This paper aims at investigating the superiority of power allocation strategies, based on calculus of variations in a point-to-point two-way relay-assisted channel incorporating the amplify and forward strategy. Single and multilayer coding strategies for two cases of having and not having the channel state information (CSI) at the transmitters are studied, respectively. Using the notion of cal...

background and aims. gingival recession (gr), a common problem in periodontium, is associated with various etiologic factors. there is controversy over the role and importance of these factors. the aim of this study was to evaluate the etiologic factors of gr in a group of subjects in northwest iran. materials and methods. in this case-control study, patients referring to a university clinic (1...