Magnetostatic Interactions and Coercivities of Ferromagnetic Soft Nanowires in Uniform Length Arrays

2008 ◽  
Vol 8 (6) ◽  
pp. 2944-2954 ◽  
Author(s):  
F. Béron ◽  
L. Clime ◽  
M. Ciureanu ◽  
D. Ménard ◽  
R. W. Cochrane ◽  
...  
Keyword(s):  
Nanowire Arrays ◽  
Physical Parameters ◽  
Preisach Model ◽  
General Shape ◽  
First Order ◽  
Average Value ◽  
Interaction Field ◽  
Soft Ferromagnetic ◽  
Out Of Plane ◽  
Magnetostatic Interactions

First-order reversal curve diagrams have been used to investigate magnetostatic interactions and average coercivity of individual wires in soft ferromagnetic uniform length nanowire arrays. We present a method for identifying these physical parameters on the out-of-plane first-order reversal curve diagrams: the position of the irreversible part on the critical axis is a good approximation to the average value of the nanowire coercivity and the maximum interaction field is equal to the interaction field at saturation. Their dependence upon material (CoFeB and Ni) and nanowire length are presented. The magnetostatic interactions increase linearly with length, in agreement with a model developed previously. The global array coercivity, obtained from magnetization curves, is generally lower than the apparent average coercivity for individual nanowires. This coercivity reduction increases linearly with the magnetostatic interactions. The general shape of the out-of-plane first-order reversal curve diagrams is compared with those obtained from a theoretical moving Preisach model.

Out-of-plane static compression and energy absorption of paper hierarchical corrugation sandwich panels

2021 ◽  
pp. 030932472110085
Author(s):  
Huineng Wang ◽  
Yanfeng Guo ◽  
Yungang Fu ◽  
Dan Li
Keyword(s):  
Yield Strength ◽  
Bearing Capacity ◽  
Energy Absorption ◽  
Sandwich Panel ◽  
Second Order ◽  
Compression Rate ◽  
Static Compression ◽  
First Order ◽  
Out Of Plane ◽  
Analytical Approaches

This study introduces the opinion of the corrugation hierarchy to develop the second-order corrugation paperboard, and explore the deformation characteristics, yield strength, and energy absorbing capacity under out-of-plane static evenly compression loading by experimental and analytical approaches. On the basis of the inclined-straight strut elements of corrugation unit and plastic hinge lines, the yield and crushing strengths of corrugation unit were analyzed. This study shows that as the compressive stress increases, the second-order corrugation core layer is firstly crushed, and the first-order corrugation structures gradually compacted until the failure of entire structure. The corrugation type has an obvious influence on the yield strength of the corrugation sandwich panel, and the yield strength of B-flute corrugation sandwich panel is wholly higher than that of the C-flute structure. At the same compression rate, the flute type has a significant impact on energy absorption, and the C-flute second-order corrugation sandwich panel has better bearing capacity than the B-flute structure. The second-order corrugation sandwich panel has a better bearing capacity than the first-order structure. The static compression rate has little effect on the yield strength and deformation mode. However, with the increase of the static compression rate, the corrugation sandwich panel has a better cushioning energy absorption and material utilization rate.

First order reversal curve investigation of the hard and soft magnetic phases of annealed CoFeCu nanowire arrays

2013 ◽  
Vol 429 ◽  
pp. 46-51 ◽  
Author(s):  
M. Almasi-Kashi ◽  
A. Ramazani ◽  
E. Golafshan ◽  
M. Arefpour ◽  
E. Jafari-Khamse
Keyword(s):  
Nanowire Arrays ◽  
Soft Magnetic ◽  
Magnetic Phases ◽  
First Order

scholarly journals Mechanism of the enhanced coercivity for the dual-main-phase Ce–Fe–B magnet

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Rui Han ◽  
Hongsheng Chen ◽  
Dong Zhou ◽  
Xiaoning Shi ◽  
Jiyuan Xu ◽  
...  
Keyword(s):  
Field Distribution ◽  
Exchange Coupling ◽  
Single Phase ◽  
Main Phase ◽  
High Coercivity ◽  
Switching Field ◽  
First Order ◽  
Magnetic Performance ◽  
Interaction Field ◽  
The Matrix

Abstract The high coercivity of Nd–Fe–B magnets can also be obtained in the Ce–Fe–B magnets fabricated via the dual-main-phase (DMP) method in which the high abundance Ce was used to substitute Nd(Pr). The inhomogeneous distributions of the matrix grains in the DMP magnet play a key role in the enhanced magnetic performance. Compared with the single-phase magnet, more grain boundary phases encapsulating the matrix 2:14:1 grain are formed in the DMP magnet, which reduce the exchange coupling between adjacent magnetic grains. The switching field distribution and the interaction field distribution of the Ce–Fe–B magnets were determined by the first-order-reversal curves (FORC). The switching field peaks around 6 kOe, 11 kOe and 12 kOe in the FORC distribution indicate that three major reversal components coexist for the DMP magnet. The overlapp of the second and third switching field peaks reveals the presence of a pinning interaction within individual magnetic grains with a core–shell structure, which further improve the coercivity of the magnet.

