Crystallization of (Fe,Mn)-based nanoparticles in sodium-silicate glasses

In this investigation, glasses from the system Na₂O/MnO/SiO₂/Fe₂O₃ are prepared using a conventional glass-melting technique. During annealing the glass, a nanocrystalline (Fe, Mn)-based spinel phase is precipitated. The phase composition and microstructure of the formed glass–ceramics are studied using X-ray diffraction and electron microscopy. Anomalous small-angle X-ray scattering experiment is used to gather information on the size, composition and element distribution for the precipitated (Fe, Mn)-based nanocrystals. The sizes of the formed spinel crystals, as determined by scanning electron microscopy and anomalous X-ray scattering, are in the range from 12 to 50 nm for annealing temperatures in the range from 550 to 700 °C. Annealing for a longer period of time at temperatures ≥600 °C results in the formation of a second crystalline phase, NaFe(SiO₃)₂ (aegirine). The ASAXS data show the formation of core–shell structure for the (Fe, Mn)-based crystals with core consisting mostly of iron oxide and a shell, depleted of Fe and Mn. The growth of the spinel crystals is assumed to be kinetically self-constrained.     

ZnO nanobelt/nanowire Schottky diodes formed by dielectrophoresis alignment across au electrodes

Rectifying diodes of single nanobelt/nanowire-based devices have been fabricated by aligning single ZnO nanobelts/nanowires across paired Au electrodes using dielectrophoresis. A current of 0.5 microA at 1.5 V forward bias has been received, and the diode can bear an applied voltage of up to 10 V. The ideality factor of the diode is approximately 3, and the on-to-off current ratio is as high as 2,000. The detailed IV characteristics of the Schottky diodes have been investigated at low temperatures. The formation of the Schottky diodes is suggested due to the asymmetric contacts formed in the dielectrophoresis aligning process.     

Noninterferometric characterization of partially coherent scalar wave fields and application to scattered light

We report on the application of a simple propagation-based phase-space tomographic technique to the determination of characteristic projections through the mutual optical intensity and the generalized radiance of a scalar, quasi-monochromatic partially coherent wave field. This method is applied to the reconstruction of the coherence functions of an initially spatially coherent optical wave field that has propagated through a suspension of polystyrene microspheres. As anticipated, we see that the field separates into a ballistic, or unscattered, component and a scattered component with a much shorter coherence length. Good agreement is obtained between experimental results and the results of a model based on a wave-transport equation.     

Comment on “Balance recovery control for biped robot based on reaction null space method”

We hereby acknowledge that the published paper on our journal, “Balance recovery control for biped robot based on reaction null space method” by Baoping Wang, Renxi Hu, Jinming Zhang and Chuangfeng Huai, is a plagiarism of “Balance control of a humanoid robot based on the reaction null space method” by Akinori Nishio, Kentaro Takahashi and Dragomir N. Nenchev. We withdrew the plagiarized paper from the Springer website, and sent a formal notification letter to each author’s affiliation. Any submission from Baoping Wang, Renxi Hu, Jinming Zhang or Chuangfeng Huai will not be accepted in three years from now on. The above comment and this notification are published not only in this printed version, but also on the Springer website and our journal website. We have used plagiarism scanning software and started the online detection of plagiarism in the received papers in September 2010 for screening the plagiarized submission.     

Multidepot pickup and delivery problems in multiple regions: a typology and integrated model

The rapid development experienced by the transportation industry in the past decades has led to many configurations of networks and therefore to an explosion of variants in transportation problems, motivating researchers to look at broader logistic problems, beyond the basic vehicle routing problems. This work introduces a new type of problem scenario combining various attributes: a pickup and delivery problem with multiple regions, multiple depots, and multiple transportation modes. We provide definitions, a literature review, and a step‐by‐step construction of the mathematical models from a simple and well‐known scenario to the multiregion multidepot pickup and delivery problem (MR‐MDPDP). For each step the relevant literature is examined. Furthermore, we suggest possible extensions for prospective research.     

Edge States and Topological Phase Transitions in Chains of Dielectric Nanoparticles

Recently introduced field of topological photonics aims to explore the concepts of topological insulators for novel phenomena in optics. Here polymeric chains of subwavelength silicon nanodisks are studied and it is demonstrated that these chains can support two types of topological edge modes based on magnetic and electric Mie resonances, and their topological properties are fully dictated by the spatial arrangement of the nanoparticles in the chain. It is observed experimentally and described how theoretically topological phase transitions at the nanoscale define a change from trivial to nontrivial topological states when the edge mode is excited.     

Columbia digital news project: an environment for briefing and search over multimedia information

In this paper we describe an ongoing research project called the Columbia Digital News Project. The goal of this project is to develop a suite of effective interoperable tools with which people can find relevant information (text, images, video, and structured documents) from distributed sources and track it over a period of time. Our initial focus is on the development of a system with which researchers, journalists, and students can keep track of current news events in specific areas.     

Mathematical modelling of fluidized bed reactors—III: Axial dispersion model

An axial dispersion model has been developed for a continuous fluidized bed catalytic reactor with a cocurrent flow of the emulsion phase gas and the catalyst particles. The influence of some parameters on multiplicity of steady states has been reported. Several examples illustrating the transient behavior of the system are presented. In cases where three steady states are possible it appears that the intermediate steady state is unstable, while the lower and the upper steady states are locally stable. It was noted that the initial temperature of the emulsion phase is a predominant factor in determining which steady state will be approached.     

Analysis of a model for a nonisothermal continuous fluidized bed catalytic reactor

A three-phase model, consisting of a dilute or bubble phase, an interstitial gas phase and a solids phase, has been developed for a non-isothermal gas fluidized-bed catalytic reactor with continuous circulation of catalyst particles. The dilute phase is assumed to be in plug flow, the interstitial gas is considered to be either perfectly mixed or in plug flow, and the particles are assumed to be perfectly mixed.It is shown that the conversion in a reactor and steady state temperature and concentration profiles are the same irrespectively of the assumed flow pattern in the interstitial gas.The numerical computations were done for the case of a single irreversible reaction with or without catalyst decay and for the case of two consecutive irreversible reactions. In the case of an adiabatic reactor and ordinary exothermic reactions, or in the case of a cooled reactor with a highly exothermic reaction, multiple steady states may occur.     

Effects of process and design parameters on heat management in fixed bed Fischer-Tropsch synthesis reactor

A two-dimensional pseudo-homogeneous model of wall-cooled fixed bed Fischer-Tropsch synthesis (FTS) reactor with Co/Re/γ-Al₂O₃ catalyst was developed to study the effect of process and design parameters on heat generation and removal characteristics. The influence of liquid-phase formation on heat transport was accounted for by using two-phase correlations. The effect of intraparticle diffusion on heat generation was considered. Detailed numerical simulations were performed to analyze the effect of process and design parameters on the reactor performance in terms of heat management. Results show that thermal behavior of FTS fixed bed reactors is very sensitive and any large disturbances can lead to temperature runaway. Large tube diameters are shown to be particularly unfavorable, with d _t >5 cm resulting in axial and radial gradients greater than 20 K and 13 K, respectively. The importance of detailed reactor modeling when designing and optimizing FTS fixed bed reactors is highlighted.