• 한국기계연구소 소보
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• s.19
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• pp.61-68
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• 1989

As the system monitoring technology become required in order to improve the system performance and the productivity, we’ve studied to the detection for the tool wear and the tool breakage using AE sensors that is able to detection of generated high frequency stress pulse at cutting. The detection system is consist of a sensing part, a amplifier part, a signal processing part, and a analysis & output part. The moment (a rms and a kurtosis) of statistical method is used for analysis of AE singnal. The experiment are carried out in a CNC lathe. In this study, we achieved that the amplitude level of the AE signal and statistical moments was largely changed as the tool failure. The change rate of Kurtosis was especially large, but the change rate of the rms was small.

• KIPS Transactions on Computer and Communication Systems
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• v.5 no.6
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• pp.135-142
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• 2016

We proposed the new method to estimate the blood pressure with the differential value of the digital arterial pulse waveform and BP relation equation. To get the digital arterial pulse waveform, we use the arterial pulse waveform measurement system that has digital air-pressure sensor device and smart phone. The acquired digital arterial pulse waveforms are classified as hypertension group, normal group, and hypotension group, and we can derive the average differential value between the highest point and lowest point of a single waveform of individuals along with the group. In this study, we found the functional correlation between the blood pressure and differential value as a form of BP relation equation through the regression process on the average of differential value and blood pressure value from a tonometer. The Experimental results show the BP relation equation can give easy blood pressure estimation method with a high accuracy. Although this estimation method has over 66 % error rate and does not give the high level of the accuracy for the diastolic compares to the commercial tonometer, the estimation results for the systolic show the high accuracy that has less than 10 % error rate.

• Proceedings of the KIEE Conference
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• 2007.04a
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• pp.377-379
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• 2007

To reduce the chattering errors of reed switch sensors used for automatic remote measurement of water supply system, a reed switch sensor was analyzed and improved. The operation of reed switch sensors can be described as a mechanical contact by approximation of permanent magnet piece to generate an electrical pulse. The reed switch sensors are used in measurement application by detecting the rotational or translational displacement. To apply for flow measurement devices, the reed switch sensors should keep high reliability. They are applied for the electronic digital type of water flow meters. The reed switch sensor is just installed simply on the mechanical type flow meter. A small magnet is attached on a pointer of the water meter counter rotor. Inside the reed sensor, two steel leaf springs make mechanical contact and apart as rotation of flow meter counter. The counting electrical contact pulses can be converted as the water flow amount. The MCU sends the digital flow rate data to the server using the wireless communication network. But it occurs data difference or errors by chattering noise. The reed switch sensor contains chattering error by it self at the force equivalent position. The vibrations such as passing car near to the switch sensor installed location. In order to reduce chattering error, most system uses just software methods for example using filter and also statistical calibration methods. The chattering errors were reduced by changing leaf spring structure using mechanical hysteresis characteristics.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.12
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• pp.807-818
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• 2020

In this study, hydrophones using acoustic sensors were used to estimate the amount of bedload discharge in a forested watershed. The reaction characteristics were analyzed through hydrophone flume tests and field tests, and the quantitative bedload discharge was calculated and compared with that measured by a pit sampler. The hydrophone reaction changed the pulse according to the flow rate change, but did not react to standard sand. The pulse was different depending on the particle size and weight, and accordingly, there was a specific channel showing a suitable response. For a hydrophone installed in the field, by using an automatic impact device, the reaction characteristics of each channel were analyzed to confirm normal operation of the sensor and the suitability of the output value of each channel. In addition, a suitable channel was selected for the estimation of bedload discharge. The bedload discharge formula was developed using a hydrophone pulse and the average flow rate, and was compared with the measured data in the pit sampler in the study site. As a result of the study, if a hydrophone is used for monitoring the bedload in forested watersheds, it is considered effective in quantitatively estimating the weight of bedload discharge.

• Journal of Sensor Science and Technology
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• v.17 no.6
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• pp.447-453
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• 2008

Respiration rate is one of the important vital signs. Photo-plethysmography (PPG) measurement especially on a finger has been widely used in pulse oximetry and also used in estimating respiration rate. It is well known that PPG contains respiration-induced intensity variation (RIIV) signal. However, the accuracy of finger PPG method has been controversial. We introduced a new technique of enhancing motion artifact by respiration. This was achieved simply by measuring PPG on the thorax. We examined the accuracy of these two PPG methods by comparing with two existing methods based on thoracic volume and nostril temperature changes. PPG sensing on finger tip, which is the most common site of measurement, produced 6.1 % error. On the other hand, our method of PPG sensing on the thorax achieved 0.4 % error which was a significant improvement. Finger PPG is sensitive to motion artifact and it is difficult to recover fully small respiratory signal buried in waveform dominated by absorption due to blood volume changes. Thorax PPG is poor to represent blood volumes changes since it contains substantial motion artifact due to respiration. Ironically, this inferior quality ensures higher accuracy in terms of respiration measurement. Extreme low-cost and small-sized LED/silicon detector and non-constrained reflection measurement provide a great candidate for respiration estimation in ubiquitous or personal health monitoring.

