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71.
七星瓢虫对两种麦蚜控制作用的模拟研究 总被引:5,自引:0,他引:5
应用二次回归旋转组合设计方法研究了七星瓢虫成虫、幼虫与两种麦蚜共存系统中瓢虫对麦长管蚜和禾谷缢管蚜的捕食量模型。结果表明七星瓢虫对两种麦蚜的捕食量随着瓢虫密度的增加而减少.随着该种麦蚜密度的增加而增加.且七星瓢虫无选择性。七星瓢虫不同个体间的干扰作用对其捕食麦长管蚜数量有显著影响,两种麦蚜数交互作用对七星瓢虫捕食禾谷缢管蚜数量影响显著。该模型可用来预测田间蚜虫的变化.指导麦田蚜虫防治。 相似文献
72.
论述和分析木质剩余物复合材料老化的原因,主要有木质剩余物的老化、胶粘剂的老化、木质剩余物的回弹和膨胀—收缩应力。综合论述木质剩余物复合材料加速老化试验方法,指出木质剩余物复合材料在加速老化试验方面的研究,适宜采用ASTM D1037六循环加速老化法和老化仪检侧法。分析木质剩余物复合材料老化的影响因素,如温度、湿度、试件尺寸等。 相似文献
73.
As the most important cultural practices for ramie (Boehmeria nivea) production,the single effects of plant density and nitrogen (N),phosphorus (P),potassium (K) fertilization on yield are well documen... 相似文献
74.
《食用菌学报》2007,(2)
The composition of fermentation medium for producing Cordyceps brasiliensis mycelium was optimized using response surface methodology. A Plackett-Burman design was applied to screen potential key factors selected on the basis of preliminary experiments, and the steepest ascent method was adopted to approach the approximate optimal medium composition. Finally, central composite design and response surface methodology were applied to define more precisely the optimal composition of the fermentation medium. Our data revealed glucose and beef extract to be the most influential parameters, and the composition of the optimal fermentation medium (100 mL) was determined to consist of 4.46 g glucose, 2 g soluble starch, 4 g silkworm powder, 2.93 g beef extract, 0.10 g KH2PO4 and 0.15 g MgSO4·7H2O. 相似文献
75.
对竹基纤维复合材料进行两种条件(80℃处理8h和50℃处理24 h)的热固化处理后,观测其表观形貌,并进行拉伸、压缩、水平剪切性能以及疲劳性能检测.结果表明:经过热固化处理后,竹基纤维复合材料表面有不连续的微小裂纹产生,其拉伸、压缩、水平剪切性能略有提高,疲劳性能则无显著变化. 相似文献
76.
将SiO2与天然橡胶的制备工艺相结合,先以价格低廉的水玻璃为原料,采用溶胶-凝胶法制备SiO2溶胶和凝胶,再以天然鲜胶乳共沉-共凝制备SiO2/NR复合材料,考察了制备工艺条件对复合材料力学性能的影响。结果表明,制备SiO2/NR复合材料较适宜的复合工艺为院水玻璃与乙酸乙酯反应温度30益,乙酸乙酯和水玻璃溶液中所含SiO2的摩尔比n为0.8∶1,水玻璃浓度为6.5%。当SiO2用量为10份时,复合材料的拉伸强度和撕裂强度分别达到了33.4MPa和47.1kN·m-1。 相似文献
77.
Strawberry fruit have a very short shelf-life and senescent period due to their high degree of perishability and infection caused by several pathogens that can rapidly reduce fruit quality. The aim of this study was to determine the efficacy of carboxymethyl cellulose (CMC), hydroxypropylmethyl cellulose (HPMC) and composites with chitosan (CH) coatings on the shelf-life and overall quality of strawberry fruit. Strawberry fruit dipped for 2 min in solutions of CMC (1%), HPMC (1%), CMC (1%) + CH (1%) and HPMC (1%) + CH (1%) were stored at 11 ± 1 °C, 70–75% RH, while the uncoated fruit served as controls. Fruit coated with edible coatings showed significant delays in the change of weight loss, decay percentage, titratable acidity (TA), pH, total soluble solids (TSS) and ascorbic acid content as compared to uncoated control fruit. In addition, the edible coatings had a positive effect on maintaining higher concentrations of total phenolics and total anthocyanins, which decreased in control fruit due to over-ripening and senescence processes. Compared to the controls, all the coatings had positive effects on the inhibition of cell wall degrading enzymes and among all the tested coatings, CMC + CH and HPMC + CH was superior in inhibiting enzyme activity. These findings suggest that the use of CMC 1% + CH 1% and HPMC 1% + CH 1% coatings are useful for extending the shelf-life and maintaing quality of strawberry fruit. 相似文献
78.
喻云水 《中南林业科技大学学报(自然科学版)》1997,(4)
用正交试验法研究了施胶量、热压温度和热压时间3个因素对复合竹碎料板物理力学性能的综合影响.结果表明:热压温度是影响板材物理力学性能的主要因素.较佳工艺参数为,施政量12%,热压温度150℃,热压时间22min,板材物理力学性能能满足混凝土模板材料性能的需要. 相似文献
79.
XUE Fenglian ZHAO Guangjie College of Material Science Technology Beijing Forestry University Beijing P.R.China Postgraduate major research: wood science 《中国林业科技(英文版)》2005,4(2):75-81
In recent years, many researchers all over the worldhave used inorganic compounds to improve theproperties of wood, for inorganic compounds are cheapand can be obtained easily. Furthermore, they havegood functions and are environmental-friendly if theyare well controlled (Chen Zhilin, 2003). Wood-hybridcomposite is a kind of organic-inorganic hybridmaterial(OIH). OIH means that organicmacromolecule material and inorganic material becomea mixed in molecule level to get excellent capabilities… 相似文献
80.