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排序方式: 共有1816条查询结果,搜索用时 15 毫秒
1.
李艳梅 《楚雄师范学院学报》2004,19(6):18-19,58
文章考虑了一类具有Z2等变性质的五次哈密向量场的全局性质,得到了其全局相图,并对参数空间进行了划分。 相似文献
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施洁斌 《现代图书情报技术》2004,20(7):27-29
提出了将支持向量机应用于文本自动分类的研究,与常用的K-最邻近法相比,无论是对训练数据集还是测试数据集均具有一定的优势,而且不同特征选择方法对支持向量机的影响要比K-最邻近法小。此外,从研究中的不同特征选择的评价函数来看,它们对分类有一定的影响,应用X2统计进行特征选择的分类正确率最高,其次是文本证据权,而期望交叉熵的效果最差,说明特征选择在文本自动分类中也是相当重要的。 相似文献
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基于机器学习的自动文本分类模型研究 总被引:2,自引:0,他引:2
基于机器学习的方法是自动文本分类中非常重要的一大类方法。本文先给出了形式化的定义,提出了自动文本分类的流程模型,然后选取了支持向量机(Support Vector Machine,SVM)算法作为一个典型例子进行分析,最后作者通过一个中文文本分类实验评价了该算法的效果。 相似文献
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Bast fibres have been commonly used as a textile material in Northern Europe since Neolithic times. However, the process of identifying the different species has been problematic, and many important questions related to their cultural history are still unanswered. For example, a modified Herzog test and the presence of calcium oxalate crystals have both been used in identification. In order to generate more reliable results, further research and advancement in multi-methodological methods is required. This paper introduces a combination of methods which can be used to identify and distinguish flax (Linum usitatissimum), hemp (Cannabis sativa), and stinging nettle (Urtica dioica). The research material consisted of reference fibres and 25 fibre samples obtained from 12 textiles assumed to be made of nettle. The textiles were from the Finno-Ugric and Historical Collections of The National Museum of Finland. The fibre samples were studied by observing the surface characteristics and cross sections with transmitted light microscopy, and by using a modified Herzog test with polarized light, in order to identify the distinguishable features in their morphological structures. The study showed that five out of 25 samples were cotton, 16 nettle, one flax, and one hemp. Findings from two samples were inconsistent. The results show that it is possible to distinguish common north European bast fibres from each other by using a combination of microscopic methods. Furthermore, by utilizing these combined methods, new and more reliable information could be obtained from historical ethnographic textiles, which creates new vistas for the interpretation of their cultural history. 相似文献
5.
Haicheng Li Yinji Ma Ziwei Liang Zhouheng Wang Yu Cao Yuan Xu Hua Zhou Bingwei Lu Ying Chen Zhiyuan Han Shisheng Cai Xue Feng 《国家科学评论(英文版)》2020,7(5):849
According to the statistics of the World Health Organization, an estimated 17.9 million people die from cardiovascular diseases each year, representing 31% of all global deaths. Continuous non-invasive arterial pressure (CNAP) is essential for the management of cardiovascular diseases. However, it is difficult to achieve long-term CNAP monitoring with the daily use of current devices due to irritation of the skin as well as the lack of motion artifacts suppression. Here, we report a high-performance skin-like optoelectronic system integrated with ultra-thin flexible circuits to monitor CNAP. We introduce a theoretical model via the virtual work principle for predicting the precise blood pressure and suppressing motion artifacts, and propose optical difference in the frequency domain for stable optical measurements in terms of skin-like devices. We compare the results with the blood pressure acquired by invasive (intra-arterial) blood pressure monitoring for >1500 min in total on 44 subjects in an intensive care unit. The maximum absolute errors of diastolic and systolic blood pressure were ±7/±10 mm Hg, respectively, in immobilized, and ±10/±14 mm Hg, respectively, in walking scenarios. These strategies provide advanced blood pressure monitoring techniques, which would directly address an unmet clinical need or daily use for a highly vulnerable population. 相似文献
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运用面板向量自回归模型分析后发现:东部地区图书出版对经济增长带来了“先增强后减弱”的正向冲击效应,中部地区的冲击效应既不明显也不稳定,西部地区则呈现负向冲击效应。同时,东部地区出版产业的延伸和知识的外溢使得全国的图书出版带来经济的有效增长。但是,这一效应主要是通过“产业渠道”而非“传播渠道”传导的,这就使得图书出版数量上的扩张只是带动了出版产业的发展,而未能带来出版知识快速且有效的转化。 相似文献
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我们利用“表格法”求二维离散型随机向量的概率分布律,这种方法直观明了,不易漏项,而且一次可以求出多个随机向量函数的概率分布律. 相似文献