关于网片剪裁和网片增减目计算中若干问题的探讨

网片的剪裁和增减目计算，它是网具设计和工艺计算中不可缺少的一环。但是，据目前有关资料和教材．在网片的剪裁计算中，一般只讲述了网片剪裁斜率和剪裁循环比这两个基本概念及其计算公式，并在实际计算中，通常地只是在假设剪裁斜率为已知的条件下，

Goals and Key Technology of Fertilizer-pesticide "Double Reduction" and Synergism for Greenhouse Strawberry

In order to develop green good, reduce the use of chemical fertilizer and pesticide, realize ＂double reduction＂ and synergism, improve safety and quality of products, protect the ecological environment and promote the healthy and steady development of strawberry industry, the goals and key technology of fertilizer-pesticide ＂double reduction＂ and synergism for greenhouse strawberry are summed up in this paper targeting at the current situation of strawberry production and combined with the new technology achievements at home and abroad. The key technology includes six items： healthy seedling cultivating technique, soil improvement and continuous cropping obstacle treatment technique, agricultural ecological prevention tech- nique, physicochemical trap of pest control technique, biological control technique and low residual risk chemical control technique.

略论子部的此消彼长与学术变迁

通过比较古代目录学著作中的《汉书·艺文志》、《隋书·经籍志》、《四库全书总目》,可以看出子部类目中的阴阳家、名家、墨家、纵横家逐渐消亡,又增加了艺术、谱录、类书、释家四个类别,子部著作的内容也出现一些变动。子部类目的增减与子部内容的调整,不只是数目的变化,其实还是中国古代学术发展的一个缩影。这变化也体现了中国传统文化因循与革新并进、生生不息的强大生命力。