• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.10a
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• pp.607-610
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• 2009

The abnormal combustion in the running engine results to knocking which increases the pressure and temperature in the cylinder, thereby decreasing the generated power by reducing the thermal efficiency. When the temperature and pressure in the cylinder increased rapidly by knocking, abnormal combustion takes place and the engine power is decreased. To investigate the knocking phenomenon, accelerometers are installed in the cylinder head to monitor and diagnose the vibration signal. As method of signal analysis, the time-frequency analysis method was adapted for acquisition of vibration signal and analyzes engine combustion in the short time. In this experiment, after analyzing time data which is stored in the signal recorder in one unit work (4 strokes: 2 revolutions), the signal with frequency and Wavelet methods with extracted one engine combustion data was also analyzed. Then, normal condition with no knocking signal is analyzed at this time. Hereafter, the experiments made a standard for distinguishing normal and abnormal condition to be carried out in acquisition of vibration signal at all cylinders and extracting knocking signal. In addition, analyzing methods can be diverse with Symmetry Dot Patterns (SDP), Time Synchronous Average (TSA), Wigner-Ville Distribution (WVD), Wigner-Ville Spectrum (WVS) and Mean Instantaneous Power (MIP) in the cold test [2]. With signal processing of vibration from engine knocking sensor, the authors adapted a part of engine /rotor vibration analysis and monitoring system for marine vessels to prevent several problems due to engine knocking

• Journal of Sensor Science and Technology
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• v.20 no.5
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• pp.343-350
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• 2011

The compliance and stiffness of artery are closely related with disease of arteries. Pulse wave velocity(PWV) in the blood vessel is a basic and common parameter in the hemodynamics of blood pressure and blood flow wave traveling in arteries because the PWV is affected directly by the conditions of blood vessels. However, there is no standardized method to measure the PWV and it is difficult to measure. The conventional PWV measurement has being done by manual calculation of the pulse wave transmission time between coronary arterial proximal and distal points on a strip chart on which the pulse wave and ECG signal are recorded. In this study, a pressure sensor consisting of strain gauges is used to measure the blood pressure of arteries in invasive method and regular ECG electrodes are used to record the ECG signal. The R-peak point of ECG is extracted by using a reference level and time windowing technique and the ascending starting point of blood pressure is determined by using differentiation of the blood pressure signal and time windowing technique. The algorithm proposed in this study, which can measure PWV automatically, shows robust and good results in the extraction of feature points and calculation of PWV.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.3 no.1
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• pp.3-7
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• 2010

In this study, we developed a circuit device detecting korotkoff sounds of forearm electronic blood pressure monitor by digital signal. In order to test a circuit detecting signal from korotkoff sounds, systolic and diastolic pressure were compared our developed circuit device with the existing forearm electronic blood pressure monitor (Model: SE-7000, Korea). Devices for an experiment composed of a forearm cuff, a stethoscope, an amplifier, a PC with A/D board, etc. Results of korotkoff sounds was similar to a pattern of oscilometric signals from the existing forearm electronic blood pressure monitor. We thought it is possible to measure blood pressures, if blood pressures were detected precisely using signals of korotkoff sounds.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.234-234
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• 2011

Electron-neutral collision frequency is one of the important parameters in the plasma physics and in industrial plasma engineering. We can understand the momentum, energy, and charge transport properties of the plasma using electron-neutral collision frequency.[1] The wave-cutoff method is a diagnostic method for the electron density measurement, but the cutoff peak value depends on gas pressure. The wave-cutoff signal becomes unclear as increasing gas pressure. The reason of pressure dependence is that the electron-neutral collision disturbs electron motion so that microwave can propagate through plasma at plasma frequency.[2] Using the pressure dependence of wave-cutoff method we can find the electron-neutral collision frequency. At first we tried to confirm this method using well known gas such as Ar. The cutoff signal decrease as increasing gas pressure (the simulation result). The wave-cutoff signal is unclear at a gas pressure of 500 mTorr. (electron density $1.0{\times}10^{10}/cm^3$, electron temperature 1.7 eV, electron -neutral collision frequency~1 GHz). In this condition, the electron-neutral collision frequency is closed to the wave-cutoff frequency.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.10 s.241
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• pp.1119-1129
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• 2005

