• 설비공학논문집
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• 제17권11호
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• pp.1022-1027
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• 2005

An experimental study is conducted to investigate the characteristics of the ion wind generated by the electric field between a needle electrode and the parallel plate electrodes. The ion wind enhances heat and mass transfer between the surface and the surrounding gas. Moreover such enhancement makes no noise or vibration. This study is conducted to develop the electronic cooling device. The measured gas velocities and heat transfer coefficients are proportional to the applied voltage. The heat transfer coefficient can be increased as compared with a natural convection. The maximum enhancement of heat transfer obtained in this system is $47\%$ for 3 W in heat transfer rate.

• Smart Structures and Systems
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• 제26권3호
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• pp.331-343
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• 2020

In this paper, based on the CPT, motion equations for a sandwich plate containing a core and two integrated face-sheets have derived. The structure rests on the Visco-Pasternak foundation, which includes normal and shear modules. The piezo-magnetic core is made of CoFe₂O₄ and also is subjected to 3D magnetic potential. Two face sheets at top and bottom of the core are under electrical fields. Also, in order to obtain more accuracy, the effect of flexoelectricity has took into account at face sheets' relations in this work. Flexoelectricity is a property of all insulators whereby they polarize when subject to an inhomogeneous deformation. This property plays a crucial role in small-scale rather than macro scale. Employing CPT, Hamilton's principle, flexoelectricity considerations, the governing equations are derived and then solved analytically. By present work a detailed numerical study is obtained based on Piezoelectricity, Flexoelectricity and modified couple stress theories to indicate the significant effect of length scale parameter, shear correction factor, aspect and thickness ratios and boundary conditions on natural frequency of sandwich plates. Also, the figures show that there is an excellent agreement between present study and previous researches. These finding can be used for automotive industries, aircrafts, marine vessels and building industries.

• 센서학회지
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• 제21권2호
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• pp.114-120
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• 2012

This paper describes the design, fabrication and testing of a micromachined resonant accelerometer consisting of a symmetrical pair of proof masses and double-ended tuning fork(DETF) oscillators. Under the external acceleration along the input axis, the proof mass applies forces to the oscillators, which causes a change in their resonant frequency. This frequency change is measured to indicate the applied acceleration. Pivot anchor and leverage mechanisms are adopted in the accelerometer to generate larger force from a proof mass under certain acceleration, which enables increasing its scale factor. Finite element method analyses have been conducted to design the accelerometer and a silicon on insulator(SOI) wafer with a substrate glass wafer was used for fabricating it. The fabricated accelerometer has a scale factor of 188 Hz/g, which is shown to be in agreement with analysis results.

• 한국지구과학회지
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• 제34권6호
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• pp.588-601
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• 2013

최근 지구물리 물리탐사 분야에서 경사각과 방위각 정보는 시추공 물리검층 및 물리탐사 자료보정을 위한 시추공 편차검층, 이동형 실시간 자료획득 시스템, 기타 지구물리 모니터링 시스템 등 다양하게 활용되면서 그 중요성이 높아지고 있다. 특히 최근 셰일가스의 개발이 가능하게 한 방향시추 기술에서도 경사각과 방위각 정보는 필수일 정도로 그 응용범위가 매우 넓다. 따라서 여러 분야에 응용될 수 있는 경사각과 방위각 측정 시스템의 초소형 옥외 저전력 운용이 절실해졌다. 본 논문에서는 최신 CMOS 저전력, 고성능 MCU 및 멤스(MEMS) 자세방위기준장치(AHRS)를 도입하여 초소형, 저전력으로 제작된 다용도 야외시험용 실시간 경사각과 방위각 연속 측정 시스템 개발 연구의 결과를 제시하고자 한다. 시스템은 최소 지름 42 mm의 존데 내에 설치될 수 있도록 초슬림 형태로 제작되었으며 실시간 데이터 획득이 가능할 뿐만 아니라 엔코더, DGPS 연동으로 운용 확장이 가능하여 다양한 응용이 기대된다.

• 한국자동차공학회논문집
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• 제16권2호
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• pp.58-65
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• 2008

The finite element programs have been developed for structure, collision, flow, dynamics, heat transfer, acoustics, electromagnetism, MEMS (Micro Electro Mechanical Systems), and etc. These programs can be classified as either "package" program or "single purpose" program. Single purpose programs usually have convenient and powerful functions, but these programs have limited expandability to different fields of analysis. Therefore, the method to converter the analysis results of single purpose program to other programs is needed. In the research, multi-body data conversion methods of 1) finite element model and 2) solid model were created to convert fluid analysis result of CFD-ACE+ to ANSYS data structure. Automatic boundary condition algorithms were developed for blade, and finite element model was compared with solid model. It is expected that, by sealess data transfer, the Multi-body Data Conversion Program could reduce the development period of torque converters.

