基于抽样学习的关联挖掘算法设计

将抽样技术引入关联规则挖掘以提高算法的执行效率是进行有效挖掘的捷径,但几乎所有关于该方法的研究都无法避免在抽样的过程中重复执行关联分析,这可能会使抽样过程产生的开销大于其为挖掘带来的益处.为了克服这一传统做法所带来的弊端,引入了二元分类评估的混淆矩阵,以解决随机抽样引起的样本1-项集频繁性变动问题.在未对抽样过程执行关联分析的前提下,设计了一个新公式以刻画累进抽样的学习曲线,并由学习曲线快速找到代替总体进行关联挖掘的最优样本.通过对该抽样方法的有效性和可靠性进行评估,以及其在人口普查数据中的实现,证明了该方法提高关联规则挖掘效率的效果明显.     

可靠度分析中拉丁超立方和传统舍选抽样法对比研究

蒙特卡罗方法是计算工程可靠度的重要手段,其计算精度需要大量的样本数量,相应的计算量巨大.在蒙特卡罗方法中,采用拉丁超立方(LHS)法和传统舍选法两类抽样方法,计算了条形基础极限承载力的失效概率,对比分析两种抽样方法的差异.计算结果表明,拉丁超立方体抽样法得到失效概率需要样本数量约为舍选法数量的25％.通过增加样本数量拉...     

采煤机截割部扭矩轴的动态可靠性分析

考虑结构和材料等随机参数对零件动态可靠性的影响,避免轴系产生共振,利用Workbench软件建立扭矩轴参数化有限元模型.用模态分析法求解前六阶固有频率和临界转速,并与传递矩阵法比较,证明了结构和转速设计的合理性.结合谐响应分析,说明共振失效应考虑一阶固有频率.通过响应面设计和拉丁超立方抽样法完成对扭矩轴结构、材料参数的抽样,运用BP神经网络拟合一阶固有频率的功能函数,并求解随机参数的可靠性灵敏度.采用一次二阶矩法(FOSM)计算轴在特定转速下的可靠度,并用Monte-Carlo模拟法(MCS)进行了验证,说明转速设计较为可靠.通过灵敏度分析,明确了对扭矩轴动态可靠性影响最大的因素,为轴的稳健优化设计奠定基础.     

基于重要抽样法的模糊可靠性数字仿真

文章利用重要抽样法,通过对模糊变量的当量随机变量的抽样,用数字仿真的方法估计零件的可靠性.在把模糊变量转化成当量随机变量后,根据当量随机变量的信息利用遗传算法计算设计点,并构造重要抽样密度函数,然后通过对当量随机变量重新抽样来计算零件的失效概率.用算例比较了重要抽样法和蒙特卡罗法的计算结果,验证了用重要抽样法对模糊变量进行抽样的可行性和效率.     

随机参数结构体系的随机地震响应计算方法

基于虚拟激励法和摄动随机有限元法,推导了单自由度体系复合随机动力响应问题的计算方法,并在灵敏度分 析中有效地消除了长期项的影响.算例表明,该法数值分析结果与Monte-Carlo随机模拟结果比较,具有理想的精度.     

类型中心抽样调查体系的研究

<正>前言 类型中心抽样调查法是当前我国森林资源调查的一种新型方法。它是建立在森林资源概知的基础上,可以根据小班档案或遥感信息资料,分别小班类型,依概知平均数抽取极少的样本单元就能获得一定精度的总体标志值。 类型中心抽样较客观地吸取了典型调查和随机抽样的优点。它将我国传统的典型调查与随机抽样结合起来,把典型调查与统计分析融为一体,使典型调查建立起精度分析系统,有了进行比较分析的可能。这样可以提高典型调查的应用价值,发挥典型调查快速、省工的优势,大大减少了调查人员的外业工作量。因此,有必要在原有的基础上对类型中心抽样在理论上和应用方面进一步研究。 本次实验的特点主要是将3p抽样法(Probability Proportional to Prediction)和众数抽样法引入类型中心抽样中来,使它进一步发挥高效率的作用,把类型中心抽样组成一种调查体系。 本次试验的目的:1.在被抽中的小班内,采用角规点抽样、角规线抽样和常规带状样地组成三套样本,通过比较,选择最优样本单元;2.把3p抽样引进类型中心抽样体系,利用3p样本估测总体蓄积量、生长量(率)和出材量(率),以消除应用数表和调查总体的不一致性而引起的误差。     

