Domain Configurations, Bloch Walls, and Magnetization Processes in Iron Whiskers from D.C. to 200 kHz. Theory and Experiment. I

1972 ◽  
Vol 50 (7) ◽  
pp. 710-720 ◽  
Author(s):  
B. Heinrich ◽  
A. S. Arrott
Keyword(s):  
Eddy Currents ◽  
Elastic Membrane ◽  
Magnetization Measurements ◽  
Wide Range ◽  
Elastic Wall ◽  
Iron Whiskers ◽  
Magnetization Processes ◽  
Theory And Experiment

Bloch walls in iron whiskers have been studied by direct magnetization measurements. Of several types of domain configurations the simplest, the Landau structure, is readily identified from the a.c. permeability. The behavior of this structure over a wide range of frequencies is accounted for by a model which treats the wall as an elastic membrane attached to two springs on its ends. The stiffness is shown to be magnetostatic in origin. The elastic wall is shown to be damped in its motion by eddy currents. The qualitative aspects of the behavior are well accounted for and some numerical consistencies are found.

Magnetization Processes and Eddy Currents in Iron Whiskers

1972 ◽  
Author(s):  
A. S. Arrott ◽  
B. Heinrich ◽  
D. S. Bloomberg
Keyword(s):  
Eddy Currents ◽  
Iron Whiskers ◽  
Magnetization Processes

Domain Configurations, Bloch Walls and Magnetization Processes in Iron Whiskers from D.C. to 200 kHz. Theory and Experiment II

1973 ◽  
Author(s):  
A. S. Arrott ◽  
B. Heinrich ◽  
D. S. Bloomberg ◽  
Hugh C. Wolfe ◽  
C. D. Graham ◽  
...  
Keyword(s):  
Iron Whiskers ◽  
Magnetization Processes ◽  
Theory And Experiment

Computation of linear elastic properties from microtomographic images: Methodology and agreement between theory and experiment

Geophysics ◽  
2002 ◽  
Vol 67 (5) ◽  
pp. 1396-1405 ◽  
Author(s):  
Christoph H. Arns ◽  
Mark A. Knackstedt ◽  
W. Val Pinczewski ◽  
Edward J. Garboczi
Keyword(s):  
Elastic Properties ◽  
Excellent Agreement ◽  
Fontainebleau Sandstone ◽  
Linear Elastic ◽  
Numerical Predictions ◽  
Wide Range ◽  
Digitized Images ◽  
Water Saturated ◽  
Dry Water ◽  
Theory And Experiment

Elastic property‐porosity relationships are derived directly from microtomographic images. This is illustrated for a suite of four samples of Fontainebleau sandstone with porosities ranging from 7.5% to 22%. A finite‐element method is used to derive the elastic properties of digitized images. By estimating and minimizing several sources of numerical error, very accurate predictions of properties are derived in excellent agreement with experimental measurements over a wide range of the porosity. We consider the elastic properties of the digitized images under dry, water‐saturated, and oil‐saturated conditions. The observed change in the elastic properties due to fluid substitution is in excellent agreement with the exact Gassmann's equations. This shows both the accuracy and the feasibility of combining microtomographic images with elastic calculations to accurately predict petrophysical properties of individual rock morphologies. We compare the numerical predictions to various empirical, effective medium and rigorous approximations used to relate the elastic properties of rocks to porosity under different saturation conditions.

scholarly journals 3D harmonic modeling of eddy currents in segmented conducting structures

2019 ◽  
Vol 38 (1) ◽  
pp. 2-23 ◽  
Author(s):  
C.H.H.M. Custers ◽  
J.W. Jansen ◽  
M.C. van Beurden ◽  
E.A. Lomonova
Keyword(s):  
Finite Element ◽  
Eddy Current ◽  
Eddy Currents ◽  
Three Dimensional ◽  
Spatial Period ◽  
Content Type ◽  
Current Distributions ◽  
Wide Range ◽  
Conductivity Function ◽  
Electromagnetic Quantities

