面向树形接入网络的可扩展IPTV视频传输质量监测方法研究

IPTV数据传输质量检测是IPTV应用部署中需要攻克的关键技术。目前,如何实现接入网中IPTV视频质量监测还缺少系统的研究。本文针对目前广泛采用的树形接入网拓扑,提出基于逐跳延时变化(PHDV)的视频传输质量检测和故障定位方法。该方法利用视频流实时性和连续性的特点,通过对交换机输出缓冲区队列长度变化的实时监测定位网络中影响IPTV视频传输质量的拥塞点。分析表明,本文提出的方法可扩展性强,监测逻辑在网络中部署实现简单,具有较强的实用价值。     

基于增量式特征基背景模型的运动目标检测

背景差法是目标运动检测的主流方法,关键在于背景模型自适应更新.针对传统特征基背景模型批处理方式计算量大、更新速度慢的问题,采用增量式主成分分析来建立特征基背景模型.首先计算样本图像的初始背景图像,然后采用CCFIPCA算法更新特征基背景模型,最后通过输入帧和重建帧的欧氏距离检测前景运动目标.算法以视频帧整体来建立背景模型,克服了混合高斯模型和核密度估计以孤立像素点建模的不足,提高了背景建模的鲁棒性.在SIMULINK下的仿真实验表明,算法能很好地适应高速公路交通场景动态变化,在有光线变化和阴影影响的情况下能完整、准确地提取出运动车辆轮廓.     

Spacebased estimation of moisture transport in marine atmosphere using support vector regression

An improved algorithm is developed based on support vector regression (SVR) to estimate horizonal water vapor transport integrated through the depth of the atmosphere (Θ) over the global ocean from observations of surface wind-stress vector by QuikSCAT, cloud drift wind vector derived from the Multi-angle Imaging SpectroRadiometer (MISR) and geostationary satellites, and precipitable water from the Special Sensor Microwave/Imager (SSM/I). The statistical relation is established between the input parameters (the surface wind stress, the 850 mb wind, the precipitable water, time and location) and the target data (Θ calculated from rawinsondes and reanalysis of numerical weather prediction model). The results are validated with independent daily rawinsonde observations, monthly mean reanalysis data, and through regional water balance. This study clearly demonstrates the improvement of Θ derived from satellite data using SVR over previous data sets based on linear regression and neural network. The SVR methodology reduces both mean bias and standard deviation compared with rawinsonde observations. It agrees better with observations from synoptic to seasonal time scales, and compare more favorably with the reanalysis data on seasonal variations. Only the SVR result can achieve the water balance over South America. The rationale of the advantage by SVR method and the impact of adding the upper level wind will also be discussed.     

Parallel and distributed simulation of sediment dynamics in shallow water using particle decomposition approach

This paper describes the parallel simulation of sediment dynamics in shallow water. By using a Lagrangian model, the problem is transformed to one in which a large number of independent particles must be tracked. This results in a technique that can be parallelised with high efficiency. We have developed a sediment transport model using three different sediment suspension methods. The first method uses a modified mean for the Poisson distribution function to determine the expected number of the suspended particles in each particular grid cell of the domain over all available processors. The second method determines the number of particles to suspend with the aid of the Poisson distribution function only in those grid cells which are assigned to that processor. The third method is based on the technique of using a synchronised pseudo-random-number generator to generate identical numbers of suspended particles in all valid grid cells for each processor. Parallel simulation experiments are performed in order to investigate the efficiency of these three methods. Also the parallel performance of the implementations is analysed. We conclude that the second method is the best method on distributed computing systems (e.g., a Beowulf cluster), whereas the third maintains the best load distribution.     

