4,338 research outputs found
Flow-Control Effectiveness of Convergent Surface Indentations on an Aerofoil at Low Reynolds Numbers
Passive flow control on aerofoils has largely been achieved through the use of protrusions
such as vane-type vortex generators. Consequently, innovative flow-control concepts should
be explored in an effort to improve current component performance. Therefore,
experimental research has been performed at The University of Manchester to evaluate the
flow-control effectiveness of a novel type of vortex generator made in the form of a surface
indentation. The surface indentation has a trapezoidal planform. A spanwise array of
indentations has been applied in a convergent orientation around the maximum-thickness
location of the upper surface of a NACA-0015 aerofoil. The aerofoil has been tested in a twodimensional
set-up in a low-speed wind tunnel at an angle of attack (AoA) of 3° and a chordbased
blockage-corrected Reynolds number (Recorr) of ~2.70 x 105
. The baseline model has
been found to suffer from a long laminar separation bubble (LSB) at low AoA. The
application of the indentations at low AoA has considerably shortened the separation
bubble. The indentations achieve this by shedding up-flow pairs of streamwise vortices.
Despite the considerable reduction in bubble length, the increase in leading-edge suction due
to the shorter bubble is limited by the removal of surface curvature and blockage (increase
in surface pressure) caused locally by the convergent indentations. Furthermore, the up-flow
region of the vortices, which locally weakens the pressure recovery around the trailing edge
of the aerofoil by thickening the boundary layer, also contributes to this limitation. Due to
the conflicting effects of the indentations, the changes in the pressure-lift and pressure-drag
coefficients, i.e., cl,p and cd,p, respectively, are small. Nevertheless, the indentations have
improved cl,p and cd,p beyond the uncertainty range, i.e., by ~1.3% and ~0.3%, respectively,
at 3° AoA. The wake measurements show that turbulence intensity and Reynolds stresses
have considerably increased in the indented case, thus implying that the indentations
increase the viscous drag on the model. In summary, the convergent indentations are able to
reduce the size of the LSB, but conversely, they are not highly effective in enhancing cl,p and
cd,p at the tested Re
Graded Fock--like representations for a system of algebraically interacting paraparticles
We will present an algebra describing a mixed paraparticle model, known in
the bibliography as "The Relative Parabose Set (\textsc{Rpbs})". Focusing in
the special case of a single parabosonic and a single parafermionic degree of
freedom , we will study a class of Fock--like representations
of this algebra, dependent on a positive integer parameter p (a kind of
generalized parastatistics order). Mathematical properties of the Fock--like
modules will be investigated for all values of p and constructions such as
ladder operators, irreducibility (for the carrier spaces) and Klein group
gradings (for both the carrier spaces and the algebra itself) will be
established.Comment: 4 pages, 1 ref. updated with respect to the journ. versio
Hyperthermal neutral beam etching
A pulsed beam of hyperthermal fluorine atoms with an average translational energy of 4.8 eV has been used to demonstrate anisotropic etching of Si. For 1.4 Hz operation, a room-temperature etch rate of 300 Å/min for Si(100) has been measured at a distance of 30 cm from the source. A 14% undercutting for room-temperature etching of Novolac-masked Si features was achieved under single-collision conditions, with no detectable mask erosion. Translational energy and angular distributions of scattered fluorine atoms during steady-state etching of Si by a normal-incidence, collimated beam demonstrate that unreacted F atoms can scatter inelastically, retaining a significant fraction of their initial kinetic energies. The observed undercutting can be explained by secondary impingement of these high-energy F atoms, which are more reactive upon interaction with the sidewalls than would be expected if they desorbed from the surface at thermal energies after full accommodation. Time-of-flight distributions of volatile reaction products were also collected, and they show evidence for a dominant nonthermal reaction mechanism of the incident atoms with the surface in addition to a thermal reaction channel
The C-terminal portion of the cleaved HT motif is necessary and sufficient to mediate export of proteins from the malaria parasite into its host cell
The malaria parasite exports proteins across its plasma membrane and a surrounding parasitophorous vacuole membrane, into its host erythrocyte. Most exported proteins contain a Host Targeting motif (HT motif) that targets them for export. In the parasite secretory pathway, the HT motif is cleaved by the protease plasmepsin V, but the role of the newly generated N-terminal sequence in protein export is unclear. Using a model protein that is cleaved by an exogenous viral protease, we show that the new N-terminal sequence, normally generated by plasmepsin V cleavage, is sufficient to target a protein for export, and that cleavage by plasmepsin V is not coupled directly to the transfer of a protein to the next component in the export pathway. Mutation of the fourth and fifth positions of the HT motif, as well as amino acids further downstream, block or affect the efficiency of protein export indicating that this region is necessary for efficient export. We also show that the fifth position of the HT motif is important for plasmepsin V cleavage. Our results indicate that plasmepsin V cleavage is required to generate a new N-terminal sequence that is necessary and sufficient to mediate protein export by the malaria parasite
DoctorEye: A clinically driven multifunctional platform, for accurate processing of tumors in medical images
Copyright @ Skounakis et al.This paper presents a novel, open access interactive platform for 3D medical image analysis, simulation and visualization, focusing in oncology images. The platform was developed through constant interaction and feedback from expert clinicians integrating a thorough analysis of their requirements while having an ultimate goal of assisting in accurately delineating tumors. It allows clinicians not only to work with a large number of 3D tomographic datasets but also to efficiently annotate multiple regions of interest in the same session. Manual and semi-automatic segmentation techniques combined with integrated correction tools assist in the quick and refined delineation of tumors while different users can add different components related to oncology such as tumor growth and simulation algorithms for improving therapy planning. The platform has been tested by different users and over large number of heterogeneous tomographic datasets to ensure stability, usability, extensibility and robustness with promising results. AVAILABILITY: THE PLATFORM, A MANUAL AND TUTORIAL VIDEOS ARE AVAILABLE AT: http://biomodeling.ics.forth.gr. It is free to use under the GNU General Public License
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