Browsing by Subject "Kernel"
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Item Open Access An adaptive speckle suppression filter for medical ultrasound imaging(Institute of Electrical and Electronics Engineers, 1995-06) Karaman, M.; Kutay, M. A.; Bozdagi, G.An adaptive smoothing technique for speckle suppression in medical B-scan ultrasonic imaging is presented. The technique is based on filtering with appropriately shaped and sized local kernels. For each image pixel, a filtering kernel, which fits to the local homogeneous region containing the processed pixel, is obtained through a local statistics based region growing technique. The performance of the proposed filter has been tested on the phantom and tissue images. The results show that the filter effectively reduces the speckle while preserving the resolvable details. The simulation results are presented in a comparative way with two existing speckle suppression methods.Item Open Access Design of application specific processors for the cached FFT algorithm(IEEE, 2006-05) Atak, Oğuzhan; Atalar, Abdullah; Arıkan, Erdal; Ishebabi, H.; Kammler, D.; Ascheid, G.; Meyr, H.; Nicola, M.; Masera, G.Orthogonal frequency division multiplexing (OFDM) is a data transmission technique which is used in wired and wireless digital communication systems. In this technique, fast Fourier transformation (FFT) and inverse FFT (IFFT) are kernel processing blocks in an OFDM system, and are used for data (de)modulation. OFDM systems are increasingly required to be flexible to accommodate different standards and operation modes, in addition to being energy-efficient. A trade-off between these two conflicting requirements can be achieved by employing application-specific instruction-set processors (ASIPs). In this paper, two ASIP design concepts for the cached FFT algorithm (CFFT) are presented. A reduction in energy dissipation of up to 25% is achieved compared to an ASIP for the widely used Cooley-Tukey FFT algorithm, which was designed by using the same design methodology and technology. Further, a modified CFFT algorithm which enables a better cache utilization is presented. This modification reduces the energy dissipation by up to 10% compared to the original CFFT implementation.Item Open Access Effect of fractional Fourier transformation on time-frequency distributions belonging to the Cohen class(Institute of Electrical and Electronics Engineers, 1996-02) Özaktaş, Haldun M.; Erkaya, N.; Kutay, M. A.We consider the Cohen (1989) class of time-frequency distributions, which can be obtained from the Wigner distribution by convolving it with a kernel characterizing that distribution. We show that the time-frequency distribution of the fractional Fourier transform of a function is a rotated version of the distribution of the original function, if the kernel is rotationally symmetric. Thus, the fractional Fourier transform corresponds to rotation of a relatively large class of time-frequency representations (phase-space representations), confirming the important role this transform plays in the study of such representations.Item Open Access Effective kernel mapping for OpenCL applications in heterogeneous platforms(Institute of Electrical and Electronics Engineers, 2012-09) Albayrak, Ömer Erdil; Aktürk, İsmail; Öztürk, ÖzcanMany core accelerators are being deployed in many systems to improve the processing capabilities. In such systems, application mapping need to be enhanced to maximize the utilization of the underlying architecture. Especially in GPUs mapping becomes critical for multi-kernel applications as kernels may exhibit different characteristics. While some of the kernels run faster on GPU, others may refer to stay in CPU due to the high data transfer overhead. Thus, heterogeneous execution may yield to improved performance compared to executing the application only on CPU or only on GPU. In this paper, we propose a novel profiling-based kernel mapping algorithm to assign each kernel of an application to the proper device to improve the overall performance of an application. We use profiling information of kernels on different devices and generate a map that identifies which kernel should run on where to improve the overall performance of an application. Initial experiments show that our approach can effectively map kernels on CPU and GPU, and outperforms to a CPU-only and GPU-only approach. © 2012 IEEE.Item Open Access Kernels, inflations, evaluations, and imprimitivity of Mackey functors(Elsevier, 2008-03-01) Yaraneri, E.Let M be a Mackey functor for a finite group G. By the kernel of M we mean the largest normal subgroup N of G such that M can be inflated from a Mackey functor for G / N. We first study kernels of Mackey functors, and (relative) projectivity of inflated Mackey functors. For a normal subgroup N of G, denoting by PH, VG the projective cover of a simple Mackey functor for G of the form SH, VG we next try to answer the question: how are the Mackey functors PH / N, VG / N and PH, VG related? We then study imprimitive Mackey functors by which we mean Mackey functors for G induced from Mackey functors for proper subgroups of G. We obtain some results about imprimitive Mackey functors of the form PH, VG, including a Mackey functor version of Fong's theorem on induced modules of modular group algebras of p-solvable groups. Aiming to characterize subgroups H of G for which the module PH, VG (H) is the projective cover of the simple K over(N, -)G (H)-module V where the coefficient ring K is a field, we finally study evaluations of Mackey functors. © 2007 Elsevier Inc. All rights reserved.Item Open Access Radiation characteristics of a 2D parabolic reflector antenna excited by the H-polarized complex source(IEEE, 2002-09) Oğuzer, T.; Nosich, A. I.; Altıntaş, AyhanThe aim of this paper is to obtain accurate reference data for relatively large and realistic reflector antenna systems. We concentrate on a parabolic reflector antenna in the H-polarization case. The directive primary feed is modeled by the complex source point method and the relative accuracy of the results is verified. © 2002 IEEE.