An efficient hybrid multicast transport protocol for collaborative virtual environment with networked haptic

In recent years, we have witnessed a growing interest in the synchronous collaboration based class of applications. Several techniques for collaborative virtual environments (CVE), haptic, audio and visual environments (C-HAVE) have been designed. However, several challenging issues remain to be resolved before CVE and C-HAVE become a common place. In this paper, we focus on applications that are based on closely coupled and highly synchronized haptic tasks that require a high-level of coordination among the participants. Four main protocols have been designed to resolve the synchronization issues in such environments: the synchronous collaboration transport protocol, the selective reliable transmission protocol, the reliable multicast transport protocol and the scalable reliable multicast. While these four protocols have shown good performance for CVE and C-HAVE class of applications, none of these protocols has been able to meet all of the basic CVE requirements, i.e., scalability, reliability, synchronization, and minimum delay. In this paper, we present a hybrid protocol that is able to satisfy all of the CVE and C-HAVE requirements and discuss its implementation and results in two tele-surgery applications. This work is partially supported by Grants from Canada Research Chair Program, NSERC, OIT/Ontario Distinguished Researcher Award, Early Research Award and ORNEC Research Grant.     

基于数字广播电视的TS流研究与分析

文章深刻分析了数字电视中的传送码流(TS流),TS流中包含了节目控制信息、系统信息、用户信息、网络信息等。这些信息关系到数字电视整个技术的实现,因此对TS流的深入理解是研究数字电视的基础。     

基于GML的公共交通数据建模

文章分析了目前的交通信息系统的建模方法及其存在的问题,结合GML3.1、GML模式和线性参考方法,研究了使用GML对公共交通数据模型的几何和拓扑关系建模的方法。以城市公共交通模型为开发实例,给出了基于GML的郑州市公共交通的建模方案和具体实现方法,并使用XSLT技术将最终结果可视化。     

基于最短道路的城市公交智能咨询系统的研究与实现

研究基于最短道路的城市公交智能查询系统,首先针对城市公交线路网络图建立数学模型;然后研究基于上述数学模型的数据库建立方法和相应的算法设计,和以Dijkstra算法为基础的、基于道路最短的公交线路查询算法,并通过简单模拟数据验证算法的有效性;最后简要介绍按此思想设计实现的城市公交智能查询系统.     

Modeling sediment resuspension and transport induced by storm wind in Apalachicola Bay, USA

Sediment is an important environmental factor for aquatic ecosystem and oyster productivities of Apalachicola Bay located in Florida, USA. Based on the data analysis in this study, surface wind speed is highly correlated to the turbidity of water column, which results from sediment resuspension and transport in the Apalachicola Bay. In this paper, an application of a 3D sediment transport model to predict the wind-induced sediment transport in Apalachicola Bay is described. The sediment model is coupled with a 3D hydrodynamic module in the Environmental Fluid Dynamics Code (EFDC) model that provides information on estuarine circulation and salinity transport under normal temperature conditions. The hydrodynamic model was calibrated with field observations of water levels and salinity. The sediment transport model solves the transport equation with sources and sinks terms to describe sediment deposition and resuspension. The coupled hydrodynamic and sediment transport models were used to investigate wind-induced total suspended sediments (TSS) resuspension and transport in the bay. For the period June 1–July 30, 2005 two storm events with strong winds gave model results of TSS concentrations that compared well with the field observations. Model simulations reasonably reproduce the sudden increase of sediment concentrations during the storm events. Maximum sediment concentrations in the bay during the two storm events were 10 times or more than those in the pre-storm conditions. Spatial sediment transport from model simulations indicate active sediment resuspension and transport near areas of highly productive oyster beds. The model predictions of TSS and salinity can be used as inputs to an oyster dynamic model (Wang, H., Huang, W., Harwell, M., Edmiston, L., Johnson, E., Hsieh, P., Milla, K., Christensen, J., Stewart, J., Liu, X., 2008. Modeling eastern oyster population dynamics in response to changing environment in Apalachicola Bay, Florida. Journal of Ecological Modeling 211, 77–89) to support the ecological study of oyster growth and mortality in the aquatic ecosystem of Apalachicola Bay.     

轨检仪处理水平轨缝信息的变化率滤波法

介绍了一种利用变化率滤波处理水平参数中轨缝信息的方法。由于该方法取代了原系统的数字滤波法处理水平参数中的轨缝信息,所以利用数字滤波器进行滤波对于稳态过程信号滤波能够起到最佳效果。而GJY轨检仪测得的水平参数是一个瞬态信号,因此采用了变化率滤波方法对水平轨缝信息进行处理,并在GJY-H系统中得到成功的应用,取得了良好的社会和经济效益。