20 results
Search Results
Now showing 1 - 10 of 20
Article Citation - WoS: 12Citation - Scopus: 15Discrete Parameter-Nonlinear Constrained Optimisation of a Gear Train Using Genetic Algorithms(inderscience Enterprises Ltd, 2005) Dolen, M.; Kaplan, H.; Seireg, A.This paper investigates the optimal design of a four-stage gear train using genetic algorithms. Five different genetic encoding schemes, which incorporate various heuristic search techniques, are proposed to deal with the most critical constraints of the problem. The fitness criterion used by all genetic algorithms includes a merit function for minimising the size of the gearbox. The results show improvement in the design merit over previous approaches without reliance on the designer's interaction to avoid geometric constraint violations and facilitate the convergence.Article Citation - WoS: 1Citation - Scopus: 3Evaluation of New Codes for Spectral-Amplitude Optical Code-Division Multiple-Access Communication Systems(Spie-int Society Optical Engineering, 2004) Murugesan, K; Ravichandran, VCNew classes of codes, namely extended modified prime sequence codes (EMPSC) and difference codes, both having an ideal in-phase cross-correlation (IPCC) value of one, are suggested for spectral-amplitude-coding optical code-division multiple-access communication systems. The general structure of the system is discussed with simpler encoder and decoder architectures based on fiber Bragg gratings. Since the influence of multiuser interference can be completely removed due to ideal IPCC, the performance analyses of the proposed codes have been carried out by incorporating the effects of phase-induced intensity noise (PIIN), shot noise, and thermal noise at the receiver, employing Gaussian approximation. Assuming typical system parameters, evaluation results show that with an increase in code weight, the maximum number of accommodative users in the system can be increased as well as significant improvements in bit error probability for a given number of active users. For the same code weight, the difference codes can support a greater number of simultaneous users than the other. It is found that the effects of PIIN dominate compared to shot noise and thermal noise at large powers, whereas the effects of PIIN and shot noise are highly reduced at low powers, so that thermal noise becomes a more influential limitation factor. In comparison with earlier codes, the error performance of EMPSC is similar to that of modified quadratic congruence codes, while difference codes resemble those codes developed based on Steiner systems. (C) 2004 Society of Photo-Optical Instrumentation Engineers.Letter Citation - WoS: 22Citation - Scopus: 24A Note on Determination of Oscillation Startup Condition(Springer, 2006) Singh, VimalThere prevails a widespread notion that, given a closed-loop system, oscillation will commence and build up therein if the magnitude of loop gain is greater than unity at the frequency at which the angle of loop gain is zero degree. Three novel examples in which this notion fails are presented.Article Citation - WoS: 4Citation - Scopus: 5Roof Shape Modelling for Multiple Diffraction Loss in Cellular Mobile Communication Systems(Taylor & Francis Ltd, 2002) Kara, A; Yazgan, EThe effects of roof shapes on multiple diffraction loss in cellular mobile communication systems are investigated. Building roofs are modelled as finitely conducting wedges with different, included angles (peaked roofs). Multiple diffraction loss, a measure of diffraction loss due to multiple building geometry, is computed by using the method of UTD (uniform theory of diffraction) for 90degrees and 120degrees wedges over the communication paths oblique to building blocks. The results, compared with the absorbing edge model, 0degrees wedge, show that multiple diffraction loss decreases with increasing wedge angle.Article A Comparison of Regression, Neural Network and Fuzzy Logic Models for Estimating Chlorophyll-A Concentrations in Reservoirs(Centre Environment Social & Economic Research Publ-ceser, 2005) Chen, Ding-Geng; Soyupak, SelcukA comparison is conducted in this paper for the multiple linear regression, neural network and fuzzy logic models for their ability to estimate pseudo steady state