An efficient randomised sphere cover classifier

This paper describes an efficient randomised sphere cover classifier(aRSC), that reduces the training data set size without loss of accuracy when compared to nearest neighbour classifiers. The motivation for developing this algorithm is the desire to have a non-deterministic, fast, instance-based classifier that performs well in isolation but is also ideal for use with ensembles. We use 24 benchmark datasets from UCI repository and six gene expression datasets for evaluation. The first set of experiments demonstrate the basic benefits of sphere covering. The second set of experiments demonstrate that when we set the a parameter through cross validation, the resulting aRSC algorithm outperforms several well known classifiers when compared using the Friedman rank sum test. Thirdly, we test the usefulness of aRSC when used with three feature filtering filters on six gene expression datasets. Finally, we highlight the benefits of pruning with a bias/variance decompositio

Structure and magnetic properties of nanocrystalline PrCo3

The structure and magnetic properties of nanocrystalline PrCo$_3$ prepared by high-energy milling technique have been investigated by means of X-ray diffraction using the Rietveld method coupled to Curie temperature and magnetic measurements. The as-milled samples were subsequently annealed in temperature range from 750 to 1050 {\deg}C for 30 min to optimize the extrinsic properties. From x-ray studies of magnetic aligned samples, the magnetic anisotropy of this compounds is found uniaxial. The Curie temperature is 349 {\deg}K and no saturation reached at room temperature for applied field of 90 kOe. The coercive field of 55 kOe and 12 kOe measured at 10 and 293 K respectively is obtained after annealing at 750 {\deg}C for 30 min suggests that nanocrystalline PrCo$_3$ are interesting candidates in the field of permanent magnets. We have completed this experimental study by simulations in the micromagnetic framework in order to get a qualitative picture of the microstructure effect on the macroscopic magnetization curve. From this simple model calculation, we can suggest that the after annealing the system behaves as magnetically hard crystallites embedded in a weakly magnetized amorphous matrix. PACS : 75.50.Bb, 75.50.Tt, 76.80.+yComment: Published in Journal of Applied Physics, 107, 083916 (2010). To be found at: http://jap.aip.or

Magnetic and structural properties of nanocrystalline PrCo3_3

The structure and magnetic properties of nanocrystalline PrCo$_3$ obtained from high energy milling technique are investigated by X-ray diffraction, Curie temperature determination and magnetic properties measurements are reported. The as-milled samples have been annealed in a temperature range of 1023 K to 1273 K for 30 mn to optimize the extrinsic properties. The Curie temperature is 349\,K and coercive fields of 55\,kOe at 10\,K and 12\,kOe at 293\,K are obtained on the samples annealed at 1023\,K. A simulation of the magnetic properties in the framework of micromagnetism has been performed in order to investigate the influence of the nanoscale structure. A composite model with hard crystallites embedded in an amorphous matrix, corresponding to the as-milled material, leads to satisfying agreement with the experimental magnetization curve. [ K. Younsi, V. Russier and L. Bessais, J. Appl. Phys. {\bf 107}, 083916 (2010)]. The microscopic scale will also be considered from DFT based calculations of the electronic structure of $R$Co$_x$ compounds, where $R$ = (Y, Pr) and $x$ = 2,3 and 5.Comment: To be published in J. Phys.: Conference Series in the JEMS 2010 special issue. To be found once published at http://iopscience.iop.org/1742-659

Aberrational Effects for Shadows of Black Holes

In this paper, we discuss how the shadow of a Kerr black hole depends on the motion of the observer. In particular, we derive an analytical formula for the boundary curve of the shadow for an observer moving with given four-velocity at given Boyer--Lindquist coordinates. We visualize the shadow for various values of parameters.Comment: 12 pages, 3 figures; Proceedings of the 524. WE-Heraeus-Seminar held at the Physikzentrum, Bad Honnef, Germany, 17.--23.2.201

