一端有界的非凸守恒律的Riemann问题

考虑一端有界的非凸单个守恒律的Ｒｉｅｍａｎｎ问题，构造性地得到了该问题的整体弱解，同时澄清了解的结构，并给出了一个实例及仿真结果。     

A quantitative survey of the aquatic invertebrate community in the “Monumento natural Salar de Surire” on the Chilean Altiplano

A quantitative survey of the aquatic invertebrate community at a salar on the Chilean Altiplano is described. To establish the taxonomic composition and abundance we monitored inter-annual changes in community structure for four consecutive years covering different conditions. The community was composed of 21 taxa, representing 16 families, and was mainly dominated by arthropods. We found a high number of endemic species compared to other freshwater systems despite the low abundances detected. There were statistically significant inter-annual differences in diversity. A canonical correlation indicated that species richness was mainly affected by temperature. We studied this unique system by taking advantage of the “natural laboratory” that it offers. We found a combination of eutrophic conditions with low species diversity at the consumer level. This system invites further research on the community dynamics and microevolutionary aspects of invertebrate populations.     

基于PLC的混合光伏自动跟踪系统设计

为提高太阳能转换效率,设计了一种新型混合式太阳能自动跟踪系统.该系统采用程序跟踪和圆弧传感器跟踪相结合的两级跟踪方式,用PLC可编程逻辑控制器为控制核心实现自动跟踪.实验结果表明,该系统跟踪精度高,波动小,效率高.