Space station integrated propulsion and fluid systems study

The program study was performed in two tasks: Task 1 addressed propulsion systems and Task 2 addressed all fluid systems associated with the Space Station elements, which also included propulsion and pressurant systems. Program results indicated a substantial reduction in life cycle costs through integrating the oxygen/hydrogen propulsion system with the environmental control and life support system, and through supplying nitrogen in a cryogenic gaseous supercritical or subcritical liquid state. A water sensitivity analysis showed that increasing the food water content would substantially increase the amount of water available for propulsion use and in all cases, the implementation of the BOSCH CO2 reduction process would reduce overall life cycle costs to the station and minimize risk. An investigation of fluid systems and associated requirements revealed a delicate balance between the individual propulsion and fluid systems across work packages and a strong interdependence between all other fluid systems

A Spectral Algorithm with Additive Clustering for the Recovery of Overlapping Communities in Networks

This paper presents a novel spectral algorithm with additive clustering designed to identify overlapping communities in networks. The algorithm is based on geometric properties of the spectrum of the expected adjacency matrix in a random graph model that we call stochastic blockmodel with overlap (SBMO). An adaptive version of the algorithm, that does not require the knowledge of the number of hidden communities, is proved to be consistent under the SBMO when the degrees in the graph are (slightly more than) logarithmic. The algorithm is shown to perform well on simulated data and on real-world graphs with known overlapping communities.Comment: Journal of Theoretical Computer Science (TCS), Elsevier, A Para\^itr

Mojave remote sensing field experiment

The Mojave Remote Sensing Field Experiment (MFE), conducted in June 1988, involved acquisition of Thermal Infrared Multispectral Scanner (TIMS); C, L, and P-band polarimetric radar (AIRSAR) data; and simultaneous field observations at the Pisgah and Cima volcanic fields, and Lavic and Silver Lake Playas, Mojave Desert, California. A LANDSAT Thematic Mapper (TM) scene is also included in the MFE archive. TM-based reflectance and TIMS-based emissivity surface spectra were extracted for selected surfaces. Radiative transfer procedures were used to model the atmosphere and surface simultaneously, with the constraint that the spectra must be consistent with field-based spectral observations. AIRSAR data were calibrated to backscatter cross sections using corner reflectors deployed at target sites. Analyses of MFE data focus on extraction of reflectance, emissivity, and cross section for lava flows of various ages and degradation states. Results have relevance for the evolution of volcanic plains on Venus and Mars

Asymmetric Induction in Intramolecular [2 + 2]-Photocycloadditions of 1,3-Disubstituted Allenes with Enones and Enoates

Irradiation of optically active allenes (89-92% ee) appended to enones and enoates affords alkylidenecyclobutane photoadducts with high levels of asymmetric induction (83-100%) derived exclusively from the allene fragment. The substrates studied include allenes tethered to enones such as 1,3-cyclohexanedionea nd 1,3-cyclopentanedione, as well as allenes tethered to functionalized coumarins. The enantiomer ratios of the photoadducts were quantified by derivatization of the products as the corresponding Mosher MTPA esters and analysis by ^1H NMR spectroscopy. The exo-methylenecyclobutanes obtained upon irradiation of allene-mumarins are isolated as single olefin diastereomers. Irradiation of a coumarin tethered at C(5) with an optically active allene affords an alkynyl-substituted oxepane with complete asymmetric induction

Measuring Relations Between Concepts In Conceptual Spaces

The highly influential framework of conceptual spaces provides a geometric way of representing knowledge. Instances are represented by points in a high-dimensional space and concepts are represented by regions in this space. Our recent mathematical formalization of this framework is capable of representing correlations between different domains in a geometric way. In this paper, we extend our formalization by providing quantitative mathematical definitions for the notions of concept size, subsethood, implication, similarity, and betweenness. This considerably increases the representational power of our formalization by introducing measurable ways of describing relations between concepts.Comment: Accepted at SGAI 2017 (http://www.bcs-sgai.org/ai2017/). The final publication is available at Springer via https://doi.org/10.1007/978-3-319-71078-5_7. arXiv admin note: substantial text overlap with arXiv:1707.05165, arXiv:1706.0636

