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1.
Fakher Chaari Tahar Fakhfakh Riadh Hbaieb Jamel Louati Mohamed Haddar 《The International Journal of Advanced Manufacturing Technology》2006,27(7-8):738-746
Planetary gears are widely used in the transmissions of helicopters, automobiles, aircraft engines, etc. They have substantial
advantages such as compactness and a large torque-to-weight ratio. In this work, a plane model of a planetary gear was investigated.
The energetic Lagrange formulation was used to recover the equations of motion of the system. A modal analysis was performed,
and the influence of gyroscopic effect in particular was scrutinized. The dynamic response was computed by an iterative spectral
method. The excitation is induced by time-varying the gearmesh stiffness. The cases of a healthy planetary gear and one with
the presence of eccentricity and profile error were compared. The influence on the transmission ratio was also studied. 相似文献
2.
Modified smectitic Tunisian clays used in the formulation of high performance lubricating greases 总被引:1,自引:0,他引:1
Two smectitic Tunisian clays were organically modified by exchange reaction with dioctadecyl dimethylammonium chloride (DODMA) and hexadecyl benzyl dimethylammonium chloride (HBDMA). The resulting organoclays were used in the formulation of lubricating greases. The results of the performance tests applied to the obtained greases showed that their physicochemical and mechanical characteristics are in conformity with the extreme-pressure (EP) greases specifications. The obtained greases present good EP properties with only 0.5% EP additives. The smectitic clays used could constitute a raw material in the formulation of high performance lubricating greases. 相似文献
3.
Rejaiba Omar Hcini Fakher Nasri Maria Alzahrani Bandar Bouazizi Mohamed Lamjed Hlil E. K. Khelifi Jabeur Khirouni Kamel Dhahri Essebti 《Journal of Materials Science》2021,56(28):16044-16058
Journal of Materials Science - The CuFeCr0.5Ni0.5O4 (CFO) compound was synthesized using sol–gel reaction combustion technic. The structural analysis showed that the obtained composites have... 相似文献
4.
Bit rate announced for the future standards of telecommunication, as well as the level of integration reached are, as many factors, determining for the establishment of new applications in mobile terminals. Nowadays, mobile video streaming services are possible. Mobile users expect to receive multimedia traffic with some performance guarantees, so we must ensure the necessary quality of service during the video transmission. This paper aims at investigating quality of service issue inUmts network. More specifically, we explore the main challenge of quality of service management to dynamically optimize the distribution of load inUmts networks. Our investigation is organized in the following way. We formalize the optimization problem which is based on the graph theory and modellingUmts network as well as mobile users and applications to be used. The simulation of our optimization model show a clear improvement of the quality of service perceived by anUmts user in terms of bit rate, blocking and connection drop. 相似文献
5.
Hussain Ali Badran Ahmed Al-Maliki R. K. Fakher Alfahed Bahjat Ali Saeed A. Y. Al-Ahmad F. A. Al-Saymari Rita S. Elias 《Journal of Materials Science: Materials in Electronics》2018,29(13):10890-10903
Curcumin and other three curcuminoids (bisdemethoxycurcumin, α-chlorocurcumin and α-methylcurcumin) were synthesized. Fourier transform infrared spectroscopy, Fluorescence quantum yields, AFM analysis and image surface profiles were characterized. All compounds possessed electron donor moieties at both ends of the conjugated π-system and an electron acceptor moiety in the middle of the molecules (D-A-D system) and should exhibit different optical properties depending on substituents on the benzene rings. The third order nonlinear optical properties of the curcuminoids have been investigated by z-scan technique. The optical response was characterized by measuring the refractive index (n2) of the derivatives of curcumin using the Z-scan technique. The compounds showed negative and large nonlinear refractive index values of the order of 10?7 cm2/W and reverse saturable absorption with high values of the nonlinear absorption coefficient of the order of 10?4 cm/W. The nonlinear refractive index was found to vary with the different compound. The optical constants of the different compound films were studied and the dispersion of the refractive index was discussed in terms of the Wemple-DiDomenico single oscillator model. The photo-physical properties of these compounds are compared to those of native curcumin, in order to provide a rationale to the design of samples with molecular structures optimized for a photosensitizer. These types of materials may be considering new photonic applications. 相似文献
6.
