Revealing the dominant factor of domain boundary resistance on bulk conductivity in lanthanum lithium titanates

Perovskite-type lithium lanthanum titanates(LLTO)display a high bulk ionic conductivity and are considered a promising electrolyte for building up to advanced solid-state Li-ion batteries.The LLTO crystals contain a high concentration of intrinsically formed 90ο-rotated domain boundaries(DBs)serving as barriers to bulk Li-ion conduction.However,the mechanism of how the DB concentration and DB resistance can compete with each other to determine the bulk conductivity of LLTO is still unknown.Here we report a comprehensive study of LLTO compounds,aimed to unravel the mechanism and hence explore new path(s)for further improving the conductivity of this material.Our results show that both the sintering temperature and chemical composition can affect significantly the domain structures in LLTO.It is found that a decrease in the DB concentration is always accompanied by increased DB resistance due to the increased lattice mismatch at DBs,and vice versa.By unifying the electrochemical impedance spectroscopy and transmission electron microscopy analysis,it is clearly shown that the high DB resistance,instead of DB concentration,acts as the dominant factor governing the bulk conductivity of LLTO.The results thus renew the conventional understanding of the bulk Li-ion conduction in LLTO and shed light on developing novel LLTO electrolyte materials with improved ionic conductivity.

A Molecular Dynamics Study on the (1120) Domain Boundary Structures in Epitaxial Wurtzite GaN

A computer program has been developed for the moIlcular dynamics calculation of ionic orstrong-ionic covalent systems. Ewald summation algorithm and Keating potentiaI model areadopted to calculate the long-range Coulomb interaction and the short-range bonding forces,respectively. A theoretical study on the domain boundary structures in epitaxial wurtzite GaN film is accomplished with the program. The calculation result is used in the structure formationexplanation of an interesting defect observed by HREM experiment.

A TIME DOMAIN BOUNDARY ELEMENT METHOD FOR WATER-SOLID IMPACT ANALYSIS

A reciprocal theorem of dynamics for potential flow problems is first derived by means of the Laplace transform in which the compressibility of water is taken into account. Based on this theorem, the corresponding time-space boundary integral equation: is obtained. Then, a set of time domain boundary element equations with recurrence form is immediately formulated through discretization in both time and boundary. After having carried out the numerical calculation two solutions are found in which a rigid semicircular cylinder and a rigid wedge with infinite length suffer normal impact on the surface of a half-space fluid. The results show that the present method is more efficient than the previous ones.

TIME DOMAIN BOUNDARY ELEMENT METHODS FOR THE NEUMANN PROBLEM： ERROR ESTIMATES AND ACOUSTIC PROBLEMS

We investigate time domain boundary element methods for the wave equation in R3, with a view towards sound emission problems in computational acoustics. The Neumann problem is reduced to a time dependent integral equation for the hypersingular operator, and we present a priori and a posteriori error estimates for conforming Galerkin approxima- tions in the more general case of a screen. Numerical experiments validate the convergence of our boundary element scheme and compare it with the numerical approximations ob- tained from an integral equation of the second kind. Computations in a half-space illustrate the influence of the reflection properties of a flat street.

THE ANALYTICAL SOLUTION FOR HELMHOLTZ BOUNDARY PROBLEM IN NON-HORIZONTALLY STRATIFIED DOMAINS

There are N domains Dj(j=0,1,...,N-1) of different physical parameters in the whole space and their interfaces S,are non-horizontally smooth curved surfaces. The following boundary problem is called Hclinholiz boundary problem:The analytical solution of the above problem is given in this paper.

Orientational Domains at Room Temperature in La_(0.33) Ca_(0.67) MnO_3 Perovskite

Orientational domains at room temperature in orthorhombic perovskite La 0.33 Ca 0.67 MnO 3 were studied by group theory and observed systematically using transmission electron microscopy. There are six orientational variants ( A, A', B,B', C and C' ) in orthorhombic perovskite La 0.33 Ca 0.67 MnO 3. Their orthorhombic b O directions are parallel to the a P, b P and c P directions of the cubic prototypic perovskite, respectively. In each case there are two orientational variants (e.g., A and A' ) with their a O and c O axes interchanged. Among the possible 15 boundaries between these 6 variants there are only two types of domain boundaries: (1) m<100> boundaries C'/C, A'/A, and B'/B. (2) m<110> boundaryies C'/A, C'/A', C'/B, C'/B', C/A, C/A', C/B, C/B', B'/A, B'/A', B/A, and B/A' .

