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71.
B. Bouzid B.Mohd. Ali M.K. Abdullah 《Photonics Technology Letters, IEEE》2003,15(9):1195-1197
An erbium-doped fiber (EDF) amplifier configured in a double-pass amplification scheme together with a midway bandpass filter is presented to provide a gain as high as 37.5 dB with a noise figure of less than 6 dB. The system provides a gain improvement of as much as 9.5 dB from the double-pass system without filter. The system also can easily be upgraded to support dense wavelength-division-multiplexing (DWDM) transmissions by using a multiwavelength filter. Using a pair of four-channel DWDM multiplexer and demultiplexer, a gain of 39.53 dB for each of the channels was achieved. At the bit-error rate of 10/sup -9/, the proposed design supports the input level as low as -43 dBm with a gain of 37 dB. This is all achieved with the EDF length of 7 m and pump power of 90 mW. 相似文献
72.
Finite element modeling of burnishing of AISI 1042 steel 总被引:2,自引:0,他引:2
W. Bouzid Saï K. Saï 《The International Journal of Advanced Manufacturing Technology》2005,25(5-6):460-465
The aim of this study is to analyze the evolution of surface roughness finished by burnishing. Burnishing is done on a surface that was initially turned or turned and then ground. In a previous work, we have defined an analytical model to determine the Rt factor of burnished surfaces in relation to the feed f, the material displacement δ and the roughness Rti of the initial surface. δ has been calculated using the Hertz contact theory which supposes that the behavior of the workpiece material is elastic. Hence, in this paper, we have defined a finite element model in which the elasto-plastic behavior of the piece is taken into account to determine the material displacement δ. This model has also permitted the calculation of the residual stresses related to the macroscopic contact geometry. Good correlations have been found between experimental and finite element results when burnishing an AISI 1042 steel. 相似文献
73.
This article aims at predicting machining performances for oblique turning in relation to tool-nose radius. A new geometric analysis for the uncut chip area is proposed as function of depth of cut, feed rate, tool-nose radius, and edge direction angle. Cutting edge is discretized into increments and average uncut chip thickness, elementary direction angle and elementary depth of cut are determined for each one. A new thermomechanical model is developed for each increment which is supposed to be an oblique machining with single cutting edge. The predicted cutting force components are in good agreement with experimental data over a wide range of cutting conditions. In particular, the effect of tool-nose radius and cutting parameters on chip geometry, cutting temperature, and cutting force components are studied. It is underlined that tool-nose radius promotes the increase in radial force, however, its influence on the other parameters is negligible. 相似文献
74.
Based on the machining tool path and the true trajectory equation of the cutting edge relative to the workpiece, the engagement region between the cutter and workpiece is analyzed and a new model is developed for the numerical simulation of the machined surface topography in a multiaxis ball-end milling process. The influence of machining parameters such as the feed per tooth, the radial depth of cut, the angle orientation tool, the cutter runout, and the tool deflection upon the topography are taken into account in the model. Based on the cutter workpiece engagement, the cutting force model is established. The tool deflections are extracted and used in the surface topography model for simulation. The predicted force profiles were compared to the measured ones. A reasonable agreement between the experimental and the predicted results was found. 相似文献
75.
Afef Bougharriou Wassila Bouzid Saï Kacem Saï 《The International Journal of Advanced Manufacturing Technology》2010,51(1-4):205-215
To reduce the irregularities of machined surface, burnishing is used as a finishing process by plastic deformation. This process does not only improve surface finish but also generates compressive residual stresses throughout the surface. In this work, an analytical study and a finite element modelling were performed to provide a fundamental understanding of the burnishing on an AISI 1042 workpiece. The analytical results were concentrated on the surface roughness and on some burnishing parameter effects. The simulations were devoted to the study of the surface profile, the residual stresses and the influence of burnishing parameters (penetration depth, feed rates, diameter of the ball of burnishing tool and initial surface quality) on surface roughness and the residual stress distribution. It has been noted that burnishing improves surface quality and introduces compressive residual stresses. These results were successfully compared to experimental data obtained in previous works. 相似文献
76.
The dicalcium phosphate dihydrate (A) reacts with glutaraldehyde (B) in aqueous solution with a yield of 95%. The resulting product (C) is chemically stable. The obtained purity is checked by UV-Visible and the structure is discussed on the basis of the Infrared absorption FTIR. The reaction mechanism is explained by the approach of the hydroxyl group (-OH) of one of the aldehyde functions (-CO) of 1.5 dipentanal with the enolic form, which stabilizes the product (C). The reversible reaction is performed by mild oxidation of the compound (C) in aqueous medium at ambient temperature. The compound (A) is generated with high efficiency. The comparative spectral and thermography study confirms this result. 相似文献
77.
78.
The diffraction efficiency of a tilted in-core fiber grating is analyzed with the scattering formalism and the first Born approximation. Without any prior physical assumptions about the shape or direction of the scattered wave, it is shown that diffraction occurs when the so-called Bragg conditions are nearly satisfied and the interaction process can be described by a pair of coupled first-order differential equations that are exactly the same as those obtained through the coupled-mode analysis. 相似文献
79.
Mohamed Anouar Ben Messaoud Aïcha Bouzid 《International Journal of Speech Technology》2016,19(1):65-73
The pitch is a crucial parameter in speech and music signals. However, due to severe noisy conditions, missing harmonics, unsuitable physical vibration, the determination of pitch presents a great challenge when desiring to get a good accuracy. In this paper, we propose a method for pitch estimation of speech and music sounds. Our method is based on the fast Fourier transform (FFT) of the multi-scale product (MP) provided by a feature auditory model of the sound signals. The auditory model simulates the spectral behaviour of the cochlea by a gammachirp filter-bank, and the out/middle ear filtering by a low-pass filter. For the two output channels, the FFT function of the MP is computed over frames. The MP is based on constituting the product of the speech and music wavelet transform coefficients at three scales. The experimental results show that our method estimates the pitch with high accuracy. Besides, our proposed method outperforms several other pitch detection algorithms in clean and noisy environments. 相似文献
80.