PurposeThe purpose of this paper is to describe a semi-analytical modeling technique to predict eddy currents in three-dimensional (3D) conducting structures with finite dimensions. Using the developed method, power losses and parasitic forces that result from eddy current distributions can be computed.Design/methodology/approachIn conducting regions, the Fourier-based solutions are developed to include a spatially dependent conductivity in the expressions of electromagnetic quantities. To validate the method, it is applied to an electromagnetic configuration and the results are compared to finite element results.FindingsThe method shows good agreement with the finite element method for a large range of frequencies. The convergence of the presented model is analyzed.Research limitations/implicationsBecause of the Fourier series basis of the solution, the results depend on the considered number of harmonics. When conducting structures are small with respect to the spatial period, the number of harmonics has to be relatively large.Practical implicationsBecause of the general form of the solutions, the technique can be applied to a wide range of electromagnetic configurations to predict, e.g. eddy current losses in magnets or wireless energy transfer systems. By adaptation of the conductivity function in conducting regions, eddy current distributions in structures containing holes or slit patterns can be obtained.Originality/valueWith the presented technique, eddy currents in conducting structures of finite dimensions can be modeled. The semi-analytical model is for a relatively low number of harmonics computationally faster than 3D finite element methods. The method has been validated and shown to be computationally accurate.

scholarly journals The influence of viscosity on the frozen wave instability: theory and experiment

2007 ◽  
Vol 584 ◽  
pp. 45-68 ◽  
Author(s):  
EMMA TALIB ◽  
SHREYAS V. JALIKOP ◽  
ANNE JUEL
Keyword(s):  
Linear Stability ◽  
Lower Layer ◽  
Experimental Parameter ◽  
Quantitative Agreement ◽  
Stability Study ◽  
Base Flow ◽  
Viscosity Contrast ◽  
Wide Range ◽  
Horizontal Oscillation ◽  
Theory And Experiment

We present the results of an experimental and linear stability study of the influence of viscosity on the frozen wave (FW) instability, which arises when a vessel containing stably stratified layers of immiscible liquids is oscillated horizontally. Our linear stability model consists of two superposed fluid layers of arbitrary viscosities and infinite lateral extent, subject to horizontal oscillation. The effect of the endwalls of the experimental vessel is simulated by enforcing the conservation of horizontal volume flux, so that the base flow consists of counterflowing layers.We perform experiments with four pairs of fluids, keeping the viscosity of the lower layer (ν1) constant, and increasing the viscosity of the upper layer (ν2), so that 1.02 × 102 ≤ N1 = ν2/ν1 ≤ 1.21 × 104. We find excellent quantitative agreement between theory and experiment despite the simple model geometry, for both the critical onset parameter and wavenumber of the FW. We show that the model of lyubimov:1987 (Fluid Dyn. vol. 86, 1987, p. 849), which is valid in the limit of inviscid fluids, consistently underestimates the instability threshold for fluids of equal viscosity, but generally overestimates the threshold for fluids of unequal viscosity. We extend the experimental parameter range numerically to viscosity contrasts 1 ≤ N1 ≤ 6 × 104 and identify four regions of N1 where qualitatively different dynamics occur, which are reflected in the non-monotonic dependence of the most unstable wavenumber and the critical amplitude on N1. In particular, we find that increasing the viscosity contrast between the layers leads to destabilization over a wide range of N1, 10 ≤ N1 ≤ 8 × 103. The intricate dependence of the instability on viscosity contrast is due to considerable changes in the time-averaged perturbation vorticity distribution near the interface.

General methods for evaluating matrix elements of singular operators in two-electron systems

1994 ◽  
Vol 72 (11-12) ◽  
pp. 822-844 ◽  
Author(s):  
Zong-Chao Yan ◽  
G. W. F. Drake
Keyword(s):  
General Scheme ◽  
Triplet States ◽  
Electron Systems ◽  
Matrix Elements ◽  
Atomic Systems ◽  
Singular Operators ◽  
Wide Range ◽  
Qed Effects ◽  
Hylleraas Coordinates ◽  
Theory And Experiment

Due to the recent advances in both theory and experiment for the fine structure of two-electron atomic systems, it is necessary to include quantum electrodynamic (QED) effects through orders α6mc2, α7ln(Zα)mc2, and α7mc2, in order to match the experimental precision. These effects can be expressed in terms of a sum of singular operators. A general scheme is given for the evaluation of a wide range of matrix elements of high-order singular QED operators for two-electron atomic systems in Hylleraas coordinates. The scheme presented here can be applied to triplet states with arbitrary angular momentum. A number of useful expressions for the analytical evaluation of radial integrals are derived. An example is given in calculating the Douglas and Kroll terms, and the numerical values of the reduced matrix elements are presented for the 2 3PJ states of helium.

