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郭勳星 全北大學校 1989 論文集 Vol.31 No.-
The discrete cosine transform(DCT) has been widely used in digital image processing because of its nearly optimal performance. For computational requirements, efficient methods reported for DCT are the Algorithms proposed by chen et al[11] and by Hein et al [2]. The CMT, called the conversion matrix transform has the following properties. 1. The conversion matrix has sparse block diagonal structure. 2. The conversion matrix has only integers as its elements. Only integer arithmetic is involved. 3. Its performance is very close to the DCT. The hardware requirements and implementation are also presented for the CMT. Because of the integer arithmetic, computationally it is much simpler. Image coding for the GIRL is simulated and performance measurements for the various discrete transforms are compared. The CMT is found to yield almost the same picture quality.
郭勳星 全北大學校 1982 論文集 Vol.24 No.-
This paper represents a computer program for the digital filter design. The computer algorithm gives the coefficients of an IIR digital filter with lowpass or highpass characteristic for any of the two types, Butterworth and Chebyshev. The bilinear method is used for transforming the analog filter into a digital filter. This program works perfectly for the filters upto a maximum order 15, basically because of the arithmetic errors encounted in evaluating the coefficients.
郭勳星 전북대학교 공업기술연구소 1987 工學硏究 Vol.18 No.-
The rapid transform is used in the recognition of korean characters. The test pattern is represented by two gray levels (0 and 1). A 2-dimensional rapid transform of the test pattern is computed. Feature selection is carried out in the rapid transform domain. These features are used with the corresponding features of the template patterns in features of the template patterns in computing the Euclidian distance function and the decision is made based on the minimum distance criterion and bit reverse techniques. The recognition algorithm is simulated on the digital computer. Experimental results show that recognition rate is 94%.
2階 RC 能動濾波器의 Ripple R에 對한 Sensitivity의 影響
郭勳星 전북대학교 공업기술연구소 1977 工學硏究 Vol.7 No.-
Recently, many reports have been presented for evaluation the sensitivity of RC active filter parameters to variations in the amplifier gain, or in the filter's resistors and capacitors. This paper introduces the ripple R that is the difference between maximum and minimum value of a function ΔG(ω)/G(ω) and derives the variation of the magnitude of the second order RC active filter as a function of w_0 and Q-Sensitivity. The function ripple R of w_0-and Q-sensitivity is a complicated form for practical application. When the Q is high, the function approximated into a simple form. In the case, the effect of w_0-Sensitivity is 2Q times stronger than that of Q-Sensitivity. If the value of Q is getting higher, the effect of Q-Sensitivity may be neglected. In the last case, we know that the practical filters are designed by w_0-Sensitivity's consideration.
郭勳聖,金煥溶 전북대학교 공업기술연구소 1981 工學硏究 Vol.11 No.-
In the digital filter design, an important factor is the word length necessary to implement the filter. In this paper, an estimate of the word length was defined such that the magnitude of the system function was maintained within a prescribed error. A procedure was also presented for minimizing this word length for realization of a give filter. In order to compute the values W_P and W_S, we calculated the maximum error in passband and stopband frequencies. These frequencies were determined by elliptic functions. Three examples were given and improvements of 1.5 bits in the word length were observed. We also investigated and compared word length according to the filter structure.
郭勳星,金英百 全北大學校 1981 論文集 Vol.23 No.-
A rational approximation procedure for digital filter design is presented in this paper. More specially, an explicit expression for the designed filter transfer function can be obtained once a rational approximation for the analytic part of the Fourier series expansion of the desired filter characteristic is determined. To demonstrate the efficiency of this technique, we derive a two-sided Pade´ approximation from the one-sided Pade´ approximant. Two examples are given to illustrate this design procedure.