1,155 research outputs found
A system for synthetic vision and augmented reality in future flight decks
Rockwell Science Center is investigating novel human-computer interaction techniques for enhancing the situational awareness in future flight decks. One aspect is to provide intuitive displays that provide the vital information and the spatial awareness by augmenting the real world with an overlay of relevant information registered to the real world. Such Augmented Reality (AR) techniques can be employed during bad weather scenarios to permit flying in Visual Flight Rules (VFR) in conditions which would normally require Instrumental Flight Rules (IFR). These systems could easily be implemented on heads-up displays (HUD). The advantage of AR systems vs. purely synthetic vision (SV) systems is that the pilot can relate the information overlay to real objects in the world, whereas SV systems provide a constant virtual view, where inconsistencies can hardly be detected. The development of components for such a system led to a demonstrator implemented on a PC. A camera grabs video images which are overlaid with registered information. Orientation of the camera is obtained from an inclinometer and a magnetometer; position is acquired from GPS. In a possible implementation in an airplane, the on-board attitude information can be used for obtaining correct registration. If visibility is sufficient, computer vision modules can be used to fine-tune the registration by matching visual cues with database features. This technology would be especially useful for landing approaches. The current demonstrator provides a frame-rate of 15 fps, using a live video feed as background with an overlay of avionics symbology in the foreground. In addition, terrain rendering from a 1 arc sec. digital elevation model database can be overlaid to provide synthetic vision in case of limited visibility. For true outdoor testing (on ground level), the system has been implemented on a wearable computer
Scaling of transverse nuclear magnetic relaxation due to magnetic nanoparticle aggregation
The aggregation of superparamagnetic iron oxide (SPIO) nanoparticles
decreases the transverse nuclear magnetic resonance (NMR) relaxation time T2 of
adjacent water molecules measured by a Carr-Purcell-Meiboom-Gill (CPMG)
pulse-echo sequence. This effect is commonly used to measure the concentrations
of a variety of small molecules. We perform extensive Monte Carlo simulations
of water diffusing around SPIO nanoparticle aggregates to determine the
relationship between T2 and details of the aggregate. We find that in the
motional averaging regime T2 scales as a power law with the number N of
nanoparticles in an aggregate. The specific scaling is dependent on the fractal
dimension d of the aggregates. We find T2 N^{-0.44} for aggregates with d=2.2,
a value typical of diffusion limited aggregation. We also find that in
two-nanoparticle systems, T2 is strongly dependent on the orientation of the
two nanoparticles relative to the external magnetic field, which implies that
it may be possible to sense the orientation of a two-nanoparticle aggregate. To
optimize the sensitivity of SPIO nanoparticle sensors, we propose that it is
best to have aggregates with few nanoparticles, close together, measured with
long pulse-echo times.Comment: 20 pages, 3 figures, submitted to Journal of Magnetism and Magnetic
Material
Effects of electrical charging on the mechanical Q of a fused silica disk
We report on the effects of an electrical charge on mechanical loss of a
fused silica disk. A degradation of Q was seen that correlated with charge on
the surface of the sample. We examine a number of models for charge damping,
including eddy current damping and loss due to polarization. We conclude that
rubbing friction between the sample and a piece of dust attracted by the
charged sample is the most likely explanation for the observed loss.Comment: submitted to Review of Scientific Instrument
Understanding the magnetic resonance spectrum of nitrogen vacancy centers in an ensemble of randomly-oriented nanodiamonds
Nanodiamonds containing nitrogen vacancy (NV-) centers show promise for a
number of emerging applications including targeted in vivo imaging and
generating nuclear spin hyperpolarization for enhanced NMR spectroscopy and
imaging. Here, we develop a detailed understanding of the magnetic resonance
behavior of NV- centers in an ensemble of nanodiamonds with random crystal
orientations. Two-dimensional optically detected magnetic resonance
spectroscopy reveals the distribution of energy levels, spin populations, and
transition probabilities that give rise to a complex spectrum. We identify
overtone transitions that are inherently insensitive to crystal orientation and
