‎we call a ring $r$ right generalized semiperfect if every simple right $r$-module is an epimorphic image of a flat right $r$-module with small kernel‎, ‎that is‎, ‎every simple right $r$-module has a flat $b$-cover‎. ‎we give some properties of such rings along with examples‎. ‎we introduce flat strong covers as flat covers which are also flat $b$-covers and give characterizations of $a$-perfe...

In this paper we give a method of constructing homeomorphisms between two small covers over simple convex polytopes. As a result we classify, up to homeomorphism, all small covers over a 3-dimensional prism P(m) with m ≥ 3. We introduce two invariants from colored prisms and two invariants from ordinary cohomology ring, which form a complete invariant system of homeomophism types of all small c...

road network (rn) can affect patterns and distribution of land uses and covers. road network expansion has both direct and indirect impacts on land uses and covers changes. agricultural land conversions (alcs) are especially known as one of the main important types of land use changes. the purpose of this paper, in addition to estimation of the direct impact of rn expansion on alcs, is to evalu...

‎We call a ring $R$ right generalized semiperfect if every simple right $R$-module is an epimorphic image of a flat right $R$-module with small kernel‎, ‎that is‎, ‎every simple right $R$-module has a flat $B$-cover‎. ‎We give some properties of such rings along with examples‎. ‎We introduce flat strong covers as flat covers which are also flat $B$-covers and give characterizations of $A$-perfe...