1,577 research outputs found
Nuclear burst plasma injection into the magnetosphere and resulting spacecraft charging
The passage of debris from a high altitude ( 400 km) nuclear burst over the ionospheric plasma is found to be capable of exciting large amplitude whistler waves which can act to structure a collisionless shock. This instability will occur in the loss cone exits of the nuclear debris bubble, and the accelerated ambient ions will freestream along the magnetic field lines into the magnetosphere. Using Starfish-like parameters and accounting for plasma diffusion and thermalization of the propagating plasma mass, it is found that synchronous orbit plasma fluxes of high temperature electrons (near 10 keV) will be significantly greater than those encountered during magnetospheric substorms. These fluxes will last for sufficiently long periods of time so as to charge immersed bodies to high potentials and arc discharges to take place
Geometric loss functions for camera pose regression with deep learning
Deep learning has shown to be effective for robust and real-time monocular
image relocalisation. In particular, PoseNet is a deep convolutional neural
network which learns to regress the 6-DOF camera pose from a single image. It
learns to localize using high level features and is robust to difficult
lighting, motion blur and unknown camera intrinsics, where point based SIFT
registration fails. However, it was trained using a naive loss function, with
hyper-parameters which require expensive tuning. In this paper, we give the
problem a more fundamental theoretical treatment. We explore a number of novel
loss functions for learning camera pose which are based on geometry and scene
reprojection error. Additionally we show how to automatically learn an optimal
weighting to simultaneously regress position and orientation. By leveraging
geometry, we demonstrate that our technique significantly improves PoseNet's
performance across datasets ranging from indoor rooms to a small city
Modelling uncertainty in deep learning for camera relocalization
We present a robust and real-time monocular six degree of freedom visual
relocalization system. We use a Bayesian convolutional neural network to
regress the 6-DOF camera pose from a single RGB image. It is trained in an
end-to-end manner with no need of additional engineering or graph optimisation.
The algorithm can operate indoors and outdoors in real time, taking under 6ms
to compute. It obtains approximately 2m and 6 degrees accuracy for very large
scale outdoor scenes and 0.5m and 10 degrees accuracy indoors. Using a Bayesian
convolutional neural network implementation we obtain an estimate of the
model's relocalization uncertainty and improve state of the art localization
accuracy on a large scale outdoor dataset. We leverage the uncertainty measure
to estimate metric relocalization error and to detect the presence or absence
of the scene in the input image. We show that the model's uncertainty is caused
by images being dissimilar to the training dataset in either pose or
appearance
Strain Measurement on Composites: Errors due to Rosette Misalignment
Electrical resistance strain gauges are increasingly used for the determination of the
strain field in composite components. The effect of the angular misalignment of a strain gauge rosette
on the determination of the strains in a composite material is investigated in this paper. The
theoretical analysis shows that the strain error along the principal material directions depends on the
difference of principal strains, on the angular misalignment of the rosette and on the angle between
the maximum principal strain and the fibre direction. The paper also shows experimental evidence
for the theoretical analysis
TTF-1/p63-positive poorly differentiated NSCLC: A histogenetic hypothesis from the basal reserve cell of the terminal respiratory unit
TTF-1 is expressed in the alveolar epithelium and in the basal cells of distal terminal bronchioles. It is considered the most sensitive and specific marker to define the adenocarcinoma arising from the terminal respiratory unit (TRU). TTF-1, CK7, CK5/6, p63 and p40 are useful for typifying the majority of non-small-cell lung cancers, with TTF and CK7 being typically expressed in adenocarcinomas and the latter three being expressed in squamous cell carcinoma. As tumors with coexpression of both TTF-1 and p63 in the same cells are rare, we describe different cases that coexpress them, suggesting a histogenetic hypothesis of their origin. We report 10 cases of poorly differentiated non-small-cell lung carcinoma (PD-NSCLC). Immunohistochemistry was performed by using TTF-1, p63, p40 (∆Np63), CK5/6 and CK7. EGFR and BRAF gene mutational analysis was performed by using real-time PCR. All the cases showed coexpression of p63 and TTF-1. Six of them showing CK7+ and CK5/6− immunostaining were diagnosed as “TTF-1+ p63+ adenocarcinoma”. The other cases of PD-NSCLC, despite the positivity for CK5/6, were diagnosed as “adenocarcinoma, solid variant”, in keeping with the presence of TTF-1 expression and p40 negativity. A “wild type” genotype of EGFR was evidenced in all cases. TTF1 stained positively the alveolar epithelium and the basal reserve cells of TRU, with the latter also being positive for p63. The coexpression of p63 and TTF-1 could suggest the origin from the basal reserve cells of TRU and represent the capability to differentiate towards different histogenetic lines. More aggressive clinical and morphological features could characterize these “basal-type tumors” like those in the better known “basal-like” cancer of the breast
