• 융합신호처리학회논문지
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• 제23권2호
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• pp.62-69
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• 2022

의료현장에서는 최근 디지털 헬스케어의 중요성이 대두되면서, 다양한 형태의 생체신호 측정 관련 연구가 활발히 진행되고 있다. 생체신호 중 가장 중요한 신호로 심전도를 들 수 있으며, 특히 부정맥 환자에 있어 심전도 신호의 연속 모니터링은 매우 중요하다. 부정맥은 동결절(sinus node), 동빈맥(sinus tachycardia), 심방조기수축(atrial premature beat, APB), 심실세동 (ventricular fibrillation) 등으로 그 발병원에 따른 형태가 다양하며, 발병 이후의 예후가 좋지 않으므로 일상 중 연속 모니터링은 부정맥의 조기 진단과 치료방향 설정에서 매우 중요하다. 부정맥 환자의 심전도 신호는 매우 불안정하며, 부정맥을 자동 검출하기 위한 주요 특징점으로 작용하는 정확한 R-peak 포인트의 검출이 어렵다. 본 연구에서는 연속 측정하는 홀터 심전도 모니터링 기기와 분석용 소프트웨어를 개발하였으며, 부정맥 데이터베이스를 통해 심전도 신호의 R-peak 효용성을 확인하였다. 향후 연구에서는 다양한 발병원인으로 인한 부정맥의 형태적 구분 및 예측을 위한 알고리즘과 임상 데이터에 근거한 유효성 검증에 관한 추가 연구가 필요하다.

• Smart Structures and Systems
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• 제11권5호
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• pp.477-496
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• 2013

Due to their cost-effectiveness and ease of installation, wireless smart sensors (WSS) have received considerable recent attention for structural health monitoring of civil infrastructure. Though various wireless smart sensor networks (WSSN) have been successfully implemented for full-scale structural health monitoring (SHM) applications, monitoring of low-level ambient strain still remains a challenging problem for WSS due to A/D converter (ADC) resolution, inherent circuit noise, and the need for automatic operation. In this paper, the design and validation of high-precision strain sensor board for the Imote2 WSS platform and its application to SHM of a cable-stayed bridge are presented. By accurate and automated balancing of the Wheatstone bridge, signal amplification of up to 2507-times can be obtained, while keeping signal mean close to the center of the ADC span, which allows utilization of the full span of the ADC. For better applicability to SHM for real-world structures, temperature compensation and shunt calibration are also implemented. Moreover, the sensor board has been designed to accommodate a friction-type magnet strain sensor, in addition to traditional foil-type strain gages, facilitating fast and easy deployment. The wireless strain sensor board performance is verified through both laboratory-scale tests and deployment on a full-scale cable-stayed bridge.

• 대한교통학회지
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• 제20권2호
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• pp.135-148
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• 2002

본 연구는 공간적 정보를 수집할 수 있는 영상검지기를 이용하여 대기길이를 산출하는 알고리즘을 개발하였다. 이 알고리즘은 접근로 상·하류부에 각각 영상검지기를 설치하여 대기길이를 측정하는 방법을 사용한다. 또한 산출된 대기길이를 기반으로 새로운 신호제어모형을 제시하였다. 특히, 대기길이 기반의 주기길이와 녹색시간을 산출하는 절차와 알고리즘을 제시하였다. 제시한 알고리즘에 대한 검증을 위해 네트워크 환경을 구축하여 시뮬레이션을 수행하였다. 그 결과, 제안 모형이 기존모형보다 운영효과가 높게 나타났다. 추가적인 연구로는 실시간 교통조건에 병행하여 본 알고리즘을 검증할 필요성이 있다.

• 한국압력기기공학회 논문집
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• 제10권1호
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• pp.75-81
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• 2014

A simulation of eddy current testing has been utilized for predicting the signal characteristics to the various defects and developing the probes. Especially, CIVA which is a simulation tool dedicated to nondestructive testing has a good accuracy and speed, and provides a three-dimensional graphical user interface for improved visualization and familiar data displays consistent with NDE technique. Although internal validations have been performed by the CIVA software development specialists, an independent validation study is necessary for the accuracy assessment of the software prior to practical use. For this purpose, in this study, eddy current testing signals of ASME FBH calibration standard tube for bobbin probe were simulated using CIVA and the results were compared to the experimental inspected signals based on the relationship between each flaw signal in terms of amplitude and phase, and the shape of the Lissajous curve. And then we verified the accuracy of the simulated signals and the possible range for simulation. Overall, there is a good qualitative agreement between the CIVA simulated and experimental results in the absolute and differential modes at the two inspection frequencies.

• Smart Structures and Systems
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• 제4권3호
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• pp.305-318
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• 2008

The development of a digital signal processor based prototype is described in relation to continuing efforts for realizing a fully self-contained active sensor system utilizing impedance-based structural health monitoring. The impedance method utilizes a piezoelectric material bonded to the structure under observation to act as both an actuator and sensor. By monitoring the electrical impedance of the piezoelectric material, insights into the health of the structured can be inferred. The active sensing system detailed in this paper interrogates a structure utilizing a self-sensing actuator and a low cost impedance method. Here, all the data processing, storage, and analysis is performed at the sensor location. A wireless transmitter is used to communicate the current status of the structure. With this new low cost, field deployable impedance analyzer, reliance on traditional expensive, bulky, and power consuming impedance analyzers is no longer necessary. A complete power analysis of the prototype is performed to determine the validity of power harvesting being utilized for self-containment of the hardware. Experimental validation of the prototype on a representative structure is also performed and compared to traditional methods of damage detection.

