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[IEEE 2018 IEEE 2nd International Conference on Dielectrics (ICD) - Budapest (2018.7.1-2018.7.5)] 2018 IEEE 2nd International Conference on Dielectrics (ICD) - Investigation on the pulse shape of DC corona discharges in air under varying test voltage level
摘要： A continuous condition assessment of operating equipment makes a significant contribution to the service reliability. In this context the partial discharge diagnosis is of great importance. In contrast to AC applications an established diagnostic tool for DC applications does not exist, even though diverse promising approaches, such as the time domain analysis, are identified. This finding is based on investigations, which are carried out under a constant test voltage level. Consequently, additional research, considering a varying test voltage level and its influence on the pulse shape of partial discharges, is required to reach universally valid statements. Focusing on corona discharges in air, the investigations are carried out by using an optimized broadband measuring system. Whereas the corona discharges are gained from an artificial and idealized defect at high-voltage potential, the measuring system enables to capture the pulse shape devoid of reflection and refraction processes. As characterizing pulse shape parameters, the rise time, the pulse width and the fall time are determined as well as the apparent charge and the repetition rate. The gained values are compared to each other and discussed for different test voltage levels.
关键词： pulse shape parameter,test voltage level,corona discharge,partial discharge,DC voltage
更新于2025-09-04 15:30:14
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5D Parameter Estimation of Near-Field Sources Using Hybrid Evolutionary Computational Techniques
摘要： Hybrid evolutionary computational technique is developed to jointly estimate the amplitude, frequency, range, and 2D direction of arrival (elevation and azimuth angles) of near-field sources impinging on centrosymmetric cross array. Specifically, genetic algorithm is used as a global optimizer, whereas pattern search and interior point algorithms are employed as rapid local search optimizers. For this, a new multiobjective fitness function is constructed, which is the combination of mean square error and correlation between the normalized desired and estimated vectors. The performance of the proposed hybrid scheme is compared not only with the individual responses of genetic algorithm, interior point algorithm, and pattern search, but also with the existing traditional techniques. The proposed schemes produced fairly good results in terms of estimation accuracy, convergence rate, and robustness against noise. A large number of Monte-Carlo simulations are carried out to test out the validity and reliability of each scheme.
关键词： pattern search,interior point algorithm,parameter estimation,hybrid evolutionary computational techniques,genetic algorithm,near-field sources
更新于2025-09-04 15:30:14
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Determination of optimum segmentation parameter values for extracting building from remote sensing images
摘要： Lately, with progresses in remote sensing information techniques and the growingly and unprecedented uses of its uses, remote sensing became a science that cannot be dispensed with in most ?elds and ground object extraction has turned out to be more exact. Remote sensing image of high spatial resolution gives more inconspicuous components for instance, shape, color, size. The use of the old pixel-based method of classi?cation images inevitably leads to a signi?cant sacri?cing of image classi?cation accuracy. The use of unconventional methods such as object based image analysis (OBIA) to obtain data from image of high spatial resolution becomes the focus of many researchers. The initial phase of the OBIA technique is segmentation, which is a procedure that partition an image into moderately homogeneous areas named segments. Because the conventional pixel-based method does not suit the classi?cation of remote sensing images with spatial resolution, it has been replaced by a new standard method OBIA. Choosing the parameters of segmentation is a fundamental stage in the image segmentation process, the main purpose of this research is to try to ?nd the best values or near the best values for the parameters of image segmentation. It is expected to obtain an image object that expresses the reality and therefore obtain the accuracy of the classi?cation of the satellite images if the selection of good and appropriate segmentation parameters well done. There are three parameters that have a signi?cant impact on the accuracy of the results of the segmentation must be determined their values with high precision, where they can be arranged from the lowest up, these are compactness, shape scale. Dependence on use of visual analysis alone in determining the values of these parameters is a waste of time. Consequently, in this paper, a set of segmentations was carried out utilizing the Worldview-3 image with different values for the segmentation parameters to de?ne ideal or close ideal segmentation parameters used to extracting building from remote sensing images.
关键词： Multiresolution segmentation,Optimum segmentation parameter,Segmentation quality
更新于2025-09-04 15:30:14
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An Efficient ISAR Imaging Method for Non-uniformly Rotating Targets Based on Multiple Geometry-Aided Parameters Estimation
摘要： The inverse synthetic aperture radar (ISAR) imaging for non-uniformly rotating target plays an important role in many applications. However, it always faces a serious challenge, i.e., the time-varying Doppler frequency induced by the target complex motions will degrade the quality of ISAR image seriously. Several algorithms based on motion parameter estimation have been proposed in recent years. However, most of them always suffer from the heavy computational burden and considerable propagation errors, which deteriorates the performances of algorithms and limits their practical applications. To tackle this problem, an efficient ISAR imaging algorithm is proposed for non-uniformly rotating targets based on geometry-aided the motion parameters estimation in this paper. After compensation, the ISAR echoes are modeled as the quadratic frequency modulated (QFM) signal first, then is transformed into time-chirp distribution (TCD) plane and the least square Radon transform based on TCD (LSRT-TCD) to estimate the derivative of chirp rate efficiently is proposed. To improve the estimation performance and robustness, the pre-processing and the weighted least square Radon transform (WLSRT-TCD) method are both developed. Similarly, the weighted least square Radon transform based on time-frequency distribution (WLSRT-TFD) is also proposed to estimate the chirp rate. The proposed multiple geometry-aided method can eliminate the effect of propagation error and reduce the computational complexity simultaneously. The simulated data and real-measured data results are both presented to validate the proposed method.
关键词： propagation error,time-frequency distribution (TFD),Radon transform (RT),Parameter estimation,time-chirp distribution (TCD)
更新于2025-09-04 15:30:14