Influence of design parameters on the unsteady flow in a centrifugal fan

ABSTRACT The aim of this study is to evaluate the influence of design parameters on the unsteady flow in a forward-curved centrifugal fan and their impact on the aeroacoustic behavior. To do so, numerical and experimental study has been carried out on four centrifugal impellers designed with various geometrical parameters. The same volute casing has been used to study these fans. The effects on the unsteady flow behavior related to irregular blade spacing, blade number and radial distance between the impeller periphery and the volute tongue have been studied. The numerical simulations of the unsteady flow have been carried out using Computational Fluid Dynamics tools (CFD) based on Unsteady Reynolds Averaged Navier Stokes approach (URANS). The sliding mesh technique has been applied at the interfaces between the rotating and stationary zones in order to model the blades' motion relative to the volute casing. The study is focused on the unsteadiness induced by the aerodynamic interaction between the volute and the rotating impeller blades. In order to predict the acoustic pressure at far field, the unsteady flow variables provided by the CFD calculations (pressure and velocity fluctuations acquired upon the surfaces of the rotating blades) have been used as inputs in the Ffowcs Williams-Hawkings equations (FW-H). Using this model, the acoustic pressure has been computed at the fan exit duct. The experimental part of this work concerns measurement of aerodynamic performance of the fans using a test bench built according to ISO 5801 [1] standard. In addition to this, pressure microphones have been flush-mounted on the volute tongue surface in order to measure the wall pressure fluctuations. The sound pressure level (SPL) measurements have been carried out in an anechoic room in order to remove undesired noise reflections. Finally, the numerical results have been compared with the experimental measurements and a correlation between the wall pressure fluctuations and the far field noise signals has been found

Moisture sorption isotherms and heat of sorption of Algerian bay leaves (Laurus nobilis)

The moisture sorption isotherms of Algerian bay leaves (Laurus nobilis) were determined experimentally in this work. The equilibrium moisture contents of the leaves were measured at 40, 50, and 60 °C using static gravimetric method. Six mathematical models were tested to fit the experimental data of sorption isotherms and predict the hygroscopic behavior during storage or drying. Peleg model was found to be the best fitting model for describing the sorption curves. The net isosteric heat of sorption was computed from the equilibrium data at different temperatures by applying the integrated form of the Clausius-Clapeyron equation. The net isosteric heat of sorption is inversely proportional to the equilibrium moisture content and is found to be an exponential function of moisture content

Moisture sorption isotherms and heat of sorption of Algerian bay leaves (Laurus nobilis)

ABSTRACT: The moisture sorption isotherms of Algerian bay leaves (Laurus nobilis) were determined experimentally in this work. The equilibrium moisture contents of the leaves were measured at 40, 50, and 60 °C using static gravimetric method. Six mathematical models were tested to fit the experimental data of sorption isotherms and predict the hygroscopic behavior during storage or drying. Peleg model was found to be the best fitting model for describing the sorption curves. The net isosteric heat of sorption was computed from the equilibrium data at different temperatures by applying the integrated form of the Clausius-Clapeyron equation. The net isosteric heat of sorption is inversely proportional to the equilibrium moisture content and is found to be an exponential function of moisture content

Fine-Scale Phylogeographic Structure of Borrelia lusitaniae Revealed by Multilocus Sequence Typing

Borrelia lusitaniae is an Old World species of the Lyme borreliosis (LB) group of tick-borne spirochetes and prevails mainly in countries around the Mediterranean Basin. Lizards of the family Lacertidae have been identified as reservoir hosts of B. lusitaniae. These reptiles are highly structured geographically, indicating limited migration. In order to examine whether host geographic structure shapes the evolution and epidemiology of B. lusitaniae, we analyzed the phylogeographic population structure of this tick-borne bacterium using a recently developed multilocus sequence typing (MLST) scheme based on chromosomal housekeeping genes. A total of 2,099 questing nymphal and adult Ixodes ricinus ticks were collected in two climatically different regions of Portugal, being ∼130 km apart. All ticks were screened for spirochetes by direct PCR. Attempts to isolate strains yielded 16 cultures of B. lusitaniae in total. Uncontaminated cultures as well as infected ticks were included in this study. The results using MLST show that the regional B. lusitaniae populations constitute genetically distinct populations. In contrast, no clear phylogeographic signals were detected in sequences of the commonly used molecular markers ospA and ospC. The pronounced population structure of B. lusitaniae over a short geographic distance as captured by MLST of the housekeeping genes suggests that the migration rates of B. lusitaniae are rather low, most likely because the distribution of mediterranean lizard populations is highly parapatric. The study underlines the importance of vertebrate hosts in the geographic spread of tick-borne microparasites