scholarly journals Electroelastic Field Concentration on Elliptical Pores in Textured Media

1996 ◽  
Vol 25 (2-4) ◽  
pp. 237-244 ◽  
Author(s):  
T. D. Shermergor ◽  
V. B. Yakovlev
Keyword(s):  
Random Fields ◽  
Piezoelectric Properties ◽  
Tensor Operator ◽  
Pore Shape ◽  
Electroelastic Field ◽  
Crystalline Inclusions ◽  
The Matrix ◽  
Tensor Operators

A method of calculating the tensor operator of the electroelastic field concentration in the vicinity of two kinds of inhomogeneities (pores and crystalline inclusions) is developed. It is assumed that the shape of inhomogeneities is an ellipsoid. The materials of the matrix and/or inclusions have piezoelectric properties. Effective piezoelectric properties of textured polycrystalline media are calculated by means of the general singularity approximation of the theory of random fields. Methods for the analysis of the operators of electroelastic field concentration on the surface of the inclusion are used. The influence of the ellipsoidal pore shape on the tensor operators of electroelastic field concentration is considered. Data are shown in figures.

Parity, time, charge and Hermitian conjugations of Racah tensor operators

1983 ◽  
Vol 61 (12) ◽  
pp. 1613-1617 ◽  
Author(s):  
R. Chatterjee ◽  
J. A. Tuszyński ◽  
H. A. Buckmaster
Keyword(s):  
Magnetic Properties ◽  
Electric Properties ◽  
Tensor Operator ◽  
Matrix Elements ◽  
Selection Rules ◽  
Angular Momenta ◽  
The Matrix ◽  
Polar Tensor ◽  
The Relationship ◽  
Tensor Operators

The relationship between the parity P, time θ, charge C, and Hermitian h conjugation operators and the irreducible Racah tensor operators is reexamined. Polar tensor operators (describing electric properties) are distinguished from axial tensor operators (describing magnetic properties and angular momenta) on the basis of their individual parity and time conjugation properties. However, the effect of the Pθ product conjugation is identical for both classes and for even rank is equivalent to the Racah definition for the Hermitian conjugation of a tensor operator. It is shown that this property separates the Racah tensor operators from other vector quantities like linear momentum which cannot be represented by such operators. The selection rules due to parity and time conjugation and Hermitian conjugation that arise in the calculation of the matrix elements of the tensor operators and their products are then obtained self-consistently using the Wigner–Eckart theorem.

scholarly journals Growth of single crystals in the (Na1/2Bi1/2)TiO3–(Sr1–xCax)TiO3 system by solid state crystal growth

2021 ◽  
Author(s):  
Phan Gia Le ◽  
Huyen Tran Tran ◽  
Jong-Sook Lee ◽  
John G. Fisher ◽  
Hwang-Pill Kim ◽  
...  
Keyword(s):  
Crystal Growth ◽  
Solid State ◽  
Single Crystal ◽  
Single Crystals ◽  
Piezoelectric Properties ◽  
Single Crystal Growth ◽  
Crystal Growth Rate ◽  
Large Strains ◽  
Growth Technique ◽  
The Matrix

AbstractCeramics based on (Na1/2B1/2)TiO3 are promising candidates for actuator applications because of large strains generated by an electric field-induced phase transition. For example, the (1−x)(Na1/2Bi1/2)TiO3-xSrTiO3 system exhibits a morphotropic phase boundary at x = 0.2–0.3, leading to high values of inverse piezoelectric constant d*33, which can be further improved by the use of single crystals. In our previous work, single crystals of (Na1/2B1/2)TiO3-SrTiO3 and (Na1/2B1/2)TiO3-CaTiO3 were grown by the solid state crystal growth technique. Growth in the (Na1/2B1/2)TiO3-SrTiO3 system was sluggish whereas the (Na1/2B1/2)TiO3-CaTiO3 single crystals grew well. In the present work, 0.8(Na1/2Bi1/2)TiO3-0.2(Sr1−xCax)TiO3 single crystals (with x = 0.0, 0.1, 0.2, 0.3, 0.4) were produced by the solid state crystal growth technique in an attempt to improve crystal growth rate. The dependence of mean matrix grain size, single crystal growth distance, and electrical properties on the Ca concentration was investigated in detail. These investigations indicated that at x = 0.3 the matrix grain growth was suppressed and the driving force for single crystal growth was enhanced. Replacing Sr with Ca increased the shoulder temperature Ts and temperature of maximum relative permittivity Tmax, causing a decrease in inverse piezoelectric properties and a change from normal to incipient ferroelectric behavior.

scholarly journals Development of Delamination in Cross-Ply Laminates: Effect of Microstructure

2009 ◽  
Vol 413-414 ◽  
pp. 229-236 ◽  
Author(s):  
Zahid R. Khokhar ◽  
Ian A. Ashcroft ◽  
Vadim V. Silberschmidt
Keyword(s):  
Random Fields ◽  
Cohesive Zone ◽  
Effective Properties ◽  
Axial Stress ◽  
Damage Mechanism ◽  
Stress Concentrations ◽  
Matrix Cracks ◽  
Load Carrying ◽  
The Matrix ◽  
Cohesive Zone Elements

