• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.3
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• pp.594-599
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• 2011

A SAW strain sensor based on Shear Horizontal wave with an 92 MHz central frequency was developed. It consists of SAW sensor, PCB substrate and bonding material (Loctite 401). External force applied to PCB substrate bonded to a piezoelectric substrate induces strain at the substrate surface, which causes changes in the elastic constant and density of the substrate and hence the propagation velocity of the SAW. The change in the velocity of the SAW result in a frequency shift of the sensor and by measuring a frequency shift, we can extract the strain induced by the external force. The $41^{\circ}$ YX $LiNbO_3$ was used because it has a Leaky shear horizontal(SH) wave propagation mode and a high electromechanical coupling coefficient ($K^2$=17.2%). And to compare with Rayleigh wave mode, $128^{\circ}$ YX $LiNbO_3$ was used. And to make a stable and low insert loss, Split IDT structure was used. The obtained sensitivity and linearity of the SAW strain sensor in the case of Split IDT were measured to be 17.2 kHz / % and 0.99, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.11a
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• pp.56-59
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• 1997

SAW filters of transversal type were fabricated on some piezoelectric substrates of the LN 128$^{\circ}$ Y-X, LN 64$^{\circ}$Y-X, Quartz ST-cut wafers through the simulation in which the number o: IDT and window function were changed for the required frequency, and the mask making. Their IDT spacing and width were 3 ${\mu}{\textrm}{m}$, chip size was 4.462 $\times$ 2.086 mm$^2$, and they had double electrode transversal type IDTs. In addition to pure Al electrode devices, Ti thin films having the different thicknesses was introduced between the Al electrode and the substrate for improving the power resistance strength. They had 11-12 dB insertion losses similar to those of pure Al electrode SAW filters in case of LN 128$^{\circ}$ Y-X, LN 64$^{\circ}$ Y-X, meaning that Ti thin film was not detrimental to the insertion loss and general frequency properties. The filters had the center frequencies 162MHz for LN 128$^{\circ}$ Y-X, 186MHz for 64$^{\circ}$ Y-X, and 131MHz for Quartz ST-cut substrates.

• Journal of Korean Society of Rural Planning
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• v.26 no.3
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• pp.115-126
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• 2020

This study designed an extended technology acceptance model incorporating and combining TPB, TAM, UTAUT, and IDT, which are known to be useful in explaining technology acceptance intention, to analyze antecedents affecting smart farm acceptance intention from the perspective of policy handlers. In the model of this study, nine independent variables were set, including subjective norm, perceived behavioral control, attitude, perceived usefulness, performance expectation, effort expectation, social impact, promotion condition, and fitness. The effect of these variables on farm acceptance intention was analyzed. The study found that four factors, including perceived behavioral control, perceived usefulness, social impact, and fitness, had positive effects on the acceptance intention of smart farms. Of these, perceived usefulness had the highest impact. In conclusion, all the TPB, TAM, UTAUT, and IDT applied to the research hypothesis to explain the smart farm acceptance intention included on or more variables with significant effects. In other words, these theories were evaluated as useful to explain the acceptance intention of smart farms.

• Advances in concrete construction
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• v.10 no.6
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• pp.489-498
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• 2020

This paper investigates mechanical properties of roller compacted concrete (RCC) involving reclaimed asphalt pavement (RAP). In this way, a set of 276 cylindrical RCC specimens were prepared with different RAP sizes (i.e., fine, coarse & total) at various ratios (i.e., 10%, 20%, and 40%). Results reveal that incorporation of RAP decreases unconfined compressive strength (UCS), modulus of elasticity (E), and indirect tensile (IDT) strength of RCC. For each RAP size, a regression model was used to maximize RAP content while satisfying the UCS lower limit (27.6 Mpa) mentioned by ACI as a minimum requirement for RCC used in pavement construction. Moreover, UCS of RAP incorporated mixes, dissimilar to that of control mixes, was found to be sensitive and insensitive to the testing temperature and curing time after 7 days, respectively. The results also demonstrate that the higher amounts of RAP, the more flexibility in RCC is. This issue was also proved by the results of modulus of elasticity test. In addition, the toughness index (TI) shows that increase in RAP content leads to up to 43% increase in energy absorbance capacity of RCC.

• Journal of the Korean Society for Nondestructive Testing
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• v.33 no.1
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• pp.54-62
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• 2013

In this study, a wireless and non-power SAW (surface acoustic wave) temperature sensor was developed. The single inter-digital transducer (IDT) of SAW temperature sensor of which resonance frequency is 434 MHz was fabricated on $128^{\circ}$ rot-X $LiNbO_3$ piezoelectric substrate by semiconductor processing technology. To find optimal acoustic reflector for SAW temperature sensor, various kinds of acoustic reflectors were fabricated and their reflection characteristics were analyzed. The IDT type acoustic reflector showed better reflection characteristic than other reflectors. The wireless temperature sensing system consisting of SAW temperature sensor with dipole antenna and a microprocessor based control circuit with dipole antenna for transmitting signal to activate the SAW temperature sensor and receiving the signal from SAW temperature sensor was developed. The result with wireless SAW temperature sensing system showed that the frequency of SAW temperature sensor was linearly decreased with the increase of temperature in the range of 40 to $80^{\circ}C$ and the developed wireless SAW temperature sensing system showed the excellent performance with the coefficient of determination of 0.99.

