25,017 research outputs found
Geometric distortion analysis of a wide-field astrograph
Ground-based optical navigation seeks to determine the angular position of a star, Solar System body, or laser-emitting spacecraft relative to objects with well-known coordinates. Measurement accuracies of 25 nrad would make optical techniques competitive with current radio metric technology. This article examines a proposed design for a wide-field astrograph and concludes that the deviation of an image centroid from the ideal projection can be modeled to the desired accuracy provided that the field of view does not exceed 5 deg on a side
Manufacture of DPFC-DMS polymer in the SKG range
BPFC-DMS block copolymers were synthesized on a pre-pilot scale (i.e., to 5 Kg lots) and subsequently fabricated into clear, colorless films. Details of the synthesis procedures, property determinations, and film casting techniques are presented. Solubility, viscosity and molecular weight characteristics of the resulting product are reported
Optimal randomized multilevel algorithms for infinite-dimensional integration on function spaces with ANOVA-type decomposition
In this paper, we consider the infinite-dimensional integration problem on
weighted reproducing kernel Hilbert spaces with norms induced by an underlying
function space decomposition of ANOVA-type. The weights model the relative
importance of different groups of variables. We present new randomized
multilevel algorithms to tackle this integration problem and prove upper bounds
for their randomized error. Furthermore, we provide in this setting the first
non-trivial lower error bounds for general randomized algorithms, which, in
particular, may be adaptive or non-linear. These lower bounds show that our
multilevel algorithms are optimal. Our analysis refines and extends the
analysis provided in [F. J. Hickernell, T. M\"uller-Gronbach, B. Niu, K.
Ritter, J. Complexity 26 (2010), 229-254], and our error bounds improve
substantially on the error bounds presented there. As an illustrative example,
we discuss the unanchored Sobolev space and employ randomized quasi-Monte Carlo
multilevel algorithms based on scrambled polynomial lattice rules.Comment: 31 pages, 0 figure
Start to end simulations of the ERL prototype at Daresbury Laboratory
Daresbury Laboratory is currently building an Energy Recovery Linac Prototype (ERLP) that will serve as a research and development facility for the study of beam dynamics and accelerator technology important to the design and construction of the proposed 4th Generation Light Source (4GLS) project. Two major objectives of the ERLP are the demonstration of energy recovery and of energy recovery from a beam disrupted by an FEL interaction as supplied by an infrared oscillator system. In this paper we present start-to-end simulations of the ERLP including such an FEL interaction. The beam dynamics in the highbrightness injector, which consists of a DC photocathode Gun and a superconducting booster, have been modelled using the particle tracking code ASTRA. After the booster the particles have been tracked with the code elegant. The 3D code GENESIS 1.3 was used to model the FEL interaction with the electron beam at 35 MeV. A brief summary of impedance and wakefield calculations for the whole machine is also given
How Much Longer Will it Take? A Ten-year Review of the Implementation of United Nations General Assembly Resolutions 61/105, 64/72 and 66/68 on the Management of Bottom Fisheries in Areas Beyond National Jurisdiction
The United Nations General Assembly (UNGA) in 2002 adopted the first in a series of resolutions regarding the conservation of biodiversity in the deep sea. Prompted by seriousconcerns raised by scientists, non-governmental organizations (NGOs) and numerous States,these resolutions progressively committed States to act both individually and through regional fishery management organizations (RFMOs) to either manage bottom fisheries in areas beyond national jurisdiction to prevent significant adverse impacts on deep-sea species, ecosystems and biodiversity or else prohibit bottom fishing from taking place.Ten years have passed since the adoption of resolution 61/105 in 2006, calling on States to take a set of specific actions to manage bottom fisheries in areas beyond national jurisdiction to protect vulnerable marine ecosystems (VMEs) from the adverse impacts of bottom fishing and ensure the sustainability of deep-sea fish stocks. Despite the considerable progress by some RFMOs, there remain significant gaps in the implementation of key elements and commitments in the resolutions. The Deep Sea Conservation Coalition (DSCC) has prepared this report to assist the UNGA in its review in 2016 and to address the following question: How effectively have the resolutions been implemented
Parity-expanded variational analysis for non-zero momentum
In recent years, the use of variational analysis techniques in lattice QCD
has been demonstrated to be successful in the investigation of the rest-mass
spectrum of many hadrons. However, due to parity-mixing, more care must be
taken for investigations of boosted states to ensure that the projected
correlation functions provided by the variational analysis correspond to the
same states at zero momentum. In this paper we present the Parity-Expanded
Variational Analysis (PEVA) technique, a novel method for ensuring the
successful and consistent isolation of boosted baryons through a parity
expansion of the operator basis used to construct the correlation matrix.Comment: 9 pages, 3 figures, 1 tabl
Probing the proton and its excitations in full QCD
We present a first look at the application of variational techniques for the
extraction of the electromagnetic properties of an excited nucleon system. In
particular, we include preliminary results for charge radii and magnetic
moments of the proton, its first even-parity excitation and the .Comment: 7 pages, 5 figures, presented at the 31st International Symposium on
Lattice Field Theory (Lattice 2013), 29 July - 3 August 2013, Mainz, German
Transition of in Lattice QCD
With the ongoing experimental interest in exploring the excited hadron
spectrum, evaluations of the matrix elements describing the formation and decay
of such states via radiative processes provide us with an important connection
between theory and experiment. In particular, determinations obtained via the
lattice allow for a direct comparison of QCD-expectation with experimental
observation. Here we present the first light quark determination of the transition form factor from lattice QCD using dynamical
quarks. Using the PACS-CS 2+1 flavour QCD ensembles we are able to obtain
results across a range of masses, to the near physical value of
MeV. An important aspect of our approach is the use of variational methods to
isolate the desired QCD eigenstate. For low-lying states, such techniques
facilitate the removal of excited state contributions. In principle the method
enables one to consider arbitrary eigenstates. We find our results are in
accord with the non-relativistic quark model for heavy masses. In moving
towards the light-quark regime we observe an interesting quark mass dependence,
contrary to the quark model expectation. Comparison of our light-quark result
with experimental determinations highlights a significant discrepancy
suggesting that disconnected sea-quark loop contributions may play a
significant role in fully describing this process.Comment: 9 pages, 5 figures and 1 tabl
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