A Novel Method for Prediction of Protein Domain Using Distance-Based Maximal Entropy

Detecting the boundaries of protein domains is an important and challenging task in both experimental and computational structural biology. In this paper, a promising method for detecting the domain structure of a protein from sequence information alone is presented. The method is based on analyzing multiple sequence alignments derived from a database search. Multiple measures are defined to quantify the domain information content of each position along the sequence. Then they are combined into a single predictor using support vector machine. What is more important, the domain detection is first taken as an imbal- anced data learning problem. A novel undersampling method is proposed on distance-based maximal entropy in the feature space of Support Vector Machine （SVM）. The overall precision is about 80%. Simulation results demonstrate that the method can help not only in predicting the complete 3D structure of a protein but also in the machine learning system on general im- balanced datasets.

Introducing the nth-Order Features Adjoint Sensitivity Analysis Methodology for Nonlinear Systems (nth-FASAM-N): I. Mathematical Framework

This work presents the “nth-Order Feature Adjoint Sensitivity Analysis Methodology for Nonlinear Systems” (abbreviated as “nth-FASAM-N”), which will be shown to be the most efficient methodology for computing exact expressions of sensitivities, of any order, of model responses with respect to features of model parameters and, subsequently, with respect to the model’s uncertain parameters, boundaries, and internal interfaces. The unparalleled efficiency and accuracy of the nth-FASAM-N methodology stems from the maximal reduction of the number of adjoint computations (which are considered to be “large-scale” computations) for computing high-order sensitivities. When applying the nth-FASAM-N methodology to compute the second- and higher-order sensitivities, the number of large-scale computations is proportional to the number of “model features” as opposed to being proportional to the number of model parameters (which are considerably more than the number of features).When a model has no “feature” functions of parameters, but only comprises primary parameters, the nth-FASAM-N methodology becomes identical to the extant nth CASAM-N (“nth-Order Comprehensive Adjoint Sensitivity Analysis Methodology for Nonlinear Systems”) methodology. Both the nth-FASAM-N and the nth-CASAM-N methodologies are formulated in linearly increasing higher-dimensional Hilbert spaces as opposed to exponentially increasing parameter-dimensional spaces thus overcoming the curse of dimensionality in sensitivity analysis of nonlinear systems. Both the nth-FASAM-N and the nth-CASAM-N are incomparably more efficient and more accurate than any other methods (statistical, finite differences, etc.) for computing exact expressions of response sensitivities of any order with respect to the model’s features and/or primary uncertain parameters, boundaries, and internal interfaces.

Effect of electric boundary conditions on crack propagation in ferroelectric ceramics

In this paper, the effect of electric boundary conditions on Mode I crack propagation in ferroelectric ceramics is studied by using both linear and nonlinear piezoelectric fracture mechanics. In linear analysis, impermeable cracks under open circuit and short circuit are analyzed using the Stroh formalism and a rescaling method. It is shown that the energy release rate in short circuit is larger than that in open circuit. In nonlinear analysis, permeable crack conditions are used and the nonlinear effect of domain switching near a crack tip is considered using an energy-based switching criterion proposed by Hwang et al.（Acta Metal. Mater.,1995）. In open circuit, a large depolarization field induced by domain switching makes switching much more diffcult than that in short circuit. Analysis shows that the energy release rate in short circuit is still larger than that in open circuit, and is also larger than the linear result. Consequently,whether using linear or nonlinear fracture analysis, a crack is found easier to propagate in short circuit than in open circuit, which is consistent with the experimental observations of Kounga Njiwa et al.（Eng. Fract. Mech., 2006）.

Drinfeld twist and the domain wall partition function of the eight-vertex model

With the help of the F-basis provided by the Drinfeld twist or factorising F-matrix for the spatial optical soliton model associated with the eight-vertex model, we calculate the partition function for the eight-vertex model on an N ×N square lattice with domain wall boundary condition.

Domain boundaries in silicene:Density functional theory calculations on electronic properties

By using density functional theory(DFT)-based first-principles calculations, the structural stability and electronic properties for two kinds of silicene domain boundaries, forming along armchair edge and zigzag edge, have been investigated. The results indicate that a linkage of tetragonal and octagonal rings(4|8) appears along the armchair edge, while a linkage of paired pentagonal and octagonal rings(5|5|8) appears along the zigzag edge. Different from graphene, the buckling properties of silicene lead to two mirror symmetrical edges of silicene line-defect. The formation energies indicate that the 5|5|8 domain boundary is more stable than the 4|8 domain boundary. Similar to graphene, the calculated electronic properties show that the 5|5|8 domain boundaries exhibit metallic properties and the 4|8 domain boundaries are half-metal.Both domain boundaries create the perfect one-dimensional(1D) metallic wires. Due to the metallic properties, these two kinds of nanowires can be used to build the silicene-based devices.

