null extension 中文意思是什麼
null extension
解釋
空外延-
Single side birth death chain of order 2 in random environment is the extension of random walk in random environment, this paper discusses the recurrence, positive recurrence and null recurrence of single side birth - death chain of order 2 in fixed environment and random environment respectively based on the relation between birth death chain of order 2 and branching chain in time environment, and gives some sufficient and necessary conditions and sufficient conditions
摘要隨機環境中單邊二重生滅鏈是隨機環境中單邊隨機游動的推廣，本文利用單邊二重生滅鏈與依時分枝鏈的關系，分別給出了固定環境及隨機環境中二重生滅鏈的常返，正常返和零常返的幾個充要及充分條件，隨機環境中的單邊隨機游動的常返性的相應結果可以作為本文的推論。 -
To the incomplete information systems, the dissertation suggests a new method to impute the null values. the method is based on the extending model of rough sets and fully considers the consistence of data and dependency of attributes. this method can not only avoid deleting those entities including null values, but also avoid redundant extension of the incomplete information system
對于不完全信息系統，本文利用粗糙集擴展模型，在充分考慮數合肥工業大學博士論文摘要據相容性和屬性依賴性的情況下，對缺失值進行了有效的估算，既防止了刪除含有空值的對象，使系統缺少典型性，又防止出現過多的、擴展的完全系統。
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