887 research outputs found
Fostering Academic Writersâ Plurilingual Voices
In today's global society, a majority of academic writers come from diverse linguistic backgrounds, where English is an additional language. Publishing in most academic journals, however, is governed by native-English norms. As instructors and tutors guiding novice plurilingual writers through these conventions so that their papers meet publishing standards, we feel that their voices and styles get lost in the process, and fear that the academic and scientific community may be losing out when these writers' work is not accepted. To understand how plurilingual novice writers experience writing for publication, we conducted in-depth interviews, followed by a content analysis of the interviews, which revealed recurring themes relating to barriers and gains from writing in English. We present these along with exemplary quotes from the respondents. Additionally, we examine the ways in which the publication world is changing and how these changes can aid novice writers, as well as consider ways in which academic writing boundaries can become more elastic and inclusive.
 
Physically founded phonon dispersions of few-layer materials, and the case of borophene
An increasing number of theoretical calculations on few-layer materials have
been reporting a non-zero sound velocity for all three acoustic phonon modes.
In contrast with these reports, here we show that the lowest phonon dispersion
branch of atomistically described few-layer materials should be quadratic, and
this can have dramatic consequencies on calculated properties, such as the
thermal conductivity. By reformulating the interatomic force constants (IFC) in
terms of internal coordinates, we find that a delicate balance between the IFCs
is responsible for this quadraticity. This balance is hard to obtain in
ab-initio calculations even if all the symmetries are numerically enforced a
posteriori, but it arises naturally in our approach. We demonstrate the
phenomenon in the case of borophene, where a very subtle correction to the
ab-initio IFCs yields the physically correct quadratic dispersion, while
leaving the rest of the spectrum virtually unmodified. Such quadraticity
nevertheless has a major effect on the computed lattice thermal conductivity,
which in the case of borophene changes by more than a factor 2, and reverses
its anisotropy, when the subtle IFC correction is put in place
Phonon-Phonon Interactions in Strongly Bonded Solids: Selection Rules and Higher-Order Processes
We show that the commonly used lowest-order theory of phonon-phonon
interactions frequently fails to accurately describe the anharmonic phonon
decay rates and thermal conductivity (), even among strongly bonded
crystals. Applying a first principles theory that includes both the
lowest-order three-phonon and the higher-order four-phonon processes to
seventeen zinc blende semiconductors, we find that the lowest-order theory
drastically overestimates the measured for many of these materials,
while inclusion of four-phonon scattering gives significantly improved
agreement with measurements. We have identified new selection rules on
three-phonon processes that help explain many of these failures in terms of
anomalously weak anharmonic phonon decay rates predicted by the lowest-order
theory competing with four-phonon processes. We also show that zinc blende
compounds containing boron (B), carbon (C) or nitrogen (N) atoms have
exceptionally weak four-phonon scattering, much weaker than in compounds that
do not contain B, C or N atoms. This new understanding helps explain the
ultrahigh in several technologically important materials like cubic
boron arsenide, boron phosphide and silicon carbide. At the same time, it not
only makes the possibility of achieving high in materials without B, C
or N atoms unlikely, but it also suggests that it may be necessary to include
four-phonon processes in many future studies. Our work gives new insights into
the nature of anharmonic processes in solids and demonstrates the broad
importance of higher-order phonon-phonon interactions in assessing the thermal
properties of materials.Comment: 18 pages, 7 figure
Development of an Ada package library
A usable prototype Ada package library was developed and is currently being evaluated for use in large software development efforts. The library system is comprised of an Ada-oriented design language used to facilitate the collection of reuse information, a relational data base to store reuse information, a set of reusable Ada components and tools, and a set of guidelines governing the system's use. The prototyping exercise is discussed and the lessons learned from it have led to the definition of a comprehensive tool set to facilitate software reuse
Covariant three-body equations in phi^3 field theory
We derive four-dimensional relativistic three-body equations for the case of
a field theory with a three-point interaction vertex. These equations describe
the coupled 2->2, 2->3, and 3->3 processes, and provide the means of
calculating the kernel of the 2->2 Bethe-Salpeter equation. Our equations
differ from all previous formulations in two essential ways. Firstly, we have
overcome the overcounting problems inherent in earlier works. Secondly, we have
retained all possible two-body forces when one particle is a spectator. In this
respect, we show how it is necessary to also retain certain three-body forces
as these can give rise to (previously overlooked) two-body forces when used in
a 2->3 process. The revealing of such hidden two-body forces gives rise to a
further novel feature of our equations, namely, to the appearance of a number
of subtraction terms. In the case of the piNN system, for example, the NN
potential involves a subtraction term where two pions, exchanged between the
nucleons, interact with each other through the pi-pi t-matrix. The necessity of
an input pi-pi interaction is surprising and contrasts markedly with the
corresponding three-dimensional description of the piNN system where no such
interaction explicitly appears. This illustrates the somewhat unexpected result
that the four-dimensional equations differ from the three-dimensional ones even
at the operator level.Comment: 33, FIAS-R-22
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