基于神经网络的数控机床可靠性预计研究     

余香梅  舒彤 《九江师专学报》2007,26(6):40-43

本文提出了利用人工神经网络来辅助实现数控机床的可靠性预计的方法，建立了用于数控机床可靠性预测的三层BP神经网络模型，给出了具体的算法，并通过实例证明该方法比传统的数学模型预计方法更准确和可靠。  相似文献   

基于XGBoost算法的社交网络链路预测     

陈耀飞  王友国  朱亮 《教育技术导刊》2019,18(11):132-135

提升链路预测精度是复杂网路研究的基础问题之一。传统基于局部信息相似性、基于全局信息相似性与基于随机游走相似性的链路预测都是基于单个相似性指标进行预测的,而没有充分利用这些相似性指标的综合信息。将链路预测问题看作机器学习中的二分类问题,将有连接的样本标签记为1,无连接的样本标签记为0,将基于局部信息、基于全局信息与基于随机游走相似性等15个指标作为样本特征。综合考虑以上信息,使用XGBoost算法,选取AUC作为模型评价准则,在facebook真实数据集上进行实验。结果表明,该算法在测试集上的AUC高于基于单个相似性指标链路预测的AUC。  相似文献   

蠕变条件下完整岩石的起裂和扩展准则     

陈有亮  岳中琦  谭国焕  李启光 《上海大学学报(英文版)》2002,6(1):24-35

The mechanism and criterion of crack initiation and propagation of rocks were investigated by many researchers,And the creep behaviour of rocks was also theoretically and experimentally studied by some scientists and engineers.The characteristics of crack initation and propagation of rocks under creep condition.however,are very improtant for rock engineering and still not paid enough attention by researchers,In this paper,the criterion and mechanism of crack initiation and propagation under creep condition were investigated using specimens collected from sandstone rock formations outcropping in the Emei Mountain,the Sichuan Province of China.Cuboid specimens under three point bending were used in this investigation.All specimens were classified into four sorts and used for Mode-I fracutre of creep frcture tests.The experimental result shows that due to creep deformation.rock crack will inevitably initialt and propagate under a load of KI,which is less than fracture toughness KIC but not less than a constant(marked as KIC2),KIC2 indicates the ability of rock to resist crack initiation and propagation under creep conditions and is less than fracture tough ness KIC.defined as creep fracture toughness in this paper,KIC2 should be considered as an importnat parameter on design and computation of rock engineering.The microstructureal mechanism for crack initiation and propagation of rock materials under creep condition was introduced based on competitive model between softening effect and hardening effect,and the validity of test result was explained.The test result was also verified in rheological theory.When KI is more than KIC2 but less than KIC,rock crack will initiate and propagate after a time interval of sustained loading under creep condition.In order to find the relation between duration of sustained lading.which can lead to crack initiation and propagation,and the initial stress intensity factor KI,an unequal0interval time sequence forecasting and predicting model was introduced,and the relation was obtained for homogeneous and isotropic fine-grained red sandstone.Finally a modified fracture toughness formula was given,in which the influence of fracture process zone(FPZ) was fully considered.  相似文献   

改进深度置信网络在城市用水量预测中的应用     

刘春柳  张征 《教育技术导刊》2020,19(1):41-45

城市用水量的准确预测可以为供水管网智能调度、异常报警提供支持,便于及时发现漏损、排查及检修,具有极大的现实意义与经济利益。针对现有用水量预测方法忽视用水量数据自身特征及不能模拟更复杂的数学运算的问题,提出一种改进深度置信网络（DBN）的用水量预测方法。对有高斯分布的连续受限玻尔兹曼机（CRBM）引入稀疏正则项,解决特征同质化现象的同时也适用于用水量数据输入。实验结果表明,在实际用水量预测中,改进DBN模型相比传统神经网络和传统DBN预测模型,预测准确率得到了较大的提高。  相似文献   

改进的灰色模型在基础沉降预测中的应用     

喻娟  郭翠翠  周成龙 《教育技术导刊》2007,(7)