Magnetic Aging

2005 ◽  
Vol 887 ◽  
Author(s):  
R. Skomski ◽  
J. Zhou ◽  
R. D. Kirby ◽  
D. J. Sellmyer
Keyword(s):  
Free Energy ◽  
Power Law ◽  
Magnetization Reversal ◽  
Eddy Currents ◽  
Scientific Research ◽  
Magnetization Dynamics ◽  
Energy Barriers ◽  
Thermally Activated ◽  
Magnetic Aging ◽  
Magnetization Processes

ABSTRACTThermally activated magnetization reversal is of great importance in areas such as permanent magnetism and magnetic recording. In spite of many decades of scientific research, the phenomenon of slow magnetization dynamics has remained partially controversial. It is now well-established that the main mechanism is thermally activated magnetization reversal, as contrasted to eddy currents and structural aging, but the identification of the involved energy barriers remains a challenge for many systems. Thermally activated slow magnetization processes proceed over energy barriers whose structure is determined by the micromagnetic free energy. This restricts the range of physically meaningful energy barriers. An analysis of the underlying micromagnetic free energy yields power-law dependences with exponents of 3/2 or 2 for physically reasonable models, in contrast to arbitrary exponents m and to 1/H-type laws.

Magnetization processes of iron whiskers in small magnetic fields

1979 ◽  
Vol 20 (2) ◽  
pp. 159-161 ◽  
Author(s):  
H. H. Mende ◽  
Th. Kleinefeld
Keyword(s):  
Magnetic Fields ◽  
Iron Whiskers ◽  
Magnetization Processes

Magnetization Processes Analysis in Co-Cu Superlattices

1989 ◽  
Vol 151 ◽  
Author(s):  
J. P. Rebouillat ◽  
G. Fillion ◽  
B. Dieny ◽  
A. Cebollada ◽  
J. M. Gallego ◽  
...  
Keyword(s):  
Hysteresis Loops ◽  
Antiferromagnetic Coupling ◽  
Magnetization Measurements ◽  
The Individual ◽  
Magnetization Processes

ABSTRACTThe analysis of the magnetization measurements performed on two Co-Cu multilayers confirm the antiferromagnetic coupling already observed with neutron experiments. Both exchange and anisotropy energies are taken into account and estimated. Their competitive role in the individual moment orientation leads to typical moment arrangements and hysteresis loops.

scholarly journals An elastocapillary model of wood-fibre collapse

2015 ◽  
Vol 471 (2179) ◽  
pp. 20150184 ◽  
Author(s):  
Amir Akbari ◽  
Reghan J. Hill ◽  
Theo G. M. van de Ven
Keyword(s):  
Contact Angle ◽  
Aspect Ratio ◽  
Elastic Membrane ◽  
Saturation Point ◽  
Capillary Surfaces ◽  
Hole Radius ◽  
Wide Range ◽  
Structural Failures ◽  
Membrane Stretching ◽  
Rigid Walls

An elastocapillary model for drying-induced collapse is proposed. We consider a circular elastic membrane with a hole at the centre that is deformed by the capillary pressure of simply and doubly connected menisci. The membrane overlays a cylindrical cavity with rigid walls, trapping a prescribed volume of water. This geometry may be suitable for studying structural failures and stiction in micro-electromechanical systems during wet etching, where capillary surfaces experience catastrophic transitions. The dry state is determined using the dihedral-angle and volume-turning-point stability criteria. Open and collapsed conformations are predicted from the scaled hole radius, cavity aspect ratio, meniscus contact angle with the membrane and cavity walls, and an elastocapillary number measuring the membrane stretching rigidity relative to the water surface tension. For a given scaled hole radius and cavity aspect ratio, there is a critical elastocapillary number above which the system does not collapse upon drying. The critical elastocapillary number is weakly influenced by the contact angle over a wide range of the scaled hole radius, thus indicating a limitation of surface hydrophobization for controlling the dry-state conformation. The model is applied to the drying of wood fibres above the fibre saturation point, determining the conditions leading to collapse.

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