1,330 research outputs found
Influence of base modifications on in-flight base drag in the presence of jet exhaust for Mach numbers from 0.7 to 1.5
The use of external modifications in the base region to reduce the base drag of a blunt-base body in the presence of jet engine exhaust was investigated in flight. Base pressure data were obtained for the following configurations: (1) blunt base; (2) blunt base modified with splitter plate; and (3) blunt base modified with two variations of a vented cavity. Reynolds number based on the length of the aircraft ranged from 1.2 to 3.1 x 10 to the 8th. Mach number M ranges were 0.71 less than or = M less than or = 0.95 and 1.10 less than or = M less than or = 1.51. The data were analyzed using the blunt base for a reference, or baseline condition. For 1.10 less than or = M less than or = 1.51, the reduction in base drag coefficient provided by the vented cavity configuration ranged from 0.07 to 0.05. These increments in base drag coefficient at M = 1.31 and 1.51 result in base drag reductions of 27 and 24 percent, respectively, when compared to the blunt base drag. For M less than 1, the drag increment between the blunt base and the modification is not significant
Flight tests of external modifications used to reduce blunt base drag
The effectiveness of a trailing disk (the trapped vortex concept) in reducing the blunt base drag of an 8-in diameter body of revolution was studied from measurements made both in flight and in full-scale wind-tunnel tests. The experiment demonstrated the significant base drag reduction capability of the trailing disk to Mach 0.93. The maximum base drag reduction obtained from a cavity tested on the flight body of revolution was not significant. The effectiveness of a splitter plate and a vented-wall cavity in reducing the base drag of a quasi-two-dimensional fuselage closure was studied from base pressure measurements made in flight. The fuselage closure was between the two engines of the F-111 airplane; therefore, the base pressures were in the presence of jet engine exhaust. For Mach numbers from 1.10 to 1.51, significant base drag reduction was provided by the vented-wall cavity configuration. The splitter plate was not considered effective in reducing base drag at any Mach number tested
Sticky Prices vs. Sticky Information – A Cross-Country Study of Inflation Dynamics
This paper empirically compares sticky-price and sticky-information Phillips curves considering inflation dynamics in six countries (US, UK, Germany, France, Canada, and Japan). We evaluate the models‘ abilities to match empirical second moments of inflation. Under baseline calibrations, the two models perform similarly in almost all countries. Under estimated parametrizations, sticky information performs better in France while sticky prices dominate in the UK and Germany. Sticky prices match unconditional moments of inflation dynamics better while sticky information is more successful in matching co-movement of inflation with demand. Both models‘ performances worsen where inflation dynamics diff er from the US benchmark.Phillips curve; sticky information; sticky prices
A fresh look at hadronic light-by-light scattering in the muon g-2 with the Dyson-Schwinger approach
We present first results for the hadronic light-by-light scattering
contribution to the anomalous magnetic moment of the muon a_{\mu} in the
framework of Dyson-Schwinger and Bethe-Salpeter equations. We determine the
quark loop and pseudoscalar ({\pi}^0, {\eta}, {\eta}') meson exchange diagram
using a phenomenological model for the combined strength of the gluon
propagator and the quark-gluon interaction as the only input. Our result for
meson exchange, a_{\mu}^{LBL;PS}=(84 \pm 13) x 10^{-11}, is commensurate with
previous calculations. However, our number for the quark loop contribution,
a_{\mu}^{LBL;quarkloop} = (107 \pm 2 \pm 46) x 10^{-11}, is significantly
larger due to dressing effects in the quark propagator and the quark-photon
vertex. Taken at face value, this then leads to a revised estimate of the total
a_{\mu}=116 591 865.0(96.6) x 10^{-11}, which reduces the difference between
theory and experiment to about 1.9 {\sigma}.Comment: 5 pages, 7 figures, v2: title slightly changed, minor corrections,
version accepted by EP
Beyond Rainbow-Ladder in bound state equations
In this work we devise a new method to study quark anti-quark interactions
beyond simple ladder-exchange that yield massless pions in the chiral limit.
The method is based on the requirement to have a representation of the
quark-gluon vertex that is explicitly given in terms of quark dressings
functions. We outline a general procedure to generate the Bethe-Salpeter kernel
for a given vertex representation. Our method allows not only the
identification of the mesons' masses but also the extraction of their
Bethe-Salpeter wave functions exposing their internal structure. We exemplify
our method with vertex models that are of phenomenological interest.Comment: 13 pages, 6 figures; v2: typos corrected, colors improve
The role of momentum dependent dressing functions and vector meson dominance in hadronic light-by-light contributions to the muon g-2
We present a refined calculation of the quark-loop contribution to hadronic
light-by-light scatter- ing that focuses upon the impact of the transverse
components of the quark-photon vertex. These structures are compared and
contrasted with those found within the extended NJL-models. We discuss
similarities and differences between the two approaches and further clarify the
important role of momentum dependent dressing functions. As expected we find
that the transverse structures of the quark-photon vertex lead to a suppression
of the quark-loop contribution to the anomalous magnetic moment of the muon.
However, we find evidence that this suppression is overestimated within models
with simple approximations for the quark-photon interaction.Comment: 13 pages, 5 figures, v2: typos corrected, references added, version
submitted to PR
Linear Facial Expression Transfer With Active Appearance Models
The issue of transferring facial expressions from one person's face to another's has been an area of interest for the movie industry and the computer graphics community for quite some time. In recent years, with the proliferation of online image and video collections and web applications, such as Google Street View, the question of preserving privacy through face de-identification has gained interest in the computer vision community. In this paper, we focus on the problem of real-time dynamic facial expression transfer using an Active Appearance Model framework. We provide a theoretical foundation for a generalisation of two well-known expression transfer methods and demonstrate the improved visual quality of the proposed linear extrapolation transfer method on examples of face swapping and expression transfer using the AVOZES data corpus. Realistic talking faces can be generated in real-time at low computational cost
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