23,021 research outputs found
Curate and storyspace: an ontology and web-based environment for describing curatorial narratives
Existing metadata schemes and content management systems used by museums focus on describing the heritage objects that the museum holds in its collection. These are used to manage and describe individual heritage objects according to properties such as artist, date and preservation requirements. Curatorial narratives, such as physical or online exhibitions tell a story that spans across heritage objects and have a meaning that does not necessarily reside in the individual heritage objects themselves. Here we present curate, an ontology for describing curatorial narratives. This draws on structuralist accounts that distinguish the narrative from the story and plot, and also a detailed analysis of two museum exhibitions and the curatorial processes that contributed to them. Storyspace, our web based interface and API to the ontology, is being used by curatorial staff in two museums to model curatorial narratives and the processes through which they are constructed
Experimental observation of negative differential resistance from an InAs/GaSb interface
We have observed negative differential resistance at room temperature from devices consisting of a single interface between n-type InAs and p-type GaSb. InAs and GaSb have a type II staggered band alignment; hence, the negative differential resistance arises from the same mechanism as in a p+-n+ tunnel diode. Room-temperature peak current densities of 8.2×10^4 A/cm^2 and 4.2×10^4 A/cm^2 were measured for structures with and without undoped spacer layers at the heterointerface, respectively
Next-to-leading order QCD calculations with parton showers II: soft singularities
Programs that calculate observables in quantum chromodynamics at
next-to-leading order typically generate events that consist of partons rather
than hadrons -- and just a few partons at that. These programs would be much
more useful if the few partons were turned into parton showers, which could be
given to one of the Monte Carlo event generators to produce hadron showers. In
a previous paper, we have seen how to generate parton showers related to the
final state collinear singularities of the perturbative calculation for the
example of e+ + e- --> 3 jets. This paper discusses the treatment of the soft
singularities.Comment: 26 pages with 5 figures. This version is close to the version to be
publishe
Full QCD simulation on CP-PACS
A status report is made of an on-going full QCD study on the CP-PACS aiming
at a comparative analysis of the effects of improving gauge and quark actions
on hadronic quantities and static quark potential. Simulations are made for
four action combinations, the plaquette or an RG-improved action for gluons and
the Wilson or SW-clover action for quarks, at -1.3GeV and
-0.9. Results demonstrate clearly that the clover
term markedly reduces discretization errors for hadron spectrum, while adding
six-link terms to the plaquette action leads to much better rotational symmetry
in the potential. These results extend experience with quenched simulations to
full QCD.Comment: Talk presented by K. Kanaya at the International Workshop on
``LATTICE QCD ON PARALLEL COMPUTERS'', 10-15 March 1997, Center for
Computational Physics, University of Tsukub
Scanning tunneling microscopy of lnAs/GaSb superlattices: Subbands, interface roughness, and interface asymmetry
Scanning tunneling microscopy and spectroscopy is used to characterize InAs/GaSb superlattices, grown by molecular-beam epitaxy. Roughness at the interfaces between InAs and GaSb layers is directly observed in the images, and a quantitative spectrum of this roughness is obtained. Electron subbands in the InAs layers are resolved in spectroscopy. Asymmetry between the interfaces of InAs grown on GaSb compared with GaSb grown on In As is seen in voltage-dependent imaging. Detailed
spectroscopic study of the interfaces reveals some subtle differences between the two in terms of their valence-band onsets and conduction-band state density. These differences are interpreted in a model in which the GaSb on InAs interface has an abrupt InSb-like structure, but at the InAs on GaSb interface some Sb grading occurs into the InAs overlayer
Drell-Yan production at small q_T, transverse parton distributions and the collinear anomaly
Using methods from effective field theory, an exact all-order expression for
the Drell-Yan cross section at small transverse momentum is derived directly in
q_T space, in which all large logarithms are resummed. The anomalous dimensions
and matching coefficients necessary for resummation at NNLL order are given
explicitly. The precise relation between our result and the
Collins-Soper-Sterman formula is discussed, and as a by-product the previously
unknown three-loop coefficient A^(3) is obtained. The naive factorization of
the cross section at small transverse momentum is broken by a collinear
anomaly, which prevents a process-independent definition of x_T-dependent
parton distribution functions. A factorization theorem is derived for the
product of two such functions, in which the dependence on the hard momentum
transfer is separated out. The remainder factors into a product of two
functions of longitudinal momentum variables and x_T^2, whose
renormalization-group evolution is derived and solved in closed form. The
matching of these functions at small x_T onto standard parton distributions is
calculated at O(alpha_s), while their anomalous dimensions are known to three
loops.Comment: 32 pages, 2 figures; version to appear in Eur. Phys. J.
