• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1991년도 하계학술대회 논문집
• /
• pp.516-520
• /
• 1991

This paper presents a comparative analysis of two inverter power supply topologies for induction heating and melting applications. The comparison is based on criteria such as resonant condition, component ratings, minimum and maximum operating frequencies, operation under varying load conditions, inverter starting current, and diode reverse recovery time. The voltage source series/parallel resonant inverters are found to offer the best overall performance with respect to converter utilization.

• 한국소음진동공학회논문집
• /
• 제19권7호
• /
• pp.685-692
• /
• 2009

Vehicle interior noise is the results of numerous sources of excitation. One source involving tire pavement interaction is the tire cavity resonance and the forcing it provides to the vehicle spindle. Using a simplified model for the tire acoustic cavity system only, we formulated finite element equation to predict the fundamental acoustic cavity resonant characteristics inside tire-wheel assembly of undeformed and deformed tire. Combining the finite element analysis with experimental verification, we explained the acoustic characteristics theoretically. Especially, we have shown that the difference between the first two resonant frequencies increases as the deformation of deformed tire increases.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2009년도 춘계학술대회 논문집
• /
• pp.551-556
• /
• 2009

Vehicle interior noise is the results of numerous sources of excitation. One source involving tire pavement interaction is the tire cavity resonance and the forcing it provides to the vehicle spindle. Using a simplified model for the tire acoustic cavity system only, we formulated finite element equation to predict the fundamental acoustic cavity resonant characteristics inside tire-wheel assembly of undeformed and deformed tire. Combining the finite element analysis with experimental verification, we explained the acoustic characteristics theoretically. Especially, we have shown that the difference between the first two resonant frequencies increases as the deformation of tire due to vertical load increases.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1989년도 하계종합학술대회 논문집
• /
• pp.544-547
• /
• 1989

The introduction of resonant link inverters has allowed the use of much higher switching frequencies in induction motor current regulators. The resonant link inverter,however, requries the use of discrete time switching strategies. This type of controller,while giving the best possible performance, is difficult to implement, since motor parameters must be calculated or measured. The delta modulated current regurator (DMCR) has been introduced as a controller without additional state feedback. A discrete pulse modulated current regulator which controls load current is introduced in the paper.

• 한국전기전자재료학회논문지
• /
• 제20권10호
• /
• pp.869-872
• /
• 2007

In this study, in order to develop low temperature sintering ultrasonic nozzle, single-layer and multilayer ring-type piezoelectric actuators were manufactured using PMN-PNN-PZT ceramics, And then the electrical properties were investigated. A ring-type piezoelectric actuator was modeled by ATILA program using finite element method(FEM). The piezoelectric actuator dimension was $\Phi26.5$ (outer diameter), $\Phi12$ (inner diameter), 3.5 mm (thickness). By FEM analysis, resonant and anti-resonant frequencies were appeared as 56.7 kHz and 61.5 kHz. The displacement increased with the increases of the number of layer. Based on the result, ring-type multilayer piezoelectric actuators were manufactured at low co-firing temperature of $940^{\circ}C$. The resonant resistance decreased with the increases of the number of layer. And also, the capacitance increased with the increases of the number of layer. The mechanical quality factor (Qm) decreased with the increases of the number of layer.

• 한국인터넷방송통신학회논문지
• /
• 제11권5호
• /
• pp.81-86
• /
• 2011

본 논문에서는 반원의 프랙탈 마이크로스트립 패치 안테나를 설계함으로써 안테나를 다중 공진시켜 대역폭의 문제점을 개선하였으며, 이는 IEEE 802.11의 무선랜 대역을 포함하고 IEEE802.16e인 이동형 WiMax의 규격을 동시에 포함할 수 있는 무지향성 안테나를 설계하고 특성을 측정하다. 안테나의 다중공진을 위해 공진주파수, 임피던스정합, 극성 및 방사패턴을 훌륭히 제어할 수 있는 다중 독립 주파수를 만족시키기 위해 세 개의 반원의 프랙탈 패치를 삽입함으로써 무선통신을 위한 안테나를 설계하였다.

• Journal of electromagnetic engineering and science
• /
• 제1권2호
• /
• pp.176-181
• /
• 2001

This paper presents the farced resonant characteristics of an electrically small cavity partially filled with dielectric material. The method of moments with Galerkins procedure is used to determine the farced resonant characteristics of the small cavity. In order to obtain the equations of the external reactance gives rise to the farced resonance at a given frequency, the cavity with external reactance can be treated as two-port network which has the admittance parameters. Numerical results show that the forced resonance, series or parallel resonance, can be obtained by the controlling the external reactance. To verify the availability of the theoretical analysis, experiments are carried out for the bakelite as the material by measuring the length of external reactance at operating frequencies.

• 대한기계학회논문집B
• /
• 제29권1호
• /
• pp.95-102
• /
• 2005

Acoustic behavior in gas turbine combustor with acoustic resonator is investigated numerically by adopting linear acoustic analysis. Helmholtz-type resonator is employed as acoustic resonator to suppress acoustic instability passively. The tuning frequency of acoustic resonator is adjusted by varying its length. Through harmonic analysis, acoustic-pressure responses of chamber to acoustic excitation are obtained and the resonant acoustic modes are identified. Acoustic damping effect of acoustic resonator is quantified by damping factor. As the tuning frequency of acoustic resonator approaches the target frequency of the resonant mode to be suppressed. mode split from the original resonant mode to lower and upper modes appears and thereby complex patterns of acoustic responses show up. Considering mode split and damping effect as a function of tuning frequency, it is desirable to make acoustic resonator tuned to broad-band frequencies near the maximum frequency of those of the possible upper modes.

• 소음진동
• /
• 제4권2호
• /
• pp.209-219
• /
• 1994

Classical method calculates the resonance frequency of Helmholtz resonator by postulating that there is a moving mass in neck and a stiffness which expresses the compressibility of cavity. This has been widely accepted as reasonable to determine the resonant frequency, provided that the wave length of interest is longer that any length scale of resonater. Nevertheless, it has been often recognized that this classical method sometimes does not well predict the resonant frequency. This paper decribes the way in which the dynamics of resonator very often does care about the detail geometries of resonator; location of the neck, diameter ratio of the neck to that of cavitty, length of resonator compared with that of neck, etc. This rather unexpected observations have been proved theoretically; 3 dimensional analysis of acoustic wave equation, as well as experimentally by comparing the resonant frequencies, transmission loss, and insertion loss of resonator.

• Journal of electromagnetic engineering and science
• /
• 제10권4호
• /
• pp.219-223
• /
• 2010

Based on a provided closed-form wireless power transmission (WPT) efficiency formula, which may be used for any value of load, we have analyzed the WPT efficiencies between two metamaterial-inspired loop antennas in various aspects. Due to the modeling based on low frequency circuit theory, the provided formula at the center resonant frequency has been found to be accurate until when the distance between the two loop antennas increases to 15 cm (about $\lambda_0/6$ at 300 MHz). When the two loops get closer, the resonant frequency has been found to split into two in theory, simulations, and measurements. The EM-simulated and measured efficiencies at new resonant frequencies are 60.9 % and 46.3 %, respectively, at d=15 cm. With two extra rings around the loops, the maximum efficiency is enhanced to 93.7 % at d=15 cm. The effect of the additional two rings is about 30 %.