• Proceedings of the Korea Association of Information Systems Conference
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• 2004.05a
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• pp.304-315
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• 2004

본 연구는 인터넷 환경 하에서 Davis의 기술수용모델(TAM)을 확장한 것이다. 본래의 TAM 모델에서는 인지된 사용용이성(perceived ease of use) 및 인지된 사용편이성(perceived usefulness)이 시스템 사용을 설명할 때 가장 중요한 요인이라고 제안하고 있다. 그러나 TAM 모델은 실제 시스템 사용의 약 $40\%$만 설명하고 있어 이 모델의 확장이 필요한 편이다. 본 연구에서는 기존의 TAM 모델에, Flow 이론에서 언급된 "인지된 즐거움 (perceived enjoyment)" 및 혁신확산이론(IDT)에서 언급된 "일치성(compatibility)"을 추가하여 TAM 모델을 확장하여 사용하였다. 본 연구자가 근무하는 대학의 대학포탈(university portals) 웹사이트를 사용하여 이 모델을 평가하였다.

• The Journal of the Korea Contents Association
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• v.15 no.7
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• pp.128-137
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• 2015

Going through rapid changes, the field of information technology (IT) has launched many innovative products. Some of those products have spread, forming a stable market, whereas others have disappeared. The purpose of the study is to purpose a theoretical model to show changes in the importance of competition factors over the three stages. Our study applied the innovation adoption stage model of the Innovation Diffusion Theory (IDT) to the industry life cycle of the Industry Life Cycle (ILC) Theory resulting in three stage of introduction, growth, and maturity, and defined a model of market characteristics according to time. By using the model, we analyzed the case of notebook computers and tablet and checked the fitness of the model. Results show that five competition factors worked differently according to time. In the introduction stage, relative functionality and relative playfulness are important competition factors. In the growth stage, compatibility is added to those two factors. In the last maturity stage, compatibility, complexity, and cost level are important competition factors.

• Applied Chemistry for Engineering
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• v.10 no.5
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• pp.701-706
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• 1999

The effect of siloxane oligomer content on thermal stability and internal stress of DGEBA epoxy resin was investigated. Siloxane-epoxy polymers having terminal epoxy group were prepared by reaction of siloxane-DDM prepolymer with DGEBA epoxy resin. Thermal stability was studied in terms of the initial decomposition temperature(IDT), temperature of maximum rate of weight loss($T_{max}$), integral procedural decomposition temperature(IPDT), and decomposition activation energy($E_t$) using TGA data. The thermal stability increased with increasing the siloxane oligomer content and showed a maximum value in the case of 5 wt% siloxane oligomer content in the blend system. While, the coefficient of thermal expansion(${\alpha}_r$) and the flexural modulus($E_r$) allowed us to study internal stress of the blend system. As the content of siloxane oligomer increases, the internal stress systematically decreases as decreasing both ${\alpha}_r$ and $E_r$.

• The Journal of the Acoustical Society of Korea
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• v.21 no.1
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• pp.47-55
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• 2002

This paper proposes a new improved lumped element equivalent circuit analysis method to analyze withdrawal weighted SAW resonators of irregular electrode configurations, which enables to calculate the frequency response of withdrawal weighted SAW resonators. This method has led to the derivation of Smith equivalent circuit's y-parameters for a single ground electrode and formulated the resonator's admittance by calculating the total current into an IDT assembly. To illustrate the effectiveness of the technique, this method was applied to the design of a simple ladder filter and the change of the filter performance was investigated in relation to the weighting of the series and parallel resonators, respectively. The results shows that the withdrawal weighted resonator ladder filters provide better performance in their bandwidth and transition characteristics than normal ones. This new equivalent circuit analysis method can also serve as a better tool to design and analyze general SAW resonator filters.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.14 no.5
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• pp.215-221
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• 2014

In this paper, the improved power durability test system and method for an reliability analysis of SAW device is proposed and the failure mechanism through failure analysis is analyzed. As a result of the failure analysis using microscope, SEM and EDX, the failure mechanism of the SAW device is electromigration due to joule heating under high current density and high temperature condition. The electromigration makes voids and hillocks in the IDT electrode and the voids and hillocks can lead to short circuit and open circuit faults, respectively, increasing the insertion loss of an SAW filter. The accelerated life testing of the SAW filter for 450MHz CDMA application using the proposed power durability test system and method is carried out. $B_{10}$ lifetime of the SAW filter using Eyring model and Weibull distribution is estimated as about 98,500 hours.