• 한국전자통신학회논문지
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• 제13권5호
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• pp.1093-1100
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• 2018

웨어러블 기기에서 반도체의 소형화 및 저전력 기술이 빠르게 진행됨에 따라 다양한 초소형 형태의 응용서비스를 제공할 수 있게 되었다. 최근에는 태양열, 피에조, 마찰 등 다양한 에너지 하베스터를 이용해 저전력 반도체는 매우 낮은 전원으로도 동작할 수 있게 되었다. 웨어러블 상황에서의 대부분에 에너지 하베스팅은 비연속적(non-linear)으로 발전된다. 이에 따라 본 연구에서는, 3Hz의 낮은 주파수기반 디바이스 플랫폼을 제작하여 실험적으로 평가하였다. 본 연구는 비연속적 발전 환경을 고려해, 2단계의 저장환경과 사용된 에너지 발전소자의 맞춘 에너지 고효율 변환 플랫폼 설계하였다. 또한, 비연속적 에너지 수집 환경에서 안정적인 에너지를 저장 유지를 통해 약 4.67mW/min 발전하였다.

• Journal of Electrical Engineering and Technology
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• 제5권2호
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• pp.337-341
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• 2010

In this paper, an extremely low voltage operated micro corner cube retroreflector (CCR) was fabricated for free-space optical communication applications by using bulk silicon micromachining technologies. The CCR was comprised of an orthogonal vertical mirror and a horizontal actuated mirror. For low voltage operation, the horizontal actuated mirror was designed with two PZT cantilever actuators, torsional bars, hinges, and a mirror plate with a size of $400{\mu}m{\times}400{\mu}m$. In particular, the torsional bars and hinges were carefully simulated and designed to secure the flatness of the mirror plate by using a finite element method (FEM) simulator. The measured tilting angle was approximately $2^{\circ}$ at the applied voltage of 5 V. An orthogonal vertical mirror with an extremely smooth surface texture was fabricated using KOH wet etching and a double-SOI (silicon-on-insulator) wafer with a (110) silicon wafer. The fabricated orthogonal vertical mirror was comprised of four pairs of two mutually orthogonal flat mirrors with $400{\mu}m4 (length) $\times400{\mu}m$ (height) $\times30{\mu}m$ (thickness). The cross angles and surface roughness of the orthogonal vertical mirror were orthogonal, almost $90^{\circ}$ and 3.523 nm rms, respectively. The proposed CCR was completed by combining the orthogonal vertical and horizontal actuated mirrors. Data transmission and modulation at a frequency of 10 Hz was successfully demonstrated using the fabricated CCR at a distance of approximately 50 cm.

• 센서학회지
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• 제5권3호
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• pp.65-73
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• 1996

수액을 장시간 환자에게 주입할 때 적절한 주입량, 주입률을 조절하는 것이 중요하다. 부적절한 주입량은 환자의 회복에 좋지 않은 영향을 끼칠 수 있으므로 주입량을 감지하는 센서의 신뢰도는 인퓨전 펌프 시스템에 많은 영향을 미친다. 본 연구에서는 인퓨전 펌프 시스템에 사용될 3가지 센서의 성능을 검토하였다. 피에조 필름, 광트렌지스터 및 광 다이오드 어레이의 3가지 센서가 비교되었으며 제안하는 신호 처리 기법과 광 다이오드 어레이를 사용한 기법을 이용하여 간섭과 진동 조도변화 센서의 위치에 따른 감도 변화등의 영향을 줄일 수 있었다. 실험 결과 광 다이오드 어레이가 다른 센서들에 비하여 높은 신지도를 보여 주었다.

