Design of the Annular Suspension and Pointing System (ASPS) (including design addendum)

The Annular Suspension and Pointing System is an experiment pointing mount designed for extremely precise 3 axis orientation of shuttle experiments. It utilizes actively controlled magnetic bearing to provide noncontacting vernier pointing and translational isolation of the experiment. The design of the system is presented and analyzed

Spacetime Metrology with LISA Pathfinder

LISA is the proposed ESA-NASA gravitational wave detector in the 0.1 mHz - 0.1 Hz band. LISA Pathfinder is the down-scaled version of a single LISA arm. The arm -- named Doppler link -- can be treated as a differential accelerometer, measuring the relative acceleration between test masses. LISA Pathfinder -- the in-flight test of the LISA instrumentation -- is currently in the final implementation and planned to be launched in 2014. It will set stringent constraints on the ability to put test masses in geodesic motion to within the required differential acceleration of 3\times10^{-14} m s^{-2} Hz^{-1/2} and track their relative motion to within the required differential displacement measurement noise of 9\times10^{-12} m Hz^{-1/2}, around 1 mHz. Given the scientific objectives, it will carry out -- for the first time with such high accuracy required for gravitational wave detection -- the science of spacetime metrology, in which the Doppler link between two free-falling test masses measures the curvature. This thesis contains a novel approach to the calculation of the Doppler response to gravitational waves. It shows that the parallel transport of 4-vectors records the history of gravitational wave signals. In practice, the Doppler link is implemented with 4 bodies in LISA and 3 bodies in LISA Pathfinder. To compensate for noise sources a control logic is implemented during the measurement. The closed-loop dynamics of LISA Pathfinder can be condensed into operators acting on the motion coordinates, handling the couplings, as well as the cross-talks. The scope of system identification is the optimal calibration of the instrument. This thesis describes some data analysis procedures applied to synthetic experiments and shows the relevance of system identification for the success of LISA Pathfinder in demonstrating the principles of spacetime metrology for all future space-based missions.Comment: PhD thesis defended at University of Trento on 26th March 2012. Advisors: Stefano Vitale, Mauro Hueller. Committee: Eugenio Coccia (Univ. of Rome, Tor Vergata), Philippe Jetzer (Univ. of Z\"urich), Eric Plagnol (APC-CNRS, Paris), Rita Dolesi (Univ. Of Trento

Entire domain basis function expansion of the differential surface admittance for efficient broadband characterization of lossy interconnects

This article presents a full-wave method to characterize lossy conductors in an interconnect setting. To this end, a novel and accurate differential surface admittance operator for cuboids based on entire domain basis functions is formulated. By combining this new operator with the augmented electric field integral equation, a comprehensive broadband characterization is obtained. Compared with the state of the art in differential surface admittance operator modeling, we prove the accuracy and improved speed of the novel formulation. Additional examples support these conclusions by comparing the results with commerical software tools and with measurements

Ultrasonic guided waves in composite plates: a study of interface bond condition and material properties determination with broadband focused air-coupled ultrasounds

This work is focused on two important aspects of the study of the composite materials: characterization of interface bonding in layered composites and evaluation of elastic material properties in air-coupled experiments.;The characterization of interface condition in a layered composite is critical to understand the behavior of the material under various stress situations. A closed disbond, alternatively known as zero-volume disbond or kissing-disbond (KSD) is difficult to detection by conventional normal-incidence ultrasonic nondestructive evaluation (NDE) methods. Such undetected defect may be dangerous because it can produce a significant decrease in structural integrity or lead to a catastrophic failure under certain loading conditions. We have successfully demonstrated a new technique for KSD detection in carried-to-completion experiments involving various artificially created defects.;The dependence of the modes of the propagating wave in a plate on the elastic material properties has motivated us to develop a method suitable for rapid non-contact reconstruction of the guided waves spectra. To overcome the weak and inefficient generation of ultrasonic waves in air of conventional transducers and to achieve the desired wide angular spread of the acoustic beam in air, we employed capacitive foil transducers and designed focusing devices. Measurements of the acoustic pressure profile of the transducers have been performed in both planar and focused configurations and compared with our computationally efficient received voltage model.;We exploited our custom broadband focused air-coupled system and a synthetic aperture scan technique to produce, in one line scan with only one incident angle, an almost complete spectrum of the Rayleigh-Lamb waves of various engineering materials subject to a 700-kHz frequency and 16° angular bandwidth limitation of the transducers. A pulse-compression method along with a fast data acquisition and processing capability allowed us to perform rapid reconstruction and evaluation of the guided waves spectra. Tests of our method on numerous materials showed excellent agreement with theoretical predictions.*;*This dissertation is a compound document (contains both a paper copy and a CD as part of the dissertation). The CD requires the following system requirements: Adobe Acrobat

Simulation of 3D periodic piezoelectric transducers radiating in layered media using Finite Element/Boundary element Analysis

Abstract. This paper is devoted to the description of a mixed finite element/boundary element analysis for the simulation of any periodic transducer radiating in any combination of solid and fluids assuming flat interfaces and linear operation regime. The theoretical developments required in that purpose are described and different examples of transducers are considered to demonstrate the interest of the proposed approach. 1