• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.10
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• pp.15-20
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• 2013

In this paper, wireless power transfer system using the magnetic resonance was designed and applied to LED lighting for implementation of wireless lighting. This lighting was made by the converted DC driving type and the direct AC driving type. In the former, transferred AC power was rectified into DC and regulated to the specified voltage value, which leads to produce the loss at the rectifying and regulating circuit. In the latter, wireless-transferred AC power was directly applied to LED, which get rid of the loss derived from the additional circuit. For the efficiency-comparison between the former and the latter, the power at each stage was measured when the same optical output radiated from LED lighting part. The result revealed that the direct AC driving type had 18% higher efficiency than the DC driving type and confirmed that LED lighting using magnetic resonance wireless power transfer system can be efficient by direct AC power supply. And the direct AC driving type had the simple circuit structure and the simple LED lighting formation, so this can leads to various application.

• Journal of the Korean Society of Safety
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• v.32 no.2
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• pp.85-91
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• 2017

When the shell-type roller gate is partly open, at a certain height the large vibration is caused due to resonance and the vibration can cause damage to the gate. In this study, the review on amplitude of vibration and the possible resonance occurring at the time of opening or closing of gate is performed. Throughout the natural frequency analysis, the installation location of the measuring instrument was selected. On opening or closing of gate, the measurement of gate vibration is performed. The natural frequencies according to the opening range of the gate is analyzed. As a result of measurement and analysis, we proposed ranges in which vibration occurs largely and resonance is predicted as an avoiding open ranges, or the safe opening or closing of the shell-type roller gate. The application of this paper's avoiding open range estimation method of shell-type roller gate can be utilized as the basic data for the systematic and rational maintenance management of dams and submerged weirs in the future, and it is expected that this study can bring forth.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.127-130
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• 2005

In this paper, we investigated the change of recognition distance according to the resonance frequency of the transponder for the ISO 14443 Type A 13.56MHz RFID(Radio Frequency IDentification) system. We made thirteen transponders of the same size. The dimension of the transponder is $84.65mm{\times}53.00mm{\times}0.45mm$. We measured the resonance frequency by means of an inductive coupling. The measured resonance frequencies were between 12.9MHz and 17.3MHz. We measured the maximum distances where the transponder's USN(Unique Serial Number) was recognized and the subcarrier was observed. The measurement results show that we can obtain good performance when the Type A transponder has the resonance frequency around 14.2MHz for the given case.

• Electrical & Electronic Materials
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• v.8 no.1
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• pp.27-34
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• 1995

The analysis of nonlinear equivalent circuit and the resonance characteristics of input current and output voltage were simulated, and their electrical properties are discussed in the transverse-type piezoelectric ceramic transformer. The nonlinear resonance characteristics of input current and output voltage showed by the thermal effect due to a higher driving current, the nonlinearity increased greatly as driving current increased. When load resistor was 100[M.ohm.], the nonlinear coefficient was -1.3. The nonlinear resonance curve of input current and output voltage for a variation of input voltage and load resistor agreed with the discussed theory. The output voltage increased nearly proportioned to input voltage when load resistors were below 50[M.ohm.], the voltage step-up ratio decreased when a load resistor was 100[M.ohm.] and their maximum value was 950.

• Journal of KSNVE
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• v.8 no.4
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• pp.643-653
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• 1998

The sub-resonance modes can be easily excited by the assembling tolerance in the asymmetric type optical pick-up actuators, compared with the symmetric type. In this paper, we propose the novel method for reducing the vibration due to the sub-resonance modes whose amplitude can be decreased by adding the damper and increasing the flexibility of holder PCB. Using the finite element method, the change of mode shapes is investigated as the shape of holder PCB is modified. Experimental results support that the propopsed method reduces remarkably the vibration of sub-resonance modes of the optical pick-up actuator.