Bayesian segnet: Model uncertainty in deep convolutional encoder-decoder architectures for scene understanding
We present a deep learning framework for probabilistic pixel-wise semantic
segmentation, which we term Bayesian SegNet. Semantic segmentation is an
important tool for visual scene understanding and a meaningful measure of
uncertainty is essential for decision making. Our contribution is a practical
system which is able to predict pixel-wise class labels with a measure of model
uncertainty. We achieve this by Monte Carlo sampling with dropout at test time
to generate a posterior distribution of pixel class labels. In addition, we
show that modelling uncertainty improves segmentation performance by 2-3%
across a number of state of the art architectures such as SegNet, FCN and
Dilation Network, with no additional parametrisation. We also observe a
significant improvement in performance for smaller datasets where modelling
uncertainty is more effective. We benchmark Bayesian SegNet on the indoor SUN
Scene Understanding and outdoor CamVid driving scenes datasets.Toyota Corporatio
PoseNet: A convolutional network for real-time 6-dof camera relocalization
© 2015 IEEE. We present a robust and real-time monocular six degree of freedom relocalization system. Our system trains a convolutional neural network to regress the 6-DOF camera pose from a single RGB image in an end-to-end manner with no need of additional engineering or graph optimisation. The algorithm can operate indoors and outdoors in real time, taking 5ms per frame to compute. It obtains approximately 2m and 3 degrees accuracy for large scale outdoor scenes and 0.5m and 5 degrees accuracy indoors. This is achieved using an efficient 23 layer deep convnet, demonstrating that convnets can be used to solve complicated out of image plane regression problems. This was made possible by leveraging transfer learning from large scale classification data. We show that the PoseNet localizes from high level features and is robust to difficult lighting, motion blur and different camera intrinsics where point based SIFT registration fails. Furthermore we show how the pose feature that is produced generalizes to other scenes allowing us to regress pose with only a few dozen training examples
Deep roots: Improving CNN efficiency with hierarchical filter groups
We propose a new method for creating computationally efficient and compact
convolutional neural networks (CNNs) using a novel sparse connection structure
that resembles a tree root. This allows a significant reduction in
computational cost and number of parameters compared to state-of-the-art deep
CNNs, without compromising accuracy, by exploiting the sparsity of inter-layer
filter dependencies. We validate our approach by using it to train more
efficient variants of state-of-the-art CNN architectures, evaluated on the
CIFAR10 and ILSVRC datasets. Our results show similar or higher accuracy than
the baseline architectures with much less computation, as measured by CPU and
GPU timings. For example, for ResNet 50, our model has 40% fewer parameters,
45% fewer floating point operations, and is 31% (12%) faster on a CPU (GPU).
For the deeper ResNet 200 our model has 25% fewer floating point operations and
44% fewer parameters, while maintaining state-of-the-art accuracy. For
GoogLeNet, our model has 7% fewer parameters and is 21% (16%) faster on a CPU
(GPU).Microsoft Research PhD Scholarshi
Projective Bundle Adjustment from Arbitrary Initialization Using the Variable Projection Method
Bundle adjustment is used in structure-from-motion pipelines as final refinement stage requiring a sufficiently good initialization to reach a useful local mininum. Starting from an arbitrary initialization almost always gets trapped in a poor minimum. In this work we aim to obtain an initialization-free approach which returns global minima from a large proportion of purely random starting points. Our key inspiration lies in the success of the Variable Projection (VarPro) method for affine factorization problems, which have close to 100% chance of reaching a global minimum from random initialization. We find empirically that this desirable behaviour does not directly carry over to the projective case, and we consequently design and evaluate strategies to overcome this limitation. Also, by unifying the affine and the projective camera settings, we obtain numerically better conditioned reformulations of original bundle adjustment algorithms
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