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11.
Synthesis and photovoltaic properties of mono-substituted quaterthiophenes bearing strong electron-withdrawing group 总被引:1,自引:0,他引:1
Abderrahim Yassar Christine Videlot Abdelhafid. Jaafari 《Solar Energy Materials & Solar Cells》2006,90(7-8):916-922
We report here on the synthesis and properties of a monosubstituted quaterthiophene derivative asymmetrically functionalized by an electron-withdrawing group using the palladium-catalyzed Stille's coupling reaction. The UV–vis absorption spectrum evidences a strong intramolecular charge transfer transition. Thus oligothiophenes act as electron donors and substituent group as acceptor. The diodes in which monosubstituted quaterthiophenes behave as organic semiconductors, exhibit a rectifying behavior. Photovoltaic measurements show moderate power conversion efficiency. 相似文献
12.
Electroabsorption modulators (eam) have proved to be very attractive both as optical sources (monolithically integrated NRZ transmitters andrz pulse generators) as well as for very fast signal processing (demultiplexing, regeneration, wavelength conversion,...). Their design criteria, technology and implementation in future networks are reviewed, and the main issues are discussed. 相似文献
13.
The silica fume (SF) is used in civil engineering, in particular for the manufacture of high performance concrete.In order to better understand the gain in strength of the concretes containing SF, the microstructural aspect has been examined.Mixtures of SF–Lime pastes present a hydraulic setting which is due to the formation of a C–S–H phase (calcium silicate hydrate). The latter is semi-crystallized. It is characterized by the lines of X-ray diffraction, hk0 such as: 3,06 Å (220), 2,80 Å (400) and 1,83 Å (040).The mix design SF–Lime paste is thus a simplified approach of that of the mixtures SF–OPC in which the main reaction is the fixation, by the SF, of lime coming from the hydration of C3S in the form of C–S–H.Tests have been carried out on two varieties of SF resulting from the same furnace with the presence of lime or Portland cement. The results show that the presence of certain impurities, by their actions on the solubility of silica plays a significant role on the evolution of the hydration of the principal components of Portland cements and the kinetics of lime fixation by the SF.Among the impurities contained in the SF, carbon delays considerably the hydration of the principal components of Portland cement (C3S and C3A) as well as the pozzolanic reactivity of the silica fume without removing it. 相似文献
14.
Moncef Hidane Olivier Lézoray Abderrahim Elmoataz 《Journal of Mathematical Imaging and Vision》2013,45(2):114-137
We propose a nonlinear multiscale decomposition of signals defined on the vertex set of a general weighted graph. This decomposition is inspired by the hierarchical multiscale (BV,L 2) decomposition of Tadmor, Nezzar, and Vese (Multiscale Model. Simul. 2(4):554–579, 2004). We find the decomposition by iterative regularization using a graph variant of the classical total variation regularization (Rudin et al, Physica D 60(1–4):259–268, 1992). Using tools from convex analysis, and in particular Moreau’s identity, we carry out the mathematical study of the proposed method, proving the convergence of the representation and providing an energy decomposition result. The choice of the sequence of scales is also addressed. Our study shows that the initial scale can be related to a discrete version of Meyer’s norm (Meyer, Oscillating Patterns in Image Processing and Nonlinear Evolution Equations, 2001) which we introduce in the present paper. We propose to use the recent primal-dual algorithm of Chambolle and Pock (J. Math. Imaging Vis. 40:120–145, 2011) in order to compute both the minimizer of the graph total variation and the corresponding dual norm. By applying the graph model to digital images, we investigate the use of nonlocal methods to the multiscale decomposition task. Since the only assumption needed to apply our method is that the input data is living on a graph, we are also able to tackle the task of adaptive multiscale decomposition of irregularly sampled data sets within the same framework. We provide in particular examples of 3-D irregular meshes and point clouds decompositions. 相似文献
15.
