Position-controlled interconnected InAs nanowire networks

We demonstrate here a method for controlled production of complex self-assembled three-dimensional networks of InAs nanowires on a substrate, based on sequentially seeded epitaxial nanowire structures, or "nanotrees". A position-controlled array of trunk nanowires is first produced using lithographically defined Au particles as seeds. With these wires positioned along the proper crystallographic directions with respect to each other, nanotree branches grow toward neighboring trunks, connecting them together. Finally, we investigate the crystal structure of the interconnected nanotrees, demonstrating that branch growth after the contact with the second trunk has an epitaxial relationship to that trunk.     

Au-free epitaxial growth of InAs nanowires

III-V nanowires have been fabricated by metal-organic vapor-phase epitaxy without using Au or other metal particles as a catalyst. Instead, prior to growth, a thin SiOx layer is deposited on the substrates. Wires form on various III-V substrates as well as on Si. They are nontapered in thickness and exhibit a hexagonal cross-section. From high-resolution X-ray diffraction, the epitaxial relation between wires and substrates is demonstrated and their crystal structure is determined.     

Aerosol phase generation of In-Se nanoparticles

Results on the generation and heat treatment of In-Se nanoparticles, made by heterogeneous condensation of selenium on indium nanoparticles synthesised via the evaporation/condensation route are reported. In-situ aerosol measurements are complemented with ex-situ analysis, to provide structural, morphological, and compositional information on the In-Se nanoparticles. Our results indicate that prior to heat treatment In-Se nanoparticles have a shape in the aerosol phase, similar to an asymmetric dumbbell. The bigger particle of the dumbbell structure is made up of amorphous Se, while the overall composition of the polycrystalline smaller particle is around InSe. The smaller particle has an intrinsic structure, and consists of different InSe-compounds, with a decreasing In content towards the shell. The shape of the In-Se nanoparticles is different in the aerosol phase and on the surface of the samples. The observed variety of particle sizes and shapes on the sample surface is shown to be partly due to the agglomeration of the aerosol phase binaries (i.e., dumbbells) via coalescence on the surface of the sample and wetting of the sample surface by the Se nanoparticles. These processes make the bigger particle of the dumbbell structure appear almost perfectly hemispherical on the sample surfaces. During heat treatment at lower temperatures mainly the evaporative removal of the big Se particle of the dumbbell structure will take place. Annealing of the smaller particles starts to dominate at temperatures above 240 degrees C and makes the composition of the small particles closer to that of the thermodynamically most favoured In2Se3.     

Inductance inequalities for ideal conductors

Contents For the stationary magnetic field of a system of ideal conductors minimum theorems are given that are analogues of Thomson's and Dirichlet's principles in electrostatics. Upper and lower bounds for the inductance of an ideal conductor with one hole are derived from the minimum theorems with the aid of Schwarz's inequality. For a torus the theorems with the aid of Schwarz's inequality. For a torus the bounds are compared numerically with the true inductance.

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Induktivitätsgleichungen für ideale Letter

Übersicht Für das stationäre magnetische Feld einer Sammlung idealer Leiter werden zwei Minimalsätze gegeben, die dem Thomsonschen und dem Dirichletschen Prinzip der Elektrostatik analog sind. Obere und untere Schranke für die Induktivität eines ringartigen idealen Leiters werden aus den Minimalsätzen mit Hilfe der Schwarzschen Ungleichung abgeleitet. Für den Fall eines Torus werden die Schranken numerisch mit der wahren Induktivität verglichen.

     

Influences of polarization-mode dispersion on soliton transmissionsystems

In soliton transmission systems with polarization-mode dispersion (PMD), random birefringence causes solitons to generate dispersive waves, which degrade soliton transmission systems in two aspects. First, the dispersive waves cause solitons to continuously lose energy, thus induce pulse broadening. Second, the dispersive waves interact with other soliton pulses and cause distortion of a sequence of soliton pulses. Both of these effects induce performance degradation of soliton transmission systems. We study these effects of PMD on both conventional and dispersion-managed (DM) soliton transmission systems. We show that, for conventional soliton systems, although single pulse has robustness to PMD, the interplay between the dispersive waves and solitons would seriously distort a sequence of pulses and make soliton systems worse than linear systems if all other transmission impairments are neglected. We also show that DM solitons are more robust to PMD than both conventional solitons and linear systems due to the enhanced nonlinearity and less sensitivity of DM solitons to perturbations. We further point out that soliton collision-induced polarization scattering causes additional timing jitter and system performance penalty in WDM soliton systems     

THE DEPENDENCE OF PAPER MACHINE DRYING DRYING CHARACTERISTIC ON THE MACHINE GEOMETRY

ABSTRACT

The effect of the dryer cylinder diameter on the dryer specific evaporation rate is examined theoretically. It is observed that, in the range of cylinder diameters applicable in practice, the dryer specific evaporation rate is nearly independent of the selected cylinder diameter when the dryer geometry remains unchanged. In practice, however, the dryer geometries have changed slightly according to the cylinder diameter.

TO clarify the effects of the various component factors pertaining to the dryer geometry, this paper presents a drying characteristic, i.e.. a curve showing the dependence of the drying rate on the condensing steam temperature. The drying characteristic is given in the form of a nomogram to facilitate the evaluation of the effect of the ratio between the free draw length and the cylinder diameter, and the wrapping angle, to the dryer specific evaporation rate. Further, by means of an example, the specific evaporation rates obtainable for machine geometries currently used by various machine manufacturers are compared.     

CFD modeling of the Wurster bed coater

In the Wurster bed coater, the wetting, drying, and circulation of particles are combined to produce a high quality coating. The drying and wetting conditions in a laboratory scale Wurster bed coater are modeled and compared with experimental data. A model combining multiphase fluid dynamics with heat and mass transfer is developed to model the particle and gas motion and the transport of thermal energy and moisture. A wetting region is defined, where a specified moisture content is set in the particle phase, above the jet inlet, to describe the injection of coating liquid. The simulation shows the characteristic circulation of particles in the equipment, as well as the behavior of the moisture in the system and agrees well with measurements. The simulation indicates how different process conditions influence the drying regions. The results show that most of the drying, under typical operating conditions, takes place in the Wurster tube. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

Projected beam irradiation at low latitudes using Meteonorm database

The quantitative analysis of beam radiation received on a solar concentrator may be understood by evaluating the projected solar height angle or profile angle along the north–south vertical plane. This means that all the sunrays projected along the north–south vertical plane will be intercepted by a collector provided the projection angle lies within the acceptance angle. The Meteonorm method of calculating solar radiation on any arbitrary oriented surface uses the globally simulated meteorological databases. Meteonorm has become a valuable tool for estimating solar radiation where measured solar radiation data is missing or irregular. In this paper we present the projected beam solar radiation at low latitudes based on the standard Meteonorm calculations. The conclusion is that there is potential in using solar concentrators at these latitudes since the projected beam radiation is more during winter periods than in summer months. This conclusion is in conformity with the design principle of solar collectors for worst case conditions.