• 센서학회지
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• 제27권2호
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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.

• 센서학회지
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• 제27권5호
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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%.

• 한국물환경학회지
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• 제24권1호
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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.

• 전기학회논문지
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• 제57권1호
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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.

• 센서학회지
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• 제29권4호
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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.

• 센서학회지
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• 제23권3호
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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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• 제22권6호
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• pp.378-386
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• 2007

바이오센싱 디바이스는 본질적으로 생체인식소재와 신호전달장치로 구성된 집적화, 소형화된 분석시스템으로 많은 장점을 가지고 있다. 고민감도, 선택도, 단순성, 다성분 측정능력, 즉시측정능력 뿐 아니라 매우 작고, 고가의 장치가 필요없는 장점이 있다. 바이오센싱 디바이스의 개발을 위해서는 두 가지의 핵심요소기술이 필요하다. 이것은 생체인식소재모듈의 제작 (리셉터 개발 및 고정화기법)과 신호발생기술을 포함한 신호전달장치의 개발이다. 효소, DNA/RNA, 단백질, 세포 등의 다양한 생체인식소재가 바이오센싱 디바이스 제작을 위해 이용되어져 왔고, 신호전달시스템도 전기화학적, 광학적, mass sensitive transducer를 중심으로 매우 활발히 연구되어져 왔다. 본 고에서는 최근 개발된 바이오센싱디바이스에 대해 다루고, 향후 전망에 대해 논하고자 한다.

• 마이크로전자및패키징학회지
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• 제14권2호
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• pp.59-63
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• 2007

간단한 PCB 공정을 기반으로 하여 저가형의 후막 가스 센서 모듈을 제안하고자 한다. 제안된 센서 모듈은 $NO_2/H_2$ 가스 센서와 습도센서, 그리고 히터를 포함한다. $NO_2/H_2$ 가스와 상대 습도 센서들은 각각 $SnO_2$와 $BaTiO_3$ 나노 입자들을 PCB 기판에서의 IDT(interdigital Transducer)에 프린팅 함으로써 제작되었다. 처음에 1% $H_2$ 가스를 센서 쳄버에 공급하고 4분 후 $H_2$가스 공급을 멈추고 공기를 주입시켰으며, 이러한 동작을 반복적으로 수행하였다. 마찬가지로 $NO_2$로 감지하도록 같은 동작을 실행하였다. $H_2$ 가스에 대한 결과는 도전성의 증가로 인하여 0.8V에서 3.5V로 증가함을 볼 수 있었으며, $H_2$ 가스를 주입한후의 반응 시간은 65초였다. $NO_2$ 가스의 경우는 도전성이 감소함으로써 2.7 V의 전압강하가 일어 났으며, 반응시간은 3초였다.

• 비파괴검사학회지
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• 제9권1호
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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.

• 전기학회논문지
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• 제61권9호
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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.