网络控制系统中不同节点驱动方式的时延研究

在建立网络控制系统模型时,节点驱动方式的不同,对整个系统的实时性、稳定性以及鲁棒性等理论研究产生很大影响;通过分析网络节点在四种驱动方式下的动作时序和数学模型,用MATLAB/TrueTime仿真工具箱仿真测试了不同驱动方式在不同延时条件下所表现的特性:小时延情况下,事件驱动的网络控制系统性能优于时钟驱动的网络控制系统性能,而当网络负荷较重,尤其出现大时延时,采用时钟驱动的网络控制系统配合先进预估控制策略,将会得到较好的系统性能。     

嵌入式VxWorks系统下的CPCI设备驱动程序开发

具体分析了VxWorks下PCI总线的配置空间结构和地址映射,并采用CPCI9054芯片,结合一个信号产生、数据采集处理系统的工程实例,详细阐述了VxWorks下CPCI设备驱动程序的开发实现方法和具体步骤,并给出了部分关键代码.应用结果表明,该方法可移植性较高,可操作性强,对于了解和开发CPCI驱动程序具有一定的参考...     

在线会议管理系统中Cookies安全应用的研究

本文首先介绍了在线会议管理系统的体系架构,然后详细分析了该系统中存在的Cookie及其安全问题,并提出了具体的解决方案。     

Design reuse oriented partial retrieval of CAD models

As a huge number of 3D CAD models is generated each year, retrieval of 3D CAD models is becoming more and more important for achieving design reuse. However, the existing methods for partial retrieval of 3D CAD models are very few and far from the requirements of design reuse. In this paper, we present an approach to partial retrieval of 3D CAD models for design reuse. The criteria for determining whether a subpart of 3D CAD models is reusable for design is defined first. Based on the criteria defined, all the design reusable subparts involved in the 3D CAD models in the library are automatically extracted and stored in the library as reference models. Moreover, each design reusable subpart in the library is represented by all its local matching regions in a hierarchical way so as to support multi-mode partial retrieval. In our approach, three partial retrieval modes including normal retrieval, exact retrieval and relaxed retrieval are defined to meet various partial retrieval requirements of design reuse such as the incomplete and vague queries during the early design stage. And the multi-mode partial retrieval is achieved by performing multi-mode matching and similarity assessment between the query and the design reusable subparts in the library indexed by bitmap. Experimental results are presented to demonstrate the effectiveness of the approach.     

Validation of MODIS derived aerosol optical depth over the Yangtze River Delta in China

MODIS derived aerosol optical depths (AODs) at 550 nm are compared with sunphotometer CE318 measurements at 7 sites located at Yangtze River Delta (YRD) in China from July to October, 2007. The evaluation result indicates that MODIS AODs (Collection 5, C005) are in good agreement with those from CE318 in dense vegetation regions, but show more differences in those regions with complex underlying surface (such as at lake water and urban surface sites). Reasons for these differences are discussed after removing cases with significant errors caused by validation scheme. The final validation result shows that MODIS AODs are in good agreement with CE318 with a correlation coefficient of 0.85 and RMS of 0.15. 90% of MODIS cases fall in the range of Δτ = ± 0.05 ± 0.20τ, indicating MODIS aerosol retrieval algorithm, aerosol models and surface reflectance estimate are generally suitably reasonable for aerosol retrieval in YRD. However, MODIS AODs show a systemic errors with fitted line of y = 0.75x + 0.13, indicating underestimation of AOD when aerosol loadings are high. Aerosol models and surface reflectance estimations are dominant sources of MODIS aerosol retrieval errors.     

基于FPGA的CAN总线控制器SJA1000软核的设计

分析了CAN控制器SJA1000的特点及CAN协议通信格式.设计了控制器SJA1000的IP软核,能为应用提供一个性能优良的、易于移植的控制器SJA1000,实现了对步进电机的控制.     

网络内部地址隐藏技术与实现

为了提高系统的安全,提出基于静态NAT技术保护内部网络地址不被发现,使内网与外网络隔离。本文实现了NAT技术,并进行了时延和信息速率测试试验,试验结果表明:满足系统需求,提供一定的网络安全保障,提高了系统的安全性。     

Efficient edit propagation using hierarchical data structure

This paper presents a novel unified hierarchical structure for scalable edit propagation. Our method is based on the key observation that in edit propagation, appearance varies very smoothly in those regions where the appearance is different from the user-specified pixels. Uniformly sampling in these regions leads to redundant computation. We propose to use a quadtree-based adaptive subdivision method such that more samples are selected in similar regions and less in those that are different from the user-specified regions. As a result, both the computation and the memory requirement are significantly reduced. In edit propagation, an edge-preserving propagation function is first built, and the full solution for all the pixels can be computed by interpolating from the solution obtained from the adaptively subdivided domain. Furthermore, our approach can be easily extended to accelerate video edit propagation using an adaptive octree structure. In order to improve user interaction, we introduce several new Gaussian Mixture Model (GMM) brushes to find pixels that are similar to the user-specified regions. Compared with previous methods, our approach requires significantly less time and memory, while achieving visually same results. Experimental results demonstrate the efficiency and effectiveness of our approach on high-resolution photographs and videos.     

Computational investigation of interactions between human H2 receptor and its agonists

Type 2 histamine receptor (H(2)R) is widely distributed in the body. Its main function is modulating the secretion of gastric acid. Most gastric acid-related diseases are closely associated with it. In this study, a combination of pharmacophore modeling, homology modeling, molecular docking and molecular dynamics methods were performed on human H(2)R and its agonists to investigate interaction details between them. At first, a pharmacophore model of H(2)R agonists was developed, which was then validated by QSAR and database searching. Afterwards, a model of the H(2)R was built utilizing homology modeling method. Then, a reference agonist was docked into the receptor model by induced fit docking. The 'induced' model can dramatically improve the recovery ratio from 46.8% to 69.5% among top 10% of the ranked database in the simulated virtual screening. The pharmocophore model and the receptor model matched very well each other, which provided valuable information for future studies. Asp98, Asp186 and Tyr190 played key roles in the binding of H(2)R agonists, and direct interactions were observed between the three residues and agonists. Residue Tyr250 could also form a hydrogen bond with H(2)R agonists. These findings would be very useful for the discovery of novel and potent H(2)R agonists.