一般的灰色残差修正GM(1,1)模型只是单纯利用差分来代替微分,而且用原始沉降数据第一点的值作为时间响应函数的初始值,导致了一定的误差。提出一种多项式逼近法改进后的残差修正GM(1,1)模型,该模型利用多项式在离散观测点上的导数代替常用的差分,同时添加一个初值参数C_0做出调整。实验验证,改进模型具有较好的准确性和工程应用价值。  相似文献   

云南省产业结构现状分析及发展趋势预测   总被引：1，自引：1，他引：1  

张无畏 《楚雄师范学院学报》2002,17(5):79-82

本文通过调查我国云南省及云南省各地州建国以来产业结构的变动情况，利用三次产业分类法对云南省产业结构的发展和现状进行了分析，并对云南省未来25年产业结构的发展作出预测。  相似文献   

Generalized Nonlinear Irreducible Auto-Correlation and Its Applications in Nonlinear Prediction Models Identification     

侯越先  何丕廉 《天津大学学报(英文版)》2005,11(1):35-39

There is still an obstacle to prevent neural network from wider and more effective applications, i.e. , the lack of effective theories of models identification. Based on information theory and its generalization, this paper introduces a universal method to achieve nonlinear models identification. Two key quantities, which are called nonlinear irreducible auto-correlation (NIAC) and generalized nonlinear irreducible auto-correlation (GNIAC), are defined and discussed. NIAC and GNIAC correspond with intrinstic irreducible auto-dependency (IAD) and generalized irreducible autodependency (GLAD) of time series respectively. By investigating the evolving trend of NIAL; and GNIAC, the optimal auto-regressive order of nonlinear auto-regressive models could be determined naturally, Subsequently, an efficient algorithm computing NIAC and GNIAC is discussed. Experiments on simulating data sets and typical nonlinear prediction models indicate remarkable correlation between optimal auto-regressive order and the highest order that NIAC-GNIAC have a remarkable non-zero value, therefore demonstrate the validity of the proposal in this paper.  相似文献   

河西地区内陆河流域地表水资源及动态趋势分析   总被引：1，自引：0，他引：1  

杜虎林高前兆李福兴 《资源科学》1996,18(2):44-54

河西地区是甘肃省主要经济地区之一，是国家下世纪初大规模开发大西北的纽带与依托。河西地区未来的经济发展规模，在很大的程度上取决于本地区水资源的承载能力。本文对河西地区内陆河流域天然地表水资源进行了计算和评价；对天然地表径流的变化特征进行了分析；并对河西地区>河西地区、内陆河流域、地表水资源、变化特征、动态过程、趋势预测  相似文献   

太阳黑子数的时-频域模型   总被引：2，自引：0，他引：2  

柯熙政  吴振森 《中国科学院研究生院学报》1998,(1)

讨论了将小波变换用于非平稳信号建模的原理,分析了１７００年～１９９３年的太阳黑子数的年均值,提出一种用于非线性非平稳时间序列建模的新方法,与传统方法相比具有独到之处,它适用于需要进行长期预测的情形  相似文献   

一个新的大样本ENSO集合预报系统的发展与检验     

郑飞  朱江 《中国科学院研究生院学报》2010,27(3):420-431

详细介绍了一个新的大样本集合预报系统. 为了减小ENSO(厄尔尼诺-南方涛动)预报中的预报不确定性,该集合预报系统首先基于一个中等复杂程度的耦合模式,利用集合卡尔曼滤波资料同化方法同化有效的海洋观测资料为集合预报系统提供集合初始场;同时,一个发展的用于12个月预报的一阶线性马尔可夫(Markov)随机误差模式被嵌套到集合预报系统中来模拟模式不确定性. 基于1992年11月~2008年10月100个样本的集合回报试验,从确定性预报技巧和概率预报技巧2个方面对集合预报系统的预报水平进行了检验. 该集合预报方法能够很有效地将传统的确定性预报扩展到概率预报领域,且检验结果表明,预报样本均值的预报水平要优于单一的确定性预报. 对于概率预报而言,集合预报样本能够很好地跟随观测的变化,并且能够提供单纯确定性预报所不能够提供的额外信息.  相似文献