Ampredictor simulations of alternate approaches. Various subjects including skin effect and dielectric losses, interconnect simulations and crosstalks of connector, affected signal discontinuity, are addressed.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2008년도 춘계종합학술대회 A
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• pp.425-428
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• 2008

본 논문에서는 위성 항법 시스템(GPS)의 불연속성과 수신 음영 지역에서의 속도 추적 한계를 극복하기 위하여 가속도계와 GPS를 이용한 이동 물체의 속도를 추정하는 시스템을 제안한다. 시스템은 이동 물체에 부착된 GPS 수신기와 가속도계의 항법 정보를 입력받아 물체의 진동과 충격 그리고 가속도계 자체의 오차에 기인한 잡음을 보정하고, 이를 이용하여 GPS 음영 지역에서 이동 물체의 속도 추정과 GPS 항법 정보의 불연속성을 보완할 수 있도록 설계되었다. 본 시스템에 사용하기 위해 GPS와 가속도계를 이용한 칼만 필터 구조를 설계하고, GPS 수신 음영 지역에서도 물체의 속도를 추적할 수 있음을 검증하여, 향후 자동항법장치 등 텔레매틱스 산업에서의 응용 가능성을 제시하고자 한다.

• 대한의용생체공학회:의공학회지
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• 제29권4호
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• pp.278-285
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• 2008

In this study the complex-valued continuous wavelet transform (CWT) has been applied in detection of Electrocardiograms (ECG) as response to various signal classification methods such as Fourier transforms and other tools of time frequency analysis. Experiments have shown that CWT may serve as a detector of non-stationary signal changes as ECG. The tested signal is corrupted by short time events. We applied CWT to detect short-time event and the result image representation of the signal has showed us that one can easily find the discontinuity at the time scale representation. Analysis of ECG signal using complex-valued continuous wavelet transform is the first step to detect possible changes and alternans. In the second step, modulus and phase must be thoroughly examined. Thus, short time events in the ECG signal, and other important characteristic points such as frequency overlapping, wave onsets/offsets extrema and discontinuities even inflection points are found to be detectable. We have proved that the complex-valued CWT can be used as a powerful detector in ECG signal analysis.

• KIEE International Transactions on Power Engineering
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• 제3A권2호
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• pp.85-92
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• 2003

When a current transformer (CT) is saturated, the wave-shape of the secondary current is distorted and contains points of inflection, which correspond to the start or end of each saturation period. Discontinuity in the first-difference function of the current arises at points of inflection, where the second and third differences convert into pulses that can be used to detect saturation. This paper describes the design and evaluation of a CT saturation detection technique using the third-difference function and includes the countermeasure for a spike signal. Test results clearly demonstrate that the algorithm successfully detects the start and end of each saturation period irrespective of the remanent flux and magnetization inductance in the saturated region. This paper concludes by describing the results of hardware implementation of the algorithm using a DSP.

• Journal of information and communication convergence engineering
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• 제6권1호
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• pp.51-54
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• 2008

The defected ground structure (DGS) for microstrip structure can be used to protect analog/RF signal from SSN interference of digital circuits on PCB with common ground. However, the basic DGS gives rise to undesired emissions that may interfere with nearby circuitry due to the ground discontinuity. In this paper, we have proposed the modified structure, Corrugated DGS and the method to reduce the radiation by adding the lumped resistor on the proposed Corrugated DGS.