• Journal of Astronomy and Space Sciences
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• v.26 no.1
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• pp.47-58
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• 2009

In this study, a Hardware-In-the-Loop (HIL) simulator using thrusters is developed to validate the spacecraft attitude system. To control the attitude of the simulator, eight cold gas thrusters are aligned with roll, pitch and yaw axis. Also linear actuators are applied to the HIL simulator for automatic mass balancing to compensate the center of mass offset from the center of rotation. The HIL simulator consists of an embedded computer (Onboard PC) for simulator system control, a wireless adapter for wireless network, a rate gyro sensor to measure 3-axis attitude of the simulator, an inclinometer to measure horizontal attitude, and a battery set to supply power for the simulator independently. For the performance test of the HIL simulator, a bang-bang controller and Pulse-Width Pulse-Frequency (PWPF) modulator are evaluated successfully. The maneuver of 68 deg. in yaw axis is tested for the comparison of the both controllers. The settling time of the bang -bang controller is faster than that of the PWPF modulator by six seconds in the experiment. The required fuel of the PWPF modulator is used as much as 51% of bang-bang controller in the experiment. Overall, the HIL simulator is appropriately developed to validate the control algorithms using thrusters.

• Journal of the Institute of Convergence Signal Processing
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• v.19 no.1
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• pp.14-19
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• 2018

Recently, the smart health care industry has been rising rapidly and interest and efforts for public health have been greatly increased. As a result, the public does not visit medical specialists and medical facilities, but the desire to check their health condition in everyday life is increased. Therefore, many domestic and foreign companies continuously research and develop wearable devices that can measure body activity information anytime and anywhere And the market. Especially, it is used for heart activity measurement device using pulse wave sensor and electrocardiogram sensor. However, in this study, a monitoring system that can detect cardiac activity using cardiac sounds, heart sound measurement rather than pulse wave measurement and electrocardiogram measurement, was performed and its performance was evaluated. Experimental results confirmed the predictability of cardiac heart rate and heart valve disease during daily living.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.10a
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• pp.67-71
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• 2007

Recently, a health care need according to the increase of an advanced age population is increasing. The requirement about a health care monitoring is increasing rapidly from general people as well as patient. The requisition about a medical treatment technique and a medical treatment information service is the trend to be expanding. That can be possible minimizing the inconvenience of the patient to take a medical service and continuously monitoring the status of the patient to take a health care service. This paper discusses an implementation of wireless physiological signal monitoring system for health care. The system are composed of the sensor node and monitoring program. The sensor node has the physiological signal measurement part and the wireless communication part. The remote monitoring system has a monitoring program that are communicating the sensor node using bluetooth. The sensor node measured the ECG, pulse wave, blood pressure, Sp02, and heart rate.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.8
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• pp.1401-1407
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• 2008

Recently, a health care need according to the increase of an advanced age population is increasing. The requirement about a health care monitoring is increasing rapidly from general people as well as patient. The requisition about a medical treatment technique and a medical treatment information service is the trend to be expanding. That can be possible minimizing the inconvenience of the patient to take a medical service and continuously monitoring the status of the patient to take a health care service. This paper discusses an implementation of wireless physiological signal monitoring system for health care. The system are composed of the sensor node and monitoring program. The sensor node has the physiological signal measurement part and the wireless communication part. The remote monitoring system has a monitoring program that are communicating the sensor node using bluetooth. The sensor node measured the ECG, pulse wave, blood pressure, SpO2, and heart rate.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.5
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• pp.1303-1310
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• 2010

Recently, researches related with automative mechanism have been widely studied to increase the driver's safety by continuously monitoring the driver's health condition to prevent driver's drowsiness. This paper describes the design of wearable chest belt for ECG and reflectance pulse oximetry for SpO2 sensors based on wireless sensor network to monitor the driver's healthcare status. ECG, SpO2 and heart rate signals can be transmitted via wireless sensor node to base station connected to the server. Intelligent monitoring system is designed at the server to analyze the SpO2 and ECG signals. HRV (Heart Rate Variability) signals can be obtained by processing the ECG and PPG signals. HRV signals are further analyzed based on time and frequency domain to determine the driver's drowsiness status.