多分量相移键控信号码速率盲估计

为解决单通道接收机同时截获到同一频带范围内的多分量相移键控信号的参数估计问题,提出了一种不经信号分离直接提取各独立信号分量码速率的盲估计算法.从理论上推导了多分量相移键控信号的二阶共轭循环自相关具有线性特性,因此可以不受干扰地提取各信号分量的码速率;进而提出了简单而有效的谱峰增强方法,与基于二阶共轭循环自相关获得的谱峰相比,用此法获得的谱峰更为清晰.仿真实验表明:用提出的算法,当双分量信号功率比为1:1且信噪比为-5 dB时,码速率估计的正确率可达98％;尤其是在单分量环境下,该算法比现有算法的性能提高4 dB以上.     

交流电力功率智能传感器粗信号处理

为提高交流电力功率性能指标的测试精度和实时性,基于相关性分析和最小二乘误差理论,研究了交流电力智能传感器的粗信号处理方法.采用最小二乘特征参数法,对交流电压和电流值的初始采样点进行估算,获得了电力功率参数.在此基础上,将最小二乘特征参数法与相关分析法进行了比较,给出了基于相关分析法和最小二乘特征参数法进行功率测试的运算量公式,并分析了运算的复杂度.实验结果表明,当干扰幅值从信号幅值的3%放宽至12%时,基于最小二乘特征参数法的粗信号处理方法与现有方法相比,其计算工作量可减少49.4%,测试误差减少了2/3,同时降低了系统的信/噪比要求.     

基于Linux下MiniGUI的图像处理GUI平台设计

目前嵌入式技术产品被广泛应用于社会的各个领域,因此,为它们设计直观、实用、易于操作的人机交互界面越发迫切.提出了一种基于MiniGUI/Embedded图像处理系统的设计方案,重点讨论了该方案所采用的图形支持系统MiniGUI、人机交互界面的设计和实现过程、事件消息驱动机制在该系统设计过程中的应用,以及图像处理系统和人...     

公路工程试验检测数据处理问题探析

在公路工程的施工技术管理中,工程试验检测是一个重要环节,同时也是公路施工质量控制和工程竣工验收工作中不可或缺的一个关键步骤。针对这样一个关键环节,从数据表达和误差表示两个方面分析公路工程试验检测数据处理问题,可供参考借鉴。     

二次蒸发制备的CuxS薄膜特性研究

在玻璃基底上通过两次蒸发的新技术制备SuxS薄膜，硫在衬底温度为160℃-200℃时与淀积在衬底上的铜直接发生反应，生成CuxS薄膜，实验发现，生成的CuxS薄与衬底温度有很大关系。160℃时生成的CuxS呈黄绿色，而在190℃左右生成的多晶状的CuxS薄膜，颜色为深绿色，通过XRD、SEM、TS等方法样品的组织结构进行了研究和讨论。     

提高标准件模具寿命的有效途径

在汽车标准件的生产过程中,模具起着主导作用,只有提高模具寿命,才能起到事半功倍的效果。有效提高标准件模具的寿命,除了需要合理选用模具的材料,合理设计模具的结构,做好模具的热处理以及加工与抛光外,还要选用恰当的润滑剂和精度高的设备,同时要加强管理,提高操作者的素质。     

From Twitter to detector: Real-time traffic incident detection using social media data

The effectiveness of traditional incident detection is often limited by sparse sensor coverage, and reporting incidents to emergency response systems is labor-intensive. We propose to mine tweet texts to extract incident information on both highways and arterials as an efficient and cost-effective alternative to existing data sources. This paper presents a methodology to crawl, process and filter tweets that are accessible by the public for free. Tweets are acquired from Twitter using the REST API in real time. The process of adaptive data acquisition establishes a dictionary of important keywords and their combinations that can imply traffic incidents (TI). A tweet is then mapped into a high dimensional binary vector in a feature space formed by the dictionary, and classified into either TI related or not. All the TI tweets are then geocoded to determine their locations, and further classified into one of the five incident categories.We apply the methodology in two regions, the Pittsburgh and Philadelphia Metropolitan Areas. Overall, mining tweets holds great potentials to complement existing traffic incident data in a very cheap way. A small sample of tweets acquired from the Twitter API cover most of the incidents reported in the existing data set, and additional incidents can be identified through analyzing tweets text. Twitter also provides ample additional information with a reasonable coverage on arterials. A tweet that is related to TI and geocodable accounts for approximately 5% of all the acquired tweets. Of those geocodable TI tweets, 60–70% are posted by influential users (IU), namely public Twitter accounts mostly owned by public agencies and media, while the rest is contributed by individual users. There is more incident information provided by Twitter on weekends than on weekdays. Within the same day, both individuals and IUs tend to report incidents more frequently during the day time than at night, especially during traffic peak hours. Individual tweets are more likely to report incidents near the center of a city, and the volume of information significantly decays outwards from the center.     

Virtual 3D city model as a priori information source for vehicle localization system

This paper aims at demonstrating the usefulness of integrating virtual 3D models in vehicle localization systems. Usually, vehicle localization algorithms are based on multi-sensor data fusion. Global Navigation Satellite Systems GNSS, as Global Positioning System GPS, are used to provide measurements of the geographic location. Nevertheless, GNSS solutions suffer from signal attenuation and masking, multipath phenomena and lack of visibility, especially in urban areas. That leads to degradation or even a total loss of the positioning information and then unsatisfactory performances. Dead-reckoning and inertial sensors are then often added to back up GPS in case of inaccurate or unavailable measurements or if high frequency location estimation is required. However, the dead-reckoning localization may drift in the long term due to error accumulation. To back up GPS and compensate the drift of the dead reckoning sensors based localization, two approaches integrating a virtual 3D model are proposed in registered with respect to the scene perceived by an on-board sensor. From the real/virtual scenes matching, the transformation (rotation and translation) between the real sensor and the virtual sensor (whose position and orientation are known) can be computed. These two approaches lead to determine the pose of the real sensor embedded on the vehicle. In the first approach, the considered perception sensor is a camera and in the second approach, it is a laser scanner. The first approach is based on image matching between the virtual image extracted from the 3D city model and the real image acquired by the camera. The two major parts are: 1. Detection and matching of feature points in real and virtual images (three features points are compared: Harris corner detector, SIFT and SURF). 2. Pose computation using POSIT algorithm. The second approach is based on the on–board horizontal laser scanner that provides a set of distances between it and the environment. This set of distances is matched with depth information (virtual laser scan data), provided by the virtual 3D city model. The pose estimation provided by these two approaches can be integrated in data fusion formalism. In this paper the result of the first approach is integrated in IMM UKF data fusion formalism. Experimental results obtained using real data illustrate the feasibility and the performances of the proposed approaches.     

新型舰载ESM信号处理系统

随着雷达技术的发展，电磁环境越来越密集，雷达信号的类型超来超复杂，这就对ＥＳＭ信号处理提出了更高的要求。基于目前ＥＳＭ信号的处理方法，本文提出了一种先进的工程上可实现的新一代舰载ＥＳＭ信号处理系统。