我国地壤侵蚀状况与主要影响因素分析

我国土壤侵蚀面积之大 ,已严重的影响和制约国民经济的发展和社会的安定。我们从土壤侵蚀与降雨 ,土壤侵蚀与坡长、坡度 ,土壤侵蚀与植被建设三个方面作了系统分析 ,研究土壤侵蚀的最为关键因子 ,并找出其对生态环境的危害性 ,提出最佳的综合防治对策 ,将土壤侵蚀的危害降低到最低程度。

Semisupervised Dimensionality Reduction and Classification Through Virtual Label Regression

Semisupervised dimensionality reduction has been attracting much attention as it not only utilizes both labeled and unlabeled data simultaneously, but also works well in the situation of out-of-sample. This paper proposes an effective approach of semisupervised dimensionality reduction through label propagation and label regression. Different from previous efforts, the new approach propagates the label information from labeled to unlabeled data with a well-designed mechanism of random walks, in which outliers are effectively detected and the obtained virtual labels of unlabeled data can be well encoded in a weighted regression model. These virtual labels are thereafter regressed with a linear model to calculate the projection matrix for dimensionality reduction. By this means, when the manifold or the clustering assumption of data is satisfied, the labels of labeled data can be correctly propagated to the unlabeled data; and thus, the proposed approach utilizes the labeled and the unlabeled data more effectively than previous work. Experimental results are carried out upon several databases, and the advantage of the new approach is well demonstrated.