7,315 research outputs found
Analysis of selective chopper radiometer data
Data from SCR-B on Nimbus 5 have been processed to yield global, orbital temperatures at 10, 5, 2, 1, and 0.4 mb for the period January 1977 through April 1978 under the current task. In addition gridded values at 10 deg latitude by 20 deg longitude were prepared by space-time interpolation for the period January 1975 through April 1978. Temperature retrieval was based on regression of radiances against Meteorological Rocket Network data, with regressions recomputed at approximately six-month intervals. This data now completes a consistent time series from April 1970 to April 1978 for all available radiance data from SCR A and SCR B on Nimbus 4 and 5. The processing details for the current period are discussed, but is also applicable to the previous data periods. The accuracy of the temperature retrievals for each 6-month period for the entire eight years is given in the Appendices
Upper-division Student Understanding of Coulomb's Law: Difficulties with Continuous Charge Distributions
Utilizing the integral expression of Coulomb's Law to determine the electric
potential from a continuous charge distribution is a canonical exercise in
Electricity and Magnetism (E&M). In this study, we use both think-aloud
interviews and responses to traditional exam questions to investigate student
difficulties with this topic at the upper-division level. Leveraging a
theoretical framework for the use of mathematics in physics, we discuss how
students activate, construct, execute and reflect on the integral form of
Coulomb's Law when solving problems with continuous charge distributions. We
present evidence that junior-level E&M students have difficulty mapping
physical systems onto the mathematical expression for the Coulomb potential.
Common challenges include difficulty expressing the difference vector in
appropriate coordinates as well as determining expressions for the differential
charge element and limits of integration for a specific charge distribution. We
discuss possible implications of these findings for future research directions
and instructional strategies.Comment: 5 pages, 1 figure, 2 tables, accepted to 2012 PERC Proceeding
Analytic Framework for Students' Use of Mathematics in Upper-Division Physics
Many students in upper-division physics courses struggle with the
mathematically sophisticated tools and techniques that are required for
advanced physics content. We have developed an analytical framework to assist
instructors and researchers in characterizing students' difficulties with
specific mathematical tools when solving the long and complex problems that are
characteristic of upper-division. In this paper, we present this framework,
including its motivation and development. We also describe an application of
the framework to investigations of student difficulties with direct integration
in electricity and magnetism (i.e., Coulomb's Law) and approximation methods in
classical mechanics (i.e., Taylor series). These investigations provide
examples of the types of difficulties encountered by advanced physics students,
as well as the utility of the framework for both researchers and instructors.Comment: 17 pages, 4 figures, 3 tables, in Phys. Rev. - PE
ACER: A Framework on the Use of Mathematics in Upper-division Physics
At the University of Colorado Boulder, as part of our broader efforts to
transform middle- and upper-division physics courses, we research students'
difficulties with particular concepts, methods, and tools in classical
mechanics, electromagnetism, and quantum mechanics. Unsurprisingly, a number of
difficulties are related to students' use of mathematical tools (e.g.,
approximation methods). Previous work has documented a number of challenges
that students must overcome to use mathematical tools fluently in introductory
physics (e.g., mapping meaning onto mathematical symbols). We have developed a
theoretical framework to facilitate connecting students' difficulties to
challenges with specific mathematical and physical concepts. In this paper, we
motivate the need for this framework and demonstrate its utility for both
researchers and course instructors by applying it to frame results from
interview data on students' use of Taylor approximations.Comment: 10 pages, 1 figures, 2 tables, accepted to the 2012 PERC Proceeding
Particle Swarm Optimization and gravitational wave data analysis: Performance on a binary inspiral testbed
The detection and estimation of gravitational wave (GW) signals belonging to
a parameterized family of waveforms requires, in general, the numerical
maximization of a data-dependent function of the signal parameters. Due to
noise in the data, the function to be maximized is often highly multi-modal
with numerous local maxima. Searching for the global maximum then becomes
computationally expensive, which in turn can limit the scientific scope of the
search. Stochastic optimization is one possible approach to reducing
computational costs in such applications. We report results from a first
investigation of the Particle Swarm Optimization (PSO) method in this context.
The method is applied to a testbed motivated by the problem of detection and
estimation of a binary inspiral signal. Our results show that PSO works well in
the presence of high multi-modality, making it a viable candidate method for
further applications in GW data analysis.Comment: 13 pages, 5 figure
Electric Polarizability of Neutral Hadrons from Lattice QCD
By simulating a uniform electric field on a lattice and measuring the change
in the rest mass, we calculate the electric polarizability of neutral mesons
and baryons using the methods of quenched lattice QCD. Specifically, we measure
the electric polarizability coefficient from the quadratic response to the
electric field for 10 particles: the vector mesons and ; the
octet baryons n, , , , and ;
and the decouplet baryons , , and .
Independent calculations using two fermion actions were done for consistency
and comparison purposes. One calculation uses Wilson fermions with a lattice
spacing of fm. The other uses tadpole improved L\"usher-Weiss gauge
fields and clover quark action with a lattice spacing fm. Our results
for neutron electric polarizability are compared to experiment.Comment: 25 pages, 20 figure
A preliminary analysis of the data from experiment 77-13 and final report on glass fining experiments in zero gravity
Thermal fining, thermal migration of bubbles under reduced gravity conditions, and data to verify current theoretical models of bubble location and temperatures as a function of time are discussed. A sample, sodium borate glass, was tested during 5 to 6 minutes of zero gravity during rocket flight. The test cell contained a heater strip; thermocouples were in the sample. At present quantitative data are insufficient to confirm results of theoretical calculations
Faculty survey on upper-division thermal physics content coverage
Thermal physics is a core course requirement for most physics degrees and
encompasses both thermodynamics and statistical mechanics content. However, the
primary content foci of thermal physics courses vary across universities. This
variation can make creation of materials or assessment tools for thermal
physics difficult. To determine the scope and content variability of thermal
physics courses across institutions, we distributed a survey to over 140
institutions to determine content priorities from faculty and instructors who
have taught upper-division thermodynamics and/or statistical mechanics. We
present results from the survey, which highlight key similarities and
differences in thermal physics content coverage across institutions. Though we
see variations in content coverage, we found 9 key topical areas covered by all
respondents in their upper-division thermal physics courses. We discuss
implications of these findings for the development of instructional tools and
assessments that are useful to the widest range of institutions and physics
instructors.Comment: Physics Education Research Conferenc
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