A technique for optimal temperature estimation for modeling sunrise/sunset thermal snap disturbance torque

A predictive temperature estimation technique which can be used to drive a model of the Sunrise/Sunset thermal 'snap' disturbance torque experienced by low Earth orbiting spacecraft is described. The twice per orbit impulsive disturbance torque is attributed to vehicle passage in and out of the Earth's shadow cone (umbra), during which large flexible appendages undergo rapidly changing thermal conditions. Flexible members, in particular solar arrays, experience rapid cooling during umbra entrance (Sunset) and rapid heating during exit (Sunrise). The thermal 'snap' phenomena has been observed during normal on-orbit operations of both the LANDSAT-4 satellite and the Communications Technology Satellite (CTS). Thermal 'snap' has also been predicted to be a dominant source of error for the TOPEX satellite. The fundamental equations used to model the Sunrise/Sunset thermal 'snap' disturbance torque for a typical solar array like structure will be described. For this derivation the array is assumed to be a thin, cantilevered beam. The time varying thermal gradient is shown to be the driving force behind predicting the thermal 'snap' disturbance torque and therefore motivates the need for accurate estimates of temperature. The development of a technique to optimally estimate appendage surface temperature is highlighted. The objective analysis method used is structured on the Gauss-Markov Theorem and provides an optimal temperature estimate at a prescribed location given data from a distributed thermal sensor network. The optimally estimated surface temperatures could then be used to compute the thermal gradient across the body. The estimation technique is demonstrated using a typical satellite solar array

The redshift of the gravitationally lensed radio source PKS1830-211

We report on the spectroscopic identification and the long awaited redshift measurement of the heavily obscured, gravitationally lensed radio source PKS 1830-211, which was first observed as a radio Einstein ring. The NE component of the doubly imaged core is identified, in our infrared spectrum covering the wavelength range 1.5-2.5 microns, as an impressively reddened quasar at z=2.507. Our redshift measurement, together with the recently measured time delay (Lovell et al.), means that we are a step closer to determining the Hubble constant from this lens. Converting the time delay into the Hubble constant by using existing models leads to high values for the Hubble constant. Since the lensing galaxy lies very close to the center of the lensed ring, improving the error bars on the Hubble constant will require not only a more precise time delay measurement, but also very precise astrometry of the whole system.Comment: 11 pages, 2 figures, Accepted ApJ

Hall-Effect for Neutral Atoms

It is shown that polarizable neutral systems can drift in crossed magnetic and electric fileds. The drift velocity is perpendicular to both fields, but contrary to the drif t velocity of a charged particle, it exists only, if fields vary in space or in time. We develop an adiabatic theory of this phenomenon and analyze conditions of its experimental observation. The most proper objects for the observation of this effect are Rydberg atoms. It can be applied for the separation of excited atoms.Comment: RevTex, 4 pages; to be published in Pis'ma v ZhET

BIMA and Keck Imaging of the Radio Ring PKS 1830-211

We discuss BIMA (Berkeley Illinois Maryland Association) data and present new high quality optical and near-IR Keck images of the bright radio ring PKS 1830-211. Applying a powerful new deconvolution algorithm we have been able to identify both images of the radio source. In addition we recover an extended source in the optical, consistent with the expected location of the lensing galaxy. The source counterparts are very red, I-K=7, suggesting strong Galactic absorption with additional absorption by the lensing galaxy at z=0.885, and consistent with the detection of high redshift molecules in the lens.Comment: To be published in the ASP Conference Proceedings, 'Highly Redshifted Radio Lines', Greenbank, W

The Variable Stars and Blue Horizontal Branch of the Metal-Rich Globular Cluster NGC 6441

We present time-series VI photometry of the metal-rich ([Fe/H] = -0.53) globular cluster NGC 6441. Our color-magnitude diagram shows that the extended blue horizontal branch seen in Hubble Space Telescope data exists in the outermost reaches of the cluster. The red clump slopes nearly parallel to the reddening vector. A component of this slope is due to differential reddening, but part is intrinsic. The blue horizontal branch stars are more centrally concentrated than the red clump stars. We have discovered about 50 new variable stars near NGC 6441, among them eight or more RR Lyrae stars which are very probably cluster members. Comprehensive period searches over the range 0.2-1.0 days yielded unusually long periods (0.5-0.9 days) for the fundamental pulsators compared with field RR Lyrae of the same metallicity. Three similar long-period RR Lyrae are known in other metal-rich globulars. With over ten examples in hand, it seems that a distinct sub-class of RR Lyrae is emerging. The observed properties of the horizontal branch stars are in reasonable agreement with recent models which invoke deep mixing to enhance the atmospheric helium abundance, while they conflict with models which assume high initial helium abundance. The light curves of the c-type RR Lyrae seem to have unusually long rise times and sharp minima. Reproducing these light curves in stellar pulsation models may provide another means of constraining the physical variables responsible for the anomalous blue horizontal branch extension and sloped red clump observed in NGC 6441.Comment: 30 pages plus 6 EPS and 6 JPEG figures; uses AAS TeX. Accepted by the Astronomical Journal. Minor changes include computing He abundance, modifications to Figs 1 and 8, and expansion on idea that blue HB stars may be produced in binarie