一种改进的SMOTE算法

少数类样本合成过抽样技术(SMOTE)是一种过抽样数据预处理算法,是在两个少数类之间随机插入一个新的少数类样本.为了解决SMOTE算法生成少数样本随机性的局限性,在考虑多数类样本分布会对少数样本的生成产生影响的基础上,提出了改进的SMOTE算法.在WEKA平台上分别使用改进前后的SMOTE算法对选用的UCI数据集进行过抽样数据预处理,并使用朴素贝叶斯、决策树和K邻近分类器对过抽样后的数据集进行分类,选择几何均数(G-mean)和曲线下面积(AUC)两个评价指标,实验显示改进后的SMOTE算法预处理的数据集的分类效果更好,证明改进后的SMOTE算法生成的少数类样本更加合理.     

基于虚位移原理的随机有限元方法研究

为研究工程对象的响应特性提供一种新的解决途径,本文根据虚位移原理得出弹性体轴对称静态问题的平衡方程以及力的边界条件下的等效积分“弱”形式,结合摄动技术推导出八节点四边形轴对称等参单元的静态随机有限元方程,提出了基于虚位移原理的随机有限元方法,最后考虑汽轮机转子的物性参数和载荷参数的随机性,利用这种方法对汽轮机转子的静态随机响应特性进行计算和分析,并与直接Monte-Carlo模拟仿真法的计算结果相对比,验证了该方法的正确性和有效性.     

基于电磁暂态仿真的电压骤降概率评估

为了准确预测电力系统中电压骤降的特性及后果,提出了基于非序贯Monte-Carlo模拟和电磁暂态仿真相结合的电力系统电压骤降的概率评估新方法和概率评估指标体系。Monte-Carlo法的优点在于能反映电力系统的随机特性,使用该方法几乎不受系统复杂性的限制。算法利用Monte-Carlo仿真得到各种故障信息,通过仿真程序PSCAD/EMTDC对Monte-Carlo模拟法随机产生的各种故障形态进行仿真计算,最后分析统计得到系统和敏感负荷点电压骤降的各项概率指标。文中以RBTS标准测试系统为例进行了分析计算,结果表明模型和算法是可行的。     

向量随机场模拟及其在岩土工程中的应用

对于岩土工程中多个土性随机参数向量随机场,将随机场谱表示模拟方法与Monte-Carlo法相结合,得到了考虑土性参数自相关性与互相关性的Monte-Carlo随机有限元法,并应用于堤坡失效概率的计算。计算结果表明:谱表示模拟方法比普通协方差分解方法收敛速度快,采用该模拟方法的Monte-Carlo随机有限元法是计算岩土工程可靠度的有效方法;在土性参数随机场的模拟中应考虑参数间的互相关性对于岩土工程可靠度的显著影响。     

Markedness and its Interpretation in Language Use

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.     

Features of Women's language

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.     

低渗透非均质砂岩油藏启动压力梯度研究

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。     

On Tragic Consciousness In The Works By Ernest Hemingway

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.     

Achieving Unusual States of Matter Under High Pressure

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-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

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-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

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     

Call for Papers

<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with     

Journal of Donghua University ( English Edition) Contents of Volume 31

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Brief Introduction to “Journal of Jilin University( Science Edition) ”

<正>"Journal of Jilin University(Science Edition)"is a comprehensive academic journal in the fields of science sponsored by Jilin University and administrated by the Ministry of Education of the Peoples Republic of China.The journal started publication in 1955.The original name at starting publication was"Journal of Natural Science of Northeast People University",which was changed into"Acta Scientiarum Naturalium Universitatis Jilinensis"in 1958 owing to the name change of the university.The present journal name has