• Title/Summary/Keyword: frequency invariant

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Efficient Korean Character Recognition using Partial Distortion Invariant MACE Composite Filter (제한된 왜곡불변 MACE 합성필터를 이용한 효율적인 한글 문자 인식)

  • 김성용;이승희;김철수;김정우;배장근;김수중
    • Journal of the Korean Institute of Telematics and Electronics B
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    • v.30B no.4
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    • pp.44-55
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    • 1993
  • In this paper, we proposed a new optical method for the efficient recognition of Korean characters. There are six filters in the proposed method which employed the concepts of amplitude-modulated phase-only filter(AMPOF) and spatial frequency modulation(SFM). Here, amplitude modulation is used to achieve improved correlation discrimination and SFM is to reduce the number of filters. We also used a simplified synthetic discriminant function(SDF) for distortion invariance of input image. In order to recognize the partial rotation invariant Korean characters, the proposed distortion invariant minimum average correlation energy (MACE) filter is synthesized SFM, partial rotation invariant filter (PRIF), AMPOF and MACE for partial rotation invariance in the frequency domain. The advantage of the proposed filters is to supress the sidelobes of cross correlation peak away from the autocorrelation peak and to produce sharp correlation peaks. We performed simulation and optical experiment for some of Korea characters using the proposed method. The results show that the proposed method has more improved discriminant ability and reduced processing time than the conventional methods.

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Digital Filter Design using the Symbol Pulse Invariant Transformation

  • ;Rokuya Ishii
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.19 no.1
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    • pp.1-9
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    • 1994
  • In general, when IIR digital filter are designed from analog filters, the bilinera transformation and the impluse invariant tramsformation are commonly used. It is known, however, that high frequency response of digital filters designed by these transformations can not be well approximated to the sampled analog signals. In this paper, the symbol pulse invariant transformation is analyzed theoretically so that the symbol pulse invariant transformation which was originally application to a rectangular pulse is newly applied to double rate pulse signals and generic shape pulse signals. Also, the relation of spectra between a transfer function of digital filter and one of analog filter is considered. Further, we apply to design the digital high pass filters using the symbol pulse invariant transformation method.

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A theory of linear quasi-time invariant filters

  • Lee, Heyoung;Bien, Zeungnam
    • 제어로봇시스템학회:학술대회논문집
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    • 1996.10a
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    • pp.362-367
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    • 1996
  • In this paper, the eigenstructure of a class of linear time varying systems, termed as linear quasi-time invariant(LQTI) systems, is investigated. A system composed of dynamic devices such as linear time varying capacitors and resistors can be an example of the class. To effectively describe and analyze the LQTI systems, a generalized differential operator G is introduced. Then the dynamic systems described by the operator G are studied in terms of eigenvalue, frequency characteristics, stability and an extended convolution. Some basic attributes of the operator G are compared with those of the differential operator D. Also the corresponding generalized Laplace transform pair is defined and relevant properties are derived for frequency domain analysis of the systems under consideration. As an application example, a LQTI circuit is examined by using the concept of eigenstructure of LQTI system. The LQTI filter processes the sinusoidal signals modulated by some functions.

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Rotation and Translation Invariant Feature Extraction Using Angular Projection in Frequency Domain (주파수 영역에서 각도 투영법을 이용한 회전 및 천이 불변 특징 추출)

  • Lee, Bum-Shik;Kim, Mun-Churl
    • Journal of the HCI Society of Korea
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    • v.1 no.2
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    • pp.27-33
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    • 2006
  • This paper presents a new approach to translation and rotation invariant feature extraction for image texture retrieval. For the rotation invariant feature extraction, we invent angular projection along angular frequency in Polar coordinate system. The translation and rotation invariant feature vector for representing texture images is constructed by the averaged magnitude and the standard deviations of the magnitude of the Fourier transform spectrum obtained by the proposed angular projection. In order to easily implement the angular projection, the Radon transform is employed to obtain the Fourier transform spectrum of images in the Polar coordinate system. Then, angular projection is applied to extract the feature vector. We present our experimental results to show the robustness against the image rotation and the discriminatory capability for different texture images using MPEG-7 data set. Our Experiment result shows that the proposed rotation and translation invariant feature vector is effective in retrieval performance for the texture images with homogeneity, isotropy and local directionality.

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Patterns Recognition Using Translation-Invariant Wavelet Transform (위치이동에 무관한 웨이블릿 변환을 이용한 패턴인식)

  • Kim, Kuk-Jin;Cho, Seong-Won;Kim, Jae-Min;Lim, Cheol-Su
    • Journal of the Korean Institute of Intelligent Systems
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    • v.13 no.3
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    • pp.281-286
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    • 2003
  • Wavelet Transform can effectively represent the local characteristics of a signal in the space-frequency domain. However, the feature vector extracted using wavelet transform is not translation invariant. This paper describes a new feature extraction method using wavelet transform, which is translation-invariant. Based on this translation-invariant feature extraction, the iris recognition method, based on this feature extraction method, is robust to noises. Experimentally, we show that the proposed method produces super performance in iris recognition.

