While the forward trajectory of a point in discrete dynamical system is always unique, general can have infinitely many backward trajectories. The union limit points all trajectories through $x$ was called by M.~Hero "special $\alpha$-limit" ($s\alpha$-limit for short) $x$. In this article we show that there hierarchy $s\alpha$-limits under iterations S-unimodal map: size $s\alpha$-limit increa...

in this paper, the removal of phenol by using aqueous solution in a low pressure reverse osmosis membrane was investigated. the effect of feed pressure, feed concentration, feed flow rate and feed ph on phenol rejection was investigated. the results showed that feed ph is the most affective parameter on the phenol rejection. rejection of phenol increased with increasing ph from 2 to 10 under th...

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