• 한국항공우주학회지
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• 제37권8호
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• pp.744-750
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• 2009

본 논문에서는 압전 작동기로 구동되는 무밸브 마이크로 펌프의 펌프 성능을 계산하였다. 선행연구에서 개발된 마이크로 펌프는 4층의 경량 압전 복합재료 작동기, PDMS로 된 챔버와 2개의 디퓨져로 이루어져 있다. 유한요소 해석은 압전 영역, 구조 영역 및 유체 영역을 완전 연성하여 수행되었다. 구조 및 압전 영역의 해석은 ANSYS를 사용하였으며, 유체영역의 해석은 ANSYS CFX를 사용하여 수행하였다. 작동 주파수가 10 Hz와 40 Hz인 경우에 대한 해석을 수행하여 작동 주파수가 유동 특성에 미치는 영향을 고찰하였다. 또한 300 Hz까지의 유동 해석을 통하여 작동 주파수에 따른 유량을 계산하였다.

• 한국정밀공학회지
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• 제5권1호
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• pp.84-93
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• 1988

The on-line detection of the chip flow is one of the most important technologies in com- pletly automatic operation of machine tool, such as FMS and Unmanned Factories. This problem has been studied by many researchers, however, it is not solved as yet. For the recognition of chip flow in this study, the dynamic cutting force components due to the chip breaking were measured by dynamometer of piezo-electric type, and the frequency components of cutting force were also analyzed. From the measured results, the effect of cutting conditions and tool geometry on the dynamic cutting force component and chip formation were investigated in addition to the relationships between frequency of chip breaking (fB) and side serrated crack (fC) of chip. As a result, the following conclusions were obtaianed. 1) The chip formations have a large effect on the dynamic cutting force components. When chip breaking takes place, the dynamic cutting force component greatly increases, and the peridoic components appear, which correspond to maximum peak- frequency. 2) The crater wear of tool has a good effect on the chip control causing the chiup to be formed as upward-curl shape. In this case, the dymamic cutting force component greatly increases also 3) fB and fC of chip are closely corelated, and fC of chips has a large effect on the change of the situation of chip flow and dynamic cutting force component. 4) Under wide cutting conditions, the limit value (1.0 kgf) of dynamic cutting force component exists between the broken and continuous chips. Accordingly, this value is suitable for recognition of chip flow in on-line control of the cutting process.

• Design & Manufacturing
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• 제13권1호
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• pp.55-60
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• 2019

Smart-phone in the recently released high-end applied to the camera module is equipped with the most features auto focusing camera module. Also, auto focusing camera module is divided into voice coil motor, encoder, and piezo according to type of motion mechanism. Auto focusing camera module is composed of voice coil motor (VCM) as an actuator and leaf spring as a guide and suspension. VCM actuator is made of magnet, yoke as a metal, and coil as a copper wire. Recently, the assembly as yoke and magnet is made by human resources. These process has a long process time and it is difficult to secure quality. Also, These process is not economical in cost, and productivity is reduced. Therefore, an automatic assembly as yoke and magnet is needed in the present process. In this paper, we have developed an automatic assembly device that can automatically assemble yoke and magnet, and performed verifying performance. Therefore, by using the developed automatic assembly device, it is possible to increase the productivity and reduce the production cost.

• 한국전기전자재료학회논문지
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• 제32권5호
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• pp.418-425
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• 2019

A piezoelectric ceramic fiber composite (PCFC) was successfully fabricated using $0.69Pb(Zr_{0.47}Ti_{0.53})O_3-0.31[Pb(Zn_{0.4}Ni_{0.6})_{1/3}Nb_{2/3}]O_3$ (PZT-PZNN) for use in small-scale wind energy harvesters. The PCFC was formed using an epoxy matrix material and an array of Ag/Pd-coated PZT-PZNN piezo-ceramic fibers sandwiched by Cu interdigitated electrode patterned polyethylene terephthalate film. The energy harvesting performance was evaluated in a custom-made wind tunnel while varying the wind speed and resistive load with two types of flutter wind energy harvesters. One had a five-PCFC array vertically clamped with a supporting acrylic rod while the other used the same structure but with a five-PCFC cantilever array. Stainless steel (thickness: $50{\mu}m$) was attached onto one side of the PCFC to form the PZT-PZNN cantilever. The output power, in general, increased with an increase in the wind speed from 2 m/s to 10 m/s for both energy harvesters. The highest output power of $15.1{\mu}W$ at $14k{\Omega}$ was obtained at a wind speed of 10 m/s for the flutter wind energy harvester with the PZT-PZNN cantilever array. The results presented here reveal the strong potential for wind energy harvester applications to supply sustainable power to various IoT micro-devices.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2016년도 추계학술대회
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• pp.602-604
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• 2016