Substituent effects of rate constants for thermal [4π + 2π] cycloreversion of spiro-fused β-lactam oxadiazolines

1993 ◽  
Vol 71 (6) ◽  
pp. 907-911 ◽  
Author(s):  
Michel Zoghbi ◽  
John Warkentin
Keyword(s):  
Thermal Decomposition ◽  
Rate Constant ◽  
Rate Constants ◽  
Transition States ◽  
Substituent Effects ◽  
Ground States ◽  
Phenyl Substituent ◽  
First Order ◽  
Average Value ◽  
Carbonyl Ylide

Twelve Δ3-1,3,4-oxadiazolines in which C-2 is also C-4 of a β-lactam moiety (spiro-fused β-lactam oxadiazoline system) were thermolyzed as solutions in benzene. Substituents in the β-lactam portion affect the rate constant for thermal decomposition of the oxadiazolines to N2, acetone, and a β-lactam-4-ylidene. The total spread of first-order rate constants at 100 °C was 47-fold and the average value was 6.7 × 10−4 s−1. A phenyl substituent at N-1 or at C-3 was found to be rate enhancing, relative to methyl. At C-3, H and Cl were also rate enhancing, relative to methyl. The data are interpreted in terms of the differential effects of substituents on the stabilities of the ground states, and on the stabilities of corresponding transition states for concerted, suprafacial, [4π + 2π] cycloreversion. The first products, presumably formed irreversibly, are N2 and a carbonyl ylide. The latter subsequently fragments to form acetone (quantitative) and a β-lactam-4-ylidene.

scholarly journals Prediction of the Progressive Loss of Winding Clamping Pressure in Power Transformers

2020 ◽  
Vol 2020 ◽  
pp. 1-8
Author(s):  
Shuguo Gao ◽  
Jun Zhao ◽  
Lingming Meng ◽  
Hongliang Liu
Keyword(s):  
Mechanical Properties ◽  
Initial Pressure ◽  
Order Reaction ◽  
Power Transformers ◽  
Pressure Drops ◽  
First Order ◽  
Progressive Loss ◽  
Out Of Plane ◽  
Transformer Winding ◽  
Clamping Pressure

This paper investigates the progressive loss of winding clamping pressure resulted from thermal aging in power transformers. Firstly, out-of-plane stress-strain characteristics of aging pressboards are investigated experimentally and relationship between mechanical properties of pressboards and aging hours is established accordingly. Then, a thermal-mechanical model is built to correlate the aging time with temperature based on the first-order reaction kinetics. Based on the above investigations, the correlation between temperature and mechanical properties of pressboards is obtained and the progressive loss of clamping pressure is predicted. The results show that with the progressive softening of pressboards from aging, the clamping pressure drops linearly under 60°C and nonlinearly over 60°C. The remaining clamping pressure of a transformer winding with 30 years’ service history is only 80.12% and 51.59% of its initial pressure under 50°C and 60°C, respectively.

Assessing First-Order Emulator Inference for Physical Parameters in Nonlinear Mechanistic Models

2011 ◽  
Vol 16 (4) ◽  
pp. 475-494 ◽  
Author(s):  
Mevin B. Hooten ◽  
William B. Leeds ◽  
Jerome Fiechter ◽  
Christopher K. Wikle
Keyword(s):  
Physical Parameters ◽  
Mechanistic Models ◽  
First Order

Estimating Linear Trends: Simple Linear Regression versus Epoch Differences

2015 ◽  
Vol 28 (24) ◽  
pp. 9969-9976 ◽  
Author(s):  
Elizabeth A. Barnes ◽  
Randal J. Barnes
Keyword(s):  
Time Series ◽  
Linear Regression ◽  
Linear Trend ◽  
Simple Linear Regression ◽  
Difference Estimator ◽  
First Order ◽  
Epoch Length ◽  
Average Value ◽  
The Difference ◽  
Linear Regression Estimator

Abstract Two common approaches for estimating a linear trend are 1) simple linear regression and 2) the epoch difference with possibly unequal epoch lengths. The epoch difference estimator for epochs of length M is defined as the difference between the average value over the last M time steps and the average value over the first M time steps divided by N − M, where N is the length of the time series. Both simple linear regression and the epoch difference are unbiased estimators for the trend; however, it is demonstrated that the variance of the linear regression estimator is always smaller than the variance of the epoch difference estimator for first-order autoregressive [AR(1)] time series with lag-1 autocorrelations less than about 0.85. It is further shown that under most circumstances if the epoch difference estimator is applied, the optimal epoch lengths are equal and approximately one-third the length of the time series. Additional results are given for the optimal epoch length at one end when the epoch length at the other end is constrained.

Refined First-Order Shear Deformation Theory Models for Composite Laminates

2003 ◽  
Vol 70 (3) ◽  
pp. 381-390 ◽  
Author(s):  
F. Auricchio ◽  
E. Sacco
Keyword(s):  
Shear Deformation ◽  
Analytical Solutions ◽  
Composite Laminates ◽  
Three Dimensional ◽  
Shear Deformation Theory ◽  
Quadratic Functions ◽  
Shear Stresses ◽  
Stress Profile ◽  
First Order ◽  
Out Of Plane

In the present work, new mixed variational formulations for a first-order shear deformation laminate theory are proposed. The out-of-plane stresses are considered as primary variables of the problem. In particular, the shear stress profile is represented either by independent piecewise quadratic functions in the thickness or by satisfying the three-dimensional equilibrium equations written in terms of midplane strains and curvatures. The developed formulations are characterized by several advantages: They do not require the use of shear correction factors as well as the out-of-plane shear stresses can be derived without post-processing procedures. Some numerical applications are presented in order to verify the effectiveness of the proposed formulations. In particular, analytical solutions obtained using the developed models are compared with the exact three-dimensional solution, with other classical laminate analytical solutions and with finite element results. Finally, we note that the proposed formulations may represent a rational base for the development of effective finite elements for composite laminates.

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