A study on relationship between the return of value/growth portfolio and market return: Evidence from Tehran Stock Exchange

This study examines the relationship between the returns of two value and growth portfolios and the return of market on 15 selected firms on Tehran Stock Exchange over the period 2008-2011. The study divides the firms into two groups in terms of the ratios of price on earning as well as price on book value into two groups of value and growth portfolios. Using some regression analysis, the study has determined a positive and meaningful relationship between value portfolio and market return when the market is on the upside but this relationship is not meaningful during the bear session. The results indicate that during the bull sessions, value portfolios provide better investment opportunities than growth ones do

Enhancing the Performance and Stability of SDN Architecture with a Fat-Tree Based Algorithm

Due to the development of networks, SDN, which stands for Software-defined networking, was introduced to resolve the demands of the community. The focus of SDN is reasonably on the control panel, and other devices only transmit data. Nevertheless, due to the division of the data and control layer, there exist still some problems, such as the rise in the load on the central controller and the failure of the network. As a consequent, two general steps have emerged in order to reduce the load on the controller. The first step is obtaining the shortest path through Dijkstra algorithm which is similar for all controllers, but the second step is variable in each load reducing approach. Accordingly, In this research, we came up with an innovative solution based on a central controller among several distributed controllers, and an OpenFlow switch which operates as an intermediate controller. Further, we adopt a FloodLight controller, a Fat Tree topology with 64 hosts, 8 switches, and a central controller. The major contrast between our topology and other Fat Tree topologies is in the combination of intermediate switches to hosts. As a result, the outcomes taken in this work indicate that the processing time of each stream is reduced to 0.1 milliseconds. Moreover, Our solution diminishes the broken flows as well as their differentiation. Furthermore, due to the usage of alternative routes and lessening the time required to process each load, the overall load on the controller is decreased and the network does not crash