Design of a Thermal and Micrometeorite Protection System for an Unmanned Lunar Cargo Lander

The first vehicles to land on the lunar surface during the establishment phase of a lunar base will be unmanned lunar cargo landers. These landers will need to be protected against the hostile lunar environment for six to twelve months until the next manned mission arrives. The lunar environment is characterized by large temperature changes and periodic micrometeorite impacts. An automatically deployable and reconfigurable thermal and micrometeorite protection system was designed for an unmanned lunar cargo lander. The protection system is a lightweight multilayered material consisting of alternating layers of thermal and micrometeorite protection material. The protection system is packaged and stored above the lander common module. After landing, the system is deployed to cover the lander using a system of inflatable struts that are inflated using residual fuel (liquid oxygen) from the fuel tanks. Once the lander is unloaded and the protection system is no longer needed, the protection system is reconfigured as a regolith support blanket for the purpose of burying and protecting the common module, or as a lunar surface garage that can be used to sort and store lunar surface vehicles and equipment. A model showing deployment and reconfiguration of the protection system was also constructed

Entropic Lattice Boltzmann Simulation of the Flow Past Square Cylinder

Minimal Boltzmann kinetic models, such as lattice Boltzmann, are often used as an alternative to the discretization of the Navier-Stokes equations for hydrodynamic simulations. Recently, it was argued that modeling sub-grid scale phenomena at the kinetic level might provide an efficient tool for large scale simulations. Indeed, a particular variant of this approach, known as the entropic lattice Boltzmann method (ELBM), has shown that an efficient coarse-grained simulation of decaying turbulence is possible using these approaches. The present work investigates the efficiency of the entropic lattice Boltzmann in describing flows of engineering interest. In order to do so, we have chosen the flow past a square cylinder, which is a simple model of such flows. We will show that ELBM can quantitatively capture the variation of vortex shedding frequency as a function of Reynolds number in the low as well as the high Reynolds number regime, without any need for explicit sub-grid scale modeling. This extends the previous studies for this set-up, where experimental behavior ranging from $Re\sim O(10)$ to $Re\leq 1000$ were predicted by a single simulation algorithm.Comment: 12 pages, 5 figures, to appear in Int. J. Mod. Phys.

Noncommutative Dynamics of Random Operators

We continue our program of unifying general relativity and quantum mechanics in terms of a noncommutative algebra ${\cal A}$ on a transformation groupoid $\Gamma = E \times G$ where $E$ is the total space of a principal fibre bundle over spacetime, and $G$ a suitable group acting on $\Gamma$. We show that every $a \in {\cal A}$ defines a random operator, and we study the dynamics of such operators. In the noncommutative regime, there is no usual time but, on the strength of the Tomita-Takesaki theorem, there exists a one-parameter group of automorphisms of the algebra ${\cal A}$ which can be used to define a state dependent dynamics; i.e., the pair $({\cal A}, \phi)$, where $\phi$ is a state on ${\cal A}$, is a ``dynamic object''. Only if certain additional conditions are satisfied, the Connes-Nikodym-Radon theorem can be applied and the dependence on $\phi$ disappears. In these cases, the usual unitary quantum mechanical evolution is recovered. We also notice that the same pair $({\cal A}, \phi)$ defines the so-called free probability calculus, as developed by Voiculescu and others, with the state $\phi$ playing the role of the noncommutative probability measure. This shows that in the noncommutative regime dynamics and probability are unified. This also explains probabilistic properties of the usual quantum mechanics.Comment: 13 pages, LaTe

Sind Innovatoren erfolgreicher als Nicht-Innovatoren? Eine empirische Analyse für das Verarbeitende Gewerbe in Deutschland

Innovationen gelten als Triebfeder der wirtschaftlichen Entwicklung und der betrieblichen Wettbewerbsfähigkeit. Von besonderem Interesse sind Produkte, die ein Unternehmen erstmals in den Markt einführt bzw. für die das Unternehmen einen neuen Markt erschließen muss. Diese Innovationen bezeichnet man als Marktneuheiten. Aus ökonomischer Sicht stellt sich die Frage, ob Unternehmen, die solche Marktneuheiten hervorbringen, erfolgreicher sind als nicht innovierende Unternehmen. Als Erfolgsindikatoren lassen sich die Entwicklung der Beschäftigung, des Umsatzes, des Gewinns und der Ertragslage heranziehen. Die zu vergleichenden innovierenden und nicht innovierenden Unternehmen sollten aber in ihren sonstigen betrieblichen Merkmalen (wie der Größe oder Branche) auch tatsächlich miteinander vergleichbar sein. Dies wird mit einem Matching-Verfahren erreicht. Die Ergebnisse der mit dem IAB-Betriebspanel für das Verarbeitende Gewerbe durchgeführten Analyse zeigen, dass sich im Durchschnitt die innovierenden Betriebe in den Neuen Ländern im Vergleich zu nicht innovierenden Betrieben durch einen Vorsprung bei der Entwicklung von Beschäftigung und Umsatz auszeichnen. Dieser Abstand ist bei Betrieben in Ostdeutschland etwas größer als bei Betrieben in den Alten Bundesländern. Mit Blick auf die Produktivitätsentwicklung und die Ertragslage finden sich keine statistisch belastbaren Unterschiede zwischen Innovatoren und Nicht-Innovatoren. Die Ergebnisse stellen die hohe Bedeutung von Innovationen für die wirtschaftliche Entwicklung und Wettbewerbsfähigkeit nicht infrage. Sie liefern aber einen Hinweis darauf, dass – bezogen auf Marktneuheiten – auch nicht innovierende Unternehmen (zumindest mittelfristig) Wege finden, sich in ihrer betrieblichen Performance zu behaupten

Earnings Announcement Premia and the Limits to Arbitrage

We document that earnings announcement-day premia persist beyond the sample period of earlier studies, over different disclosure environments and remain robust to the refinement of using the expected announcement day rather than the actual announcement day. A portfolio of announcing firms yields returns in excess of the corresponding risk. Excluding announcers from a well-diversified portfolio, while reducing the standard deviation of that portfolio, also reduces its Sharpe ratio, indicating that this strategy results in a less favorable risk-return trade-off. Finally, we provide evidence that the premia are dramatically reduced when the announcement risk is reduced through preannouncements. In addition, we document that the continued presence of this premia is likely to result from limits to arbitrage. These findings are consistent with the view that the announcement period returns are likely to represent compensation for announcement risk

Scattering from supramacromolecular structures

We study theoretically the scattering imprint of a number of branched supramacromolecular architectures, namely, polydisperse stars and dendrimeric, hyperbranched structures. We show that polydispersity and nature of branching highly influence the intermediate wavevector region of the scattering structure factor, thus providing insight into the morphology of different aggregates formed in polymer solutions.Comment: 20 pages, 8 figures To appear in PR