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Microfibre reinforced cement composites reinforced with high volume fractions of carbon, steel and polypropylene fibres were tested in uniaxial tension. Composites investigated included those with only one type of fibre (mono-fibre composites) and those with two or more types of fibres (hybrid-fibre composites) in the same mix. Considerable strengthening, toughening and stiffening of the host matrix due to microfibre reinforcement were observed. In the hybrid-fibre composites, different fibres appear to act as additive phases; i.e., they maintain their individual reinforcing capabilities. The composites were also impact tested in uniaxial tension using a newly designed instrumented impact machine. When compared with static test results, considerable sensitivity to stress rate was noted; composites were found to be stronger and tougher under impact and the improvements were more pronounced at higher fibre volume fractions. The potential of these composites for use in thin sheet products and other similar applications is recognized, and the need for continued research is stressed. 相似文献
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Maher El��Arbi Mohamed Koubaa Maha Charfeddine Chokri Ben Amar 《Multimedia Tools and Applications》2011,55(3):579-600
In this paper, we propose a video watermarking algorithm which embeds different parts of a single watermark into different shots of a video under the wavelet domain. Based on a Motion Activity Analysis, different regions of the original video are separated into perceptually distinct categories according to motion information and region complexity. Thus, the localizations of the watermark are adjusted adaptively in accordance with the human visual system and signal characteristics, which makes them perceptually invisible and less vulnerable to automated removal. In addition, contrary to traditional methods where the watermark remains at a fixed position on the screen, the watermark moves along with moving objects and thus motion artefacts can be avoid. The multi-frame based extraction strategy ensures that the watermark can be correctly recovered from a very short segment of video. Individual frames extracted from the video also contain watermark information. Experimental results show that the inserted watermark is not only less perceptible but also robust against common video processing attacks. 相似文献
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This article deals with a local improvement of domain decomposition methods for 2-dimensional elliptic problems for which
either the geometry or the domain decomposition presents conical singularities. After explaining the main results of the theoretical
analysis carried out in Chniti et al. (Calcolo 45, 2008), the numerical experiments presented in this article confirm the optimality properties of the new interface conditions. 相似文献
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Chaabouni Souad Benois-pineau Jenny Tison François Ben Amar Chokri Zemmari Akka 《Multimedia Tools and Applications》2017,76(21):22527-22546
Multimedia Tools and Applications - Studies of visual attention of patients with Dementia such as Parkinson’s Disease Dementia and Alzheimer Disease is a promising way for non-invasive... 相似文献
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Martin Kirsten Juliane Meinl Katrin Schönfeld Alexander Michaelis Chokri Cherif 《应用聚合物科学杂志》2016,133(29)
The performance of carbon fibers depends on the quality of the precursor and the conditions of the thermal treatment. In detail, for a PAN precursor fiber the viscosity of a spinning dope and the draw ratio during the spinning process needs to be considered. Through wet spinning, different types of PAN precursor fibers with defined spinning parameters, including solid content, solvent content in a bath, and especially draw ratio resulting in defined cross section diameters, were fabricated and analyzed with tensile tests, density investigations, SEM, TGA‐MS, FTIR, and XRD. The results show that the mechanical properties of the fibers correlate to crystallinity. The cross section diameter is strongly related to the morphology of the fibers after thermal treatment. By extending the postdrawing of PAN fibers high tenacities were obtained at the cost of the cross section shape. In addition, TGA measurements reveal trapped residues of the wet spinning process as well as show several chemical reactions takes place at the same time at different temperatures. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43698. 相似文献
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Bouchrika Tahani Jemai Olfa Zaied Mourad Amar Chokri Ben 《Multimedia Tools and Applications》2018,77(5):5995-6016
Multimedia Tools and Applications - The vision based on hand gesture recognition is one of the key challenges in behavior understanding and computer vision. It offers to machines the possibility of... 相似文献
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Wavelet network for recognition system of Arabic word 总被引:1,自引:0,他引:1
Ridha Ejbali Mourad Zaied Chokri Ben Amar 《International Journal of Speech Technology》2010,13(3):163-174
Focusing on the development of new technologies of information, research in the speech communication field is an activity
in full expansion. Several disciplines and skills interact in order to improve performance of Human Machine Communication
Systems (HMC). In order to increase the performance of these systems, various techniques, including Hidden Markov Models (HMM)
and Neural Network (NN), are implemented. 相似文献
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Chokri Trabelsi Abbas Yongaçoglu 《International Journal of Wireless Information Networks》1995,2(3):149-163
The probability of packet success for asynchronous direct sequence code division multiple access (DS-CDMA) over the multipath fading channel is investigated under different fading conditions and for different cases. We studied the bit-to-bit dependence caused by the multipath fading and by the multiple access interference (MAI) originating from the chip and phase offsets between the desired and interfering signals. We investigated the effect of using the Gaussian versus the improved Gaussian process on the computation of probability of packet success as well as the effect of the bit-to-bit dependence within a packet. The improved Gaussian approximation provides more accurate values for the probability of bit error for any number of simultaneous users, while it also allows us to incorporate the effects of bit-to-bit dependence into the calculations of the probability of packet success.This paper was presented in part at the 17th Biennial Symposium on Communiations, Kingston, June 1994. This work was supported by a strategic grant (STR-0100720) from the Natural Sciences and Engineering Research Council (NSERC) of Canada. 相似文献