6 sonuçlar
Arama Sonuçları
Listeleniyor 1 - 6 / 6
Yayın Adaptive extremum seeking scheme for ABS control(IEEE, 2014) Dinçmen, ErkinA sliding mode based extremum seeking algorithm is applied to the ABS control problem where the optimum slip ratio is searched online for maximum braking force in unknown road conditions. By making the parameter of the search algorithm adaptive, an adaptive extremum seeking scheme is proposed to improve the behavior of the controlled system around the optimum operating point. Simulation study is presented to illustrate the effectiveness of the methodology.Yayın A new algorithm for joint time and phase synchronization in OFDM systems(IEEE, 2000) Panayırcı, ErdalIn this paper, a computationally efficient algorithm is presented for joint maximum likelihood (ML) timing and carrier phase synchronization of OFDM systems employing M-PSK modulation scheme with additive Gaussian noise, based on the Expectation-Maximization (EM) method. A nondata-aided(NDA) scheme is considered for the joint timing and phase synchronizer which maximizes the low SNR limit of the likelihood function averaged over the MPSK signal constellation. For this, an EM algorithm is derived which estimates the timing offset and the phase rotations of each subcarrier iteratively and which converges to the true ML estimation of the unknown timing and phase. It is shown that the algorithm becomes independent of the signal-to-noise ratio for both low and high SNR cases. The algorithm is applied to the QPSK modulated OFDM systems and-it is concluded that for SNR values greater than 10 dB the convergence is achieved in first iteration and for SNR values less than 10 dB, at most in three iterations. It is also concluded that the convergence is independent of the initial starting points.Yayın Research characteristics and agenda of technology management discipline in Turkey(IEEE, 2008) Ansal, Hacer; Aygören, Huriye; Ekmekci, Cavit UmutDespite the growing importance of "Technology Management" (TM) field in advanced countries since 1990s, it is rather new for developing countries such as Turkey. Considering the diversity of needs and concerns in different countries, the evolution of TM discipline can be expected to follow different paths to include different national experiences and to consider unique national needs and concerns in relation with technology management. Therefore, to what extent this diversity is reflected in the mainstream TM research agenda is an important issue. Thus, the aim of this study is in two folds; first, to examine how the general research characteristics and agenda of TM discipline have evolved in the academic research in Turkey, and next, to what extent they have converged or diverged with the patterns of mainstream TM research in international journals, by analyzing the TM articles published by Turkish academics both in the national and international scientific journals. The findings of this research reveal that the TM discipline in Turkey indicate both divergent and convergent characteristics when compared with the results of recent studies about developed and developing countries. In addition, a significant difference is observed about how these characteristics are reflected in national and international journals.Yayın Low complexity least minimum symbol error rate based post-distortion for vehicular VLC(Institute of Electrical and Electronics Engineers Inc., 2020-10-22) Mitra, Rangeet; Miramirkhani, Farshad; Bhatia, Vimal; Uysal, MuratVehicular visible light communications (VLC) has emerged as a viable supplement for high speed next-generation vehicle to vehicle (V2V) communication systems. However, performance of a V2V-VLC link is impaired due to nonlinear transfer-characteristics of light emitting diodes (LEDs), and inter-symbol interference (ISI). In this article, a low-complexity least-squares based post-distortion algorithm is formulated over reproducing kernel Hilbert space (RKHS) for a multi-hop V2V-VLC link. The impairments encountered in V2V-VLC channels are mitigated in RKHS by a minimum symbol error-rate post-distorter using a low dimensional approximation of random Fourier features (RFF) (which is a soft approximation of the feature-map to RKHS), that facilitates computationally simple post-distortion under finite memory-budget. The convergence and the BER-performance of the proposed post-distorter is analyzed over realistic V2V VLC channels obtained via ray-tracing. From the analysis, and the presented computer-simulations, the proposed post-distorter is found to exhibit equivalent convergence characteristics and error-rate over reasonable distances, with much lower computational complexity.Yayın Joint ML timing and phase estimation in OFDM systems using the EM algorithm(IEEE, 2000) Panayırcı, Erdal; Georghiades, Costas N.In this paper, a computationally efficient algorithm is presented for joint maximum likelihood (ML) timing and carrier phase estimation of OFDM systems employing M-PSK modulation scheme with additive Gauissian noise, based on the Expectation-Maximization (EM) algorithm. A nondata-aided(NDA) scheme is considered for the joint timing and phase synchronizer which maximizes the low SNR limit of the likelihood function averaged over the M-PSK signal costellation. For this, an Ehl algorithm is derived which estimates the timing offset and the phase rotations of each subcarrier iteratively and which converges to the true ML estimation of the unknown timing and phase. It is shown that the algorithm becomes independent of the signal-to-noise ratio for both low and high SNR cases. The algorithm is applied to the QPSK modulated OFDM systems and it is concluded that for SNR values greater than 10 dB the convergence is achieved in first iteration and for SNR values less than 10 dB, at most in three iterations. It is also concluded that the convergence is independent of the initial starting points.Yayın The concept of confluence and the edge conditions for a wedge bounded by material sheets(IEEE, 2000) İdemen, Mehmet MithatThe edge conditions which dictate the asymptotic behaviour of the electromagnetic field near the edges play a crucial role in solving boundary-value problems involving boundaries having edges, in analytical studies they permit one to determine some unknown functions while in numerical investigations they enable one to improve the convergence of some processes by introducing beforehand the edge singularities into the field functions. This work is devoted to the analysis of wedge configurations bounded by material sheets having different constitutive parameters. From mathematical point of view, the problem can be reduced to 9 canonical types. These canonical types are investigated in full detail by introducing the confluence concept which permits one to reveal also the logarithmic singularities, if any.
