Influence of the Feedback Filter on the Response of the Pulsed Digital Oscillator

This paper introduces a new feedback topology for the Pulsed Digital Oscillator (PDO) and compares it to the classical topology. The `classic' or single feedback topology, introduced in previous works, shows a strong behavior dependence on the damping losses in the MEMS resonator. A new double feedback topology is introduced here in order to help solving this problem. Comparative discrete-time simulations and preliminary experimental measurements have been carried out for both topologies, showing how the new double feedback topology may increase PDO performance for some frequency ranges.Comment: Submitted on behalf of TIMA Editions (http://irevues.inist.fr/tima-editions

Vibrations on pulse tube based Dry Dilution Refrigerators for low noise measurements

Dry Dilution Refrigerators (DDR) based on pulse tube cryo-coolers have started to replace Wet Dilution Refrigerators (WDR) due to the ease and low cost of operation. However these advantages come at the cost of increased vibrations, induced by the pulse tube. In this work, we present the vibration measurements performed on three different commercial DDRs. We describe in detail the vibration measurement system we assembled, based on commercial accelerometers, conditioner and DAQ, and examined the effects of the various damping solutions utilized on three different DDRs, both in the low and high frequency regions. Finally, we ran low temperature, pseudo-massive (30 and 250 g) germanium bolometers in the best vibration-performing system under study and report on the results

Large amplitude dynamics of micro/nanomechanical resonators actuated with electrostatic pulses

International audienceIn the field of resonant NEMS design, it is a common misconception that large-amplitude motion, and thus large signal-to-noise ratio, can only be achieved at the risk of oscillator instability. In the present paper, we show that very simple closed-loop control schemes can be used to achieve stable largeamplitude motion of a resonant structure, even when jump resonance (caused by electrostatic softening or Duffing hardening) is present in its frequency response. We focus on the case of a resonant accelerometer sensing cell, consisting in a nonlinear clamped-clamped beam with electrostatic actuation and detection, maintained in an oscillation state with pulses of electrostatic force that are delivered whenever the detected signal (the position of the beam) crosses zero. We show that the proposed feedback scheme ensures the stability of the motion of the beam much beyond the critical Duffing amplitude and that, if the parameters of the beam are correctly chosen, one can achieve almost full-gap travel range without incurring electrostatic pull-in. These results are illustrated and validated with transient simulations of the nonlinear closed-loop system

Exploración de los modelos de marcaje–reavistaje–recuperación para estudiar la demografía de los árboles de sabana

Despite their sessile nature, juvenile trees in savannah ecosystems are not always easy to encounter. Here, we evaluate the applicability to plants of the remedy of choice in animal studies: capture–recapture modelling. The plant equivalents, tagging and resighting, were caried outnin 7 censuses, involving 4,145 juvenile trees of 8 dominant savannah species. Using models with joint analysis of live and dead encounters, the resighting probabilities averaged 0.88 ± 0.15 and 0.92 ± 0.10 for seedlings and resprouts respectively; while dead recovery probabilities averaged 0.71 ± 0.25 for all age–classes. An ad hoc method that did not take into account encounter probabilities yielded biased survival estimates compared with estimates obtained using the mark–resighting–recovery approaches. This bias was observed even at high encounter probabilities, and we recommend therefore capture–recapture models where plant encounter is less than one. Finally, survival probabilities estimated by models based only on live or on dead data might both differ and be less accurate than estimates based on combined data. This highlights the advantages of models with joint analysis of live and dead encounters even the value of site fidelity is one.Pese a su naturaleza sésil, los árboles jóvenes no siempre resultan fáciles de hallar en los ecosistemas de sabana. En el presente trabajo se evalua la odelización de captura–recaptura, tan utilizada en estudios de animales, para su aplicación en los estudios de plantas. El equivalente al marcaje y reavistamiento para las plantas, se llevó a cabo a lo largo de siete censos, con un total de 4.145 árboles juveniles de ocho especies de la sabana dominantes. Mediante el empleo de análisis conjuntos de hallazgos de individuos vivos y muertos, las probabilidades de reaviastamiento medias fueron de 0,88 ± 0,15 y 0,92 ± 0,10 para las plántulas y los rebrotes, respectivamente, mientras que el promedio correspondiente a las probabilidades de recuperación de individuos muertos fue de 0,71 ± 0,25 para todas las clases de edad. Un método especialmente disenyado que no tenía en cuenta las probabilidades de recaptura dio unas estimaciones de supervivencia sesgadas, en comparación con las estimas obtenidas utilizando las aproximaciones basadas en el marcaje–reavistamiento–recaptura. Este sesgo aparecía incluso con altas probabilidades de recaptura, por lo que recomendamos los modelos de captura–recaptura en los que la probabilidad de encontarr la planta es menor de uno. Por ultimo, las probabilidades de supervivencia estimadas mediante los modelos basados únicamente en datos de plantas vivas o muertas pueden tanto diferir como ser menos precisas que las estimas basadas en datos combinados. Esto realza las ventajas de los modelos que emplean análisis conjuntos de hallazgos de plantas vivas y muertas, aun cuando el valor de la fidelidad al emplazamiento sea uno

