Apollo experience report: Lunar module structural subsystem

In the Apollo Program, the lunar-orbit rendezvous mode was used for the lunar-landing mission. To accomplish the lunar landing, a lunar module spacecraft was built. A description of the design requirements for the structural subsystem and of the structural configuration and the method of design verification are given. A discussion is presented of several problems encountered and the corrective actions taken during the designing, manufacturing, and testing of the lunar module

Producing Bose condensates using optical lattices

We relate the entropies of ensembles of atoms in optical lattices to atoms in simple traps. We then determine which ensembles of lattice-bound atoms will adiabatically transform into a Bose condensate. This shows a feasible approach to Bose condensation without evaporative cooling.Comment: RevTeX, 5 pages, 5 eps-figure

Coherent and incoherent dynamics in excitonic energy transfer: correlated fluctuations and off-resonance effects

We study the nature of the energy transfer process within a pair of coupled two-level systems (donor and acceptor) subject to interactions with the surrounding environment. Going beyond a standard weak-coupling approach, we derive a master equation within the polaron representation that allows for investigation of both weak and strong system-bath couplings, as well as reliable interpolation between these two limits. With this theory, we are then able to explore both coherent and incoherent regimes of energy transfer within the donor-acceptor pair. We elucidate how the degree of correlation in the donor and acceptor fluctuations, the donor-acceptor energy mismatch, and the range of the environment frequency distribution impact upon the energy transfer dynamics. In the resonant case (no energy mismatch) we describe in detail how a crossover from coherent to incoherent transfer dynamics occurs with increasing temperature [A. Nazir, Phys. Rev. Lett. 103, 146404 (2009)], and we also explore how fluctuation correlations are able to protect coherence in the energy transfer process. We show that a strict crossover criterion is harder to define when off-resonance, though we find qualitatively similar population dynamics to the resonant case with increasing temperature, while the amplitude of coherent population oscillations also becomes suppressed with growing site energy mismatch.Comment: 14 pages, 7 figures, builds upon PRL 103, 146404 (2009) (arXiv:0906.0592). Comments welcome. V2 - Section IV shortened to improve presentation, references updated, new Imperial College affiliation added for A. Nazir. Published versio

Vers l'évaluation des données pariétales fluctuantes avec des méthodes de frontières immergées

International audienceImmersed boundary conditions (IBC) has reached a sufficient level of maturity to allow the simulation of compressible high Reynolds number flows around complex geometries. However, the reconstruction of physical quantities at the wall of geometries introduced using IBC is far from being straightforward. The difficulty to obtain a prediction as accurate as for classical body-fitted approaches originates from the intrinsic mismatch between immersed boundaries and the underlying mesh. To tackle this issue, a novel method to compute global loads and to provide precise wall data in the view of spectral analyses is introduced. First, this method is assessed for the investigation of highly unsteady separating compressible flows of two space launcher afterbody configurations using Zonal Detached Eddy Simulation (ZDES). Then, the results are compared against validated numerical simulations using a classical body-fitted approach. Finally, the present method successfully returns wall quantities with IBC consistent with classical methodologies and without additional time-consuming operations.Les méthodes de frontières immergées ont atteint un niveau suffisant de maturité pour permettre la simulation des écoulements compressibles à haut nombre de Reynolds sur des géométries complexes. Cependant la reconstruction des valeurs pariétales introduites pas une approche de frontières immergées est un problème complexe. La principale difficulté provient de la dissociation intrinsèque à la méthode entre le maillage de fond utilisé durant la simulation et l’objet immergé. Afin de résoudre ce problème, une nouvelle méthode a été développée afin de permettre le calcul des efforts aérodynamiques et de permettre l’analyse spectrale des données pariétales sur une paroi modélisée par une approche de frontières immergées. Cette méthode a été appliquée afin de simuler l’écoulement autour de deux arrière-corps de lanceurs spatiaux en utilisant la Zonal Detached Eddy Simulation (ZDES). Les grandeurs pariétales fluctuantes sur les parois modélisées par une approche de frontières immergées ont été comparées à des calculs obtenus par des méthodes classiques. Les résultats ont montré que l’approche proposée permet d’évaluer les grandeurs pariétales modélisées par des approches de frontières immergées

Reaction of the chick to one atmosphere of oxygen

Experiment to determine chicken reaction to 100 percent oxygen at atmospheric pressur

Embryo development and chick growth in a helium - oxygen atmosphere

Embryo development and chick growth in helium- oxygen atmospher