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用孢子捕捉和病情调查结果,表明小黑杨肿茎溃疡病的流行景象:6月初至6月中旬为初始病情期,7月至8月为流行盛期,9月上旬为流行终止期。气温,相对湿度和降雨三个因子对病情影响很大,气温对病害开始发生期和流行终止期起决定作用。在适宜的温度条件下,病情随时间与相应的湿度、降雨而累加递增。 根据小黑杨肿茎溃疡病的流行规律,在测报时间范围内病情(x_4)与相应时期的平均温度(x_1),平均相对湿度(x_2)、总降雨量(x_3),温湿比(x_5)、湿雨比(x_6)应用多元统计方法建立多元线性回归预测模型:y=-100.468-2.089x_1+1.023x_2-0.076x_3+0.928x_4+324.968x_5+2.755x_6,这个预测式可以预测30天的病情。又用灰色方法建立灰色预测模型,它是由(dx(t))/(dt)+ax(t)=u形成的,α=-0.151,u=15.984,x(t)是病情指数按时点形成的累加序列。此微分方程的解再经累减即可形成预测序列。按距离贴近原则,便可作出中短期预测。两种方法经过对建立模型以外的实际病情进行检验,证明预测式是可信的。
Spore capture and disease survey results show that Populus sclerotiorum prevalence scene: early June to mid June for the initial disease period, July to August for the peak of the epidemic, early September for the epidemic termination. Temperature, relative humidity and rainfall three factors have a great impact on the disease, the temperature of disease onset and termination of the epidemic play a decisive role. In the appropriate temperature conditions, the disease with the corresponding humidity, rainfall and cumulative increase. According to the epidemic law of Populus euphorbiae, the average temperature (x_1), average relative humidity (x_2), total rainfall (x_3), temperature and humidity ratio (x_5) ), Wet rain ratio (x_6) multivariate statistical methods to establish multiple linear regression prediction model: y = -100.468-2.089x_1 + 1.023x_2-0.076x_3 +0.928x_4 +324.968x_5 + 2.755x_6, this prediction can predict the 30-day Condition. The gray prediction model is also established by gray method. It is formed by (dx (t)) / (dt) + ax (t) = u, α = -0.151, u = 15.984, The resulting cumulative sequence. The solution of this differential equation can be followed by the formation of a prediction sequence. Close to the principle of distance, we can make short-term forecasts. Both methods tested the actual condition outside the established model to prove that the predictive formula is credible.