126,625 research outputs found
Inconsistency in 9 mm bullets : correlation of jacket thickness to post-impact geometry measured with non-destructive X-ray computed tomography
Fundamental to any ballistic armour standard is the reference projectile to be defeated. Typically, for certification purposes, a consistent and symmetrical bullet geometry is assumed, however variations in bullet jacket dimensions can have far reaching consequences. Traditionally, characteristics and internal dimensions have been analysed by physically sectioning bullets – an approach which is of restricted scope and which precludes subsequent ballistic assessment. The use of a non-destructive X-ray computed tomography (CT) method has been demonstrated and validated Kumar et al., 2011); the authors now apply this technique to correlate bullet impact response with jacket thickness variations. A set of 20 bullets (9 mm DM11) were selected for comparison and an image-based analysis method was employed to map jacket thickness and determine the centre of gravity of each specimen. Both intra- and inter-bullet variations were investigated, with thickness variations of the order of 200 um commonly found along the length of all bullets and angular variations of up to 50 um in some. The bullets were subsequently impacted against a rigid flat plate under controlled conditions (observed on a high-speed video camera) and the resulting deformed projectiles were re-analysed. The results of the experiments demonstrate a marked difference in ballistic performance between bullets from different manufacturers and an asymmetric thinning of the jacket is observed in regions of pre-impact weakness. The conclusions are relevant for future soft armour standards and provide important quantitative data for numerical model correlation and development. The implications of the findings of the work on the reliability and repeatability of the industry standard V50 ballistic test are also discussed
SINDA/SINFLO computer routine, volume 1, revision A
The SINFLO package was developed to modify the SINDA preprocessor to accept and store the input data for fluid flow systems analysis and adding the FLOSOL user subroutine to perform the flow solution. This reduced and simplified the user input required for analysis of flow problems. A temperature calculation method, the flow-hybrid method which was developed in previous VSD thermal simulator routines, was incorporated for calculating fluid temperatures. The calculation method accuracy was improved by using fluid enthalpy rather than specific heat for the convective term of the fluid temperature equation. Subroutines and data input requirements are described along with user subroutines, flow data storage, and usage of the plot program
Charge Detection in Phosphorus-doped Silicon Double Quantum Dots
We report charge detection in degenerately phosphorus-doped silicon double
quantum dots (DQD) electrically connected to an electron reservoir. The sensing
device is a single electron transistor (SET) patterned in close proximity to
the DQD. Measurements performed at 4.2K show step-like behaviour and shifts of
the Coulomb Blockade oscillations in the detector's current as the reservoir's
potential is swept. By means of a classical capacitance model, we demonstrate
that the observed features can be used to detect single-electron tunnelling
from, to and within the DQD, as well as to reveal the DQD charge occupancy.Comment: 4 pages, 3 figure
Kinetic Monte Carlo simulations inspired by epitaxial graphene growth
Graphene, a flat monolayer of carbon atoms packed tightly into a two
dimensional hexagonal lattice, has unusual electronic properties which have
many promising nanoelectronic applications. Recent Low Energy Electron
Microscopy (LEEM) experiments show that the step edge velocity of epitaxially
grown 2D graphene islands on Ru(0001) varies with the fifth power of the
supersaturation of carbon adatoms. This suggests that graphene islands grow by
the addition of clusters of five atoms rather than by the usual mechanism of
single adatom attachment.
We have carried out Kinetic Monte Carlo (KMC) simulations in order to further
investigate the general scenario of epitaxial growth by the attachment of
mobile clusters of atoms. We did not seek to directly replicate the Gr/Ru(0001)
system but instead considered a model involving mobile tetramers of atoms on a
square lattice. Our results show that the energy barrier for tetramer break up
and the number of tetramers that must collide in order to nucleate an immobile
island are the important parameters for determining whether, as in the
Gr/Ru(0001) system, the adatom density at the onset of island nucleation is an
increasing function of temperature. A relatively large energy barrier for
adatom attachment to islands is required in order for our model to produce an
equilibrium adatom density that is a large fraction of the nucleation density.
