scholarly journals Mechanically clamped PZT ceramics investigated by First-Order Reversal Curves diagram

2010 ◽  
Vol 4 (3) ◽  
pp. 209-214 ◽  
Author(s):  
Laurentiu Stoleriu ◽  
Cristina Ciomaga ◽  
Fabio Fochi ◽  
Pilar Ochoa ◽  
José Fernández ◽  
...  
Keyword(s):  
Bias Field ◽  
Delta Function ◽  
Ferroelectric Ceramics ◽  
High Dispersion ◽  
Gaussian Shape ◽  
Pzt Ceramics ◽  
First Order ◽  
Polycrystalline Ceramics ◽  
Non Gaussian ◽  
Cycling Experiment

The First Order Reversal Curves (FORC) diagrams method was developed for characterizing the switching properties of ferroelectrics. In the present paper, the FORC method was applied for hard Pb(Zr,Ti)O3 ceramics with symmetric and asymmetric clamping. An ideal high-oriented single-crystalline ferroelectric with rectangular P(E) loop would be characterised by a delta-function FORC distribution, while real ferroelectrics and mostly the polycrystalline ceramics show dispersed FORC distributions. All the investigated ceramics show FORC distributions with non-Gaussian shape, slightly elongated along the coercitive axis, meaning a high dispersion of the energy barriers separating the two bi-stable polarizations ?P. The degree of dispersion is enhanced by clamping. The maximum FORC coercivity is located at ~ (1.9-2) MV/m for all the hard ceramics. The FORC cycling experiment causes the reversal of the initial poling and result in a positive/negative bias on the FORC diagrams. According to the observed features, it results that FORC coercivity is more related to the nature of the material, while the bias field is more sensitive to the electrical and mechanical boundary conditions in which the ferroelectric ceramics evolves while switching.

scholarly journals Lagrangian predictability of high-resolution regional models: the special case of the Gulf of Mexico

2004 ◽  
Vol 11 (1) ◽  
pp. 47-66 ◽  
Author(s):  
P. C. Chu ◽  
L. M. Ivanov ◽  
L. H. Kantha ◽  
T. M. Margolina ◽  
O. V. Melnichenko ◽  
...  
Keyword(s):  
Gulf Of Mexico ◽  
Prediction Error ◽  
Spatial Scales ◽  
Singular Values ◽  
Forecast System ◽  
Gaussian Shape ◽  
University Of Colorado ◽  
Non Gaussian ◽  
The University ◽  
Lagrangian Drifter

Abstract. The Lagrangian prediction skill (model ability to reproduce Lagrangian drifter trajectories) of the nowcast/forecast system developed for the Gulf of Mexico at the University of Colorado at Boulder is examined through comparison with real drifter observations. Model prediction error (MPE), singular values (SVs) and irreversible-skill time (IT) are used as quantitative measures of the examination. Divergent (poloidal) and nondivergent (toroidal) components of the circulation attractor at 50m depth are analyzed and compared with the Lagrangian drifter buoy data using the empirical orthogonal function (EOF) decomposition and the measures, respectively. Irregular (probably, chaotic) dynamics of the circulation attractor reproduced by the nowcast/forecast system is analyzed through Lyapunov dimension, global entropies, toroidal and poloidal kinetic energies. The results allow assuming exponential growth of prediction error on the attractor. On the other hand, the q-th moment of MPE grows by the power law with exponent of 3q/4. The probability density function (PDF) of MPE has a symmetrical but non-Gaussian shape for both the short and long prediction times and for spatial scales ranging from 20km to 300km. The phenomenological model of MPE based on a diffusion-like equation is developed. The PDF of IT is non-symmetric with a long tail stretched towards large ITs. The power decay of the tail was faster than 2 for long prediction times.

OBSERVATION OF NON-GAUSSIAN SOURCE STRUCTURE BY HBT-IMAGING ANALYSIS

2007 ◽  
Vol 16 (10) ◽  
pp. 3193-3204
Author(s):  
AKITOMO ENOKIZONO
Keyword(s):  
Theoretical Calculations ◽  
Heavy Ion ◽  
Relativistic Heavy Ion Collisions ◽  
Imaging Analysis ◽  
Gaussian Shape ◽  
Particle Correlation ◽  
Ion Collisions ◽  
Gaussian Source ◽  
Relative Separation ◽  
Non Gaussian

We report a summary of recent RHIC measurements of hadron emission source structures by HBT-imaging analysis. Recent developments of the imaging technique which can be applied to two-particle correlation functions and high statistics data sets taken by RHIC experiments allow us to investigate the detailed source structures of hadron emissions, revealing an interesting characteristic that the source functions of charged pion pairs measured in relativistic heavy-ion collisions at [Formula: see text] are not the simple Gaussian shape but have non-Gaussian tails at large relative separation r. Also theoretical calculations to describe the observed non-Gaussian tails are reported.