chlorophyll-a concentrations in a very large and deep dam reservoir that exhibits high spatial and temporal variability. The utilized data set include chlorophyll-a concentrations as an indicator of primary productivity as well as several other water quality variables such as alkalinity, PO4 phosphorus, water temperature and dissolved oxygen concentrations as independent environmental variables. Using the conventional model criteria of correlation coefficient and mean square errors, the fuzzy logic model performed the best with the neural network model better than multiple linear regression model.Article On the Definition of Sequential Consistency(Elsevier Science Bv, 2005) Sezgin, A; Gopalakrishnan, GThe definition of sequential consistency is compared with an intuitive notion of correctness. That the definition is not strong enough is illustrated through a hypothetical memory system which is clearly incorrect, yet sequentially consistent. It is claimed that the reason for this is the absence of a relation between what actually happens (temporal order) and what seems to happen (logical order). A stronger version of sequential consistency is proposed. (c) 2005 Elsevier B.V. All rights reserved.Article Citation - WoS: 2Citation - Scopus: 2Sets of Random Variables With a Given Uncorrelation Structure(Elsevier Science Bv, 2001) Ostrovska, SLet xi (1),...,xi (n) be random variables having finite expectations. Denote i(k) := # {(j(1),...,j(k)): 1 less than or equal to j(1) < ... < j(k) less than or equal to n and E (l=1)pi (k) xi (fi) = (l=1)pi (k) E xi (h)}, k = 2,...,n. The finite sequence (i(2),...,i(n)) is called the uncorrelation structure of xi (1),...,xi (n). It is proved that for any given sequence of nonnegative integers (i(2),...,i(n)) satisfying 0 less than or equal to i(k) less than or equal to ((n)(k))and any given nondegenerate probability distributions P-1,...,P-n there exist random variables eta (1),...,eta (n) with respective distributions P-1,...,P-n such that (i(2),...,i(n)) is their uncorrelation structure. (C) 2001 Elsevier Science B.V. All rights reserved.Article Citation - WoS: 2Citation - Scopus: 5Scattering of Plane Waves at the Junction of Two Corrugated Half-Planes(Taylor & Francis inc, 2005) Serbest, AH; Kara, A; Lueneburg, E; Lüneburg, ErnstIn this paper, the boundary conditions given by Weinstein ( 1969) are employed to simulate two corrugated half-planes with the same slot height but different slot width. The scattering mechanism at the junction of these half-planes is investigated via the Fourier transform technique, which leads to two coupled Wiener - Hopf equations. The solution of the Wiener - Hopf system is obtained by the Daniele - Khrapkov method and some numerical results are presented about the analysis of the scattered field.Article Citation - WoS: 1Citation - Scopus: 1The Local Mobius Equation and Decomposition Theorems in Riemannian Geometry(Canadian Mathematical Soc, 2002) Fernández-López, M; García-Río, E; Kupeli, DNA partial differential equation, the local Mobius equation, is introduced in Riemannian geometry which completely characterizes the local twisted product structure of a Riemannian manifold. Also the characterizations of warped product and product structures of Riemannian manifolds are made by the local Mobius equation and an additional partial differential equation.Article Citation - WoS: 2Spectroelectrochemical Investigation of Pentacarbonyl(pyrazine)metal(0) (metal = Cr, Mo, W) Complexes of Group 6 Elements(Walter de Gruyter Gmbh, 2002) Yaman, SO; Esentürk, E; Kayran, C; Önal, AMThe electrochemical behaviour of pentacarbony l(pyrazine) metal (0) complexes of the group 6 elements was studied by cyclic voltammetry in dichloromethane-(n-Bu)(4)NBF4 solvent-electrolyte couple at -20 degreesC vs. Ag/Ag+ or SCE reference electrode. Constant potential electrolyses of the complexes were carried out at their first oxidation peak potentials and monitored in situ by UV-Vis spectrometry. Electrolysis of W(CO)(5)pz produces [W(CO)(5)pz](+) and a similar electrochemical mechanism is expected both for Cr(CO)(5)pz and Mo(CO)(5)pz complexes. In situ low temperature constant current ESR electrolysis also confirmed the production of [W(CO)(5)pz](+) after the electron transfer.