Various aspects of the effect of microstructural randomness exhibited by carbon fibre-reinforced cross-ply laminates on the delamination damage mechanism is investigated in this paper. In the first part, the matrix cracks with different spacings measured in experiments are simulated using finite elements in order to obtain the levels of degradation and effective properties for a composite beam loaded in bending. The results show significant levels of degradation of obtained effective properties depicting the importance of accounting for the inherent stochasticity in these laminates. In the second part of the paper, initiation of delamination at an interface between 0° and 90° layers due to stress concentrations at tips matrix cracks is simulated for a beam under tension. Stochastic cohesive zone elements with fracture parameters presented as random fields are used to model this interface in a composite. Different values of the axial stress are obtained for initiation of damage for a number of realisations based on this approach. The results emphasize the need to take into consideration the microstructural randomness in fibre-reinforced laminates for adequate predictions of damage and load carrying capacities.

scholarly journals CROP TYPE MAPPING FROM A SEQUENCE OF TERRASAR-X IMAGES WITH DYNAMIC CONDITIONAL RANDOM FIELDS

2016 ◽  
Vol III-7 ◽  
pp. 59-66 ◽  
Author(s):  
B. K. Kenduiywo ◽  
D. Bargiel ◽  
U. Soergel
Keyword(s):  
Random Fields ◽  
Conditional Random Fields ◽  
Feature Space ◽  
Ensemble Classifier ◽  
Ensemble Technique ◽  
Single Feature ◽  
The Matrix ◽  
Markov Assumption ◽  
Repeated Structure ◽  
Crop Discrimination

Crop phenology is dynamic as it changes with times of the year. Such biophysical processes also look spectrally different to remote sensing satellites. Some crops may depict similar spectral properties if their phenology coincide, but differ later when their phenology diverge. Thus, conventional approaches that select only images from phenological stages where crops are distinguishable for classification, have low discrimination. In contrast, stacking images within a cropping season limits discrimination to a single feature space that can suffer from overlapping classes. Since crop backscatter varies with time, it can aid discrimination. Therefore, our main objective is to develop a crop sequence classification method using multitemporal TerraSAR-X images. We adopt first order markov assumption in undirected temporal graph sequence. This property is exploited to implement Dynamic Conditional Random Fields (DCRFs). Our DCRFs model has a repeated structure of temporally connected Conditional Random Fields (CRFs). Each node in the sequence is connected to its predecessor via conditional probability matrix. The matrix is computed using posterior class probabilities from association potential. This way, there is a mutual temporal exchange of phenological information observed in TerraSAR-X images. When compared to independent epoch classification, the designed DCRF model improved crop discrimination at each epoch in the sequence. However, government, insurers, agricultural market traders and other stakeholders are interested in the quantity of a certain crop in a season. Therefore, we further develop a DCRF ensemble classifier. The ensemble produces an optimal crop map by maximizing over posterior class probabilities selected from the sequence based on maximum F1-score and weighted by correctness. Our ensemble technique is compared to standard approach of stacking all images as bands for classification using Maximum Likelihood Classifier (MLC) and standard CRFs. It outperforms MLC and CRFs by 7.70% and 6.42% in overall accuracy, respectively.

scholarly journals Enhanced ferro-/piezoelectric properties of tape-casting-derived Er3+-doped Ba0.85Ca0.15Ti0.9Zr0.1O3 optoelectronic thick films

2020 ◽  
Vol 9 (6) ◽  
pp. 693-702
Author(s):  
Jie Xu ◽  
Qiling Lu ◽  
Jinfeng Lin ◽  
Cong Lin ◽  
Xinghua Zheng ◽  
...  
Keyword(s):  
Piezoelectric Properties ◽  
Thick Films ◽  
Sol Gel ◽  
Matrix Material ◽  
Tape Casting ◽  
Optoelectronic Devices ◽  
Casting Method ◽  
Pure Perovskite Structure ◽  
The Matrix ◽  
Surface Morphologies

AbstractEr3+-doped Ba0.85Ca0.15Ti0.9Zr0.1O3 (xEr-BCTZ, x = 0, 0.005, 0.01, 0.015) multifunctional thick films were prepared by the tape-casting method, using sol-gel-derived nano-sized powders as the matrix material. The surface morphologies, photoluminescence, and electrical properties were investigated. Dense microstructures with pure perovskite structure were obtained in the thick films. By doping an appropriate amount of Er3−, the samples exhibit superior up-conversion photoluminescence performance and simultaneously enhanced electrical performances. In addition, relatively higher texture fractions (with the largest value of 83.5%) were realized through introducing plate-like BaTiO3 templates to make the thick film grow by the [001]c orientation. And the ferro-/piezoelectric properties of the thick films were further improved, showing potential in the applications of micro-optoelectronic devices.

