• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.3
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• pp.383-388
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• 2014

This paper describes a wave modeling method using low-cost sensors. Wave modeling is applied to the wave monitoring system for accurate measurement of ocean wave parameters. The observation of ocean wave parameters is necessary to improve the accuracy of forecast of ocean wave condition. However, the ocean wave parameters measured by a low-cost wave monitoring system suffer from several errors. Therefore we introduce a wave modeling method to compensate the ocean wave parameters corrupted by errors. The proposed method is analyzed using experiments within controlled environment. It is verified that the accuracy of low-cost wave monitoring system can be increased by the proposed method.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.7
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• pp.1012-1016
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• 2009

This paper describes the control and monitoring system for OWEC (Overtopping Wave Energy Converter) which shows the characteristic of power stabilization in overtopping wave energy converter system. Overtopping waves generates different water pressure and the turbine is rotated by this pressure. As a result, overtopping wave energy converter is able to convert wave energy into electricity. Small size of overtopping wave energy converter is developed to simulate the control monitoring system which is able to control power generation and also monitor the system condition. The result shows the reduction of fluctuation from the overtopping wave energy system by the developed control monitoring system. In addition, the DB(Data Base) of test results are contributed to the research and development for OWEC.

• Proceedings of the KSRS Conference
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• 2002.10a
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• pp.337-340
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• 2002

Monitoring of wave height is important primarily to reduce storm risks at sea and along the coast. Wave heights in recent years have increased 50% for the last 40 years, thus requiring intensive monitoring. Satellite altimetry offers a powerful tool for regular and extensive monitoring of the wave height. We extracted significant wave height (SWH) using several altimeter missions from 1987-1995 over the Northwest Pacific and compared with ECMWF reanalysis (ERA) products. For large wave heights > 2.5 m, the ERA wave heights are smaller than the altimetric ones, while for small wave heights the ERA wave heights are larger. Comparison in SWH between altimetric derivations and ERA model products shows the discrepancy of 0.46-0.21$\times$SWH(m).

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.834-837
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• 2005

In this paper, we describe the method of non-invasive blood pressure measurement using pulse wave transit time(PWTT). PWTT is a new parameter involved with a vascular that can indicate the change of BP. PWTT is measured by continuous monitoring of ECG and pulse wave. No additional sensors or modules are required. In many cases, the change of PWTT correlates with the change of BP. We measure pulse wave using the photo plethysmograph(PPG) sensor in an earlobe and we measure ECG using the ECG monitoring device our made in the chest. The measurement device for detecting pulse wave consists of infrared LED for transmitted light illumination, pin photodiode as light detector, amplifier and filter. We composed 0.5Hz high pass, 60Hz notch and 10Hz low pass filter. ECG measurement device consists of multiplexer, amplifier, filter, micro-controller and RF module. After amplification and filtering, ECG signal and pulse wave is fed through micro-controller. We performed the initial work towards the development of ambulatory BP monitoring system using PWTT. An earlobe is suitable place to measure PPG signal without the restraint in daily work. From the results, we can know that the dependence of PWTT on BP is almost linear and it is possible to monitoring an individual BP continuously after the individual calibration.

• The Journal of the Korea institute of electronic communication sciences
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• v.6 no.2
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• pp.268-273
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• 2011

Withstanding the continuous treat from the typhoon and nasty weather from ocean, the development of the real time monitoring buoy such as ocean wave related monitoring buoy system becomes essential. In this research, the development of the ocean wave monitoring buoy system had been done domestically. The development including the data real-time monitoring (wind, temperature and pressure) added in the buoy, buoy mooring and real-time data communication system. The developed wave monitoring buoy system (drift type, wave direction and wave height type) is expected to meet the demands.

• Journal of information and communication convergence engineering
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• v.5 no.1
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• pp.7-11
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• 2007

The aim of this paper is to design and implement a new ECG signal monitoring and analysis method for the home care of elderly persons or patients, using wireless sensor network (WSN) technology. The wireless technology for home-care purpose gives new possibilities for monitoring of vital parameter with wearable biomedical sensors and will give the patient freedom to be mobile and still be under continuously monitoring. Developed platform for portable real-time analysis of ECG signals can be used as an advanced diagnosis and alarming system. The ECG features are used to detect life-threatening arrhythmias, with an emphasis on the software for analyzing the P-wave, QRS complex, and T-wave in ECG signals at server after receiving data from base station. Based on abnormal ECG activity, the server transfer diagnostic results and alarm conditions to a doctor's PDA. Doctor can diagnose the patients who have survived from arrhythmia diseases.

• Smart Structures and Systems
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• v.11 no.2
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• pp.185-197
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• 2013

We developed a simultaneous strain measurement and damage detection technique using a pair of surface-mounted piezoelectric transducers and a fiber connecting them. This is a novel sensor configuration of the fiber acoustic wave (FAW) piezoelectric transducer. In this study, lead-zirconate-titanate (PZT) transducers are installed conventionally on a plate's surface, which is a technique used in many structural health monitoring studies. However, our PZTs are also connected with an optical fiber. A FAW and Lamb wave are simultaneously guided in the optical fiber and the structure, respectively. The dependency of the time-of-flight of the FAW on the applied strain is quantified for strain sensing. In our experimental results, the FAW exhibited excellent linear behavior and no hysteresis with respect to the change in strain. On the other hand, the well-known damage detection function of the surface-mounted PZT transducers was still available by monitoring the waveform change in the conventional Lamb wave ultrasonic path.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.2066-2072
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• 2008

The time reversal was investigated for direct root between PZT and PZT, but in case of a circular PZT, lamb wave moves not only along the direct root but also another roots. The center frequency of lamb wave is kept when the lamb waves are reflected from damage. This paper presents experimental and theoretical results for the new structural health monitoring method by above features of lamb wave, and we can increase accuracy of the new structural health monitoring method by using STFT(Short Time Fourier Transform).

• Laser Solutions
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• v.6 no.2
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• pp.27-33
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• 2003

A laser shock cleaning technology is a new dry cleaning methodology for the effective removal of small particles from the surface. This technique uses a plasma shock wave produced by a breakdown of air due to an intense laser pulse. In order to optimize the laser shock cleaning process, it needs to evaluate the cleaning performance quantitatively by using a monitoring technique. In this paper, an acoustic monitoring technique was attempted to investigate the laser shock cleaning process with an aim to optimize the cleaning process. A wide-band microphone with high sensitivity was utilized to detect acoustic signals during the cleaning process. It was found that the intensity of the shock wave was strongly dependent on the power density of laser beam and the gas species at the laser beam focus. As a power density was larger, the shock wave became stronger. It was also seen that the shock wave became stronger in the case of Ar gas compared with air and N$_2$ gas.

• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.3
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• pp.241-262
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• 2012

Some applications require structural health monitoring in inaccessible components. This paper presents a technique useful for Structural Health Monitoring of double wall structures, such as double wall steam pipes and double wall pressure vessels separated from an ultrasonic transducer by three layers. Detection has been demonstrated at distances in excess of one meter for a fixed transducer. The case presented here is for one of the layers, the middle layer, being a fluid. For certain transducer configurations the wave propagating in the fluid is a wave with low velocity and attenuation. The paper presents a model based on wave theory and finite element simulation; the experimental set-up and observations, and comparison between theory and experiment. The results provide a description of the technique, understanding of the phenomenon and its possible applications in Structural Health Monitoring.