• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.1
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• pp.1-8
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• 2010

The Fourier series uses a vibrating wave that possesses an amplitude that is like the one of the sine curve. Therefore, the functions used in the Fourier series do not change due to the value of the frequency and that set a limit to express irregular signals with rapid oscillations or with discontinuities in localized regions. However, the wavelet series analysis(WSA) method supplements these limits of the Fourier series by a linear combination of a suitable number of wavelets. By using the wavelet that is focused on time, it is able to give changes to the range in the cycle. Also, this enables to express a signal more efficiently that has singular configuration and that is flowing. The main objective of this study is to propose a scheme called wavelet series analysis for the application of wavelet theory to one-dimensional problems represented by the second-order elliptic equation and to evaluate theperformance of proposed scheme comparing with the finite element analysis. After a through evaluation of different types of wavelets, the HAT wavelet system is chosen as a wavelet function as well as a scaling function. It can be stated that the WSA method is as efficient as the FEA method in the case of axial bars with distributed loads, but the WSA method is more accurate than the FEA method at the singular points and its computation time is less.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.1
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• pp.57-62
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• 2011

This paper presents a study on the performance analysis on probability of bit error for wavelet in 4-ary SWSK system. The formula for the bit error probability in 4-ary SWSK system was derived from the conventional method. This paper experimentally implements the probability of bit error for Daubechies, Biorthogonal, Coiflet and Symlet wavelet using the conventional formula of bit error probability. Additionally, the performance of bit error probability is analyzed for the period and the number of wavelet taps. Based on the results, we confirmed that the performance of Coiflet and Symlet wavelet for the probability of bit error is superior to the other wavelet, and their probability of bit error are similar.

• Journal of Korea Multimedia Society
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• v.8 no.1
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• pp.19-26
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• 2005

The basis function of wavelet transform used in this paper is constructed by using lifting scheme, which is different from general wavelet transform. Lifting scheme is a new biorthogonal wavelet con-structing method, that does not use Fourier transform for constructing its basis function. In this paper, an image compression and reconstruction method using the lifting scheme was proposed. And this method improves data visualization by supporting a partial reconstruction and a local reconstruction. Approx- imations at various resolutions allow extracting various sizes of feature from an image or signal with a small amount of original information. An approximation with small size of scaling coefficients gives a brief outline of features at fast. Image compression and edge detection techniques provide good frame- works for data management and visualization in multimedia database.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.10A
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• pp.1579-1587
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• 1999

Bias-dependent noise models of $0.2\mu\textrm{m}$ gate length P-HEMT's which are scalable with gate width are proposed. To predict S-parameters of the P-HEMT's the intrinsic parameters except for $\tau$ subtracted the offsets introduced in this paper are normalized to the gate width and then scaled. The small-signal model parameters are expressed as fitting functions of the drain current to $\textrm{I}_{dss}$ ratio and gate width. In addition, to estimate accurately noise parameters the noise temperature $\textrm{T}_{g}$ of the intrinsic resistance, the equivalent noise conductance $\textrm{G}_{ni}$ of the gate current noise source, and the equivalent noise conductance $\textrm{G}_{no}$ of the drain current noise source are adopted as the noise model parameters. The extracted values of $\textrm{T}_{g}$ are nearly independent of drain current and gate width and their average is around the ambient temperature. The extracted values of $\textrm{G}_{ni}$ are small enough to be neglected to the circuit characteristics. From the comparison of the noise model with only $\textrm{G}_{no}$ and that having $\textrm{T}_{g}$, $\textrm{G}_{ni}$ and $\textrm{G}_{no}$ to the measured data it is fund that even the former model is in good agreement with the measured noise parameters. Thus, from a practical point of view the noise model having only the drain current noise source is confirmed as a scalable bias-dependent model.