Fifth-Order Comprehensive Adjoint Sensitivity Analysis Methodology for Nonlinear Systems (5th-CASAM-N): II. Paradigm Application to a Bernoulli Model Comprising Uncertain Parameters

This work presents the application of the recently developed “Fifth-Order Comprehensive Adjoint Sensitivity Analysis Methodology for Nonlinear Systems (5th-CASAM-N)” to a simplified Bernoulli model. The 5th-CASAM-N builds upon and incorporates all of the lower-order (i.e., the first-, second-, third-, and fourth-order) adjoint sensitivities analysis methodologies. The Bernoulli model comprises a nonlinear model response, uncertain model parameters, uncertain model domain boundaries and uncertain model boundary conditions, admitting closed-form explicit expressions for the response sensitivities of all orders. Illustrating the specific mechanisms and advantages of applying the 5th-CASAM-N for the computation of the response sensitivities with respect to the uncertain parameters and boundaries reveals that the 5th-CASAM-N provides a fundamental step towards overcoming the curse of dimensionality in sensitivity and uncertainty analysis.

AN ITERATIVE PROCEDURE FOR DOMAIN DECOMPOSITION METHOD OF SECOND ORDER ELLIPTIC PROBLEM WITH MIXED BOUNDARY CONDITIONS

This paper is devoted to study of an iterative procedure for domain decomposition method of second order elliptic problem with mixed boundary conditions (i.e., Dirichlet condition on a part of boundary and Neumann condition on the another part of boundary). For the pure Dirichlet problem, Marini and Quarteroni [3], [4] considered a similar approach, which is extended to more complex problem in this paper.

Non-rigid registration of medical images based on S^(1/2)(Δ_(mn)^((2)))non-tensor product Bspline

In this study,a non-tensor product B-spline algorithm is applied to the search space of the registration process,and a new method of image non-rigid registration is proposed.The tensor product B-spline is a function defined in the two directions of x and y,while the non-tensor product B-spline S^(1/2)(Δ_(mn)^((2)))is defined in four directions on the 2-type triangulation.For certain problems,using non-tensor product B-splines to describe the non-rigid deformation of an image can more accurately extract the four-directional information of the image,thereby describing the global or local non-rigid deformation of the image in more directions.Indeed,it provides a method to solve the problem of image deformation in multiple directions.In addition,the region of interest of medical images is irregular,and usually no value exists on the boundary triangle.The value of the basis function of the non-tensor product B-spline on the boundary triangle is only 0.The algorithm process is optimized.The algorithm performs completely automatic non-rigid registration of computed tomography and magnetic resonance imaging images of patients.In particular,this study compares the performance of the proposed algorithm with the tensor product B-spline registration algorithm.The results elucidate that the proposed algorithm clearly improves the accuracy.

A study on boundary integral equations for dynamic elastoplastic analysis for the plane problem by TD-BEM

The equivalent stress fundamental solution for the elastoplastic dynamic plane strain problem is proposed to transform the virtual work in the third direction to the plane.Subsequently,based on Betti reciprocal theorem,by adopting the time dependent fundamental solutions in terms of displacement,traction and equivalent stress,the boundary integral equations for dynamic elastoplastic analysis for the plane strain problem are established.The establishment procedures for the displacement and the stress boundary integral equations,together with the stress equation at boundary points,are presented in details,while the standard discretization both in time and space under the frame of time domain boundary element method(TD-BEM)and the solution of the algebraic equations are also briefly stated.Two verification examples are presented from different viewpoints,for elastic and elastoplastic analysis,for 1-D and 2-D geometries,and for finite and infinite domains.The TD-BEM formulation for dynamic elastoplastic analysis is presented for the plane strain problem as an example,where the formulation is also applicable for the plane stress problem by properly transforming the elastic constants and adopting the corresponding fundamental solutions.

DOMAIN BOUNDARIES IN FERROELECTRICS

Present paper is a brief review of the information and existing approaches in the study of domain walls in ferroelectric materials.In the framework of the continuum approach the structure of 180°and 90°domain walls was considered.The results of calculation of width and energy of domain walls were compared with those obtained from ab initio calculations and experimental data.Factors conducive to the broadening of domain boundaries are discussed such as profile temperature fluctuation,capture to nearby defects and surface impact.The structure of charged domain walls was considered under the conditions of screening by free carriers.The structure and characteristics of the moving domain wall are discussed:the local effective mass,the top speed and the mobility.The lateral motion of domain walls in the lattice potential relief in the general case creeping mode is investigated.The factors that control the macroscopic movement of domain walls are studied:an effective quasi-elasticity coefficient and nonlocal effective mass associated with involvement in the movement of the elastic medium surrounding wall.Natural frequency of translational oscillations of domain boundaries and the influence of the size effect were estimated.The interaction of domain walls with different types of defects and their effect on the deformation profile and features of the motion of domain walls are considered.

Fatigue phenomena in thin ferroelectric films stimulated by repeated switching of the polarization

With the use of techniques of Sawyer
Tower and Mertz method regularities of the origin of "fatigue"in thin ferroelectric films of lead titanate and lead zirconate titanate have been investigated in the fields above coercive.We propose a model to explain the experimentally observed switching-dependent fatigue processes by the motion of charged dislocations in an applied external alternating electric field.