Manifolds, Active Models, and Deformable Templates

2006 ◽  
Author(s):  
Ulf Grenander ◽  
Michael I. Miller
Keyword(s):  
Image Analysis ◽  
Random Fields ◽  
Transport Theory ◽  
Structural Models ◽  
Gaussian Random Fields ◽  
Deformable Templates ◽  
Infinite Products ◽  
Matrix Groups ◽  
The Matrix ◽  
Deformable Shapes

To study shape we introduce manifolds and submanifolds examined in the continuum as the generators. Transformations are constructed which are built from the matrix groups and infinite products. This gives rise to many of the widely used structural models in image analysis often termed active models, essentially the deformable templates. These deformations are studied as both diffeomorphisms as well as immersions. A calculus is introduced based on transport theory for activating these deformable shapes by taking variations with respect to the matrix groups parameterizing them. Segmentation based on activating these manifolds is examined based on Gaussian random fields and variations with respect to the parameterizations.

New relativistic crystalline electric field effective operators

1989 ◽  
Vol 67 (6) ◽  
pp. 632-633 ◽  
Author(s):  
R. Chatterjee ◽  
H. A. Buckmaster
Keyword(s):  
Electric Field ◽  
Tensor Operator ◽  
Operator Technique ◽  
Matrix Elements ◽  
Effective Operator ◽  
Crystalline Electric Field ◽  
The Matrix ◽  
Definition Of ◽  
Effective Operators

This paper shows that the use of the Landau and Lifshitz definition of the Hermitian adjoint of a tensor operator combined with the triangular rule leads to new terms in the relativistic "effective operator technique" formulation of a crystalline electric field, and that the matrix elements of these terms are significant for S-state ions.

scholarly journals Mitochondria during androgenesis in Hordeum vulgare

2014 ◽  
Vol 50 (3) ◽  
pp. 359-366 ◽  
Author(s):  
Krystyna Idzikowska
Keyword(s):  
Hordeum Vulgare ◽  
Crystalline Inclusions ◽  
The Matrix

Different number of mitochondria of varying structure was observed in particular stages of the development of barley (<em>Hordeum vulgare</em>) microspores, stimulated by the <em>in vitro</em> culture to form embryoids. This variability was reflected in different shape of sections, different ratio between total area of mitochondria profiles and area of cytoplasm sections, varying number of cristae, and different density of the matrix. Within the cristae of some mitochondria crystalline inclusions were observed. Mitochondria divided by a contraction. In the matrix of some mitochondria spheric bodies were formed. They were surrounded by one or two membranes. It is suggested that the bi-membrane forms constituted promitochandria, whereas unimembrane forms could constitute promicrobodies.

scholarly journals CROP TYPE MAPPING FROM A SEQUENCE OF TERRASAR-X IMAGES WITH DYNAMIC CONDITIONAL RANDOM FIELDS

2016 ◽  
Vol III-7 ◽  
pp. 59-66
Author(s):  
B. K. Kenduiywo ◽  
D. Bargiel ◽  
U. Soergel
Keyword(s):  
Random Fields ◽  
Conditional Random Fields ◽  
Feature Space ◽  
Ensemble Classifier ◽  
Ensemble Technique ◽  
Single Feature ◽  
The Matrix ◽  
Markov Assumption ◽  
Repeated Structure ◽  
Crop Discrimination

Crop phenology is dynamic as it changes with times of the year. Such biophysical processes also look spectrally different to remote sensing satellites. Some crops may depict similar spectral properties if their phenology coincide, but differ later when their phenology diverge. Thus, conventional approaches that select only images from phenological stages where crops are distinguishable for classification, have low discrimination. In contrast, stacking images within a cropping season limits discrimination to a single feature space that can suffer from overlapping classes. Since crop backscatter varies with time, it can aid discrimination. Therefore, our main objective is to develop a crop sequence classification method using multitemporal TerraSAR-X images. We adopt first order markov assumption in undirected temporal graph sequence. This property is exploited to implement Dynamic Conditional Random Fields (DCRFs). Our DCRFs model has a repeated structure of temporally connected Conditional Random Fields (CRFs). Each node in the sequence is connected to its predecessor via conditional probability matrix. The matrix is computed using posterior class probabilities from association potential. This way, there is a mutual temporal exchange of phenological information observed in TerraSAR-X images. When compared to independent epoch classification, the designed DCRF model improved crop discrimination at each epoch in the sequence. However, government, insurers, agricultural market traders and other stakeholders are interested in the quantity of a certain crop in a season. Therefore, we further develop a DCRF ensemble classifier. The ensemble produces an optimal crop map by maximizing over posterior class probabilities selected from the sequence based on maximum F1-score and weighted by correctness. Our ensemble technique is compared to standard approach of stacking all images as bands for classification using Maximum Likelihood Classifier (MLC) and standard CRFs. It outperforms MLC and CRFs by 7.70% and 6.42% in overall accuracy, respectively.

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