Optimal selection of reference set for the nearest neighbor classification by Tabu search

In this paper,a new approach is presented to find the reference set for the nearest neighbor classifer.The optimal reference set,which has minimum sample size and satisfies a certain error rate threshold,is obtained through a Tabu search algorithm.When the error rate threshold is set to zero,the algorithm obtains a near minimal consistent subset of a given training set.While the threshold is set to a small appropriate value,the obtained reference set may compensate the bias of the nearest neighbor estimate.An aspiration criterion for Tabu search is introduced,which aims to prevent the search process form the inefficient wandering between the feasible and infeasible regions in the search space and speed up the convergence.Experimental results based on a number of typical data sets are presented and analyzed to illustrate the benefits of the proposed method.Compared to conventional methods,such as CNN and Dasarathy‘s algorithm,the size of the reduced reference sets is much smaller,and the nearest neighbor classification performance is better,especially when the error rate thresholds are set to appropriate nonzerovalues,The experimental results also illustrate that the MCS(inimal consistent set)of Dasarathy‘s algorithm is not minimal,and its candidate consistent set is not always ensured to reduce monotonically.A counter example is also given to confirm this claim.     

近邻法参考样本集的最优选择

为克服近邻分类法需要大量计算和存储的缺点,本文利用Tabu搜索来求解满足一定错误率条件的最小参考样本集.当错误率阈值设为0时,可以得到原训练集的一致子集.当错误率阈值设为适当的非零值时,可以较好地克服近邻估计的偏置.通过在Tabu搜索中引入适当的激活(aspiration)条件,避免了在可行和不可行解区间无意义的来回搜索,加快了收敛的速度.实验结果表明,本文算法在压缩比和分类性能上都优于经典的算法.本文还证明了Dasarathy的算法^[6]得到的最小一致子集(Minimal Consistent Set: MCS)不是最小的,其MCS也不一定是单调减的.     

交联聚合物驱油机理研究

该文用微观和宏观两种渗流实验方法研究了交联聚合物的驱油机理，认为交联聚合物不但有调剖作用，同时还具有驱油作用。交联聚合物可明显改善油藏高含水期水驱油效果，控制含水上升速度。在注水时，以适当的主段塞和副段塞组合可获得较好的增油降水效果。在该实验条件下，推荐段塞组合为：主段塞０．２ＰＶ，不加清水隔离段塞，副段塞０．０５～０．１ＰＶ。实验采用此段塞组合可提高采收率２０％～２６％。含水率下降３０％以上。     

交联聚合物剪切特性及渗流规律研究

研究了交联聚合物剪切和剪切后再交联的特性及其在孔隙介质中的渗流规律。用机械剪切、在孔隙介质中流动剪切和段塞渗流三种实验方法，用ＵＶ－３０００紫外分光光度计分析出口样品，用付里叶变换红外ＦＴ－ＩＲ漫反射技术分析模型中滞留的聚合物分布。结果表明：未交联的交联聚合物体系在地层条件下和经岩心剪切后都能交联增粘，剪切粘度损失可达７５％以上，停止剪切后在６０℃下静置，粘度在当天即开始回升，３～４天升到最大值，尔后逐渐下降；交联聚合物受机械剪切，粘度可降到原值的０．０７％，但停止剪切后２～４天可恢复到８５％，最大约９０％；交联聚合物注入岩心后再水驱，由于水窜流，驱出聚合物量只有３０％左右，滞留的聚合物在岩心各段均有分布，而入口处的滞留量明显高于其它部位。因此，交联聚合物有较好的抗剪切性，现场应用时具有调剖和驱油双重功能。     

Tabu搜索在特征选择中的应用

研究利用Tabu搜索从大特征集中选择一组有效特征的问题.分析了Tabu搜索中 表长、邻域大小和候选解数量等参数对Tabu搜索的影响.对两种特征选择的问题,与经典及 最近新提出的一些特征选择方法如SFS,SBS,GSFS,GSBS,PTA,BB,GA和SFFS,SFBS等 算法的实验比较表明,Tabu搜索在求解时间和解的质量上都取得了满意的结果.