A necessary and sufficient LMI condition for stability of 2D mixed continuous-discrete-time systems

WeA10 Regular Session: Linear Systems I, Paper WeA10.6This paper addresses the problem of establishing stability of 2D mixed continuous-discrete-time systems. Traditional stability analysis for 2D systems gives a sufficient condition based on 2D version of a Lyapunov equation. Here, a linear matrix inequality (LMI) condition is proposed that extends these results by introducing complex Lyapunov functions depending polynomially on a parameter and by exploiting the Gram matrix method. It is shown that this condition is sufficient for 2D exponential stability for any chosen degree of the Lyapunov function candidate, and it is also shown that this condition is also necessary for a sufficiently large degree. Moreover, an a priori bound on the degree required for achieving necessity is given. Some numerical examples illustrate the proposed methodology.published_or_final_versio

Mean winds of the mesosphere and lower thermosphere at 52° N in the period 1988?2000

International audienceA meteor radar in the UK (near 52° N) has been used to measure the mean winds of the mesosphere/lower-thermosphere (MLT) region over the period 1988?2000. The seasonal course and interannual variability is characterised and comparisons are made with a number of models. Annual mean wind trends were found to be + 0.37 ms-1 yr-1 for the zonal component and + 0.157 ms-1 yr-1 for the meridional component. Seasonal means revealed significant trends in the case of meridional winds in spring ( + 0.38 ms-1 yr-1) and autumn ( + 0.29 ms-1 yr-1), and zonal winds in summer ( + 0.48 ms-1 yr-1) and autumn ( + 0.38 ms-1 yr-1). Significant correlation coefficients, R, between the sunspot number and seasonal mean wind are found in four instances. In the case of the summer zonal winds, R = + 0.732; for the winter meridional winds, R = - 0.677; for the winter zonal winds, R = - 0.472; and for the autumn zonal winds R = + 0.508

Supersonic aircraft Patent

Design of supersonic aircraft with novel fixed, swept wing planfor

Hysterectomy, endometrial destruction, and levonorgestrel releasing intrauterine system (Mirena) for heavy menstrual bleeding : systematic review and meta-analysis of data from individual patients

Peer reviewedPublisher PD

Modelling the tongue-of-ionisation using CTIP with SuperDARN electric potential input: verification by radiotomography

Electric potential patterns obtained by the SuperDARN radar network are used as input to the Coupled Thermosphere-Ionosphere-Plasmasphere model, in an attempt to improve the modelling of the spatial distribution of the ionospheric plasma at high latitudes. Two case studies are considered, one under conditions of stable IMF <I>B<sub>z</sub></I> negative and the other under stable IMF <I>B<sub>z</sub></I> positive. The modelled plasma distributions are compared with sets of well-established tomographic reconstructions, which have been interpreted previously in multi-instrument studies. For IMF <I>B<sub>z</sub></I> negative both the model and observations show a tongue-of-ionisation on the nightside, with good agreement between the electron density and location of the tongue. Under <I>B<sub>z</sub></I> positive, the SuperDARN input allows the model to reproduce a spatial plasma distribution akin to that observed. In this case plasma, unable to penetrate the polar cap boundary into the polar cap, is drawn by the convective flow in a tongue-of-ionisation around the periphery of the polar cap

Crew Motion and the Dynamic Environment of Spaceborne Experiments

Analytical study of crew motion on dynamic environment of orbiting laboratorie

P3_6 Cavorite Pt 2: the Gravity of the Situation

We continue to explore the gravitational and atmospheric effects of Cavorite, a fictional material that is “opaque to gravitation”, by attempting to form a simplified gravitational model of the situation. This gravitational model was found to define the range at which gravitational acceleration will return to near normal as between 0.02 and 12 m. Further research is required to truly model the gravitational acceleration due to Cavorite

P3_4 Elysium: Where'd the Atmosphere Go?

This paper determines whether the Elysium space station, from the 2013 film Elysium[1], could maintain an atmosphere. We found that Elysium, with a radius of 20 km[2], would not hold onto its atmosphere unless high wind speeds (183 ms^-1, 324 ms^-1, and 443 ms^-1; for the atmospheric rotations tested) are to be endured by its inhabitants