基于模糊自适应PID的桥式起重机智能防摆控制研究     

胡艳丽  刘团结  贾群  沈晓波 《淮南师范学院学报》2012,14(3):17-20

为了消除桥式起重机吊重摆动和实现小车精确定位,提高起重机工作效率,国内外很多学者对防摆控制方法做了大量研究。在建立起重机非线性数学模型的基础上,完成基于模糊自适应PID防摆控制器的设计,其中角度环采用模糊控制器,位置环采用模糊PID控制器。通过与线性二次型最优控制（LQR）仿真结果比较,表明该方法的可行性,其控制过程更加平稳,稳态精度更高,并且当吊重质量和绳长发生改变时,系统仍有较强的鲁棒性。  相似文献   

The Effects of Type I Error Rate and Power of the ANCOVA F Test and Selected Alternatives Under Nonnormality and Variance Heterogeneity     

David C. Rheinheimer  Douglas A. Penfield 《Journal of Experimental Education》2013,81(4):373-391

The authors sought to identify through Monte Carlo simulations those conditions for which analysis of covariance (ANCOVA) does not maintain adequate Type I error rates and power. The conditions that were manipulated included assumptions of normality and variance homogeneity, sample size, number of treatment groups, and strength of the covariate-dependent variable relationship. Alternative tests studied were Quade's procedure, Puri and Sen's solution, Burnett and Barr's rank difference scores, Conover and Iman's rank transformation test, Hettmansperger's procedure, and the Puri-Sen-Harwell-Serlin test. For balanced designs, the ANCOVA F test was robust and was often the most powerful test through all sample-size designs and distributional configurations. With unbalanced designs, with variance heterogeneity, and when the largest treatment-group variance was matched with the largest group sample size, the nonparametric alternatives generally outperformed the ANCOVA test. When sample size and variance ratio were inversely coupled, all tests became very liberal; no test maintained adequate control over Type I error.  相似文献   

Data-Division–Specific Robustness and Power of Randomization Tests for ABAB Designs     

Rumen Manolov  Antonio Solanas  Isis Bulté  Patrick Onghena 《Journal of Experimental Education》2013,81(2):191-214

This study deals with the statistical properties of a randomization test applied to an ABAB design in cases where the desirable random assignment of the points of change in phase is not possible. To obtain information about each possible data division, the authors carried out a conditional Monte Carlo simulation with 100,000 samples for each systematically chosen triplet. The authors studied robustness and power under several experimental conditions—different autocorrelation levels and different effect sizes as well as different phase lengths determined by the points of change. Type I error rates were distorted by the presence of autocorrelation for the majority of data divisions. The authors obtained satisfactory Type II error rates only for large treatment effects. The relation between the lengths of the four phases appeared to be an important factor for the robustness and power of the randomization test.  相似文献   

A Study of Sensori-Motor and Conceptual Thinking in Children between the Ages of Nine and Eighteen     

Herman N. Stuart 《Journal of Experimental Education》2013,81(2):147-153

In this research, the author addresses whether the application of unidimensional item response models provides valid interpretation of test results when administering items sensitive to multiple latent dimensions. Overall, the present study found that unidimensional models are quite robust to the violation of the unidimensionality assumption due to secondary dimensions from sensitive items. When secondary dimensions are highly correlated with main construct, unidimensional models generally fit and the accuracy of ability estimation is comparable to that of strictly unidimensional tests. In addition, longer tests are more robust to the violation of the essential unidimensionality assumption than shorter ones. The author also shows that unidimensional item response theory models estimate item difficulty parameter better than item discrimination parameter in tests with secondary dimensions.  相似文献   

PISA and policy-borrowing: A philosophical perspective on their interplay in mathematics education     

