Utility-based adaptive radio resource allocation in OFDM wireless networks with traffic prioritization

In this letter, a joint transmit scheduling and dynamic sub-carrier and power allocation method is proposed to exploit multi-user diversity in downlink packet transmission in an OFDM wireless network with mixed real-time and non-real-time traffic patterns. To balance efficiency and fairness and to satisfy the QoS requirements of real-time users, we utilize a utility-based framework and propose a polynomial-time heuristic algorithm to solve the formulated optimization problem. The distinguishing feature of the proposed method is that it gives in one shot, the transmission scheduling, the sub-carriers assigned to each user, and the power allocated to each sub-carrier, based on a fair and efficient framework while satisfying the delay requirements of real-time users.     

Finite element analysis of blood flow characteristics in a Ventricular Assist Device (VAD)

The replacement or augmentation of failing human organs with artificial devices and systems has been an important element in health care for several decades. There are a lot of geometrical and flow considerations in the artificial organs that are developed to perform in contact with the blood particles. For example, preventing the stagnation, high pressure and shear regions is an important consideration in artificial organ design. In this paper, the geometrical and boundary conditions for the blood flow in the HeartSaver Ventricular Assist Device (VAD) are studied using the numerical solution of the governing equations. In order to provide the interaction between the blood and the elastic diaphragm and between the blood and the inlet/outlet valves, the Fluid-Structural Interaction (FSI) approach is used in this study. Arbitrary Lagrangian–Eulerian (ALE) Finite Element Method (FEM) formulation is used for the numerical solution of the flow domain. Blood and the driving fluid are assumed as isothermal, Newtonian, viscose and incompressible fluids. The numerical solution has provided the required characteristics for the evaluation of the performance of the VAD in contact with the realistic flow conditions. Although they present the formation of wakes in the blood chamber, no stagnation points and high shear rate zones are detected in the blood chamber.