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Linkoping, Sweden

Swedish Defence Research Agency is a Swedish government agency for defence research that reports to the Ministry of Defence. It has its headquarters in Kista, Stockholm and other locations in Grindsjön south of Stockholm, Linköping and Umeå. The activities of FOI include research, development of technology and analysis, primarily for military defence, but also for civil emergency, security and other civilian applications.In 2011, FOI employed around 950 people. Wikipedia.

Johansson B.,Swedish Defence Research Agency | Johansson B.,Lund University
Energy | Year: 2013

Energy security is sometimes used to advocate renewable energy systems. Renewable energy systems can improve some aspects of security, but they will not automatically lead to the removal of all types of security problems and new problems will most certainly arise. This paper analyses energy security aspects of renewable energy systems on the basis of a broad typology on energy and security. Renewable energy sources do not suffer from the same long-term resource availability problems as finite fossil resources and their geographical location is less concentrated, but other issues such as dependence on variable flowing resources and competition for scarce land resources will grow in importance. Many security issues related to energy are also dependent on the energy carrier rather than the energy resource and on the existence of effectively functioning institutions and regulations. New interdependencies will appear and will have to be handled within future international and bilateral institutional frameworks. © 2013 The Author. Source

Johansson B.,Swedish Defence Research Agency | Johansson B.,Lund University
Energy | Year: 2013

A broadened typology describing the interconnection between energy and security is developed in this paper, with the aim of improving understanding of the relationship between energy and security by applying different research and policy perspectives. One approach involves studying energy as an object exposed to security threats, using concepts such as security of supply or security of demand. Another approach involves studying the role of the energy system as the subject in generating or enhancing insecurity. The latter approach includes studying the conflict-generating potential inherent in the economic value of energy, the risk of accidents and antagonistic attacks to energy infrastructure and the security risks related to the negative environmental impact of the energy system. In order to make a comprehensive analysis of the security consequences of proposed energy policies or strategies, all these aspects should be taken into account to varying degrees. The typology proposed here could be a valuable tool for ensuring that all security aspects have been considered. © 2013 Elsevier Ltd. Source

Fureby C.,Swedish Defence Research Agency
Flow, Turbulence and Combustion | Year: 2010

In this study, Large Eddy Simulation (LES) has been used to predict the flow, mixing and combustion in both a single burner laboratory gas turbine combustor and in an 18 burner annular combustor, having identical cross sections. The LES results for the single burner laboratory combustor are compared with experimental data for a laboratory model of this combustor, and with other LES predictions, with good agreement. An explicit finite volume based LES model, using the mixed subgrid model together with a partially stirred reactor model for the turbulence chemistry interactions, is used. For the annular combustor, with the swirlers parameterized by jet inflow boundary conditions, we have investigated the influence of the a-priori unknown combustor exit impedance, the influence of the swirler characteristics and the fuel type. The combustion chemistry of methane-air and ndecane- air combustion is modeled by a two-step reaction mechanism, whereas NOx is separately modeled with a one-step mechanism. No experimental data exists for the annular combustor, but these results are compared with the single burner LES and experimental results available. The combustor exit impedance, the swirler-and fuel characteristics all seem to influence the combusting flow through the acoustics of the annular combustor. To examine this in greater detail time-series and eigenmodes of the combustor flow fields are analyzed and comparisons are made also with results from conventional thermoacoustic eigenmode analysis, with reasonable agreement. The flow and pressure distributions in the annular combustor are described in some detail and the mechanisms by which the burners interact are outlined. © 2009 Springer Science + Business Media B.V. Source

Gustafsson F.,Linkoping University | Hendeby G.,Swedish Defence Research Agency
IEEE Transactions on Signal Processing | Year: 2012

The unscented Kalman filter (UKF) has become a popular alternative to the extended Kalman filter (EKF) during the last decade. UKF propagates the so called sigma points by function evaluations using the unscented transformation (UT), and this is at first glance very different from the standard EKF algorithm which is based on a linearized model. The claimed advantages with UKF are that it propagates the first two moments of the posterior distribution and that it does not require gradients of the system model. We point out several less known links between EKF and UKF in terms of two conceptually different implementations of the Kalman filter: the standard one based on the discrete Riccati equation, and one based on a formula on conditional expectations that does not involve an explicit Riccati equation. First, it is shown that the sigma point function evaluations can be used in the classical EKF rather than an explicitly linearized model. Second, a less cited version of the EKF based on a second-order Taylor expansion is shown to be quite closely related to UKF. The different algorithms and results are illustrated with examples inspired by core observation models in target tracking and sensor network applications. © 2011 IEEE. Source

Hoijer M.,Swedish Defence Research Agency
IEEE Transactions on Electromagnetic Compatibility | Year: 2011

The susceptibility of electronic equipment against electromagnetic irradiation depends on irradiation direction and polarisation. We show how this dependency can be taken into account when performing a radiated susceptibility test in the reverberation chamber. In the reverberation chamber the stress onto the equipment under test increases with the number of independent stirrer positions in the same manner as, in open space the stress onto the equipment under test increases with the number of independent irradiation directions and polarisations. © 2011 IEEE. Source

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