Saab Automobile AB

About: Saab Automobile AB is a based out in . It is known for research contribution in the topics: Radar & Signal. The organization has 760 authors who have published 890 publications receiving 11811 citations.

Parallel implicit time-accurate Navier-Stokes computations using a coarse grid correction scheme

Abstract: A parallel implicit Navier-Stokes solver is constructed using a block-by-block inversion of the resulting linear system of equations followed by a global coarse grid correction to account for the block coupling. This solver is used to compute two different cases of vortex shedding flows. The efficiency of our method is compared to the efficiency of the method based on pseudotime stepping and multigrid acceleration. This comparison is based on direct comparison of the two methods applied to identical test cases, as well as results reported in the literature. Emphasis is put on scalability as well as mesh sensitivity. It is concluded that the solver is not sensitive to grid stretching and scales well with both problem size and number of processors

Propagation ability of UWB transients through junctions of low-voltage power installation cable

Abstract: It has been shown earlier (D. Mansson et al., 2007) that ultra wide band (UWB) transients can travel in differential mode (DM) along low voltage power installation cables, and deliver large amounts of power to connected equipments. However, branches in the network were not included at that time. In this paper, the ability of UWB transients to propagate through different types of junctions of low voltage power cables is investigated. The received voltage could with very good accuracy be estimated from transmission line theory, either using theoretical calculations or numerical simulations. This was verified experimentally. The decrease in voltage received at the loads of the branches is mainly due to the reflection caused by impedance mismatch at the junction. It is concluded that large voltages can be delivered to unprotected loads, if a UWB transient is injected in DM at another part of the same network.

A framework for performance analysis of geographic delay-tolerant routing

Abstract: A major tool used for evaluating routing protocols in ad hoc and delay-tolerant networks is simulation. Whereas the results from simulations give good insights, they are limited to the specific scenario set-up that is used. If the scenario changes, new and often time-consuming simulations have to be run. Moreover, the simulation time in packet-level simulators with fairly realistic physical layer implementation, such as ns-2, generally grows rapidly in the number of nodes. This practically limits the number of nodes in a simulation, even if the limit can be extended by the use of simulation federations. Larger scenarios can also be facilitated by the use of more abstraction in the physical layer; abstractions that may impact the validity of the results. In this article, we present the forward-wait framework--a mathematical model describing the packet movements for opportunistic geographic delay-tolerant routing protocols. By describing packet movements as a sequence of alternating forwarding and waiting phases, the framework can accurately predict the routing performance. Key input parameters to the framework are random variables describing the forwarding and waiting phases. We show how the properties of the random variables can be derived, both via abstract modeling and small scale ns-2 simulation data. The model is then used to demonstrate the prediction capabilities of the framework in providing results that are close to the (much slower) packet-level simulations.

Demonstration of a formal method for incremental qualification of IMA systems

Abstract: In this paper we address the process of incremental certification/qualification of integrated modular avionic (IMA) systems. The work aims to show that given a scalable avionics architecture we can apply a component-based development process and save some safety analysis effort by reusing design models for components. This creates a formal framework for IMA system safety assessment.