Ian Cantley 《Educational Philosophy and Theory》2013,45(12):1200-1215

Mathematics achievement in different education systems around the world is assessed periodically in the Programme for International Student Assessment (PISA). PISA is deemed to yield robust international comparisons of mathematical attainment that enable individual countries and regions to monitor the performance of their education systems relative to standards being achieved internationally, with a view to informing their mathematics education policy decisions. Initially, the role of PISA in instigating mathematics education policy borrowing is outlined using England as a case study, and some existing technical critiques of PISA are then reviewed. Following this, aspects of Ludwig Wittgenstein’s later philosophy of mind are used to reason that an over-reliance on the use of PISA to inform policy decisions in mathematics education may be problematic. It is suggested that, when PISA is viewed through a later Wittgensteinian lens, a potential deficiency in the underpinning psychometric model, pertaining to the inherent indeterminism in unmeasured mathematical abilities, may weaken PISA’s utility in guiding mathematics education policy decisions. It is concluded that, whilst PISA mathematics scores may give some indication of the mathematical proficiency of a nation’s students, caution is required before mathematics education policies are borrowed from other jurisdictions on the basis of PISA performance. Implications for the other PISA domains are also outlined.  相似文献   

实时校正模型的抗差递推算法     

赵超  洪华生  张珞平 《中国科学院研究生院学报》2008,25(5):665-670

利用遥测系统实时监测水情资料,由于遥测系统自身的原因以及水文要素测量的具体要求,数据常常携带异常误差。采用有异常误差的实测流量资料对实时校正模型进行参数辨识,要求算法既能抵御异常误差的影响,又具有较强的实时跟踪能力,以适应实时洪水预报的要求。在递推最小二乘算法的基础上,引入抗差理论,削弱异常值对参数估计的影响;引入遗忘因子,实时跟踪模型时变参数的变化。计算实例表明,带有遗忘因子的抗差递推最小二乘算法对异常误差不敏感,又具有较强的实时跟踪能力。  相似文献   

数字作品的保护神——数字水印技术   总被引：1，自引：0，他引：1  

杨俊华 《石家庄学院学报》2000,(4)

作为信息隐藏技术的一个分支 ,数字水印技术在现代数字媒体的版权保护、电子票据防伪、信息隐藏标识等领域发挥着重要作用。因此 ,数字水印在数据安全中占有不可替代的地位  相似文献   

pH值的神经网络多步预测控制算法   总被引：6，自引：0，他引：6  

贾平  麻红昭  俞蒙槐 《科技通报》2000,16(1):31-36

ｐＨ值控制过程是一个具有较强非线性、纯滞后的过程,针对ｐＨ值控制系统提出了一种基于神经网络的多步预测控制算法（ＮＭＰＣ）。神经网络用于辨识对象的预测模型,控制算法利用了神经网络的梯度信息。控制效果表明该控制系统具有较好的动态性能和较强的鲁棒性。  相似文献   

基于高维特征的图像对抗攻击算法     

林大权  范睿  张良峰 《中国科学院大学学报》2022,39(3):421-431

为了攻击最先进的对抗防御方法,提出一种基于高维特征的图像对抗攻击算法——FB-PGD(feature based projected gradient descent)。该算法通过迭代的方式给待攻击图像添加扰动,使待攻击图像的特征与目标图像的特征相似,从而生成对抗样本。实验部分,在多种数据集和防御模型上,与现存的攻击算法对比,证实了FB-PGD算法不仅在以往的防御方法上攻击性能优异,同时在最先进的两个防御方法上,攻击成功率较常见的攻击方法提升超过20 % 。因此,FB-PGD算法可以成为检验防御方法的新基准。  相似文献   

基于小波包分解的数字图像水印算法研究     

韩忠 《科技通报》2012,28(4):136-137

通过Shannon熵算法采用自下向上的搜索方法选取最优小波包基,分别对原始图像和水印图像进行小波包分解,把水印数据嵌入选定的原始图像小波包基中。经攻击实验表明,应用本算法所实现的水印不可见,较好地保持了图像的质量,同时显示了较强的鲁棒性。  相似文献