Archetypal analysis of galaxy spectra

Archetypal analysis represents each individual member of a set of data vectors as a mixture (a constrained linear combination) of the pure types or archetypes of the data set. The archetypes are themselves required to be mixtures of the data vectors. Archetypal analysis may be particularly useful in analysing data sets comprising galaxy spectra, since each spectrum is, presumably, a superposition of the emission from the various stellar populations, nebular emissions and nuclear activity making up that galaxy, and each of these emission sources corresponds to a potential archetype of the entire data set. We demonstrate archetypal analysis using sets of composite synthetic galaxy spectra, showing that the method promises to be an effective and efficient way to classify spectra. We show that archetypal analysis is robust in the presence of various types of noise.Comment: 6 pages, 5 figures, 1 style-file. Accepted for publication by MNRA

Factors contributing to the ballistocardiographic wave form in healthy middle aged males

Factors contributing to ballistocardiographic waveform in healthy middle aged male

Human factors aspects of control room design: Guidelines and annotated bibliography

A human factors analysis of the workstation design for the Earth Radiation Budget Satellite mission operation room is discussed. The relevance of anthropometry, design rules, environmental design goals, and the social-psychological environment are discussed

The 67 Hz Feature in the Black Hole Candidate GRS 1915+105 as a Possible ``Diskoseismic'' Mode

The Rossi X-ray Timing Explorer (RXTE) has made feasible for the first time the search for high-frequency (~ 100 Hz) periodic features in black hole candidate (BHC) systems. Such a feature, with a 67 Hz frequency, recently has been discovered in the BHC GRS 1915+105 (Morgan, Remillard, & Greiner). This feature is weak (rms variability ~0.3%-1.6%), stable in frequency (to within ~2 Hz) despite appreciable luminosity fluctuations, and narrow (quality factor Q ~ 20). Several of these properties are what one expects for a ``diskoseismic'' g-mode in an accretion disk about a 10.6 M_sun (nonrotating) - 36.3 M_sun (maximally rotating) black hole (if we are observing the fundamental mode frequency). We explore this possibility by considering the expected luminosity modulation, as well as possible excitation and growth mechanisms---including turbulent excitation, damping, and ``negative'' radiation damping. We conclude that a diskoseismic interpretation of the observations is viable.Comment: 4 Pages, Latex (emulateapj.sty included), to Appear in ApJ Letters, Vol. 477, Final Version with Updated Reference

Gas-plasma compressional wave coupling by momentum transfer

Pressure disturbances in a gas-plasma mixed fluid will result in a hybrid response, with magnetosonic plasma waves coupled to acoustic waves in the neutral gas. In the analytical and numerical treatment presented here, we demonstrate the evolution of the total fluid medium response under a variety of conditions, with the gas-plasma linkage achieved by additional coupling terms in the momentum equations of each species. The significance of this treatment lies in the consideration of density perturbations in such fluids: there is no 'pure' mode response, only a collective one in which elements of the characteristics of each component are present. For example, an initially isotropic gas sound wave can trigger an anisotropic magnetic response in the plasma, with the character of each being blended in the global evolution. Hence sound waves do not remain wholly isotropic, and magnetic responses are less constrained by pure magnetoplasma dynamics

Hawkes process as a model of social interactions: a view on video dynamics

We study by computer simulation the "Hawkes process" that was proposed in a recent paper by Crane and Sornette (Proc. Nat. Acad. Sci. USA 105, 15649 (2008)) as a plausible model for the dynamics of YouTube video viewing numbers. We test the claims made there that robust identification is possible for classes of dynamic response following activity bursts. Our simulated timeseries for the Hawkes process indeed fall into the different categories predicted by Crane and Sornette. However the Hawkes process gives a much narrower spread of decay exponents than the YouTube data, suggesting limits to the universality of the Hawkes-based analysis.Comment: Added errors to parameter estimates and further description. IOP style, 13 pages, 5 figure

Optimisation of ITER Nb3Sn CICCs for coupling loss, transverse electromagnetic load and axial thermal contraction

The ITER cable-in-conduit conductors (CICCs) are built up from sub-cable bundles, wound in different stages, which are twisted to counter coupling loss caused by time-changing external magnet fields. The selection of the twist pitch lengths has major implications for the performance of the cable in the case of strain sensitive superconductors, i.e. Nb3Sn, as the electromagnetic and thermal contraction loads are large but also for the heat load from the AC coupling loss. Reduction of the transverse load and warm-up cool-down degradation can be reached by applying longer twist pitches in a particular sequence for the sub-stages, offering a large cable transverse stiffness, adequate axial flexibility and maximum allowed lateral strand support. Analysis of short sample (TF conductor) data reveals that increasing the twist pitch can lead to a gain of the effective axial compressive strain of more than 0.3 % with practically no degradation from bending. For reduction of the coupling loss, specific choices of the cabling twist sequence are needed with the aim to minimize the area of linked strands and bundles that are coupled and form loops with the applied changing magnetic field, instead of simply avoiding longer pitches. In addition we recommend increasing the wrap coverage of the CS conductor from 50 % to at least 70 %. The models predict significant improvement against strain sensitivity and substantial decrease of the AC coupling loss in Nb3Sn CICCs, but also for NbTi CICCs minimization of the coupling loss can be achieved. Although the success of long pitches to transverse load degradation was already demonstrated, the prediction of the combination with low coupling loss needs to be validated by a short sample test.Comment: to be published in Supercond Sci Techno