• 한국재료학회지
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• 제33권5호
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• pp.195-204
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• 2023

Micro-electronic gas sensor devices were developed for the detection of carbon monoxide (CO), nitrogen oxides (NO_x), ammonia (NH₃), and formaldehyde (HCHO), as well as binary mixed-gas systems. Four gas sensing materials for different target gases, Pd-SnO₂ for CO, In₂O₃ for NO_x, Ru-WO₃ for NH₃, and SnO₂-ZnO for HCHO, were synthesized using a sol-gel method, and sensor devices were then fabricated using a micro sensor platform. The gas sensing behavior and sensor response to the gas mixture were examined for six mixed gas systems using the experimental data in MEMS gas sensor arrays in sole gases and their mixtures. The gas sensing behavior with the mixed gas system suggests that specific adsorption and selective activation of the adsorption sites might occur in gas mixtures, and allow selectivity for the adsorption of a particular gas. The careful pattern recognition of sensing data obtained by the sensor array made it possible to distinguish a gas species from a gas mixture and to measure its concentration.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.66-66
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• 2011

Anodic titanium dioxide (TiO2) nanotubes are very attractive materials for gas sensors due to its large surface to volume ratios. The most widely known method for fabrication of TiO2 nanotubes is anodic oxidation of metallic Ti foil. Since the remaining Ti substrate is a metallic conductor, TiO2 nanotube arrays on Ti are not appropriate for gas sensor applications. Detachment of the TiO2 nanotube arrays from the Ti Substrate or the formation of electrodes onto the TiO2 nanotube arrays have been used to demonstrate gas sensors based on TiO2 nanotubes. But the sensitivity was much lower than those of TiO2 gas sensors based on conventional TiO2 nanoparticle films. In this study, Ti thin films were deposited onto a SiO2/Si substrate by electron beam evaporation. Samples were anodized in ethylene glycol solution and ammonium fluoride (NH4F) with 0.1wt%, 0.2wt%, 0.3wt% and potentials ranging from 30 to 60V respectively. After anodization, the samples were annealed at $600^{\circ}C$ in air for 1 hours, leading to porous TiO2 films with TiO2 nanotubes. With changing temperature and CO concentration, gas sensor performance of the TiO2 nanotube gas sensors were measured, demonstrating the potential advantages of the porous TiO2 films for gas sensor applications. The details on the fabrication and gas sensing performance of TiO2 nanotube sensors will be presented.

• Smart Structures and Systems
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• 제4권6호
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• pp.727-740
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• 2008

A down hole vertical seismic array is a sequence of instruments installed at various depths in the earth to record the ground motion at multiple points during an earthquake. Numerous studies demonstrate the unique utility of vertical seismic arrays for studying in situ site response and soil behavior. Examples are given of analyses made at two sites to show the value of data from vertical seismic arrays. The sites examined are the Lotung, Taiwan SMART1 array and a new site installed at Jingliao, Taiwan. Details of the installation of the Jingliao array are given. ARX models are theoretically the correct process models for vertical wave propagation in the layered earth, and are used to linearly map deeper sensor input signals to shallower sensor output signals. An example of Event 16 at the Lotung array is given. This same data, when examined in detail with a Bayesian inference model, can also be explained by nonlinear filters yielding commonly accepted soil degradation curves. Results from applying an ARMAX model to data from the Jingliao vertical seismic array are presented. Estimates of inter-transducer soil increment resonant frequency, shear modulus, and damping ratio are presented. The shear modulus varied from 50 to 150 MPa, and damping ratio between 8% and 15%. A new hardware monitoring system - TerraScope - is an affordable 4-D down-hole seismic monitoring system based on independent, microprocessor-controlled sensor Pods. The Pods are nominally 50 mm in diameter, and about 120 mm long. An internal 16-bit micro-controller oversees all aspects of instrumentation, eight programmable gain amplifiers, and local signal storage.

• 한국정밀공학회지
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• 제27권11호
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• pp.30-36
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• 2010

Previous researches show that linearly integrated Hall sensor arrays (LIHaS) can detect cracks in the steel structure fast and effectively This paper proposes an algorithm that estimates the size and shape of cracks for the developed LIHaS. In most nondestructive testing (NDT), just crack existence and location are obtained by processing 1-dimensional data from the sensor that scans the object with relative speed in single direction. The proposed method is composed with two steps. The first step is constructing 2-dimensionally mapped data space by combining the converted position data from the time-based scan data with the position information of sensor arrays those are placed in the vertical direction to the scan direction. The second step is applying designed Laplacian filter and smoothing filter to estimate the size and shape of cracks. The experimental results of express train wheels show that the proposed algorithm is not only more reliable and accurate to detecting cracks but also effective to estimate the size and shape of cracks.

