• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2009년도 정기 학술대회
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• pp.6-9
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• 2009

교량, 댐, 터널 등의 대형 구조물 및 항공기 등의 기계 구조물의 경우 그 중요성과 함께 노후화 및 손상의 발생에 의한 구조물의 사고를 미연에 방지하기 위해 효과적인 건전도 평가와 손상 검색에 대한 연구가 최근 급증하고 있으며 특히 압전소자를 활용하여 구조물의 손상을 추정하는 기법들이 많이 개발되고 있다. 또한, 최근에는 압전소자와 계측기 사이를 케이블을 이용하여 연결할 경우 실제 대형 구조물에 설치 시 비효율적인 부분이 많아 무선 기반 계측시스템이 개발되고 있다. 그러나 이러한 무선 계측 시스템의 경우 압전소자의 가진 및 계측되는 데이터의 전송을 위해 별도의 전원공급이 필요하기 때문에 배터리가 포함되도록 구성되며 이럴 경우 그 수명이 제한적이기 때문에 실제 구조물에 활용 시 문제로 제기되고 있다. 이러한 배경에서 본 연구에서는 레이저를 통해 원격지의 압전소자에 무선으로 전원을 공급하여 가진시키는 시스템을 제안하였다. 압전소자를 가진시키고자 하는 임의의 파형으로 레이저를 변조(modulation)시키고 대기 중으로 전송하여, 압전소자와 연결된 광검출기(photodiode)를 통해 전기적 신호로 변환하여 최종적으로 가진시키게 된다. 이러한 시스템을 실내 실험을 통하여 구현하였으며 그 효용성을 살펴보았다.

• 한국음향학회지
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• 제23권1호
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• pp.1-7
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• 2004

본 연구에서는 항원-항체 결합반응을 통해 액상의 단백질 분자를 감지할 수 있는 SH형 SAW센서를 개발하였다. 측정하고자 하는 항원으로는 anti-Human-immune-globulin (anti-HigG) 단백질을, 이에 대응하는 항체로는 HigG를 채택하였다. 압전 단결정 LiTaO₃를 사용하여 100 MHz로 발진되는 센서를 제작하고, 센서의 지연선 위에 Ti/Au층을 증착하였다. 증착된 Au층 위에 SAM (self assembled monolayer)을 형성시켜서 추가되는 항원의 농도에 의한 센서의 주파수 변화를 측정하였다. 개발된 센서의 최소검출단위는 노이즈 레벨 400 Hz 이하 값에 10.8 ng/ml/Hz의 민감도를 가지며, anti-HigG 항원의 질량하중 효과에 대해 안정적인 반응을 보였다.

• Advances in aircraft and spacecraft science
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• 제5권4호
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• pp.459-475
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• 2018

In the field of aerospace engineering, accurate control of a spacecraft's orientation is often very important to mission success. Therefore, attitude control is a technically plentiful and extensively studied subject in controls literature during recent decades. This investigation of spacecraft attitude control is assumed to address two important aspects of the problem solutions. One sliding mode anti-disturbance control for utilization of faulty actuator components and another one disturbance observer based control to improve the pointing accuracy in the absence of anti-vibration equipment for the elastic appendages like a solar panel. Simultaneous occurrence of vibration due to flexible appendages and reaction degradation due to failure in attitude actuators complicates this case. The advantage of this method is acquisition proper control by the combination of disturbance observer and sliding mode compensation that form a fault tolerant control for the concerned satellite attitude control system. Furthermore, the proposed composite method indicates that occurrence the failure in actuators and even elastic solar panel vibration effect may be handled directly without reconfiguring the control components or providing piezoelectric devices. It's noteworthy, attitude quaternion and angular velocity commands are robustly tracked via controllers to become inclined to zero.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.583-588
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• 2007

This paper investigates the vibration characteristics of a wire-bonding transducer horn for high speed welding devices. The sample wire-bonder uses the input frequency of 136 kHz. The ultrasonic excitation causes the various vibrations of transducer horn and capillary. The vibration modes and frequencies close to the exciting frequency are identified using ANSYS. The nodal lines and amplification ratio of the ultrasonic horn are also obtained in order to evaluate the bonding performance of the sample wire-bonder system. The FEM results and experimental results show that the sample wire-bonder system uses the bending mode of 136 kHz as principal motion for bonding. The major longitudinal mode exists at 119 kHz below the excitation frequency. It is recommeded that the sample system is to set the excitation frequency at 119 kHz to improve bonding performance.

• Composites Research
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• 제15권3호
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• pp.18-29
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• 2002

본 논문에서는 얇은 벽보로 모델링 한 위성체 구조물에 입사되는 열 하중에 의해 발생하는 굽힘 진동과 열적 플러터에 대하여 연구하였다. 복합재료 얇은 벽보는 회전관성과 1차, 2차 와핑, 전단변형의 비고전적 요소를 포함한다. CUS구조물로 모델링한 복합재료 얇은 벽보의 열 진동 특성은 적층 순서와 섬유강화복합재료의 방향특성인자로부터 기인된 종방향 굽힘과 횡방향 굽힘의 언성과 관련하여 연구되었다. 수치 해석적인 방법으로 열적 플러터의 안정성 영역의경계값을 구하였으며, 태양 열 플럭스의 입사각, 감쇠계수, 섬유각의 변화에 의한 보의 변위를 구하였다. 주 구조물에 압전소자를 부착하여, 감지기와 작동기로 사용하여 제어해석을 수행하였다.

