• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.11a
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• pp.109-112
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• 1998

SAW filters of transversal type were fabricated on some piezoelectric substrate of the LN 128 $^{\circ}$ Y-X waters through the simulation in which the number of IDT and window function were changed for the required frequency, and the mask making. Their IDT spacing and width were 1.63$\mu\textrm{m}$, 1.239$\mu\textrm{m}$, respectively. Titanium thin films having different thicknesses were introduced between the Al electrode and the substrate for improving the power resistance strength due to its high temperature durability and good adhesion characteristics. All of specimens showed similar insertion loss results, which means the possibility of introducing the Ti layer though it is known to have a higher resistivity leading to a worse insertion loss result. Ti inserted specimens had a better power durability than that of pure Al electrode though their thickness had no effect on the performance.

• Journal of Sensor Science and Technology
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• v.9 no.4
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• pp.327-333
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• 2000

Transversal SAW(Surface Acoustic Wave) filters of 340MHz were fabricated on piezoelectric substrates of the LN $128^{\circ}$ Y-X wafers. Both of spacing and width of IDT were $1.435{\mu}m$. For improving the power durability characteristics, titanium layer was inserted between aluminum electrode and piezoelectric substrate since it has high density, low thermal expansion coefficient, and good adhesive properties. Power durability was evaluated with respect to the thickness of inserted titanium layer and the temperature of heat treatment. Power durability is improved with increasing the thickness of the inserted titanium layer. Moreover, it is remarkably improved by heat treatment at the temperature of $300^{\circ}C$.

• Journal of Biosystems Engineering
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• v.29 no.4
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• pp.317-322
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• 2004

This study was conducted to evaluate the feasibility of identifying freshness of beef using a surface acoustic wave (SAW) sensor based electronic nose. The beef was stored at 5$^{\circ}C$ and aroma was measured with the passage of time. Chromatographic analysis of the odor showed that number of volatile components and their amounts were rapidly increased after 19 days of storage. Classifying beefs according to their storage days was possible using principle component analysis (PCA). Classifying beefs processed from four different origins was also possible with PCA analysis of odor. This study shows that electronic nose can be applied to beef freshness evaluation and classification of its origin.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.05a
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• pp.343-345
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• 2015

Currently, SAW Device has been used as a frequency filter using the property of passing only a desired frequency with a narrow bandwidth. However, the areas of activity in various fields since the permanent advantages can be widened by using a non-powered. These sensor tags using SAW Device has been done, but a lot of research, the development of the state still insufficient for Reader Platform. How to read the value of the ID Tag Using SAW Device has a time domain sampling (TDS) method and a frequency domain sampling (FDS) method. The purpose of the paper, we use the FDS method that requires high-speed processing with a relatively slow sampling rate does not require high-speed sampling. Reader Platform was the way to detect ID through PC as FDS way, but It is based on the Cortex-A9 processor and it works a low price, compact and real-time Reader Platform.

• Journal of Sensor Science and Technology
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• v.21 no.6
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• pp.408-412
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• 2012

An in-line dispersive delay line (DDL) demands low and controllable reflectivity of the reflectors, especially if the surface acoustic wave (SAW) propagates all the way along the reflecting structure. The metal reflectors are usually too strong and introduce too much attenuation in such a device. The proposed solution of this problem is to spatially separate the acoustic channels for different frequencies with the help of Fan-shaped Transducers (FIDT) and to use narrow open metal reflectors to reduce reflectivity. Special arrangement of FIDT is performed to use 180-deg. reflection of the SAW. Narrow open metal strips with a metallisation ratio of the order of 20% are used as reflectors with small and controllable reflectivity. Reflectivity of such strips is estimated both theoretically and experimentally. Experimental performance of the proposed DDL is presented.

• Proceedings of the KWS Conference
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• 1999.10a
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• pp.47-50
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• 1999

The term adaptive control is often used to describe recent advances in welding process control but strictly this only applies to system which are able to cope with dynamic changes in system performance. In welding applications, the term adaptive control may not imply the conventional control theory definition but may be used in the more descriptive sense to explain the need for the process to adapt to the changing welding conditions. This paper proposed a methodology for obtaining a good bead appearance based on multi-torches welding system with the vision system in SAW. The methodologies for adaptive filling control used the welding current/voltage, arc voltage/welding current/wire feed speed combination and welding speed by using the vision sensor. It was shown that the algorithm for the welding current/voltage combination and welding speed revealed the sound weld bead appearance compared with that of the voltage/current combination.