• 로봇학회논문지
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• 제11권3호
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• pp.156-162
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• 2016

For the underwater localization, acoustic sensor systems are widely used due to greater penetration properties of acoustic signals in underwater environments. On the other hand, the good penetration property causes multipath and interference effects in structured environment too. To overcome this demerit, a localization method using the attenuation of electro-magnetic(EM) waves was proposed in several literatures, in which distance estimation and 2D-localization experiments show remarkable results. However, in 3D-localization application, the estimation difficulties increase due to the nonuniform (doughnut like) radiation pattern of an omni-directional antenna related to the depth direction. For solving this problem, we added a depth sensor for improving underwater 3D-localization with the EM wave method. A micro scale pressure sensor is located in the mobile node antenna, and the depth data from the pressure sensor is calibrated by the curve fitting algorithm. We adapted the depth(z) data to 3D EM wave pattern model for the error reduction of the localization. Finally, some experiments were executed for 3D localization with the fast calculation and less errors.

• 센서학회지
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• 제18권5호
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• pp.359-364
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• 2009

This paper presents flexible electrocardiography(ECG) sensors using micro electro mechanical systems(MEMS) and flexible printed circuit(FPC) technology. By using FPC technology, ECG sensors which consisted of an outer hook-shaped electrode and an inner circular-shaped electrode were fabricated on the polyimide substrate. Thereafter, the bipolar ECG sensor was miniaturized using MEMS technology. The ECG measurement capability was examined by attaching the sensor to the human chest and wrist. Performance of the proposed sensors was then compared with ECG measured by commercial Ag/AgCl electrodes. It was verified that ECG could be measured using proposed sensors at only single body.

• Current Applied Physics
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• 제18권11호
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• pp.1327-1337
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• 2018

This paper investigates the vibration behavior of pristine and defected triangular graphene sheets; which has recently attracted the attention of researchers and compare these two types in natural frequencies and sensitivity. Here, the molecular dynamics method has been employed to establish a virtual laboratory for this purpose. After measuring the different parameters obtained by the molecular dynamics approach, these data have been analyzed by using the frequency domain decomposition (FDD) method, and the dominant frequencies and mode shapes of the system have been extracted. By analyzing the vibration behaviors of pristine triangular graphene sheets in four cases (right angle of 45-90-45 configuration, right angle of 60-90-30 configuration, equilateral triangle and isosceles triangle), it has been demonstrated that the natural frequencies of these sheets are higher than the natural frequency of a square sheet, with the same number of atoms, by a minimum of 7.6% and maximum of 26.6%. Therefore, for increasing the resonance range of sensors based on 2D materials, nonrectangular structures, and especially the triangular structure, can be considered as viable candidates. Although the pristine and defective equilateral triangular sheets have the highest values of resonance, the sensitivity of defective (45,90,45) triangular sheet is more than other configurations and then, defective (45,90,45) sheet is the worst choice for sensor applications.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 하계학술대회 논문집 C
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• pp.1025-1027
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• 1995

SEG(Selective Epitaxial Growth) and ELO(Epitaxial Lateral Growth) of Silicon offer new opportunities in the fabrication of MEMS(Micro Electro-Mechanical Systems) structures. SEG of silicon enables the stacking of junctions in addition to those resulting from the standard bipolar process and this properly was utilized for the fabrication of an improved-performance color sensor. When the crystalline growth takes place through the seed windows and proceeds over the dielectric, after reaching the surface, it form an ELO silicon layer and this ELO-Si can be modified into various structures for MEMS application such as cantilevers, beams, diaphragms.

• Smart Structures and Systems
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• 제11권5호
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• pp.453-476
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• 2013

DuraMote is a remote sensing system developed for the "NIST TIP project: next generation SCADA for prevention and mitigation of water system infrastructure disaster". It is designed for supervisory control and data acquisition (SCADA) of ruptures in water pipes. Micro-electro mechanical (MEMS) accelerometers, which record the vibration of the pipe wall, are used detect the ruptures. However, the performance of Duramote cannot be verified directly on a water distribution system because it lacks an acceptable recordable level of ambient vibration. Instead, a long-span cable-stayed bridge is an ideal test-bed to validate the accuracy, the reliability, and the robustness of DuraMote because the bridge has an acceptable level of ambient vibration. The acceleration data recorded on the bridge were used to identify the modal properties of the structure and to verify the performance of DuraMote. During the test period, the bridge was subjected to heavy rain, wind, and a typhoon but the system demonstrates its robustness and durability.