• Journal of Sensor Science and Technology
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• v.16 no.5
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• pp.377-383
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• 2007

We describe the fabrication and characterization of a doubly clamped multi-walled carbon nanotube (MWNT). The device was assembled by an application of electric field in solution. The MWNT was clamped on end of metal trench electrodes in solution and deposited with additional platinum (Pt) on edge of electrode for firmly suspending the MWNT by focused ion beam (FIB). The MWNTs range of diameter and length were 100 to 150 nm and 1.5 to $2{\mu}m$, respectively. Electrical characteristics of fabricated devices were measured by I-V curve and impedance analysis. The mechanical deformation was observed by resistivity in high air pressure. Resonant frequency around 6.8 MHz was detected and resistivity was linearly varied according to the magnitude of air pressure. This device could have potential applications in nanoelectronics and various sensors.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2004.04a
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• pp.373-380
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• 2004

This paper presents the feasibility of an impedance-based damage detection technique using piezoelectric (PZT) transducers for civil infrastructures such as steel bridges. The impedance-based damage detection method is based on monitoring the changes in the electrical impedance. Those changes in the electrical impedance are due to the electro-mechanical coupling property of the piezoelectric material and structure. An effective integrated structural health monitoring system must include a statistical process of damage detection that is automated and real time assessment of damage in the structure. Once measured, damage sensitive features from this impedance change can be statistically quantified for various damage cases. The results of the experimental study on three kinds of structural members show that cracks or loosened bolts/nuts near the PZT sensors may be effectively detected by monitoring the shifts of the resonant frequencies. The root mean square (RMS) deviations of impedance functions between before and after damages were also considered as a damage indicator. The subsequent statistical methods using the impedance signature of the PZT sensors were investigated.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.77.2-77.2
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• 2015

Recently, metamaterials attracted much attention because of the potential applications for superlens, cloaking and high precision sensors. We developed several dielectric metamaterials for enhancing antireflection or light trapping capability in solar energy harvesting devices. Colloidal lithography and electrochemical anodization process were employed to fabricate self-assembed nano- and microscale dielectric metamaterials in a simple and cost-effective manner. We improved broadband light absorption in c-Si, a-Si, and organic semiconductor layer by employing polystyrene (PS) islands integrated Si conical-frustum arrays, resonant PS nanosphere arrays, and diffusive alumina nanowire arrays, respectively. We also demonstrated thin metal coated alumina nanowire array which is utilized as an efficient light-to-heat conversion layer of solar steam generating devices. The scalable design and adaptable fabrication route to our light management nanostructures will be promising in applications of solar energy harvesting system. On the other hands, broadband invisible cloaks, which continuously work while elastically deforming, are developed using smart metamaterials made of photonic and elastic crystals. A self-adjustable, nearly lossless, and broadband (10-12GHz) smart meatamaterials have great potentials for applications in antenna system and military stealth technology.

• Proceedings of the KIEE Conference
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• 1992.07b
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• pp.757-758
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• 1992

At-cut quarts crystal has been applied as chemical vapour sensors. The responses of quartz crystal at 9 MHz coated with various lipids were determined for organic gases which showed different affinities for each lipid. The identification of odorants depending on the species of lipid used for coating is discussed in terms of the normalized resonant frequency shift pattern.

• Current Optics and Photonics
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• v.2 no.1
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• pp.85-89
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• 2018

This paper presents a new, efficient hybrid photonic-plasmonic structure. The proposed structure efficiently and with very high accuracy combines the resonant mode of a low-mode-volume photonic-crystal nanocavity with a bowtie nanoantenna's plasmonic resonance. The resulting enormous enhancement of light intensity of about $1.1{\times}10^7$ in the gap region of the bowtie nanoantenna, due to the effective optical-resonance combination, is realized by subtle optimization of the nanocavity's optical characteristics. This coupled structure holds great promise for many applications relying on strong confinement and enhancement of optical field in nanoscale volumes, including antennas (communication and information), optical trapping and manipulation, sensors, data storage, nonlinear optics, and lasers.

• Proceedings of the KIEE Conference
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• 1993.11a
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• pp.246-248
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• 1993

We investigated the responses of six types of lipid-coated AT-cut quartz crystal resonators to chemical vapour sensors. The responses of quartz crystal at 9 MHz coated with phosphatidylglycerol (PG), phosphatidylinositol(PI), phosphatidylethanolamine(PE), phosphatidylserine(PS), and lipid A(LA) were obtained for amyl acetate, acetoin, menthane and other organic gases which showed different affinities for each lipid. The identification of odorants depending on the species of lipid used for coating is discussed in terms of the normalized resonant frequency shift pattern.

• Journal of Sensor Science and Technology
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• v.21 no.3
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• pp.204-210
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• 2012

In this paper, signal detection and control circuits for hemispherical resonator gyroscope(HRG) are designed, simulated and tested. HRG is one of the coriolis vibratory gyroscope(CVG) which has very stable quartz hemispherical resonator and shows very precise performance. HRG signals are usually modulated at the several kHz of resonant frequency. So the general control scheme cannot be applied directly because general control schemes mainly focused at low frequency range. Using demodulated and modulated PI control scheme with the signal detection which is presented in this paper, performance of manufactured HRG has tested.

• Journal of the Optical Society of Korea
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• v.19 no.6
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• pp.673-678
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• 2015

Terahertz dual-band frequency selective surface filters made by perforating two different rectangular holes in molybdenum have been designed, fabricated and measured. Physical mechanisms of the dual-band resonant responses are clarified by three differently configured filters and the electric field distribution diagrams. The design process is straightforward and simple according to the physical concept and some formulas. Due to the weak coupling between the two neighboring rectangle holes with different sizes in the unit cell, good dual-band frequency selectivity performance can be easily achieved both in the lower and higher bands by tuning dimensions of the two rectangular holes. Three samples are fabricated, and their dual-band characteristics have been demonstrated by a THz time-domain spectroscopy system. Different from most commonly used metal-dielectric structure or metal-dielectric-metal sandwiched filters, the designed dual-band filters have advantages of easy fabrication and low cost, the encouraging results afforded by these filters could find their applications in dual-band sensors, THz communication systems and other emerging THz technologies.

• Journal of Sensor Science and Technology
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• v.20 no.4
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• pp.238-242
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• 2011

This paper describes the fabrication and characteristics of a low frequency vibration driven electromagnetic energy harvester. The fabricated generator consists of a permanent magnet of NdFeB, a FR-4 planar spring and a Copper cylinder type coil. ANSYS modal analysis was used to determine the resonant frequency for the generator. The implemented generator is capable of producing up to 550 mV peak-to-peak under 7 Hz frequency, which has a maximum power of $95.5\;{\mu}W$ with load resistance of $580\;{\Omega}$. This device is shown to generate sufficient power at different resonating modes, and the experimental and simulated results are discussed and composed.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.8
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• pp.1412-1415
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• 2008

A glucose biosensor using a microdisk resonator in polymeric waveguides was developed by observing either the shift in the resonant wavelength or the variation in the optical power. The deformation in the transfer curve of the vertically coupled resonator sensor resulting from the variation in the disk-to-ring coupling, which was incurred by the application of the target analyze, was suppressed. And the refractive index of the polymeric waveguide was devised to closely follow that of the analyze itself for enhancing the sensitivity of the sensor. The sensitivity and measurement range were observed to be respectively 0.14 pm/(mg/dL) and 1500 mg/dL (theoretically up to 4700 mg/dL, for the wavelength shift method and 0.04 dB/(mg/dU and 140 mg/dL the power variation scheme.