Parallel genetic algorithms for optimising cellular automata models of natural complex phenomena: An application to debris flows

Cellular automata models of natural complex phenomena may depend on a set of parameters which can significantly influence the global dynamics of the simulated events. In order to reliably apply such models for predictive purposes, their parameters have to be estimated with the greatest possible accuracy. However, no standardised optimisation techniques exist in this specific research field. Genetic Algorithms (GAs) offer a possible solution: they are parallel algorithms, and can be easily implemented to exploit the simultaneous use of multiple CPUs, thereby greatly reducing the execution time.An application of a parallel GA to the optimisation of a cellular automata model for the simulation of debris flows characterised by strong inertial effects is presented. The May 1998, Curti-Sarno (Italy) debris flow has been selected as a case study for the optimisation of the model. Theoretical considerations on the dynamics of the adopted GA are discussed, with reference to two different fitness functions applied to an idealised case study.Results demonstrated the usefulness of the approach, in terms of both computing time and quality of performed simulations. Moreover, experiments on the idealised case study pointed out that the simplest fitness function (only based on the comparison of affected areas) could conveniently be adopted for calibration purposes.     

Integrated carbon nanotube field emission differential amplifier: Modeling and measurement of the common-mode rejection ratio

A novel integrated vacuum field emission (VFE) differential amplifier (diff-amp) utilizing carbon nanotube (CNT) emitters has been developed. A dual-mask microfabrication process was employed to achieve a VFE diff-amp by integrating identical CNT VFE transistors with built-in split gates and integrated anodes. The identical pair of triode amplifiers was well-matched in their device characteristics. The measured ac small-signal characteristics of the diff-amp showed a common-mode-rejection ratio (CMRR) of ~ 320 (~ 50 dB). The proposed analytical model of the CMRR was verified to be in good agreement with the experimental data. The successful implementation of the CNT diff-amp demonstrates a new way to achieve temperature and radiation tolerant VFE integrated microelectronics.     

Structural and Superconducting Property Variations with Nominal Mg Non‐Stoichiometry in MgxB2 and Its Enhancement of Upper Critical Field

By applying a combination of characterisation tools, changes in structural and superconducting properties with nominal Mg non‐stoichiometry in Mg_xB₂ are found. The non‐stoichiometry produces enhanced in‐field critical current densities (J_c's) and upper critical field / irreversibility field (H_c2/H_irr(T)) values. Upper critical fields of ～ 21 T (4.2 K) were obtained in nominal Mg‐deficient samples compared to ～ 17 T (4.2 K) for near‐stoichiometric samples.     

Robust decentralized neural networks based LFC in a deregulated power system

In this paper, a decentralized radial basis function neural network (RBFNN) based controller for load frequency control (LFC) in a deregulated power system is presented using the generalized model for LFC scheme according to the possible contracts. To achieve decentralization, the connections between each control area with the rest of system and effects of possible contracted scenarios are treated as a set of input disturbance signals. The idea of mixed H₂/H_∞ control technique is used for the training of the proposed controller. The motivation for using this control strategy for training the RBFNN based controller is to take large modeling uncertainties into account, cover physical constraints on control action and minimize the effects of area load disturbances. This newly developed design strategy combines the advantage of the neural networks and mixed H₂/H_∞ control techniques to provide robust performance and leads to a flexible controller with simple structure that is easy to implement. The effectiveness of the proposed method is demonstrated on a three-area restructured power system. The results of the proposed controllers are compared with the mixed H₂/H_∞ controllers for three scenarios of the possible contracts under large load demands and disturbances. The resulting controller is shown to minimize the effects of area load disturbances and maintain robust performance in the presence of plant parameter changes and system nonlinearities.     

Antireflection coating on InP for semiconductor detectors

Aluminum nitride thin film by RF magnetron sputtering is used to produce antireflection coating on InP. The index of refection variation of aluminum nitride for different thickness at different wavelength in the range of 400 to 1500 nm is investigated using reflection spectroscopy. Subsequent Ar+ ion implantation at 30 keV with different doses on these coated layers has been performed. The morphology of aluminum nitride after ion implantation is characterized using atomic force microscopy AFM.     

Windows平台下的汉字输入法机制及应用

作者在Windows平台下，通过对E码汉字输入法系统实现的软件研发过程，本质地认识了Windows平台下的汉字输入法系统的实现原理及其基本方法；本文对Windows IME系统的两个主要组成部分：转换引擎和界面模块以及二者之间的交互关系进行了深入的分析，并揭示了Windows平台下整个汉字输入法系统的底层运转机制。     

Maximum Cardinality Search for Computing Minimal Triangulations of Graphs

We present a new algorithm, called MCS-M, for computing minimal triangulations of graphs. Lex-BFS, a seminal algorithm for recognizing chordal graphs, was the genesis for two other classical algorithms: LEX M and MCS. LEX M extends the fundamental concept used in Lex-BFS, resulting in an algorithm that not only recognizes chordality, but also computes a minimal triangulation of an arbitrary graph. MCS simplifies the fundamental concept used in Lex-BFS, resulting in a simpler algorithm for recognizing chordal graphs. The new algorithm MCS-M combines the extension of LEX M with the simplification of MCS, achieving all the results of LEX M in the same time complexity.