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1.
对动态数据流的在线学习问题,传统的在线BLS(Broad Learning System)算法无法准确地捕捉数据最新的变化趋势。为此提出两种具有遗忘机制的在线BLS算法——基于遗忘因子的在线BLS算法(FF-OBLS:Online Broad Learning System based on Forgetting Factor)和基于滑动窗口的在线BLS算法(SW-OBLS:Online Broad Learning System based on Sliding Window)。FF-OBLS在在线学习过程中通过为旧样本添加遗忘因子以体现新旧样本对学习模型的不同贡献,SW-OBLS在在线学习过程中通过删除旧样本以消除旧样本对学习模型的影响,从而使学习模型对动态数据流的后续趋势做出更准确的分析和预测。为验证提出的两种在线BLS算法的有效性,使用动态回归数据集进行实验。实验结果表明,具有遗忘机制的在线BLS模型在预测精度和时间开销上均优于传统在线BLS模型,更适合处理动态数据流问题。  相似文献   

2.
数据流分为静态数据流和动态数据流,但因数据的情况越来越复杂,动态数据流已经遍布我们的生活.针对动态数据流中的不平衡数据流、概念漂移数据流及噪声数据流的基本概念、算法特点、相关工作及优缺点等方面进行了分析和阐述,同时对三类动态数据流的传输特点、适用方法及集成分类算法展开了介绍与对比,并对突变、增量、重复及渐变的概念漂移类型展开了研究,以及集成分类中常用的Boosting和Bagging方法进行了深度研究,指出了现阶段动态数据流集成分类算法所需要解决的主要问题,此外,针对多种类概念漂移、复合动态数据流及集成基分类器的动态加权等提供了多个可扩展性研究方向,并进行了分析和展望.  相似文献   

3.
基于残差思想的异常数据检测方法的关键之处在于对数据的准确预测.针对这一问题,提出基于改进径向基网络(radial basis function network,RBFN)的过程工业时间序列预测方法,该方法通过改变RBF网络的输入形式,使改进后的RBF网络能够更方便地引入遗忘因子以及惩罚因子,以适应于基于残差思想的异常数据检测方法要求的动态性能和鲁棒性.通过理论证明改进的RBF网络与传统RBF网络的等效性,并通过实验比较证明改进后的RBF网络较传统的网络结构更简单,参数意义更明确.  相似文献   

4.
文本标签作为一种文本关键词,能够简化科技政策中有效信息的挖掘。本文从科技政策类别角度,将标签类别分为科技投入、知识产权、农村科技和税收四类,针对传统SVM算法的缺点和标签数据不平衡的缺点,结合欧式距离思想,提出一种带有惩罚因子的ESVM科技政策文本标签分类方法。最后,对比SVM和ESVM两种分类方法,验证了本文方法在处理科技政策文本标签数据上的有效性。  相似文献   

5.
针对数据流环境中混合多种类型概念漂移问题,提出了基于图模型的数据流分类算法.该算法通过对数据块上的实例集进行概念表示,检测概念的变化度来衡量概念漂移,并引入了一个动态自适应阈值,为每个待分类实例合理选择基分类器模型,充分利用基分类器模型潜在的多样性并降低漂移恢复期间的分类误差.实验表明,本文提出的算法性能在多数数据集上优于其他算法,在复杂概念漂移环境下具有较好的适应性.  相似文献   

6.
针对海量数据环境下对数据流预处理实时性和高效性的需求,文中提出了一种大规模数据环境下的数据流实时预处理模型,基于MMHC(Max-Min Hill-Climbing)并运用增量式学习的方式改进贝叶斯网络模型的构建过程,提升预处理模型的有效性,同时也减少了因模型更新所消耗的时间,在一定程度上防止了数据的积压,支持网络结构的动态更新,适用于更复杂的数据环境.  相似文献   

7.
为了发现分布式数据流环境下的微簇,针对数据流的遗忘特性,提出一种基于时间衰减的数据流聚类算法.根据衰减模型增量式的处理局部站点,将局部模型发送给中心站点.中心站点对局部站点的微簇进行合并,生成全局聚类模型.通过真实数据和仿真数据的实验表明,该算法能够得到较好的聚类质量,并且有较好的伸缩性.  相似文献   

8.
隐含概念漂移的数据流分类问题是数据挖掘领域研究的热点之一,而实际数据中的噪音会直接影响概念漂移检测及分类质量,因此具有良好抗噪性能的数据流分类方法具有重要的研究和应用价值.随机决策树的集成模型是一种有效的数据流分类模型,为此本文基于随机决策树,引入Hoeffding Bounds不等式来检测和区分概念漂移和噪音,根据检测结果动态调整滑动窗口的大小和漂移检测周期,并提出一种增量式的集成分类方法ICDC,实验结果表明,本文算法在含噪音数据流上处理概念漂移是有效的.  相似文献   

9.
数据流的特征是海量的、高速流动的、实时处理的.由于一些数据分布随着时间而改变,因此将这些数据流称为概念漂移.首先按照分类模型对数据流决策树进行分类,分为单分类决策树和集成分类决策树.单分类模型分为快速决策树、变异决策树和其他决策树算法.集成分类模型分为衍生快速决策树和随机决策树变体算法.其次介绍了概念漂移处理技术,包括概念漂移问题的描述、常见的概念漂移处理技术和用于解决概念漂移的决策树算法.接着介绍了增量模型决策树算法,最后对本文介绍的决策树算法进行分析总结.  相似文献   

10.
数据流广泛应用于现实世界的多个领域,但是不平衡数据流的存在严重影响了传统数据流分类器的性能.针对不平衡数据流问题,提出了随机平衡采样算法(RBS)处理数据流的不平衡问题,并以RBS算法为基础提出了随机平衡采样数据流集成算法(RBSSEA)旨在解决不平衡数据流的分类问题.最后,分别采用合成和真实数据集对RBSSEA算法进行验证,实验结果证明RBSSEA算法在解决不平衡数据流分类问题具有一定的优势.  相似文献   

11.
Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.  相似文献   

12.
何延凌 《科技信息》2008,(4):258-258
Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women's language from these perspectives: pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women's language, more attention should be paid to language use in social context. What's more, the linguistic phenomena in a speaking community can be understood more thoroughly.  相似文献   

13.
王慧 《科技信息》2008,(10):240-240
Wuthering Heights, Emily Bronte's only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.  相似文献   

14.
The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.  相似文献   

15.
理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。  相似文献   

16.
As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.  相似文献   

17.
正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-  相似文献   

18.
We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-  相似文献   

19.
正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that  相似文献   

20.
For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the  相似文献   

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