• The Journal of the Acoustical Society of Korea
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• v.28 no.1
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• pp.70-76
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• 2009

In speech communications in noisy environments, speech intelligibility is seriously degraded due to the masking effect of ambient noise. In this paper, a new method to improve speech intelligibility in noisy environments is proposed. Based on the perception theory that the temporal envelope plays a major role in determining intelligibility, the proposed method uses a novel operation that enhances the fluctuation of band-wise temporal envelope and also contains pitch enhancement for improving speech naturalness. In addition, a new subjective evaluation scheme employing binaural listening is proposed in order to measure more reliable performance. The subjective performance measured with the proposed scheme shows that the proposed method improves both intelligibility and naturalness in various environments, whereas a function parameter can control the performance trade-off between intelligibility and naturalness.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.20 no.2
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• pp.194-202
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• 2008

In general, forecast tsunami heights announced for tsunami warning are computed by using a linear tsunami model with coarse grids which leads the underestimation of inundation area. Thus, an accurate tsunami inundation map corresponding the forecast tsunami height is needed for an emergency evacuation plan. A practical way to construct a relatively accurate tsunami inundation map was proposed in this study for the quantitative forecast of inundation area. This procedure can be introduced as in the followings: The fault dislocations of potential tsunami sources generating a specific tsunami height near an interested area are found by using a linear tsunami model. Based on these fault dislocations, maximum inundation envelops of the interested area are computed and illustrated by using nonlinear inundation numerical model. In this study, the tsunami inundation map for Imwon area was constructed according to 11 potential tsunami sources, and the validity of this process was examined.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.10
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• pp.964-970
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• 2013

This paper presents a bandpass wireless 3-D chip to chip interface technique. The proposed technique uses direct amplitude modulation of the free running oscillator which especially utilizes the coupling capacitance between two stacked chips as a part of the resonator. Therefore, the oscillator is three dimensionally configured and a simple envelope detector can be used as a receiver without any additional matching circuitry. The proposed link was designed and fabricated using 110 nm CMOS technology and experimental results successfully showed the data transmission at a data rate of 2 Gb/s for the stacked chips with a thickness of 50 ${\mu}m$ consuming 4.32 mW. The sizes of the Tx and Rx chips are 0.045 $mm^2$ and 0.029 $mm^2$, respectively.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.9
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• pp.2261-2266
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• 2009

A novel adaptive phase calibration method is proposed for nonlinear amplifiers. Based on the adaptive process of simple phase vector calculations, the AM/PM distortion can be significantly reduced for various input power. The performance of the proposed method is evaluated for up to 80 % improvements in AM/PM distortions, compared with the distortion of a conventional amplifier. Moreover, by means of an additional envelope-compensation technique, the improvement of the adjacent channel power ratio (ACPR) is presented.

• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.4
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• pp.39-49
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• 2003

This research is a part of a research program to develope a new design method for reinforced concrete bridge columns under axial load and cyclic lateral load. A nonlinear analytical method is proposed to obtain moment-curvature relationship and lateral load-displacement relationship. Various analytical models that contribute seismic behavior of reinforced concrete bridge columns are adopted and modified by comparing quasi-static test results of reinforced concrete columns with spirals of circular hoops. The analysis adopts confined concrete model, longitudinal reinforcement test result of reinforced concrete columns with spirals or circular hoops. The analysis adopts confined concrete model, etc. The results obtained using the propose analytical method agree well with test results and give conservative estimations particularly for deformation capacity and ductility.

