Solving the nonlinear power flow equations with an inexact Newtonmethod using GMRES

This paper presents a detailed investigation into the effectiveness of iterative methods in solving the linear system subproblem of a Newton power flow solution process. An exact Newton method employing an LU factorization has been one of the most widely used power flow solution algorithms, due to the efficient minimum degree ordering techniques that attempt to minimize fill-in. However, the LU factorization remains a computationally expensive task that can be avoided by the use of an iterative method in solving the linear subproblem. An inexact Newton method with a preconditioned Generalized Minimal Residual (GMRES) linear solver is presented as a promising alternative for solving the power flow equations. When combined with a good quality preconditioner, the Newton-GMRES method achieves a better than 50% reduction in computation, compared to Newton-LU, for two large-scale power systems: one with 3493 buses and 6689 branches, another with 8027 buses and 13765 branches     

Transient behavior of natural circulation for boiling two-phase flow (flow after pump trip)

The idea of a flow diode has been proposed to improve the pump coastdown characteristics of the internal recirculation pumps adopted by the ABWR. In this paper, the transient behavior from forced to natural circulation was experimentally investigated by simulating a pump coastdown condition for the purpose of providing an available source of information that is necessary for designing the flow diode. The results of the study showed that the transient behavior after pump coastdown was influenced by the coastdown period, the trigger velocity and the initial driving force of natural circulation. The potential of each driving factor was governed by the delay time for boiling, which is a very important parameter in natural circulation of boiling two-phase flow. In consequence, a guide for the designing of a flow diode was proposed.     

Numerical Simulation of Heat Transfer in a Three-Dimensional Enclosure with Three Chips in Various Position Arrangements

The three-dimensional laminar natural convection flow with three chips at various positions was analyzed by employing the computational fluid dynamics (CFD) code PHOENICS. The SIMPLEST algorithm with the Hybrid Scheme was used to simulate these flows. Three chips, arranged in five different positions with isothermal and insulated walls, were solved. The temperature distribution of our computational results was similar to the experimental data trend and very close to the numerical results achieved by Beak et al. The calculating results show that different chip position arrangements strongly influence the chip average temperature. The highest temperature occurred with the vertical chip arrangements. The findings herein establish a fundamental numerical study of three-dimensional heat transfer using three chips and a basis for further analysis of the associated heat transfer for more complicated chip position arrangements.     

Evolutionary Fuzzy ARTMAP Neural Networks and their Applications to Fault Detection and Diagnosis

In this paper, two mutation-based evolving artificial neural networks, which are based on the Fuzzy ARTMAP (FAM) network and evolutionary programming, are proposed. The networks utilize the knowledge base extracted from a set of data to perform search and adaptation. The performances of the two networks are assessed using benchmark problems, with the results analyzed and discussed. The effects of the network parameters are evaluated through a parametric study. The applicability of the networks is also demonstrated using a real fault detection and diagnosis task in a power generation plant. The experimental results consistently indicate the usefulness of the proposed evolutionary FAM-based networks in yielding good classification performances with parsimonious network structures.     

Investigation and Improvement of Transient Response of DVR at Medium Voltage Level

An area of interest for dynamic voltage restorer (DVR) research is the damping of transient oscillations initiated at the start and at the recovery instant from a voltage sag. Nonlinear loads, with harmonic currents close to the DVR filter resonance frequency, can also excite the resonance oscillations. To compensate voltage sags and dampen high-frequency oscillations simultaneously, an investigation of the transient response of DVR is first carried out. Possible control schemes and their effects on the oscillation attenuation are also studied. Such studied control schemes include the commonly used single voltage loop control, voltage feedback plus reference feedforward control, and double-loop control with an outer voltage loop and an inner current loop. Subsequently, an effective and simple resonance damping method is proposed by employing a closed-loop control with an embedded two-step Posicast controller. The proposed control methods have been extensively tested on a 10-kV DVR system. It is shown that the proposed damping methods improve both the transient and steady-state performance of the DVR.     

Enhancing empathy instruction using a collaborative virtual learning environment for children with autistic spectrum conditions

Empathy is an essential part of normal social function that people with autism spectrum conditions (ASCs) lack. This study uses the intervention of enhancing empathy via 3D animated scenarios of empathy in a virtual learning environment to help those deficient in empathy. Specifically, this study explores the understanding of empathy, perspective-taking and the performance of understanding of empathy via a collaborative virtual learning environment (CVLE) - empathy system. The study, which used CVLE - 3D empathy systems and three participants diagnosed with ASCs, conducted multiple baseline research for evidence of improved understanding of empathy via system usage. This experimental study lasted 5 months and the experimental results indicate that using the CVLE 3D empathy system had significant and positive effects on participant use of empathy, both within the CVLE 3D empathy system and in terms of maintaining learning in understanding empathy.     

一种静态电压稳定临界点的识别和计算方法

提出了一种用连续潮流技术识别和计算电压崩溃临界点的方法。电力系统静态电压稳定分析中,常见有鞍结型分岔点和约束诱导型分岔点。基于连续潮流的间接方法没有确定初值的困难,适合于负荷参数耦合的情形,易于识别约束型分岔点,从而适合于大型实际系统静态稳定临界点的计算。通过对中国一个实际地区系统的数值分析,表明文中所提方法是有效的。     

Strain gradient theory based on a new framework of non-local model

A new framework of non-local model for the strain energy density is proposed in this paper. The global strain energy density of the representative volume element is treated as a non-local variable and can be obtained through a special integral of the local strain energy density. The local strain energy density is assumed to be dependent on both the strain and the rotation-gradient. As a result of the non-local model, a new strain gradient theory is derived directly, in which the first and second strain gradients, as well as the triadic and tetradic stress, are introduced in the context of work conjugate. For power law hardening materials, size effects in thin metallic wire torsion and ultra-thin cantilever beam bend are investigated. It is found that the result predicted by the theoretical model is well consistent with the experimental data for the thin wire torsion. On the other hand, the calculation result for the micro-cantilever beam bend clearly shows the size effect.     

Pulsed Laser Deposition of Ba0.6Sr0.4TiO3 Thin Films and Their Optical Properties

ABSTRACT

Barium strontium titanate [Ba_0.6Sr_0.4TiO₃ or BST (60/40)] thin films were deposited on MgO (100) substrates using pulsed laser deposition. X-ray diffraction (XRD) measurements revealed that the BST thin films had epitaxially grown on the MgO (100) substrates. The surface morphology of the thin films was observed using an atomic force microscope and the grain size was found to be about 100–150 nm. The surface roughness was around 4.9 nm for a 250 nm thick film. The optical transmittance of the BST thin film was measured using a transmission mode ellipsometer. The BST/MgO configuration was highly transparent in the visible region. The optical band gap energy of the BST film, calculated by applying the Tauc relation, was 3.56 eV. Optical waveguide characteristics of the BST (60/40) thin film were determined using a prism coupler. The electro-optic (E-O) properties were measured at 632.8 nm wavelength using a phase modulation detection method. The BST film exhibited a predominately quadratic E-O behavior and the quadratic E-O coefficient was found to be 0.58 × 10^{? 17} m²/V².