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Beausir, Benoî,t,Biswas, Somjeet,Kim, Dong Ik,Tó,th, Lá,szló,S.,Suwas, Satyam Elsevier 2009 Acta materialia Vol.57 No.17
<P><B>Abstract</B></P><P>Asymmetric rolling of commercially pure magnesium was carried out at three different temperatures: room temperature, 200°C and 350°C. Systematic analysis of microstructures, grain size distributions, texture and misorientation distributions were performed using electron backscattered diffraction in a field emission gun scanning electron microscope. The results were compared with conventional (symmetric) rolling carried out under the same conditions of temperature and strain rate. Simulations of deformation texture evolution were performed using the viscoplastic self-consistent polycrystal plasticity model. The main trends of texture evolution are faithfully reproduced by the simulations for the tests at room temperature. The deviations that appear for the textures obtained at high temperature can be explained by the occurrence of dynamic recrystallization. Finally, the mechanisms of texture evolution in magnesium during asymmetric and symmetric rolling are explained with the help of ideal orientations, grain velocity fields and divergence maps displayed in orientation space.</P>
Madathil, Pramod Kandoth,Heinrich, Benoî,t,Donnio, Bertrand,Mathevet, Fabrice,Fave, Jean-Louis,Guillon, Daniel,Attias, Andre-Jean,Lee, Changjin,Kim, Tae-Dong,Lee, Kwang-Sup American Scientific Publishers 2010 Journal of Nanoscience and Nanotechnology Vol.10 No.10
<P>We report here the synthesis and characterization of novel diethynylbenzene-based liquid crystalline semiconductor (P1) for organic thin-film transistors (OTFTs). Compound P1 was synthesized by the Sonogashira coupling reaction between 2-bromo-5-(4-hexylthiophen-2-yl)thieno[3,2-b]thiophene and 1,4-bis(dodecyloxy)-2,5-diethynylbenzene. Top contact OTFTs were fabricated by spin casting with 2 wt% solution of P1 in chloroform and their best performance, which exhibited a hole mobility of 4.5 x 10(-5) cm2/Vs, was showed after annealing of the films at liquid crystalline temperature. Time-of-flight (TOF) mobility measured at liquid crystalline phase was observed to be 1.5 x 10(-6) cm2/Vs for both positive and negative carriers. These results indicate that the liquid crystallinity helps to improve the molecular packing and enhance charge mobility for P1. These advantages can be applicable to design and construct solution-processable OTFT materials for electronic applications.</P>
A Model-Based Analysis of Secure Video Transmission Based on IPSec and IPv4
Quang-Dao Van,Anne Wei,Benoît Geller,Gérard Dupeyrat 한국전자통신연구원 2005 ETRI Journal Vol.27 No.2
A promising solution to protect wired Internet networks is to use the Secure Internet Protocol (IPSec); however, this has some drawbacks, particularly on the quality of service (QoS). This paper aims at evaluating the video traffic QoS in terms of end-to-end delay and packet loss rate. Based on some basic assumptions, our analysis shows that the performance with IPSec is rapidly inferior to the IPv4 performance. We thus suggest adding some QoS parameters into IPSec in order to achieve a compromise between QoS and security.
