局域网环境下利用DHCP欺骗技术实现DNS劫持攻击

利用DHCP协议的缺陷,实现对局域网计算机的DNS劫持攻击,并给出将此类攻击应用于网站钓鱼的实现方法,旨在引起人们对局域网安全问题的重视。     

基于存储区域网络的数据备份技术研究

从数据备份系统结构的角度,研究了传统数据备份技术的优缺点,针对现有备份技术的存在的问题,通过在存储区域网络中引入网络数据管理协议,使得存储区域网络环境下的数据备份极大减轻了网络负载量,同时业务服务器最大限度地从数据备份过程中解脱出来,从而提高了整个备份系统的性能;同时对基于存储区域网络数据备份技术研究的特点、存在的问题、研究热点和应用情况等进行了分析。     

利用CPU时间戳实现局域网时间同步的新机制

当前在网络应用中,经常需要多台计算机协同工作,因而要有一个统一时钟。提出一种利用CPU内部高精度时间戳实现局域网时钟同步的新机制,并用VC++语言编写了服务端与客户端软件,且在Windows XP 和Windows 2000环境的小型局域网进行测试。结果表明,该算法同步精度较高,且系统运行稳定。     

基于全电子设计方案的区域计算机联锁系统

介绍了基于全电子设计方案的区域性计算机联锁控制系统的技术方案和系统构成。详细阐述了系统中主控站和被控站设备的组成、功能和特点,给出了系统详细的结构框图。系统对于降低工程造价、充分发挥计算机性能、提高运输组织效率具有重要作用。     

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.     

Responses of the reflectance indices PRI and NDVI to experimental warming and drought in European shrublands along a north-south climatic gradient

The aim of this study was to evaluate the use of ground-based canopy reflectance measurements to detect changes in physiology and structure of vegetation in response to experimental warming and drought treatment at six European shrublands located along a North-South climatic gradient. We measured canopy reflectance, effective green leaf area index (green LAIe) and chlorophyll fluorescence of dominant species. The treatment effects on green LAIe varied among sites. We calculated three reflectance indices: photochemical reflectance index PRI [531 nm; 570 nm], normalized difference vegetation index NDVI₆₈₀ [780 nm; 680 nm] using red spectral region, and NDVI₅₇₀ [780 nm; 570 nm] using the same green spectral region as PRI. All three reflectance indices were significantly related to green LAIe and were able to detect changes in shrubland vegetation among treatments. In general warming treatment increased PRI and drought treatment reduced NDVI values. The significant treatment effect on photochemical efficiency of plants detected with PRI could not be detected by fluorescence measurements. However, we found canopy level measured PRI to be very sensitive to soil reflectance properties especially in vegetation areas with low green LAIe. As both soil reflectance and LAI varied between northern and southern sites it is problematic to draw universal conclusions of climate-derived changes in all vegetation types based merely on PRI measurements. We propose that canopy level PRI measurements can be more useful in areas of dense vegetation and dark soils.     

大视觉智能巡线车控制系统开发

针对常规的智能车传感器固定,视觉范围小,影响智能车的运行速度和准确性问题,提出了基于双舵机的大视觉智能巡线车控制系统。采用激光传感器、将路径识别传感器安装在车架上随动舵机的轮盘上,MCU通过控制随动摆头舵机来带动传感器的运动,使智能车的路径识别角度范围增大。经试验证明,此控制系统紧密结合双舵机的特点,充分发挥装在车架上的随动舵机带动路径识别传感器的优势,增大了智能车巡线过程中能识别到的路径范围,使智能车模实现高速稳定行驶。在不"丢线"的情况下,速度得到较大的提升,能适应各种赛道。     

3G用户在WLANs间的快速认证方法

EAP-AKA协议可以实现用户和3G网络的双向认证,但缺乏对无线局域网(WLAN)接入网络的认证和用户主密钥的更新机制,并且3G用户在WLAN间漫游时代价较高。针对上述问题,利用身份加密技术和门票技术改进EAP-AKA协议,设计无需3G网络参与的WLAN间快速漫游协议,实现对WLAN接入网络的认证和主密钥更新。     

FRA:基于帧长和发送速率的信道竞争算法

提出一种MAC层竞争信道的FRA算法。FRA算法以实验测得的数据帧长和信道速率作为调节CWmin的因子,提高了发送大数据帧或高速信道节点的信道占用时间。实验结果表明,该算法在速率、帧长各异的无线网络环境中,网络总吞吐率比DCF协议提高约70%。