7294 research outputs found
Sort by
FAILURE RATE ANALYSIS OF BOEING 737 BRAKES EMPLOYING NEURAL NETWORK
Get PDFThe failure rate analysis of brake assemblies of a commercial airplane, i.e., Boeing 737, is analyzed using the artificial neural network and Weibull regression models. One-layered feed-forward back-propagation algorithm for artificial neural network whereas three parameters model for Weibull are used for the analysis. Three years of data are used for model building and validation. The results show that the failure rate predicted by neural network is closer in agreement with the actual data than the failure rate predicted by the Weibull model. Results also indicate that neural network can be effectively integrated into an aviation maintenance facility computerized material requirement planning system to forecast the number of brake assemblies needed for a given planning horizon
Dynamic Performance of a Wind Generation System with Thyristor Controlled Capacitor Compensation
Get PDFA dynamic model of a variable speed cage machine wind generation unit, including wind profile, wind turbine, induction generator, local load and transmission line connecting the grid is developed. The steady state as well as the dynamic performance of the wind energy system is explored. The performance of the system under wind gust conditions has been studied and the amount of transient injection to the grid investigated. A stabilizing control scheme which minimizes the transient injection through a thyristor controlled variable capacitance at the generator terminal is explored. PI controller with optimized gain settings is included in the control loop. The ‘optimal’ parameters of the PI controller are obtained through a pole-placement technique. The PI controlled variable capacitance strategy has demonstrated very good damping profile for the wind turbine-generator power system
A noveltime-domain technique for nonparaxial ultra short optical pulses
No full textA novel nonparaxial technique based on Pade approximant for modeling ultra short optical pulses has been discussed and verified. The characterization of the technique shows excellent performance in terms of accuracy, efficiency, and stability where the traditional paraxial time-domain beam propagation method failed to achieve. The new method is very useful and efficient for modeling long optical pulse interaction when compared to the classical finite-difference time-domain
A New Linear Group-Wise SIC multiuser Detector
Get PDFIn this work, we introduce a new linear groupwise SIC multi-user detector that can converge to either the decorrelator or the least minimum mean-square error (LMMSE) detector. We study the convergence behavior of the proposed scheme and show that the latter is equivalent to the block Gauss- Seidel iterative method if the group-detection scheme used is the decorrelator detector. Moreover, we prove that the latter is convergent if the group-detection matrix is positive definite. Our simulation results are in excellent agreement with the proposed theory
Flaw impulse response estimation in ultrasonic non-destructive evaluation using bi-cepstra
Get PDFPulse-echo measurements in ultrasonic non-destructive evaluation (NDE) are masked by the characteristics of the measuring instruments, the propagation paths taken by the ultrasonic pulses, and are considered to be corrupted by additive noise. It is assumed that the measured pulse echo is obtained by linearly convolving the defect impulse response (IR) with the measurement system response. Deconvolution operation, therefore, seeks to undo the effect of this convolution and extract the IR which is essential for defect identification. Autocorrelation (or power spectrum) deconvolution techniques are limited to the identification of minimum-phase systems. In this work, we show that higher-order cepstra can be used to deconvolve the IR of the flaw from ultrasonic echo measurements (synthetic as well as real). We also demonstrate that a deconvolution based on the use of the bi-cepstrum gives lower identification error variance when compared with the results of Wiener filtering deconvolution, specially at low signal-to-noise ratios (SNR)
Full-wave Solution of the Second Harmonic Generation Problem Using a Nonlinear FDTD Algorithm
No full textA vectorial time-domain simulator of integrated optical structures containing second order nonlinearities is presented. The simulation algorithm is based on the direct solution of nonlinear Maxwell's equations representing the propagating fields and is solved using the FDTD method. Because the proposed algorithm accounts for the full optical coefficient tensor, the inaccuracies associated with the scalar and paraxial approximations are avoided. It should find application in a wide range of device structures and in the analysis of short-pulse propagation in second order nonlinear devices
Area-Efficient High-Speed Carry Chain
No full textAn improved carry chain circuit with carry-skip capability is described. The carry-skip logic allows an arbitrarily long carry chain without the need for intermediate buffers for signal restoration, leading to an implementation that is both fast and area-efficient. The chain can flexibly accommodate technology-imposed maximum depth of NMOS transistor pull-down stack
UTILIZING EXTENSION CHARACTER ‘KASHIDA’ WITH POINTED LETTERS FOR ARABIC TEXT DIGITAL WATERMARKING
Get PDFThis paper exploits the existence of the redundant Arabic extension character, i.e. Kashida. We propose to use pointed letters in Arabic text with a Kashida to hold the secret bit ‘one’ and the un-pointed letters with a Kashida to hold ‘zero’. The method can be classified under secrecy feature coding methods where it hides secret information bits within the letters benefiting from their inherited points. This watermarking technique is found attractive too to other languages having similar texts to Arabic such as Persian and Urdu
