Nutation Damper System

The Nutation Damper System is a three function mechanism designed for the Galileo Spacecraft, a spin stabilized deep-space probe to Jupiter. By damping the movement of a large deployable science boom acting as an outboard pendulum, the nutation damper rapidly stabilizes the spacecraft from dynamic irregularities. The system includes the boom deployment device and the ultra-low friction boom hinge. This paper describes the mechanism, the degree to which friction, stiction and lost motion have been eliminated, and the unique test methods that allow its performance to be measured

"Explaining the September 1992 ERM Crisis: The Maastricht Bargain and Domestic Politics in Germany, France and Great Britain"

At the time of the September 1992 crisis, the conventional wisdom held in the ERM was due to an unfortunate contuence of exceptional circumstances -- the shock of German reunification, a debt-driven recession in Britain, and the uncertainties caused by the Danish and French referenda on Maastricht. This paper points to systemic factors at both the EC and domestic levels in explaining the September crisis. At the Community level, it is argued that the ERM was the victim of an underlying structural flaw in the Maastricht 3-stage plan for EMU. Intergovemmental bargaining, reflecting the differing national preferences of Germany and France in particular, produced an untenable compromise with potentially chaotic consequences: the matching of demanding economic convergence criteria with a strict timetable for their fulfillment, upon commencement of Stage II of the EMU process set for January 1994. Far from being epiphenomenal, this bargain was only the latest manifestation of an ongoing debate between "economist" and monetarist" approaches to monetary integration, tracing back to the early 1970s. and I argue that the "framing effects" of the Stage II criteria fundamentally altered the nature of economic discourse at Stage I, beginning in 1990. Specific reference numbers for debt ratios and relative and interest rate targets emphasized economic divergence in countries with clearly overvalued currencies, and invited markets to test the strength of govemments' political commitments to their exchange rate pegs. The second component of my explanation of the September crisis lies at the domestic level. Even though strict convergence criteria and timetables provided a severe test of the credibility of members' European commitments, it was not a foregone conclusion that the Maastricht bargain would result in turbulence on the currency markets. A margin of maneuver was left to the member governments, through the demonstration of a willingness to take painful measures, such as fiscal and wage restraint or timely interest rate hikes, to defend the ERM commitment

Synchronization of interconnected networks: the role of connector nodes

In this Letter we identify the general rules that determine the synchronization properties of interconnected networks. We study analytically, numerically and experimentally how the degree of the nodes through which two networks are connected influences the ability of the whole system to synchronize. We show that connecting the high-degree (low-degree) nodes of each network turns out to be the most (least) effective strategy to achieve synchronization. We find the functional relation between synchronizability and size for a given network-of-networks, and report the existence of the optimal connector link weights for the different interconnection strategies. Finally, we perform an electronic experiment with two coupled star networks and conclude that the analytical results are indeed valid in the presence of noise and parameter mismatches.Comment: Accepted for publication in Physical Review Letters. Main text: 5 pages, 4 figures. Supplemental material: 8 pages, 3 figure

The structure of the ICM from High Resolution SPH simulations

We present results from a set of high (512^3 effective resolution), and ultra-high (1024^3) SPH adiabatic cosmological simulations of cluster formation aimed at studying the internal structure of the intracluster medium (ICM). We derive a self-consistent analytical model of the structure of the intracluster medium (ICM). We discuss the radial structure and scaling relations expected from purely gravitational collapse, and show that the choice of a particular halo model can have important consequences on the interpretation of observational data. The validity of the approximations of hydrostatic equilibrium and a polytropic equation of state are checked against results of our simulations. The properties of the ICM are fully specified when a 'universal' profile is assumed for either the dark or the baryonic component. We also show the first results from an unprecedented large-scale simulation of 500 Mpc/h and 2 times 512^3 gas and dark matter particles. This experiment will make possible a detailed study of the large-scale distribution of clusters as a function of their X-ray properties.Comment: 5 pages, 3 figures, to appear in the Proceedings of IAU Colloquium 195: "Outskirts of Galaxy Clusters: intense life in the suburbs", Torino Italy, March 200

Galaxy clustering with photometric surveys using PDF redshift information

Photometric surveys produce large-area maps of the galaxy distribution, but with less accurate redshift information than is obtained from spectroscopic methods. Modern photometric redshift (photo-z) algorithms use galaxy magnitudes, or colors, that are obtained through multi-band imaging to produce a probability density function (PDF) for each galaxy in the map. We used simulated data to study the effect of using different photo-z estimators to assign galaxies to redshift bins in order to compare their effects on angular clustering and galaxy bias measurements. We found that if we use the entire PDF, rather than a single-point (mean or mode) estimate, the deviations are less biased, especially when using narrow redshift bins. When the redshift bin widths are $\Delta z=0.1$, the use of the entire PDF reduces the typical measurement bias from 5%, when using single point estimates, to 3%.Comment: Matches the MNRAS published version. 19 pages, 19 Figure

Connecting density fluctuations and Kirkwood-Buff integrals for finite-size systems

Kirkwood-Buff integrals (KBI) connect the microscopic structure and thermodynamic properties of liquid solutions. KBI are defined in the grand canonical ensemble and evaluated assuming the thermodynamic limit (TL). In order to reconcile analytical and numerical approaches, finite-size KBI have been proposed in the literature, resulting in two strategies to obtain their TL values from computer simulations. (i) The spatial block-analysis method in which the simulation box is divided into subdomains of volume $V$ to compute fluctuations of the number of particles. (ii) A direct integration method where a corrected radial distribution function and a kernel that accounts for the geometry of the integration subvolumes are combined to obtain KBI as a function of $V$. In this work, we propose a method that connects both strategies into a single framework. We start from the definition of finite-size KBI, including the integration subdomain and an asymptotic correction to the radial distribution function, and solve them in Fourier space where periodic boundary conditions are trivially introduced. The limit $q\to 0$, equivalent to the value of the KBI in the TL, is obtained via the spatial block-analysis method. When compared to the latter, our approach gives nearly identical results for all values of $V$. Moreover, all finite-size effect contributions (ensemble, finite-integration domains and periodic boundary conditions) are easily identifiable in the calculation. This feature allows us to analyse finite-size effects independently and extrapolate the results of a single simulation to different box sizes. To validate our approach, we investigate prototypical systems, including SPC/E water and aqueous urea mixtures