Elektronika Ir Elektrotechnika 

About: Elektronika Ir Elektrotechnika is an academic journal published by Kaunas University of Technology. The journal publishes majorly in the area(s): Voltage & Computer science. It has an ISSN identifier of 1392-1215. It is also open access. Over the lifetime, 2552 publications have been published receiving 14347 citations.

Optimization of Weighted Aggregated Sum Product Assessment

Abstract: One of important parts of every computer-aided multiple criteria decision support system is selection of a proper MCDM (Multiple Criteria Decision Making) method. WSM (Weighted Sum Model) and WPM (Weighted Product Model) are analyzed in the current research. The aim of the research is to measure the accuracy of the latter methods and to propose a method to increase the ranking accuracy of alternatives. It is proposed to apply joint WASPAS (Weighted Aggregates Sum Product Assessment) method. Methodology for evaluation of accuracy, based on initial criteria values, is developed. Optimization of weighted aggregated function is suggested, that enables to reach the highest accuracy of measurement. An example of application of the proposed methodology is presented. Ill. 3, bibl. 15, tabl. 4 (in English; abstracts in English and Lithuanian). DOI: http://dx.doi.org/10.5755/j01.eee.122.6.1810

Feature Extraction and Reduction of Wavelet Transform Coefficients for EMG Pattern Classification

Abstract: Recently, wavelet analysis has proved to be one of the most powerful signal processing tools for the analysis of surface electromyography (sEMG) signals. It has been widely used in sEMG pattern classification for both clinical and engineering applications. This study investigated the usefulness of extracting sEMG features from multiple-level wavelet decomposition and reconstruction. A suitable wavelet based function was used to yield useful resolution components from the sEMG signal. The optimal sEMG resolution component was selected and then its reconstruction carried out. Throughout this process, noise and unwanted sEMG components were removed. Effective sEMG components were extracted with twenty-five state-of-the-art features in both the time domain and the frequency domain. Two criteria were deployed in the evaluation, scatter graphs and a class separation index. The experimental results show that most sEMG features extracted from the reconstructed sEMG signal of the first and second-level wavelet detail coefficients yield improved class separability in feature space. Some features extracted from the sub-signals are recommended such as the myopulse percentage rate, zero crossing, Willison amplitude and the mean absolute value. The proposed method will ensure that the classification accuracy will be as high as possible while the computational time will be as low as possible. Ill. 3, bibl. 24, tabl. 2 (in English; abstracts in English and Lithuanian). DOI: http://dx.doi.org/10.5755/j01.eee.122.6.1816

Visualization of eye gaze data using heat maps

Abstract: Usability testing is widely used today to determine, among other things, the quality of web site designs. To help the researchers, a number of techniques have been suggested for visualizing the eye tracker’s data. Using one of the most popular techniques, gaze fixations are plotted in 2-D against the stimulus image in the background. However, there is an alternative visualization technique, based on the heat map paradigm, which offers additional benefits by better separating the different levels of observation intensity. We present a modified version of this technique to facilitate visualizations by allowing the transparency of the heat map to depend on the gaze data itself. In our version, transparency is presented in either the gray scale, or employing some color scheme. The intensity is proportional to the duration of the observation. Thus, longer fixations add more transparency than shorter ones. Conversely, the least observed areas are hidden by a shadow or fog. We also propose three alternative forms for the function of the transparency distribution. One of these is a simple linear relationship, whereas the other two are nonlinear (a sum of linear and sine wave, and a Gaussian). Ill. 7, bibl. 6 (in English; summaries in English, Russian and Lithuanian).

Mean and Median Frequency of EMG Signal to Determine Muscle Force based on Time-Dependent Power Spectrum

Abstract: The analysis of EMG signals can be generally divided into three main issues, i.e., muscle force, muscle geometry and muscle fatigue. Recently, there are no universal indices that can be applied for all issues. In this paper, we modify the global fatigue indices, namely mean frequency (MNF) and median frequency (MDF), to be used as a muscle force and fatigue index. Due to a drawback of MNF and MDF that it has a non-linear relationship between muscle force and feature value, especially in large muscles and in cyclic dynamic contractions. A time-dependence of MNF and MDF (TD-MNF and TD-MDF) is computed for dynamic contractions. Subsequently, a slope of the regression line that fits maximum values of MDF (and MNF) during a number of cyclic contractions is used as a fatigue index. To be additionally used as a muscle force index, some suitable ranges of TD-MNF and TD-MDF should be selected and five effective statistical parameters including mean, median, variance, root mean square and kurtosis, were applied to the selected range. From the experiments, the performance of TD-MNF is definitely better than that of TD-MDF. The results showed that mean and median features of the selected TD-MNF series have a better linear relationship with muscle force (load level) compared to the traditional methods and have a significant difference (p<0.001) between feature values for different loading conditions. Moreover, there is a certain pattern of TD-MNF for all trials and subjects that has not been found in traditional MNF. TD-MNF is optimized when an overlapping consecutive window method is performed with a 384-sample window-size and a 192-sample window-increment. In total, mean and median features of the selected TD-MNF series can be used as a muscle force and fatigue index. In future works, the proposed method can be used instead of using multiple features for the EMG signal analysis.

Modeling of Photovoltaic Panel and Examining Effects of Temperature in Matlab/Simulink

Abstract: This study proposes general and specific modeling and simulation for Lorentz LA30-12S photovoltaic panel. This panel has monocrystalline cell technology. The panel power parameters are examined under observing different panel temperatures. It is created a special function for this system by Matlab/Simulink programmer. Also, the different solar radiation values are taken into account. The model for the proposed range of irradiance and temperature as model inputs, with the corresponding values of voltages, currents, and power as outputs is presented. Simulation results are compared by doing power calculations. The simulation results show that a photovoltaic panel output power reduces as module temperature increases. This situation is showed with Matlab/Simulink graphics. Ill. 13, bibl. 24, tabl. 1 (in English; abstracts in English and Lithuanian). http://dx.doi.org/10.5755/j01.eee.109.3.166