• Journal of Mechanical Science and Technology
• /
• 제20권7호
• /
• pp.941-949
• /
• 2006

Nonlinear behavior analysis was used to verify whether a one-way clutch is effective for reducing the torsional vibration of a paired spur gear system under periodic excitation. The dynamic responses were studied over a wide frequency range by speed sweeping to check the nonlinear behavior using numerical integration. The gear system with a one-way clutch showed typical nonlinear behavior. The oscillating component of the dynamic transmission error was reduced over the entire frequency range compared to a system without a one-way clutch. The one-way clutch also eliminated unsteady continuous jump phenomena over multiple solution bands, and prevented double-side contact, even with very small backlash. Installing a one-way clutch on both sides of the gear system was more effective at mitigating the negative effects of external periodic excitation and various parameter changes than a conventional gear system without a one-way clutch.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2001년도 춘계학술대회논문집
• /
• pp.1210-1216
• /
• 2001

The impinging tones by high-speed plane jets are investigated for the characteristics of edgetone generation based on experimental observations. Experiment has been performed for edgetones with a slit nozzle and a wedge system. The jet in the experiment is varied from low to high subsonic speed to obtain the effect of the speed on the frequency characteristics of impinging tones. The experimental data obtained previously for edgetones and platetones by various nozzles are compared with the present edgetone data for the condition of tone generation, the frequency ranges and the effective source point. It is found that the jet speed has no fundamental influence on the impinging tone characteristics. Regardless of the jet speed, the effective source point is about a quarter wavelength downstream from the edge tip. With increase in jet speed, the influence of the nozzle configuration is decreased and the operating frequencies show good coincidencies by normalized parameters based on the slit thickness.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2000년도 춘계학술대회논문집
• /
• pp.177-182
• /
• 2000

This study aims to provide an effective method to reduce construction noise generated by breakers. To reduce the breaker's noise level, a sound encloser was developed; the sound insulation's performance was tested in the field. From the field test, the following results were obtained. The sound insertion loss was about 6.5dB(A), even though part of the sound encloser for the breaker was left unclosed. This is equal to the reduction value which can be obtained by using more expensive low noise breakers, proving that there are more effective measures for sound insulation at lower cost. The characteristic of frequency was evaluated to show an even reduction through all frequency bands, except 630Hz.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2012년도 춘계학술대회 논문집
• /
• pp.157-162
• /
• 2012

A structural modification of baseframe is an effective method to avoid resonance in marine diesel generator (D/G) set which consists of diesel engine, generator and baseframe. However the reinforcement with thick plates or additional parts to increase the natural frequency can be less effective because of increased weight. Especially fine control of target mode based on the experience is difficult because the weight and interference of system have to be considered. In this paper, the design optimization of baseframe was performed to reduce the resonant vibration using a gradient descent method. The design parameters such as thickness, shape and location of baseframe parts are optimized to increase the torsional natural frequency of D/G set. From the actual test, the new designed baseframe reduced the vibration level in resonance by 55% without any increase of weight and interference. interference.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2000년도 춘계학술대회논문집A
• /
• pp.292-297
• /
• 2000

The seismic isolation technology has appeared to be increasingly necessary for highway bridges, LNG tank, nuclear power plant, and building structures in view of earthquake vibrations. Also high-technology industries require effective seismic protection. The Seismic Isolation Bearing - High Damping Rubber Bearing - system has been counted as the most effective way fur seismic isolation, which is now under development and widely used in industries. Here, the commercial FEM software for nonlinear analysis, MARC, has provided force-displacement curves on the rubber system. The analyses have been carried out about fourteen cases; 25%, 50%, 75%, 100%, 125% and 150% horizontal displacements with a different frequency - 0.01Hz and 0.50Hz - and 100% horizontal displacement with four different frequency - 0.01Hz, 0.16667Hz, 0.3333Hz and 0.50Hz. The unknown constants of the strain energy function of Ogden model have been obtained by a tension test and planar shear test.

