• Proceedings of the KIEE Conference
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• 2002.11c
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• pp.329-332
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• 2002

Recently, most machineries have been small size and mobile type. Then the motors used in this field are developed in micro size such as about 2mm in diameter. The structure of this motor is similar to a general brushless DC motor but because of small sige there is no position sensor such as hall sensor. In this paper, we propose synchronous driving and control method for micro brushless DC motor without position sensor. We design and manufacture this controller and perform experiment to show the effectiveness of the proposed method.

• Proceedings of the KIEE Conference
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• 1994.07b
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• pp.1339-1341
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• 1994

In this paper, the flow velocity/mass sensor which is based on the principle of CCT(Constant Chip Temperature) and its digital operating circuit and system have been developed and tested. The experimental result for flow velocity shows that the sensitivity is $644.01{\mu}W^2/[m/sec]$ for air, and there is nearly no hysteresis for full measured range of velocity. Response tine is between 1 second and 8 seconds for low and large velocity variation, respectively.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.1444-1446
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• 2005

Recently most machineries have been small size and mobile type. And human body insertion type endoscope and micro robot technology has been developed. Then the motors used in this field are developed in micro size such as about 2mm in diameter. The structure of this motor is similar to a general brushless DC(BLDC) motor but because of small size there is no position sensor such as hall sensor. In this paper, a design and fabrication result of an ultra-small brushless DC motor is presented. This motor is designed to 3-phase coreless winding and operated with sensor-less type driver. Test results confirmed the feasibility of the proposed motor drive system design.

• Journal of Sensor Science and Technology
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• v.23 no.3
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• pp.211-215
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• 2014

The Pt-, Ni- and Cr-decorated tubular $SnO_2$ nanofibers for gas sensors were prepared by the electrospinning of polyvinylpyrrolidone (PVP) nanofibers containing Pt, Ni, and Cr precursors, the sputtering of $SnO_2$ on the electrospun PVP nanofibers, and the removal of sacrificial PVP parts by heat treatment at $600^{\circ}C$ for 2 h. Pt-decorated tubular $SnO_2$ nanofibers showed high response ($R_a/R_g=210.5$, $R_g$: resistance in gas, $R_a$: resistance in air) to 5 ppm $C_2H_5OH$ at $350^{\circ}C$ with negligible cross-responses to other interference gases (5 ppm trimethylamine, $NH_3$, HCHO, p-xylene, toluene and benzene). Cr-decorated tubular $SnO_2$nanofibers showed the selective detection of p-xylene at $400^{\circ}C$. In contrast, no significant selectivity to a specific gas was found in Ni-decorated tubular $SnO_2$ nanofibers. The selective and sensitive detection of gases using Pt-decorated and Cr-decorated tubular $SnO_2$ nanofibers were discussed in relation to the catalytic promotion of gas sensing reaction.

• Bulletin of the Korean Chemical Society
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• v.33 no.6
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• pp.1851-1855
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• 2012

The $NO_2$ gas sensing properties of multiple-networked, Pt-loaded $TeO_2$ nanorod sensors were examined. Scanning electron microscopy revealed nanowires with diameters of 50-100 nm and lengths of a few micrometers. Transmission electron microscopy and X-ray diffraction showed that the nanrods were tetragonal-structured, single crystal $TeO_2$. The Pt-loaded $TeO_2$ nanorod sensors exhibited sensitivities of 11.00, 10.26, 11.23 and 11.97% at $NO_2$ concentrations of 10, 50, 100 and 200 ppm, respectively, at $300^{\circ}C$. These sensitivities were more than 10 times higher than those of bare-$TeO_2$ nanorod sensors. The response times of the sensors were 310, 260, 270 and 230 sec at $NO_2$ concentrations of 10, 50, 100 and 200 ppm, respectively. The recovery times of the Pt-loaded $TeO_2$ nanorods were 390, 330, 335, and 330 sec at $NO_2$ concentrations of 10, 50, 100 and 200 ppm, respectively. The origin of the enhanced sensing properties of the $TeO_2$ nanorods by Pt loading is discussed.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.3
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• pp.215-218
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• 2011

A novel design of gas sensor using Ga-doped ZnO (GZO) thin films which are deposited on low temperature co-fired ceramic (LTCC) substrates is presented. The LTCC substrates with thickness of 400 ${\mu}m$ are fabricated by laminating 12 green tapes which consist of alumina and glass particle in an organic binder. The GZO thin films with different thickness are deposited on LTCC substrates, by RF magnetron sputtering method. The microstructure and sensing properties of GZO gas sensing films are analyzed as a function of the film thickness. The films are well crystallized in the hexagonal (wurzite) structure with increasing thickness. The maximum sensitivity of 3.49 is obtained at 100 nm film thickness and the fastest 90% response time of 27.2 sec is obtained at 50 nm film thickness for the operating temperature of $400^{\circ}C$ to the $NO_2$ gas.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.8
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• pp.843-850
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• 2016