give well-defined transition frequencies that access the entire nanodiamond
ensemble. These transitions may be harnessed for high-resolution imaging and
generation of nuclear spin hyperpolarization. The data are well described by
numerical simulations from the zero- to high-field regimes, including the
intermediate regime of maximum complexity. We evaluate the prospects of
nanodiamond ensembles specifically for nuclear hyperpolarization and show that
frequency-swept dynamic nuclear polarization may transfer a large amount of the
NV- center's hyperpolarization to nuclear spins by sweeping over a small region
of its spectrum.Comment: 6 pages, 5 figure
Cardiovascular magnetic resonance: Stressing the future
Non-invasive cardiac stress imaging plays a central role in the assessment of patients with known or suspected coronary artery disease. The current guidelines suggest estimation of the myocardial ischaemic burden as a criterion for revascularisation on prognostic grounds despite the lack of standardised reporting of the magnitude of ischaemia on various non-invasive imaging methods. Future studies should aim to accurately describe the relationship between myocardial ischaemic burden as assessed by cardiovascular magnetic resonance imaging and mortality
Risk of sudden cardiac death:Are coronary chronic total occlusions an additional risk factor?
Sudden arrhythmic cardiac death remains a significant, potentially reversible, cardiological challenge in terms of creating accurate risk prediction models. The current guidelines for implantable cardioverter defibrillator (ICD) therapy are mainly based on left ventricular ejection fraction despite its low sensitivity and specificity in predicting sudden cardiac death (SCD). Chronic total occlusions have been associated with increased mortality but further research is required to clarify if they should be incorporated in a risk model predicting SCD aiming to identify patients that would benefit from ICD therapy even with preserved ejection fraction
`Third' Quantization of Vacuum Einstein Gravity and Free Yang-Mills Theories
Based on the algebraico-categorical (:sheaf-theoretic and sheaf
cohomological) conceptual and technical machinery of Abstract Differential
Geometry, a new, genuinely background spacetime manifold independent, field
quantization scenario for vacuum Einstein gravity and free Yang-Mills theories
is introduced. The scheme is coined `third quantization' and, although it
formally appears to follow a canonical route, it is fully covariant, because it
is an expressly functorial `procedure'. Various current and future Quantum
Gravity research issues are discussed under the light of 3rd-quantization. A
postscript gives a brief account of this author's personal encounters with
Rafael Sorkin and his work.Comment: 43 pages; latest version contributed to a fest-volume celebrating
Rafael Sorkin's 60th birthday (Erratum: in earlier versions I had wrongly
written that the Editor for this volume is Daniele Oriti, with CUP as
publisher. I apologize for the mistake.
CASAM: Collaborative Human-machine Annotation of Multimedia.
The CASAM multimedia annotation system implements a model of cooperative annotation between a human annotator and automated components. The aim is that they work asynchronously but together. The system focuses upon the areas where automated recognition and reasoning are most effective and the user is able to work in the areas where their unique skills are required. The system’s reasoning is influenced by the annotations provided by the user and, similarly, the user can see the system’s work and modify and, implicitly, direct it. The CASAM system interacts with the user by providing a window onto the current state of annotation, and by generating requests for information which are important for the final annotation or to constrain its reasoning. The user can modify the annotation, respond to requests and also add their own annotations. The objective is that the human annotator’s time is used more effectively and that the result is an annotation that is both of higher quality and produced more quickly. This can be especially important in circumstances where the annotator has a very restricted amount of time in which to annotate the document. In this paper we describe our prototype system. We expand upon the techniques used for automatically analysing the multimedia document, for reasoning over the annotations generated and for the generation of an effective interaction with the end-user. We also present the results of evaluations undertaken with media professionals in order to validate the approach and gain feedback to drive further research
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