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991.
旨在预测风险系数,我们对沪市10个行业的β系数的时变行为采用随机游走(RW)模型,在随机游走模型的回归变量前引进了未知参数,仿真预测的结果表明,引进未知系数后的模型,其绝对预测误差MAE和均方预测误差MSE都比引进未知系数前的模型更精确,改后的模型更适合描述沪市行业风险系数的时变行为。仿真过程是通过卡尔曼滤波的递推过程获取新息及其协方差阵,得到似然函数,从而推进参数估计。将估计的结果返回卡尔曼滤波更新过程,易得观测变量的预测值。 相似文献
992.
本文根据单片机原理与接口理论和实验教学的经验与研究,分析了目前这门课程实验教学的特点和存在的问题,提出将EDA仿真技术应用于实验教学的先进教学方法,可以大大提高学习积极性和总体能力。 相似文献
993.
网络机房承载着网络系统信息交换和存储业务,为网络上的用户提供全面的数据资源共享服务和各种网络服务,那么具有良好供电能力的UPS电源则是基本保障的前提。本文从UPS电源的初步认识入手,重点讨论了UPS电源在网络机房的使用注意事项及其日常维护。 相似文献
994.
In this paper, we propose a distributed agent model that applies belief-desire-intention (BDI) reasoning and negotiation for addressing the linear assignment problem (LAP) collaboratively. In resource allocation, LAP is viewed as seeking a concurrent allocation of one different resource for every task to optimize a linear sum objective function. The proposed model provides a basic agent-based foundation needed for efficient resource allocation in a distributed environment. A distributed agent algorithm that has been developed based on the BDI negotiation model is examined both analytically and experimentally. To improve performance in terms of average negotiation speed and solution quality, two initialization heuristics and two different reasoning control strategies are applied, with the latter yielding different variants of the basic algorithm. Extensive simulations suggest that all the heuristic-algorithm combinations can produce a near optimal solution soon enough in some specific sense. The significance and applicability of the research work are also discussed. 相似文献
995.
An application of MODIS data to snow cover monitoring in a pastoral area: A case study in Northern Xinjiang, China 总被引:3,自引:0,他引:3
Tian Gang Liang Xing Yuan Liu Wen Long Li Zheng Gang Guo Ji Zhou Ren 《Remote sensing of environment》2008,112(4):1514-1526
Snow is an important land cover on the earth's surface. It is characterized by its changing nature. Monitoring snow cover extent plays a significant role in dynamic studies and prevention of snow-caused disasters in pastoral areas. Using NASA EOS Terra/MODIS snow cover products and in situ observation data during the four snow seasons from November 1 to March 31 of year 2001 to 2005 in northern Xinjiang area, the accuracy of MODIS snow cover mapping algorithm under varied snow depth and land cover types was analyzed. The overall accuracy of MODIS daily snow cover mapping algorithm in clear sky condition is high at 98.5%; snow agreement reaches 98.2%, and ranges from 77.8% to 100% over the 4-year period for individual sites. Snow depth (SD) is one of the major factors affecting the accuracy of MODIS snow cover maps. MODIS does not identify any snow for SD less than 0.5 cm. The overall accuracy increases with snow depth if SD is equal to or greater than 3 cm, and decreases for SD below 3 cm. Land cover has an important influence in the accuracy of MODIS snow cover maps. The use of MOD10A1 snow cover products is severely affected by cloud cover. The 8-day composite products of MOD10A2 can effectively minimize the effect of cloud cover in most cases. Cloud cover in excess of 10% occurs on 99% of the MOD10A1 products and 14.7% of the MOD10A2 products analyzed during the four snow seasons. User-defined multiple day composite images based on MOD10A1, with flexibilities of selecting composite period, starting and ending date and composite sequence of MOD10A1 products, have an advantage in effectively monitoring snow cover extent for regional snow-caused disasters in pastoral areas. 相似文献
996.
Yu J Amores J Sebe N Radeva P Tian Q 《IEEE transactions on pattern analysis and machine intelligence》2008,30(3):451-462
In this paper, we present a general guideline to find a better distance measure for similarity estimation based on statistical analysis of distribution models and distance functions. A new set of distance measures are derived from the harmonic distance, the geometric distance, and their generalized variants according to the Maximum Likelihood theory. These measures can provide a more accurate feature model than the classical Euclidean and Manhattan distances. We also find that the feature elements are often from heterogeneous sources that may have different influence on similarity estimation. Therefore, the assumption of single isotropic distribution model is often inappropriate. To alleviate this problem, we use a boosted distance measure framework that finds multiple distance measures which fit the distribution of selected feature elements best for accurate similarity estimation. The new distance measures for similarity estimation are tested on two applications: stereo matching and motion tracking in video sequences. The performance of boosted distance measure is further evaluated on several benchmark data sets from the UCI repository and two image retrieval applications. In all the experiments, robust results are obtained based on the proposed methods. 相似文献
997.
998.
999.
18位高精度音频∑-△DAC设计 总被引:1,自引:0,他引:1
采用基于过采样∑-△DAC调制技术设计的音频D/A转换器,对量化噪声进行有效整形,提高了分辨率和带内信噪比(SNR).重点对Sigma-delta设计进行了详细分析,给出了有关电路结构和仿真结果.芯片已在TSMC 0.18μm CMOS工艺上流片成功,在工作频率6.144MHz时动态范围达128.6dB,信噪比109.5dB,总谐波失真达-117.2dB. 相似文献
1000.