in order to effect of different mulch materials and optimal chemical, organic and biological fertilizer management on ecological agriculture characteristics in common purslane (portulaca oleracea l.) in khuzestan conditions, a filed experiment was conducted at experimental field of ramin agriculture and natural resources university in ahwaz, south-western of iran, during 2010- 2011 growing seas...

In this paper we study width of semi-algebraic proof systems and various cut-based procedures in integer programming. We focus on two important systems: Gomory-Chvátal cutting planes and LovászSchrijver lift-and-project procedures. We develop general methods for proving width lower bounds and apply them to random k-CNFs and several popular combinatorial principles like the perfect matching prin...