Web网页中往往包含许多主题噪声,准确地自动抽取关键词成为技术难点。提出了一个文本对象网络模型DON,给出了对象节点的中心度概念和基于中心度的影响因子传播规则,并据此自动聚集DON中的主题社区(topic society),从而提高了模型的抗噪能力。提出一个基于DON的网页关键词自动抽取算法KEYDON(Keywords Extraction Algorithm Based on DON)。实验结果表明,与基于DocView模型的相应算法相比,KEYDON的准确率提高了近20%,这说明DON模型具有较强的抑制主题噪声能力。
In Fourier transform profilometry （FTP）, we must restrain spectrum overlapping caused by the nonlinearity of the charge coupled device （CCD） and increase the measurement accuracy of the object shape. Firstly, the causes of producing higher-order spectrum components and inducing spectrum overlapping are analysed theoretically, and a simple physical ex- planation and analytical deduction are given. Secondly, aiming to suppress spectrum overlapping and improve measurement accuracy, the influence of spatial carrier frequency of projection grating on them is analysed. A method of increasing the spatial carrier frequency of projection grating to restrain or reduce the spectrum overlapping significantly is proposed. We then analyze the mechanism of how the spectrum overlapping is reduced. Finally, the simulation results and experimental measurements verify the correction of the proposed theory and method.