This paper introduces a novel modulation scheme for vehicular communication in taking advantage of existing LED lights available on a car. Our proposed 2-Phase Shift Keying (2-PSK) is a spatial modulation approach in which a pair of LED light sources in a car (either rear LEDs or front LEDs) is used as a transmitter. A typical camera (i.e. low frame rate at no greater than 30fps) that either a global shutter camera or a rolling shutter camera can be used as a receiver. The modulation scheme is a part of our Image Sensor Communication proposal submitted to IEEE 802.15.7r1 (TG7r1) recently. Also, a neural network approach is applied to improve the performance of LEDs detection and decoding under the noisy situation. Later, some analysis and experiment results are presented to indicate the performance of our system

• Journal of Powder Materials
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• v.13 no.3 s.56
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• pp.192-198
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• 2006

The nanostructured cerium oxide powders were synthesized by spray thermal decomposition process for the use as the raw materials of resistive oxygen sensor. The synthesis routes consisted of 1) spray drying of water based organic solution made from cerium nitrate hydrate ($Ce(NO_3){_3}6H_2O$) and 2) heat treatment of spray dried precursor powders at $400^{\circ}C$ in air atmosphere to remove the volatile components and identically to oxidize the cerium component. The produced powders have shown the loose structure agglomerated with extremely fine cerium oxide particles with about 15 nm and very high specific surface area ($110m^2/g$). The oxygen sensitivity, n ($Log{\propto}Log (P_{O2}/P^o)^{-n}$ and the response time, $t_{90}$ measured at $600^{\circ}C$ in the sample sintered at $1000^{\circ}C$, were about 0.25 and 3 seconds, respectively, which had much higher performances than those known in micron or $100{\sim}200nm$ sized sensors.

• Korean Journal of Digital Imaging in Medicine
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• v.11 no.2
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• pp.109-114
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• 2009

Carried out an experiment for quantitative evaluation about intraoral sensor among oral dental imaging equipments in PACS environment. For evaluation, testing environment & evaluation criteria are established that refer to the 'IEC 62220-1-2' and experimented with set up the standard radiation penetration that correspond with RQA-3(IEC 61267). Results of experiments using the image J, derived the ESF(edge spread function), LSF (line spread function) and calculated the MTF(modulation transfer function) finally. As a result, the MTF that 0.1, 0.2sec are 10% about 10 lp/mm and 0.32 sec is the 10% about 9 lp/mm in level represents the value of the MTF. Change of scan condition in dental environmental, according to the MTF value taken note that no changes can be seen enough. However, the dimensions of each other size $1(1200{\times}1600)$, size $2(1440{\times}1920)$ intraoral sensors for 3 lp/mm, respectively 40%, 90% of the note might have been the difference between the value of MTF, in accordance with standard sensors might note differences could be observed.

• Journal of Sensor Science and Technology
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• v.23 no.4
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• pp.266-271
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• 2014

Chemical sensors are used in various industrial facilities such high-risk and prevent the leakage of substances, important in life and environmental protection and the safe use of industry, used for management. In particular, high-temperature environments such as power generation equipment of the rotating part due to leakage generated by the various oil, power plants Shut Down, fire, work environment (exposure to various chemical solution and gas leak) and various water, air and soil pollution causes. Thus, over the long term through various channels such as crops and groundwater contamination caused by the slow, serious adverse effect on the ecosystem. In this paper, synthetic lube oil and high pressure hydraulic fluid leakage and immediately detect a new Printed Electronic implementation of technology-based film-type sensors, and its performance test. Thus, industrial accidents and environmental pollution and for early detection of problems, large accidents can be prevented. Experimental results of the synthetic lube oil and high pressure hydraulic fluid solution after the contact time depending on the experiment and the oil solution of the sensor material of the conductive porous PE resistance value by a chemical reaction could be confirmed that rapid increase. Also implemented in the film-type oil sensor electrical resistance change over time of the reaction rate and the synthetic lube oil is about 2 minutes or less, the high pressure hydraulic fluid is less than about 1 minute was. Therefore, more high-pressure hydraulic fluid such as a low volatility synthetic lube oils are the resistance change and the reaction rate was confirmed to be the slowest.