Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - WoS: 32Citation - Scopus: 37Teleoperation With Kinematically Redundant Robot Manipulators With Sub-Task Objectives(Cambridge Univ Press, 2009) Nath, Nitendra; Tatlicioglu, Enver; Dawson, Darren M.In this paper, control of nonlinear teleoperator systems where both the master and slave systems are kinematically redundant robot manipulators is addressed. The controller is developed under the assumption that the user and environmental input forces arc unmeasurable. Lyapunov-based stability analysis is used to prove that the proposed controller yields asymptotic tracking results and ensures the coordination of the master and slave systems while satisfying a sub-task objective. Numerical simulation results are presented to illustrate the effectiveness of the proposed controller.Article Citation - WoS: 4Citation - Scopus: 5Query optimization: Mobile agents versus accuracy of the cost estimation(CRL Publishing, 2005) Özakar, Belgin; Morvan, F.; Hameurlaint, A.Since an increasing number of diverse sources of data and information become available through World Wide Web, the field of distributed heterogeneous query processing attracts attention of the researchers. One of the main concerns is to reduce the amount of communication and the volume of data transferred in terms of query optimization where it is a real challenge to have the statistics of the resources predictable and up-to-date. Autonomy, proactivity and mobility features of mobile agents seem promising under some conditions. In this paper we are interested in the study of the efficiency of the mobile agents in relation with the approach of the cost model used during the optimization process. We present an execution model based on mobile agents. Performance evaluation shows the efficiency intervals of the execution model according to the estimation errors and the current state of the system. The major contribution of this paper is to point out the effective use of an execution model based on mobile agents in relation with the approach of the cost model and with the query type. © 2005 CRL Publishing Ltd.Article Citation - WoS: 56Citation - Scopus: 63Processing, Characterization and Photocatalytic Properties of Cu Doped Tio2 Thin Films on Glass Substrate by Sol-Gel Technique(Elsevier Ltd., 2006) Çelik, Erdal; Gökçen, Z.; Azem, N. Funda Ak; Tanoğlu, Metin; Emrullahoğlu, O. F.The present paper describes processing, properties and photocatalytic application of Cu doped TiO2 thin films on glass substrate. Cu doped TiO2 coatings were successfully prepared on glass slide substrates using sol-gel method. The obtained solutions exhibit acidic characteristics. The phase structure, thermal, microstructure and surface properties of the coatings were characterized by using XRD, DTA/TG, SEM and AFM. Their adhesion properties and spectroscopic analysis were investigated by a scratch tester and UV-vis spectroscopy. Four different solutions were prepared by changing Cu/Ti ratios. Glass substrates were coated by solutions of Ti-alkoxide, Cu-chloride, glacial acetic acid and isopropanol. The obtained gel films were dried at 300 degrees C for 10 min and subsequently heat-treated at 500 degrees C for 5 min in air. The oxide thin films were annealed at 600 degrees C for 60min in air. TiO2, CuO, Cu4Ti, Ti3O5 and Cu3TiO4 phases were found in the coating. The organic matters were burned at temperatures between 200 and 350 degrees C and TiO2 crystallization was formed at 450 degrees C. The weight loss of the powder during process up to 600 degrees C is approximately 70%. The microstructural observations demonstrated that CuO content was led an improved surface morphology while thickness of the film and surface defects were increased in accordance with number of dipping. According to AFM results, it was found that as the Cu/Ti content increases the surface roughness of the films increases. In addition structural, thermal and microstructural results, it was found that the films of 0.73 ratio have better adhesion strength to the glass substrate among other coatings. The oxide films were found to be active for photocatalytic decomposition of metylene blue. (c) 2006 Published by Elsevier B.V.Article Citation - WoS: 27Citation - Scopus: 29Fuzzy, Ann, and Regression Models To Predict Longitudinal Dispersion Coefficient in Natural Streams(IWA Publishing, 2006) Tayfur, GökmenThis study developed fuzzy, ANN, and regression-based models to predict longitudinal dispersion coefficient in natural streams from flow discharge data. 92 sets of field data were employed to calibrate and validate the models. 