Home About us Contact
|
Home About us Contact | ||
|
|
||
Experimental Report (experimental + report)
Selected AbstractsMolecular dynamics of the generation process of double-walled carbon nanotubes from peapodsHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 4 2006Yasushi Shibuta Abstract The generation process of a double-walled carbon nanotube (DWNT) from a "peapod" was studied by classical molecular dynamics simulation. Starting from a peapod structure, defined by five C60 molecules inside a (10,10) single-walled carbon nanotube (SWNT), polymerized fullerenes, a peanut-like structure and an almost nanotube-like structure were obtained under suitable conditions of temperature control. The mean distance between the two layers of the DWNT agreed with an experimental report that it is larger than the interlayer spacing found in multi-walled carbon nanotubes (MWNTs). In addition, the chirality dependence of the potential energy of a DWNT on the relative chirality of its constituent tubes was examined using a 6-12 Lennard-Jones potential. It was found that the potential energy depends only on the distance between the two layers, not on the relative chiralities. © 2006 Wiley Periodicals, Inc. Heat Trans Asian Res, 35(4): 254,264, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20115 [source] Methane steam reforming at microscales: Operation strategies for variable power output at millisecond contact timesAICHE JOURNAL, Issue 1 2009Georgios D. Stefanidis Abstract The potential of methane steam reforming at microscale is theoretically explored. To this end, a multifunctional catalytic plate microreactor, comprising of a propane combustion channel and a methane steam reforming channel, separated by a solid wall, is simulated with a pseudo 2-D (two-dimensional) reactor model. Newly developed lumped kinetic rate expressions for both processes, obtained from a posteriori reduction of detailed microkinetic models, are used. It is shown that the steam reforming at millisecond contact times is feasible at microscale, and in agreement with a recent experimental report. Furthermore, the attainable operating regions delimited from the materials stability limit, the breakthrough limit, and the maximum power output limit are mapped out. A simple operation strategy is presented for obtaining variable power output along the breakthrough line (a nearly iso-flow rate ratio line), while ensuring good overlap of reaction zones, and provide guidelines for reactor sizing. Finally, it is shown that the choice of the wall material depends on the targeted operating regime. Low-conductivity materials increase the methane conversion and power output at the expense of higher wall temperatures and steeper temperature gradients along the wall. For operation close to the breakthrough limit, intermediate conductivity materials, such as stainless steel, offer a good compromise between methane conversion and wall temperature. Even without recuperative heat exchange, the thermal efficiency of the multifunctional device and the reformer approaches ,65% and ,85%, respectively. © 2008 American Institute of Chemical Engineers AIChE J, 2009 [source] A theoretical study of an amorphous aluminium oxide layer used as a tunnel barrier in a magnetic tunnel junctionPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 12 2007E. S. Noh Abstract An amorphous aluminium oxide layer is assumed to be a condensed gas phase composed of (AlOx)N molecules. The total energy and the electron affinity of (AlOx)N molecules is calculated by using a DFT program. The effective tunnel barrier height in the MTJ is presumed from a difference between the work function of the ferromagnetic metal and the electron affinity of (AlOx)N molecules. By using a quantum-mechanical free electron model the TMR and the R×A product are calculated as a function of the thickness of an amorphous aluminium oxide layer in the F/I/F tunnel junction. It is inferred that the tunnel barrier width determined by subtracting 6 Å from the thickness of an amorphous aluminium oxide layer is more suitable to explain an experimental report qualitatively than the tunnel barrier width equivalent to the thickness of an amorphous aluminium oxide layer. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] How good are the Electrodes we use in PEFC?FUEL CELLS, Issue 3 2004M. Eikerling Abstract Basically, companies and laboratories implement production methods for their electrodes on the basis of experience, technical capabilities and commercial preferences. But how does one know whether they have ended up with the best possible electrode for the components used? What should be the (i) optimal thickness of the catalyst layer? (ii) relative amounts of electronically conducting component (catalyst, with support , if used), electrolyte and pores? (iii) "particle size distributions" in these mesophases? We may be pleased with our MEAs, but could we make them better? The details of excellently working MEA structures are typically not a subject of open discussion, also hardly anyone in the fuel cell business would like to admit that their electrodes could have been made much better. Therefore, we only rarely find (far from systematic) experimental reports on this most important issue. The message of this paper is to illustrate how strongly the MEA morphology could affect the performance and to pave the way for the development of the theory. Full analysis should address the performance at different current densities, which is possible and is partially shown in this paper, but vital trends can be demonstrated on the linear polarization resistance, the signature of electrode performance. The latter is expressed through the minimum number of key parameters characterizing the processes taking place in the MEA. Model expressions of the percolation theory can then be used to approximate the dependence on these parameters. The effects revealed are dramatic. Of course, the corresponding