Determination of Forces in a Magnetic Bearing Actuator: Numerical Computation With Comparison to Experiment

1992 ◽  
Vol 114 (4) ◽  
pp. 796-801 ◽  
Author(s):  
J. D. Knight ◽  
Z. Xia ◽  
E. McCaul ◽  
H. Hacker
Keyword(s):  
Relative Permeability ◽  
Free Space ◽  
Flux Distribution ◽  
Magnetic Bearing ◽  
Two Dimensional ◽  
Metal Parts ◽  
A Value ◽  
Axis Of Symmetry ◽  
Good Agreement

Calculations of the forces exerted on a journal by a magnetic bearing actuator are presented, along with comparisons to experimentally measured forces. The calculations are based on two-dimensional solutions for the flux distribution in the metal parts and free space, using finite but constant permeability in the metals. Above a relative permeability of 104 the effects of changes in permeability are negligible, but below 104 decreases in permeability cause significant decreases in the force. The calculated forces are shown to depend on the metal permeability more strongly when the journal is displaced from its centered position. The predicted forces in the principal attractive direction are in good agreement with experiment when a relatively low value of permeability is chosen. The forces measured normal to the axis of symmetry when the journal is displaced from that axis, however, are significantly higher than predicted by theory, even with a value of relative permeability larger than 5000. These results indicate a need for futher work including nonlinear permeability distributions.

Calculation and Verification of Magnetic Field Parameters in Axial Active Magnetic Bearing

2014 ◽  
Vol 214 ◽  
pp. 143-150
Author(s):  
Piotr Graca
Keyword(s):  
Magnetic Field ◽  
Finite Element Method ◽  
Magnetic Force ◽  
Magnetic Bearing ◽  
Active Magnetic Bearing ◽  
Magnetic Flux Density ◽  
Two Dimensional ◽  
The Finite Element Method ◽  
Magnetic Field Computation

The paper presents numerical modeling of an Axial Active Magnetic Bearing (AAMB) based on two-dimensional (2D) magnetic field computation. The calculations, assisted by the Finite Element Method (FEM), have focused on the determination of the magnetic flux density and the magnetic force. Obtained magnetic field parameters were then measured and verified on a physical model.

Device Modeling of a-Si:H Alloy Solar Cells: Calibration Procedure for Determination of Model Input Parameters

1998 ◽  
Vol 507 ◽  
Author(s):  
M. Zeman ◽  
R.A.C.M.M. Van Swaaij ◽  
E. Schroten ◽  
L.L.A. Vosteen ◽  
J.W. Metselaar
Keyword(s):  
Solar Cell ◽  
Material Properties ◽  
Calibration Procedure ◽  
Model Parameters ◽  
Model Input ◽  
A Value ◽  
Input Parameters ◽  
Simulated Material ◽  
Good Agreement

ABSTRACTA calibration procedure for determining the model input parameters of standard a-Si:H layers, which comprise a single junction a-Si:H solar cell, is presented. The calibration procedure consists of: i) deposition of the separate layers, ii) measurement of the material properties, iii) fitting the model parameters to match the measured properties, iv) simulation of test devices and comparison with experimental results. The inverse modeling procedure was used to extract values of the most influential model parameters by fitting the simulated material properties to the measured ones. In case of doped layers the extracted values of the characteristic energies of exponentially decaying tail states are much higher than the values reported in literature. Using the extracted values of model parameters a good agreement between the measured and calculated characteristics of a reference solar cell was reached. The presented procedure could not solve directly an important issue concerning a value of the mobility gap in a-Si:H alloys.

Measurement of the Isothermal Volume Dilation Accompanying the Unilateral Extension of Rubber

1959 ◽  
Vol 32 (2) ◽  
pp. 428-433
Author(s):  
Fred G. Hewitt ◽  
Robert L. Anthony
Keyword(s):  
Molecular Weight ◽  
Young’S Modulus ◽  
Experimental Results ◽  
Molecular Weights ◽  
Rubber Specimen ◽  
A Value ◽  
Fractional Increase ◽  
Internal Agreement ◽  
Good Agreement

Abstract The fractional increase in volume accompanying the isothermal extension of soft gum rubber was measured for four rubber samples at mean extensions of 14, 33, and 51%. The chain molecular weights Mc of the four samples were 5500, 5100, 4400, and 3000, with an estimated uncertainty of about 10% in each value of Mc. The observed fractional increase in volume ranged from 3.2×10−5 to 142×10−5, the latter value being observed for the sample of lowest chain molecular weight and at the extension of 51%. The experimental results for each sample have been represented by theoretical curves based on Gee's expression for the fractional increase in volume as a function of the sample extension. The theoretical curves exhibit good agreement with those of Gee, Stern, and Treloar. The process of fitting the theoretical curves to the experimental points constituted a determination of Young's modulus E for each rubber specimen. As a check on the experimental results, and also on the theory employed, determinations of E were also made by two additional methods, namely, from rough stess-strain curves, and from the relation E=3γρRT/Mc. With one exception, the internal agreement between the three determinations of E for the four different samples was satisfactory. The exception noted can probably be ascribed to the use of too small a value of Mc for the sample of lowest chain molecular weight.

