• Journal of the Korean Ceramic Society
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• v.33 no.12
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• pp.1311-1318
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• 1996

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.05a
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• pp.292-294
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• 1996

Dielectric properties were investigated at Mn doped 0.17($Ba_{0.53}$, $Pb_{0.47}$)0-$0.16Nd_2O_3$-$0.67TiO_2$ system in microwave frequency. It was observed that dielectric constant of 90.1, quality factor of 1320 (at 3.8GHz) and temperature coefficient of resonance frequency 2.3 ppm/$^{\circ}C$ for 0.5wt% Mn doped 0.17($Ba_{0.53}$, $Pb_{0.47}$)0-$0.16Nd_2O_3$-$0.67TiO_2$ system in sintering condition $1290^{\circ}C$/2hr. The quality factor increase due to the compensation effect of Mn ions yp to 0.5wt% and the decrease due to the interface relaxation effect. The temperature coefficient of resonance frequency increases to negative direction with increasing the amounts of Mn.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.6 no.4
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• pp.355-360
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• 2005

The objective of this study is design and structural analysis of 2nd crusher for useless wood. Structural analysis and modal analysis were effected in ANSYS and the structural safety was examined in search of displacement, stress, strain. There are avoid to resonance phenomenon by motor control.

• Journal of the Korea Institute of Military Science and Technology
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• v.17 no.1
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• pp.57-63
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• 2014

In this paper, we have proposed a wide band antenna for manpack SDR(Software Defined Radio). The proposed antenna consists of feeding post, flexible gooseneck and two radiating elements composed of a upper and lower radiators. The upper radiator has a longer electrical length than the lower radiator in order to operate in the lower frequency. Also, the resonant frequency and impedance characteristics of the antenna can be adjusted independently for two radiators. Therefore, the proposed antenna can be achieved wide impedance bandwidth by the combination of two independent resonance modes. To analyze the characteristics of the antenna in the design process is employed the equivalent circuit theory and EM(Electro-Magnetic) simulation. The measurement results show that the proposed antenna have the sufficient wide bandwidth, above -3.4dBi of the gain and fairly good radiation pattern over the wide bandwidth.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.770-774
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• 2003

We propose the re-design method of modal parameters to depress the 2nd resonance peak of the ultra-slim-height optical pick-up actuator. With the addition of tile counter mode near the 2nd resonance frequency, we can achieve the gain margin which is sufficient to meet the system requirement. It would alleviate the burden of the additional filter for a high-speed drive.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.1
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• pp.43-49
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• 2005

Temperature stabilities of resonance frequencies of the substrates are very important in piezoelectric ceramics oscillators and fitters. In this study, it was investigated thermal resisting property of the length-extensional vibration mode of PZT ceramics. The mode can be utilized in fabricating ultra-small 55 kHz IF devices. We fabricated the ceramic specimens with x = 0.51, 0.52, 0.53, 0.54, and 0.55 in the Pb(Zr$\sub$x/Ti$\sub$1-x/)O$_3$ system. And their resonance frequencies were measured before 1st thermal aging, after 1st and 2nd thermal aging. In order to investigate the influence of thermal aging on thermal resisting properties, thermally aged specimens were once mote thermally aged. Before 1st thermal aging, the specimens of the compositions with morphotropic phase, x = 0.53 and rhombohedral phase, x = 0.54 have weak thermal resisting property of resonance frequency, while tetragonal phase, x = 0.51 has robust thermal resisting property of resonance frequency. 1st thermal aging improved thermal resisting property of resonance frequency in all specimens.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.5
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• pp.77-81
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• 2008

Structural components subjected to high frequency vibrations, such as those used in vibrating parts of gas turbine engines, are usually required to avoid resonance frequencies. Generally, the operating frequency is designed at more than resonance frequencies. When a vibrating structure starts or stops, the structure has to pass through a resonance frequency, which results in large stress concentration. This paper presents the transient thermoelastic stress analysis of vibrating cantilever beam using infrared thermography and finite element method (FEM). In FEM, stress concentration factor at the 2nd resonance vibration mode is calculated by the mode superposition method of ANSYS. In experiment, stress distributions are investigated with infrared thermography and dynamic stress concentration factor is estimated. Experimental result is agreed with FEM result within 10.6%. The advantage of this technique is a better immunity to contact problem and geometric limitation in stress analysis of small or micro structures.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.11
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• pp.1061-1067
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• 2005

The resonant frequency modulation of $YBa_2Cu_3O_{7-x}$ meander lines has been investigated as functions of optical pulse energy and temperature by using a network analyzer. The frequency-domain measurements are performed by controlling both the resonant frequency and the frequency width. The meander lines, configured in a microstrip geometry, are illuminated by optical pulses from an actively mode-locked Nd:YAG laser. The variation of the resonant frequency shows a quadratic dependence on the reduced optical pulse energy $P/P_c$, where $P_c$ is defined as the critical optical pulse energy at which resonance signal has disappeared. As for the dependence on temperature, the results are in good agreement with the previously reported data.

• Journal of Sensor Science and Technology
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• v.20 no.2
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• pp.102-106
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• 2011

This paper presents a design and analysis of an electromagnetic micro generator which can convert low frequency vibration energy to electrical power. The design aspects of the micro generator comprised planar spring, Cu coil and a permanent magnet(NdFeB). Threetype spring designs and four materials(Parylene, FR-4, Cu and Si) were compared to find resonance frequency. It was found that the resonance frequency will be changed according to the spring shape and material. Mechanical and magnetic parameters had been adjusted to optimize the output power through a comprehensive theoretical study.

• Journal of the Korean Ceramic Society
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• v.30 no.2
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• pp.101-106
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• 1993

Effects of CaO on microwave dielectric properties of (Ba, Pb)O-Nd2O3-TiO2 ceramic ystem were investigated. As the content of CaO increases, the sintered bulk density decreases due to the decrease of sinterability. However, with increasing the sintering tmperature, the relative dielectric constants increases. This has been attributed on the formation of the 2nd phase inclusion, TiO2(rutile). The Q values increase due to the compensation effect of Ca ions up to 1 wt%, and then decrease due to the interfacial relaxation effects. The temperature coefficient of resonance frequency increases to a positive direction with increasing the amounts of CaO.