• Journal of the Microelectronics and Packaging Society
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• v.16 no.1
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• pp.13-19
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• 2009

A 440MHz wireless and passive surface acoustic wave (SAW) based chemical sensor was developed on a $41^{\circ}YX\;LiNbO_3$ piezoelectric substrate for simultaneous measurement of $CO_2$ gas and relative humidity (RH) using a reflective delay line pattern as the sensor element. The reflective delay line is composed of an interdigital transducer (IDT) and several shorted grating reflectors. A Teflon AF 2400 and a hydrophilic $SiO_2$ layer were used as $CO_2$ and water vapor sensitive films. The coupling of mode (COM) modeling was conducted to determine optimal device parameters prior to fabrication. According to simulation results, the device was fabricated and then wirelessly measured using the network analyzer. The measured reflective coefficient $S_{11}$ in the time domain showed high signal/noise (S/N) ratio, small signal attenuation, and few spurious peaks. In the $CO_2$ and humidity testing, high sensitivity ($2^{\circ}/ppm$ for $CO_2$ detection and $7.45^{\circ}/%$RH for humidity sensing), good linearity and repeatability were observed in the $CO_2$ concentration ranges of $75{\sim}375ppm$ and humidity levels of $20{\sim}80%$RH. Temperature and humidity compensations were also investigated during the sensitivity evaluation process.

• Journal of Sensor Science and Technology
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• v.10 no.2
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• pp.142-147
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• 2001

Using transmission-line equivalent circuit based on cross-field model for an interdigital acoustic wave transducer, an efficient simulation technique of SAW filters by SPICE is proposed. Propagation of surface acoustic wave is modeled as transmission line so that frequency-dependent circuit elements are not needed in the equivalent circuit of an interdigital transducer. Because the equivalent circuits for frequency-dependent circuit elements are not derived approximately, and a small number of circuit elements are used in the equivalent circuit for filters, simulation time is much reduced. The utility of the proposed technique is demonstrated through simulation for the characteristics of SAW filters such as insertion loss, input admittance, passband ripple, and harmonic frequency response.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.2
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• pp.390-396
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• 2010

An 80MHz surface acoustic wave (SAW)-based gyroscope utilizing a progressive wave was developed on a piezoelectric substrate. The developed sensor consists of two SAW oscillators in which one is used for sensing element and has metallic dots in the cavity between input and output IDTs. The other is used for a reference element. Coupling of mode (COM) modeling was conducted to determine the optimal device parameters prior to fabrication. According to the simulation results, the device was fabricated and then measured on a rate table. When the device was subjected to an angular rotation, oscillation frequency differences between the two oscillators were observed because of the Coriolis force acting on the metallic dots. Depending on the angular rate, the difference of the oscillation frequency was modulated. The obtained sensitivity was approximately 52.35 Hz/deg.s within the angular rate range of 0~1000 deg/s. The performances of devices with three IDT structures for two kinds of piezoelectric substrates were characterized. Good thermal stability was also observed during the evaluation process.

• Korean journal of food and cookery science
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• v.22 no.3 s.93
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• pp.299-306
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• 2006

The numerous varieties of coffee beans contain a wide range prices and qualities. While the varieties of green coffee beans can generally be distinguished by their appearance, this visual criterion is impossible after the roasting process. Therefore, we need to develop a classification method or device. In this study, the potential of a new type of electronic nose, fast gas chromatography based on a surface acoustic wave sensor(SAW), was evaluated for the classification of origins and blended commercial brands in roasted coffee beans. Eight blended commercial brands and the origins of four similarly roasted ground coffee beans(with no significant difference of color) were rapidly(90 sec/sample) classified. The reproductive results were easily understandable over the aroma image pattern by $VaporPrint^{TM}$. In conclusion, GC-SAW electronic nose can be applied to the classification of origins and commercial brands in roasted ground coffee beans and to e evaluation of the similarities and differences of volatile pattern between samples.