413 research outputs found
Investigations of multiple jets in a crossflow
Study was conducted to determine penetration and mixing characteristics of multiple jets of ambient temperature air injected perpendicularly into ducted mainstream of hot combustion gases
Multiple jet study
Test data is presented which allows determination of jet penetration and mixing of multiple cold air jets into a ducted subsonic heated mainstream flow. Jet-to-mainstream momentum flux ratios ranged from 6 to 60. Temperature profile data is presented at various duct locations up to 24 orifice diameters downstream of the plane of jet injection. Except for two configurations, all geometries investigated had a single row of constant diameter orifices located transverse to the main flow direction. Orifice size and spacing between orifices were varied. Both of these were found to have a significant effect on jet penetration and mixing. The best mixing of the hot and cold streams was achieved with duct height
Technology considerations for main engine specific impulse
Combustion, cooling, nozzle design, and specific impulse prediction for space shuttle main engin
Virtual effects of light gauginos and higgsinos: a precision electroweak analysis of split supersymmetry
We compute corrections to precision electroweak observables in supersymmetry
in the limit that scalar superpartners are very massive and decoupled. This
leaves charginos and neutralinos and a Standard Model-like Higgs boson as the
only states with unknown mass substantially affecting the analysis. We give
complete formulas for the chargino and neutralino contributions, derive simple
analytic results for the pure gaugino and higgsino cases, and study the general
case. We find that in all circumstances, the precision electroweak fit improves
when the charginos and neutralinos are near the current direct limits. Larger
higgsino and gaugino masses worsen the fit as the theory predictions
asymptotically approach those of the Standard Model. Since the Standard Model
is considered by most to be an adequate fit to the precision electroweak data,
an important corollary to our analysis is that all regions of parameter space
allowed by direct collider constraints are also allowed by precision
electroweak constraints in split supersymmetry.Comment: 22 pages, 5 figures, v2: typos fixed and note adde
Suppression of Higgsino mediated proton decay by cancellations in GUTs and strings
A mechanism for the enhancement for proton lifetime in
supersymmetric/supergravity (SUSY/SUGRA) grand unified theories (GUTs) and in
string theory models is discussed where Higgsino mediated proton decay arising
from color triplets (anti-triplets) with charges and
is suppressed by an internal cancellation due to contributions
from different sources. We exhibit the mechanism for an SU(5) model with
Higgs multiplets in addition to the usual Higgs structure of
the minimal model. This model contains both and
Higgs color triplets (anti-triplets) and simple constraints allow for a
complete suppression of Higgsino mediated proton decay. Suppression of proton
decay in an SU(5) model with Planck scale contributions is also considered. The
suppression mechanism is then exhibited for an SO(10) model with a unified
Higgs structure involving representations.The SU(5)
decomposition of contains and
and the cancellation mechanism arises among these
contributions which mirrror the SU(5) case. The cancellation mechanism appears
to be more generally valid for a larger class of unification models.
Specifically the cancellation mechanism may play a role in string model
constructions to suppress proton decay from dimension five operators. The
mechanism allows for the suppression of proton decay consistent with current
data allowing for the possibility that proton decay may be visible in the next
round of nucleon stability experiment.Comment: 26 pages, no figures. Revtex 4. To appear in Physical Review
D-term inflation in non-minimal supergravity
D-term inflation is one of the most interesting and versatile models of
inflation. It is possible to implement naturally D-term inflation within high
energy physics, as for example SUSY GUTs, SUGRA, or string theories. D-term
inflation avoids the -problem, while in its standard form it always ends
with the formation of cosmic strings. Given the recent three-year WMAP data on
the cosmic microwave background temperature anisotropies, we examine whether
D-term inflation can be successfully implemented in non-minimal supergravity
theories. We show that for all our choices of K\"ahler potential, there exists
a parameter space for which the predictions of D-term inflation are in
agreement with the measurements. The cosmic string contribution on the measured
temperature anisotropies is always dominant, unless the superpotential coupling
constant is fine tuned; a result already obtained for D-term inflation within
minimal supergravity. In conclusion, cosmic strings and their r\^ole in the
angular power spectrum cannot be easily hidden by just considering a non-flat
K\"ahler geometry.Comment: 29 pages, 9 figures; minor changes to match publihed versio
High Scale Physics Connection to LHC Data
The existing data appears to provide hints of an underlying high scale
theory. These arise from the gauge coupling unification, from the smallness of
the neutrino masses, and via a non-vanishing muon anomaly. An overview of high
scale models is given with a view to possible tests at the Large Hadron
Collider. Specifically we discuss here some generic approaches to deciphering
their signatures. We also consider an out of the box possibility of a four
generation model where the fourth generation is a mirror generation rather than
a sequential generation. Such a scenario can lead to some remarkably distinct
signatures at the LHC.Comment: 23 pages, no figures. Based on invited lectures at the 46th Course at
the International School of Subnuclear Physics- Erice -Sicily: 29 August -7
September, 200
Stuckelberg Axions and the Effective Action of Anomalous Abelian Models 1. A unitarity analysis of the Higgs-axion mixing
We analyze the quantum consistency of anomalous abelian models and of their
effective field theories, rendered anomaly-free by a Wess-Zumino term, in the
case of multiple abelian symmetries. These models involve the combined
Higgs-Stuckelberg mechanism and predict a pseudoscalar axion-like field that
mixes with the goldstones of the ordinary Higgs sector. We focus our study on
the issue of unitarity of these models both before and after spontaneous
symmetry breaking and detail the set of Ward identities and the organization of
the loop expansion in the effective theory. The analysis is performed on simple
models where we show, in general, the emergence of new effective vertices
determined by certain anomalous interactions.Comment: 67 pages, 26 figures, replaced with revised final version, to appear
on JHE
Erasmus MC at CLEF eHealth 2016: Concept recognition and coding in French texts
We participated in task 2 of the CLEF eHealth 2016 chal-lenge. Two subtasks were addressed: entity recognition and normalization in a corpus of French drug labels and Medline titles, and ICD-10 coding of French death certificates. For both subtasks we used a dictionary-based approach. For entity recognition and normalization, we used Peregrine, our open-source indexing engine, with a dictionary based on French terms in the Unified Medical Language System (UMLS) supplemented with English UMLS terms that were translated into French with automatic translators. For ICD-10 coding, we used the Solr text tagger, together with one of two ICD-10 terminologies derived from the task training ma-terial. To reduce the number of false-positive detections, we implemented several post-processing steps. On the challenge test set, our best system obtained F-scores of 0.702 and 0.651 fo
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