7,723 research outputs found
An evaluation of electronic individual peer assessment in an introductory programming course
[Abstract]: Peer learning is a powerful pedagogical practice delivering improved outcomes over conventional teacher-student interactions while offering marking relief to instructors. Peer review enables learning by requiring students to evaluate the work of others. PRAISE is an on-line peer-review system that facilitates anonymous review and delivers prompt feedback from multiple sources. This study is an evaluation of the use of PRAISE in an introductory programming course. Use of the system is examined and attitudes of novice programmers towards the use of peer review are compared to those of students from other disciplines, raising a number of interesting issues. Recommendations are made to introductory programming instructors who may be considering peer review in assignments
Cryogenic Microwave Imaging of Metal-Insulator Transition in Doped Silicon
We report the instrumentation and experimental results of a cryogenic
scanning microwave impedance microscope. The microwave probe and the scanning
stage are located inside the variable temperature insert of a helium cryostat.
Microwave signals in the distance modulation mode are used for monitoring the
tip-sample distance and adjusting the phase of the two output channels. The
ability to spatially resolve the metal-insulator transition in a doped silicon
sample is demonstrated. The data agree with a semi-quantitative finite-element
simulation. Effects of the thermal energy and electric fields on local charge
carriers can be seen in the images taken at different temperatures and DC
biases.Comment: 10 pages, 5 Figures, Accepted to Review of Scientific Instrumen
Dissecting the PPP Puzzle: The Unconventional Roles of Nominal Exchange Rate and Price Adjustment
The conventional view, as expounded by sticky-price models, is that price adjustment determines the PPP reversion rate. This study examines the mechanism by which PPP deviations are corrected. Nominal exchange rate adjustment, not price adjustment, is shown to be the key engine governing the speed of PPP convergence. Moreover, nominal exchange rates are found to converge much more slowly than prices. With the reversion being driven primarily by nominal exchange rates, real exchange rates also revert at a slower rate than prices, as identified by the PPP puzzle (Rogoff, 1996).
The Energetic Implications of Using Deforming Reference Descriptions to Simulate the Motion of Incompressible, Newtonian Fluids
In this work the issue of whether key energetic properties (nonlinear,
exponential-type dissipation in the abscence of forcing and long-term stability
under conditions of time dependent loading) are automatically inherited by
deforming reference descriptions is resolved. These properties are intrinsic to
real flows and the conventional Navier-Stokes equations. A completely general
reference description of an incompressible, Newtonian fluid, which reconciles
the differences between opposing schools of thought in the literature is
derived for the purposes of this investigation.
The work subsequently focusses on establishing a class of time
discretisations which inherit these self-same energetic properties,
irrespective of the time increment employed. The findings of this analysis have
profound consequences for the use of certain classes of finite difference
schemes in the context of deforming references. It is significant that many
algorithms presently in use do not automatically inherit the fundamental
qualitative features of the dynamics. An `updated' approach as a means of
avoiding ever burgeoning deformation gradients and a still further simplified
implementation are further topics explored.Comment: 26 pages, 2 figures, lemma 2 proof correcte
Tunable current circulation in triangular quantum-dot metastructures
Advances in fabrication and control of quantum dots allow the realization of
metastructures that may exhibit novel electrical transport phenomena. Here, we
investigate the electrical current passing through one such metastructure, a
system composed of quantum dots placed at the vertices of a triangle. The wave
natural of quantum particles leads to internal current circulation within the
metastructure in the absence of any external magnetic field. We uncover the
relation between its steady-state total current and the internal circulation.
By calculating the electronic correlations in quantum transport exactly, we
present phase diagrams showing where different types of current circulation can
be found as a function of the correlation strength and the coupling between the
quantum dots. Finally, we show that the regimes of current circulation can be
further enhanced or reduced depending on the local spatial distribution of the
interactions, suggesting a single-particle scattering mechanism is at play even
in the strongly-correlated regime. We suggest experimental realizations of
actual quantum-dot metastructures where our predictions can be directly tested.Comment: 5 pages, 4 figures, the Supplemental Information is attached at the
en
Self-normalized processes: exponential inequalities, moment bounds and iterated logarithm laws
Self-normalized processes arise naturally in statistical applications.
Being unit free, they are not affected by scale changes. Moreover,
self-normalization often eliminates or weakens moment assumptions. In this
paper we present several exponential and moment inequalities, particularly
those related to laws of the iterated logarithm, for self-normalized random
variables including martingales. Tail probability bounds are also derived. For
random variables B_t>0 and A_t, let Y_t(\lambda)=\exp{\lambda A_t-\lambda
^2B_t^2/2}. We develop inequalities for the moments of A_t/B_{t} or sup_{t\geq
0}A_t/{B_t(\log \log B_{t})^{1/2}} and variants thereof, when EY_t(\lambda
)\leq 1 or when Y_t(\lambda) is a supermartingale, for all \lambda belonging to
some interval. Our results are valid for a wide class of random processes
including continuous martingales with A_t=M_t and B_t=\sqrt _t, and sums of
conditionally symmetric variables d_i with A_t=\sum_{i=1}^td_i and
B_t=\sqrt\sum_{i=1}^td_i^2. A sharp maximal inequality for conditionally
symmetric random variables and for continuous local martingales with values in
R^m, m\ge 1, is also established. Another development in this paper is a
bounded law of the iterated logarithm for general adapted sequences that are
centered at certain truncated conditional expectations and self-normalized by
the square root of the sum of squares. The key ingredient in this development
is a new exponential supermartingale involving \sum_{i=1}^td_i and
\sum_{i=1}^td_i^2.Comment: Published by the Institute of Mathematical Statistics
(http://www.imstat.org) in the Annals of Probability
(http://www.imstat.org/aop/) at http://dx.doi.org/10.1214/00911790400000039
- …