• Proceedings of the Acoustical Society of Korea Conference
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• 1993.06a
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• pp.17-20
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• 1993

The acoustic mode of a perforated tube muffler was investigated both theoretically and experimentally to explain the cavity-tones induced by through-flow. The cutoff frequencies for the axisymmetric modes were obtained and confirmed experimentally. It was found that the cutoff frequencies are decreased significantly by the perforated tube. The onset frequencies of the cavity-tones were compared with the cutoff frequencies of the acoustic mode and it was found that the cavity-tones are induced by the radial acoustic modes and their frequency stages are coincident with the discrete cutoff frequencies.

• ETRI Journal
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• v.9 no.2
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• pp.55-61
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• 1987

The effective cutoff wavelength of $LP_11$mode is measured as a function of fiber length for three types of single-mode optical fiber which have different characteristics in the index profile or the coating structure. The measured cutoff wavelength decreased linearly in a logarithmic scale of fiber length as increasing fiber length, and eventually became constant after 3km for two fiber types. It is found that the length dependence of cutoff wavelength is due to a mode coupling between the $LP_01$ and $LP_11$ modes.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.34C no.11
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• pp.56-65
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• 1997

In this paper, a design of current-mode continuous-time filters for low voltage and high frequency applictions using complementary bipolar current mirror paris is presented. The proposed current-mode filters consist of simple bipolar current mirrors and capacitors and are quite suitable for monolithic integrtion. Since the design method of the proposed curent-mode filters is based on the integrator type of realization, it can be used for a wide range of applications. And the cutoff frequency of th efilters can be easily changed by the DC cntrolling current. As design examples, the 5th order butterworth filters are designed by cascade and leapfrog methods with tunable cutoff frequencies from 30MHz to 100MHz. The characteristics of the designed current mode filters are simulated and examined by SPICE using standard bipolar transistor parameters.

• Journal of the Korea Society for Simulation
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• v.6 no.2
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• pp.117-124
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• 1997

A simulation model for the estimation of cutoff connection rate in the asynchronous transfer mode (ATM) switching system under multimedia traffic environments is presented. The simulator is developed by the integration of the AweSim tool with user-written C++ routines that model the internal structures of operational details of the switching system. For the case study, the simulator is applied to the ATM switching system developed by Electronics and Telecommunications Research Institute (ETRI) to compare design alternatives according to the cutoff connection rates.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.10
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• pp.3905-3910
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• 2010

In this paper, a 3rd-order Chebyshev current-mode filter in 1.8V-$0.18{\mu}m$ CMOS parameter is designed. The core circuit of the current-mode filter is composed with the proposed voltage-controlled frequency tunable current-mode integrator. Using the proposed current-mode integrator, the cutoff frequency of the filter can be controlled and also total power consumption can be reduced. HSPICE simulation results show the cutoff frequency of the filter is controlled between 1.2MHz and 10.1MHz, and the power consumption is 2.85mW at Vdd=1.8V.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.7 no.5
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• pp.440-446
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• 1996

The multiple-ridged circular waveguides is analyzed using Fourier series and the mode matching technique. The enforcement of the boundary conditions yields the simultaneous equations for the field coefficient inside the waveguides. The simultaneous equations are solved to represent a dispersion relation in an analytic series form. The numerical computation is performed to illustrate the behavior of the cutoff wavenumbers in terms of number, length and angle of ridges. The presented series solution is exact and rapidly-convergent so that it is efficient for numerical computation. A simple dispersion relation based on the dominant mode analysis is obtained and is shown to be very accurate for most practical applications.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.10B
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• pp.1885-1894
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• 1999

The higher mode cutoff frequencies in Crawford TEM cells computed by the Galerkin method(GM) describe in this paper. The authors also report the half mode boundaries to solve not only the cut-off frequencies of symmetric TEM cells and those of asymmetric TEM cells. It is shown that the measured resonant frequencies of the present symmetric TEM cells and a designed asymmetric TEM cell are agreed with the calculated results.

• Journal of the Korean Institute of Telematics and Electronics
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• v.11 no.4
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• pp.29-37
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• 1974

Theoretical analysis is carried out for the curtoff wavelength characteristics of rectangular waveguide containing a step-ridge. In order to obtain the cutoff wavelength of step-rigde waveguide, an transmission matriz is formulated by the method of equivalent transverse resonance. The characteristic equation, in which the wavelength is obtainable by the numerical method, is derived from the equation. An approximate determination of the dominant mode fields in step-ridge waveguides at all frequencies has been made. Using these fields, the characteristic impedance equation is derived from power considerations. Analyzing the results of the calculations, the following characteristics are noted. The values of λ /a of TE10 mode increase with decreasing gap lengths and with increasing step width S or S , or both. Experimental results of cutoff characteristics are in good agreement with the theoretical analusis. It is shown that a waveguide within which a step-ridge is placed has a lower cutoff frequency and impedance than empty guide without it. Therefore, the role of a step-ridge guide is to broadening the bandwidth 2 to 3 times more than that of an empty guide of the same demension.

• The Journal of the Acoustical Society of Korea
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• v.22 no.7
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• pp.554-561
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• 2003

Results of the numerical simulation and experimental data analysis for identification of mode cutoff frequency and estimation of sound speed of seabed from the spectrum of acoustic signal received at fixed source-receiver range are presented. Model simulations for Pekeris waveguide show that the frequency-dependent propagation loss and interference pattern are closely related to mode cutoff frequencies and it could be possible to the identify them from the changes of interference pattern. The concept considered at numerical simulations is applied to signals acquired at sea test. Cutoff frequency and sound speed of seabed are estimated from the interference pattern of measured signal. Propagation loss predicted using the estimated sound speed of seabed as model input parameter shows similar estimation result compared to propagation loss derived from measured data.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.19 no.2
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• pp.198-203
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• 2010

In this paper, study on the mode characteristics analysis of the SH-EMAT (shear horizontal, electromagnetic acoustic transducer) waves for evaluating the thickness reduction in plates such as corrosion and friction is presented. Noncontact methods for ultrasonic wave generation and detection have been a great concern and highly demanded due to their capability of wave generation and reception on surface of high temperature or on rough surface. Mode identification of the SH-EMAT wave is carried out in an aluminum plate with thinning defects using time frequency analysis method such as wavelet transform, compared with theoretically calculated group velocity dispersion curve. The changes of various wave features such as the amplitude and the time-of-flight have been observed and the correlations with the thickness reduction have been investigated. Firstly, experiments have been conducted to confirm that it is possible to selectively generate and receive specific desired SH modes. These modes have then been analyzed to select the parameters that are sensitive to the thickness change. The results show that the mode cutoff and the time-of-flight changes are feasible as key parameters to evaluate the thickness reduction.