• Journal of Sensor Science and Technology
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• v.27 no.2
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• pp.112-117
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• 2018

In this study, a bender-type piezoelectric energy harvester was fabricated and evaluated to compensate for the disadvantages of high-power generation only in the resonance frequency range of a piezoelectric harvester using a piezoelectric cantilever. The generated power was investigated according to various changes in the vibration environment. Compared with the piezoelectric cantilever module, the bender-type piezoelectric module showed a larger number of peak voltages. The primary peak voltage shifted toward the low frequency when the spring was coupled to the bender-type piezoelectric module. The harvester of the three bender-type modules had a vibration frequency exceeding 1 mW in the 34-45 Hz range and generated 3.112 mW of power at the vibration frequency of 38 Hz. The harvester of the six bender-type modules had a vibration frequency exceeding 1 mW in the 31-45 Hz range and generated 3.081 mW of power at the vibration frequency of 35 Hz.

• Journal of Sensor Science and Technology
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• v.27 no.5
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• pp.352-356
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• 2018

This paper relates to a technology for monitoring a liquefied gas storage tank in the special gas field where demand is increasing owing to the continuous growth of related fields such as the semiconductor, display, and ICT convergence electronics industries. We have proposed a system for real - time monitoring using wireless sensor network technology, and implemented a system consisting of a sensor unit, transmitter module, and receiver module to be attached to a liquefied gas storage tank. The system was applied to LCO2 tanks among various liquefied gas storage tanks to verify the feasibility. The storage tanks employed in the experiments has capacities of 16,179 l and was 1,920 mm in inner diameter. Furthermore, the density was 1.03 g/l. The measured data were compared with reference data on the remaining gas level versus the $CO_2$ height of the surface, expressed using a conventional water meter, provided by an existing storage tank supplier. The experimental results show that the data is similar to the standard data provided by the tank supplier, and has a high accuracy and reliability within an error range of 0.03%.

• Journal of Korean Society on Water Environment
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• v.24 no.1
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• pp.129-134
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• 2008

Ultrasonic cavitational energy distributions were measured in a large-scale sonoreator. In application of 110 and 170 kHz of ultrasound, the cavitational energy was just detected near the transducer module. However 35 and 72 kHz ultrasound made good distributions from the module to the end of the sonoreactor, Especially, 72 kHz ultrasound application showed most stable and highest cavitational energy value through the whole length. In the comparison between input power and cavitational energy, linear relationships were obtained in 35 and 72 kHz and it was anticipated that these results would be used for the optimization of input power for the design of sonoreactors. And three dimensional energy distribution was depicted through the mapping of cavitaional energy. Average energy in the large-scale sonoreactor was estimated as 62.8 W, which was about 40 % of input power.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.1
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• pp.142-147
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• 2008

Abdominal circumference changes due to breathing by the respiratory muscle activity such as diaphragm, which would partially represent the lung volume variation. The present study introduced conductive rubber molded in a cord shape incorporated with a patient's pants. The conductive rubber cord operated as a displacement transducer to measure the lung or abdominal volume changes. Signal extraction circuitry was developed to obtain the volume and its derivative(or the flow) signals followed by wireless transmission based on the Zigbee communication protocol in a size of $65mm{\times}105mm$ easily put in pocket. Breathing frequency was accurately evaluated and breath pattern analysis seemed feasible, since respiratory behaviours such as maximal inspiration and cough were well identified. Remote wireless receiver module also enabled to monitor both volume and flow signals during resting breathing on a PC terminal.

• Journal of Sensor Science and Technology
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• v.29 no.4
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• pp.261-265
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• 2020

In cantilever type piezoelectric energy harvester, the amount of power generation decreases rapidly when outside a certain frequency. The thickness and weight of the cantilever metal plate were modified to develop cantilevers that could produce high power over a wide frequency range. The thicker the cantilever, the higher the power in the higher frequency range. As the weight of the mass increased, the cantilever tended to generate higher power, and the frequency band decreased. A 0.6 mm metal plate cantilever that had a mass of 3.3 g generated power that exceeded 3 mW within the 91-102 Hz range, with average and output values of 9.484 mW and 20.748 mW, respectively, at 99 Hz.

• Journal of Sensor Science and Technology
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• v.23 no.3
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• pp.178-184
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• 2014

Key components of implantable hearing aids are consist of an acoustic sensor that collect external sound by suppressing the body noise, a signal processor module for compensation algorithm of hearing loss, and a output transducer which has tiny size but have high efficiency, respectively. In the partial implantable hearing aids, technologies of transducer and signal processor are so matured that can be applied not too much difficulty. However, due to the difficulties in implantable acoustic sensor technology, such as minimization of masticatory sound and damage of sensor's membrane from external impact, practical use of fully implantable hearing aids have not successful so far. In this paper, we have proposed a novel implantable acoustic sensor which has trans-tympanic structure, and is verified that the proposed method can be very useful for fully implantable hearing aids by cadaveric experiments.

