2,841 research outputs found
PC-based aviation training devices (PCATDs): research, development and certification
This paper examines the development of two PCATDâs (one
helicopter, one fixed-wing) and their eventual certification by CAA.
Certification has demonstrated the potential these devices have for aviation
training in New Zealand. Traditionally FTDâs and PCATDâs have been
sourced from foreign companies, and they represent a considerable financial
investment for large flying training organisations. The procurement of these
simulator types is generally beyond the financial resources of most small to
medium sized flying schools. Aviation training in NZ is facing significant
financial constraints as well as an increasing demand to simulate complex
glass cockpit systems that are now installed in most new General Aviation
(GA) aircraft. The development, utilisation and certification of this type of
PCATD technology could solve these difficult challenges
Characteristics of the wavelength of ripples on icicles
It is known that the wavelength of the ripples on icicles in nature is of
centimeter-scale. Such study on morphological instability of ice-water
interface during ice growth from flowing supercooled water film with one side
being a free surface has recently been made [K. Ueno, Phys. Rev. E 68, 021603
(2003)]. This is a first theoretical study taking into account the influence of
the shape of the water-air surface on the growth condition of infinitesimal
disturbances of the ice-water interface. A simpler formula to determine the
wavelength of the ripples than that in the previous paper is derived. It seems
that the wavelength of ripples is insensitive to the water supply rates,
diameters of the icicles and surrounding air temperatures. The details of
dependence of the wavelengh of ripples on these parameters are investigated.Comment: 15 pages, 6 figure
Determining the Angle of Impact from the Analysis of Bullets Following Perforation with Glass
When two objects come into contact with one another, there is a potential for the transfer of material between those objects. The goal of this research was to develop statistical models to aid investigators in the reconstruction of a shooting incident. Specifically, the determination of the direction of fire from the angle of impact of the bullet was addressed by assessing the deformation of the bullet and the transfer of glass onto the bullet. Transfer of material to bullets is an underexploited area of trace evidence. Current research has mainly been observational and no attempt has been made to provide a quantitative measure to the results. Four aspects of bullet deformation after perforation of a glass target were studied during the research: (1) the shape of the bullet holes, (2) the side view of bullet deformation, (3) the frontal view of bullet deformation, and (4) the distribution of glass onto the bullets. A Ruger SR9 9mm pistol was used to fire 100 cartridges at individual glass samples at angles of 45°, 50°, 60°, 75°, and 90° using full metal jacket and lead round nose ammunition. The following methodologies were employed for image capture and analysis: (1) focus stacking was used to generate high-quality images of the frontal view of the bullet, (2) analysis of the bullet holes in the glass targets using HemoSpat, (3) analysis of bullet deformation and distribution of glass onto bullets using ImageJ. Regression modeling and principal component analysis were performed on the data. The research found that examining bullet holes in glass is not a viable method for determining angle of impact. It also found that the side view deformation of full metal jacket bullets can be used to distinguish between some impact angles, for example, 90° and 65°, but cannot be used for lead round nose bullets. Furthermore, the front view deformation and distribution of glass on full metal jacket bullets can be used to distinguish between some impact angles, for example, 75° and 50°, but cannot be used for lead round nose bullets
Might EPR particles communicate through a wormhole?
We consider the two-particle wave function of an Einstein-Podolsky-Rosen
system, given by a two dimensional relativistic scalar field model. The Bohm-de
Broglie interpretation is applied and the quantum potential is viewed as
modifying the Minkowski geometry. In this way an effective metric, which is
analogous to a black hole metric in some limited region, is obtained in one
case and a particular metric with singularities appears in the other case,
opening the possibility, following Holland, of interpreting the EPR
correlations as being originated by an effective wormhole geometry, through
which the physical signals can propagate.Comment: Corrected version, to appears in EP
Yersinia ruckeri isolates recovered from diseased Atlantic Salmon (Salmo salar) in Scotland are more diverse than those from Rainbow Trout (Oncorhynchus mykiss) and represent distinct subpopulations
