1,536,648 research outputs found
Ray Maddison photograph, Ray Madison's swings, 1975.
No full textRay Maddison's Swings photographed 1975. Location given as Teeside
Time Resolved Two Dimensional X-Ray Densitometry of a Two Phase Flow Downstream of a Ventilated Cavity
No full textTo measure the void fraction distribution in gas-liquid flows, a two-dimensional x-ray densitometry system was developed. This system is capable of acquiring a two-dimensional projection with a 225 cm2 area of measurement through 21 cm of water. The images can be acquired at rates on the order of 1 kHz. Common sources of error in x-ray imaging, such as x-ray scatter, image distortion, veiling glare, and beam hardening were considered, and mitigated. The measured average void fraction was compared success fully to that of a phantom target and found to be within 1%. To evaluate the performance of the new system, the flow in and downstream of a ventilated nominally two-dimensional partial cavity was investigated and compared to measurements from dual tip fiber optical probes and high speed video. The measurements were found to have satisfactory agreement for void fractions above 5% of the selected void fraction measurement range.Office of Naval Research under grant N00014-10-1-097
Ray Maddison photograph, Carrington Park Terrace, 1982.
No full textRay Maddison's Juvenile Swing Boats photographed 31 May 1982. Location given as Carrington Park Terrace
Photodetectors for Gamma-Ray Astronomy
No full textPhotodetectors are widely employed as optical receivers to convert light into electrical signals in many applications ranging from communications to electronics, medicine, automotive, and transport. In gamma-ray astronomy, photodetectors are extensively used by space experiments to detect and measure the energy of X-rays and gamma rays (from a few keV to hundreds of GeV) interacting in various scintillator materials. Moreover, they are required in the cameras of Imaging Atmospheric Cherenkov Telescopes (IACTs) on the ground to measure very short light pulses produced by the interaction of high-energy gamma rays in the atmosphere down to a level of several photons. In this chapter, we introduce representative photodetectors used for high-energy astronomy, including photomultiplier tubes (PMTs), solid-state (semiconductor) photodetectors, with particular emphasis on silicon photomultipliers (SiPMs), and silicon drift detectors (SDDs). We address their basic properties and highlight past, present, and future applications, with particular emphasis to their employment in many small CubeSat missions devoted to the study of the highenergy, multimessenger sky
Active X-ray optics for the next generation of X-ray space telescopes
No full textDescribed within is the design, manufacture, metrology and X-ray testing of an active X-ray
prototype intended for the next generation of X-ray telescopes. One of the challenges faced by
the X-ray telescope community is how to combine high resolution and high sensitivity into one
system, as weight limitations place constraints on the optics that can be launched. Therefore the
mandate of the active X-ray prototype is to provide high sensitivity through the ability of the optics
to be nested and to deliver high angular resolution through the active control of the optic’s form.
Piezoelectric unimorph actuators provide the active component: it is intended that they will correct
for figure errors within the optic and therefore increase the angular resolution capability.
The prototype’s design is based upon an ellipsoidal segment which provides point-to-point
focussing of an X-ray source. The prototype itself is composed of an electroformed nickel optic
where the non-reflective surface is populated with 30 piezoelectric actuators and it is the production
of the prototype that is the core of the presented research. Metrology of the actuators’ influence
functions is presented and highlight the prototype’s ability to deform its optic surface by microns.
In addition, the measured influence functions are compared against finite element models and a
distinct similarity between the functions is observed.
The prototype was tested at an X-ray beamline facility in November 2008 and the results
showed the prototype’s ability to correct the optic to achieve an improved angular resolution: from
0.786 arc-minutes to 0.686 arc-minutes in terms of full width half maximum. Finally, difficulties
in the manufacture of the prototype and X-ray testing shall be presented alongside future work in
conclusion to this thesis
Variations on the Author
No full text“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
[Affidavit In Any Fact by Bonnie Ray Williams #2]
No full textHandwritten affidavit by Bonnie Ray Williams, an employee at the Texas School Book Depository, who worked on the sixth floor on November 22nd. At lunchtime Williams went to the fifth floor with a man named Hank where they saw the President pass and heard two shots, which sounded as though they came from just above them. Williams saw Lee Harvey Oswald when he arrived at the building at 8 AM and recognized him when he was brought into the Homicide Bureau
[Affidavit In Any Fact by Bonnie Ray Williams #3]
No full textHandwritten affidavit by Bonnie Ray Williams, an employee at the Texas School Book Depository, who worked on the sixth floor on November 22nd. At lunchtime Bonnie went to the fifth floor with a man named Hank where they saw the President pass and heard two shots, which sounded as though they came from just above them. Bonnie saw Lee Harvey Oswald when he arrived at the building at 8 AM and recognized him when he was brought into the Homicide Bureau
A 2 h periodic variation in the low-mass X-ray binary Ser X-1
No full textSpectroscopy of the low-mass X-ray binary Ser X-1 using the Gran Telescopio Canarias have revealed a ?2 h periodic variability that is present in the three strongest emission lines. We tentatively interpret this variability as due to orbital motion, making it the first indication of the orbital period of Ser X-1. Together with the fact that the emission lines are remarkably narrow, but still resolved, we show that a main-sequence K dwarf together with a canonical 1.4 M? neutron star gives a good description of the system. In this scenario, the most likely place for the emission lines to arise is the accretion disc, instead of a localized region in the binary (such as the irradiated surface or the stream-impact point), and their narrowness is due instead to the low inclination (?10°) of Ser X-1
Simulations of X-ray bursts and superbursts
No full textObservations of neutron star in binary systems provide powerful constrains on the physics at the surface of neutron stars. During the accretion of matter from the companion star, periodic nuclear explosion are triggered in the outer layers of the neutron star, increasing the luminosity during a time range of a few minutes. Rarely, one can also detect day-long explosions in accreting binary systems. The nature of those two kind of bursts is still not well understood. In fact, simplified simulations of the outer layers of an accreting neutron star in a binary are not yet able to reproduce all observable features.
The work presented in this thesis is devoted to the one-dimensional simulations of X-ray bursts and superbursts. The numerical code used in this work has initially been programmed by J. Fisker in 2006. By updating and optimizing the code, we are able to simulate X-ray bursts as well as superbursts in a feasible time range. Using a large nulear network, we study the features of X-ray bursts and compare them with observations. To understand the link between various properties entering our simulations as parameters or boundary conditions, we present several models which reproduces hunderds of X-ray burst. In this current work, we focus mainly on changes in crustal heating, accretion rate and accretion composition. Analyzing the influence on the light curve as well as on the ashes of X-ray bursts, we are able to compare our results with observations. To shed some light on the self-consistent ignition of a superburst, we model a setup which may lead to the ignition of a superburst.
Our results suggest that additional helium, heavier isotopes and the lack of hydrogen in the accretion composition help to generate carbon-rich X-ray burst ashes. Strong heating below the superburst ignition layer prevents the destruction of carbon after an X-ray bursts and might be the key ingredience in the self-consistent ignition of a superburst within the time range of the observed recurrence tim
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