61,048 research outputs found
Multinomial selection index
Comparison of multivariate statistical analysis techniques for multinomial selection indice
Innovative Opportunities for Elementary and Middle School Teachers to Maintain Currency in Mathematics and Science: A Community College-School System Partnership
Since 1992 the Manassas Campus of Northern Virginia Community College – in response to requests from local school systems – has developed four innovative methods of assisting elementary, secondary and middle school teachers to enhance their content knowledge in science and mathematics, as well as integrate curriculum units for classroom presentation. These methods are based on the assumptions that: - While teachers at this level have fundamental understanding of math and science, if they wish to incorporate new concepts or technologies from these fields, graduate level content courses are generally beyond their background level. - Community College faculty can often provide a bridge that connects advanced content in science and mathematics with the applications that can be adapted to elementary/middle school curriculum. - Presenting content to a mixed audience of teachers from K-8 allows teachers to see how content can be adapted to grade levels above and below. - Content delivery methods must be interactive and must be responsive to the multiple demands on these teachers’ time. This requires flexibility in scheduling and course requirements
The influence of defects of the fatigue resistance of butt and girth welds in A106B steel
This three-phase study was directed at developing a fitness for service defect acceptance criteria for welds with defect indications. The study focussed on A106 Gr. B steel pipe. The first phase involved a literature search and critical review to develop the preliminary acceptance criteria to the extent permitted by the data. The second phase developed data for flat plate, wall segment, and vessel specimens containing artificial or natural planar or volumetric defects. The final phase developed acceptance criteria from the test data
Diurnal variation in harbour porpoise detection – potential implications for management
Peer reviewedPublisher PD
Superconductivity in SrNi2As2 Single Crystals
The electrical resistivity \rho(T) and heat capacity C(T) on single crystals
of SrNi2As2 and EuNi2As2 are reported. While there is no evidence for a
structural transition in either compound, SrNi2As2 is found to be a bulk
superconductor at T_c=0.62 K with a Sommerfeld coefficient of \gamma= 8.7
mJ/mol K^2 and a small upper critical field H_{c2} \sim 200 Oe. No
superconductivity was found in EuNi2As2 above 0.4 K, but anomalies in \rho and
C reveal that magnetic order associated with the Eu^{2+} magnetic moments
occurs at T_m = 14 K.Comment: 8 pages, 5 figure
Quantum walk-based search and centrality
We study the discrete-time quantum walk-based search for a marked vertex on a
graph. By considering various structures in which not all vertices are
equivalent, we investigate the relationship between the successful search
probability and the position of the marked vertex, in particular its
centrality. We find that the maximum value of the search probability does not
necessarily increase as the marked vertex becomes more central and we
investigate an interesting relationship between the frequency of the successful
search probability and the centrality of the marked vertex.Comment: 29 pages, 17 figure
On three-manifolds dominated by circle bundles
We determine which three-manifolds are dominated by products. The result is
that a closed, oriented, connected three-manifold is dominated by a product if
and only if it is finitely covered either by a product or by a connected sum of
copies of the product of the two-sphere and the circle. This characterization
can also be formulated in terms of Thurston geometries, or in terms of purely
algebraic properties of the fundamental group. We also determine which
three-manifolds are dominated by non-trivial circle bundles, and which
three-manifold groups are presentable by products.Comment: 12 pages; to appear in Math. Zeitschrift; ISSN 1103-467
Reactions at Polymer Interfaces: Transitions from Chemical to Diffusion-Control and Mixed Order Kinetics
We study reactions between end-functionalized chains at a polymer-polymer
interface. For small chemical reactivities (the typical case) the number of
diblocks formed, , obeys 2nd order chemically controlled kinetics, , until interfacial saturation. For high reactivities (e.g. radicals) a
transition occurs at short times to 2nd order diffusion-controlled kinetics,
with for unentangled chains while and
regimes occur for entangled chains. Long time kinetics are 1st order and
controlled by diffusion of the more dilute species to the interface: for unentangled cases, while and regimes
arise for entangled systems. The final 1st order regime is governed by center
of gravity diffusion, .Comment: 11 pages, 3 figures, uses poliface.sty, minor changes, to appear in
Europhysics Letter
Negative Differential Resistivity and Positive Temperature Coefficient of Resistivity effect in the diffusion limited current of ferroelectric thin film capacitors
We present a model for the leakage current in ferroelectric thin- film
capacitors which explains two of the observed phenomena that have escaped
satisfactory explanation, i.e. the occurrence of either a plateau or negative
differential resistivity at low voltages, and the observation of a Positive
Temperature Coefficient of Resistivity (PTCR) effect in certain samples in the
high-voltage regime. The leakage current is modelled by considering a
diffusion-limited current process, which in the high-voltage regime recovers
the diffusion-limited Schottky relationship of Simmons already shown to be
applicable in these systems
Understanding Student Computational Thinking with Computational Modeling
Recently, the National Research Council's framework for next generation
science standards highlighted "computational thinking" as one of its
"fundamental practices". 9th Grade students taking a physics course that
employed the Modeling Instruction curriculum were taught to construct
computational models of physical systems. Student computational thinking was
assessed using a proctored programming assignment, written essay, and a series
of think-aloud interviews, where the students produced and discussed a
computational model of a baseball in motion via a high-level programming
environment (VPython). Roughly a third of the students in the study were
successful in completing the programming assignment. Student success on this
assessment was tied to how students synthesized their knowledge of physics and
computation. On the essay and interview assessments, students displayed unique
views of the relationship between force and motion; those who spoke of this
relationship in causal (rather than observational) terms tended to have more
success in the programming exercise.Comment: preprint to submit to PERC proceedings 201
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