NATURAL ADJUSTMENT OF POPULATION DENSITY OF LARCH CASEBEARER(COLEOPHORA DAHURICA)

Population increase of Larch casebearer(C. dahurica)were controlled by compre-hensive factors.Spring wind caused 27％ of larvae on crown to fa11 down.Early and late frosts,larch catempillar,sawfly and needle cast of larch could reduce the food quality and quantity of larchcasebearer and had indrect effects on population density. Birds,ants and spites were the mainpredators of C.dahurica. The parasite complex comprised Piermalebae,Eulophidae,Ichneumonidaeand Braconidae."Self--adjustment",of population caused by"self--population density",only runseffectively at a high larval density.

一种新型风电场虚拟惯量协同控制策略

常规比例—微分(PD)虚拟惯量控制策略可使直驱式风电机组为系统提供频率支撑,但其控制参数和算法固定,在风电场多机并网条件下调频效果欠佳。文中给出了PD虚拟惯量控制方式相关参数的整定方法,分析了不同风速区机组转子动能和变流器容量对机组调频能力的影响。据此提出了一种考虑机组间调频能力差异的虚拟惯量协同控制策略,该策略引入转子动能评估因子和变流器容量限制因子以体现功率协调。风电场仿真结果表明,该控制策略在充分发挥各机组调频能力的同时避免了系统频率的二次跌落现象,调频效果得到进一步改善。

落叶松枯梢病发生与温差及风力的关系

根据勃利县林业局通天一林场种子园1986～1991年的气象资料，对5、6月的日最高气温与日最低气温的温差和日最大风力的日数进行概率分析。结果表明，我国引发落叶松枯梢病发生的环境条件与日本不同，温差和风力是引发该病的主要诱因。