A new measurement system of wall pressure fluctuations on a rotating machinery, composed of digital recording device, was developed and evaluated. The small-sized digital recording device was attached on the rotating machinery and then was detached for data reduction. In order to obtain the system transfer function of the digital recording system, a dynamic calibration was performed utilizing the signal from a 1/8 inch B&K microphone as input. The time history of the unsteady pressure was then reconstructed from the output of the sensor by using this transfer function. The reconstructed pressure signals showed good agreement with the reference signal in both temporal and spectral sense. This sensor was then used to measure the wall pressure fluctuations on a rotating blade. An array of microphones were installed on the blade in the circumferential and radial directions. Various statistical moments were obtained from the measurement data set. Comparison of these quantities with the existing studies demonstrated satisfactory agreement. These tests give credence to the relevance and reliability of this device for applications in more complicated turbulent rotating machineries.

• Journal of Biomedical Engineering Research
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• v.28 no.4
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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.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.5 s.170
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• pp.181-188
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• 2005

The purpose of this study is to develop the new cuff improving the accuracy of blood pressure measurement, and to evaluate the performance of the developed system. We added a small bladder to the normal cuff which is called the double bladder system. The developed system for blood pressure measurement was based on the oscillometric method using a double bladder. This system was developed in order to reduce the oscillation noise and to amplify the signal of pure blood pressure An oscillometric signal database based on the developed system were evaluated following the standard ANSI/AAMI/SP10-1992. The correlation coefficients between cuff of double bladder and normal cuff were 0.98 for systolic and 0.94 for diastolic. Mean differences and the standard deviations between average blood pressure of mercury sphygmomanometer and automated sphygmomanometer were -0.7mmHg and 4.9mmHg for systolic, and -1.4mmHg and 5.4mmHg for diatolic, respectively. We conclude that the proposed double bladder based cuff system improves the accuracy of the oscillometric blood pressure measurement. The developed system reduces the error range about $44\~62\%$ for systolic and about $6\~21\%$ for diastolic compared to the recently developed commercially available sphygmomanometers.

• Journal of Biomedical Engineering Research
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• v.24 no.4
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• pp.281-286
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• 2003

Blood Pressure is one of the most fundamental Parameters which reflects physical conditions medically and the blood pressure measurement system using oscillometric method is a Non-Invasive Blood Pressure measurement device by measuring arterial Pressure through a cuff. In this paper. we designed a inflatable wrist blood pressure system which measures blood Pressure during the stepping inflation in the wrist cuff. The hardware system consists of a main power unit, a bladder in cuff unit, signal detection units, signal Processing units. a wireless data transmission unit, and a data display unit. We evaluated the reliability of this system by comparing and analyzing systolic. diastolic blood Pressure, and heart rate with other commercial blood Pressure measurement devices. Characteristic ratio values used to determine systolic and diastolic blood Pressure using MAA(Maximum Amplitude Algorithm) were 0.436 and 0.671 respectively.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 1996.09a
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• pp.117-124
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• 1996

When navigating in or near an area of restricted visibility it is necessary to be heard the whistle bell and/or the siren of lighthouses or ships at times. Even though we can get the brief informations about the property of sound the direction and range of a sound radiator it is not easy to get the accurate informations for decision making. generally the audio frequency is known as 16-20,000Hz but the earshot is shorten and discrimination of sound is more difficult when there is some noise. The sound pressure is 60dB at the moment when human speaks 1 meter away. Usually the noise pressure in a silent room is 40dB and 60dB on the quiet street. In this study we suggest the basic algorithm to trace the direction and range of the source radiator using the signal received through not a physical sense but the microphone sensors and a series of signal of signal processing.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.4 s.247
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• pp.364-372
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• 2006

In this paper, we present a finger tip tactile sensor which can detect contact normal force as well as slip. The sensor is made up of two different materials, such as polyvinylidene fluoride (PVDF) known as piezoelectric polymer, and pressure variable resistor ink. In order to detect slip on the surface of the object, two PVDF strips are arranged along the normal direction in the robot finger tip and the thumb tip. The surface electrode of the PVDF strip is fabricated using silk-screening technique with silver paste. Also a thin flexible force sensor is fabricated in the form of a matrix using pressure variable resistor ink in order to sense the static force. The developed tactile sensor is physically flexible and it can be deformed three-dimensionally to any shape so that it can be placed on anywhere on the curved surface. In addition, a tactile sensing system is developed, which includes miniaturized charge amplifier to amplify the small signal from the sensor, and the fast signal processing unit. The sensor system is evaluated experimentally and its effectiveness is validated.