12,469 research outputs found

    An analysis of I/O efficient order-statistic-based techniques for noise power estimation in the HRMS sky survey's operational system

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    Noise power estimation in the High-Resolution Microwave Survey (HRMS) sky survey element is considered as an example of a constant false alarm rate (CFAR) signal detection problem. Order-statistic-based noise power estimators for CFAR detection are considered in terms of required estimator accuracy and estimator dynamic range. By limiting the dynamic range of the value to be estimated, the performance of an order-statistic estimator can be achieved by simpler techniques requiring only a single pass of the data. Simple threshold-and-count techniques are examined, and it is shown how several parallel threshold-and-count estimation devices can be used to expand the dynamic range to meet HRMS system requirements with minimal hardware complexity. An input/output (I/O) efficient limited-precision order-statistic estimator with wide but limited dynamic range is also examined

    Shaped Pupil Lyot Coronagraphs: High-Contrast Solutions for Restricted Focal Planes

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    Coronagraphs of the apodized pupil and shaped pupil varieties use the Fraunhofer diffraction properties of amplitude masks to create regions of high contrast in the vicinity of a target star. Here we present a hybrid coronagraph architecture in which a binary, hard-edged shaped pupil mask replaces the gray, smooth apodizer of the apodized pupil Lyot coronagraph (APLC). For any contrast and bandwidth goal in this configuration, as long as the prescribed region of contrast is restricted to a finite area in the image, a shaped pupil is the apodizer with the highest transmission. We relate the starlight cancellation mechanism to that of the conventional APLC. We introduce a new class of solutions in which the amplitude profile of the Lyot stop, instead of being fixed as a padded replica of the telescope aperture, is jointly optimized with the apodizer. Finally, we describe shaped pupil Lyot coronagraph (SPLC) designs for the baseline architecture of the Wide-Field Infrared Survey Telescope-Astrophysics Focused Telescope Assets (WFIRST-AFTA) coronagraph. These SPLCs help to enable two scientific objectives of the WFIRST-AFTA mission: (1) broadband spectroscopy to characterize exoplanet atmospheres in reflected starlight and (2) debris disk imaging.Comment: 41 pages, 15 figures; published in the JATIS special section on WFIRST-AFTA coronagraph

    Searching Gravitational Waves from Pulsars, Using Laser Beam Interferometers

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    We use recent population synthesis results to investigate the distribution of pulsars in the frequency space, having a gravitational strain high enough to be detected by the future generations of laser beam interferometers. We find that until detectors become able to recover the entire population, the frequency distribution of the 'detectable' population will be very dependent on the detector noise curve. Assuming a mean equatorial deformation ϵ=106\epsilon =10^{-6}, the optimal frequency is around 450 Hz for interferometers of the first generation (LIGO or VIRGO) and shifts toward 85 Hz for advanced detectors. An interesting result for future detection stategies is the significant narrowing of the distribution when improving the sensitivity: with an advanced detector, it is possible to have 90% of detection probability while exploring less than 20% of the parameter space (7.5% in the case of ϵ=105\epsilon =10^{-5}). In addition, we show that in most cases the spindown of 'detectable' pulsars represents a period shift of less than a tens of nanoseconds after one year of observation, making them easier to follow in the frequency space.Comment: 5 pages, 3 figures accepted for publication in Astronomy & Astrophysic

    A Typology of Youth Participation and Empowerment for Child and Adolescent Health Promotion

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    Research suggests that increasing egalitarian relations between young people and adults is optimal for healthy development; however, the empirical assessment of shared control in youth–adult partnerships is emerging, and the field still requires careful observation, identification, categorization and labeling. Thus, our objective is to offer a conceptual typology that identifies degrees of youth–adult participation while considering the development potential within each type. We use an empowerment framework, rooted in evidence‐based findings, to identify five types of youth participation: (1) Vessel, (2) Symbolic, (3) Pluralistic, (4) Independent and (5) Autonomous. The typology is constructed as a heuristic device to provide researchers, practitioners and policy‐makers with a common language for articulating degrees of youth participation for optimal child and adolescent health promotion.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/117056/1/ajcp9330.pd

    Overlapping-gate buried-channel charge-coupled devices

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    In this letter the advantages of the overlapping-gate buried-channel charged-coupled devices over the 3-phase metal-gate and resistive-gate buried-channel c.c.d. are discussed and pertinent design considerations for the overlapping-gate c.c.d.s are presented

    GaAs Quantum Dot Thermometry Using Direct Transport and Charge Sensing

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    We present measurements of the electron temperature using gate defined quantum dots formed in a GaAs 2D electron gas in both direct transport and charge sensing mode. Decent agreement with the refrigerator temperature was observed over a broad range of temperatures down to 10 mK. Upon cooling nuclear demagnetization stages integrated into the sample wires below 1 mK, the device electron temperature saturates, remaining close to 10 mK. The extreme sensitivity of the thermometer to its environment as well as electronic noise complicates temperature measurements but could potentially provide further insight into the device characteristics. We discuss thermal coupling mechanisms, address possible reasons for the temperature saturation and delineate the prospects of further reducing the device electron temperature.Comment: 8 pages, 3 (color) figure

    The role of spatial and temporal radiation deposition in inertial fusion chambers: the case of HiPER¿

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    The first wall armour for the reactor chamber of HiPER will have to face short energy pulses of 5 to 20 MJ mostly in the form of x-rays and charged particles at a repetition rate of 5–10 Hz. Armour material and chamber dimensions have to be chosen to avoid/minimize damage to the chamber, ensuring the proper functioning of the facility during its planned lifetime. The maximum energy fluence that the armour can withstand without risk of failure, is determined by temporal and spatial deposition of the radiation energy inside the material. In this paper, simulations on the thermal effect of the radiation–armour interaction are carried out with an increasing definition of the temporal and spatial deposition of energy to prove their influence on the final results. These calculations will lead us to present the first values of the thermo-mechanical behaviour of the tungsten armour designed for the HiPER project under a shock ignition target of 48 MJ. The results will show that only the crossing of the plasticity limit in the first few micrometres might be a threat after thousands of shots for the survivability of the armour

    Community and Clinical Epidemiology of Borderline Personality Disorder

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    Several studies of the prevalence of Borderline Personality Disorder (BPD) in community and clinical settings have been carried out to date. Although results vary according to sampling method and assessment method, median point prevalence of BPD is roughly 1%, with higher or lower rates in certain community subpopulations. In clinical settings, BPD prevalence is around 10-12% in outpatient psychiatric clinics and 20-22% among inpatient clinics. Further research is needed to identify the prevalence and correlates of BPD in other clinical settings (e.g., primary care) and to investigate the impact of demographic variables on BPD prevalence
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