Burschka, Julian,Brault, Vincent,Ahmad, Shahzada,Breau, Livain,Nazeeruddin, Mohammad K.,Marsan, Benoî,t,Zakeeruddin, Shaik M.,Grä,tzel, Michael The Royal Society of Chemistry 2012 ENERGY AND ENVIRONMENTAL SCIENCE Vol.5 No.3
<P>Strong scientific interests focus on the investigation of iodine-free redox couples for their application in dye-sensitized solar cells (DSCs). Recently, a disulfide/thiolate-based redox electrolyte has been proposed as a valuable alternative to the conventional I<SUB>3</SUB><SUP>−</SUP>/I<SUP>−</SUP> system due to its transparent and non-corrosive nature. In the work presented herein, we systematically studied the influence of different counter electrode materials on the photovoltaic performance of DSCs employing this promising organic redox electrolyte. Our investigations focused on understanding the importance of electrocatalytic activity and surface area of the electroactive material on the counter electrode, comparing the conventional platinum to cobalt sulfide (CoS) and poly(3,4-ethylenedioxythiophene) (PEDOT). Electrochemical Impedance Spectroscopy has been used to study in detail the interfacial charge transfer reaction at the counter electrode. By using a high surface area PEDOT-based counter electrode, we finally achieved an unprecedented power conversion efficiency of 7.9% under simulated AM1.5G solar irradiation (100 mW cm<SUP>−2</SUP>) which, to the best of our knowledge, represents the highest efficiency that has so far been reported for an organic redox couple.</P> <P>Graphic Abstract</P><P>Investigation of platinum-free electrocatalysts for disulfide-to-thiolate reduction in dye-sensitized solar cells leading to a new record efficiency of 7.9%. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2ee03005e'> </P>
Ibraikulov, Olzhas A.,Ngov, Chheng,Chá,vez, Patricia,Bulut, Ibrahim,Heinrich, Benoî,t,Boyron, Olivier,Gerasimov, Kirill L.,Ivanov, Dimitri A.,Swaraj, Sufal,Mé,ry, Sté,phane,Lecl The Royal Society of Chemistry 2018 Journal of Materials Chemistry A Vol.6 No.25
<P>The recently reported high power conversion efficiencies achieved in fluorinated polymer:fullerene solar cells have been accounted for by the presence of face-on oriented polymer backbones that enable charge transport towards the collecting electrodes. In this work, we demonstrate that, in contrast to the results of a number of reports, the face-on polymer orientation is due to the bulky side chains, rather than to aggregation in solution. This conclusion is supported by a comparative study of polymers having similar conjugated backbones but different number of fluorine atoms and different number and type of alkyl side chains. While the latter are primarily introduced to tune polymer solubility, the present in-depth thin-film morphology investigation shows that increasing the chain bulkiness favors formation of crystalline lamellae with face-on oriented backbones, independently of the degree of fluorination. By contrast, introduction of fluorine atoms is found to substantially enhance the π-stacking interactions that remain invariably strong upon blending of the polymer with fullerene. Our results demonstrate that, for the polymer family under investigation, fluorination and functionalization by bulky alkyl side chains are both needed for reaching power conversion efficiencies above 10%.</P>
Zipper-like molecular packing of donor–acceptor conjugated co-oligomers based on perylenediimide
Biniek, Laure,Schwartz, Pierre-Olivier,Zaborova, Elena,Heinrich, Benoî,t,Leclerc, Nicolas,Mé,ry, Sté,phane,Brinkmann, Martin The Royal Society of Chemistry 2015 Journal of Materials Chemistry C Vol.3 No.14
<▼1><P>The structure of perylene diimide co-oligomers used in organic photovoltaics is uncovered by TEM and GIXD on highly oriented films.</P></▼1><▼2><P>The molecular packing of a new class of perylene diimide-based acceptor–donor (A–D) co-oligomers has been investigated by combining electron diffraction and X-ray scattering methods for AD dyads and an ADA triad structure. The AD and ADA compounds form highly ordered lamellar mesophases with well-defined donor and acceptor domains. To determine the structure of the co-oligomers, highly oriented films with different orientations were prepared. Both flat-on and edge-on orientations of the lamellae were obtained by using two different alignment methods. High temperature rubbing leads to edge-on oriented lamellae with the long molecular axis of the co-oligomer oriented almost parallel to the rubbing direction. Instead, on oriented substrates of poly(tetrafluoroethylene) (PTFE), flat-on lying lamellae with the π-stacking direction oriented parallel to the PTFE chains are obtained. The structural data gathered by low dose selected area electron diffraction and high resolution transmission electron microscopy are used to establish a structural model of an AD dyad. Driven by the strong π-stacking of the PDI core, both AD and ADA co-oligomers form two similar self-assembled lamellar structures with an original zipper-like organization of the PDI blocks.</P></▼2>