1,318 research outputs found
On the Stability of Stochastic Parametrically Forced Equations with Rank One Forcing
We derive simplified formulas for analyzing the stability of stochastic
parametrically forced linear systems. This extends the results in [T. Blass and
L.A. Romero, SIAM J. Control Optim. 51(2):1099--1127, 2013] where, assuming the
stochastic excitation is small, the stability of such systems was computed
using a weighted sum of the extended power spectral density over the
eigenvalues of the unperturbed operator. In this paper, we show how to convert
this to a sum over the residues of the extended power spectral density. For
systems where the parametric forcing term is a rank one matrix, this leads to
an enormous simplification.Comment: 16 page
Block scheduling and its effect on the academic performance of students with learning disabilities
This study surveyed the professionals from one middle school in southern New Jersey regarding their perceptions of block scheduling as well as their views on its effectiveness with students who have learning disabilities. The survey indicated that the participants favored teaching under the block schedule format. They felt that they can address the students\u27 needs more effectively and that the quality and quantity of student work has improved. Some questions were directed only to special education teachers, and they also agreed that the time allocated using the block format helped them work more effectively with their students
On the length of chains of proper subgroups covering a topological group
We prove that if an ultrafilter L is not coherent to a Q-point, then each
analytic non-sigma-bounded topological group G admits an increasing chain <G_a
: a of its proper subgroups such that: (i) U_{a in b(L)} G_a=G; and
For every sigma-bounded subgroup H of G there exists a such that H is a
subset of G_a. In case of the group Sym(w) of all permutations of w with the
topology inherited from w^w this improves upon earlier results of S. Thomas
Laboratory studies, analysis, and interpretation of the spectra of hydrocarbons present in planetary atmospheres including cyanoacetylene, acetylene, propane, and ethane
Combining broadband Fourier transform spectrometers (FTS) from the McMath facility at NSO and from NRC in Ottawa and narrow band TDL data from the laboratories with computational physics techniques has produced a broad range of results for the study of planetary atmospheres. Motivation for the effort flows from the Voyager/IRIS observations and the needs of Voyager analysis for laboratory results. In addition, anticipation of the Cassini mission adds incentive to pursue studies of observed and potentially observable constituents of planetary atmospheres. Current studies include cyanoacetylene, acetylene, propane, and ethane. Particular attention is devoted to cyanoacetylen (H3CN) which is observed in the atmosphere of Titan. The results of a high resolution infrared laboratory study of the line positions of the 663, 449, and 22.5/cm fundamental bands are presented. Line position, reproducible to better than 5 MHz for the first two bands, are available for infrared astrophysical searches. Intensity and broadening studies are in progress. Acetylene is a nearly ubiquitous atmospheric constituent of the outer planets and Titan due to the nature of methane photochemistry. Results of ambient temperature absolute intensity measurements are presented for the fundamental and two two-quantum hotband in the 730/cm region. Low temperature hotband intensity and linewidth measurements are planned
Flow organization and heat transfer in turbulent wall sheared thermal convection
We perform direct numerical simulations of wall sheared Rayleigh-B\'enard
(RB) convection for Rayleigh numbers up to , Prandtl number unity, and
wall shear Reynolds numbers up to . Using the Monin-Obukhov length
we identify three different flow states, a buoyancy dominated regime
(; with the thermal
boundary layer thickness), a transitional regime (; with the height of the domain), and a shear dominated
regime (). In the buoyancy dominated regime the flow
dynamics are similar to that of turbulent thermal convection. The transitional
regime is characterized by rolls that are increasingly elongated with
increasing shear. The flow in the shear dominated regime consists of very
large-scale meandering rolls, similar to the ones found in conventional Couette
flow. As a consequence of these different flow regimes, for fixed and with
increasing shear, the heat transfer first decreases, due to the breakup of the
thermal rolls, and then increases at the beginning of the shear dominated
regime. For the Nusselt number effectively scales as
, with while we find
in the buoyancy dominated regime. In the transitional regime the effective
scaling exponent is , but the temperature and velocity profiles
in this regime are not logarithmic yet, thus indicating transient dynamics and
not the ultimate regime of thermal convection
Sub-unit cell layer-by-layer growth of Fe3O4, MgO, and Sr2RuO4 thin films
The use of oxide materials in oxide electronics requires their controlled
epitaxial growth. Recently, it was shown that Reflection High Energy Electron
Diffraction (RHEED) allows to monitor the growth of oxide thin films even at
high oxygen pressure. Here, we report the sub-unit cell molecular or block
layer growth of the oxide materials Sr2RuO4, MgO, and magnetite using Pulsed
Laser Deposition (PLD) from stoichiometric targets. Whereas for perovskites
such as SrTiO3 or doped LaMnO3 a single RHEED intensity oscillation is found to
correspond to the growth of a single unit cell, in materials where the unit
cell is composed of several molecular layers or blocks with identical
stoichiometry, a sub-unit cell molecular or block layer growth is established
resulting in several RHEED intensity oscillations during the growth of a single
unit-cell
Logical Dreams
We discuss the past and future of set theory, axiom systems and independence
results. We deal in particular with cardinal arithmetic
Showing Children the Communicative Nature of Reading
This article explores the effects of the classroom learning environment
A General Framework for Sound and Complete Floyd-Hoare Logics
This paper presents an abstraction of Hoare logic to traced symmetric
monoidal categories, a very general framework for the theory of systems. Our
abstraction is based on a traced monoidal functor from an arbitrary traced
monoidal category into the category of pre-orders and monotone relations. We
give several examples of how our theory generalises usual Hoare logics (partial
correctness of while programs, partial correctness of pointer programs), and
provide some case studies on how it can be used to develop new Hoare logics
(run-time analysis of while programs and stream circuits).Comment: 27 page
Manipulating Entitativity Affects Implicit Behavioral and Neural Attentional Biases Toward Gay Couples
This study investigated whether attentional bias toward homosexual couples differs as a function of the manipulation of perceived entitativity, the degree to which group members are perceived to share common values and pursue common goals. Across two experiments, heterosexual college students were randomly assigned to read statements that suggested that homosexual and heterosexual couples were either high or low in entitativity. Following this task, 199 participants completed a dot probe task in Experiment 1 and electroencephalogram (EEG) activity was recorded for 74 participants in Experiment 2 to measure the implicit attentional processing that resulted from viewing pictures of gay, lesbian, and straight couples. Results indicated that participants exposed to low entitativity statements directed less behavioral and neural attention toward gay relative to straight couples compared to those exposed to high entitativity statements. Given the apparent malleability of attentional biases, future research should strive to better understand the factors involved in reducing attentional bias, and by extension, discriminatory behaviors toward minority groups
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