• Proceedings of the KSPS conference
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• 2007.05a
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• pp.247-250
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• 2007

The affricates of the Korean were alveolar sounds in the 15th century. Alveolar sounds have changed to post-alveolar or alveo-palatal sounds since the 18th century, at least in Southern Korean. These days, the advanced articulation of the affricates are observed, especially in the speech of young generations. The aim of this paper is to show the differences of the affricates when they are pronounced in alveo-palatal and in a more advanced position than in alveo-palatal by their cut-off frequencies. We have recorded speeches of freshmen(in their early twenties) at Seoul National University. The result was that the cut-off frequency of the advanced articulation in auditory observations was higher than that of the others. We have found in particular, that women have tendency to advance their place of articulation of the affricates.

• The KSFM Journal of Fluid Machinery
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• v.2 no.1 s.2
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• pp.43-49
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• 1999

Flow field and near-field noise of a centrifugal fan has been studied with an efficient compressible method and STAR-CD. The flow field of the centrifugal fan is assumed to be two-dimensional. Most of the compressible studies have been done by inviscid solver because viscous simulation shows little difference. The near field noise is estimated in terms of sound pressure level in frequency domain transformed from the computed pressure fluctuations using FFT. The simulation has been done on various design elements such as impeller blade shapes, the number of blades and cut-off clearance. The comparison shows that the number of blades has a significant effect on near-field noise without losing aerodynamic performance.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.11
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• pp.1584-1589
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• 2013

A new and significantly small guided and resonant structure is suggested to take over bulky metallic hollow waveguides used in military satellite transceivers. Below Ku-band, the conventional waveguides resulting in quite heavy transceivers will be replaced by the low profile SIW(substrate integrated waveguide) structures that are distinguished from the others in that the suggested ones have much lower cut-off frequencies by the circuital configuration of DNG(dobule negative) constitutive parameters and become even smaller than the other SIWs. The design scheme is validated by the circuit and full-wave simulations from the guided, resonant, and coupled structures. Besides, a bandpass filter as the suggested coupled structure is fabricated with a cheap substrate in a low-budget fabrication process and its frequency response is measured as verification of the purpose of the design.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.7
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• pp.693-700
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• 2008

High-Pressure gas Pipeline which is buried in underground has the Possibility that will be exposed to unexpected dangerous impact of construction equipment. To protect from this kind of danger, the real-time health monitoring system of the high-pressure gas pipeline is necessary. First of all, to make the real-time health monitoring system clearly, the acoustic wave propagation characteristics which are made from various construction equipment impacts must be identified. In link of technical development that prevents the damage of high-pressure gas pipeline, this paper gives FEM(finite element method) and BEM(boundary element method) solutions to identify the acoustic wave propagation characteristic of the various impact input signals which consist of Direc delta function and convolution signal of 45 Hz square signal and random signal.

• The Transactions of the Korean Institute of Power Electronics
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• v.13 no.6
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• pp.447-452
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• 2008

In the paper, the product-type PLL system, which is so suitable for synchronizing a single phase grid voltage is designed. The PLL system is modelled with the small signal analysis. Both the cut-off frequency of low pass filter and the optimal gain are derived by considering the transient response for synchronization as well as a distortion of synchronization signal. Through the simulation studies and experimental results, the transient response and ripple component of synchronization signal are investigated with a variation of both the cut-off frequency and gain in order to verify the performance of design.

• Journal of the Institute of Convergence Signal Processing
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• v.3 no.2
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• pp.45-52
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• 2002

EMI(Electromagnetic Interface) is a measure of electomagnetic radiation from equipment in the range of 10KHz to 3GHz, and can cause unexpected reactions of electronics/electrical equipment. In this study, for safe and stable communication operation, a STGU(System Timing Genetation Unit), which is a 2.5Gbps SDH System and a major EMI source, was employed to simulate electromagnetic interface. In On-Site test, the power of fundamental frequency of EMI of interest and its harmonics were measured. Also, a low pass filter at cut-off frequency of 2GHz was specifically designed to minimize the effect of EMI between electronic components. When the low pass filter was implemented within the STGU, the power of EMI decreased more than 20dBm. Finally, when TIE and MTIE, two important quality measure in synchronous reference clcok, was assessed, ITU-T G8l3 requirements are satisfied.

• ETRI Journal
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• v.37 no.5
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• pp.945-950
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• 2015

A novel microstrip low-pass filter is presented to achieve an ultra-wide stopband with 11 harmonic suppression and very sharp skirt characteristics. The filter is composed of a modified U-shaped resonator (which creates two fully adjustable transmission zeroes), a T-shaped resonator (which determines a cut-off frequency), and four radial stubs (which provide a wider stopband). The operating mechanism of the filter is investigated based on a proposed equivalent-circuit model, and the role of each section of the proposed filter in creating null points is theoretically discussed in detail. The presented filter with 3 dB cut-off frequency ($f_c=2.35GHz$) has been fabricated and measured. Results show that a relative stopband bandwidth of 164% (referred to as a 22 dB suppression) is obtained while achieving a high figure-of-merit of 15,221.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.17 no.10
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• pp.1051-1062
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• 1992

Design of a continuous-time fifth-order OTA-C Eiliptic filter for operation at 4MHz is presented. The filter has been realize by five OTAs, eight capacitors and a buffer as an OTA-C structure. To prevent decreasing of characteristics due to the parastic capacitance of OTA and loading a buffer and a capacitor have been connected to the next of second section. As the result the frequency characteristics were found to be essentially within specifications : less than 0.2dB passband attenuation, 30dB stopband attenuation and 4Mz cut-off frequency have been obtained and the characteristic of cut-off region has been improved about 7dB compared with it of the theoretical case.

• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.1
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• pp.9-14
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• 2012

In this study, the diplexer used a separator or a combine of signals was designed and its characteristics were investigated. The diplexer consists of two fixed tuned bandpass filter such as low pass filter(LPF) and high pass filter(HPF) sharing a common part and was simulated. The diplexer with micro-strip structure was fabricated. The LPF of diplexer has insertion loss of -0.4 dB, return loss of -30 dB and 1.6 GHz cut-off frequency and HPF has insertion loss of -0.8 dB, return loss of -30 dB and 1.9 GHz cut-off frequency, respectively.

• ETRI Journal
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• v.33 no.6
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• pp.985-988
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• 2011

A novel application of a dual-transmission line is proposed to design a lowpass filter (LPF). The proposed structure uses only transmission line elements to produce an equiripple LPF response with sharp roll-off. Design equations are derived using a lossless transmission line model. Controlling the electrical lengths, three transmission-zeros are realized in the stopband to obtain a sharp roll-off rate and wide stopband bandwidth. A single unit microstrip LPF with a 3-dB cut-off frequency at 1.0 GHz having a roll-off of 135 dB/GHz along with a stopband bandwidth of 69.5% is designed for validation.