Defence Research Agency

About: Defence Research Agency is a based out in . It is known for research contribution in the topics: Synthetic aperture radar & Radar. The organization has 1211 authors who have published 1109 publications receiving 31542 citations.

Closed loop analysis of a simple aircraft model using bifurcation methods

Abstract: This paper presents work performed into the analysis of nonlinear aircraft dynamics using bifurcation methods. Published work on the application of bifurcation methods to study non-linear aircraft dynamics has been available for many years. These works mainly consider the case of open loop aircraft and the way in which flight dynamic effects give rise to departures. This study, however, conducts a preliminary investigation into the analysis of control laws for closed loop aircraft using bifurcation analysis techniques. Bifurcation methods are initially applied to a simple open loop aircraft model with constant aerodynamic derivatives to demonstrate the use of bifurcation analysis. The bifurcation techniques are then used to analyse a simple control law of the closed loop aircraft model to detect known flaws, that is integrator wind-up and rate limit effects.

Dependency of Military Capabilities on Technological Development

Abstract: Our goal is to get better understanding of different kind of dependencies behind the high-level capability areas. The models are suitable for investigating present state capabilities or future developments of capabilities in the context of technology forecasting. Three levels are necessary for a model describing effects of technologies on military capabilities. These levels are capability areas, systems and technologies. The contribution of this paper is to present one possible model for interdependencies between technologies. Modelling interdependencies between technologies is the last building block in constructing a quantitative model for technological forecasting including necessary levels of abstraction. This study supplements our previous research and as a result we present a model for the whole process of capability modelling. As in our earlier studies, capability is defined as the probability of a successful task or operation or proper functioning of a system. In order to obtain numerical data to demonstrate our model, we conducted a questionnaire to a group of defence technology researchers where interdependencies between seven representative technologies were inquired. Because of a small number of participants in questionnaires and general uncertainties concerning subjective evaluations, only rough conclusions can be made from the numerical results

A Study of the Factors Which Determine the Modulation Speed of a Shallow PN Junction Porous Silicon Led

Abstract: The effect of the chemical thinning of the porous silicon structure on the speed and efficiency of electroluminescent devices, produced by the anodisation of a pn junction in bulk silicon is investigated. Thinning of the silicon wires results in an increase in the efficiency but at the expense of a reduction in operating speed. It is demonstrated that the operating speed is limited by the photoluminescence lifetime for small signal excitation. However, for large signals, the electroluminescence can be turned off more than 5 times faster than the photoluminescence lifetime, indicating that this need not necessarily limit device operating speed.