976 research outputs found
A robust and efficient video representation for action recognition
This paper introduces a state-of-the-art video representation and applies it
to efficient action recognition and detection. We first propose to improve the
popular dense trajectory features by explicit camera motion estimation. More
specifically, we extract feature point matches between frames using SURF
descriptors and dense optical flow. The matches are used to estimate a
homography with RANSAC. To improve the robustness of homography estimation, a
human detector is employed to remove outlier matches from the human body as
human motion is not constrained by the camera. Trajectories consistent with the
homography are considered as due to camera motion, and thus removed. We also
use the homography to cancel out camera motion from the optical flow. This
results in significant improvement on motion-based HOF and MBH descriptors. We
further explore the recent Fisher vector as an alternative feature encoding
approach to the standard bag-of-words histogram, and consider different ways to
include spatial layout information in these encodings. We present a large and
varied set of evaluations, considering (i) classification of short basic
actions on six datasets, (ii) localization of such actions in feature-length
movies, and (iii) large-scale recognition of complex events. We find that our
improved trajectory features significantly outperform previous dense
trajectories, and that Fisher vectors are superior to bag-of-words encodings
for video recognition tasks. In all three tasks, we show substantial
improvements over the state-of-the-art results
Enabling Program Analysis Through Deterministic Replay and Optimistic Hybrid Analysis
As software continues to evolve, software systems increase in complexity. With software systems composed of many distinct but interacting components, today’s system programmers, users, and administrators find themselves requiring automated ways to find, understand, and handle system mis-behavior. Recent information breaches such as the Equifax breach of 2017, and the Heartbleed vulnerability of 2014 show the need to understand and debug prior states of computer systems.
In this thesis I focus on enabling practical entire-system retroactive analysis, allowing programmers, users, and system administrators to diagnose and understand the impact of these devastating mishaps. I focus primarly on two techniques. First, I discuss a novel deterministic record and replay system which enables fast, practical recollection of entire systems of computer state. Second, I discuss optimistic hybrid analysis, a novel optimization
method capable of dramatically accelerating retroactive program analysis.
Record and replay systems greatly aid in solving a variety of problems, such as fault tolerance, forensic analysis, and information providence. These solutions, however, assume ubiquitous recording of any application which may have a problem. Current record and replay systems are forced to trade-off between disk space and replay speed. This trade-off has historically made it impractical to both record and replay large histories of system level computation. I present Arnold, a novel record and replay system which efficiently records years of computation on a commodity hard-drive, and can efficiently replay any recorded information. Arnold combines caching with a unique process-group granularity
of recording to produce both small, and quickly recalled recordings. My experiments show that under a desktop workload, Arnold could store 4 years of computation on a commodity 4TB hard drive.
Dynamic analysis is used to retroactively identify and address many forms of system mis-behaviors including: programming errors, data-races, private information leakage, and memory errors. Unfortunately, the runtime overhead of dynamic analysis has precluded its adoption in many instances. I present a new dynamic analysis methodology called optimistic hybrid analysis (OHA). OHA uses knowledge of the past to predict program behaviors in the future. These predictions, or likely invariants are speculatively assumed true by a static analysis. This creates a static analysis which can be far more accurate than
its traditional counterpart. Once this predicated static analysis is created, it is speculatively used to optimize a final dynamic analysis, creating a far more efficient dynamic analysis than otherwise possible. I demonstrate the effectiveness of OHA by creating an optimistic hybrid backward slicer, OptSlice, and optimistic data-race detector OptFT. OptSlice and OptFT are just as accurate as their traditional hybrid counterparts, but run on average 8.3x
and 1.6x faster respectively.
In this thesis I demonstrate that Arnold’s ability to record and replay entire computer systems, combined with optimistic hybrid analysis’s ability to quickly analyze prior computation, enable a practical and useful entire system retroactive analysis that has been previously unrealized.PHDComputer Science & EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/144052/1/ddevec_1.pd
Learning in vision and robotics
I present my work on learning from video and robotic input. This is an important problem, with numerous potential applications. The use of machine learning makes it possible to obtain models which can handle noise and variation without explicitly programming them. It also raises the possibility of robots which can interact more seamlessly with humans rather than only exhibiting hard-coded behaviors. I will present my work in two areas: video action recognition, and robot navigation. First, I present a video action recognition method which represents actions in video by sequences of retinotopic appearance and motion detectors, learns such models automatically from training data, and allow actions in new video to be recognized and localized completely automatically. Second, I present a new method which allows a mobile robot to learn word meanings from a combination of robot sensor measurements and sentential descriptions corresponding to a set of robotically driven paths. These word meanings support automatic driving from sentential input, and generation of sentential description of new paths. Finally, I also present work on a new action recognition dataset, and comparisons of the performance of recent methods on this dataset and others
The Surveillance AI Pipeline
A rapidly growing number of voices have argued that AI research, and computer
vision in particular, is closely tied to mass surveillance. Yet the direct path
from computer vision research to surveillance has remained obscured and
difficult to assess. This study reveals the Surveillance AI pipeline. We obtain
three decades of computer vision research papers and downstream patents (more
than 20,000 documents) and present a rich qualitative and quantitative
analysis. This analysis exposes the nature and extent of the Surveillance AI
pipeline, its institutional roots and evolution, and ongoing patterns of
obfuscation. We first perform an in-depth content analysis of computer vision
papers and downstream patents, identifying and quantifying key features and the
many, often subtly expressed, forms of surveillance that appear. On the basis
of this analysis, we present a topology of Surveillance AI that characterizes
the prevalent targeting of human data, practices of data transferal, and
institutional data use. We find stark evidence of close ties between computer
vision and surveillance. The majority (68%) of annotated computer vision papers
and patents self-report their technology enables data extraction about human
bodies and body parts and even more (90%) enable data extraction about humans
in general
Foundational Models in Medical Imaging: A Comprehensive Survey and Future Vision
Foundation models, large-scale, pre-trained deep-learning models adapted to a
wide range of downstream tasks have gained significant interest lately in
various deep-learning problems undergoing a paradigm shift with the rise of
these models. Trained on large-scale dataset to bridge the gap between
different modalities, foundation models facilitate contextual reasoning,
generalization, and prompt capabilities at test time. The predictions of these
models can be adjusted for new tasks by augmenting the model input with
task-specific hints called prompts without requiring extensive labeled data and
retraining. Capitalizing on the advances in computer vision, medical imaging
has also marked a growing interest in these models. To assist researchers in
navigating this direction, this survey intends to provide a comprehensive
overview of foundation models in the domain of medical imaging. Specifically,
we initiate our exploration by providing an exposition of the fundamental
concepts forming the basis of foundation models. Subsequently, we offer a
methodical taxonomy of foundation models within the medical domain, proposing a
classification system primarily structured around training strategies, while
also incorporating additional facets such as application domains, imaging
modalities, specific organs of interest, and the algorithms integral to these
models. Furthermore, we emphasize the practical use case of some selected
approaches and then discuss the opportunities, applications, and future
directions of these large-scale pre-trained models, for analyzing medical
images. In the same vein, we address the prevailing challenges and research
pathways associated with foundational models in medical imaging. These
encompass the areas of interpretability, data management, computational
requirements, and the nuanced issue of contextual comprehension.Comment: The paper is currently in the process of being prepared for
submission to MI
Humboldt Bay Independent Spent Fuel Storage Installation Final Safety Analysis Report Update
Author N/A
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Final Safety Analysis Report Update
Revision 11
NRC Docket No. 72-2
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