810 research outputs found
Prediction of transonic flutter for a supercritical wing by modified strip analysis and comparison with experiment
Use of a supercritical airfoil can adversely affect wing flutter speeds in the transonic range. As adequate theories for three dimensional unsteady transonic flow are not yet available, the modified strip analysis was used to predict the transonic flutter boundary for the supercritical wing. The steady state spanwise distributions of section lift curve slope and aerodynamic center, required as input for the flutter calculations, were obtained from pressure distributions. The calculated flutter boundary is in agreement with experiment in the subsonic range. In the transonic range, a transonic bucket is calculated which closely resembles the experimental one with regard to both shape and depth, but it occurs at about 0.04 Mach number lower than the experimental one
The High-Resolution Structures of the Neutral and the Low pH Crystals of Aminopeptidase from \u3cem\u3eAeromonas proteolytica\u3c/em\u3e
The aminopeptidase from Aeromonas proteolytica (AAP) contains two zinc ions in the active site and catalyzes the degradation of peptides. Herein we report the crystal structures of AAP at 0.95-Ã… resolution at neutral pH and at 1.24-Ã… resolution at low pH. The combination of these structures allowed the precise modeling of atomic positions, the identification of the metal bridging oxygen species, and insight into the physical properties of the metal ions. On the basis of these structures, a new putative catalytic mechanism is proposed for AAP that is likely relevant to all binuclear metalloproteases
Giant Magnetic Moments of Nitrogen Stabilized Mn Clusters and Their Relevance to Ferromagnetism in Mn Doped GaN
Using first principles calculations based on density functional theory, we
show that the stability and magnetic properties of small Mn clusters can be
fundamentally altered by the presence of nitrogen. Not only are their binding
energies substantially enhanced, but also the coupling between the magnetic
moments at Mn sites remains ferromagnetic irrespective of their size or shape.
In addition, these nitrogen stabilized Mn clusters carry giant magnetic moments
ranging from 4 Bohr magnetons in MnN to 22 Bohr magnetons in Mn_5N. It is
suggested that the giant magnetic moments of Mn_xN clusters may play a key role
in the ferromagnetism of Mn doped GaN which exhibit a wide range (10K - 940K)
of Curie temperatures
Subsonic aerodynamic and flutter characteristics of several wings calculated by the SOUSSA P1.1 panel method
The SOUSSA (steady, oscillatory, and unsteady subsonic and supersonic aerodynamics) program is the computational implementation of a general potential flow analysis (by the Green's function method) that can generate pressure distributions on complete aircraft having arbitrary shapes, motions and deformations. Some applications of the initial release version of this program to several wings in steady and oscillatory motion, including flutter are presented. The results are validated by comparisons with other calculations and experiments. Experiences in using the program as well as some recent improvements are described
Alloprof: a new French question-answer education dataset and its use in an information retrieval case study
Teachers and students are increasingly relying on online learning resources
to supplement the ones provided in school. This increase in the breadth and
depth of available resources is a great thing for students, but only provided
they are able to find answers to their queries. Question-answering and
information retrieval systems have benefited from public datasets to train and
evaluate their algorithms, but most of these datasets have been in English text
written by and for adults. We introduce a new public French question-answering
dataset collected from Alloprof, a Quebec-based primary and high-school help
website, containing 29 349 questions and their explanations in a variety of
school subjects from 10 368 students, with more than half of the explanations
containing links to other questions or some of the 2 596 reference pages on the
website. We also present a case study of this dataset in an information
retrieval task. This dataset was collected on the Alloprof public forum, with
all questions verified for their appropriateness and the explanations verified
both for their appropriateness and their relevance to the question. To predict
relevant documents, architectures using pre-trained BERT models were fine-tuned
and evaluated. This dataset will allow researchers to develop
question-answering, information retrieval and other algorithms specifically for
the French speaking education context. Furthermore, the range of language
proficiency, images, mathematical symbols and spelling mistakes will
necessitate algorithms based on a multimodal comprehension. The case study we
present as a baseline shows an approach that relies on recent techniques
provides an acceptable performance level, but more work is necessary before it
can reliably be used and trusted in a production setting
Dev2vec: Representing Domain Expertise of Developers in an Embedding Space
Accurate assessment of the domain expertise of developers is important for
assigning the proper candidate to contribute to a project or to attend a job
role. Since the potential candidate can come from a large pool, the automated
assessment of this domain expertise is a desirable goal. While previous methods
have had some success within a single software project, the assessment of a
developer's domain expertise from contributions across multiple projects is
more challenging. In this paper, we employ doc2vec to represent the domain
expertise of developers as embedding vectors. These vectors are derived from
different sources that contain evidence of developers' expertise, such as the
description of repositories that they contributed, their issue resolving
history, and API calls in their commits. We name it dev2vec and demonstrate its
effectiveness in representing the technical specialization of developers. Our
results indicate that encoding the expertise of developers in an embedding
vector outperforms state-of-the-art methods and improves the F1-score up to
21%. Moreover, our findings suggest that ``issue resolving history'' of
developers is the most informative source of information to represent the
domain expertise of developers in embedding spaces.Comment: 30 pages, 5 figure
Scholar-activists in an expanding European food sovereignty movement
This article analyzes the roles, relations, and positions of scholar-activists in the European food sovereignty movement. In doing so, we document, make visible and question the political dimensions of researchers' participation in the movement. We argue that scholar-activists are part of the movement, but are distinct from the affected constituencies, put in place to ensure adequate representation of key movement actors. This is because scholar-activists lack a collective identity, have no processes to formulate collective demands, and no mechanisms for inter-researcher and researchers-movement communication. We reflect on whether and how scholar-activists could organize, and discuss possible pathways for a more cohesive and stronger researcher engagement in the movement.</p
Teaching in groups in grade III.
Thesis (Ed.M.)--Boston University
N.B.:Pages 28, 144 and 145 are missing from original thesis
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