63 sets of data were used for the calibration while the remaining data were used for the validation of the models. The model-prediction results revealed the superiority of the developed models over the existing equations. The developed models predicted the measured data satisfactorily with minimum errors and maximum accuracy rates. The three models had comparable performances although the fuzzy model had the highest accuracy rate (79%) and lowest mean relative error (0.85).Article Citation - WoS: 18Citation - Scopus: 31Applied Mel-Frequency Discrete Wavelet Coefficients and Parallel Model Compensation for Noise-Robust Speech Recognition(Elsevier, 2006) Tüfekçi, Zekeriya; Gowdy, John N.; Gürbüz, Sabri; Patterson, EricInterfering noise severely degrades the performance of a speech recognition system. The Parallel Model Compensation (PMC) technique is one of the most efficient techniques for dealing with such noise. Another approach is to use features local in the frequency domain, such as Mel-Frequency Discrete Wavelet Coefficients (MFDWCs). In this paper, we investigate the use of PMC and MFDWC features to take advantage of both noise compensation and local features (MFDWCs) to decrease the effect of noise on recognition performance. We also introduce a practical weighting technique based on the noise level of each coefficient. We evaluate the performance of several wavelet-schemes using the NOISEX-92 database for various noise types and noise levels. Finally, we compare the performance of these versus Mel-Frequency Cepstral Coefficients (MFCCs), both using PMC. Experimental results show significant performance improvements for MFDWCs versus MFCCs, particularly after compensating the HMMs using the PMC technique. The best feature vector among the six MFDWCs we tried gave 13.72 and 5.29 points performance improvement, on the average, over MFCCs for -6 and 0 dB SNR, respectively. This corresponds to 39.9% and 62.8% error reductions, respectively. Weighting the partial score of each coefficient based on the noise level further improves the performance. The average error rates for the best MFDWCs dropped from 19.57% to 16.71% and from 3.14% to 2.14% for -6 dB and 0 dB noise levels, respectively, using the weighting scheme. These improvements correspond to 14.6% and 31.8% error reductions for -6 dB and 0 dB noise levels, respectively. (c) 2006 Elsevier B.V. All rights reserved.Article Citation - WoS: 67Citation - Scopus: 78Chirp Group Delay Analysis of Speech Signals(Elsevier, 2007) Bozkurt, Barış; Couvreur, Laurent; Dutoit, ThierryThis study proposes new group delay estimation techniques that can be used for analyzing resonance patterns of short-term discrete-time signals and more specifically speech signals. Phase processing or equivalently group delay processing of speech signals are known to be difficult due to large spikes in the phase/group delay functions that mask the formant structure. In this study, we first analyze in detail the z-transform zero patterns of short-term speech signals in the z-plane and discuss the sources of spikes on group delay functions, namely the zeros closely located to the unit circle. We show that windowing largely influences these patterns, therefore short-term phase processing. Through a systematic study, we then show that reliable phase/group delay estimation for speech signals can be achieved by appropriate windowing and group delay functions can reveal formant information as well as some of the characteristics of the glottal flow component in speech signals. However, such phase estimation is highly sensitive to noise and robust extraction of group delay based parameters remains difficult in real acoustic conditions even with appropriate windowing. As an alternative, we propose processing of chirp group delay functions, i.e. group delay functions computed on a circle other than the unit circle in z-plane, which can be guaranteed to be spike-free. We finally present one application in feature extraction for automatic speech recognition (ASR). We show that chirp group delay representations are potentially useful for improving ASR performance. (c) 2007 Elsevier B.V. All rights reserved.Article Citation - WoS: 72Citation - Scopus: 79Artificial Neural Networks for Estimating Daily Total Suspended Sediment in Natural Streams(IWA Publishing, 2006) Tayfur, Gökmen; Güldal, VeyselEstimates of sediment loads in natural streams are required for a wide spectrum of water resources engineering problems from optimal reservoir design to water quality in lakes. Suspended sediment constitutes 75-95% of the total load. The nonlinear problem of suspended sediment estimation requires a nonlinear model. An artificial neural network (ANN) model has been developed to predict daily total suspended sediment (TSS) in rivers. The model is constructed as a three-layer feedforward network using the back-propagation algorithm as a training tool. The model predicts TSS rates using precipitation (P) data as input. For network training and testing 240 sets of data sets were used. The model successfully predicted daily TSS loads using the present and past 4 