Surface shear viscosity of Gibbs and Langmuir monolayers

1999 ◽  
Vol 397 ◽  
pp. 331-349 ◽  
Author(s):  
CATHERINE BARENTIN ◽  
CHRISTOPHE YBERT ◽  
JEAN-MARC DI MEGLIO ◽  
JEAN-FRANÇOIS JOANNY
Keyword(s):  
Shear Viscosity ◽  
Sodium Dodecyl ◽  
Langmuir Monolayers ◽  
Two Dimensional ◽  
Hydrodynamic Models ◽  
Surface Shear ◽  
Hydrodynamic Calculations ◽  
Good Agreement ◽  
Surface Shear Viscosity

In this paper, we present a new two-dimensional viscometer, and the hydrodynamic calculations used to obtain the surface viscosities from the measurements. In order to interpret the experiments, performed with solutions of sodium dodecyl sulfate (SDS) and also with monolayers of insoluble surfactants, we develop various hydrodynamic models of soluble Gibbs monolayers and of incompressible Langmuir monolayers, that describe well the experimental results. In the case of SDS solutions, the calculations allow the determination of the surface shear viscosity, and its value is in good agreement with previous studies.

Two-dimensional viscous gravity currents flowing over a deep porous medium

2001 ◽  
Vol 440 ◽  
pp. 359-380 ◽  
Author(s):  
JAMES M. ACTON ◽  
HERBERT E. HUPPERT ◽  
M. GRAE WORSTER
Keyword(s):  
Porous Medium ◽  
Numerical Solutions ◽  
Gravity Current ◽  
Constant Volume ◽  
Two Dimensional ◽  
Theoretical Predictions ◽  
Self Similar ◽  
Coefficient Of Viscosity ◽  
Good Agreement

The spreading of a two-dimensional, viscous gravity current propagating over and draining into a deep porous substrate is considered both theoretically and experimentally. We first determine analytically the rate of drainage of a one-dimensional layer of fluid into a porous bed and find that the theoretical predictions for the downward rate of migration of the fluid front are in excellent agreement with our laboratory experiments. The experiments suggest a rapid and simple technique for the determination of the permeability of a porous medium. We then combine the relationships for the drainage of liquid from the current through the underlying medium with a formalism for its forward motion driven by the pressure gradient arising from the slope of its free surface. For the situation in which the volume of fluid V fed to the current increases at a rate proportional to t3, where t is the time since its initiation, the shape of the current takes a self-similar form for all time and its length is proportional to t2. When the volume increases less rapidly, in particular for a constant volume, the front of the gravity current comes to rest in finite time as the effects of fluid drainage into the underlying porous medium become dominant. In this case, the runout length is independent of the coefficient of viscosity of the current, which sets the time scale of the motion. We present numerical solutions of the governing partial differential equations for the constant-volume case and find good agreement with our experimental data obtained from the flow of glycerine over a deep layer of spherical beads in air.

A Theoretical Approach to the Aerodynamically Significant Properties of Roughness from Insects

1960 ◽  
Vol 11 (2) ◽  
pp. 171-194 ◽  
Author(s):  
W. S. Coleman
Keyword(s):  
Incompressible Flow ◽  
Theoretical Approach ◽  
Leading Edge ◽  
Critical Conditions ◽  
Two Dimensional ◽  
Edge Zone ◽  
Good Agreement

SummaryIn Reference 3, attention is drawn to the difficulties of measuring the streamwise extent of the roughness from insects. The present paper deals with the problem theoretically for an aerofoil in two-dimensional, incompressible flow. A tentative approach to the determination of effective excrescence height downstream of the leading-edge zone is also advanced. The application of these investigations, in conjunction with the analysis from Ref. 3 regarding the critical conditions for premature transition, leads to estimates of the amount of significant roughness which are in good agreement with flight observation.

