2007/4

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    On the Relationship between Integer Lifting and Rounding Transform
    (Společnost pro radioelektronické inženýrství, 2007-12) Prochaska, Jan; Vargic, Radoslav
    In this paper we analyze the relationship between integer Lifting scheme and Rounding transform as means to compute the wavelet transform in signal processing area. We bring some new results which better describe relationship, reversibility and equivalence of integer lifting scheme and rounding transform concept.
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    Evaluation of Measurement Performance in Averaging Quantization System with Noise
    (Společnost pro radioelektronické inženýrství, 2007-12) Kamensky, Miroslav; Kovac, Karol; Kralikova, Eva; Krammer, Anton
    Statistical description of quantization process is common in the theory of quantization. For the case of nonsubtractive dither theoretical analyses of the dithered quantizer have been confronted with experimental results. As a quantization system one-chip microcomputer with the analog-to-digital converter on a chip has been used. Generally valid criteria for dithered system performance have been practically applied for Gaussian dither. Interaction of natural noise present in the signal with an added Gaussian noise of several different disperses and influence of differential nonlinearity of the converter has been observed.
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    Blind Source Separation Using Time-Frequency Masking
    (Společnost pro radioelektronické inženýrství, 2007-12) Mohammed, Abbas; Ballal, Tarig; Grbic, Nedelko
    In blind source separation (BSS), multiple mixtures acquired by an array of sensors are processed in order to recover the initial multiple source signals. While a variety of Independent Component Analysis (ICA)-based techniques are being used, in this paper we used a newly proposed method: The Degenerate Unmixing and Estimation Technique (DUET). The method applies when sources are W-disjoint orthogonal; that is, when the time-frequency representations, of any two signals in the mixtures are disjoint sets. The method uses an online algorithm to perform gradient search for the mixing parameters, and simultaneously construct binary time-frequency masks that are used to partition one of the mixtures to recover the original source signals. Previous studies have demonstrated the robustness of the method. However, the investigation in this paper reveals significant drawbacks associated with the technique which should be addressed in the future.
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    The Use of Wavelets in Image Interpolation: Possibilities and Limitations
    (Společnost pro radioelektronické inženýrství, 2007-12) Dumic, Emil; Grgic, Sonja; Grgic, Mislav
    Discrete wavelet transform (DWT) can be used in various applications, such as image compression and coding. In this paper we examine how DWT can be used in image interpolation. Afterwards proposed method is compared with two other traditional interpolation methods. For the case of magnified image achieved by interpolation, original image is unknown and there is no perfect way to judge the magnification quality. Common approach is to start with an original image, generate a lower resolution version of original image by downscaling, and then use different interpolation methods to magnify low resolution image. After that original and magnified images are compared to evaluate difference between them using different picture quality measures. Our results show that comparison of image interpolation methods depends on downscaling technique, image contents and quality metric. For fair comparison all these parameters need to be considered.
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    Detection of Cortical Oscillations Induced by SCS Using Power Spectral Density
    (Společnost pro radioelektronické inženýrství, 2007-12) Svoboda, Lukas; Stancak, Andrej; Sovka, Pavel
    Chronic, intractable pain of lower back and lower extremity might develop as the result of unsuccessful surgery of back. This state called failed-back surgery syndrome (FBSS) cannot be effectively treated by pharmacotherapy. Electric stimulation of the dorsal spinal cord is applied to relieve the pain. According to the medical hypothesis, oscillatory activity, which might be related to the analgesic effects, may occur in the cortex during the stimulation. To confirm the presence of the SCS induced oscillations, a new method of detection was designed for this purpose. The analysis of EEG data was performed using power spectral density, confidence intervals, visualization and group statistic for its verification. Parameters of the method were experimentally optimized to maximize its reliability. During ongoing SCS, statistically significant changes were detected and localized at the stimulation frequency and/or its subharmonic or upper harmonic over central midline electrodes in eight patients.