days precipitation data in the input vector with R2 = 0.91 and MAE = 34.22 mg/L. The performance of the model was also tested against the most recently developed non-linear black box model based upon two-dimensional unit sediment graph theory (2D-USGT). The comparison of results revealed that the ANN has a significantly better performance than the 2D-USGT. Investigation results revealed that the ANN model requires a period of more than 75 d of measured P-TSS data for training the model for satisfactory TSS estimation. The statistical parameter range (xmin - xmax) plays a major role for optimal partitioning of data into training and testing sets. Both sets should have comparable values for the range parameter.Conference Object Visual Planning and Urbanism in the Mid-Twentieth Century: Conference at Newcastle Upon Tyne, Uk, 11-13 September 2007(International Seminar on Urban Form, 2008) Erten, ErdemPlanning attitudes with a particular focus on visual and three-dimensional planning have been insufficiently studied in histories of modernism. This conference, sponsored by the UK Arts and Humanities Research Council, focused on ‘a strand of more practical urbanism, modernist in flavour but historically informed [which sought] to recover positive conceptions of the city and town after the perceived deprivations of the nineteenth century’. Dealing with a timespan similar to that of narratives of modernist planning which targeted a radical reformation of the city – from the CIAM doctrine codified by the Athens Charter to the de-urbanist proposals of Frank Lloyd Wright’s Broadacre City – most of the attitudes discussed in the conference papers remained critical of such radical restructuring.Article Citation - WoS: 2Citation - Scopus: 10Water and Water Vapor Sorption Studies in Poly(propylene)-Zeolite Composites(John Wiley and Sons Inc., 2003) Pehlivan, Hilal; Özmıhçı, Filiz; Tıhmınlıoğlu, Funda; Balköse, Devrim; Ülkü, SemraWater and water vapor sorption to porous poly(propylene)zeolite composites prepared by hot pressing have been studied as a function of zeolite loading. This work presents the first report on the effect of the zeolite as a filler on the water sorption properties of PP composites. Water swelling experiments were conducted at 25°C using pure PP and PP-zeolite film samples having different zeolite loadings (6-40 wt%). Since PP is a hydrophobic polymer, it does not sorp any water, but the composites having 10, 20, 30, and 40% zeolite sorbed 0.63, 1.00, 1.72 and 3.74 wt% water, respectively. The zeolite itself at the same conditions sorbed 24.5 wt% water. As the filler loading in the composites increased, equilibrium uptake values increased too. On the other hand, water vapor sorption and kinetics has been studied using a Cahn 2000 gravimetric sorption system. Within in the range 0.35-0.95%, water vapor was adsorbed by the composites containing 10-40 wt% zeolite. Experimental effective water vapor diffusivities of the composite films were about one order of magnitude higher than the experimental water diffusion coefficient in composites. The transport of water in composites was slower than that in the liquid water due to the longer diffusion pathway and adsorption on the surface of the composites. Although the liquid water may fill all the voids in the composite, water vapor is adsorbed on the surface of the zeolite only.Article Citation - WoS: 4Citation - Scopus: 5Conductance Fluctuations in Undoped Hydrogenated Amorphous Silicon-Germanium Alloy Thin Films(Elsevier Ltd., 2002) Güneş, Mehmet; Johanson, Robert E.; Kasap, Safa O.; Yang, Jeffrey C.; Guha, SubhenduWe report coplanar conductance fluctuations of device quality, undoped hydrogenated amorphous silicon-germanium alloy thin films (a-SiGe:H) measured from 430 to 490 K. The a-SiGe:H alloys produce noise power spectra similar to coplanar undoped a-Si:H films in the same temperature range. The noise power spectrum S(n) does not fit a single 1/fα power law but rather has two distinct regions, each accurately fitted by a power law, but with different slopes. The low frequency slope α1 is similar to that observed in undoped a-Si:H films varying from 1.30 to 1.46 for different Ge concentrations and shows a slight temperature dependence. At higher frequencies, the slope α2 is less than unity and temperature independent but depends on the Ge content of the film. α2 decreases from 0.60 for no Ge (pure a-Si:H) to 0.15 for 40 at.% Ge. The noise power at lower frequencies increases and at higher frequencies decreases substantially as the temperature increases from 430 to 490 K. We infer that similar noise mechanisms are operating in undoped a-SiGe:H and a-Si:H films but that the Ge content is influencing the noise, particularly the slope at higher frequencies. In addition, the noise has the expected quadratic dependence on bias current and obeys Gaussian statistics.