Modeling for Microslip Behavior of Lap Joints Based on Non-Gaussian Rough Surfaces

2019 ◽  
Vol 142 (1) ◽  
Author(s):  
Wei Li ◽  
Wanglong Zhan ◽  
Ping Huang
Keyword(s):  
Delta Function ◽  
Lap Joints ◽  
Constitutive Relationship ◽  
Joint Interface ◽  
Lap Joint ◽  
Tangential Forces ◽  
Non Gaussian ◽  
Relationship Of ◽  
Legendre Quadrature ◽  
Effect Of Surface

Abstract A general contact model for a lap joint interface based on non-Gaussian surfaces was proposed. The effect of surface topography parameters on microslip behavior in a lap joint interface was studied. Pearson system was applied to produce non-Gaussian surfaces. Combining the topographical-dependent Zhao–Maietta–Chang (ZMC) model with the physical-related Iwan model, the nonlinear constitutive relationship of a lap interface was constructed by using Masing hypothesis. Meanwhile, the probability density function of asperity heights of an infinitely smooth surface was mathematically proved to be a delta function, verifying that the calculated value of friction in the model conforms to the physical law. Gauss-Legendre quadrature was conducted to calculate contact relations of different Pearson distribution surfaces. Furthermore, numerical results of microslip loops under oscillating tangential forces were compared with the published experiments, indicating the present model considering non-Gaussian surfaces could agree well with the experiments.

Berechnung der Spin-Spin-Koppelkonstante von HD mit nichtsingulärem Kontaktoperator / Calculation of the NMR Coupling Constant in HD by Using a Nonsingitlar Contact Operator

1973 ◽  
Vol 28 (11) ◽  
pp. 1866-1868 ◽  
Author(s):  
W. Sänger ◽  
J. Voitländer
Keyword(s):  
Delta Function ◽  
Spin Coupling ◽  
Coupling Constant ◽  
Coupling Energy ◽  
First Order ◽  
Order Energy ◽  
Spatial Part ◽  
Fermi Contact ◽  
Contact Operator ◽  
Spin Spin Coupling

The Fermi contact contribution to the nuclear spin-spin coupling constant of HD is calculated variationally. Instead of the delta-function a modified nonsingular contact spatial part is used. The self-coupling energy becomes finite and the variation of the whole second-order energy due to a non- singular first-order perturbed trial function can be carried out.

Analysis of switching properties of porous ferroelectric ceramics by means of first-order reversal curve diagrams

2006 ◽  
Vol 74 (17) ◽  
Author(s):  
Laurentiu Stoleriu ◽  
Alexandru Stancu ◽  
Liliana Mitoseriu ◽  
Daniele Piazza ◽  
Carmen Galassi
Keyword(s):  
Ferroelectric Ceramics ◽  
First Order

Reliability Analysis of Nonlinear Vibratory Systems Under Non-Gaussian Loads Using a Sensitivity-Based Propagation of Moments

2020 ◽  
Vol 142 (6) ◽  
Author(s):  
Dimitrios Papadimitriou ◽  
Zissimos P. Mourelatos ◽  
Santosh Patil ◽  
Zhen Hu ◽  
Vasiliki Tsianika ◽  
...  
Keyword(s):  
Reliability Analysis ◽  
Autocorrelation Function ◽  
Computational Cost ◽  
Random Variables ◽  
Random Coefficients ◽  
Time Dependent ◽  
Vibratory System ◽  
First Order ◽  
Non Gaussian ◽  
First Four Moments

Abstract The paper proposes a new methodology for time-dependent reliability analysis of vibratory systems using a combination of a first-order, four-moment (FOFM) method and a non-Gaussian Karhunen–Loeve (NG-KL) expansion. The approach can also be used for random vibrations studies. The vibratory system is nonlinear and is excited by stationary non-Gaussian input random processes which are characterized by their first four marginal moments and autocorrelation function. The NG-KL expansion expresses each input non-Gaussian process as a linear combination of uncorrelated, non-Gaussian random variables and computes their first four moments. The FOFM method then uses the moments of the NG-KL variables to calculate the moments and autocorrelation function of the output processes based on a first-order Taylor expansion (linearization) of the system equations of motion. Using the output moments and autocorrelation function, another NG-KL expansion expresses the output processes in terms of uncorrelated non-Gaussian variables in the time domain, allowing the generation of output trajectories. The latter are used to estimate the time-dependent probability of failure using Monte Carlo simulation (MCS). The computational cost of the proposed approach is proportional to the number of NG-KL random variables and is significantly lower than that of other recently developed methodologies which are based on sampling. The accuracy and efficiency of the proposed methodology is demonstrated using a two-degree-of-freedom nonlinear vibratory system with random coefficients excited by a stationary non-Gaussian random process.

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