85,200 research outputs found
Fatigue failure load indicator
An indicator for recording the load at which a fatigue specimen breaks during the last cycle of a fatigue test is described. A load cell is attached to the specimen which is alternately subjected to tension and compression loads. The output of the load cell which is proportional to the load on the specimen is applied to the input of a peak detector. Each time the specimen is subjected to a compression load, means are provided for applying a positive voltage to the rest of the peak detector to reset it. During the last cycle of the tension load the peak detector measures the maximum load on the specimen. Means are provided for disconnecting the load cell from the peak detector when there is a failure in the specimen
Chiral Vortons and Cosmological Constraints on Particle Physics
We investigate the cosmological consequences of particle physics theories
that admit stable loops of current-carrying string - vortons. In particular, we
consider chiral theories where a single fermion zero mode is excited in the
string core, such as those arising in supersymmetric theories with a D-term.
The resulting vortons formed in such theories are expected to be more stable
than their non-chiral cousins. General symmetry breaking schemes are considered
in which strings formed at one symmetry breaking scale become current-carrying
at a subsequent phase transition. The vorton abundance is estimated and
constraints placed on the underlying particle physics theories from
cosmological observations. Our constraints on the chiral theory are
considerably more stringent than the previous estimates for more general
theories.Comment: minor corrections made. This version will appear in PR
When Hashes Met Wedges: A Distributed Algorithm for Finding High Similarity Vectors
Finding similar user pairs is a fundamental task in social networks, with
numerous applications in ranking and personalization tasks such as link
prediction and tie strength detection. A common manifestation of user
similarity is based upon network structure: each user is represented by a
vector that represents the user's network connections, where pairwise cosine
similarity among these vectors defines user similarity. The predominant task
for user similarity applications is to discover all similar pairs that have a
pairwise cosine similarity value larger than a given threshold . In
contrast to previous work where is assumed to be quite close to 1, we
focus on recommendation applications where is small, but still
meaningful. The all pairs cosine similarity problem is computationally
challenging on networks with billions of edges, and especially so for settings
with small . To the best of our knowledge, there is no practical solution
for computing all user pairs with, say on large social networks,
even using the power of distributed algorithms.
Our work directly addresses this challenge by introducing a new algorithm ---
WHIMP --- that solves this problem efficiently in the MapReduce model. The key
insight in WHIMP is to combine the "wedge-sampling" approach of Cohen-Lewis for
approximate matrix multiplication with the SimHash random projection techniques
of Charikar. We provide a theoretical analysis of WHIMP, proving that it has
near optimal communication costs while maintaining computation cost comparable
with the state of the art. We also empirically demonstrate WHIMP's scalability
by computing all highly similar pairs on four massive data sets, and show that
it accurately finds high similarity pairs. In particular, we note that WHIMP
successfully processes the entire Twitter network, which has tens of billions
of edges
Stress concentrations around voids in three dimensions : The roots of failure
Funding This work forms part of a NERC New Investigator award for DH (NE/I001743/1), which is gratefully acknowledged. Acknowledgments The authors would like to acknowledge the reviewers, Elizabeth Ritz and Phillip Resor. Their reviews were very constructive, both helping to improve the manuscripts consistency and highlighting a number of errors in the initial submission. The authors would also like to thank Lydia Jagger's keen eye and patience, she helped greatly in removing a number of grammatical errors from the initial draft.Peer reviewedPublisher PD
Household debt and foreign currency borrowing in new member states of the EU
In the light of rapidly rising household debt, we undertake panel estimation of
determinants of debt-income ratios in new EU member states of Central and Eastern Europe
and interpret the results in the light of indicators of housing bubbles, estimates of equilibrium debt ratios from Western Europe and information on foreign currency borrowing in the CEE. We conclude that there are potential risks from overindebtedness in some of these countries, while in others where debt-income ratios appear sustainable, there remain risks related to high levels of foreign currency debt, notably where there is a floating exchange rate. Important
issues are raised for future economic performance as well as the structure of banking regulation
Titanium honeycomb structure
A brazed titanium honeycomb sandwich system for supersonic transport wing cover panels provides the most efficient structure spanwise, chordwise, and loadwise. Flutter testing shows that high wing stiffness is most efficient in a sandwich structure. This structure also provides good thermal insulation if liquid fuel is carried in direct contact with the wing structure in integral fuel tanks
Perspective distortion modeling for image measurements
A perspective distortion modelling for monocular view that is based on the fundamentals of perspective projection is presented in this work. Perspective projection is considered to be the most ideal and realistic model among others, which depicts image formation in monocular vision. There are many approaches trying to model and estimate the perspective effects in images. Some approaches try to learn and model the distortion parameters from a set of training data that work only for a predefined structure. None of the existing methods provide deep understanding of the nature of perspective problems. Perspective distortions, in fact, can be described by three different perspective effects. These effects are pose, distance and foreshortening. They are the cause of the aberrant appearance of object shapes in images. Understanding these phenomena have long been an interesting topic for artists, designers and scientists. In many cases, this problem has to be necessarily taken into consideration when dealing with image diagnostics, high and accurate image measurement, as well as accurate pose estimation from images. In this work, a perspective distortion model for every effect is developed while elaborating the nature of perspective effects. A distortion factor for every effect is derived, then followed by proposed methods, which allows extracting the true target pose and distance, and correcting image measurements
Advanced Computer Dormant Reliability Study Final Report
Reliability of integrated circuits and discrete components of electronics for computer and dormant module for Minuteman
On the Uniqueness of Solution of Magnetostatic Vectorāpotential Problems by Threeādimensional Finiteāelement Methods
In this paper, particular attention is paid to the impact of finiteāelement approximation on uniqueness and to approximations implicit in finite element formulations from the uniqueness requirements standpoint. It is also shown that the flux density is unique without qualifications. The theoretical and numerical uniqueness of the magnetic vector potential in threeādimensional problems is also given. This analysis is restricted to linear, isotropic media with Dirichlet Boundary conditions. As an interesting consequence of this analysis it is shown that, under usual conditions adopted in obtaining threeādimensional finiteāelement solutions, it is not necessary to specify div Ä in order that Ä be uniquely defined
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