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21.
区域农业水资源系统是与自然及人类活动紧密联系的复杂适应系统,不断与周围环境发生物质、能量和信息因素方面的交换和作用。以黑龙江省农垦红兴隆管理局12个农场为研究基点,运用主成分-相关分析法筛选评价指标,构建农业水资源恢复力评价指标体系,采用CRITIC法确定指标权重,结合可变模糊模型评价方法对其农业水资源系统恢复力进行评价,并利用ArcGIS技术对其进行分区,结果表明:双鸭山、八五三、北兴和八五二农场的农业水资源恢复力为Ⅱ级,饶河、二九一、五九七、红旗岭、友谊、江川、宝山和曙光的农业水资源恢复力为Ⅲ级。研究成果揭示了当地农业水资源系统力恢复情况,为农业水资源系统恢复力研究提供了一种新的研究模式。 相似文献
22.
为探究梨火疫病菌解淀粉欧文氏菌Erwinia amylovora在全球的潜在地理分布,基于其全球分布数据和筛选得到的环境变量,利用MaxEnt模型对其在当前气候和未来气候条件下的潜在地理分布进行预测,并利用刀切法和皮尔逊相关性分析法筛选对梨火疫病菌分布有重要影响的环境变量。结果显示,对梨火疫病菌分布有重要影响的环境变量包括2月平均最高温度、1月平均降水量、7月平均最低温度、温度变化方差、昼夜温差月均值和7月平均降水量,表明春季和夏季的温度和降水对梨火疫病菌的分布有较大影响。在当前气候条件下,梨火疫病菌在全球的适生区分布较广,适生区总面积达到5.58×107 km2,且高适生区主要分布在北美洲沿海地区、地中海沿岸和亚洲中部及东部的部分地区;梨火疫病菌在我国的适生区总面积为7.36×106 km2,占全国陆地总面积的76.70%;在未来气候SSP126和SSP585情景下,梨火疫病菌在全球的适生区总面积分别为5.52×107 km2和5.24×107 km2。表明梨火疫病菌对我国大部分地区有潜在威胁,应加强监测与防控。 相似文献
23.
Nickolas G. Kavallieratos Maria C. Boukouvala Artemis Phoebe A. Pappa Angelo Canale Giovanni Benelli 《Pest management science》2023,79(12):5230-5236
BACKGROUND
Sublethal effects of insecticides may negatively affect several biological and behavioral traits of insects. The lethal effects of pirimiphos-methyl and chlorfenapyr have been previously showed on Trogoderma granarium, but little knowledge is available about their sublethal effects at low concentrations on both sexes. Herein, the sublethal effects of pirimiphos-methyl and chlorfenapyr on the mobility of T. granarium males and females were investigated.RESULTS
Lethal concentration (LC) values of pirimiphos-methyl and chlorfenapyr were lower for T. granarium females than males. LC values on males were LC10 = 0.000788 and 0.00139 mg active ingredient (a.i.) cm−2, LC30 = 0.00350 and 0.00535 mg a.i. cm−2, and LC50 = 0.00986 and 0.0136 mg a.i. cm−2 for pirimiphos-methyl and chlorfenapyr respectively. LC on females were LC10 = 0.000704 and 0.00110 mg a.i. cm−2, LC30 = 0.00323 and 0.00428 mg a.i. cm−2, and LC50 = 0.00925 and 0.0110 mg a.i. cm−2 for pirimiphos-methyl and chlorfenapyr respectively. The walking duration of beetles exposed to LC30 of pirimiphos-methyl was significantly lower than the individuals exposed to LC10 and LC30 of both insecticides and control ones. Pirimiphos-methyl LC30-exposed males remained more time on their back (101.7 s) than females (46.9 s), while the latter stayed immobile longer than males (381.7 s versus 371.9 s). The highest speed was recorded for control beetles (14.17 mm s−1 females vs. 12.44 mm s−1 males), while the lowest speed was observed in pirimiphos-methyl LC30-treated males (8.36 mm s−1) and females (9.66 mm s−1).CONCLUSIONS
Overall, males and females exposed to low concentrations of pirimiphos-methyl and chlorfenapyr showed reduced motility. This knowledge can be exploited further to unlock behavioral effects of insecticides for effective pest management programs in warehouses. © 2023 Society of Chemical Industry. 相似文献24.
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26.
Reference efficiency of a pair of gear drive without planetary motion is the base to calculate efficiency of the whole planetary gear train. The authors find reference efficiency for speed increase is higher than that of the same drive used for speed reduction. This is different from the earlier viewpoint. New equations are derived for correctly calculating the reference efficiency of spur gear and helical gear with internal conjugate and external conjugate either in the state of speed increase or speed reduction respectively. The equations are also used to calculate efficiency of 2K-H planetary gear train. 相似文献
27.
Zhang Xiangwei Xu Meihe 《保鲜与加工》1991,(4):8-15
The reliability of random vibration is discussed,and then by using the first order perturbation method and with the aid of relation of the systemic response function to the first order sensetivity of variable damp parameter, the rate of change of structural reliability indication is derived, therefore the constraint equation to guarantee reliability for the structural optimization design is proved and the satisfactory result is obtained,test and the practicability of this method is tested. 相似文献
28.
Zhang Wei Ren Zhen Qin Yihong Liao Qing 《保鲜与加工》1990,(1):56-62
A flexible mathematical model used for dynamic simulation studies of HVDC systems which is based on the stale variable method is presented, and the correspongding computer program has been implemented. Generality, easy to use, and suitable to run on microcomputers are the main features of the model and the computer program. Therefore the model is easy to be extended for application. An example is given in the paper to verily the coneclness of the model and the program. 相似文献
29.
In 1995, Padmanabhan and Vrat presented inventory models for deteriorating items with a constant selling price and stock dependent selling rate . Based on the result, in 2000, Kun-Jen Chung, Peter Chu and Shaw-Ping Lan devoloped the necessary and sufficient conditions of the existence and uniqueness of the optimal solutions of the profit per unit time functions without backlogging and with complete backlogging. Actually, the selling price need not be constant, it may be variable . This paper puts forward an EOQ model when the selling price is variable without backlogging, discusses the existence and uniqueness of optimum solution. The example is provided to illustrate the model. The theoretical evidence is provided for the inventory system to make management decision. 相似文献
30.
In accordance with the deficient elongation of the Stretching-bending Rectifier, as well as the severe wear and slipping of V-belt , the driving system velocity ratio of rectifier and the calculation formula of the theoretical elongation are deduced, which are based on the analysis of its structure and reeling principle. The carrying capacity of the driving system is also analyzed and it reaches the main reason for the elongation of the stretching-bending rectifier that cannot reach request, which is caused by the step less torsion of fixed output of the continuously variable transmission. The improvement measure which can be achieved by increasing the stiffness of the spring to increase the output torsion of the continuously variable transmission is proposed. Thus it makes the actual coefficient of elongation,which can satisfiy the producing request. 相似文献