μC/OS-Ⅱ事件标志组系统漏洞及其修复

μC/OS-Ⅱ的事件标志组在任务间的同步和通信中有着不可忽视的作用。在应用过程中,发现事件标志组存在系统缺陷,通过对其进行深入分析,提出了解决问题的方案,本文详细地描述了解决方案的具体方式及步骤。该解决方案没有改变系统函数接口,对系统实时性影响也较小,有很强的兼容性及可行性。     

Optimistic Byzantine fault tolerance

The primary concern of traditional Byzantine fault tolerance is to ensure strong replica consistency by executing incoming requests sequentially according to a total order. Speculative execution at both clients and server replicas has been proposed as a way of reducing the end-to-end latency. In this article, we introduce optimistic Byzantine fault tolerance. Optimistic Byzantine fault tolerance aims to achieve higher throughput and lower end-to-end latency by using a weaker replica consistency model. Instead of ensuring strong safety as in traditional Byzantine fault tolerance, nonfaulty replicas are brought to a consistent state periodically and on-demand in optimistic Byzantine fault tolerance. Not all applications are suitable for optimistic Byzantine fault tolerance. We identify three types of applications, namely, realtime collaborative editing, event stream processing, and services constructed with conflict-free replicated data types, as good candidates for applying optimistic Byzantine fault tolerance. Furthermore, we provide a design guideline on how to achieve eventual consistency and how to recover from conflicts at different replicas. In optimistic Byzantine fault tolerance, a replica executes a request immediately without first establishing a total order of the message, and Byzantine agreement is used only to establish a common state synchronization point and the set of individual states needed to resolve conflicts. The recovery mechanism ensures both replica consistency and the validity of the system by identifying and removing the operations introduced by faulty clients and server replicas.     

新疆极端降水事件时空变化特征研究

基于新疆1960—2011年的日降水量数据,选取持续干燥指数、持续湿润指数、年总降水量、强降水天数、强降水量、1 d最大降水量、5 d最大降水量和普通日降水强度8个极端降水指标,采用线性倾向率、Mann-Kendall突变检验及主成分分析法研究新疆极端降水的时空分布特征及演变趋势。结果表明:时间变化上,新疆极端降水的持续湿润指数均呈上升趋势,持续干燥指数呈下降趋势,表明新疆降水量总体呈增加趋势;空间变化上,南疆、北疆极端降水指标的年际变化表现出明显差异,北疆湿润指数大、年际变化率大,南疆湿润指数小、年际变化率小;极端降水指标基本上在1986年、1987年发生突变,各指标突变前后的变化率存在明显差异;时间上的主成分分析表明降水量整体增加,干燥程度下降;空间上的主成分分析表明,北疆降水量多于南疆,南疆较北疆干旱。     

复杂电磁干扰环境下的C6000 DSP自举方法

对TMS320C620X／670XDSP的存储结构和特点进行分析,采用分两次生成ROM文件的方式实现TMS320C620X／670XDSP自举,并阐述了该自举方法的关键过程。通过该自举方法,程序在片内RAM中执行,预置参数和常量从外部ROM中读取。结合软件三模冗余,该自举方法可以防止复杂电磁干扰环境下单粒子翻转效应。该方法已得到实际应用,行之有效。     

Personal driving diary: Automated recognition of driving events from first-person videos

In this paper, we introduce the concept of personal driving diary. A personal driving diary is a multimedia archive of a person’s daily driving experience, describing important driving events of the user with annotated videos. This paper presents an automated system that constructs such multimedia diary by analyzing videos obtained from a vehicle-mounted camera. The proposed system recognizes important interactions between the driving vehicle and the other actors in videos (e.g., accident, overtaking, etc.), and labels them together with its contextual knowledge on the vehicle (e.g., mean velocity) to construct an event log. A decision tree based activity recognizer is designed, detecting driving events of vehicles and pedestrians from the first-person view videos by analyzing their trajectories and spatio-temporal relationships. The constructed diary enables efficient searching and event-based browsing of video clips, which helps the users when retrieving videos of dangerous situations. Our experiment confirms that the proposed system reliably generates driving diaries by annotating the vehicle events learned from training examples.     

Controller Synthesis with Highly Simplified Linear Constraints

This paper deals with the problem of forbidden states in safe Petri nets to obtain a maximally permissive controller. To prevent the system from entering the forbidden states, assigning some constraints to them is possible. The constraints can be enforced on the system using control places. When the number of forbidden states is large, a large number of constraints should be assigned to them. This results in a large number of control places being added to the model of the system, which causes a complicated model. Some methods have been proposed to reduce the number of constraints. Nevertheless, they do not always give the best results. In this paper, two ideas are offered to reduce the number of constraints, giving a more simplified controller.     

声发射技术在地压监测中的应用

对某矿的采空区围岩试样进行了单轴压缩声发射实验,得到了岩石破坏时能率、事件率等声发射参数值,根据这些数值对声发射监测系统参数进行了设置;通过对声发射监测系统长期运行结果的统计,总结出了井下多种活动即岩石声发射、打钻、爆破、人工破碎大块矿石、放矿、敲击的波形及各类波形的参数范围;确定了以能率、事件率为特征的采空区失稳判据,为判断地压灾害提供了可靠依据。     

汉语块分析评测任务设计

该文主要介绍了目前中文信息学会句法分析评测CIPS-ParsEval-2009中的三项块分析评测任务 基本块分析、功能块分析和事件描述小句识别的设计理念、判定标准和相关资源构建方法。然后给出了这三项目前的主要评测结果并对相关内容进行了简要分析。最后通过相关统计数据分析和国内外相关研究评述,总结了这三项评测任务的主要特色。     

嵌入式Linux和Qtopia下矩阵键盘输入的实现

详细介绍了基于嵌入式Linux和Qtopia的矩阵键盘输入实现方法。通过重载Qt的事件过滤器,结合信号和槽机制,利用两级状态处理及有效输入的界定,来简化输入过程,减少按键次数,提高输入效率。同时利用Qtopia的图形显示,使输入界面清晰,更适用于嵌入式终端设备。     

基于能量特征的脑电信号特征提取与分类

为了快速、有效地提取脑电特征,提高分类正确率,采用带通滤波和小波包分析的方法提取Mu、Beta节律对应的脑电信号,在时域范围内,将信号幅度的平方作为能量特征值;在频域范围内,采用AR模型功率谱估计法所得的功率谱密度作为能量特征值.根据运动想象脑电信号特点,构造左右通道信号能量差值的符号特性作为分类判别依据,进行分类测试,方法简单.初步实验结果表明,所利用的两种方法的分类正确率达87.857%.