The architectures of media power: editing, the newsroom, and urban public space

This paper considers the relation of the newsroom and the city as a lens into the more general relation of production spaces and mediated publics. Leading theoretically from Lee and LiPuma’s (2002) notion of ‘cultures of circulation’, and drawing on an ethnography of the Toronto Star, the paper focuses on how media forms circulate and are enacted through particular practices and material settings. With its attention to the urban milieus and orientations of media organizations, this paper exhibits both affinities with but also differences to current interests in the urban architectures of media, which describe and theorize how media get ‘built into’ the urban experience more generally. In looking at editing practices situated in the newsroom, an emphasis is placed on the phenomenological appearance of media forms both as objects for material assembly as well as more abstracted subjects of reflexivity, anticipation and purposiveness. Although this is explored with detailed attention to the settings of the newsroom and the city, the paper seeks to also provide insight into the more general question of how publicness is material shaped and sited

Metal-to-insulator transition and magnetic ordering in CaRu_{1-x}Cu_xO_3

CaRuO_3 is perovskite with an orthorhombic distortion and is believed to be close to magnetic ordering. Magnetic studies of single crystal and polycrystalline CaRu_{1-x}Cu_xO_3 (0\le x \le 15 at.%Cu) reveal that spin-glass-like transition develops for x\le 7 at.%Cu and obtained value for effective magnetic moment p_{eff}=3.55 mu_B for x=5 at.% Cu, single crystal, indicates presence of Ru^{5+}. At higher Cu concentrations more complex magnetic behaviors are observed. Electrical resistivity measured on polycrystalline samples shows metal-to-insulator transition (MIT) at 51 K for only 2 at.% Cu. Charge compensation, which is assumed to be present upon Cu^{2+/3+} substitution, induces appearance of Ru^{5+} and/or creation of oxygen vacancies in crystal structure. Since the observed changes in physical properties are completely attributable to the charge compensation, they cannot be related to behaviors of pure compound where no such mechanism is present. This study provides the criterion for "good" chemical probes for studying Ru-based perovskites.Comment: 12 pages, 7 figure

Mean-Field Theory for Spin Ladders Using Angular-Momentum Coupled Bases

We study properties of two-leg Heisenberg spin ladders in a mean-field approximation using a variety of angular-momentum coupled bases. The mean-field theory proposed by Gopalan, Rice, and Sigrist, which uses a rung basis, assumes that the mean-field ground state consists of a condensate of spin-singlets along the rungs of the ladder. We generalize this approach to larger angular-momentum coupled bases which incorporate---by their mere definition---a substantial fraction of the important short-range structure of these materials. In these bases the mean-field ground-state remains a condensate of spin singlet---but now with each involving a larger fraction of the spins in the ladder. As expected, the ``purity'' of the ground-state, as judged by the condensate fraction, increases with the size of the elementary block defining the basis. Moreover, the coupling to quasiparticle excitations becomes weaker as the size of the elementary block increases. Thus, the weak-coupling limit of the theory becomes an accurate representation of the underlying mean-field dynamics. We illustrate the method by computing static and dynamic properties of two-leg ladders in the various angular-momentum coupled bases.Comment: 28 pages with 8 figure

The Composition of M-type asteroids II: Synthesis of spectroscopic and radar observations

This work updates and expands on results of our long-term radar-driven observational campaign of main-belt asteroids (MBAs) focused on Bus-DeMeo Xc- and Xk-type objects (Tholen X and M class asteroids) using the Arecibo radar and NASA Infrared Telescope Facilities (Ockert-Bell et al. 2008; 2010; Shepard et al. 2008; 2010). Eighteen of our targets were near-simultaneously observed with radar and those observations are described in Shepard et al. (2010). We combine our near-infrared data with available visible wavelength data for a more complete compositional analysis of our targets. Compositional evidence is derived from our target asteroid spectra using two different methods, a \c{hi}2 search for spectral matches in the RELAB database and parametric comparisons with meteorites. We present four new methods of parametric comparison, including discriminant analysis. Discriminant analysis identifies meteorite type with 85% accuracy. This paper synthesizes the results of these two analog search algorithms and reconciles those results with analogs suggested from radar data (Shepard et al. 2010). We have observed 29 asteroids, 18 in conjunction with radar observations. For eighteen out of twenty-nine objects observed (62%) our compositional predictions are consistent over two or more methods applied. We find that for our Xc and Xk targets the best fit is an iron meteorite for 34% of the samples. Enstatite Chondrites were best fits for 6 of our targets (21%). Stony-iron meteorites were best fits for 2 of our targets (7%). A discriminant analysis suggests that asteroids with no absorption band can be compared to iron meteorites and asteroids with both a 0.9 and 1.9 {\mu}m absorption band can be compared to stony-iron meteorites.Comment: 30 pages, 5 figures, 10 table