• 센서학회지
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• 제23권2호
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• pp.99-104
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• 2014

Sensor arrays based on chemical sensors produce multidimensional patterns of data that may be used discriminate between different chemicals. For the human observer, visualization of multidimensional data is difficult, since the eye and brain process visual information in two or three dimensions. To devise a simple means of data inspection from the response of sensor arrays, PCA (Principal Component Analysis) or Sammon's nonlinear mapping technique can be applied. The PCA, which is a well-known statistical method and widely used in data analysis, has disadvantages including data distortion and the axes for plotting the dimensionally reduced data have no physical meaning in terms of how different one cluster is from another. In this paper, we have investigated two techniques and proposed a combination technique of PCA and nonlinear Sammom mapping for visualization of multidimensional patterns to two dimensions using data sets from odor sensing system. We conclude the combination technique has shown more advantages comparing with the PCA and Sammon nonlinear technique individually.

• Current Optics and Photonics
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• 제4권5호
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• pp.428-433
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• 2020

Recently, the on-chip autofocus (AF) function has become essential to the CMOS image sensor. An auto-focus usually operates using phase detection of the photocurrent difference from a pair of AF pixels that have focused or defocused. However, the phase-detection method requires a pair of AF pixels for comparison of readout. Therefore, the pixel variation may reduce AF performance. In this paper, we propose a color-selective AF pixel with a plasmonic nanostructure in a 0.9 μ㎡ pixel. The suggested AF pixel requires one pixel for AF function. The plasmonic nanostructure uses metal-insulator-metal (MIM) stack arrays instead of a color filter (CF). The color filters are formed at the subwavelength, and they transmit the specific wavelength of light according to the stack period and incident angles. For the optical analysis of the pixel, a finite-difference time-domain (FDTD) simulation was conducted. The analysis showed that the MIM stack arrays in the pixels perform as an AF pixel. As the primary metric of AF performance, the resulting AF contrasts are 1.8 for the red pixels, 1.6 for green, and 1.5 blue. Based on the simulation results, we confirmed the autofocusing performance of the MIM stack arrays.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1995년도 춘계학술대회 논문집
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• pp.124-128
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• 1995

We have fabricated the vacuum magnetic device with a lateral field emitter arrays constructed on n-Si wafer, and investigated its magnetic characteristics. The device is consited to tip-arrayed emitter. gate and split-anode, The fabricated vacuum magnetic device has showed a good linearity of magnetic field and a high sensitivity compared with the conventional semiconductor magnetic device.

• 전기학회논문지
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• 제58권11호
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• pp.2219-2222
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• 2009

A new touch-sensitive hydrogenated amorphous silicon(a-Si:H) display with embedded optical sensor arrays is presented. The touch-sensitive panel operation was successfully demonstrated on a prototype of 16-in. active-matrix liquid crystal display (AMLCD). The proposed system provides the finger touched point without the real-time image processing of information of the captured images. Due to the simple architecture of the system, we expect the introduction of large-area touch-sensitive display panels.

• Journal of Electrical Engineering and Technology
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• 제11권3호
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• pp.759-768
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• 2016

Direction of arrival (DOA) estimation of multiple sources using sensor arrays has been widely studied in the last few decades, particularly, the spherical harmonic analysis utilizing a spherical array. Both the number of sensors on the aperture and size of the sphere can affect the estimation accuracy dramatically. However, those two factors are conflicted to each other in a single spherical array. In this paper, a multiple spherical arrays structure is proposed to provide an alternative design to the traditional single spherical array for the spherical harmonic decomposition, to obtain better localization performance. The new structure consists of several identical spheres in a given area, and the microphones are placed identically on each sphere. The spherical harmonic analysis algorithm using the new multiple array structure for the problem of multiple acoustic sources localization is presented. Simulation results show that the multiple spherical arrays can provide a more accurate direction of arrival (DOA) estimation for the multiple sources than that of a single spherical array, distinguish several adjacent sources more efficiently, and reduce the number of microphones on each sphere without decreasing its’ estimation accuracy.

• 산업기술연구
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• 제31권B호
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• pp.3-7
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• 2011

This paper addresses a computationally simple adaptive beamforming method to cancel interferences arriving onto a sensor array. In the proposed method, an estimate of the interference subspace is extracted from a submatrix of the sample covariance matrix and an orthonormal basis for the estimated subspace is efficiently found, one basis vector being updated every sample. Its computational burden is just $O(M{\eta})$ in an M-sensor array when ${\eta}$ directional signals are present. The new method does not make any premises of the geometrical structure of arrays, and can be applied to arbitrary arrays.