• Journal of Advanced Navigation Technology
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• v.6 no.1
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• pp.52-62
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• 2002

Electrical characteristics of two types of 20 GHz Push-Push GaAs MESFET dielectric resonator oscillators having Wilkinson and T-junction power combiners for the output stage have been investigated. The Push-Push oscillator for suppressing fundamental frequency 10 GHz and enhancing 20 GHz has been designed and realized in microstrip configuration on 20 mil thick RT-Duroid(${\varepsilon}_r$=2.52) teflon substrate. Two different types of power combiners, T-junction and Wilkinson, have been considered. Whenever one type of the combiners has been adopted for the output circuit, output power, phase noise and fundamental frequency suppression characteristics of the oscillator have been measured. When the Wilkinson power combiner was used, a maximum output power of 5.67 dBm, a phase noise of -105.5 dBc/Hz at an offset frequency of 100 kHz and a fundamental frequency suppression of -29.33 dBc have been measured. When the T-junction power combiner was used, a maximum output power of -1.17 dBm, a phase noise of -102.2 dBc/Hz at an offset frequency of 100 kHz and a fundamental frequency suppression of -17.84 dBc have been measured.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.11
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• pp.1131-1139
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• 2009

Combustion Instabilities are caused by a coupling between acoustic waves and unsteady heat release. They can be eliminated using passive controller such as a Helmholtz resonator. But, Helmholtz resonator is normally only effective over a narrow frequency range. In this work, Helmholtz resonator is applied for reducing the combustion oscillations and we vary the Helmholtz resonator volume using piston in oder to tune in the wide range of operating conditions. As the result, it is found that the dominant combustion oscillations can be largely reduced by optimizing the size of resonator volume. And, interesting relation for phase difference of dynamic pressure both combustor and the helmholtz resonator are presented in this paper. Also, we investigate semi-active control using Helmholtz equation and phase difference.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.7
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• pp.613-624
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• 2002

Electrical characteristics of two types of 20 GHz Push-Push GaAs MESFET dielectric resonator oscillators having Wilkinson and T-junction power combiners for the output stage have been investigated and compared. So we have explained that the output power and phase noise properties of the Push-push FET DRO are depending on return loss and isolation characteristics of power combiner at the fundamental and the second harmonic frequencies. A Push-push oscillator for suppressing the fundamental frequency of 10 GHz and enhancing the second harmonic of 20 GHz has been designed and fabricated in microstrip configuration on 20 mil thick RT-Duroid($\varepsilon$$_{r}$ = 2.52) Teflon substrate. Return loss and isolation characteristics of T-junction and Wilkinson have been measured at the fundamental frequency of 10.2 GHz and the second harmonic frequency of 20.5 GHz. At the fundamental frequency, -12 dB return loss and -3.7 dB isolation have been measured for the T-junction power combiner, and -14 dB return loss and -11 dB isolation fur the Wilkinson power combiner. At the second harmonic frequency, -10 dB return loss and -7.5 dB isolation have been obtained for the T-junction power combiner, and -23 dB return loss and -22 dB isolation for the Wilkinson power combiner. As a result, we have confirmed that the oscillator based on the Wilkinson power combiner with better retrun loss and isolation characteristics produces more output power and better phase noise characteristics..

• Journal of the Computational Structural Engineering Institute of Korea
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• v.37 no.2
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• pp.111-118
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• 2024

An in-structure response spectrum (ISRS) is required to evaluate the seismic performance of a nuclear power plant (NPP). However, when a new ISRS is required because of the change in the unique spectrum of an NPP site, considerable costs such as seismic response re-analyses are incurred. This study provides several approaches to generate approximate methods for ISRS scaling, which do not require seismic response re-analyses. The ISRSs derived using these approaches are compared to the original ISRS. The effect of the ISRS of the approximate method on the seismic response and seismic performance of one of the main systems of an NPP is analyzed. The ISRS scaling approximation methods presented in this study produce ISRSs that are relatively similar at low frequencies; however, the similarity decreases at high frequencies. The effect of the ISRS scaling approximate method on the calculation accuracy of the seismic response/seismic performance of the system is determined according to the degree of similarity in the calculation of the system's essential mode responses for the method.