Wavelet circular harmonic function frequency selective joint transform correlator for rotation invariant pattern recognition (회전불변 패턴인식을 위한 WCHF-FSJTC)

  • 방준학;이하운;노덕수;김수중
    • Journal of the Korean Institute of Telematics and Electronics S
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    • v.34S no.2
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    • pp.94-103
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    • 1997
  • The WCHF-FSJTC (wavelet circular harmonic function frequency selective joint transform correlator) using th wavelet transformed CHF as the reference image in FSJTC is proposed for rotation invariant pattern recognition. Since the wavelet transform has the property of feature extraction, the proposed system can have the better DC (discrimination cpability) and the higher SNR(signal to noise ratio) compared with the conventional CHF-CJTC(circular harmonic function conventional joint transform correlator). And since the structure of the proposed system is FSJTC which can eliminate auto-correlation and cross-correlation between input images, it can eliminate false alarm caused by the overlapping among correlation peaks. The used wavelet functio is the morlet function, which is proper for the reference image used in this paper. the optimal dialation parameter and oscillation frequency of the wavelet function are also achieved with varying the parameters of the wavelet function. The computer simulation shows that the proposed system has the best performance when the dilation parameter is 0.8 and the oscillation frequency is 0.48.

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Broadband Interference Patterns in Shallow Water with Constant Bottom Slope (해저면 경사가 일정한 천해에서의 광대역 간섭 유형)

  • 오철민;오선택;나정열;이성욱
    • The Journal of the Acoustical Society of Korea
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    • v.21 no.5
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    • pp.485-493
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    • 2002
  • Broadband interference patterns are studied using ship as an acoustic source in shallow waters with varying bathymetry. Waveguide invariant index (β) indicating the pattern of constructive (or destructive) interference in range-frequency domain is derived in a waveguide with constant bottom slope based on adiabatic mode theory. Using this invariant, changes of the interference patterns resulting from the variation of bottom bathymetry are analyzed. Results of the analytic interpretation is compared with those from sea experiments and numerical simulations.

Wideband DOA Estimation with FDFIB Network (FDFIB Network를 이용한 광대역 DOA 추정)

  • Zhou, Weiwei;Wang, Yisu;Jang, Woo-Jin;Koh, Jin-Hwan
    • Proceedings of the IEEK Conference
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    • 2006.06a
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    • pp.251-252
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    • 2006
  • In this paper, we presented an extension of the broadband DOA estimation method using frequency-domain frequency-invariant beamforming (FDFIB). The technique uses FDFIB instead of conventional frequency invariant beamforming (FIB) methods. And different narrowband DOA estimation methods, MUSIC, ESPRIT, and MPM, are used respectively. A comparison is made to demonstrate that the FDFIB-MPM not only offers a better resolution than the FDFIB-MUSIC, FDFIB-ESPRIT, but also it is computationally very efficient.

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Simplification of Linear Time-Invariant Systems by Least Squares Method (최소자승법을 이용한 선형시불변시스템의 간소화)

  • 추연석;문환영
    • Journal of Institute of Control, Robotics and Systems
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    • v.6 no.5
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    • pp.339-344
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    • 2000
  • This paper is concerned with the simplification of complex linear time-invariant systems. A simple technique is suggested using the well-known least squares method in the frequency domain. Given a high-order transfer function in the s- or z-domain, the squared-gain function corresponding to a low-order model is computed by the least squares method. Then, the low-order transfer function is obtained through the factorization. Three examples are given to illustrate the efficiency of the proposed method.

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Rotation and Translation Invariant Feature Extraction Using Angular Projection in Frequency Domain (주파수 영역에서 각도 투영법을 이용한 회전 및 천이 불변 특징추출)

  • Lee, Bum-Shik;Kim, Mun-Churl
    • 한국HCI학회:학술대회논문집
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    • 2006.02a
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    • pp.699-704
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    • 2006
  • 본 논문은 회전 및 천이불변 이미지 텍스처 검색의 새로운 방식을 소개한다. 주파수 영역의 극좌표계에서 동일한 공간 주파수에서 각도 방향으로 투영을 하는 각도 투영법을 제안하며, 제안된 각도 투영법을 이용하여 주파수 영역에서 푸리에 계수이 합과 표준편차를 특징벡터로 이용한다. 각도 투영법을 쉽게 구현하기 위해 극좌표계에서 라돈변환이 수행된다. 실험 시 MPEG-7 데이터를 이용하였으며 그 결과는 여러 텍스처 이미지를 검색하는데 있어서 특징을 잘 구별해 내는 결과를 보여준다. 또한 제안된 회전 및 천이불변 특징 추출 알고리듬은 등방성 텍스처나 국부적인 방향성을 보이는 텍스처 영상 검색에도 효율적인 검색률을 보인다.

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