Oblique Low-Velocity Impact on Fiber-Metal Laminates

In the present study, oblique low-velocity impact (OLVI) on GLARE fiber-metal laminates (FMLs) has been modeled using finite element analysis (FEA) for the first time. Two types of boundary conditions (BCs) can be considered for impactor in the low-velocity impact: constrained (if the impact angle between the impactor and target remains constant during and after the contact) and free (if rotation of the impactor and change in angle with respect to the target is likely) BCs. The more details of these BCs are described in the paper. The OLVI is numerically modeled for four different impact angles. Effect of BC types and impact angle on energy absorption, as well as maximum contact force, is investigated. Due to lack of experimental results for the OLVI on FMLs in the open literature, the authors had to validate the present modelling via the experimental data of the perpendicular low-velocity impact. An excellent agreement was obtained between the numerical results and the experimental data. The results of present study reveal that at the same impact angle, the maximum contact force and energy absorption are greater for the constraint oblique impact (Constrained OLVI). In addition, in the Constrained OLVI, the maximum energy absorption occurs at larger impact angles, while this occurs at smaller impact angles for free oblique impact (Free OLVI). The conclusion to be drawn from all of the cases studied in this paper is that the maximum contact force occurs in the Constrained OLVI with smaller impact angles. Moreover, the maximum energy absorption takes place in the Constrained OLVI at higher impact angles.     

Robust Tomlinson-Harashima Precoding for Two-Way Relaying

Most of the non-linear transceivers, which are based on Tomlinson-Harashima (TH) precoding and have been proposed in the literature for two-way relay systems, assume perfect channel state information (CSI). In this paper, a novel and robust TH precoding scheme has been investigated for two-way relay systems, with multiple antennas at the transceiver and relay nodes. We assume imperfect CSI and the channel uncertainty is bounded by a spherical region. The minimum mean square error at the destinations is used as the design criterion and we develop an iterative method to solve this nonconvex problem to obtain TH precoding matrices at the transmitter, linear precoding matrix at the relay and linear equalizer at the destination nodes, where each subproblem is convex. Simulations are provided to evaluate the performance and to validate the efficiency of the proposed scheme.

     

Numerical prediction of hydrodynamic cavitating flow structures and their corresponding erosion

Hydrodynamic cavitating flows usually consist of 3-D intense vortical flows that are detached from solid boundaries.Detached vortical flows normally generate he...     

Turbo soft interference cancellation for coded asynchronous ds/cdma

In this paper we propose a Multiuser receiver architecture which removes the Multiple Access Interference (Mai) by means of a Soft Input Soft Output (siso) multiuser detector followed by a bank of channel decoders. The extrinsic information at the output of the channel decoders are used to estimate the values of the interfering bits and the SISO multiuser detector subtracts the vector of the interfering bits from the incoming signal. The resulting vector is then filtered by an adaptive mmse filter to help remove the residual mai. The paper examines the use of such a receiver in the context of a synchronous awgn channel and then we generalize to the case of asynchronous multipath fading channels.     

Robust Output Feedback Model Predictive Control: A Stochastic Approach

This paper addresses the robust explicit model predictive control scheme for linear systems with input and output constraint in the presence of disturbances and noise. Conditions for disturbance rejection are established by incorporating a full state/disturbance observer. The separation principle is applied to design an optimal observer in the unconstrained problem. Then, an efficient algorithm is developed to explicitly design observer gains by minimizing a quadratic performance criterion. It is shown that the solution includes a set of regions with piecewise affine functions of the state and reference vectors and a set of regions with optimal observers. In the proposed method, two sets of partitions associated with the control law and the observer gains are obtained. Therefore, the online computation includes finding the active regions of both observer and control law partitions in which the current state is located. The proposed technique is particularly attractive for a wide range of practical problems where the exact model of the actual system is not available.