RESOLUTION LIMITS FOR RESONANT MEMS SENSORS BASED ON DISCRETE RELAY FEEDBACK TECHNIQUES

Submitted on behalf of EDA Publishing Association (http://irevues.inist.fr/handle/2042/5920)International audienceThis paper is devoted to the analysis of resonant MEMS sensors based on discrete relay feedback techniques. One drawback of such techniques is that some synchronization usually occurs between the discrete part and the continuous part of the system: this results in sensor responses that are very similar to the curves known as devil's staircases, i.e. the frequency does not vary smoothly with the sensor's input. The main contribution of this paper is a theoretical calculation of the resolution of such systems. The resolutions of two existing resonant MEMS architectures are then calculated and these results are discussed

320g Ionization-Heat Cryogenic Detector for Dark Matter Search in the EDELWEISS Experiment

The EDELWEISS experiment used in 2001 a 320g heat-and-ionization cryogenic Ge detector operated in a low-background environment in the Laboratoire Souterrain de Modane for direct WIMP detection. This detector presents an increase of more than 4 times the mass of previous detectors. Calibrations of this detector are used to determine its energy resolution and fiducial volume, and to optimize the detector design for the 1kg phase of the EDELWEISS-I experiment. Analysis of the calibrations and characteristics of a first series of 320g-detectors are presented.Comment: 4 pages, 3 figure

Linear analysis of the influence of FIR feedback filters on the response of the pulsed digital oscillator

The original publication is available at www.springerlink.comThe objective of this work is to extend the linear analysis of PulsedDigitalOscillators to those topologies having a Finite Impulse Response (FIR) in the feedback loop of the circuit. It will be shown with two specific examples how the overall response of the oscillator can be adjusted to some point by changing the feedback filter, when the resonator presents heavy damping losses. Extensive discrete-time simulations and experimental results obtained with a MEMS cantilever with thermoelectric actuation and piezoresistive position sensing are presented. It will be experimentally shown that the performance of the oscillator is good even below the Nyquist limit

La réaction d ’hémagglutination type Middlebrook-Dubos dans le diagnostic de la tuberculose bovine

La réaction d’hémagglutination type Middlebrook- Dubos, effectuée chez 118 bovins avec des hématies de mouton et la tuberculine soit dite « précipitée » soit I.P. 48 de l ’Institut Pasteur de Paris, a été positive dans 81 p. 100 des cas de tuberculose évolutive, avec des pourcentages variables selon la nature des lésions puisqu’elle a été maxima (100 p. 100) pour les lésions pleuro-pulmonaires, forte (87,3 p. 100) pour les lésions de plusieurs organes ou généralisées, et faible (50 p. 100) pour les lésions ganglio-pulmonaires . Par contre, elle a été le plus souvent négative lorsque les lésions étaient limitées aux ganglions pulmonaires et de type caséo-calcaire. Cette réaction a été très rarement (4,0 p. 100) positive chez des animaux apparemment sains, et toujours d’ailleurs à des taux faibles. Bien que des recherches portant sur de nombreux sérums soient encore nécessaires (pour préciser en particulier la signification des réactions positives chez les bovidés apparemment sains), on peut admettre, semble-t-il, dès maintenant, qu’une réaction nettement positive (5> 1/147) traduit toujours une tuberculose évolutive atteignant plusieurs organes. Elle paraît pouvoir dès maintenant rendre des services pour le diagnostic de la tuberculose et l’étude de la phtisiogenèse chez les bovidés

Confirmation and Keplerian motion of the gap-carving protoplanet HD 169142 b

We present the re-detection of a compact source in the face-on protoplanetary disc surrounding HD 169142, using VLT/SPHERE data in YJH bands. The source is found at a separation of 0.''319 ($\sim$37 au) from the star. Three lines of evidence argue in favour of the signal tracing a protoplanet: (i) it is found in the annular gap separating the two bright rings of the disc, as predicted by theory; (ii) it is moving at the expected Keplerian velocity for an object at $\sim$37 au in the 2015, 2017 and 2019 datasets; (iii) we also detect a spiral-shaped signal whose morphology is consistent with the expected outer spiral wake triggered by a planet in the gap, based on dedicated hydrodynamical simulations of the system. The YJH colours we extracted for the object are consistent with tracing scattered starlight, suggesting that the protoplanet is enshrouded in a significant amount of dust, as expected for a circumplanetary disc or envelope surrounding a gap-clearing Jovian-mass protoplanet.Comment: Accepted for publication in MNRAS Letters. 5 pages, 5 figure