• Journal of Korea Water Resources Association
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• v.43 no.8
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• pp.709-720
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• 2010

This paper describes the modeling of climate change impact on drought using a conceptual soil moisture model and presents the results of the modeling approach. The future climate series is obtained by scaling the historical series, informed by CCCma CGCM3-T63 with A2 green house emission scenario, using a daily scaling method that considers changes in the future monthly precipitation and potential evapotranspiration as well as in the daily precipitation distribution. The majority of the modeling results indicate that there will be more frequent drought in Korea in the future.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.5
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• pp.955-960
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• 2007

In this paper, the deviation of tunneling current for gate voltage has been investigated in double gate MOSFET developed to decrease the short channel effects. In device scaled to nano units, the tunneling current is very important current factor and rapidly increases,compared with thermionic emission current according to device size scaled down. We consider the change of tunneling current according to gate voltage in this study. The potential distribution is derived to observe the change of tunneling current according to gate voltage, and the deviation of off-current is derived from the relation of potential distribution and tunneling probability. The derived current is compared with the termionic emission current, and the relation of effective gate voltage to decrease tunneling current is obtained.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.10
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• pp.921-932
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• 2016

In this paper, a modified FSA(Frequency Scaling Algorithm) is proposed for KOMPSAT-5 high-resolution SAR image generation. In order to enhance performance of azimuth compression, degraded in sub-aperture processing due to the imperfect geometric parameter of data acquisition, the full-aperture signal processing algorithm is designed based on the exact time-frequency analysis. In addition, an azimuth scaling function is newly devised to make the full-aperture processing algorithm suitable for KOMPSAT-5 sliding-spotlight mode. Different from the previous sub-aperture FSA schemes, the suggested technique could accommodate the merit of unified signal processing structure regardless of operational modes of KOMPSAT-5. Through the point target simulation, it is verified that the suggested algorithm provides superior performance of azimuth compression over the existing full-aperture processing methods. The experimental results using real data acquired by KOMPSAT-5 are also given to demonstrate the effectiveness of our scheme as well.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.15 no.1
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• pp.165-170
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• 2015

The unsharp mask technique emphasize the boundary of the image by adding the boundary of the original image. This technique improves quality by emphasize its boundaries but produce rough image from image noise. The multi channel unsharp mask is possible to enhance entire contrast of the image by applying at least two channels of unsharp mask. However, There is limitations to strengthen boundaries even if the scale strongly applies the multi channel unsharp mask technique. To solve this problem, linear scaling to nonlinear scaling by applying exponential function to existing multi channel unsharp mask technique. Experimental results show enhanced contrast for desired area because of control scaling in details compared with existing unsharp mask technique.

• Journal of the Korea Computer Graphics Society
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• v.8 no.3
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• pp.9-16
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• 2002

Recently, high dynamic range (HDR) compression has attracted much attention due to the wide availability of HDR images. In this paper, we present an HDR compression method using a progressive image, which is a multi-level image representation based on a progressive mesh. An HDR image can be decomposed into a base image and a sequence of details by conversion into a progressive image. This decomposition provides a good structure to highly compress the dynamic range while preserving image details. The base image and larger details are considerably scaled down but smaller details are slightly scaled down. Experimental results show that our method successfully generates HDR compressed images without halo artifacts by controlling two intuitive parameters.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.8
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• pp.829-837
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• 2012

Direct numerical simulations were carried out for turbulent channel flows with $Re_{\tau}$ = 180, 395 and 590 to investigate the turbulent flow structure related to the Reynolds shear stress. By examining the probability density function, the second quadrant (Q2) events with the largest contribution to the mean Reynolds shear stress were identified. The change in the inclination angle of Q2 events varies with wall units in $y^+<50$ and with the channel half height in y/h > 0.5. Conditionally averaged flow fields for the Q2 event show that the flow structures associated with Reynolds shear stress are a quasi-streamwise vortex in the buffer layer and a hairpin-shaped vortex in the outer layer. Three-dimensional visualization of the distribution of high Reynolds shear stress reveals that the organization of hairpin vortices in the outer layer having a size of 1.5~3 h is associated with large-scale motions with high Reynolds shear stress in the outer layer.