Automatic determination of diffuse-peak positions and the centre of a diffraction pattern

1999 ◽  
Vol 32 (2) ◽  
pp. 332-335 ◽  
Author(s):  
S. J. Wilkinson ◽  
D. W. L. Hukins
Keyword(s):  
Annulus Fibrosus ◽  
Gaussian Function ◽  
Two Dimensional ◽  
X Ray Diffraction ◽  
X Ray ◽  
Oriented Molecules ◽  
Beam Stop ◽  
Diffraction Patterns ◽  
Good Agreement

Correlation with a two-dimensional Gaussian function was used to locate the positions of diffuse peaks in X-ray diffraction patterns. The centre of a pattern was defined as the centroid of the image of the undeflected beam, found by convolution with a two-dimensional Gaussian function. These methods were implemented using the IDL programing language. They were tested on diffraction patterns from systems containing oriented molecules of the protein collagen: collagen tape, elastoidin spicules and annulus fibrosus of intervertebral disc. Specimens were dusted with quartz to calibrate the diffraction patterns. These patterns were recorded on film, using a semi-transparent beam stop to obtain an image of the undeflected beam, and digitized at a resolution of 105 µm. Intermolecular spacings, calculated from the distance between a peak and the centre of a pattern, were in good agreement with those determined previously.

Determination of Sulfur in Rubber Vulcanizates

1956 ◽  
Vol 29 (2) ◽  
pp. 612-619 ◽  
Author(s):  
E. W. Zimmerman ◽  
V. E. Hart ◽  
Emanuel Horowitz
Keyword(s):  
Nitric Acid ◽  
Barium Sulfate ◽  
Combustion Method ◽  
Fusion Method ◽  
Total Sulfur ◽  
A Value ◽  
Acid Method ◽  
Barium Compounds ◽  
Good Agreement

Abstract A combustion method for rubber which determines the sulfur evolved at 480° to 500° C is compared with the fusion and the zinc-nitric acid methods. In the combustion method an interaction occurs between sulfur and fillers present in the rubber. The effect of particular fillers with respect to this interaction is discussed. A value representative of the organically bound sulfur in an extracted specimen can be obtained by the combustion method when no reaction takes place between the sulfur and the fillers during combustion. The fusion method yields results in good agreement with the total sulfur added in compounding the rubber samples. Except in the presence of barium compounds, the zinc-nitric acid method likewise determines total sulfur. When barium compounds are present, barium sulfate is formed during the oxidation, and low values are obtained for the total sulfur.

DETERMINATION OF TRAPPING CENTER PARAMETERS OF Tl2Ga2S3Se LAYERED CRYSTALS BY THERMALLY STIMULATED CURRENT MEASUREMENTS

2010 ◽  
Vol 24 (14) ◽  
pp. 2149-2161 ◽  
Author(s):  
T. YILDIRIM ◽  
H. A. NASSER ◽  
N. M. GASANLY
Keyword(s):  
Cross Section ◽  
Trapping Center ◽  
Heating Rates ◽  
Thermally Stimulated Current ◽  
A Value ◽  
Initial Rise ◽  
Layered Crystals ◽  
Light Excitation ◽  
Good Agreement

We have carried out thermally stimulated current (TSC) measurements on as-grown Tl 2 Ga 2 S 3 Se layered single crystals in the temperature range 10–60 K with different heating rates of 0.6–1.5 K s1. The data were analyzed by curve fitting, initial rise, and peak shape methods. The results were in good agreement with each other. Experimental evidence was obtained for trapping center in Tl 2 Ga 2 S 3 Se crystal with activation energy of 11 meV. The capture cross section and concentration of the traps were found to be 1.5 × 10-23 cm 2 and 1.44 × 1010 cm -3, respectively. Analysis of the TSC data at different light excitation temperatures leads to a value of 18meV/decade for the traps distribution.

Vitamin A Value of Plant Food Provitamin A - Evaluated by the Stable Isotope Technologies

2014 ◽  
Vol 84 (Supplement 1) ◽  
pp. 25-29 ◽  
Author(s):  
Guangwen Tang
Keyword(s):  
Stable Isotope ◽  
Vitamin A ◽  
Provitamin A ◽  
Animal Origin ◽  
Plant Food ◽  
Plant Foods ◽  
A Value ◽  
Provitamin A Carotenoids ◽  
Β Carotene

Humans need vitamin A and obtain essential vitamin A by conversion of plant foods rich in provitamin A and/or absorption of preformed vitamin A from foods of animal origin. The determination of the vitamin A value of plant foods rich in provitamin A is important but has challenges. The aim of this paper is to review the progress over last 80 years following the discovery on the conversion of β-carotene to vitamin A and the various techniques including stable isotope technologies that have been developed to determine vitamin A values of plant provitamin A (mainly β-carotene). These include applications from using radioactive β-carotene and vitamin A, depletion-repletion with vitamin A and β-carotene, and measuring postprandial chylomicron fractions after feeding a β-carotene rich diet, to using stable isotopes as tracers to follow the absorption and conversion of plant food provitamin A carotenoids (mainly β-carotene) in humans. These approaches have greatly promoted our understanding of the absorption and conversion of β-carotene to vitamin A. Stable isotope labeled plant foods are useful for determining the overall bioavailability of provitamin A carotenoids from specific foods. Locally obtained plant foods can provide vitamin A and prevent deficiency of vitamin A, a remaining worldwide concern.

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