• Korean Journal of Optics and Photonics
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• v.5 no.1
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• pp.9-17
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• 1994

Optical properties of $TiO_2$ thin films prepared by ion-beam assisted deposition(1BAD) were investigated. The result shows that the refractive index of IBAD TiOL thin films measured by an envelope method is closer to that of the corresponding bulk than that of conventionally deposited $TiO_2$ thin films and the packing density of IBAD $TiO_2$ thin films measured by a vacuum-to-air spectral shift of films increases drastically. The vacuum-to-air spectral shift of an IBAD $(TiO_2/SiO_2)$ multilayer interference filter was negligible as compared to that of a conventional interference filter and so the IBAD filter is denser and more stable optically than the conventional filter. Also it is observed that the IBAD and conventional $TiO_2$ thin films are stoichiometric and amorphous.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.13 no.6
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• pp.490-500
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• 1988

In recent years the acquisition, processing and interpretation of three dimensional seisimic data, for the purpose of locating gas and reservoirs, have become practical. This paper exlores one way in which the volume data can be searched and visualized, which may aid the interpreter. The illusion of looking at a three dimensional volume can be obrained by fusing a stereoscopic pair of pictures. Each picture can be made by projecting each data point of the volume into a plane from a point where the eye is placed. The data valuse along any projection line can be summed to form the picture, or only a segment along the line can be selected. By selective projection, the volume can be searched and obscuring layers removed. The stereoscopic pictures show the physical models in there ture spatial positions. Projection of the envelope function of the seismic traces is shown to give improved depth perception compared with projection of the position amplitudes.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.7
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• pp.1086-1093
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• 2001

A new linearization technique for RF high-power amplifiers(HPAs) using n-th order error signal generator (ESGn) is proposed. The n-th order ESG generates an error signal based on the complex envelope transfer characteristics of the HPA, which is combined at the output of the HPA. Therefore, the higher-order nonlinearlities are not affected by the ESG$\_$n/ and the stability of the linearized system is guaranteed due to the inherent open-loop configuration. Moreover, the output delay loss can be avoided, because the error signal is generated with the input signal of the HPA. The IMD(intermodulation distortion) improvement obtained applying the ESG$\_$7/ to 5 W class A HPA in cellular band demonstrates the feasibility of the proposed postdistortion system.

• Journal of the Korean Geotechnical Society
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• v.19 no.1
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• pp.93-102
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• 2003

Unconfined compression test (UC) has been widely used to determine the undrained shear strength ($c_u$) of clay, because it is convenient and economical. However, UC can not represent the behaviour of in-situ stress condition and the strength obtained by the test is generally underestimated compared to that of triaxial compression, due to no confining pressure. Therefore, a simple and practical method to correct the ($c_u$) for sample disturbance and to be used in geotechnical practice is needed. This study is aimed at proposing the method to estimate in-situ undrained shear strength from UC with suction measurement. The proposed method is based on theoretical shear strength equation of perfect sample (Noorany & Seed, 1965), and effective overburden stress and analysis results ($A_f,\phi'$) of effective stress behaviour by UC are needed for the equation. The shear resistance angle ($\phi'$) can be simply estimated through the result that $K_f$-line slope of the UC is 1.6 times higher than that of triaxial compression test. The result of this study shows that the measured strength by this method is very similar to that of the undrained shear strength by triaxial compression test (CK$_0$UC).

• The Journal of the Acoustical Society of Korea
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• v.20 no.2
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• pp.77-85
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• 2001

This paper proposes a method of time-scale modification of polyphonic audio signals based on a sinusoidal model. The signals are modeled with sinusoidal component and noise component. A multiresolution filter bank is designed which splits the input signal into six octave-spaced subbands without aliasing and sinusoidal modeling is applied to each subband signal. To alleviate smearing of transients in time-scale modification a dynamic segmentation method is applied to subbands which determines the analysis-synthesis frame size adaptively to fit time-frequency characteristics of the subband signal. For extracting sinusoidal components and calculating their parameters matching pursuit algorithm is applied to each analysis frame of subband signal. In accordance with spectrum analysis a psychoacoustic model implementing the effect of frequency masking is incorporated with matching pursuit to provide a resonable stop condition of iteration and reduce the number of sinusoids. The noise component obtained by subtracting the synthesized signal with sinusoidal components from the original signal is modeled by line-segment model of short time spectrum envelope. For various polyphonic audio signals the result of simulation shows suggested sinusoidal modeling can synthesize original signal without loss of perceptual quality and do more robust and high quality time-scale modification for large scale factor because of representing transients without any perceptual loss.