• Title/Summary/Keyword: Transform domain

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A Study on Spectrum Moment Estimation in an Acoustic Doppler Current Profiler (ADCP에서의 스펙트럼 모멘트 추정에 관한 연구)

  • Lee, Jonggil
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.17 no.8
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    • pp.1790-1795
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    • 2013
  • The current velocity and turbulence information in each range cell can be obtained from the first and second Doppler spectrum moment estimates. However, the very widely used correlation method often called as the pulse-pair method has the inherent restrictions under the highly turbulent conditions since it does not satisfy the assumptions that the return Doppler spectrum should be symmetric and have a single peak value. Therefore, in this paper, the quality of pulse-pair estimates were compared with that of FFT estimates for problem analysis using various shapes of simulated Doppler spectra. It can be known that the pulse-pair method often yields meaningless results if the received signals are severely biased or multi-peak Doppler spectra in the Doppler frequency domain.

Key Frame Extraction and Region Segmentation-based Video Retrieval in Compressed Domain (압축영역에서의 대표프레임 추출 및 영역분할기반 비디오 검색 기법)

  • 강응관;김성주;송호근;최종수
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.24 no.9B
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    • pp.1713-1720
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    • 1999
  • This paper presents a new key frame extraction technique, for scene change detection, using the proposed AHIM (Accumulative Histogram Intersection Measure) from the DC image constructed by DCT DC coefficients in the compressed video sequence that is video compression standard such as MPEG. For fast content-based browsing and video retrieval in a video database, we also provide a novel coarse-to-fine video indexing scheme. In the extracted key frame, we perform the region segmentation as a preprocessing. First, the segmented image is projected with the horizontal direction, then we transform the result into a histogram, which is saved as a database index. In the second step, we calculate the moments and change them into a distance value. From the simulation results, the proposed method clearly shows the validity and superiority in respect of computation time and memory space, and that in conjunction with other techniques for indexing, such as color, can provide a powerful framework for image indexing and retrieval.

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Enhancing Robustness of Information Hiding Through Low-Density Parity-Check Codes

  • Yi, Yu;Lee, Moon-Ho;Kim, Ji-Hyun;Hwang, Gi-Yean
    • Journal of Broadcast Engineering
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    • v.8 no.4
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    • pp.437-451
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    • 2003
  • With the rapid growth of internet technologies and wide availability of multimedia computing facilities, the enforcement of multimedia copyright protection becomes an important issue. Digital watermarking is viewed as an effective way to deter content users from illegal distributions. In recent years, digital watermarking has been intensively studied to achieve this goal. However, when the watermarked media is transmitted over the channels modeled as the additive white Gaussian noise (AWGN) channel, the watermark information is often interfered by the channel noise and produces a large number of errors. So many error-correcting codes have been applied in the digital watermarking system to protect the embedded message from the disturbance of the noise, such as BCH codes, Reef-Solomon (RS) codes and Turbo codes. Recently, low-density parity-check (LDPC) codes were demonstrated as good error correcting codes achieving near Shannon limit performance and outperforming turbo codes nth low decoding complexity. In this paper, in order to mitigate the channel conditions and improve the quality of watermark, we proposed the application of LDPC codes on implementing a fairly robust digital image watermarking system. The implemented watermarking system operates in the spectrum domain where a subset of the discrete wavelet transform (DWT) coefficients is modified by the watermark without using original image during watermark extraction. The quality of watermark is evaluated by taking Into account the trade-off between the chip-rate and the rate of LDPC codes. Many simulation results are presented in this paper, these results indicate that the quality of the watermark is improved greatly and the proposed system based on LDPC codes is very robust to attacks.

