• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.11
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• pp.1034-1046
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• 2013

In this paper, a design of a GaN HEMT power amplifier using output matching circuit with arbitrary harmonic impedances is presented. The adopted GaN HEMT device, TGF2023-02 of TriQuint Semiconductor, was packaged in commercial package. The optimal impedances of the GaN HEMT package are extracted from load-pull simulation at package input and output reference planes. The targets of load-pull simulation are the highest output power at fundamental frequency and the highest efficiency at $2^{nd}$ and $3^{rd}$ harmonic frequencies. Because of fixture in the package, the extracted impedances shows arbitrary harmonic impedances. In order to match the optimal impedances, output matchin circuit which has 4 transmission lines is presented. Characteristic impedances and electrical lengths of the transmission lines are mathmatically calculated. The power amplfiier with $54.6{\times}40mm^2$ shows the output power of 8 W at the fundamental frequency of 2.5 GHz, the efficiency above 55 %, and harmonic suppression of above 35 dBc at the $2^{nd}$ and the $3^{rd}$ harmonics.

• Journal of Sensor Science and Technology
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• v.6 no.1
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• pp.6-15
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• 1997

This paper presents the multi-objective optimal design of thermopile sensor having beam or membrane structure. The thermopile sensor is composed of $Si_{3}N_{4}/SiO_{2}$ dielectric membrane, Al-polysilicon thermocouples and $RuO_{2}$ thin film for black body. The sensing method is based on the Seebeck effect which is originated from the temperature difference of the two positions, black body and silicon rim. The objective functions of the presented design are sensitivity, detectivity and thermal time constant. The modelling of the sensor is proposed including the package. The multi-objective optimization technique is applied to the design of the sensor not only inspecting the modelling equation but also simulating mathematical programming method. Especially, fuzzy optimization technique is adapted to get the optimal solution which enables the designer to reach the more practical solution. The design constraint of the voltage output originated from the change of the environmental temperature is included for practical use.

• Journal of the Korean association of regional geographers
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• v.11 no.4
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• pp.497-510
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• 2005

The purpose of this study was to examine the image similarity, preference, and the attribute recognition using multidimensional scaling. The analyses were carried out by 5 spa destinations located in Choongchung area. The results were as followings: first, considering the image similarity, the image of Suanbo & Onyang and Dogo & Asan were similar except for the Yusung. Second, considering the attribute recognition, Yusung had a stronger attribute reflecting spa tradition when compared to other competitive spa destinations. Onyang showed a strong attribute of facilities. Dogo had a stronger point about use cost. Suanbo had relatively strong attributes in terms of facilities, customer service, and accessability. However, the water quality of spa destination and activities were not reflected in attribute recognition because these two attributes was farthest from the spa destination. Third, considering the preference of selecting spa destinations, package tourists had a strong preference about Yusung, individual tourists, family, incentive tourists prefer Suanbo, followed by Dogo and Yusung. Group tourists had a strong preference about Dogo.