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61.
Mohamed Slim Abbes Tahar Fakhfakh Mohamed Haddar Aref Maalej 《The International Journal of Advanced Manufacturing Technology》2007,34(3-4):211-218
The dynamic response of gearbox remains a paramount concern because of noise generation. This work is concerned with numerical
simulation of the overall dynamic behaviour of a parallel helical gear transmission. A dynamic sub-structuring method using
different types of substructure (carrying and slave) is made to determine the natural frequencies and the corresponding mode
shapes. The structure to be investigated is subdivided into components or sub-structures, which are then analyzed independently
for natural frequencies and mode shapes. A numerical model taking into account the elastic coupling between the various components
of a gearbox was developed. It allows studying and analyzing the dynamic behaviour of elastic housing in the presence of gear
process. The static transmission error is introduced as a vibratory excitation source and it is represented by time-varying
mesh stiffness. The discretization of the housing deformation energy and the kinetic energy expressions using plate finite
elements leads to constructions of the stiffness and the mass matrixes. In dynamic analyses, time-discretization based on
the Newmark method is used. The different equations governing movement of gearbox are established in a truncated modal base
deduced from the average characteristics of the structure. A gearbox example is presented, and analyzed. A presentation and
discussion of the numerical results was emphasized. The numerical results allow us to conclude on the dominant phenomena of
the overall dynamic behaviour of the gear transmission. 相似文献
62.
Laoui F. M. Balegroune F. Saib F. Charles C. Trari M. 《Journal of Materials Science: Materials in Electronics》2022,33(15):11701-11711
Journal of Materials Science: Materials in Electronics - A new hybrid single crystal was synthetized by chemical route. The binuclear complex containing N-donor ligand... 相似文献
63.
The Hand Gestures Recognition (HGR) System can be employed to facilitate communication between humans and computers instead of using special input and output devices. These devices may complicate communication with computers especially for people with disabilities. Hand gestures can be defined as a natural human-to-human communication method, which also can be used in human-computer interaction. Many researchers developed various techniques and methods that aimed to understand and recognize specific hand gestures by employing one or two machine learning algorithms with a reasonable accuracy. This work aims to develop a powerful hand gesture recognition model with a 100% recognition rate. We proposed an ensemble classification model that combines the most powerful machine learning classifiers to obtain diversity and improve accuracy. The majority voting method was used to aggregate accuracies produced by each classifier and get the final classification result. Our model was trained using a self-constructed dataset containing 1600 images of ten different hand gestures. The employing of canny's edge detector and histogram of oriented gradient method was a great combination with the ensemble classifier and the recognition rate. The experimental results had shown the robustness of our proposed model. Logistic Regression and Support Vector Machine have achieved 100% accuracy. The developed model was validated using two public datasets, and the findings have proved that our model outperformed other compared studies. 相似文献
64.
Hong Peng Sofiène Tahar Ferhat Khendek 《International Journal on Software Tools for Technology Transfer (STTT)》2003,4(2):234-245
In this paper, we compare and contrast SPIN and VIS, two widely used formal verification tools. In particular, we devote special
attention to the efficiency of these tools for the verification of communications protocols that can be implemented either
in software or hardware. As a basis of our comparison, we formally describe and verify the Asynchronous Transfer Mode Ring
(ATMR) medium access protocol using SPIN and its hardware model using VIS. We believe that this study is of particular interest
as more and more protocols, like ATM protocols, are implemented in hardware to match high-speed requirements.
Published online: 1 March 2002 相似文献
65.
Radhouane Bel Hadj Tahar Takayuki Ban Yutaka Ohya Yasutaka Takahashi 《Journal of the American Ceramic Society》1998,81(2):321-327
Metal-doped indium oxide thin films that have been prepared on glass substrates via a dip-coating method from an aqueous sol show a rapid decrease in electrical conductivity at room temperature (by approximately three orders of magnitude) when brought into contact with moist air. This observation is in contrast to the conductivities of nondoped indium oxide films that are independent of moisture. Thus, the doped films can be applied as a humidity sensor. The film thickness has no substantial effect on the sensing properties, probably because of the porous nature of the films that are prepared by a sol-gel process. To examine the effects of film morphology, a comparison between the humidity-sensing properties of the films that have been prepared from organic and aqueous sols also has been conducted. The roles of the doped metal ions are also discussed. 相似文献
66.
