The long-term effects of the micrometeoroid and orbital debris environments on materials used in space

The long-term effects of the orbital debris and micrometeoroid environments on materials that are current candidates for use on space vehicles are discussed. In addition, the limits of laboratory testing to determine these effects are defined and the need for space-based data is delineated. The impact effects discussed are divided into primary and secondary surfaces. Primary surfaces are those that are subject to erosion, pitting, the degradation and delamination of optical coatings, perforation of atomic oxygen erosion barriers, vapor coating of optics and the production of secondary ejecta particles. Secondary surfaces are those that are affected by the result of the perforation of primary surfaces, for example, vapor deposition on electronic components and other sensitive equipment, and the production of fragments with damage potential to internal pressurized elements. The material properties and applications that are required to prevent or lessen the effects described, are defined

Target2 and Cross-border Interbank Payments during the Financial Crisis

Schulden; Finanzmarktkrise; Target Zone; Schuldenkrise; Europäische Wirtschafts- und Währungsunion

Quasi Markovian behavior in mixing maps

We consider the time dependent probability distribution of a coarse grained observable Y whose evolution is governed by a discrete time map. If the map is mixing, the time dependent one-step transition probabilities converge in the long time limit to yield an ergodic stochastic matrix. The stationary distribution of this matrix is identical to the asymptotic distribution of Y under the exact dynamics. The nth time iterate of the baker map is explicitly computed and used to compare the time evolution of the occupation probabilities with those of the approximating Markov chain. The convergence is found to be at least exponentially fast for all rectangular partitions with Lebesgue measure. In particular, uniform rectangles form a Markov partition for which we find exact agreement.Comment: 16 pages, 1 figure, uses elsart.sty, to be published in Physica D Special Issue on Predictability: Quantifying Uncertainty in Models of Complex Phenomen

Hypervelocity impact shield

A hypervelocity impact shield and method for protecting a wall structure, such as a spacecraft wall, from impact with particles of debris having densities of about 2.7 g/cu cm and impact velocities up to 16 km/s are disclosed. The shield comprises a stack of ultra thin sheets of impactor disrupting material supported and arranged by support means in spaced relationship to one another and mounted to cover the wall in a position for intercepting the particles. The sheets are of a number and spacing such that the impacting particle and the resulting particulates of the impacting particle and sheet material are successively impact-shocked to a thermal state of total melt and/or vaporization to a degree as precludes perforation of the wall. The ratio of individual sheet thickness to the theoretical diameter of particles of debris which may be of spherical form is in the range of 0.03 to 0.05. The spacing between adjacent sheets is such that the debris cloud plume of liquid and vapor resulting from an impacting particle penetrating a sheet does not puncture the next adjacent sheet prior to the arrival thereat of fragment particulates of sheet material and the debris particle produced by a previous impact

CESifo Forum Special Issue April 2013: Target Balances and the Crisis in the Euro Area

This paper offers a meticulous description and analysis of the development of the Target balances, with a rich set of new data and detailed information that specialists will treasure and the general public will find illuminating. The last part of the paper, in which the author discusses measures to prevent Target balances from ballooning in the future and includes a comparison of settlement possibilities, is particularly thoughtprovoking and useful. In the US system, balance-of-payment imbalances between commercial banks and, much later, district Feds, were settled for two hundred years using gold and gold certificates; and the US system only recently adopted settlement with marketable securities. In Europe no settlement procedure for Target balances has been introduced to-date. Target balances are merely carried forward on the balance sheets of national central banks from year to year, with interest added to the debt and liability positions that have accumulated between the national central banks. This could imply risks that limit the policy choices of member countries. After all, Moody’s decided to consider downgrading the Netherlands and Germany because of their huge outstanding Target claims. It is high time for the Eurosystem partners to discuss the settlement issue more seriously