the paper examines industrial concentration in iranian food products and beverages industries using firm level data aggregated to the 4-digit isic industry level between 2002 and 2004. based on different concentration indices the average level of concentration has increased slightly for the period of study. the empirical results show that increase in the level of concentration is more likely in...

introduction: market power is an important factor affecting welfare. existence of market power on the purchase side reduces supplier welfare. however, existence of market power on the sales side reduces supplier welfare. some believe that the agricultural market structure is a monopoly. in fact, most of the agricultural products can be purchased by small firms and then delivered to consumers be...

following our previous presentation of a new three-fold symmetry for derivation of the magic numbers of nuclei based upon a quark state model of nuclei, here the nuclear binding energy is obtained from such new perspective. from this point of view, since each nucleon is made of three quarks, the binding energy of nuclei contains a volume term proportional to 3a (a is mass number). by considerin...

in this paper energy bands and berry curvature of graphene was studied. desired hamiltonian regarding the next-nearest neighbors obtained by tight binding model. by using the second quantization approach, the transformation matrix is calculated and the hamiltonian of system is diagonalized. with this hamiltonian, the band structure and wave function can be calculated. by using calculated wave f...

this paper shows the role of the general dynamic model in empirical research of production technology in agriculture. the model is a first order autoregressive multivariate specification, first developed by anderson and blundell. this model is general enough to nest several simpler dynamic as well as static models within it. therefore, it provides a framework for applying classical testing ...

the predator-prey model with stage structure for predator is generalized in the context of ecoepidemiology, where the prey population is infected by a microparasite and the predator completely avoids consuming the infected prey. the intraspecific competition of infected prey is considered. all the equilibria are characterized and the existence of a hopf bifurcation at the coexistence equilibriu...