Hanen Chakroun Sami Sayadi Tahar Mechichi Abdelhafidh Dhouib 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2009,84(10):1527-1532
BACKGROUND: Laccases are receiving increasing attention as potential industrial enzymes in various applications. Therefore, it is important to find inexpensive and optimized media for large‐scale commercial production. The present work aims to valorize olive mill wastewater (OMW) by its use as base media for laccases production by Trametes trogii and use of the laccases produced for decolorizing textile dyes. RESULTS: A high yield of 25 120 U L?1 of laccases was obtained at an OMW:water ratio of 80:20 enriched with 2 g L?1 of urea corresponding to initial biochemical oxygen demand (BOD5), chemical oxygen demand (COD) and total phenol concentrations of 18.4, 46 and 4.6 g L?1 respectively. The partially purified laccases resulted in 85% decolorization of blue tubantin GLL 300 and black tubantin VSF 600, and 45% decolorization of blue solophenyl after 6 h of incubation. Subsequent additions of the same dye dose to the reaction mixture resulted in a very significant decrease in laccases activity after the third dye addition. CONCLUSION: The use of OMW for laccases production is a cost effective process. The laccases produced can be applied to the decolorization of textile wastewaters. Copyright © 2009 Society of Chemical Industry 相似文献
67.
68.
The competitive formation of metastable and stable phases during nonequilibrium processing of Al-Ge alloys and the corresponding
metastable phase equilibria have been investigated. For germanium concentrations in the range 30 to 50 at. pct, it is shown
that the four metastable phases can be ranked in order of decreasing stability as follows: monoclinic (P21/c), rhombohedral (R-C), orthorhombic (Pbca), and hexagonal (P6/mmm). Their formation depends not only on the transformation
temperature(e.g., the liquid undercooling), but also on the presence of appropriate heterogeneous nucleation sites. For example, the orthorhombic
phase has only been observed in amorphous films after rapid annealing/crystallization treatments. It is also shown that all
of these phases form metastable equilibria with α-aluminum only,i.e., no metastable phase equilibria appear to exist between any metastable phase and β-germanium or between any two metastable
phases. Consequently, it is not possible to draw a single metastable phase diagram that incorporates all of these phases with
phase boundaries that represent their metastable equilibria; rather, separate diagrams should be drawn for each metastable
phase. It is noted that these diagrams should extend only to the metastable phase field rather than all the way to pure germanium:
for compositions richer in germanium, the results indicate that the metastable phase forms and then remelts upon the formation
of germanium or a more stable, germanium-enriched metastable phase. Furthermore, it is proposed that this behavior is rather
general in nature. Finally, it is concluded that the production of metastable phases in bulk form, in systems such as this
where so many reactions occur simultaneously and competitively, might be impossible using solidification processing approaches.
Formerly with the Department of Materials Science and Engineering, University of Washington, Seattle, WA 98195 相似文献
69.
Abir Mchergui Tarek Moulahi Mohamed Tahar Ben Othman Salem Nasri 《International Journal of Communication Systems》2020,33(5)
Vehicular ad hoc networks (VANETs) are emergent concepts in terms of infrastructure‐less communication. The data dissemination is usually done using broadcast schemes. Data broadcast in VANETs is a challenging issue due to the high mobility vehicles and the varying density. On one hand, these vehicles have to share and disseminate the safety‐critical information, in real time, to other intended vehicles. On the other hand, the existing broadcast solutions do not succeed, till now, to fulfill VANETs requirements especially in terms of performance and QoS. In this paper, we propose a new QoS‐aware broadcast method in order to face VANETs communications challenges. We choose to adapt a concept originally devoted to mobile ad hoc networks (MANETs) and join it to other specific VANET techniques to introduce a new broadcasting protocol in the aim of optimizing QoS fulfilment. The proposed solution is fundamentally based on enhanced kinetic strategy assisted with fuzzy logic for QoS‐aware multipoint relay (MPR). The protocol efficiency is eventually tested through an experimental study and compared with existing methods. The results prove the over‐performance of the proposed solution. 相似文献
70.
Brahimi Tahar Khelifi Fouad Kacha Abdellah 《Multimedia Tools and Applications》2021,80(14):21241-21260
Multimedia Tools and Applications - In this paper, a wavelet-based multimodal compression method is proposed. The method jointly compresses a medical image and an ECG signal within a single codec,... 相似文献