A Calibrated Time Domain Envelope Measurement System for the Behavioral Modeling of Power Amplifiers

This paper presents a set-up which enables the generation and the calibrated time domain measurements of complex envelopes of modulated signals at both ports of non linear microwave power amplifiers. The architecture of the characterization tool is given. Examples of error corrected time domain envelopes at the input / output RF ports of a 36 dBm output power – 30dB power gain L-band SSPA are shown. Futhermore, the use of this characterization tool and a suitable processing of measurement data are applied to a novel measurement based behavioral modeling approach of non linear devices accounting for memory effects

A model-based approach to assess the effectiveness of pest biocontrol by natural enemies

Main goal: The aim of this note is to propose a modeling approach for assessing the effectiveness of pest biocontrol by natural enemies in diversified agricultural landscapes including several pesticide-based management strategies. Our approach combines a stochastic landscape model with a spatially-explicit model of population dynamics. It enables us to analyze the effect of the landscape composition (proportion of semi-natural habitat, non-treated crops, slightly treated crops and conventionally treated crops) on the effectiveness of pest biocontrol. Effectiveness is measured through environmental and agronomical descriptors, measuring respectively the impact of the pesticides on the environment and the average agronomic productivity of the whole landscape taking into account losses caused by pests. Conclusions: The effectiveness of the pesticide, the intensity of the treatment and the pest intrinsic growth rate are found to be the main drivers of landscape productivity. The loss in productivity due to a reduced use of pesticide can be partly compensated by biocontrol. However, the model suggests that it is not possible to maintain a constant level of productivity while reducing the use of pesticides, even with highly efficient natural enemies. Fragmentation of the semi-natural habitats and increased crop rotation tend to slightly enhance the effectiveness of biocontrol but have a marginal effect compared to the predation rate by natural enemies. This note was written in the framework of the ANR project PEERLESS "Predictive Ecological Engineering for Landscape Ecosystem Services and Sustainability"(ANR-12-AGRO-0006)

Ressenyes

Index de les obres ressenyades: J. COROMINAS, Geologia i planificació teritoria

Min-Max formulae for the speeds of pulsating travelling fronts in periodic excitable media

This paper is concerned with some nonlinear propagation phenomena for reaction-advection-diffusion equations in a periodic framework. It deals with travelling wave solutions of the equation $$u_t =\nabla\cdot(A(z)\nabla u) +q(z)\cdot\nabla u+ f(z,u), t \in \mathbb{R}, z \in \Omega,$$ propagating with a speed $c.$ In the case of a "combustion" nonlinearity, the speed $c$ exists and it is unique, while the front $u$ is unique up to a translation in $t.$ We give a $\min-\max$ and a $\max-\min$ formula for this speed $c.$ On the other hand, in the case of a "ZFK" or a "KPP" nonlinearity, there exists a minimal speed of propagation $c^{*}.$ In this situation, we give a $\min-\max$ formula for $c^{*}.$ Finally, we apply this $\min-\max$ formula to prove a variational formula involving eigenvalue problems for the minimal speed $c^{*}$ in the "KPP" case

Kuiper Belt Object Sizes and Distances from Occultation Observations

There are several observational campaigns under way to detect kilometer size foreground Kuiper Belt Objects (KBOs) through their occultation of background stars. The interpretation of an occultation light curve, unfortunately, is affected by a geometric degeneracy such that one is unable to determine the KBO size independent of its distance. This degeneracy can be broken through a precise measurement of the relative velocity obtained from simultaneous observations of individual events. While an array of telescopes spread over an area of few square kilometers can be employed, it is unlikely that the relative velocity can be measured to the required accuracy to help break this geometric degeneracy. The presence of diffraction fringes in KBO occultation light curves, when projected sizes of occulted stars are smaller than the Fresnel scale, improves determination of size and distance significantly. In this regard, we discuss the potential role of a dedicated satellite mission for KBO occultation observations. If dwarf stars at the V-band magnitudes of 14th and fainter can be monitored at time intervals of 0.1 seconds with normalized flux errors at the level of 1%, the occultation observations will allow individual KBO sizes and distances to be determined at the level of a few percent or better.Comment: 4 pages, 2 figures, To appear in ApJ Letter

Glossaires et lexiques médiévaux inédits. Bilan et perspectives, édités par Jacqueline Hamesse et José Meirinhos

Ce volume réunit les communications présentées au Colloque sur les glossaires médiévaux qui s’est déroulé à Paris en 2010; ce domaine, exploré autrefois par M. Roques et J. Monfrin, nécessite encore de recherches approfondies pour faire en sorte que ces instruments de travail importants pour les clercs médiévaux soient connus à fond et exploités convenablement. Pourtant, ces études sont la preuve de la vitalité des nombreuses équipes interdisciplinaires qui s’y consacrent. Trois contributions..