Optimal Design of a Continuous Time Deadbeat Controller (연속시간 유한정정제어기의 최적설계)

  • Kim Seung Youal;Lee Keum Won
    • Journal of the Institute of Convergence Signal Processing
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    • v.1 no.2
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    • pp.169-176
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    • 2000
  • Deadbeat property is well established in digital control system design in time domain. But in continuous time system, deadbeat is impossible because of it's ripples between sampling points inspite of designs using the related digital control system design theory. But several researchers suggested delay elements. A delay element is made from the concept of finite Laplace Transform. From some specifications such as internal model stability, physical realizations as well as finite time settling, unknown coefficents and poles in error transfer functions with delay elements can be calulted so as to satisfy these specifications. For the application to the real system, robustness property can be added. In this paper, error transfer function is specified with 1 delay element and robustness condition is considered additionally. As the criterion of the robustness, a weighted sensitive function's $H_{infty}$ norm is used. For the minimum value of the criterion, error transfer function's poles are calculated optimally. In this sense, optimal design of the continuous time deadbeat controller is obtained.

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A Component Transformation Technique based on Model for Composition of EJB and COM+ (EJB와 COM+ 결합을 위한 모델기반 컴포넌트 변환 기법)

  • 최일우;신정은;류성열
    • Journal of KIISE:Software and Applications
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    • v.30 no.12
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    • pp.1172-1184
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    • 2003
  • At present, new techniques based on different component reference models for the integration of component and system of different platforms, such as EJB and COM+, are introduced. The operation between the components in the identical component platform is realized by the composition at the source level. In case of the different component platform, however, it is impossible to use combined components in real condition although they are components of similar domain. In this paper we proposed a solution for the composition problem by using component transformation methodology based on model between EJB and COM+ components which are different components. For the composition between EJB and COM+ components, we compared and analyzed each reference model, then proposed the Virtual Component Model which is implementation independent and the Implementation Table for the mutual conversion. Reffering to the Virtual Component Model and the Implementation Table, we can generalize each Implementation model to the Virtual Component Model, make the Virtual Component Model which is implementation independent through the virtual component modeling, transform EJB and COM+ components selectively. Proposing the effective Model Transformation method to the different component platform, we can combine EJB and COM+ components.

Information extraction of the moving objects based on edge detection and optical flow (Edge 검출과 Optical flow 기반 이동물체의 정보 추출)

  • Chang, Min-Hyuk;Park, Jong-An
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.27 no.8A
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    • pp.822-828
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    • 2002
  • Optical flow estimation based on multi constraint approaches is frequently used for recognition of moving objects. However, the use have been confined because of OF estimation time as well as error problem. This paper shows a new method form effectively extracting movement information using the multi-constraint base approaches with sobel edge detection. The moving objects anr extraced in the input image sequence using edge detection and segmentation. Edge detection and difference of the two input image sequence gives us the moving objects in the images. The process of thresholding removes the moving objects detected due to noise. After thresholding the real moving objects, we applied the Combinatorial Hough Transform (CHT) and voting accumulation to find the optimal constraint lines for optical flow estimation. The moving objects found in the two consecutive images by using edge detection and segmentation greatly reduces the time for comutation of CHT. The voting based CHT avoids the errors associated with least squares methods. Calculation of a large number of points along the constraint line is also avoided by using the transformed slope-intercept parameter domain. The simulation results show that the proposed method is very effective for extracting optical flow vectors and hence recognizing moving objects in the images.

Digital Image Watermarking Scheme in the Singular Vector Domain (특이 벡터 영역에서 디지털 영상 워터마킹 방법)

  • Lee, Juck Sik
    • Journal of the Institute of Convergence Signal Processing
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    • v.16 no.4
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    • pp.122-128
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    • 2015
  • As multimedia information is spread over cyber networks, problems such as protection of legal rights and original proof of an information owner raise recently. Various image transformations of DCT, DFT and DWT have been used to embed a watermark as a token of ownership. Recently, SVD being used in the field of numerical analysis is additionally applied to the watermarking methods. A watermarking method is proposed in this paper using Gabor cosine and sine transform as well as SVD for embedding and extraction of watermarks for digital images. After delivering attacks such as noise addition, space transformation, filtering and compression on watermarked images, watermark extraction algorithm is performed using the proposed GCST-SVD method. Normalized correlation values are calculated to measure the similarity between embedded watermark and extracted one as the index of watermark performance. Also visual inspection for the extracted watermark images has been done. Watermark images are inserted into the lowest vertical ac frequency band. From the experimental results, the proposed watermarking method using the singular vectors of SVD shows large correlation values of 0.9 or more and visual features of an embedded watermark for various attacks.

