夏芝麻生长发育规律研究

以驻J1 8为试验材料 ,通过 1 999、2 0 0 0年两年定株观测和分析 ,结果表明 :夏芝麻茎的最快生长时期在出苗后第 2 6～ 65天 ,日平均增长量最大。从出苗至第一对真叶出现需要 7天 ,之后叶片出现所需天数呈递减趋势。从现蕾至开花的时间 ,下部节位蕾需要 7～ 8天 ,上部节位蕾需要 4～ 5天。第 7～ 34节蒴果长度均在 3cm以上。植株中部蒴果有效粒数最多。单蒴粒重与壳重比为 1 .0 0 7～ 1 .1 44时千粒重可达 3.0 0 g以上。蒴果籽粒千粒重低于 1 .85 g时 。

Occurrence Rule and Forecast Method of Cotton Aphid in Poyang Lake Area in Jiujiang City

[Objective] The aim was to explore occurrence rules and forecast methods of cotton aphid in Poyang Lake Area in Jiujiang City to enrich prediction methods of cotton aphid in the area. [Method] The occurrence rules and influencing factors of cotton aphid in Pengze County in 28 years were analyzed with comparative analysis, correlation analysis and wavelet analysis. Furthermore, a long-term forecast model of occurrence grade of cotton aphid and a short-term forecast model of weather condi- tion suitability were established based on stepwise regression. In addition, a forecast test was conducted in cotton area in the north of Poyang Lake. [Result] The wavelet analysis showed that in recent 28 years, oscillating period at 4 years was significant for the occurrence grade of cotton aphid in the north of Poyang Lake, but insignifi- cant for cotton at seedling stage. The comparative and correlation analyses suggest- ed that occurrence of cotton aphid is of significant correlation with winter climate and weather conditions at middle and short periods. The prediction test indicated that long-term forecast model of occurrence grade of cotton aphid and short-term forecast model of weather condition suitability based on stepwise regression can be made use of in the areas with similar climate. [Conclusion] The research provides theoreti- cal references for prevention against cotton aphid in cotton-planting area.

Gully Erosion Regionalization of Black Soil Area in Northeastern China

Gully erosion is the frequent and main form of soil erosion in the black soil area of the northeastern China, which is one of the most important commodity grain production bases in China. It is encroaching upon the fertile farmland there. Regionalization of gully erosion can reveal the spatial distribution and regularity of the development of gully erosion. Based on the eco-geographical regional background features of the black soil area, this study combined the regionalization with influencing factors of the development of gully erosion. GIS spatial analysis, geostatistical analysis, spatial statistics, reclassification, debris polygon processing and map algebra methods were employed. As a result, the black soil area was divided into 12 subregions. The field survey data on type, length, volume and other characteristics indicators of gully erosion were used to calibrate the results. Then the features of every subregion, such as where the gully erosion is, how serious it is, and why it happens and develops, were expounded. The result is not only an essential prerequisite for gully erosion surveys and monitoring, but also an important basis for gully erosion prevention.

Seasonal changes in the demersal nekton community off the Changjiang River estuary

The diversity,community structure and seasonal variation in demersal nekton off the Changjiang(Yangtze)River estuary was evaluated using monthly trawl survey data,collected between December 2008 and November 2009.A total of 95 species(56 teleosts,11 cephalopods,and 28 decapod crustaceans)from 69 genera,49 families and 15 orders were collected.These species could be classifi ed into six groups on the basis of temporal distribution patterns.The resident crab Ovalipes punctatus dominated the community,both in number and biomass.A clear seasonal succession was observed in the species composition.Cluster analysis revealed three primary seasonal groups corresponding to the samples collected in winter-spring,late spring-summer and late summer-autumn.The highest biomass and lowest diversity were observed in summer,while the lowest biomass and highest diversity in winter.The abundance-biomass comparison curves and community composition suggested that the investigated community was moderately disturbed.The results suggest that reduction in fi shing pressure and in the degree of seasonal hypoxia are essential for sustainable resource management off the Changjiang River estuary.

Structural bionic design for high-speed machine tool working table based on distribution rules of leaf veins

High-speed machine tool working table restrains the machining accuracy and machining efficiency,so lightweight design of the table is an important issue.In nature,leaf has developed a plate structure that maximizes the surface-to-volume ratio.It can be seen as a plate structure stiffened by veins.Compared with a high-speed machine tool working table,leaf veins play a role of supporting part which is similar to that of stiffening ribs,and they can provide some new design ideas for lightweight design of the table.In this paper,distribution rules of leaf veins were investigated,and a structural bionic design for the table was achieved based on regulation of leaf veins.First,statistical analysis on geometric structure of leaf veins was carried out,and four distribution rules were obtained.Then,relevant mechanical models were developed and analyzed in finite element software.Based on the results from mechanical analysis on those relevant models,the four distribution rules were translated into the design rules and a structural bionic design for the working table was achieved.Both simulation and experimental verifications were carried out,and results showed that the average displacement of the working table was reduced by about 33.9%.