Nagy-Soper subtraction scheme for multiparton final states
In this work, we present the extension of an alternative subtraction scheme
for next-to-leading order QCD calculations to the case of an arbitrary number
of massless final-state partons. The scheme is based on the splitting kernels
of an improved parton shower and comes with a reduced number of final state
momentum mappings. While a previous publication including the setup of the
scheme has been restricted to cases with maximally two massless partons in the
final state, we here provide the final state real emission and integrated
subtraction terms for processes with any number of massless partons. We apply
our scheme to three jet production at lepton colliders at next-to-leading order
and present results for the differential C parameter distribution.Comment: 45 pages, 5 figures v2: several references added; v3: title changed,
references and a discussion of further scaling improvement added. Corresponds
to published journal versio
Extracting Muon Momentum Scale Corrections for Hadron Collider Experiments
We present a simple method for the extraction of corrections for bias in the
measurement of the momentum of muons in hadron collider experiments. Such bias
can originate from a variety of sources such as detector misalignment, software
reconstruction bias, and uncertainties in the magnetic field. The two step
method uses the mean for muons from $Z\to \mu\mu$ decays to
determine the momentum scale corrections in bins of charge, $\eta$ and $\phi$.
In the second step, the corrections are tuned by using the average invariant
mass of events in the same bins of charge
and . The forward-backward asymmetry of pairs
as a function of mass, and the distribution of bosons
in the Collins-Soper frame are used to ascertain that the corrections remove
the bias in the momentum measurements for positive versus negatively charged
muons. By taking the sum and difference of the momentum scale corrections for
positive and negative muons, we isolate additive corrections to
that may originate from misalignments and multiplicative corrections that may
originate from mis-modeling of the magnetic field . This method has recently been used in the CDF experiment at
Fermilab and in the CMS experiment at the Large Hadron Collider at CERNComment: 6 pages, 3 figures, to be published in EPJC 201
Initial-state parton shower kinematics for NLO event generators
We are developing a consistent method to combine tree-level event generators
for hadron collision interactions with those including one additional QCD
radiation from the initial-state partons, based on the limited leading-log
(LLL) subtraction method, aiming at an application to NLO event generators. In
this method, a boundary between non-radiative and radiative processes
necessarily appears at the factorization scale (mu_F). The radiation effects
are simulated using a parton shower (PS) in non-radiative processes. It is
therefore crucial in our method to apply a PS which well reproduces the
radiation activities evaluated from the matrix-element (ME) calculations for
radiative processes. The PS activity depends on the applied kinematics model.
In this paper we introduce two models for our simple initial-state leading-log
PS: a model similar to the "old" PYTHIA-PS and a p_T-prefixed model motivated
by ME calculations. PS simulations employing these models are tested using
W-boson production at LHC as an example. Both simulations show a smooth
matching to the LLL-subtracted W + 1 jet simulation in the p_T distribution of
W bosons, and the summed p_T spectra are stable against a variation of mu_F,
despite that the p_T-prefixed PS results in an apparently harder p_T spectrum.Comment: 10 pages, 6 figures; minor changes in the abstract and the text
according to the comments from the refere
An Examination of Keyes Universal Chart: 50 Years Later
© 2016 ASHRAE (www.ashrae.org). Published in ASHRAE Conference Papers, Winter Conference, Orlando, FL. For personal use only. Additional reproduction, distribution, or transmission in either print or digital form is not permitted without ASHRAE's prior written permission.From the late 1940's to the late 1960's, significant efforts were made by ASHVE and then ASHRAE to evaluate and quantify the impact of window shading. In the context of the now defunct Shading Coefficient, well known researchers such as Parmelee, Ozisik, Schutrum, Farber, Yellott, and Keyes laid the groundwork for much of the work that followed decades later. Of particular interest are the efforts of Keyes. In his work, he produced a method of classifying fabric based either on visible inspection, or on property measurements. The result was the Keyes Universal Chart, which was first published in the 1965 ASHRAE Guide and Data Book, and has been part of the Fenestration Chapter of the ASHRAE Handbook of Fundamentals since its inception. The chart compares fabric transmittance, reflectance, and openness. It also permits estimation of these properties by making generalized fabric classifications based on a subjective analysis of how light or dark the fabric is, and how open or closed the fabric weave is. More recently, significant efforts have been made to produce window shading models for use in building simulation and daylighting analysis. As part of this research, shading materials have been analyzed using modern and highly accurate spectrophotometric equipment. Unfortunately, that data has revealed inaccuracy in Keyes Universal Chart. The present work examines this inaccuracy.Natural Sciences and Engineering Research Council of Canada (NSERC
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