curves will not be reproduced literally in experiments, since these illustrations use crude expressions inspired by the theory of percolation on a regular lattice, whereas the actual mesoscopic architecture of MEA is much more complicated. However, they give us a flavour of reserves that might be released by smart MEA design. [source] Age-Related Increase in Atrial Fibrillation Induced by Transvenous Catheter-Based Atrial Burst Pacing: An In Vivo Rat Model of Inducible Atrial FibrillationJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 1 2010DONGZHU XU M.D. AF Rat Model Induced by Transvenous Catheter Pacing.,Introduction: Large animal models of atrial fibrillation (AF) are well established, but limited experimental reports exist on small animal models. We sought to develop an in vivo rat model of AF using a transvenous catheter and to evaluate the model's underlying characteristics. Methods and Results: Echocardiogram, surface electrocardiogram (ECG), and atrial effective refractory period (AERP) were recorded at baseline in young (3 months) and middle-aged (9 months) Wistar rats. AF inducibility and duration were measured through transvenous electrode catheter in young (n = 11) and middle-aged rats (n = 11) and middle-aged rats treated with either pilsicainide (1 mg/kg iv, n = 7) or amiodarone (10 mg/kg iv, n = 9). Degrees of interstitial fibrosis and cellular hypertrophy in the atria were assessed histologically. The P-wave duration and AERP were significantly longer and echocardiographic left atrial dimension significantly larger in middle-aged versus young rats. AF was inducible in >90% of all procedures in both untreated rat groups, whereas AF inducibility was reduced by the antiarrhythmic drugs. The AF duration was significantly longer in middle-aged than in young rats and was significantly shortened by treatment with either pilsicainide or amiodarone. Histologic analysis revealed significant increases in atrial interstitial fibrosis and cellular diameter in middle-aged versus young rats. Conclusions: Transvenous catheter-based AF is significantly longer in middle-aged than in young rats and is markedly reduced by treatment with antiarrhythmic drugs. This rat model of AF is simple, reproducible, and reliable for examining pharmacologic effects on AF and studying the process of atrial remodeling.(J Cardiovasc Electrophysiol, Vol. 21, pp. 88,93, January 2010) [source] Preface: phys. stat. sol. (c) 1/6PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2004Alexey Kavokin This volume contains some of the papers presented at the Third International Conference on Physics of Light,Matter Coupling in Nanostructures (PLMCN3) which took place in Acireale, Sicily, from 1 to 4 October 2003. This meeting was fourth in the series started by PLMCN (St. Nectaire, 2000) and continued by PLMCN1 (Rome, 2001) and PLMCN2 (Rithymnon, 2002). All four conferences had the same format (about 70 participants), similar subject scope (interface between fundamental physics of light,matter coupling phenomena and applied research on new semiconductor materials and low-dimensional structures), and the proceedings of all of them have been published in physica status solidi. During these four years, a huge progress has been achieved in the understanding of exciton,polariton effects in microcavities. From the discovery of stimulated scattering of polaritons in 1999 to the first experimental reports of polariton Bose condensation and lasing, attention to this rapidly developing research area has been increased drastically. It is clear now that realization of a new generation of opto-electronic devices, referred to as polariton devices, is a realistic task for the coming decade. To achieve this target, much work has to be done both in fundamental research on dynamics of exciton,polaritons in microcavities and experimental realization of high-quality microcavities presumably based on wide-band gap semiconductors like GaN, ZnO, ZnSe, suitable for the observation of strong exciton,light coupling at room temperature. Forty nine research teams from twelve European countries have created a Polariton Consortium aimed at integration of the European research effort towards fabrication of polariton devices. PLMCN3 was not only an international conference devoted, in particular, to the research on polariton devices, but also the first scientific meeting of this community. The PLMCN meetings since the very first one have been sponsored by the US Army European Research Office (ERO). This time, with the initiative of Jim Harvey from ERO, a special session has been organized on the devices of 21st century, where a number of intriguing ideas have been proposed on new light sources, polariton lasers, and quantum memory elements based on microcavities. A special prize for the most crazy but realizable idea has been won by Misha Portnoi (Exeter) for the concept of a white diode based on a microcavity. Each PLMCN meeting brings participants from new countries. This time, the traditionally strong participation from Japan, Russia, the European Union and the USA has been enforced by a representative delegation from Israel and two speakers from Mexico. We are looking forward for new-comers from other countries not yet involved in the PLMCN community, to join us for the next meeting to be held in St. Petersburg on 29 June,3 July 2004. Sergey Ivanov from the A. F. Ioffe Institute chairs the local Organizing Committee of this future conference. We are going to keep a unique informal and creative atmosphere being characteristic of the PLMCN meetings. We invite all those who wish to know more about light,matter coupling in solids or to present any new interesting results in this area and at the same time to enjoy the beautiful city of St. Petersburg, to contact Sergey Ivanov (ivan@beam.ioffe.rssi.ru) or myself (kavokin@lasmea.univ-bpclermont.fr). We are looking forward to welcoming you in St. Petersburg! [source] | |||||||||||||