본 논문에서는 블루투스를 기반으로 실내의 조명, LED 그리고 알람시계를 제어할 수 있는 것을 제안한다. 제안된 블루투스 기반 LED 알람 무드등(Bluetooth based LED Alarm Lamp)은 블루투스 모듈을 이용하여 ON/OFF를 할 수 있으며, 조도센서 및 전압을 변압시켜 ON/OFF 및 빛 밝기를 조정할 수 있도록 설계하였다. 또한 7-segment를 이용하여 시계를 표시하였고 피에조 부조를 이용하여 시간에 맞춰 알람을 울리게 할 수 있도록 설계하였다. 그리고 터치센서를 이용하여 전압을 낮춰 빛 밝기를 조절할 수 있다. 또한 알람을 맞출 수 있는 기능을 추가하였다. 본 작품(블루투스 기반 LED 알람 무드등)은 환경이 어두울 때 전압이 유지되고 있다면 자동으로 ON되는 시스템으로 거주자의 방에 안락한 내부 환경을 제공할 수 있다. 그리고 약한 불빛으로 인한 수면 시간의 질을 향상시킬 수 있는 것에 중점을 두어 설계하였다.

• 한국전기전자재료학회논문지
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• 제35권1호
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• pp.72-79
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• 2022

Piezoelectric energy harvesting technologies, which can be used to convert the electricity from the mechanical energy, have been developed in order to assist or power the wearable electronics. To realize non-toxic and biocompatible electronics, the lead-free (Ba_0.85Ca_0.15)(Ti_0.90Zr_0.10)O₃ (BCTZ) nanoparticles (NPs) are being studied with a great attention as flexible energy harvesting device. Herein, piezoelectric hybrid nanocomposites were fabricated using BCTZ NPs-embedded poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] matrix to improve the performance of flexible energy harvester. Output performance of the fabricated energy device was investigated by the well-optimized measurement system during the periodically bending and releasing motions. The generated open-circuit voltage and the short-circuit current of the piezoelectric hybrid nanocomposite-based energy harvester reached up to ~15 V and ~1.1 ㎂, respectively; moreover, the instantaneous power of 3.5 ㎼ is determined from load voltage and current at the external load of 20 MΩ. This research is expected to cultivate a new approach to high-performance wearable self-powering electronics.

• 대한임베디드공학회논문지
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• 제17권1호
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• pp.9-17
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• 2022

As the COVID-19 pandemic situation worsens, the time spent indoors increases, and the exposure to indoor environmental pollution such as indoor air pollution and noise also increases, causing problems such as deterioration of human health, stress, and discord between neighbors. This paper designs and implements a system that measures and monitors indoor air quality and noise, which are representative evaluation criteria of the indoor environment. The system proposed in this paper consists of a particulate matter measurement subsystem that measures and corrects the concentration of particulate matters to monitor indoor air quality, and a noise measurement subsystem that detects changes in sound and converts it to a sound pressure level. The concentration of indoor particulate matters is measured using a laser-based light scattering method, and an error caused by temperature and humidity is compensated in this paper. For indoor noise measurement, the voltage measured through a microphone is basically measured, Fourier transform is performed to classify it by frequency, and then A-weighting is performed to correct loudness equality. Then, the RMS value is obtained, high-frequency noise is removed by performing time-weighting, and then SPL is obtained. Finally, the equivalent noise level for 1 minute and 5 minutes are calculated to show the indoor noise level. In order to classify noise into direct impact sound and air transmission noise, a piezo vibration sensors is mounted to determine the presence or absence of direct impact transmitted through the wall. For performance evaluation, the error of particulate matter measurement is analyzed through TSI's AM510 instrument. and compare the noise error with CEM's noise measurement system.