63,729 research outputs found
An extension to GUM methodology: degrees-of-freedom calculations for correlated multidimensional estimates
The Guide to the Expression of Uncertainty in Measurement advocates the use
of an 'effective number of degrees of freedom' for the calculation of an
interval of measurement uncertainty. However, it does not describe how this
number is to be calculated when (i) the measurand is a vector quantity or (ii)
when the errors in the estimates of the quantities defining the measurand (the
'input quantities') are not incurred independently. An appropriate analysis for
a vector-valued measurand has been described (Metrologia 39 (2002) 361-9), and
a method for a one-dimensional measurand with dependent errors has also been
given (Metrologia 44 (2007) 340-9). This paper builds on those analyses to
present a method for the situation where the problem is multidimensional and
involves correlated errors. The result is an explicit general procedure that
reduces to simpler procedures where appropriate. The example studied is from
the field of radio-frequency metrology, where measured quantities are often
complex-valued and can be regarded as vectors of two elements.Comment: 30 pages with 2 embedded figure
Climate Change and Great Lakes Water Resources
Looks at how climate change will impact water resources in the Great Lakes region and identifies policies to reduce greenhouse gas emissions that cause climate change
Singlet baryons in the graded symmetry approach to partially quenched QCD
Progress in the calculation of the electromagnetic properties of baryon
excitations in lattice QCD is presenting new challenges in the determination of
sea-quark loop contributions to matrix elements. A reliable estimation of the
sea-quark loop contributions presents a pressing issue in the accurate
comparison of lattice QCD results with experiment. In this article, an
extension of the graded symmetry approach to partially quenched QCD is
presented, which builds on previous theory by explicitly including
flavor-singlet baryons in its construction. The formalism takes into account
the interactions among both octet and singlet baryons, octet mesons, and their
ghost counterparts; the latter enables the isolation of the quark-flow
disconnected sea-quark loop contributions. The introduction of the
flavor-singlet states anticipates the application of the method to baryon
excitations such as the lowest-lying odd-parity Lambda baryon, the
Lambda(1405), which is considered in detail as a worked example.Comment: arXiv copy updated to published version: Phys. Rev. D 94, 094004
(2016
Chiral extrapolations for nucleon magnetic moments
Lattice QCD simulations have made significant progress in the calculation of
nucleon electromagnetic form factors in the chiral regime in recent years. With
simulation results achieving pion masses of order ~180 MeV, there is an
apparent challenge as to how the physical regime is approached. By using
contemporary methods in chiral effective field theory, both the quark-mass and
finite-volume dependence of the isovector nucleon magnetic moment are carefully
examined. The extrapolation to the physical point yields a result that is
compatible with experiment, albeit with a combined statistical and systematic
uncertainty of 10%. The extrapolation shows a strong finite-volume dependence;
lattice sizes of L > 5 fm must be used to simulate results within 2% of the
infinite-volume result for the magnetic moment at the physical pion mass.Comment: 7 pages, 12 figures, 1 tabl
Power Counting Regime of Chiral Effective Field Theory and Beyond
Chiral effective field theory complements numerical simulations of quantum
chromodynamics (QCD) on a space-time lattice. It provides a model-independent
formalism for connecting lattice simulation results at finite volume and a
variety of quark masses to the physical world. The asymptotic nature of the
chiral expansion places the focus on the first few terms of the expansion.
Thus, knowledge of the power-counting regime (PCR) of chiral effective field
theory, where higher-order terms of the expansion may be regarded as
negligible, is as important as knowledge of the expansion itself. Through the
consideration of a variety of renormalization schemes and associated
parameters, techniques to identify the PCR where results are independent of the
renormalization scheme are established. The nucleon mass is considered as a
benchmark for illustrating this general approach. Because the PCR is small, the
numerical simulation results are also examined to search for the possible
presence of an intrinsic scale which may be used in a nonperturbative manner to
describe lattice simulation results outside of the PCR. Positive results that
improve on the current optimistic application of chiral perturbation theory
beyond the PCR are reported.Comment: 18 pages, 55 figure
The environmental control and life-support system for a lunar base: What drives its design
The purpose of this paper is to identify and briefly discuss some of the ground rules and mission scenario details that become drivers of the environmental control and life support (ECLS) system design and of the logistics related to the design. This paper is written for mission planners and non-ECLS system engineers to inform them of the details that will be important to the ECLS engineer when the design phase is reached. In addition, examples illustrate the impact of some selected mission characteristics on the logistics associated with ECLS systems. The last section of this paper focuses on the ECLS system technology development sequence and highlights specific portions that need emphasis
Large time scale variation in hydrogen emission from Jupiter and Saturn
The IUE and Voyager spacecraft observations of Jupiter and Saturn were combined to obtain a consistent measurement of temporal variation of the equatorial subsolar hydrogen emission. The outer planets appear to have rather independent behavior over time scales of the order of 10 yr, particularly in emission from the H Ly alpha line. The time interval from 1978 to the present shows variation of mean equatorial H Ly alpha brightness of 2 at Jupiter and 5 at Saturn. The relative magnitudes of the variations is sufficiently different to suggest that response to input from the Sun is at least nonlinear. The brightness of H2 band emission appears to be relatively more stable than H Ly alpha. There is evidence in IUE observations of a moderate increase in H2 band brightness with increasing time at Jupiter, in opposition to the variation in H Ly alpha
Study of behavioral modifications resulting from exposure to high let radiation
Animal irradiations, behavioral studies, neurological studies, and nuclear medicine studies are discussed
Dispersal of \u3ci\u3eFenusa Dohrnii\u3c/i\u3e (Hymenoptera: Tenthredinidae) From an \u3ci\u3eAlnus\u3c/i\u3e Short-Rotation Forest Plantation
The European alder leafminer, Fenusa dohrnii, is a defoliating insect pest of Alnus in short-rotation forest plantations. A 2-year study was performed to quantify movement from infested stands to uninfested areas. Sticky traps and potted monitor trees were installed at different locations within and at various distances from (0,5, 10, and 20 m) an infested stand to measure adult flight and oviposition activity, respectively. Trap catch and oviposition activity fell off sharply with distance, few insects being trapped or eggs laid at distances of 5 m or greater from the infestation
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