This study considers a general class of twodimensional, discrete population models where each per capita transition function (fitness) depends on a linear combination of the densities of the interacting populations. The fitness functions are either monotone decreasing functions (pioneer fitnesses) or one-humped functions (climax fitnesses). Conditions are derived which guarantee that an equilib...

the ecological footprint is a useful tool that we can use it to inform the public about the pressure on ecology and the environment. also, by measuring it, policymakers can design and implement the necessary programs to help reduce that pressure. in order to measure the potential impact of future activities and policies of development programs on the environment, it is necessary to study the sh...

springs are the  mechanical parts which have many application in industries. static and dynamic forces cause relaxation in these parts so that they lose some of their free length and reaction force. springs constant are very important in airplane and vailway industry since constant and variable forces are applied to them in period time, therefore it is necessary to avoid decreasing in spring co...

todays, the world development is facing serious water quality issues. since protect of water quality and ecosystem healthy is an important aspect of ecohydrology. the present research aimed to analyze the temporal trends of water quality parameters of mashin zard river station in order to planning long term management approaches. in this research, trend of some significant factors of water qual...