Surface tension implementation for Gensmac 2D

In the present work we describe a method which allows the incorporation of surface tension into the GENSMAC2D code. This is achieved on two scales. First on the scale of a cell, the surface tension effects are incorporated into the free surface boundary conditions through the computation of the capillary pressure. The required curvature is estimated by fitting a least square circle to the free surface using the tracking particles in the cell and in its close neighbors. On a sub-cell scale, short wavelength perturbations are filtered out using a local 4-point stencil which is mass conservative. An efficient implementation is obtained through a dual representation of the cell data, using both a matrix representation, for ease at identifying neighbouring cells, and also a tree data structure, which permits the representation of specific groups of cells with additional information pertaining to that group. The resulting code is shown to be robust, and to produce accurate results when compared with exact solutions of selected fluid dynamic problems involving surface tension

What children know about the source of their knowledge without reporting it as the source

We argue that, amongst 3- to 5- year-olds, failure to report the source of knowledge recently acquired in answer to “How do you know…?” is due to a specific failure to make a causal inference, in line with source monitoring theory but not fuzzy trace theory. In three Experiments, children (N = 37; 30; 59) identified a hidden toy by seeing, feeling, or by being told, having had two modes of access on each trial, one informative (e.g. seeing a toy identified by colour) and the other uninformative (e.g. being told the toy’s colour by the Experimenter who had only felt it). Children who answered the know question wrongly nevertheless reported accurately who saw and who felt the toy, and what the well-informed player had said. They also realised when the Experimenter’s uninformative access implied their own knowledge was unreliable, suggesting precocious working understanding of knowledge sources

Quality engineering of a traction alternator by robust design

Robust design is an engineering methodology for improving productivity during research and development so that high-quality products can be developed and produced quickly and at low cost. A large electrical company was developing traction alternators for a diesel electrical engine. Customer requirement was to obtain very high efficiency which, in turn, was influenced by several design parameters. The usual approach of the 'design-build-test' cycle was considered time-consuming and costly; it used to take anywhere from 4 months to 1 year before finalizing the product design parameters as it involved physical assembly and also testing. Instead, the authors used Taguchi's parameter design approach. This approach took about 8 weeks to arrive at optimum design parameter values; clearly demonstrating the cutting edge of this methodology over the traditional design-build-test approach. The prototype built and tested accordingly gave satisfactory overall performance, meeting and even exceeding customer requirements

APASS Landolt-Sloan BVgri photometry of RAVE stars. I. Data, effective temperatures and reddenings

We provide APASS photometry in the Landolt BV and Sloan g'r'i' bands for all the 425,743 stars included in the latest 4th RAVE Data Release. The internal accuracy of the APASS photometry of RAVE stars, expressed as error of the mean of data obtained and separately calibrated over a median of 4 distinct observing epochs and distributed between 2009 and 2013, is 0.013, 0.012, 0.012, 0.014 and 0.021 mag for B, V, g', r' and i' band, respectively. The equally high external accuracy of APASS photometry has been verified on secondary Landolt and Sloan photometric standard stars not involved in the APASS calibration process, and on a large body of literature data on field and cluster stars, confirming the absence of offsets and trends. Compared with the Carlsberg Meridian Catalog (CMC-15), APASS astrometry of RAVE stars is accurate to a median value of 0.098 arcsec. Brightness distribution functions for the RAVE stars have been derived in all bands. APASS photometry of RAVE stars, augmented by 2MASS JHK infrared data, has been chi2 fitted to a densely populated synthetic photometric library designed to widely explore in temperature, surface gravity, metallicity and reddening. Resulting Teff and E(B-V), computed over a range of options, are provided and discussed, and will be kept updated in response to future APASS and RAVE data releases. In the process it is found that the reddening caused by an homogeneous slab of dust, extending for 140 pc on either side of the Galactic plane and responsible for E(B-V,poles)=0.036 +/- 0.002 at the galactic poles, is a suitable approximation of the actual reddening encountered at Galactic latitudes |b|>=25 deg.Comment: Astronomical Journal, in press. Resolution of Figures degrated to match arXiv file size limit

Removing non-stationary, non-harmonic external interference from gravitational wave interferometer data

We describe a procedure to identify and remove a class of non-stationary and non-harmonic interference lines from gravitational wave interferometer data. These lines appear to be associated with the external electricity main supply, but their amplitudes are non-stationary and they do not appear at harmonics of the fundamental supply frequency. We find an empirical model able to represent coherently all the non-harmonic lines we have found in the power spectrum, in terms of an assumed reference signal of the primary supply input signal. If this signal is not available then it can be reconstructed from the same data by making use of the coherent line removal algorithm that we have described elsewhere. All these lines are broadened by frequency changes of the supply signal, and they corrupt significant frequency ranges of the power spectrum. The physical process that generates this interference is so far unknown, but it is highly non-linear and non-stationary. Using our model, we cancel the interference in the time domain by an adaptive procedure that should work regardless of the source of the primary interference. We have applied the method to laser interferometer data from the Glasgow prototype detector, where all the features we describe in this paper were observed. The algorithm has been tuned in such a way that the entire series of wide lines corresponding to the electrical interference are removed, leaving the spectrum clean enough to detect signals previously masked by them. Single-line signals buried in the interference can be recovered with at least 75 % of their original signal amplitude.Comment: 14 pages, 5 figures, Revtex, psfi