فهرست مطالب

  • Volume:4 Issue: 3, 2010
  • تاریخ انتشار: 1389/09/01
  • تعداد عناوین: 8
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  • Ahmed M. Soliman Page 1
    A generalization method is used to transform a floating resistor oscillator circuit to a family of sixteen grounded capacitor oscillators using the current conveyor (CCII) or the inverting current conveyor (ICCII) or combination of both. Two of the oscillator circuits have a floating property. A new family of sixteen oscillator circuits is generated from the known circuit using the adjoint circuit theorem. It is also shown that the oscillator under consideration leads to the generation of other known and new grounded passive element oscillators employing the differential voltage current conveyor (DVCC) and the balanced output current conveyor (BOCCII).
  • Aynaz Besharat, Emad Fatemizadeh Page 7
    In this study we created an optimized Region Of Interest (ROI) based JPEG2000 image compression algorithm for mammograms compression. The first step was to perform the standard JPEG2000 algorithm. The second step was to optimize this algorithm in different aspects which are, the type of wavelet transform, the number of decomposition levels of this transform and the quantization table for mammograms compression. Also we tried not to damage the diagnostic information in the images and keep the Peak Signal to Noise Ratio value, high. We achieved high compression ratios up to 165:1 with PSNR=47.96dB which was significantly higher than the previous results studied. At the next step we modified the optimized image compression algorithm in order to compress the mammograms with one square-shaped ROI in a way that we could compress the ROI losslessly. Therefore we could obtain a high total compression ratio and meanwhile preserve the significant medical diagnostic information. In previous studies on ROI-based 8bpp mammograms compression, the highest total CR for the ROI size of 5% and 15% of the entire image, with lossless ROI compression, were 32:1 and 12:1 respectively these values have been raised up to 49.9:1 and 21.33:1 in this study.
  • Amer Gulam Page 19
    This paper describes the development of a new generation of single phase rectifier which is used to power telecommunications equipment. A rectifier is designed in such a manner to meets with all the requirements of the telecommunications industry. A number of common single phase topologies exist that could be realized as telecommunication power supplies, however, they do not completely satisfy all the industry requirements. This paper reviews recent progress in topology, control and design aspects in single phase PFC techniques. Different switching rectifier topologies are presented for various applications. Merits and limitations of these techniques are discussed. A detailed report of an investigation in the power converter system performance is also provided.
  • Amir Hossein Zaeri, Samsul Bahari Mohd Noor, Maryam Mohd Isa, Farah Saleena Taip Page 31
    Sliding mode control (SMC) is a nonlinear controller that is used to achieve desired performance in the presence of unstructured uncertainty as a result of carelessness of parameter specification of the system. The main aim for sliding control, or also called Variable Structure Control, is to control the nonlinear plant by introducing a sliding surface. The sliding surface should be reached by making the state of system approach this level. In this paper, an integral augmented sliding mode control (SMC+I) is proposed to improve the control performance of a plant with uncertainty giving the example of bench-top helicopter and the results are compared with the results obtained from conventional sliding mode control with and without a boundary layer.
  • Nur Azman Abu, Siaw Lang Wong, Hidayah Rahmalan, Shahrin Sahib Page 37
    Orthogonal moment functions have long been used in image analysis. This paper proposes a novel approach based on 4x4 discrete orthogonal Tchebichef moment for fast and efficient image compression. The method incorporates a simplified mathematical framework technique using matrices as well as a block-wise reconstruction technique to eliminate possible occurrences of numerical instabilities at higher moment orders. Then the 4x4 Tchebichef Moment Transform and Discrete Cosine Transform have been compared. The results show that the 4x4 Tchebichef moment has significant advantages over the other technique in terms of its error reconstruction, average bit-length of Huffman codes and image quality. Moreover, Tchebichef moment provides a compact support to sub-block reconstruction for image compression. Tchebichef Moment Compression clearly performs potentially better for broader domains on real digital images and graphically generated images.
  • Saadat Jamali Arand, Karim Abbaszadeh Page 47
    The influence of arrangement, dimensions, and magnetic permeability of the magnetic flux shunts on the flux distribution and leakage reactance of the power transformers is studied in this paper by using a finite elements method and a simple modeling approach. By using magneto-static analysis and finite element method, first the flux distribution in the 2D model of a core-type three phase power transformer and then using the magnetic stored energy method the leakage reactance of the transformer windings is calculated. By studying the different models including magnetic flux shunts, the effect of the arrangement, geometric dimensions as well as the magnetic permeability of the magnetic flux shunt on the leakage reactance of the transformer are studied and some interesting results are obtained. It is shown that the variation of these parameters in the transformer model has significant effects on the leakage reactance of the transformer.
  • Farhad Mesrinejad, Leila Borooshak, Davood Mansouri Page 53
    Demands for mobile communications are drastically increasing. Nonetheless, these demands cannot be fulfilled because of the limited frequency resources available for mobile communications. More specifically, channel allocation for different uses of frequency resource has emerged a critical issue. This paper presents an adaptive sub-carrier allocation in an orthogonal frequency division multiple access (OFDMA) downlink transmission system. It also attempts to testify the high performance attitude on capacity compared to the latest available rate in other adaptive OFDMA methods, which maximizes the total system’s capacity and the total power in bit error rate (BER) constraints that are subject to proportional rate constraint (PRC). In this study the expectation value statistic scheduling was formed instead of the random numerical ordering during the first time of the sub-carrier allocation. Furthermore, this scheme was developed via rate allocation, based on the PRC scheme to allocate the channel adaptively among users. The rate of the allocation problem was also formulated to enhance the throughput.
  • Wan Nural Jawahir Hj Wan Yussof, Hans Burkhardt Page 59
    Here a fully 3D algorithm for automatic liver segmentation from CT volumetric datasets is presented. The algorithm starts by smoothing the original volume using anisotropic diffusion. The coarse liver region is obtained from the threshold process that is based on a priori knowledge. Then, several morphological operations is performed such as operating the liver to detach the unwanted region connected to the liver and finding the largest component using the connected component labeling (CCL) algorithm. At this stage, both 3D and 2D CCL is done subsequently. However, in 2D CCL, the adjacent slices are also affected from current slice changes. Finally, the boundary of the liver is refined using graph-cuts solver. Our algorithm does not require any user interaction or training datasets to be used. The algorithm has been evaluated on 10 CT scans of the liver and the results are encouraging to poor quality of images.