A large energy barrier for tetramer attachment to islands is also needed for
the island density to dramatically decrease with increasing temperature. We
show that islands grow with a velocity that varies with the fourth power of the
supersaturation of adatoms when tetramer attachment is the dominant process for
island growth
The open cluster initial-final mass relationship and the high-mass tail of the white dwarf distribution
Recent studies of white dwarfs in open clusters have provided new constraints
on the initial - final mass relationship (IFMR) for main sequence stars with
masses in the range 2.5 - 6.5 Mo. We re-evaluate the ensemble of data that
determines the IFMR and argue that the IFMR can be characterised by a mean
initial-final mass relationship about which there is an intrinsic scatter. We
investigate the consequences of the IFMR for the observed mass distribution of
field white dwarfs using population synthesis calculations. We show that while
a linear IFMR predicts a mass distribution that is in reasonable agreement with
the recent results from the PG survey, the data are better fitted by an IFMR
with some curvature. Our calculations indicate that a significant (~28%)
percentage of white dwarfs originating from single star evolution have masses
in excess of ~0.8 Mo, obviating the necessity for postulating the existence of
a dominant population of high-mass white dwarfs that arise from binary star
mergers.Comment: 5 pages, 2 color Postscript figures. Accepted for publication in
MNRA
Assessing the Effectiveness of Automated Emotion Recognition in Adults and Children for Clinical Investigation
Recent success stories in automated object or face recognition, partly fuelled by deep learning artificial neural network (ANN) architectures, has led to the advancement of biometric research platforms and, to some extent, the resurrection of Artificial Intelligence (AI). In line with this general trend, inter-disciplinary approaches have taken place to automate the recognition of emotions in adults or children for the benefit of various applications such as identification of children emotions prior to a clinical investigation. Within this context, it turns out that automating emotion recognition is far from being straight forward with several challenges arising for both science(e.g., methodology underpinned by psychology) and technology (e.g., iMotions biometric research platform). In this paper, we present a methodology, experiment and interesting findings, which raise the following research questions for the recognition of emotions and attention in humans: a) adequacy of well-established techniques such as the International Affective Picture System (IAPS), b) adequacy of state-of-the-art biometric research platforms, c) the extent to which emotional responses may be different among children or adults. Our findings and first attempts to answer some of these research questions, are all based on a mixed sample of adults and children, who took part in the experiment resulting into a statistical analysis of numerous variables. These are related with, both automatically and interactively, captured responses of participants to a sample of IAPS pictures
Theoretical calculations of radiant heat transfer properties of particle-seeded gases
Radiant heat transfer properties of particle seeded gases, including absorption and scattering characteristics of carbon, silicon, and tungste
The ALMA Early Science View of FUor/EXor objects. III. The Slow and Wide Outflow of V883 Ori
We present Atacama Large Millimeter/ sub-millimeter Array (ALMA) observations
of V883 Ori, an FU Ori object. We describe the molecular outflow and envelope
of the system based on the CO and CO emissions, which together
trace a bipolar molecular outflow. The CO emission traces the rotational
motion of the circumstellar disk. From the CO blue-shifted emission, we
estimate a wide opening angle of 150 for the outflow
cavities. Also, we find that the outflow is very slow (characteristic velocity
of only 0.65 km~s), which is unique for an FU Ori object. We calculate
the kinematic properties of the outflow in the standard manner using the
CO and CO emissions. In addition, we present a P Cygni profile
observed in the high-resolution optical spectrum, evidence of a wind driven by
the accretion and being the cause for the particular morphology of the
outflows. We discuss the implications of our findings and the rise of these
slow outflows during and/or after the formation of a rotationally supported
disk.Comment: 12 pages, 7 figures, 2 tables. Accepte
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