11,519 research outputs found

    Aberration Corrected Emittance Exchange

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    Full exploitation of emittance exchange (EEX) requires aberration-free performance of a complex imaging system including active radio-frequency (RF) elements which can add temporal distortions. We investigate the performance of an EEX line where the exchange occurs between two dimensions with normalized emittances which differ by multiple orders of magnitude. The transverse emittance is exchanged into the longitudinal dimension using a double dog-leg emittance exchange setup with a five cell RF deflector cavity. Aberration correction is performed on the four most dominant aberrations. These include temporal aberrations that are corrected with higher order magnetic optical elements located where longitudinal and transverse emittance are coupled. We demonstrate aberration-free performance of an EEX line with emittances differing by four orders of magnitude, \textit{i.e.} an initial transverse emittance of 1~pm-rad is exchanged with a longitudinal emittance of 10~nm-rad

    A user's guide for painters and cyclists: very abstract painting and serious cycling

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    This practice led research investigates the relationship between cycling and abstract painting. It is a written commentary presented alongside my artwork that gives voice to my studio practice. The history of abstraction and cycling are explored to discuss the myths and nuances of painterly practice, cycling and the studio. The text is an assemblage or collage, put together to represent the modality of interests in the studio and an exploration of key motivations that have driven my practice during this research. There are chronological and parallel developments in the history of Modernist painting and the history of cycling, I will use these to illuminate my relationship to painting and explore the mechanics of the studio. The fact that cycling and painting are both caught up in their own histories is evidenced and also how at certain moments these histories have intertwined and overlapped, such as, in the work of Marcel Duchamp and Alfred Jarry. I have produced a text that is intended to reflect the complexities and impossibilities of explaining an intuitive, visually driven studio practice. It seeks to examine and present key relationships within my painting and the studio in order to extend my knowledge and the vocabulary of my making. The writing touches on the not always immediately apparent connection between my work and those things that populate the studio, I am interested here in the coincidences, references and happenchance that enable and nourish my work in the studio. I discuss first hand meetings between myself and other artists, how work is sustained through studio visits and discussion. I investigate the placement and logic of references and how they function. I am interested in how past historical works enable, inform and develop artwork, these precedents are explored here to gain insight into practice. I consider the role of abstraction in my practice, what it means and how the idea of non-figurative painting is negotiated by myself and others. The history of painting and the work of other artists leave a trace in my studio, a catalogue of references, which allow me to navigate my paintings and give them context. This is in no way a definitive history of abstraction but an attempt to map a personal dialogue, implied by the paintings and suggested by theoretical writings and the curatorial landscape of contemporary painting in London. The reflection on paintings‚Äô past is to be focused on the early and mid-twentieth century traditions of abstraction and its persistence in the post-conceptual art landscape of contemporary artistic practice and current painting. I do envisage this as an attempt to address the specific and historical problems of painting, in particular the contested and shifting position of abstraction. I decided to research abstract painting because it is the domain in which my own practice situates itself, but it also allows me to direct my historical study towards a particular period of painting and pick up on a current dialogue on the reach of modernist practice and the contemporary place of abstraction. In order to do this I will use the somewhat disparate voices that are the key texts that have informed and become my influences in the studio. The texts of Jean Luc Nancy, Ludwig Wittgenstein‚Äôs and Roland Barthes have been a constant presence throughout this research and have provided a framework for this writing. The relevance, pertinence and necessity of these writings have not always been immediately apparent, their relationship to the vocabulary of a painting sometimes oblique. I have appropriated the Wittgenstein‚Äôs text Zettel, a post-humously published series of numbered fragments and quoted them here to enable me to respond to them and use Wittgenstein‚Äôs language of visual depiction (to explore philosophical thought) to give a structure to my reflections on painting. Jean Luc Nancy‚Äôs writing has allowed me to place texts together that are both attracting and repelling, pleasing and repulsing, hoping to find a traction between them and to draw out invisible, previously untraced lines between what concerns my practice and my writing. I take from Nancy the idea of presence in terms of painting and how might this be considered, that text and painting both present something, have presence. Nancy is instructional for shedding light on my thinking about text and image, to assist the discussion, to develop the relationship, to signal ideas about painting and writing. The text explores image, the image therefore captures the text. In this research I consider moments of cyclings past, in order to explore the way in which cycling might describe ways of being. A way of describing movement and existing, of going beyond or outside of oneself, exceeding. So cycling, as discussed here, is often the negotiation of a climb, the assent, the rise, moments where the essence of the race is found; altitude, height, the peak. Nancy speaks of the intimately mingled relationship between form and intensity, that intensity animates form. And so to interpret, to understand and to position my thinking about painting, cycling has been useful and insightful. In Hubert Damisch‚Äôs discussion on the tradition of Chinese painting there is the opportunity to think outside of a Western Tradition about how to animate the field of a painting. Considered here is the idea of painting made up of limits, paths and journeys. The order in which the development of an image might be traced, how a brush might journey through a work. The flesh and bone of a work