Charguia Raihane Hcini Sobhi Hcini Fakher Bouazizi Mohamed Lamjed 《Journal of Superconductivity and Novel Magnetism》2022,35(2):603-613
Journal of Superconductivity and Novel Magnetism - In this work, the thermal, microstructural, magnetic, and optical studies for both La0.7Ca0.3CoO3 (LCCO) and La0.7Pb0.3CoO3 (LPCO) cobaltite... 相似文献
7.
Slim Frikha Mohamed Djemel Nabil Derbel 《International Journal of Control, Automation and Systems》2018,16(2):559-565
This paper presents a new adaptive neuro-sliding mode control for gantry crane as varying rope length. This control method derived from combining the sliding surfaces of three subsystem of the gantry crane (trolley position, rope length, anti-swing) to draw out two system sliding surfaces: the trolley position with the anti-swing and the rope length and the anti-swing. On the based of the sliding mode control principle, drawn out the equivalent controller and the switching controller for gantry crane. But due to the uncertain parameters-nonlinear model of gantry crane with the bound disturbances, combining the neural approximate method, defined the neural controller and the compensation controller for the difference between the equivalent controller and the neural controller for two system control inputs: trolley position and rope length. The adaptive control laws for these controllers were deduced from Lyapunov’s stable criteria to asymptotically stabilize the sliding surfaces. Simulation studies are performed to illustrate the effectiveness of the proposed control. 相似文献
8.
Mondher Frikha Sabeur Masmoudi Ahmed Ben Hamida Mohamed Chtourou 《International Journal of Speech Technology》2013,16(3):273-284
This paper introduces a neural network optimization procedure allowing the generation of multilayer perceptron (MLP) network topologies with few connections, low complexity and high classification performance for phoneme’s recognition. An efficient constructive algorithm with incremental training using a new proposed Frame by Frame Neural Networks (FFNN) classification approach for automatic phoneme recognition is thus proposed. It is based on a novel recruiting hidden neuron’s procedure for a single hidden-layer. After an initializing phase started with initial small number of hidden neurons, this algorithm allows the Neural Networks (NNs) to adjust automatically its parameters during the training phase. The modular FFNN classification method is then constructed and tested to recognize 5 broad phonetic classes extracted from the TIMIT database. In order to take into account the speech variability related to the coarticulation effect, a Context Window of Three Successive Frame’s (CWTSF) analysis is applied. Although, an important reduction of the computational training time is observed, this technique penalized the overall Phone Recognition Rate (PRR) and increased the complexity of the recognition system. To alleviate these limitations, two feature dimensionality reduction techniques respectively based on Principal Component Analysis (PCA) and Self Organizing Maps (SOM) are investigated. It is observed an important improvement in the performance of the recognition system when the PCA technique is applied. Optimal neuronal phone recognition architecture is finally derived according to the following criteria: best PRR, minimum computational training time and complexity of the BPNN architecture. 相似文献
9.
Wireless access to Internet services will become typical, rather than the exception as it is today. Such a vision presents
great demands on mobile networks. Mobile IP represents a simple and scalable global mobility solution but lacks the support
for fast handoff control and paging found in cellular telephony networks. In contrast, second- and third-generation cellular
systems offer seamless mobility support but are built on complex and costly connection-oriented networking infrastructure
that lacks the inherent flexibility, robustness, and scalability found in IP networks. This paper presents an overview and
performance comparison of two of the main micro-mobility protocols, namely Cellular IP and Hierarchical Mobile IP with regards
to the handoff process for UDP applications. The differences in the handoff quality of the two protocols are small and can
be traced to design choices within the typical model. There are however significant differences regarding the processing requirement,
routing efficiency and parameters relating to implementation and deployment. 相似文献
10.