A Cell Search with Reduced Complexity in a Mobile Station of OFCDM Systems (OFCDM 시스템의 이동국에서의 복잡도 감소 셀 탐색)

  • Kim, Dae-Yong;Park, Yong-Wan
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.11 no.1
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    • pp.139-149
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    • 2007
  • Asynchronous OFCDM(Orthogonal Frequency and Code Division Multiplexing) systems must have a cell search process necessarily unlike synch개nous systems. this process is hewn initial synchronization and a three-step cell search algorithm is performed for the initial synchronization in the following three steps: OFCDM symbol timing, i.e., Fast Fourier Transform(FFT) window timing is estimated employing guard interval (GI) correlation in the first step, then the frame timing and CSSC(Cell Specific Scrambling Code) group is detected by taking the correlation of the CPICH(Common Pilot Channel) based on the property yielded by shifting the CSSC phase in the frequency domain. Finally, the CSSC phase within the group is identified in the third step. This paper proposes a modification group code with two or three block of the conventional CPICH based cell search algorithm in the second step which offers MS(Mobile Station) complexity reductions. however, the effect of the reduction complexity leads to degradation of the performance therefore, look for combination to have the most minimum degradation. the proposed block type group code with suitable combinations is the nearly sane performance as conventional group code and has a complexity reduction that is to be compared and verified through the computer simulation.

Fabrication of PEDOT:PSS/AgNW-based Electrically Conductive Smart Textiles Using the Screen Printing Method and its Application to Signal Transmission Lines (스크린 프린팅을 이용한 PEDOT:PSS/AgNW 기반 전기전도성 스마트 텍스타일의 제조 및 신호전달선으로의 적용)

  • Kang, Heeeun;Lee, Eugene;Cho, Gilsoo
    • Fashion & Textile Research Journal
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    • v.23 no.4
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    • pp.527-535
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    • 2021
  • In this study, electroconductive textiles were developed by screen-printing technology using a complex solution of PEDOT:PSS/AgNW on a polylactic acid nanofiber web. A performance evaluation was then conducted to utilize this electroconductive textile as a signal transmission line. To obtain highly conductive electroconductive textiles, this study sought to determine the optimal mixing ratio of PEDOT:PSS/AgNW. Sheet resistance was measured to evaluate the electrical properties of electroconductive textiles, Finite element-scanning electron microscopy images were then used to examine surface properties, and Fourier transform-infrared analysis was performed to evaluate chemical properties. The signal waveform characteristics of the electroconductive textile were observed using a signal generator and an oscilloscope. Radio-frequency characteristics were then evaluated to confirm frequency range, and bending tests were conducted to evaluate durability. The signal transmission lines produced in this study had a sheet resistance value of 3.30 ?/sq, and signal transmission performance was evaluated to observe that the input value of the voltage was nearly identical to the output value. In addition, S21 analysis confirmed that it was available in the frequency domain up to 35 MHz. The performances of the transmission lines were maintained after 100, 200, 500, and 1,000 repeated bending tests, and sufficient durability was confirmed.

Effects of the Geometrical Misalignment on the MTF Measurement (변조전달함수 측정에 있어 기하학적 조정 불량이 해상도에 미치는 영향)

  • Kim, Jun-Woo
    • Journal of the Korean Society of Radiology
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    • v.15 no.5
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    • pp.705-713
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    • 2021
  • The modulation transfer function (MTF) is calculated to analyze the resolution of the spatial frequency of the image acquired from the x-ray imaging system. In general, the response function of the detector acquires a line spread function (LSF) using a slit-camera, and derives a modulation transfer function through a Fourier transform. Because of the fact that the x-ray must always be incident on the center of the slit-camera, the tilt of the detector and slit-camera caused by the experimenter will affect the detector performance. In addition, if the tilt increases, the performance evaluation of the x-ray image system will be problematic. In this study, we analyzed the experimental and analytical models in the modulation transfer function, ie, the Fourier domain, based on the experimental error and analyzed the effect on the spatial frequency. Furthermore, performance evaluation is being carried out for various x-ray imaging systems, and experimental errors are indispensable, and the extent to which they can be tolerated should be reviewed.