• KSBB Journal
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• v.22 no.6
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• pp.378-386
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• 2007

Bio-sensing devices, which are basically integrated and miniaturized assay systems consisted of bioreceptor and signal transducer, are advantageous in several ways. In addition to their high sensitivity, selectivity, simplicity, multi-detection capability, and real time detection abilities, they are both very small and require relatively inexpensive equipments. Two core technologies are required to develop bio-sensing devices; the fabrication of biological receptor module (both of receptor development and immobilisation of them) and the development of signal transducing instruments containing signal generation technique. Various biological receptors, such as enzymes, DNA/RNA, protein, and cell were tried to develop bio-sensing devices. And, the signal transducing instruments have also been extensively studied, especially with regard to electrochemical, optical, and mass sensitive transducers. This article addresses bio-sensing devices that have been developed in the past few years, and also discusses possible future major trends in these devices.

• Journal of the Microelectronics and Packaging Society
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• v.14 no.2 s.43
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• pp.59-63
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• 2007

This paper presented a low-cost thick film gas sensor module, which was based on simple PCB (Printed Circuit Board) process. The proposed sensor module included a $NO_2/H_2$ gas sensor, a relative humidity sensor, and a heating element. The $NO_2/H_2$ gas and relative humidity sensors were realized by screen-printing $SnO_2,\;BaTiO_3$ nano-powders on IDTS (Interdigital Transducer) of a PCB substrate, respectively. At first 1% $H_2$ gas flowed into the sensor chamber. After 4 min, air filled the chamber while $H_2$ gas flow stopped. This experiment was performed repeatedly. The Identical procedure was used for the $NO_2$ detection. The result for sensing $H_2$ gas showed the increase of voltage from 0.8V to 3.5V due to the conductance increase and its reaction response time by hydrogen flow was 65 sec. $NO_2$ sensing results showed 2.7 V voltage drop due to the conductance decrease and its response time was 3 sec through a voltage monitoring.

• Journal of the Korean Society for Nondestructive Testing
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• v.9 no.1
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• pp.30-38
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• 1989

Since the nuclear power plants in Korea have been operated in 1979, the nondestructive testing (NDT) of pressure vessels and/or piping welds plays an important role for maintaining the safety and integrity of the plants. Ultrasonic method is superior to the other NDT method in the viewpoint of the detectability of small flaw and accuracy to determine the locations, sizes, orientations, and shapes. As the service time of the nuclear power plants is increased, the radiation level from the components is getting higher. In order to get more quantitative and reliable results and secure the inspector from the exposure to high radiation level, automation of the ultrasonic equipments has been one of the important research and development(R & D) subject. In this research, it was attempted to visualize the shape of flaws presented inside the specimen using a Modified C-Scan technique. In order to develope Modified C-Scan technique, an automatic ultrasonic scanner and a module to control the scanner were designed and fabricated. IBM-PC/XT was interfaced to the module to control the scanner. Analog signals from the SONIC MARK II were digitized by Analog-Digital Converter(ADC 0800) for Modified C-Scan display. A computer program has been developed and has capability of automatic data acquisition and processing from the digital data, which consist of maximum amplitudes in each gate range and locations. The data from Modified C-Scan results was compared with shape from artificial defects using the developed system. Focal length of focused transducer was measured. The automatic ultrasonic equipment developed through this study is essential for more accurate, reliable, and repeatable ultrasonic experiments. If the scanner are modified to meet to appropriate purposes, it can be applied to automation of ultrasonic examination of nuclear power plants and helpful to the research on ultrasonic characterization of the materials.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.9
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• pp.1350-1357
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• 2012

Medical system for personal health management recently changes its paradigm from hospital service to self home care based on ubiquitous technology for healthcare anywhere at any time. The present study developed a wireless bio-signal measurement system for patients to self manage pulmonary disease and benign prostate hyperplasia(BPH), both of which are chronic diseases with increasing frequency in modern society. Velocity-type respiratory air flow transducer adapted to develop respiratory module for pulmonary disease management was simplified in structure to measure uni-directional flow since most important diagnostic parameters are evaluated on the expiratory flow signal only. Standard weight measurement technique was introduced to obtain urinary flow signal for BPH management. Three load cell signals were acquired for averaging to minimize noise, followed by accuracy evaluation. Transmission and receiver modules were also developed with user program for wireless communication. Averaged relative errors were 2.05 and 1.02% for respiratory volume and maximal flow rate, respectively, and the relative error was 2.17% for urinary volume, demonstrating that both modules enabled very accurate measurements. Wireless communication distance was verified within 15m, long enough for home care application. The present system allows the user to select a necessary measurement module on a particular health demand and to immediately provide the self-test results, thus better quality health care would be possible.