are discussed through a meditation and reflection on the relationship of brush to ink. In Chinese painting the pictorial field and its orientation are, says Damisch, given priority over delineation. But this kind of delineation is not set up to separate or isolate the fields of the painting but to open up a relationship of opposites and allow a dialectical relationship to occur across the painting. A pivotal part of this research, is the reading of Zettel by Ludwig Wittgenstein, which allowed me to respond to my practice as a thread of connected but unrelated ideas. A discussion on how a text might explore and reflect the content in my work but also the continuity or discontinuity of approaches in my thinking about painting. Visually specific and descriptive Zettel connected to my paintings with its open and abstract propositions. The question of intention, connectivity and meaning are brought up by these writings and help to establish a pattern for a series of responses to my own painting and reflections on practice. The quotes I use are part of a posthumously published, fragmented collection, open-ended, they are descriptions of ideas that conjure visual pictures and enable me to respond with a collection of ideas on practice. The writings were found clipped together, somewhat ordered and boxed. Are they random? What interested me about this is that they ask questions about arrangement, for my work and this writing. And so, this allows me to touch on the openness of my practice and the question of refinement and resolution that the painting presents. I discuss how Modernist painterly abstraction and in particular how the writing of this period sought to resist depiction and mimicry. Placement is suggested by my reading and revealed in the arrangement of these writings and how they are placed or collaged together. The possibility of leaving something unsaid is explored here and considered alongside the impossibility of description when discussing painterly abstraction. The associations or representations about practice are oblique, lateral and sometimes silent. I have sought an open interpretation to these writings, suggested by my practice. The relationship between the text and painting affirm a language that is an attempt at equivalence, seeking to engage the impossibility of writing about painting, within the text. I have used cycling and the race to reveal and suggest something outside of the more formal and painterly signs of the works, the references chosen are fluid and revealing, suggestive of other dimensions and movement in space. For example, an Alpine stage of the Tour de France allows me to move beyond a formal description of painterly practice and describe movement in three and four dimensions, time and space in the world where the relationship of viewer to practice takes place. I have for some time balanced cycle training and racing with my studio practice and the two disciplines have become woven together. Cycling clubs usually take their name from the town or suburb where they were formed, the Finsbury Park Cycling Club was founded in the nineteenth century and is known as ‚ÄúThe Park‚ÄĚ to its members - I joined the club in 1999. As a cyclist and painter both activities are autobiographical, they are a record of my time and activity they leaving patterns and traces that are both diaristic and instructional. In many senses both activities require balance and practice and are maintained through spatial awareness, timing, and reflection, they are also, for me, habits that are often remarkable for their consistency. And so to illuminate what happens in the studio, to describe the stance of my painting, to explore the contested position and the challenge of painting I have used cycling as a narrative device. I have sought within these two disciplines certain fixed points in their development, a development that is episodic, tumultuous, and limited in duration. In Roland Barthes essay The Tour de France as Epic he describes the poetic nature of the Tour through the production of a Racer‚Äôs Lexicon and the Tours Homer like myths. ‚ÄėThe gradients are wicked, reduced to difficult or deadly percentages, and the relays - each of which has the unity of a chapter in a novel (we are given, in effect, an epic duration, an additive sequence of absolute crisis and not the dialectical progression of a single conflict, as in tragic duration) - the relays are above all physical characters, successive enemies, individualized by that combination of morphology and morality which defines an epic Nature. The relay is hairy, sticky, burnt-out, bristling, etc., all adjectives which belong to an essential order of qualification and seek to indicate that the racer is at grips not with some natural difficulty but with a veritable theme of existence, a substantial theme in which he engages, by a single impulse, his perception and his judgement.‚Äô Like a grand tour this writing is a series of stages, some are flat and long, others traverse the mountains, some are cobbled, whilst others are concentrated in and circle the city. It is a training diary and a formula for the studio, it documents my attempts to elicit the most from tired limbs. How do we begin and train? How do I pick up the brush and paint? What is present and with me in my practice and has touched me over the period of this research? The negotiation of a gradient and terrain, the creation of a route, the practice of an unchartered but at the same time familiar journey. These parameters, limits and boundaries enable practice to settle within a framework. The limits of time, physical limits, the reach that defines and dictates the scale of my movement. The lactate acid (see below) that accumulates in the muscles and burns. My progress in training is tracked by a GPS and measured by Functional Threshold Power (FTP) - my body‚Äôs ability to process lactate as I attempt to extend the point at which speed and progress can be sustained. The development of painting and paintings are somewhat glacial, as change is seldom dynamic, the nature of the medium and materials will not allow for sudden shifts. So development needs careful planning and a series of timed efforts. In cycling changes can only be compounded with the correct recovery and nutrition, progress in painting is only made with the correct period of reflection. The work is periodic, studio time is similar to training, it is formulaic and a search for the atypical moment that steps out and goes beyond the attempt to paint what is pictorially effective and genuinely surprises. Both painting and cycling can be seen as marginal, outdated technologies, they are the practice of a minority, but they are both activities which periodically gain some traction and threaten to crossover to the mainstream