Mohand Amokrane Bradai Nedjemeddine Bounar Abderrahim Benabbas Abdelaziz Ati 《Journal of Materials Processing Technology》2008,200(1-3):410-415
The recharging technique by thermal spraying offers the opportunity of renovating the worn surface parts of a machine element to give it again a new technical life despite its previous degradation in service. This process has consequently interesting economic impacts. In order to improve the adherence between 100Cr6 steel deposits and the substrate material (left worn crankshafts), company SNC ATRA of Béjaïa uses at present a composite formed by (100Cr6 steel/molybdenum bond coat of 0.2 mm thick/crankshaft substrate). As a matter of fact, it is shown in the present work that the molybdenum bond coat is not appropriate since, for the 0.2 mm thickness, lateral cracks are observed in the middle of the bond coat. On the other hand, our experiment is that a deposit of 100Cr6 steel projected directly on the substrate seems more promising since no gaps or cracks were detected at the “deposit/substrate” interface of this two-material composite. Lastly, phase analysis using X-ray diffraction confirmed that during spraying process, a stable -phase (bcc) of 100Cr6 wire was transformed to a new phase of γ-phase (fcc). The coatings exhibited the higher microhardness which would contribute to increase wear resistance. 相似文献
16.
Ahcene Sadi Abderrahim Elmoataz Matthieu Toutain 《Signal, Image and Video Processing》2016,10(3):439-446
This paper presents an adaptation and extension of the shock filters on weighted graphs using the formalism of partial difference equations. This adaptation leads to new morphological operators that alternate between nonlocal dilation and nonlocal erosion filter type on graphs. Furthermore, this adaptation extends the shock filter applications to any data that can be represented by graphs. This approach is illustrated through image, data defined on region maps, and 3D point cloud processing. 相似文献
17.
Experimental investigation of a new type of interfacial instability in a reactive coextrusion process 下载免费PDF全文
Arnaud Bondon Khalid Lamnawar Abderrahim Maazouz 《Polymer Engineering and Science》2015,55(11):2542-2552
This paper deals with the study of new interfacial instabilities, called “grainy” defects, in coextrusion process of reactive multilayer polymers. The main objective was to better understand this phenomenon since no help can be found in the literature. The fundamental approach from a micro‐scale to a macro‐scale involves the study of relationships between polymer structure, processing, and interfacial properties. The influence of these parameters on the generation of “grainy” defects during coextrusion has been assessed in correlation with physicochemical properties. Through this work, rheological properties and the interfacial morphology between tie and barrier layers have been investigated by shear stress relaxation experiments and transmission electronic microscopy, respectively. Depending on the reactive polymers, the interfacial coupling was found to significantly alter the stress relaxation behavior by extending the relaxation time and generating an interfacial roughness. Hence, relations between the copolymer architecture, the relaxation process, and the interfacial morphology were established in correlation with the generation of grainy defects in coextrusion process. POLYM. ENG. SCI., 55:2542–2552, 2015. © 2015 Society of Plastics Engineers 相似文献
18.
19.
Abderrahim Bouaid 《Fuel》2007,86(16):2596-2602
Biodiesel is defined as the mono-alkyl esters of vegetable oils. Production of biodiesel has grown tremendously in European Union in the last years. Though the commercial prospects for biodiesel have also grown, there remains some concern with respect to its resistance to oxidative degradation during storage. Due to the chemical structure of biodiesel the presence of the double bond in the molecule produce a high level of reactivity with the oxygen, especially when it placed in contact with air. Consequently, storage of biodiesel over extended periods may lead to degradation of fuel properties that can compromise fuel quality.This study used samples of biodiesel prepared by the process of transesterification from different vegetable oils: high oleic sunflower oil (HOSO), high and low erucic Brassica carinata oil (HEBO and LEBO) respectively and used frying oil (UFO). These biodiesels, produced from different sources, were used to determine the effects of long storage under different conditions on oxidation stability. Samples were stored in white (exposed) and amber (not exposed) glass containers at room temperature.The study was conducted for a period of 30-months. At regular intervals, samples were taken to measure the following physicochemical quality parameters: acid value (AV), peroxide value (PV), viscosity (ν), iodine value (IV) and insoluble impurities (II). Results showed that AV, PV, ν and II increased, while IV decreased with increasing storage time of biodiesel samples. However, slight differences were found between biodiesel samples exposed and not exposed to daylight before a storage time of 12 months. But after this period the differences were significant. 相似文献
20.
Michael Knorr Fabrice Guyon Abderrahim Khatyr Magali Allain Shawkat M. Aly Antony Lapprand Daniel Fortin Pierre D. Harvey 《Journal of Inorganic and Organometallic Polymers and Materials》2010,20(3):534-543