55,968 research outputs found
Recommended from our members
Assessment, Evaluations and Definitions of Research Impact: A Review
This article aims to explore what is understood by the term âresearch impactâ and to provide a comprehensive assimilation of available literature and information, drawing on global experiences to understand the potential for methods and frameworks of impact assessment being implemented for UK impact assessment. We take a more focused look at the impact component of the UK Research Excellence Framework taking place in 2014 and some of the challenges to evaluating impact and the role that systems might play in the future for capturing the links between research and impact and the requirements we have for these systems.Jisc [DIINN10
Understanding Confinement From Deconfinement
We use effective magnetic SU(N) pure gauge theory with cutoff M and fixed
gauge coupling g_m to calculate non-perturbative magnetic properties of the
deconfined phase of SU(N) Yang-Mills theory. We obtain the response to an
external closed loop of electric current by reinterpreting and regulating the
calculation of the one loop effective potential in Yang-Mills theory. This
effective potential gives rise to a color magnetic charge density, the
counterpart in the deconfined phase of color magnetic currents introduced in
effective dual superconductor theories of the confined phase via magnetically
charged Higgs fields. The resulting spatial Wilson loop has area law behavior.
Using values of M and g_m determined in the confined phase, we find SU(3)
spatial string tensions compatible with lattice simulations in the temperature
interval 1.5T_c < T < 2.5T_c. Use of the effective theory to analyze
experiments on heavy ion collisions will provide applications and further tests
of these ideas.Comment: 18 pages, 5 figures, v2: fixed archive title (only
Structural analysis of stratocumulus convection
The 1 and 20 Hz data are examined from the Electra flights made on July 5, 1987. The flight legs consisted of seven horizontal turbulent legs at the inversion, midcloud, and below clouds, plus 4 soundings made within the same period. The Rosemont temperature sensor and the top and bottom dewpoint sensors were used to measure temperature and humidity at 1 Hz. Inversion structure and entrainment; local dynamics and large scale forcing; convective elements; and decoupling of cloud and subcloud are discussed in relationship to the results of the Electra flight
Simulations and observations of cloudtop processes
Turbulent entrainment at zero mean shear stratified interfaces has been studied extensively in the laboratory and theoretically for the classical situation in which density is a passive tracer of the mixing and the turbulent motions producing the entrainment are directed toward the interface. It is the purpose of the numerical simulations and data analysis to investigate these processes and, specifically, to focus on the following questions: (1) Can local cooling below cloudtop play an important role in setting up convective circulations within the cloud, and bringing about entrainment; (2) Can Cloudtop Entrainment Instability (CEI) alone lead to runaway entrainment under geophysically realistic conditions; and (3) What are the important mechanisms of entrainment at cloudtop under zero or low mean shear conditions
Confinement: Understanding the Relation Between the Wilson Loop and Dual Theories of Long Distance Yang Mills Theory
In this paper we express the velocity dependent, spin dependent heavy quark
potential in QCD in terms of a Wilson Loop determined
by pure Yang Mills theory. We use an effective dual theory of long-distance
Yang Mills theory to calculate for large loops; i.e. for loops of
size . ( is the flux tube radius, fixed by the value of the
Higgs (monopole) mass of the dual theory, which is a concrete realization of
the Mandelstam 't Hooft dual superconductor mechanism of confinement).
We replace by , given by a functional integral
over the dual variables, which for can be evaluated by a
semiclassical expansion, since the dual theory is weakly coupled at these
distances. The classical approximation gives the leading contribution to
and yields a velocity dependent heavy quark potential which
for large becomes linear in , and which for small approaches lowest
order perturbative QCD. This latter fact means that these results should remain
applicable down to distances where radiative corrections giving rise to a
running coupling constant become important. The spin dependence of the
potential reflects the vector coupling of the quarks at long range as well as
at short range. The methods developed here should be applicable to any
realization of the dual superconductor mechanism. They give an expression
determining independent of the classical approximation, but
semi classical corrections due to fluctuations of the flux tube are not worked
out in this paper. Taking these into account should lead to an effective string
theory free from the conformal anomaly.Comment: 39 pages, latex2e, 1 figure(fig.eps
Observing mergers of non-spinning black-hole binaries
Advances in the field of numerical relativity now make it possible to
calculate the final, most powerful merger phase of binary black-hole
coalescence for generic binaries. The state of the art has advanced well beyond
the equal-mass case into the unequal-mass and spinning regions of parameter
space. We present a study of the nonspinning portion of parameter space,
primarily using an analytic waveform model tuned to available numerical data,
with an emphasis on observational implications. We investigate the impact of
varied mass ratio on merger signal-to-noise ratios (SNRs) for several
detectors, and compare our results with expectations from the test-mass limit.
We note a striking similarity of the waveform phasing of the merger waveform
across the available mass ratios. Motivated by this, we calculate the match
between our 1:1 (equal mass) and 4:1 mass-ratio waveforms during the merger as
a function of location on the source sky, using a new formalism for the match
that accounts for higher harmonics. This is an indicator of the amount of
degeneracy in mass ratio for mergers of moderate-mass-ratio systems.Comment: 13 pages, 11 figures, submitted to Phys. Rev.