• Journal of ILASS-Korea
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• v.29 no.1
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• pp.23-31
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• 2024

This study conducted a 3D thermo-acoustic analysis based on the helmholtz solver to analyze the major resonance modes causing combustion instability in a single-can combustor. The experimental investigations were carried out on a test rig designed by the Korea Institute of Machinery & Materials (KIMM) under various conditions of hydrogen co-firing and fuel staging. Through these experiments, two primary unstable frequencies were identified. To determine the resonance modes of these frequencies, a 3D thermo-acoustic analysis was conducted using temperature information from the test rig. The results confirmed that the unstable frequencies observed in the experiments were all longitudinal modes. Additionally, the mode shapes identified in the analysis facilitated a simplification of the exit geometry for the low-order network model, confirming that this did not significantly affect the fundamental resonance modes.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.11
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• pp.77-83
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• 2010

This paper presents the dual resonance PIFA(Planar Inverted F-Antenna) which satisfies the requirements of the 802.11n standard at both 2.4 GHz and 5 GHz frequency bands. Patch for 2.4 GHz and U-Type slot for 5 GHz were used for dual resonance, respectively. In this paper, the characteristics of an antenna were investigated by varying locations of short plate and feed point, the width of the short plate, the thickness and the location of U-Type slot. To investigate the characteristics of the PIFA, HFSS(High Frequency Structure Simulation) for the simulation was used. And the measurement results of a fabricated PIFA were compared with the simulated ones. The measurement and simulation results show that good dual resonance characteristics as the thickness of U-type slot decreases and when the location of U-type slot is far from the feed point.

• The Journal of the Acoustical Society of Korea
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• v.30 no.4
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• pp.223-230
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• 2011

Korean bell is hung with some air gap between the bell bottom and the ground. In addition, it has a peculiar acoustic element, so called resonance cavity below the bell. A proper design of the air gap and cavity size dramatically amplifies the bell sound by resonance effect. Bell interior cavity, air gap and resonance cavity consist of an acoustic cavity system. When the acoustic cavity frequency coincides with the natural frequency of the bell body, the frequency component is significantly amplified. On the Sacred Bell of the Great King Seongdeok, this study proposes a resonance condition of the cavity system considering air gap effect for the first time. With the exact dimension of the bell, boundary element analysis is performed using SYSNOISE. Finally, this study reveals how the temperature in season influences the resonance condition and proposes a concept of variable type resonance cavity. By using the variable type resonance cavity, the cavity size is controlled on site and exact resonance is available regardless of temperature difference in season.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.12
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• pp.1905-1910
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• 2001

Pressure resonance frequency that is caused in the combustion chamber can be interpreted by acoustic analysis. Until now the pressure resonance has been assumed and calculated to a disc type combustion chamber that neglected the combustion chamber height because the knock occurs near the TDC(top dead center). In this research FEM(finite element method) has been used to calculate the pressure resonance frequency inside the experimental engine combustion. The error of the resonance frequency obtained by FEM has decreased about 50% compared to the calculation of Draper's equation. Due to the asymmetry in the shape of the combustion chamber that was neglected in Draper's equation we could find out that a new resonance frequency could be generated. To match the experimental results, the speed of sound that satisfies Draper's equation is selected 13% higher than the value for pent-roof type combustion chamber.

• The Journal of the Acoustical Society of Korea
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• v.16 no.1
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• pp.76-80
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• 1997

Acoustic resonance characteristics were analyzed and their effect on the refrigerating capability were experimentally verified on a fabricated Hofler-type thermoacoustic refrigerating system. Factors governing the overall resonance are the resonator composed of a cavity and two pipes, the loudspeaker driving the resonator, and rear side impedance characteristics of speaker housing. All these are coupled with electric constants of the speaker to exhibit electric resonance. Also the 'wall-effect' within the resonator causes attenuation to reduce the sharpness of the resonance. Analysis and experiments showed housing and the wall-effect of the resonator reduce the sharpness of resonance. Maintaining the accuracy of the resonance is, therefore, very important for efficient refrigeration.