An evaluation of composite propulsion for single-stage-to-orbit vehicles designed for horizontal take-off

Composite propulsion was analyzed for single-stage-to-orbit vehicles designed for horizontal take-off. Trajectory, geometric, and mass analyses were performed to establish the orbital payload capability of six engines. The results indicated that none of the engines performed adequately to deliver payloads to orbit as analyzed. The single-stage turbine and oxidizer-rich gas generator resulted in a low engine specific impulse, and the performance increment of the ejector subsystem was less than that of a separate rocket system with a high combustion pressure. There was a benefit from incorporating a fan into the engine, and removal of the fan from the airstream during the ramjet mode increased the orbital payload capability

Discriminating between unresolved point sources and "negative" SZ clusters in CMB maps

Clusters of galaxies produce negative features at wavelengths $\lambda > 1.25$ mm in CMB maps, by means of the thermal SZ effect, while point radio sources produce positive peaks. This fact implies that a distribution of unresolved SZ clusters could be detected using the negative asymmetry introduced in the odd-moments of the brightness map (skewness and higher), or in the probability distribution function (PDF) for the fluctuations, once the map has been filtered in order to remove the contribution from primordial CMB fluctuations from large scales. This property provides a consistency check to the recent detections from CBI and BIMA experiments of an excess of power at small angular scales, in order to confirm that they are produced by a distribution of unresolved SZ clusters. However it will require at least 1.5 - 2 times more observing time than detection of corresponding power signal. This approach could also be used with the data of the planned SZ experiments (e.g. ACT, AMI, AMIBA, APEX, 8 m South Pole telescope).Comment: Includes a new section and a new appendix. Typos corrected. Accepted for publication in MNRA

Study and applications of retrodirective and self-adaptive electromagnetic wave controls to a Mars probe First quarterly report

Antenna array studies for future Mars probe

Sampled forms of functional PCA in reproducing kernel Hilbert spaces

We consider the sampling problem for functional PCA (fPCA), where the simplest example is the case of taking time samples of the underlying functional components. More generally, we model the sampling operation as a continuous linear map from $\mathcal{H}$ to $\mathbb{R}^m$, where the functional components to lie in some Hilbert subspace $\mathcal{H}$ of $L^2$, such as a reproducing kernel Hilbert space of smooth functions. This model includes time and frequency sampling as special cases. In contrast to classical approach in fPCA in which access to entire functions is assumed, having a limited number m of functional samples places limitations on the performance of statistical procedures. We study these effects by analyzing the rate of convergence of an M-estimator for the subspace spanned by the leading components in a multi-spiked covariance model. The estimator takes the form of regularized PCA, and hence is computationally attractive. We analyze the behavior of this estimator within a nonasymptotic framework, and provide bounds that hold with high probability as a function of the number of statistical samples n and the number of functional samples m. We also derive lower bounds showing that the rates obtained are minimax optimal.Comment: Published in at http://dx.doi.org/10.1214/12-AOS1033 the Annals of Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical Statistics (http://www.imstat.org