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71.
One of the more well-studied problems in data mining is the search for association rules in market basket data. Association rules are intended to identify patterns of the type: A customer purchasing item A often also purchases item B. Motivated partly by the goal of generalizing beyond market basket data and partly by the goal of ironing out some problems in the definition of association rules, we develop the notion of dependence rules that identify statistical dependence in both the presence and absence of items in itemsets. We propose measuring significance of dependence via the chi-squared test for independence from classical statistics. This leads to a measure that is upward-closed in the itemset lattice, enabling us to reduce the mining problem to the search for a border between dependent and independent itemsets in the lattice. We develop pruning strategies based on the closure property and thereby devise an efficient algorithm for discovering dependence rules. We demonstrate our algorithm's effectiveness by testing it on census data, text data (wherein we seek term dependence), and synthetic data. 相似文献
72.
基于PERT图的虚拟拆装过程建模 总被引:1,自引:0,他引:1
提出了使用PERT图来建立虚拟拆装过程模型的方法,根据零件之间的约束关系构造PERT图及其对应的依赖矩阵,并且能够根据它来指导虚拟拆装训练过程的实施.所提供的方法在对某设备的虚拟维修中得到了验证. 相似文献
73.
SZ绞设备是将单元绞制和缆芯绞制在一道工序完成的一种专业电缆生产设备。SZ绞设备采用了先进的变频调速技术和PLC控制技术,有的还采用了伺服驱动,使其控制快速、精确和可靠。本文就SZ绞设备的电控系统构成及在调试运行中遇到的变频器故障进行了分析。 相似文献
74.
本文分析了矿井提升机的运行特点,详细阐述了英威腾CHV190系列起重提升专用变频器用于永磁同步电动机驱动的节能型矿井提升机的选型配置原则,最后介绍了应用现场的调试步骤及注意事项。 相似文献
75.
This communique presents forced second-order consensus protocols with communication time-delays for the network of agents with double integrator dynamics and gives a measure of the robustness of the protocols to the communication time-delays. By employing a frequency domain method, it is proven that the forced consensus is achieved asymptotically for appropriate time-delay if the network is connected. Particularly, the maximum fixed time-delay that can be tolerated by the network is found. The forced consensus protocols are distributed in the sense that each agent only needs information from its neighboring agents, which reduces the complexity of connections between agents significantly. Numerical simulation results are provided to demonstrate the effectiveness and the sharpness of the theoretical results. 相似文献
76.
Jing Li András Bárdossy Lelys Guenni Min Liu 《Environmental Modelling & Software》2011,26(11):1349-1357
In this paper, a method for environmental observation network design using the framework of spatial modeling with copulas is proposed. The methodology is developed to enlarge or redesign an existing monitoring network by taking the configuration which would increase the expected gain defined in a utility function. The utility function takes the estimation uncertainty, critical threshold value and gain-loss of a certain decision into account. In this approach, the studied spatial variable is considered as a random field in where variations in time is neglected and the variable of interest is static in nature. The uniqueness of this approach lies in the fact that the uncertainty estimation at the unsampled location is based on the full conditional distribution calculated as conditional copula in this study. Unlike the traditional Kriging variance which is a function of mere measurements density and spatial configuration of data points, the conditional copula account for the influence from data values. This is important specially if we are interested in purpose oriented network design (pond) as for example the detection of noncompliance with water quality standards, the detection of higher quantiles in the marginal probability distributions at ungauged locations, the presence or absence of a geophysical variable as soil contaminants, hydrocarbons, golds and so on. An application of the methodology to the groundwater quality parameters in the South-West region of Germany shows its potential. 相似文献
77.
提出一种抗干扰信道估计(AICE)算法用于解决MIMO-OFDM系统信道估计问题。该算法在接收端通过对收到的累加信号进行分解,得到来自不同发射天线的信号,通过消除符号间干扰与子载波间干扰及采用期望值最大迭代算法进行信道估计来减小估计误差,提高信道估计的准确性。与ICE算法的性能比较证明了AICE算法在瑞利衰落信道下具有更好的信道估计均方误差及误比特率性能。 相似文献
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