    A vectorized code for calculating laminar and turbulent hypersonic flows about blunt axisymmetric bodies at zero and small angles of attack

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    A user's guide is provided for a computer code which calculates the laminar and turbulent hypersonic flows about blunt axisymmetric bodies, such as spherically blunted cones, hyperboloids, etc., at zero and small angles of attack. The code is written in STAR FORTRAN language for the CDC-STAR-100 computer. Time-dependent, viscous-shock-layer-type equations are used to describe the flow field. These equations are solved by an explicit, two-step, time asymptotic, finite-difference method. For the turbulent flow, a two-layer, eddy-viscosity model is used. The code provides complete flow-field properties including shock location, surface pressure distribution, surface heating rates, and skin-friction coefficients. This report contains descriptions of the input and output, the listing of the program, and a sample flow-field solution

    Marsupials and monotremes sort genome treasures from junk

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    A recent landmark paper demonstrates the unique contribution of marsupials and monotremes to comparative genome analysis, filling an evolutionary gap between the eutherian mammals (including humans) and more distant vertebrate species

    Composite fuselage technology

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    The overall objective is to identify and understand, via directed experimentation and analysis, the mechanisms which control the structural behavior of fuselages in their response to damage (resistance, tolerance, and arrest). A further objective is to develop straightforward design methodologies which can be employed by structural designers in preliminary design stages to make intelligent choices concerning the material, layup, and structural configuration so that a more efficient structure with structural integrity can be designed and built

    Composite fuselage technology (summary of year 2)

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    The overall objective of this work is to identify and understand, via directed experimentation and analysis, the mechanisms which control the structural behavior of fuselages in their response to damage (resistance, tolerance, and arrest). A further objective is to develop straightforward design methodologies which can be employed by structural designers in preliminary design stages to make intelligent choices concerning the material, layup, and structural configuration so that a more efficient structure with structural integrity can be designed and built

    Correcting political and consumer misperceptions

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    While fact-checking has grown dramatically in the last decade, little is known about the relative effectiveness of different formats in correcting false beliefs or overcoming partisan resistance to new information. This article addresses that gap by using theories from communication and psychology to compare two prevailing approaches: An online experiment examined how the use of visual ‚Äútruth scales‚ÄĚ interacts with partisanship to shape the effectiveness of corrections. We find that truth scales make fact-checks more effective in some conditions. Contrary to theoretical predictions and the fears of some journalists, their use does not increase partisan backlash against the correction or the organization that produced it

    Nano-modulated electron beams via electron diffraction and emittance exchange for coherent x-ray generation

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    We present a new method for generation of relativistic electron beams with current modulation on the nanometer scale and below. The current modulation is produced by diffracting relativistic electrons in single crystal Si, accelerating the diffracted beam and imaging the crystal structure, then transferring the image into the temporal dimension via emittance exchange. The modulation period can be tuned by adjusting electron optics after diffraction. This tunable longitudinal modulation can have a period as short as a few angstroms, enabling production of coherent hard x-rays from a source based on inverse Compton scattering with total accelerator length of approximately ten meters. Electron beam simulations from cathode emission through diffraction, acceleration and image formation with variable magnification are presented along with estimates of the coherent x-ray output properties

    User's guide for vectorized code EQUIL for calculating equilibrium chemistry on Control Data STAR-100 computer

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    A vectorized code, EQUIL, was developed for calculating the equilibrium chemistry of a reacting gas mixture on the Control Data STAR-100 computer. The code provides species mole fractions, mass fractions, and thermodynamic and transport properties of the mixture for given temperature, pressure, and elemental mass fractions. The code is set up for the electrons H, He, C, O, N system of elements. In all, 24 chemical species are included

    Viscous compressible flow about blunt bodies using a numerically generated orthogonal coordinate system

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    A numerical solution to the Navier-Stokes equations was obtained for blunt axisymmetric entry bodies of arbitrary shape in supersonic flow. These equations are solved on a finite difference mesh obtained from a simple numerical technique which generates orthogonal coordinates between arbitrary boundaries. The governing equations are solved in time dependent form using Stetter's improved stability three step predictor corrector method. For the present application, the metric coefficients were obtained numerically using fourth order accurate, finite difference relations and proved to be totally reliable for the highly stretched mesh used to resolve the thin viscous boundary layer. Solutions are obtained for a range of blunt body nose shapes including concavities
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