• Journal of information and communication convergence engineering
• /
• 제8권6호
• /
• pp.687-689
• /
• 2010

In this paper, the equalization for frequency slope of path loss in Multi-Band(MB) OFDM UWB is proposed. The path loss of a signal is proportionate to the square of the signal's frequency. So, the received signal amplitudes of OFDM subcarrier can be different up to 3dB when MB-OFDM occupies bandwidth over 1.5GHz. The differences of subcarrier-amplitudes make an effective of 0.3 bit reduction of soft decision bits of viterbi decoder, and when the effective of 0.3 bit reduction can cause 0.5dB SNR degradation. This paper proposes two modem architectures which compensate for the degraded subcarrier by multiplying the reciprocal of degraded values in analog or digital domain. It is shown that, for the proposed architecture applied to MB-OFDM UWB, the performance improvements up to 0.5dB can be obtained over the conventional uncompensated receiver architecture.

• 한국정보통신학회:학술대회논문집
• /
• 한국해양정보통신학회 2008년도 추계종합학술대회 B
• /
• pp.61-65
• /
• 2008

In this paper, we studied a ZnO-based film bulk acoustic resonator (FBAR) device fabricated on a specially designed multi-layerd Bragg reflector part. Very thin chromium adhesion layers (0,03um thick) were additionally deposited to improve the quality of the Bragg reflector and some thermal treatments were performed to improve the resonant characteristics of the device. At the operating frequency of ${\sim}2.7GHz$, excellent resonant characteristics were observed in terms of return loss and quality factor, and effective electromechanical coupling coefficient. These findings are expected to be highly promising and effective for improving the performance of the FBAR devices at high frequency.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2003년도 추계학술대회
• /
• pp.1702-1707
• /
• 2003

Absorptive material arrangement method for effective interior noise control is proposed. Sound field with arbitrary boundary condition is formulated by Kirchhoff-Helmholtz integral equation. A simple example such as a rectangular cavity will present physical meaning between changing boundary condition and control of sound field. The effect of changing boundary condition is expressed in modal admittance. From this formulation, an admittance map is presented. The admittance map is the figure to represent position where absorptive material is attached. The admittance map can be assigned to each resonant frequency. There, however, may be common area of those maps. Then, frequency robust arrangement of absorptive material in noise control will be presented.

• 한국정보통신학회:학술대회논문집
• /
• 한국정보통신학회 2012년도 추계학술대회
• /
• pp.561-563
• /
• 2012

In this work, tunable capacitors using a finger-type electrode are designed and characterized for frequency-agile RF circuit applications. Their top electrodes with different area and line width are designed in types of the finger for a long conducting perimeter which results in enhanced fringing-electric fields in order to improve their tunability. The tunable varactors were fabricated on a quartz substrate employing a multi-layer dielectric of a para/ferro/para-electric thin film. Compared to the conventional capacitor, finger-type capacitors are characterized in terms of effective capacitance and tunablility. Their effective capacitance and tunability with the long perimeter increase 24~40% and 7~12%, respectively, due to enhanced fringing electric fields from 1 to 2.5 GHz, compared to the conventional ones.

• 한국소음진동공학회논문집
• /
• 제12권3호
• /
• pp.187-194
• /
• 2002

A seven-port impedance and admittance matrices of multilayered piezoelectric beam are derived for the analysis of piezoelectric AFM ( atomic force microscope) cantilever that is partially covered by the piezoelectric layer. The variational principle is used for deriving the extensional and flexural motional equations and the conjugate parameters. Overall impedance matrix of AFM cantilever can be obtained by combining two impedance matrices of the covered and the non-covered. she resonance and antiresonance frequencies and the effective electromechanical coupling factors are calculated using the derived matrices. The results and the three dimensional finite element solutions are compared with the experimental results in other publication.