Gillnet Selectivity and Length at Maturity of Nile Tilapia （Oreochromis niloticus L.） in a Tropical Reservoir （Amerti： Ethiopia）

The selectivity of gillnets for Oreochromis niloticus in Amerti reservoir （9°63′ N, 37°23′ E） was determined from gillnets with four mesh sizes （60, 80, 100 and 120 mm）. Four selectivity models （a normal model assuming fixed spread, a normal model assuming that spread is proportional to mesh size, a lognormal model and a gamma model） were fitted to the data by using the share each length＇s catch total （SELECT） method. A total of 657 specimens of Oreochromis niloticus were caught （12.0-35.5 cm total length, TD. The sizes at first sexual maturity were 21.5 cm TL and 18.9 cm TL, respectively, for male and female Oreochromis niloticus. The lognormal selectivity curve provided the best fit to the data according to model deviance estimates with optimum selectivity of 16.66, 22.26, 27.78 and 33.38 cm TL for the 60, 80, 100 and 120 mm mesh sizes, respectively.     

From Sequential Pattern Mining to Structured Pattern Mining： A Pattern-Growth Approach

Sequential pattern mining is an important data mining problem with broad applications. However, it is also a challenging problem since the mining may have to generate or examine a combinatorially explosive number of intermediate subsequences. Recent studies have developed two major classes of sequential pattern mining methods: (1) a candidate generation-and-test approach, represented by (i) GSP, a horizontal format-based sequential pattern mining method, and (ii) SPADE, a vertical format-based method; and (2) a pattern-growth method, represented by PrefixSpan and its further extensions, such as gSpan for mining structured patterns. In this study, we perform a systematic introduction and presentation of the pattern-growth methodology and study its principles and extensions. We first introduce two interesting pattern-growth algorithms, FreeSpan and PrefixSpan, for efficient sequential pattern mining. Then we introduce gSpan for mining structured patterns using the same methodology. Their relative performance in large databases is presented and analyzed. Several extensions of these methods are also discussed in the paper, including mining multi-level, multi-dimensional patterns and mining constraint-based patterns.     

On Reflections and Prospects of Education＇s Return to Life World

教育回归生活已成为对教育的要求,但当前教育语境中＂生活世界＂的模糊状态以及教学实践中＂生活世界＂向＂日常生活＂的简单归一,使得教育并没有向＂生活世界＂回归,甚至有进一步脱离的倾向。对＂生活世界＂基本精神的溯源与反思,有利于人们更好地理解教育回归生活世界的本质意义。同时,教育回归生活世界是一个艰难而又长期的过程,我们要避免虚假的回归,并应认识到教育在此过程中无法自我拯救,只有认识到这些,教育向生活世界的回归才有可能,而不仅仅是把它作为一种理论畅想。     

A Friendly Bridge between Hunan and the World——Opening Speech for the Official Publication of HASTN

At the time when the new millennium comes, I am very delighted at the news that Hunan Agricultural Science & Technology Newsletter(HASTN) in English edition officially starts publicatiou. We think it will certainly establish another more friendly bridge between our Hunan Province and foreign countries in scientific and economic exchange and cooperation during the mportant days when our People's Republic of China is ready to enter the WTO.