7,684 research outputs found
Prediction of the electromagnetic torque in synchronous machines through Maxwell stress harmonic filter (HFT) method
For the calculation of torque in synchronous motors a local method is analysed, based on the Maxwell stress theory and the filtered contributions due to the harmonics of the magnetic vector potential in the motor air-gap. By considering the space fundamental field only, the method can efficiently estimate the average synchronous torque for a variety or motor topologies, including concentrated winding designs. This approach employs an analytical filter for the Maxwell stress tensor and `frozen permeability' technique. The proposed method is validated by comparison with FE results for several synchronous motor types: interior permanent magnet motors, wound field motor, synchronous reluctance motor
A best-fit model of power losses in cold rolled-motor lamination steel operating in a wide range of frequency and magnetization
A procedure is described for identifying a mathematical model of core losses in ferromagnetic steel based on a minimal amount of experimental data. The new model has a hysteresis loss multiplicative coefficient variable only with frequency, a hysteresis loss power coefficient variable both with frequency and induction and a combined coefficient for eddy-current and excess losses that is, within a set frequency range, variable only with induction. Validation was successfully performed on a large number of different samples of nongrain oriented fully and semiprocessed steel alloys. Over a wide range of frequencies between 20 Hz and 2.1 kHz and inductions from 0.05 up to 2 T, the errors of the proposed model are substantially lower than those of a conventional model with fixed value coefficients
The moduli space of (111)-polarized abelian surfaces is unirational
We prove that the moduli space 11lev of (1,11)-polarized Abelian surfaces with level structure of canonical type is birational to Klein's cubic hypersurface in P4. Therefore, 11lev is unirational but not rational, and there are no Γ11-cusp forms of weight 3. The same methods also provide an easy proof of the rationality of 9lev
Calabi–Yau threefolds and moduli of abelian surfaces I
We describe birational models and decide the rationality/unirationality of moduli spaces d (and levd) of (1, d)-polarized Abelian surfaces (with canonical level structure, respectively) for small values of d. The projective lines identified in the rational/unirational moduli spaces correspond to pencils of Abelian surfaces traced on nodal threefolds living naturally in the corresponding ambient projective spaces, and whose small resolutions are new Calabi–Yau threefolds with Euler characteristic zero
MOCVD-Fabricated TiO2 Thin Films: Influence of Growth Conditions on Fibroblast Cells Culture
TiO2 thin films with various morphologies were grown on Ti substrates by the LP-MOCVD technique (Low Pressure Chemical Vapour Deposition from Metal-Organic precursor), with titanium tetra-iso-propoxide as a precursor. All the films were prepared in the same conditions except the deposition time. They were characterized by X-ray diffraction, scanning electron microscopy, optical 15 interferometry, water contact angle measurements. MOCVD-fabricated TiO2 thin films are known to be adapted to cell culture for implant requirements. Human gingival fibroblasts were cultured on the various TiO2 deposits. Differences in cell viability (MTT tests) and cell spreading (qualitative assessment) were observed and related to film roughness, wettability and allotropic composition
Age and Mass for 920 LMC Clusters Derived from 100 Million Monte Carlo Simulations
We present new age and mass estimates for 920 stellar clusters in the Large
Magellanic Cloud (LMC) based on previously published broad-band photometry and
the stellar cluster analysis package, MASSCLEANage. Expressed in the generic
fitting formula, d^{2}N/dM dt ~ M^{\alpha} t^{\beta}, the distribution of
observed clusters is described by \alpha = -1.5 to -1.6 and \beta = -2.1 to
-2.2. For 288 of these clusters, ages have recently been determined based on
stellar photometric color-magnitude diagrams, allowing us to gauge the
confidence of our ages. The results look very promising, opening up the
possibility that this sample of 920 clusters, with reliable and consistent age,
mass and photometric measures, might be used to constrain important
characteristics about the stellar cluster population in the LMC. We also
investigate a traditional age determination method that uses a \chi^2
minimization routine to fit observed cluster colors to standard infinite mass
limit simple stellar population models. This reveals serious defects in the
derived cluster age distribution using this method. The traditional \chi^2
minimization method, due to the variation of U,B,V,R colors, will always
produce an overdensity of younger and older clusters, with an underdensity of
clusters in the log(age/yr)=[7.0,7.5] range. Finally, we present a unique
simulation aimed at illustrating and constraining the fading limit in observed
cluster distributions that includes the complex effects of stochastic
variations in the observed properties of stellar clusters.Comment: Accepted for publication in The Astrophysical Journal, 37 pages, 18
figure
MASSCLEANage -- Stellar Cluster Ages from Integrated Colors --
We present the recently updated and expanded MASSCLEANcolors, a database of
70 million Monte Carlo models selected to match the properties (metallicity,
ages and masses) of stellar clusters found in the Large Magellanic Cloud (LMC).
This database shows the rather extreme and non-Guassian distribution of
integrated colors and magnitudes expected with different cluster age and mass
and the enormous age degeneracy of integrated colors when mass is unknown. This
degeneracy could lead to catastrophic failures in estimating age with standard
SSP models, particularly if most of the clusters are of intermediate or low
mass, like in the LMC. Utilizing the MASSCLEANcolors database, we have
developed MASSCLEANage, a statistical inference package which assigns the most
likely age and mass (solved simultaneously) to a cluster based only on its
integrated broad-band photometric properties. Finally, we use MASSCLEANage to
derive the age and mass of LMC clusters based on integrated photometry alone.
First we compare our cluster ages against those obtained for the same seven
clusters using more accurate integrated spectroscopy. We find improved
agreement with the integrated spectroscopy ages over the original photometric
ages. A close examination of our results demonstrate the necessity of solving
simultaneously for mass and age to reduce degeneracies in the cluster ages
derived via integrated colors. We then selected an additional subset of 30
photometric clusters with previously well constrained ages and independently
derive their age using the MASSCLEANage with the same photometry with very good
agreement. The MASSCLEANage program is freely available under GNU General
Public License.Comment: 17 pages, 11 figures. Accepted for publication in The Astrophysical
Journal. Full resolution figures available in journal versio
Diffusive spreading and mixing of fluid monolayers
The use of ultra-thin, i.e., monolayer films plays an important role for the
emerging field of nano-fluidics. Since the dynamics of such films is governed
by the interplay between substrate-fluid and fluid-fluid interactions, the
transport of matter in nanoscale devices may be eventually efficiently
controlled by substrate engineering. For such films, the dynamics is expected
to be captured by two-dimensional lattice-gas models with interacting
particles. Using a lattice gas model and the non-linear diffusion equation
derived from the microscopic dynamics in the continuum limit, we study two
problems of relevance in the context of nano-fluidics. The first one is the
case in which along the spreading direction of a monolayer a mesoscopic-sized
obstacle is present, with a particular focus on the relaxation of the fluid
density profile upon encountering and passing the obstacle. The second one is
the mixing of two monolayers of different particle species which spread side by
side following the merger of two chemical lanes, here defined as domains of
high affinity for fluid adsorption surrounded by domains of low affinity for
fluid adsorption.Comment: 12 pages, 3 figure
- …