• 전기학회논문지
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• 제56권3호
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• pp.566-570
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• 2007

The specific electrical, optical and acoustic properties of Zinc Oxide (ZnO) are important for semiconductor process which has many various applications. Piezoelectric ZnO films has been widely used for such as transducers, bulk and surface acoustic-wave resonators, and acousto-optic devices. In this study, we investigated etch characteristics of ZnO thin films in inductively coupled plasma etch system with $BCl_3/Ar$ gas mixture. The etching characteristics of ZnO thin films were investigated in terms of etch rates and selectivities to $SiO_2$ as a function of $BCl_3/Ar$ gas mixing ratio, RF power, DC bias voltage and process pressure. The maximum ZnO etch rate of 172 nm/min was obtained for $BCl_3$ (80%)/Ar(20%) gas mixture. The chemical states on the etched surface were investigated with X-ray photoelectron spectroscopy (XPS).

• Journal of Electrical Engineering and Technology
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• 제13권6호
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• pp.2434-2440
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• 2018

A new type of piezoelectric micromachined ultrasonic transducer (pMUT) with high resonant frequency was developed by using a thin lead zirconate titanate (PZT) as an insulation layer on a floating $10{\mu}m$ silicon membrane. The PZT insulation layer facilitated acoustic impedance matching at active pMUT, leading to a high performance in the acoustic conversion property compared with the transducer using $SiO_2$ insulation layer. The fabricated ultrasonic devices were wirelessly measured by connecting two identical acoustic transducers to two separate ports in a single network analyzer simultaneously. The acoustic wave emitted from a transducer induced a $3.16{\mu}W$ on the other side of the transducer at a distance of 2 cm. The transducer performances in terms of device diameters, PZT thickness, annealings, and different DC polings, etc. were investigated. COMSOL simulation was also performed to predict the device performances prior to fabrication. Based on the COMSOL simulation, the device was fabricated and the results were compared.

• 한국진공학회지
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• 제8권4A호
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• pp.425-431
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• 1999

$Pb(Zr_{0.52}, Ti_{0.48})O_3$ (PZT) thick films as an actuating material with conducting oxides, $(La_{0.5}Sr_{0.5}) CoO_3$ (LSCO), have been fabricated by sol-gel method for Optical Micro-Electro-Mechanical System (MEMS) devices, in which PZT/LSCO/SiO2 structures were used. In order to improve the adhesion to LSCO solution in order to enhance the wetting behavior of a water-based LSCO precursor solution and further to improve the adhesion between LSCO and $SiO_2$ layers. PZT films were made using 1-3 propanediol based precursor solution which has a high viscosity and a boiling point appropriate for thick film fabrication. In the precursor solution, Ti-propoxied and Zr-propoxied are partially substituted with acetylacetone to achieve the solution stability while maintaining reactivity. Crack free PZT films (0.8~1$\mu\textrm{m}$) have been successfully fabricated at crystallization temperatures above $700^{\circ}C$. Dielectric constants and dielectric losses of the PZT films were 900~1200and 2~5%, respectively. Piezoelectric constant $d_{33}$ of the PZT films constrained by a substrate were 200pm/V at 100kV/cm.

• 한국전기전자재료학회논문지
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• 제22권4호
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• pp.314-317
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• 2009

This paper describes the temperature characteristics of polycrystalline 3C-SiC micro resonators. The $1.2{\mu}m$ and $0.4{\mu}m$ thick polycrystalline 3C-SiC cantilever and doubly clamped beam resonators with $60{\sim}100{\mu}m$ lengths were fabricated using a surface micromachining technique. Polycrystalline 3C-SiC micro resonators were actuated by piezoelectric element and their fundamental resonance was measured by a laser vibrometer in vacuum at temperature range of $25{\sim}200^{\circ}C$. The TCF(Temperature Coefficient of Frequency) of 60, 80 and 100 On long cantilever resonators were -9.79, -7.72 and -8.0 ppm/$^{\circ}C$. On the other hand, TCF of 60, 80 and $100{\mu}m$ long doubly clamped beam resonators were -15.74, -12.55 and -8.35 ppm/$^{\circ}C$. Therefore, polycrystalline 3C-SiC resonators are suitable with RF MEMS devices and bio/chemical sensor applications in harsh environments.

• 한국생산제조학회지
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• 제24권5호
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• pp.530-534
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• 2015

Ultrasonic nanocrystal surface modification (UNSM) is an example of a nanoscale-surface modification that has become noticeable because of its effects on the mechanical improvement of metallic materials. UNSM equipment needs to be both utilized and improved. The equipment is based on an ultrasonic waveguide whose role is to strike surfaces of metallic materials to achieve nanoscale deformation. In this paper, we introduce the development of one kind of UNSM equipment. Using piezoelectric elements, we repeatedly design and fabricate a 20-kHz ultrasonic waveguide. With respect to the composition of the equipment, the waveguide is automatically transferred by two axial stages automatically. In addition, a static force is constantly applied by pneumatic devices. We perform an experiment to verify the feasibility of the equipment.