Profiling unauthorized natural resource users for better targeting of conservation interventions
Unauthorized use of natural resources is a key threat to many protected areas. Approaches to reducing this threat include law enforcement and integrated conservation and development (ICD) projects, but for such ICDs to be targeted effectively, it is important to understand who is illegally using which natural resources and why. The nature of unauthorized behavior makes it difficult to ascertain this information through direct questioning. Bwindi Impenetrable National Park, Uganda, has many ICD projects, including authorizing some local people to use certain nontimber forest resources from the park. However, despite over 25 years of ICD, unauthorized resource use continues. We used household surveys, indirect questioning (unmatched count technique), and focus group discussions to generate profiles of authorized and unauthorized resource users and to explore motivations for unauthorized activity. Overall, unauthorized resource use was most common among people from poor households who lived closest to the park boundary and farthest from roads and trading centers. Other motivations for unauthorized resource use included crop raiding by wild animals, inequity of revenue sharing, and lack of employment, factors that created resentment among the poorest communities. In some communities, benefits obtained from ICD were reported to be the greatest deterrents against unauthorized activity, although law enforcement ranked highest overall. Despite the sensitive nature of exploring unauthorized resource use, managementârelevant insights into the profiles and motivations of unauthorized resource users can be gained from a combination of survey techniques, as adopted here. To reduce unauthorized activity at Bwindi, we suggest ICD benefit the poorest people living in remote areas and near the park boundary by providing affordable alternative sources of forest products and addressing crop raiding. To prevent resentment from driving further unauthorized activity, ICDs should be managed transparently and equitably
On the evaluation formula for Jack polynomials with prescribed symmetry
The Jack polynomials with prescribed symmetry are obtained from the
nonsymmetric polynomials via the operations of symmetrization,
antisymmetrization and normalization. After dividing out the corresponding
antisymmetric polynomial of smallest degree, a symmetric polynomial results. Of
interest in applications is the value of the latter polynomial when all the
variables are set equal. Dunkl has obtained this evaluation, making use of a
certain skew symmetric operator. We introduce a simpler operator for this
purpose, thereby obtaining a new derivation of the evaluation formula. An
expansion formula of a certain product in terms of Jack polynomials with
prescribed symmetry implied by the evaluation formula is used to derive a
generalization of a constant term identity due to Macdonald, Kadell and Kaneko.
Although we don't give the details in this work, the operator introduced here
can be defined for any reduced crystallographic root system, and used to
provide an evaluation formula for the corresponding Heckman-Opdam polynomials
with prescribed symmetry.Comment: 18 page
Noise-Adaptive Compiler Mappings for Noisy Intermediate-Scale Quantum Computers
A massive gap exists between current quantum computing (QC) prototypes, and
the size and scale required for many proposed QC algorithms. Current QC
implementations are prone to noise and variability which affect their
reliability, and yet with less than 80 quantum bits (qubits) total, they are
too resource-constrained to implement error correction. The term Noisy
Intermediate-Scale Quantum (NISQ) refers to these current and near-term systems
of 1000 qubits or less. Given NISQ's severe resource constraints, low
reliability, and high variability in physical characteristics such as coherence
time or error rates, it is of pressing importance to map computations onto them
in ways that use resources efficiently and maximize the likelihood of
successful runs.
This paper proposes and evaluates backend compiler approaches to map and
optimize high-level QC programs to execute with high reliability on NISQ
systems with diverse hardware characteristics. Our techniques all start from an
LLVM intermediate representation of the quantum program (such as would be
generated from high-level QC languages like Scaffold) and generate QC
executables runnable on the IBM Q public QC machine. We then use this framework
to implement and evaluate several optimal and heuristic mapping methods. These
methods vary in how they account for the availability of dynamic machine
calibration data, the relative importance of various noise parameters, the
different possible routing strategies, and the relative importance of
compile-time scalability versus runtime success. Using real-system
measurements, we show that fine grained spatial and temporal variations in
hardware parameters can be exploited to obtain an average x (and up to
x) improvement in program success rate over the industry standard IBM
Qiskit compiler.Comment: To appear in ASPLOS'1
Coronal mass ejections, magnetic clouds, and relativistic magnetospheric electron events: ISTP
The role of high-speed solar wind streams in driving relativistic electron acceleration within the Earth\u27s magnetosphere during solar activity minimum conditions has been well documented. The rising phase of the new solar activity cycle (cycle 23) commenced in 1996, and there have recently been a number of coronal mass ejections (CMEs) and related âmagnetic cloudsâ at 1 AU. As these CME/cloud systems interact with the Earth\u27s magnetosphere, some events produce substantial enhancements in the magnetospheric energetic particle population while others do not. This paper compares and contrasts relativistic electron signatures observed by the POLAR, SAMPEX, Highly Elliptical Orbit, and geostationary orbit spacecraft during two magnetic cloud events: May 27â29, 1996, and January 10â11, 1997. Sequences were observed in each case in which the interplanetary magnetic field was first strongly southward and then rotated northward. In both cases, there were large solar wind density enhancements toward the end of the cloud passage at 1 AU. Strong energetic electron acceleration was observed in the January event, but not in the May event. The relative geoeffectiveness for these two cases is assessed, and it is concluded that large induced electric fields (âB/ât) caused in situ acceleration of electrons throughout the outer radiation zone during the January 1997 event
- âŠ