• 대한의용생체공학회:의공학회지
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• 제28권4호
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• pp.577-584
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• 2007

Uroflowmetry is non-invasive and easily performed to diagnose benign prostatic hypertrophy(BPH) frequent in aged men. Weight change during urination is usually measured to estimate the urinary flow rate by a load cell, but sensitive to any impacts against the bottom of the container, leading to unnecessary noise generation. Moreover, load cells are relatively expensive raising the production cost. The present study proposed a new technique, measuring hydraulic pressure on the bottom of the urine container to evaluate the urinary volume. Low cost pressure transducer enabled almost perfectly linear relationship between the urine volume and the hydraulic pressure. During both the simulated and human urination experiments, variance of the pressure signal was more than 50% smaller than the weight signal acquired by a load cell, which demonstrated that the impact noise was decreased to a great degree by pressure compared to weight measurement.

• ETRI Journal
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• 제42권3호
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• pp.324-332
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• 2020

In this paper, a blind symbol timing offset (STO) estimation method is proposed for offset quadrature phase-shift keying (OQPSK) modulated signals, which also works for other linearly modulated signals (LMS) such as binary-PSK, QPSK, 𝜋/4-QPSK, and minimum-shift keying. There are various methods available for blind STO estimation of LMS; however, none work in the case of OQPSK modulated signals. The popular cyclic correlation method fails to estimate STO for OQPSK signals, as the offset present between the in-phase (I) and quadrature (Q) components causes the cyclic peak to disappear at the symbol rate frequency. In the proposed method, a set of close and approximate offsets is used to compensate the offset between the I and Q components of the received OQPSK signal. The STO in the time domain is represented as a phase in the cyclic frequency domain. The STO is therefore calculated by obtaining the phase of the cyclic peak at the symbol rate frequency. The method is validated through extensive theoretical study, simulation, and testbed implementation. The proposed estimation method exhibits robust performance in the presence of unknown carrier phase offset and frequency offset.

• 동력기계공학회지
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• 제17권2호
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• pp.56-62
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• 2013

A technique is presented that uses a circular waveguide for the measurement of the bulk shear (S-wave) velocities of unconsolidated, saturated media, with particular application to near surface soils. The technique requires the measurement of the attenuation characteristics of the fundamental torsional mode that propagate along an embedded pipe, from which the acoustic properties of the surrounding medium are inferred. From the dispersion curve analysis, the feasibility of using fundamental torsional mode which is non-dispersive and have constant attenuation over all frequency range is discussed. The principles behind the technique are discussed and the results of an experimental laboratory validation are presented. The experimental data are best fitted for the different depths of wetted sand and the shear velocities are evaluated as a function of depths. Also the characteristics of the reflected signal from the defects are examined and the reflection coefficients are calculated for identifying the relation between defect sizes and the magnitude of the reflected signal.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 C
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• pp.1195-1199
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• 1998

In this paper a design method of robust power system stabilizers is proposed by means of robust linear quadratic regulator design technique under power system's operating condition change, which is caused by inner structure uncertainties and disturbances into a power system. It is assumed that the uncertainties present in the system are modeled as one equivalent signal. In this connections an optimal LQR control input for disturbance rejection, the output feedback gain for eliminating the disturbance are calculated. In this case. PSS input signal is obtained on the basis of weighted ${\Delta}P_e$ and $\Delta\omega$. In order to stabilize the overall control of system. Pole placement algorithm is applied in addition. making the poles of the closed loop system to move into a stable region in the complex plane. Some simulations have been conducted to verify the feasibility of the proposed control method on a machine to infinite bus power system. From the simulation results validation of the proposed method could be achieved by comparisons with the conventional PSS with phase lag-lead compensation.

• 한국음향학회지
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• 제22권5호
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• pp.345-350
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• 2003

음향 인텐시티는 근접한 두 개의 마이크로폰으로부터 얻어지는 음압의 크로스스펙트럼으로부터 얻어진다. 크로스스펙트럼은 이산 푸리에 변환에 의해 얻어지는데 이는 기록시간과 신호의 주기가 일반적으로 일치하지 않기 때문에 누설오차의 발생을 피할 수 없다. 그러므로 기존의 FFT 해석기로부터 얻어지는 음향 인텐시티는 왜곡된 값을 보여준다. 본 논문에서는 단일주파수를 가지는 조화 신호에 누설오차가 발생한 경우 푸리에 변환된 데이터를 규정한다. 또한 왜곡된 데이터로부터 누설오차의 영향을 제거하는 방법을 제안한다. 제안한 방법의 타당성을 보이기 위해 몇 가지 수치해석 예를 보인다.