Swedish Defence Research Agency

About: Swedish Defence Research Agency is a government organization based out in Stockholm, Sweden. It is known for research contribution in the topics: Radar & Synthetic aperture radar. The organization has 1413 authors who have published 2731 publications receiving 56083 citations. The organization is also known as: Totalförsvarets forskningsinstitut.

Positioning of moving non-line-of-sight targets behind a corner

Abstract: A stand-off radar system with the capability of “seeing” behind corners would be of great importance for civilian surveillance purposes, for automotive radar, or in urban warfare. Detecting moving people and objects in the shadow region of a street corner by exploiting multi-path propagation of radar waves has previously been demonstrated in experimental set-ups. To position the detected targets, a scanning, narrow beam radar system is suggested. Simulations are used to investigate the performance of the system. Targets are found to be positioned with a good accuracy when the geometry of the scene is known. If errors are introduced in the assumed geometry, the obtained positions are still centered on the true tracks.

Social positions and simulation relations

Abstract: Describing social positions and roles is an important topic within the social network analysis. Identi- fying social positions can be difficult when the target organization lacks a formal structure or is partially hidden. One approach is to compute a suitable equivalence relation on the nodes of the target network. Several different equivalence relations can be used, all depending on what kind of social positions that are of interest.One relation that is often used for this purpose is regular equivalence ,o r bisimulation, as it is known within the field of computer science. In this paper we consider a relation from computer science called simulation relation. The simulation relation creates a partial order on the set of actors in a network and we can use this order to identify actors that have charac- teristic properties. The simulation relation can also be used to compute simulation equivalence which is a related but less restrictive equivalence relation than regular equiva- lence that is still computable in polynomial time.We tentatively term the equivalence classes determined by simulation equivalence social positions. Which equiva- lence relation that is interesting to consider depends on the problem at hand. We argue that it is necessary to consider several different equivalence relations for a given network, in order to understand it completely. This paper primarily considers weighted directed networks and we present definitions of both weighted simulation equivalence and weighted regular equivalence. Weighted networks can be used to model a number of network domains, including information flow, trust propagation, and communication channels. Many of these domains have applications within homeland security and in the military, where one wants to survey and elicit key roles within an organization. After social positions have been calculated, they can be used to produce abstractions of the network—smaller versions that retain some of the most important characteristics.

Intrusion detection and the role of the system administrator.

Abstract: Purpose – The expertise of a system administrator is believed to be important for effective use of intrusion detection systems (IDS). This paper examines two hypotheses concerning the system administrators' ability to filter alarms produced by an IDS by comparing the performance of an IDS to the performance of a system administrator using the IDS.Design/methodology/approach – An experiment was constructed where five computer networks are attacked during four days. The experiment assessed difference made between the output of a system administrator using an IDS and the output of the IDS alone. The administrator's analysis process was also investigated through interviews.Findings – The experiment shows that the system administrator analysing the output from the IDS significantly improves the portion of alarms corresponding to attacks, without decreasing the probability that an attack is detected significantly. In addition, an analysis is made of the types of expertise that is used when output from the IDS i...

Scattering and Polarization Properties of the Scarab Beetle Cyphochilus insulanus cuticle

Abstract: Optical properties of natural photonic structures can inspire material developments in diversified areas, such as the spectral design of surfaces for camouflage. Here, reflectance, scattering, and ...

A Single-Carrier Turbo-Coded System for Underwater Communications

Abstract: In the last several years, the Swedish Defence Research Agency (FOI, Stockholm, Sweden) has been engaged in developing a system for underwater (UW) acoustic communications for both point-to-point (P2P) and network applications. The basis of the system is a single-carrier (SC) scheme with recursive equalization on the receiver side. In this paper, we will give a motivation for our choice of SC by discussing some aspects of modulation and coding for UW communication systems from an information-theoretic point of view. The system is able to take advantage of the diversity offered by the multipath and/or by multiple receivers. Due to the great variations in the UW channel, reliable prediction of communication performance in terms of achievable range and data rate is nontrivial. This has motivated the development of a simulation tool called COMLAB, based on combining the communication system with hybrid ray-trace plane-wave time-domain modeling of sound propagation. The simulation tool is designed to account for environmental effects with significant influence on communication performance, including surface and bottom reflections, transmission loss, ambient noise, and ray-path-dependent Doppler shifts caused by moving source, receivers, or surface waves. Short descriptions of the communication system and the simulation tool are given. A comparison of the predicted performance with experiments made at the UAN'11 trials in the Trondheim fjord (Norway) is presented.