Recent developments of free mesh method

This paper presents the recent advances on Free Mesh Method by the authors. In this method, elements are locally created at each node in an autonomous manner, so that only nodal information is necessary without global meshing. The method has been tested with various applications such as heat conduction, fluid and fracture analyses, and reliable solutions were obtained with good parallel efficiency. Modifications of Free Mesh Method have been further proposed, and the accuracy of solution has been improved.The overall review of the recent advances has demonstrated the effectiveness of Free Mesh Method. Copyright © 2000 John Wiley & Sons, Ltd.     

Shift of redox potential and kinetics in Lix(MnyFe1−y)PO4

The relatively high redox potential in the olivine-type LiMPO₄ (M = Mn, Fe, Co, Ni) materials has largely been explained by the M–O–P inductive effect which increases the ionic character of transition metal atoms. Here, we identify the additional perturbative effect that slightly but systematically shifts the redox potential. The substitution of iron by manganese in the olivine LiMPO₄ framework raises both of the Fe³⁺/Fe²⁺ and Mn³⁺/Mn²⁺ redox potentials by ∼0.1 V. The overall volume expansion upon Mn substitution in the whole Li_x(Mn_yFe_1−y)PO₄ system possibly increases the average metal-oxide bond length and hence the ionicity of each transition metal. The voltage shift in a single cell is small but should be significant in a larger-scale battery where there exist a large number of series connections. The kinetic shift for each of the Fe³⁺/Fe²⁺ and Mn³⁺/Mn²⁺ redox reactions is also investigated.     

Neural Network-Based Inverse Analysis for Defect Identification with Laser Ultrasonics

This paper describes an application of the neural network-based inverse analysis method to the identification of a surface defect hidden in a solid, using laser ultrasonics. The inverse analysis method consists of three subprocesses. First, sample data of identification parameters versus dynamic responses of displacements at several monitoring points on the surface are calculated using the dynamic finite-element method. Second, the back-propagation neural network is trained using the sample data. Finally, the well-trained network is utilized for defect identification. Fundamental performance of the method is examined quantitatively and in detail, through both numerical simulations and laser ultrasonics experiments. Locations and depths of vertical defects are successfully estimated within 12.5% and 4.1% errors relative to the specimen thickness, respectively.     

Ambient pressure synthesis of La2LiHO3 as a solid electrolyte for a hydrogen electrochemical cell

The capability of La₂LiHO₃ as a H⁻ conductive solid electrolyte has recently been demonstrated, which has suggested the possibility of developing electrochemical devices based on H⁻ conduction. However, the performance of La₂LiHO₃ as a solid electrolyte has not yet been fully clarified. In this study, we prepared La₂LiHO₃ sintered pellets by a conventional solid-state reaction with LiH flux under ambient pressure and characterized the crystal structure and thermal stability (to moisture, ambient air, and oxygen) by neutron and X-ray diffraction measurements. The produced sintered pellets exhibited an activation energy of 69.2 kJ/mol, which is consistent with the value of the sample synthesized by the high-pressure method. The gas-sealing properties of the sintered La₂LiHO₃ pellets as the H⁻ conductive solid electrolyte were confirmed by measuring the electromotive force using a hydrogen concentration cell.     

Task transmission control with dynamic lightpath setup for constant processing delay in an optical grid

This paper proposes a task transmission control with dynamic lightpath setup in an optical grid. In our proposed method, a job manager changes the number of tasks in a resource manager dynamically so as to maintain a constant processing delay. It leads to effective utilization of computing resource. I‐PD control is applied to maintain efficient network management. Furthermore, in order to avoid frequent lightpath setup process, multiple lightpaths are established simultaneously by our proposed algorithm. Numerical results show the effectiveness of the proposed task transmission method. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Controlled Polarizability of One‐Nanometer‐Thick Oxide Nanosheets for Tailored,High‐κ Nanodielectrics

An important challenge in current microelectronics research is the development of techniques for making smaller, higher‐performance electronic components. In this context, the fabrication and integration of ultrathin high‐κ dielectrics with good insulating properties is an important issue. Here, we report on a rational approach to produce high‐performance nanodielectrics using one‐nanometer‐thick oxide nanosheets as a building block. In titano niobate nanosheets (TiNbO₅, Ti₂NbO₇, Ti₅NbO₁₄), the octahedral distortion inherent to site‐engineering by Nb incorporation results in a giant molecular polarizability, and their multilayer nanofilms exhibit a high dielectric constant (160–320), the largest value seen so far in high‐κ nanofilms with thickness down to 10 nm. Furthermore, these superior high‐κ properties are fairly temperature‐independent with low leakage‐current density (<10^?7 A cm^?2). This work may provide a new recipe for designing nanodielectrics desirable for practical high‐κ devices.     

Recursive distribution method for probabilistic fracture mechanics

This paper proposes a new method for Probabilistic Fracture Mechanics (PFM). The present method gives a recursive formula for a joint probability distribution function of crack geometry, which is obtained from random variables of the initial crack geometry and a deterministic time-evolution law of the variables. A numerical example of Light Water Reactor (LWR)'s piping is solved by the present method, and the results are compared with those of the Monte Carlo (MC) method. It is clearly shown that both results agree sufficiently well, while CPU time of the present method is remarkably short.     

Parallel computing for incompressible flow using a Nodal-Based method

In this paper, the development of a seamless system for parallel flow analysis using the “free-mesh method”, which is a kind of meshless method, is described. The system consists of two main parts: the computation of the global mass, advection, diffusion, gradient, and divergence matrices, and the time integration by the decoupled method with respect to velocity and pressure. This system is quite compatible with the parallel environment because the matrices are independently computed node-by-node without any node-element connectivity information, and furthermore because the fractional step method, with the interpolation functions for velocity and pressure being of equal order, is used with the conjugate gradient solver for the time integration. A parallel efficiency of approximately 83 was achieved for a large-scale problem with 480,000 degrees of freedom using 16 processors.     

A parallel triangular decomposition algorithm on a workstation network with application to structural vibration analysis

This paper presents a parallel triangular decomposition algorithm for banded symmetric matrices and its application to structural vibration analysis, which gives high rates of parallel efficiency on a workstation network. In case of decomposition of a matrix with halfbandwidth 822, the working efficiency rate was 84% using a network of six workstations (SUN SparcStation 20s). The algorithm provides a high rate of working efficiency in parallel environment with local memory, even if the communication time is considerably longer than the operation time. As an application of the algorithm, a finite element (FE) system for structural vibration analysis with the parallel decomposition algorithm was developed on the above workstation network and a model with more than 100,000 degrees of freedom (DOFs) was successfully analyzed by the system. The computation time for the model with 10,752 DOFs and halfbandwidth 822 was 3,661 sec by the present parallel system, whereas the computation time by a single workstation was 14,335 sec.     

Direct analysis method for probabilistic fracture mechanics

A new method for solving problems of probabilistic fracture mechanics (PFM) is proposed. A process of crack growth is reduced into an iterative integration equation with respect to the probabilistic distribution functions of crack geometry using approximate independence, which we have introduced. The integration equation which has a form of Stieltjes integral is solved by a numerical method. Some PFM problems are solved using the present method, and the results are compared with those by the MC method. Failure probabilities obtained from both calculations agree well. Execution time of the present method is shown to be remarkably short.