环境一号B星热红外波段单通道算法温度反演

文中在考虑环境一号B星(HJ-1B)热红外波段(infrared scanner,IRS4)光谱响应函数和有效波长的基础上,通过MODTRAN4模型模拟,对Jimenez-Munoz和Sobrino(JM&S)单通道算法中的大气函数进行改进,重新计算得到了适合HJ-1B星IRS4地表温度(land surface temperature,LST)反演的3个大气函数公式,并反演了福州地区的地表温度.采用基于星上辐亮度法对反演的地表温度进行精度评价,并将反演的地表温度与JM&S算法、段四波等修正的JM&S算法反演的地表温度进行对比分析.结果表明:使用文中改进后的大气参数对HJ-1B星IRS4进行地表温度反演,可取得较好结果.     

电信网络运维阶段风险评估方法研究

安全风险评估是电信网运维阶段安全防护的重要内容,为了深入了解全网的安全状态、控制运行过程中的安全风险,需要建立一套有效的风险评估方法。本文对电信网运维阶段风险评估方法进行研究,提出了一套量化的风险计算方法。该方法不仅可以定量分析网络存在的内在脆弱性和面临的外部威胁,而且可对风险高低情况进行梳理,找出网络运行中的薄弱点,提出安全需求,从而为实施合适的安全防范措施、制定有效的风险控制策略提供理论基础。     

Efficient random saliency map detection

Most image retargeting algorithms rely heavily on valid saliency map detection to proceed. However, the inefficiency of high quality saliency map detection severely restricts the application of these image retargeting methods. In this paper, we propose a random algorithm for efficient context-aware saliency map detection. Our method is a multiple level saliency map detection algorithm that integrates multiple level coarse saliency maps into the resulting saliency map and selectively updates unreliable regio...     

Implementation and evaluation of parallel FFT on Engineering and Scientific Computation Accelerator (ESCA) architecture

The fast Fourier transform (FFT) is a fundamental kernel of many computation-intensive scientific applications.This paper deals with an implementation of the FFT on the accelerator system,a heterogeneous multi-core architecture to accelerate computation-intensive parallel computing in scientific and engineering applications.The Engineering and Scientific Computation Accelerator (ESCA) consists of a control unit and a single instruction multiple data (SIMD) processing element (PE) array,in which PEs communicate with each other via a hierarchical two-level network-on-chip (NoC) with high bandwidth and low latency.We exploit the architecture features of ESCA to implement a parallel FFT algorithm efficiently.Experimental results show that both the proposed parallel FFT algorithm and the ESCA architecture are scalable.The 16-bit fixed-point parallel FFT performance of ESCA is compared with a published work to prove the superiority of the mapping algorithm and the hardware architecture.The floating-point parallel FFT performances of ESCA are evaluated and compared with those of the IBM Cell processor and GPU to demonstrate the computing power of the ESCA system for high performance applications.     

Forced consensus in networks of double integrator systems with delayed input

This communique presents forced second-order consensus protocols with communication time-delays for the network of agents with double integrator dynamics and gives a measure of the robustness of the protocols to the communication time-delays. By employing a frequency domain method, it is proven that the forced consensus is achieved asymptotically for appropriate time-delay if the network is connected. Particularly, the maximum fixed time-delay that can be tolerated by the network is found. The forced consensus protocols are distributed in the sense that each agent only needs information from its neighboring agents, which reduces the complexity of connections between agents significantly. Numerical simulation results are provided to demonstrate the effectiveness and the sharpness of the theoretical results.     

Modeling MODIS LAI time series using three statistical methods

Leaf Area Index (LAI) is one of the most important variables characterizing land surface vegetation and dynamics. Many satellite data, such as the Moderate Resolution Imaging Spectroradiometer (MODIS), have been used to generate LAI products. It is important to characterize their spatial and temporal variations by developing mathematical models from these products. In this study, we aim to model MODIS LAI time series and further predict its future values by decomposing the LAI time series of each pixel into several components: trend, intra-annual variations, seasonal cycle, and stochastic stationary or irregular parts. Three such models that can characterize the non-stationary time series data and predict the future values are explored, including Dynamic Harmonics Regression (DHR), STL (Seasonal-Trend Decomposition Procedure based on Loess), and Seasonal ARIMA (AutoRegressive Intergrated Moving Average) (SARIMA). The preliminary results using six years (2001-2006) of the MODIS LAI product indicate that all these methods are effective to model LAI time series and predict 2007 LAI values reasonably well. The SARIMA model gives the best prediction, DHR produces the smoothest curve, and STL is more sensitive to noise in the data. These methods work best for land cover types with pronounced seasonal variations.     

Web测试与链路瓶颈分析系统设计与实现

Internet用户的日益增加,给Web服务器和网络带来了巨大的压力。了解Web站点以及网络性能状态已是网管员们非常关注的问题。要发现并解决这些问题主要是采用网页抽取与网络测量技术。在比较分析了Web特征信息及各种网络测量工具优缺点的基础上,设计并实现了一个用于Web测试与网络瓶颈分析的系统,从而为网管员们分析网站和网络故障提供了有效的参考信息。     

浅谈黑客技术及其对策

本文通过对黑客起源及其文化的认识来分析黑客技术的发展,同时也针对当前一些主要的黑客攻击手段提出了防御的对策。     

Role-based access to facilities lifecycle information on RFID tags

Radio Frequency Identification (RFID) based systems have been used in different applications in the Architecture, Engineering, Construction, Owner and Operator (AECOO) industry. Applications are mainly designed for specific lifecycle stage of the facility and serve the needs of only one of the stakeholders. This would increase the cost and the labor for adding and removing tags and eliminate the chance of using shared resources. In this paper, the usage of tags permanently attached to components is proposed where the memory of the tags is used during the lifecycle by different stakeholders for data storage and handover. A Building Information Model (BIM) database is used for tackling the interoperability issues allowing different users to access and share the data. To securely and efficiently store data on RFID tags in ifcXML format, multi-level encryption together with role-based access control is applied on the data stored on RFID tags. Each user is assigned a certain role and can only access the part of data for which he has authorization according to a predefined role and the Access Control Policy. To explore the technical feasibility of the proposed approach, a case study considering both facilities management and emergency management has been implemented and tested at Concordia University.