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41.
We investigate the transverse modal properties of cylindrical subwavelength metal-clad nanowire and micropost lasers via rigorous theoretical waveguide analysis, including the effects of finite thickness metal cladding and gain in the core. The results of this analysis show that air-metal surface guided TM01 and some hybrid surface guided modes suffer less loss but are less confined to the core, while core-metal surface guided modes are better confined to the core but suffer greater loss. An increase in the thickness of the metal cladding reduces the loss of the core-metal surface guided modes. The modal gain and confinement of the metal-clad cavity are compared to an unclad cavity. 相似文献
42.
Carole E. Baddour Cedric L. Briens Serge Bordere Didier Anglerot Patrice Gaillard 《Chemical Engineering and Processing: Process Intensification》2008,47(12):2195-2202
Since their observation in 1976 and 1991, carbon nanotubes (CNTs) have generated much interest due to their properties and potential applications. CNTs are tubular carbon molecules with remarkable mechanical, electrical, chemical and thermal properties, which make them useful in various applications. Industries producing CNTs via the fluidized bed chemical vapor deposition technique face challenges related to the size of CNT bundles. The two main challenges are agglomeration and agglomerate size distribution control. A solution to these challenges involves the use of jet mills to grind the CNT agglomerates. The goal of this study was to determine whether the nanotubes could be ground with air jets using a commercial jet mill and apply a two-parameter model to describe the grinding process. The present study has indicated that air-jet grinding of CNTs is feasible with a typical commercial jet mill. This paper presents the effect of operational parameters on the arithmetic mean diameter of the ground product. Sonic velocity through the grinding nozzles was required to obtain reasonable grinding rates and relatively narrow particle size distributions. This occurs at high air to solids feedrate ratios. Additionally, a simple attrition model can describe the grinding process in the spiral jet mill. 相似文献
43.
Didier SBILLEAU 《核技术(英文版)》2003,14(1)
We present here a general overview of electron spectroscopies from a practical point of view. The most frequently used ones are described and the type of structural information they can provide on materials is explained in relation to the physical processes on which they are based. Furthermore, we explore critically and in detail various tools that have been developed to allow a systematic solving of structures by these spectroscopies. 相似文献
44.
Wei Wei Craig A. BennettRyuzo Tanaka Gang HouMichael T. Klein Jr. Michael T. Klein 《Fuel Processing Technology》2008
The complexity of many chemical and refining reaction systems and the thus-derived tedious and time-consuming process of building the associated kinetic models have been major obstacles in the use of fundamental kinetics in the solution of chemical engineering problems. This review summarizes work aimed at removing theses obstacles. Our recent work that has led to the enhancement of the Kinetic Modeler's Toolbox (KMT) and the development of the Kinetic Model Editor (KME) presents an end-to-end solution to the kinetic modeling process, including automated feedstock modeling, reaction network construction, kinetic rate estimation, model programming, process system configurations, model customizations, compilations, model execution and results analysis. 相似文献
45.
Didier Perrin Céline Guillermain Anne Bergeret José-Marie Lopez-Cuesta Gilles Tersac 《Journal of Materials Science》2006,41(12):3593-3602
A new process of management of waste of composite materials from Sheet Moulding Compounds (SMC), as reinforcing fillers for
thermoplastic materials, including both mechanical and chemical processes is proposed in this paper. Communited SMC being
composed of coated glass fibres intimately mixed with calcium carbonate powder, their reinforcing power is low. First, the
fibrous part was increased by partial dissolution of calcium carbonate present in the crushed products SMC. Second, a process
of partial solvolysis was developed aiming at strong increasing the interfacial mechanical properties by functionalising of
SMC load incorporated into polypropylene/grafted maleic anhydride polypropylene (PP/PPgma). At this effect, we investigated a treatment with a hot triamine (diethylenetriamine, DETA) in order to create a functionalisation,
after scission of the bond ester of unsaturated polyester, as bridging amino-succinimide.The effect of this recycling way
by partial solvolysis was checked from the mechanical properties of the resulting reinforced PP/PPgma material: Although a lower of Young modulus, better yield stress and especially resilience were observed. 相似文献
46.
GI Kempen MJ van Heuvelen RH van den Brink AC Kooijman M Klein PJ Houx J Ormel 《Canadian Metallurgical Quarterly》1996,25(6):458-464
Molecular electrostatic potential (MEP) maps of certain 3-methoxy flavone derivatives having different anti-picornavirus activities have been studied. Geometries of the molecules were optimised and charge distributions computed using the AM1 molecular orbital method. Hybridization displacement charges (HDC) were combined with the L?wdin charge distributions to compute the MEP maps. Reliability of the method of computing MEP maps was tested by studying certain other molecules for which ab initio MEP results are available. The anti-picornavirus activities of the flavones have been shown to be related with negative MEP values in two regions, one near the 3-methoxy group and another in a diagonally opposite region near the substituent attached to the C7 atom of the molecules. 相似文献
47.
48.
49.
Delapasse J.S. Behbehani K. Kuangchung Tsui Klein K.W. 《IEEE transactions on bio-medical engineering》1994,41(11):1083-1091
A new self-tuning regulator for control of mean arterial blood pressure using sodium nitroprusside is presented. In addition to adapting to various patient response gains and time constants, the controller can accommodate variations in pure time delays, a problem that has not been addressed fully in previously proposed controllers. The control algorithm derivation is based on incorporating a self-turning controller with an adaptive discrete time delay compensator. The derivation, however, is general and can potentially be applied to other pharmacological agents in addition to sodium nitroprusside. The a priori information required for implementation of the controller is the estimate of the order of the patient response transfer function and the range of the pure time delay. An attractive feature of the controller is its capability to optimize the level of the infused drug during the transient phase of the control without creating an output offset. This feature tends to reduce the overall level of the infused drug. Hence, it may be useful when the cost of a drug or its long-term administration side effects is of concern, such as in the case of sodium nitroprusside 相似文献
50.
The influence of different alkali halides (LiF, LiCl. LiBr, NaF, NaCl, NaBr, KF, KCl and KBr) on α-chymotrypsin-catalysed plastein synthesis has been studied in aqueous medium at different substrate concentrations. The results showed an enhancing effect on the plastein synthesis enzyme action by the presence of salts, proportional to salt concentration, which was decreased when the substrate concentration was increased. Additionally, these facts allowed the ions to be classified as a function of their activation power (F? > Cl? > Br?: K+ > Na+ > Li+), which was in agreement with the interpretation of the Hofmeister lyotropic series. The influence of the several phenomena produced by the presence of salts in the plastein reaction, such as, salt-substrate interactions and water activity, as well as the presence of deactivated enzyme was also analysed. The obtained results showed that the substrate concentration is the most important factor, and the activating effect of salts could be simultaneously involved with both a structural change on the substrate conformation and a reduction of water activity into the reaction media, enhancing the catalytic capability of the α-chymotrypsin towards a peptide synthesis action. 相似文献