Yersinia ruckeri is the etiological agent of enteric redmouth (ERM) disease of farmed salmonids. Enteric redmouth disease is traditionally associated with rainbow trout (Oncorhynchus mykiss, Walbaum), but its incidence in Atlantic salmon (Salmo salar) is increasing. Yersinia ruckeri isolates recovered from diseased Atlantic salmon have been poorly characterized, and very little is known about the relationship of the isolates associated with these two species. Phenotypic approaches were used to characterize 109 Y. ruckeri isolates recovered over a 14-year period from infected Atlantic salmon in Scotland; 26 isolates from infected rainbow trout were also characterized. Biotyping, serotyping, and comparison of outer membrane protein profiles identified 19 Y. ruckeri clones associated with Atlantic salmon but only five associated with rainbow trout; none of the Atlantic salmon clones occurred in rainbow trout and vice versa. These findings suggest that distinct subpopulations of Y. ruckeri are associated with each species. A new O serotype (designated O8) was identified in 56 biotype 1 Atlantic salmon isolates and was the most common serotype identified from 2006 to 2011 and in 2014, suggesting an increased prevalence during the time period sampled. Rainbow trout isolates were represented almost exclusively by the same biotype 2, serotype O1 clone that has been responsible for the majority of ERM outbreaks in this species within the United Kingdom since the 1980s. However, the identification of two biotype 2, serotype O8 isolates in rainbow trout suggests that vaccines containing serotypes O1 and O8 should be evaluated in both rainbow trout and Atlantic salmon for application in Scotland
How to construct spin chains with perfect state transfer
It is shown how to systematically construct the quantum spin chains with
nearest-neighbor interactions that allow perfect state transfer (PST). Sets of
orthogonal polynomials (OPs) are in correspondence with such systems. The key
observation is that for any admissible one-excitation energy spectrum, the
weight function of the associated OPs is uniquely prescribed. This entails the
complete characterization of these PST models with the mirror symmetry property
arising as a corollary. A simple and efficient algorithm to obtain the
corresponding Hamiltonians is presented. A new model connected to a special
case of the symmetric -Racah polynomials is offered. It is also explained
how additional models with PST can be derived from a parent system by removing
energy levels from the one-excitation spectrum of the latter. This is achieved
through Christoffel transformations and is also completely constructive in
regards to the Hamiltonians.Comment: 7 page
Vertical force production in soccer: mechanical aspects and applied training strategies
Vertical force production (VFP) is widely recognized as a critical determinant of performance in a series of soccer-specific activities, such as sprinting, jumping, and changing direction. Therefore, practitioners are constantly seeking better and more effective strategies to improve VFP in professional soccer players. This article analyzes the mechanical aspects associated with the actual role played by VFP in elite soccer, and also examines and highlights the training considerations related to its appropriate and effective development during modern soccer seasons
Extended Heat-Fluctuation Theorems for a System with Deterministic and Stochastic Forces
Heat fluctuations over a time \tau in a non-equilibrium stationary state and
in a transient state are studied for a simple system with deterministic and
stochastic components: a Brownian particle dragged through a fluid by a
harmonic potential which is moved with constant velocity. Using a Langevin
equation, we find the exact Fourier transform of the distribution of these
fluctuations for all \tau. By a saddle-point method we obtain analytical
results for the inverse Fourier transform, which, for not too small \tau, agree
very well with numerical results from a sampling method as well as from the
fast Fourier transform algorithm. Due to the interaction of the deterministic
part of the motion of the particle in the mechanical potential with the
stochastic part of the motion caused by the fluid, the conventional heat
fluctuation theorem is, for infinite and for finite \tau, replaced by an
extended fluctuation theorem that differs noticeably and measurably from it. In
particular, for large fluctuations, the ratio of the probability for absorption
of heat (by the particle from the fluid) to the probability to supply heat (by
the particle to the fluid) is much larger here than in the conventional
fluctuation theorem.Comment: 23 pages, 6 figures. Figures are now in color, Eq. (67) was corrected
and a footnote was added on the d-dimensional cas
Diffusive persistence and the `sign-time' distribution
We present a new method for extracting the persistence exponent theta for the
diffusion equation, based on the distribution P of `sign-times'. With the aid
of a numerically verified Ansatz for P we derive an exact formula for theta in
arbitrary spatial dimension d. Our results are in excellent agreement with
previous numerical studies. Furthermore, our results indicate a qualitative
change in P above d ~ 36, signalling the existence of a sharp change in the
ergodic properties of the diffusion field.Comment: 5 pages, 2 tar gzip figures (Latex), subm. to PRE (Rapid Comm), new
reference adde
Self-gravitating astrophysical mass with singular central density vibrating in fundamental mode
The fluid-dynamical model of a self-gravitating mass of viscous liquid with
singular density at the center vibrating in fundamental mode is considered in
juxtaposition with that for Kelvin fundamental mode in a homogeneous heavy mass
of incompressible inviscid liquid. Particular attention is given to the
difference between spectral formulae for the frequency and lifetime of -mode
in the singular and homogeneous models. The newly obtained results are
discussed in the context of theoretical asteroseismology of pre-white dwarf
stage of red giants and stellar cocoons -- spherical gas-dust clouds with dense
star-forming core at the center.Comment: Mod. Phys. Lett. A, Vol. 24, No. 40 (2009) pp. 3257-327
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