63,296 research outputs found
Toolboxes and handing students a hammer: The effects of cueing and instruction on getting students to think critically
Developing critical thinking skills is a common goal of an undergraduate
physics curriculum. How do students make sense of evidence and what do they do
with it? In this study, we evaluated students' critical thinking behaviors
through their written notebooks in an introductory physics laboratory course.
We compared student behaviors in the Structured Quantitative Inquiry Labs
(SQILabs) curriculum to a control group and evaluated the fragility of these
behaviors through procedural cueing. We found that the SQILabs were generally
effective at improving the quality of students' reasoning about data and making
decisions from data. These improvements in reasoning and sensemaking were
thwarted, however, by a procedural cue. We describe these changes in behavior
through the lens of epistemological frames and task orientation, invoked by the
instructional moves
Anomalous temperature-induced volume contraction in GeTe
The recent surge of interest in phase change materials GeTe,
GeSbTe, and related compounds motivated us to revisit the
structural phase transition in GeTe in more details than was done before.
Rhombohedral-to-cubic ferroelectric phase transition in GeTe has been studied
by high resolution neutron powder diffraction on a spallation neutron source.
We determined the temperature dependence of the structural parameters in a wide
temperature range extending from 309 to 973 K. Results of our studies clearly
show an anomalous volume contraction of 0.6\% at the phase transition from the
rhombohedral to cubic phase. In order to better understand the phase transition
and the associated anomalous volume decrease in GeTe we have performed phonon
calculations based on the density functional theory. Results of the present
investigations are also discussed with respect to the experimental data
obtained for single crystals of GeTe
Classical Langevin dynamics of a charged particle moving on a sphere and diamagnetism: A surprise
It is generally known that the orbital diamagnetism of a classical system of
charged particles in thermal equilibrium is identically zero -- the Bohr-van
Leeuwen theorem. Physically, this null result derives from the exact
cancellation of the orbital diamagnetic moment associated with the complete
cyclotron orbits of the charged particles by the paramagnetic moment subtended
by the incomplete orbits skipping the boundary in the opposite sense. Motivated
by this crucial, but subtle role of the boundary, we have simulated here the
case of a finite but \emph{unbounded} system, namely that of a charged particle
moving on the surface of a sphere in the presence of an externally applied
uniform magnetic field. Following a real space-time approach based on the
classical Langevin equation, we have computed the orbital magnetic moment which
now indeed turns out to be non-zero, and has the diamagnetic sign. To the best
of our knowledge, this is the first report of the possibility of finite
classical diamagnetism in principle, and it is due to the avoided cancellation.Comment: Accepted for publication in EP
The structure of the central disk of NGC 1068: a clumpy disk model
NGC 1068 is one of the best studied Seyfert II galaxies, for which the
blackhole mass has been determined from the Doppler velocities of water maser.
We show that the standard -disk model of NGC 1068 gives disk mass
between the radii of 0.65 pc and 1.1 pc (the region from which water maser
emission is detected) to be about 7x10 M (for ), more
than four times the blackhole mass, and a Toomre Q-parameter for the disk is
0.001. This disk is therefore highly self-gravitating and is subject to
large-amplitude density fluctuations. We conclude that the standard
-viscosity description for the structure of the accretion disk is
invalid for NGC 1068.
In this paper we develop a new model for the accretion disk. The disk is
considered to be composed of gravitationally bound clumps; accretion in this
clumped disk model arises because of gravitational interaction of clumps with
each other and the dynamical frictional drag exerted on clumps from the stars
in the central region of the galaxy. The clumped disk model provides a
self-consistent description of the observations of NGC 1068. The computed
temperature and density are within the allowed parameter range for water maser
emission, and the rotational velocity in the disk falls off as .Comment: To appear in Ap
Two and three-dimensional shock-shock interactions on the blunt leading edges of the hypersonic inlets
The effect of shock impingement on the blunt leading edges of the top and sidewall compression type inlet of a scramjet engine is studied numerically. The impinging shock is caused by the vehicle forebody. The interaction of this forebody shock with the inlet leading edge shock results in a very complex flowfield containing local regions of high pressure and intense heating. This complex flowfield in calculated by solving the Navier-Stokes equations using a finite volume flux splitting technique due to van Leer. To resolve the finer details of the flow structure as well as to predict the surface heat transfer accurately, adaptive grid technique is used in the analysis. Results of the present numerical study are compared with available experimental results
Modified SPLICE and its Extension to Non-Stereo Data for Noise Robust Speech Recognition
In this paper, a modification to the training process of the popular SPLICE
algorithm has been proposed for noise robust speech recognition. The
modification is based on feature correlations, and enables this stereo-based
algorithm to improve the performance in all noise conditions, especially in
unseen cases. Further, the modified framework is extended to work for
non-stereo datasets where clean and noisy training utterances, but not stereo
counterparts, are required. Finally, an MLLR-based computationally efficient
run-time noise adaptation method in SPLICE framework has been proposed. The
modified SPLICE shows 8.6% absolute improvement over SPLICE in Test C of
Aurora-2 database, and 2.93% overall. Non-stereo method shows 10.37% and 6.93%
absolute improvements over Aurora-2 and Aurora-4 baseline models respectively.
Run-time adaptation shows 9.89% absolute improvement in modified framework as
compared to SPLICE for Test C, and 4.96% overall w.r.t. standard MLLR
adaptation on HMMs.Comment: Submitted to Automatic Speech Recognition and Understanding (ASRU)
2013 Worksho
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