frictional shear stress is usually determined by utilizing the coefficient of friction or the constant friction factor models. the present study deals with finite element analysis of double cup extrusion process to determine the relationship between constant friction factor (m) and coefficient of friction (µ), since the metal flow in this process is very sensitive to frictional conditions. ther...

iran including attractive places and high potential for tourism (external and internal) and investing on tourism industry including social and economic effects leading to constancy of tourism areas. unfortunately, despite high capacity of developing tourism in our country, this capacity has not recognized well and has not utilized for development of iran. the special factors influence on transi...

The linear differential operator with constant coefficients D(y)=y(n)+a1y(n−1)+…+any,y∈Cn(R,X) acting in a Banach space X is Ulam stable if and only its characteristic equation has no roots on the imaginary axis. We prove that of D distinct rk satisfying Rerk>0,1≤k≤n, then best KD=1|V|∫0∞|∑k=1n(−1)kVke−rkx|dx, where V=V(r1,r2,…,rn) Vk=V(r1,…,rk−1,rk+1,…,rn),1≤k≤n, are Vandermonde determinants.