An adaptive cut‐cell method for environmental fluid mechanics

In this work we present a numerical method for solving the incompressible Navier–Stokes equations in an environmental fluid mechanics context. The method is designed for the study of environmental flows that are multiscale, incompressible, variable‐density, and within arbitrarily complex and possibly anisotropic domains. The method is new because in this context we couple the embedded‐boundary (or cut‐cell) method for complex geometry with block‐structured adaptive mesh refinement (AMR) while maintaining conservation and second‐order accuracy. The accurate simulation of variable‐density fluids necessitates special care in formulating projection methods. This variable‐density formulation is well known for incompressible flows in unit‐aspect ratio domains, without AMR, and without complex geometry, but here we carefully present a new method that addresses the intersection of these issues. The methodology is based on a second‐order‐accurate projection method with high‐order‐accurate Godunov finite‐differencing, including slope limiting and a stable differencing of the nonlinear convection terms. The finite‐volume AMR discretizations are based on two‐way flux matching at refinement boundaries to obtain a conservative method that is second‐order accurate in solution error. The control volumes are formed by the intersection of the irregular embedded boundary with Cartesian grid cells. Unlike typical discretization methods, these control volumes naturally fit within parallelizable, disjoint‐block data structures, and permit dynamic AMR coarsening and refinement as the simulation progresses. We present two‐ and three‐dimensional numerical examples to illustrate the accuracy of the method. Copyright © 2008 John Wiley & Sons, Ltd.     

Structural transformations in silver nanoparticles

A molecular dynamics simulation was performed for silver clusters of 147, 309, and 561 atoms with the initial cuboctahedral habit in the temperature range 0–1000 K with an embedded atom potential for silver. Structural transitions of the silver clusters to complex twins (icosahedral habit) with coherent (111)/(111) boundaries over all edges of icosahedra were found, which started at temperatures of 50 K, 350 K, and 700 K, respectively. To analyze the structural transformations in nanoparticles, an algorithm is proposed based on a simplicial Delaunay decomposition (Delaunay triangulation). It was found that after the transition of silver nanoparticles to complex twins, the atomic motion becomes vibrational; the atoms vibrate around the sites that correspond to the vertices of the regular polyhedra. In the case of the 147-atom silver nanoparticle, the polyhedra are arranged in the following sequence, starting from the center of mass: icosahedron (12 atoms), icosododecahedron (30 atoms), icosahedron (12 atoms), dodecahedron (20 atoms), truncated icosahedron (60 atoms, isostructural with fullerene C₆₀), icosahedron (12 atoms), and one atom at the center of mass.     

新型数字式时间声音记录仪

介绍了一种用语音专用压缩硬件进行长时间语音录放的原理和数字式时间声音记录仪的特点，对一些主要部件作了说明；最后给出了软件流程框图。该仪器经使用，表明其性能达到设计要求，适合于多个领域应用。     

实现Ethernet over SDH的嵌入式系统研究

简要介绍了Ethemetover SDH(EoS)系统的结构原理，阐述和分析了EoS的LAPS协议核心技术，给出了使用FPGA完成SDH网络和以太网的连接，从而实现EOS的嵌入式系统设计方案。     

Elliptic curve cryptography on embedded multicore systems

The increasing use of network-connected embedded devices and online transactions creates a growing demand of network security for embedded systems. The security requirements, such as authentication, confidentiality and integrity, always make computationally intensive processes and can easily become the bottleneck of the related applications. In this paper we implement Elliptic Curve Cryptography (ECC) (Miller in Lecture Notes in Computer Science, vol. 218, pp. 417–426, 1985; Koblitz in Math. Comput. 48:203–209, 1987) on an embedded multicore system, and explore the task scheduling methods in different levels. First, we propose an instruction scheduling method that utilizes all the cores to perform one modular operation in parallel. Second, we perform multiple modular operations with multiple cores in parallel. The performance of those two implementations is compared and a scheduling method combining these two types of parallelism is proposed. We discuss the details of our proposed method by using an FPGA implementation of ECC over a prime field.     

The environmental impact of lightweight HCPV modules: efficient design and effective deployment

We present a life cycle analysis of a lightweight design of high concentration photovoltaic module. The materials and processes used in construction are considered to assess the total environmental impact of the module construction in terms of the cumulative energy demand and embodied greenhouse gas emissions, which were found to be 355.3 MJ and 27.9 kgCO_2eq respectively. We consider six potential deployment locations and the system energy payback times are calculated to be 0.22–0.33 years whilst the greenhouse gas payback times are 0.29–0.88 years. The emission intensities over the lifetimes of the systems are found to be 6.5–9.8 g CO_2eq/kWh, lower than those of other HCPV, PV and CSP technologies in similar locations. Copyright © 2016 John Wiley & Sons, Ltd.     

在PCB中埋置有源元件

摘要文章概述了埋置有源元件的重要意义和主要埋嵌方法。它较详细地评述了三种埋嵌有源元件方法——“先”埋嵌有源元件、“中间”埋嵌有源元件和“最后”埋嵌有源元件,而“最后”埋嵌有源元件是较好的方法。文章提供了“最后”埋置有源元件的样品与效果。     

在MCS-51单片机上移植μC/OS-Ⅱ

介绍了实时嵌入式操作系统μC/OS-Ⅱ及有关硬件移植的要点。在MCS-51系列中典型的单片机AT89C52上移植该操作系统,经过裁剪的操作系统通过了移植测试,成功加载和创建了一系列任务,并达到了实时性的要求。解决了嵌入式操作系统μC/OS-Ⅱ移植中的难题。     

基于嵌入式人体生理信号监测系统的设计

本文介绍了一种经济、实用型的家用人体生理佶号监测系统,控制终端采用S3C2410嵌入式微处理,裁剪后Linux操作系统,并用QT开发出了用户图形界面。     

Extending colorings of locally planar graphs

Suppose G is a graph embedded in S_g with width (also known as edge width) at least 264(2^g−1). If P ⊆ V(G) is such that the distance between any two vertices in P is at least 16, then any 5‐coloring of P extends to a 5‐coloring of all of G. We present similar extension theorems for 6‐ and 7‐chromatic toroidal graphs, for 3‐colorable large‐width graphs embedded on S_g with every face even‐sided, and for 4‐colorable large‐width Eulerian triangulations. © 2001 John Wiley & Sons, Inc. J Graph Theory 36: 105–116, 2001