236 research outputs found
Key exchange with the help of a public ledger
Blockchains and other public ledger structures promise a new way to create
globally consistent event logs and other records. We make use of this
consistency property to detect and prevent man-in-the-middle attacks in a key
exchange such as Diffie-Hellman or ECDH. Essentially, the MitM attack creates
an inconsistency in the world views of the two honest parties, and they can
detect it with the help of the ledger. Thus, there is no need for prior
knowledge or trusted third parties apart from the distributed ledger. To
prevent impersonation attacks, we require user interaction. It appears that, in
some applications, the required user interaction is reduced in comparison to
other user-assisted key-exchange protocols
Scalar-tensor cosmology at the general relativity limit: Jordan vs Einstein frame
We consider the correspondence between the Jordan frame and the Einstein
frame descriptions of scalar-tensor theory of gravitation. We argue that since
the redefinition of the scalar field is not differentiable at the limit of
general relativity the correspondence between the two frames is lost at this
limit. To clarify the situation we analyse the dynamics of the scalar field in
different frames for two distinct scalar-tensor cosmologies with specific
coupling functions and demonstrate that the corresponding scalar field phase
portraits are not equivalent for regions containing the general relativity
limit. Therefore the answer to the question whether general relativity is an
attractor for the theory depends on the choice of the frame.Comment: 16 pages, 8 figures, version appeared in PR
Scalar-tensor cosmologies: fixed points of the Jordan frame scalar field
We study the evolution of homogeneous and isotropic, flat cosmological models
within the general scalar-tensor theory of gravity with arbitrary coupling
function and potential. After introducing the limit of general relativity we
describe the details of the phase space geometry. Using the methods of
dynamical systems for the decoupled equation of the Jordan frame scalar field
we find the fixed points of flows in two cases: potential domination and matter
domination. We present the conditions on the mathematical form of the coupling
function and potential which determine the nature of the fixed points
(attractor or other). There are two types of fixed points, both are
characterized by cosmological evolution mimicking general relativity, but only
one of the types is compatible with the Solar System PPN constraints. The phase
space structure should also carry over to the Einstein frame as long as the
transformation between the frames is regular which however is not the case for
the latter (PPN compatible) fixed point.Comment: 21 pages, 4 figures, some comments and references adde
Proceedings of the inaugural International Summit for Medical Nutrition Education and Research
© 2016 The Royal Society for Public Health Medical Nutrition Education (MNE) has been identified as an area with potential public health impact. Despite countries having distinctive education systems, barriers and facilitators to effective MNE are consistent across borders, demanding a common platform to initiate global programmes. A shared approach to supporting greater MNE is ideal to support countries to work together. In an effort to initiate this process, the Need for Nutrition Education/Innovation Programme group, in association with their strategic partners, hosted the inaugural International Summit on Medical Nutrition Education and Research on August 8, 2015 in Cambridge, UK. Speakers from the UK, the USA, Canada, Australia, New Zealand, Italy, and India provided insights into their respective countries including their education systems, inherent challenges, and potential solutions across two main themes: (1) Medical Nutrition Education, focused on best practice examples in competencies and assessment; and (2) Medical Nutrition Research, discussing how to translate nutrition research into education opportunities. The Summit identified shared needs across regions, showcased examples of transferrable strategies and identified opportunities for collaboration in nutrition education for healthcare (including medical) professionals. These proceedings highlight the key messages presented at the Summit and showcase opportunities for working together towards a common goal of improvement in MNE to improve public health at large
Pulsed laser deposited KNbO thin films for applications in high frequency range
Potassium niobate thin films were grown by pulsed laser deposition on various substrates. Influence of deposition conditions on film characteristics was studied. Structural investigation evidenced that single phase polycrystalline randomly oriented films were grown on sintered alumina whereas epitaxial films were grown on (100)SrTiO and (100)MgO substrates. The microstructure was highly controlled by the structural characteristics. Interdigited capacitors built from KNbO3 films on two different substrates (alumina and MgO) showed the strong influence of the structural characteristics on the dielectric behavior. The variation of the equivalent capacitance measured on the interdigital capacitor on MgO was 6.4% at 2.5 GHz while it was 1.5% on alumina, in both cases for a moderate applied field of 15 kV cm. The results show the potentiality of these ferroelectric materials for use in frequency agile microwave electronics
Supervised Domain Adaptation using Graph Embedding
Getting deep convolutional neural networks to perform well requires a large
amount of training data. When the available labelled data is small, it is often
beneficial to use transfer learning to leverage a related larger dataset
(source) in order to improve the performance on the small dataset (target).
Among the transfer learning approaches, domain adaptation methods assume that
distributions between the two domains are shifted and attempt to realign them.
In this paper, we consider the domain adaptation problem from the perspective
of dimensionality reduction and propose a generic framework based on graph
embedding. Instead of solving the generalised eigenvalue problem, we formulate
the graph-preserving criterion as a loss in the neural network and learn a
domain-invariant feature transformation in an end-to-end fashion. We show that
the proposed approach leads to a powerful Domain Adaptation framework; a simple
LDA-inspired instantiation of the framework leads to state-of-the-art
performance on two of the most widely used Domain Adaptation benchmarks,
Office31 and MNIST to USPS datasets.Comment: 7 pages, 3 figures, 3 table
Phase Space Analysis of Quintessence Cosmologies with a Double Exponential Potential
We use phase space methods to investigate closed, flat, and open
Friedmann-Robertson-Walker cosmologies with a scalar potential given by the sum
of two exponential terms. The form of the potential is motivated by the
dimensional reduction of M-theory with non-trivial four-form flux on a
maximally symmetric internal space. To describe the asymptotic features of
run-away solutions we introduce the concept of a `quasi fixed point.' We give
the complete classification of solutions according to their late-time behavior
(accelerating, decelerating, crunch) and the number of periods of accelerated
expansion.Comment: 46 pages, 5 figures; v2: minor changes, references added; v3: title
changed, refined classification of solutions, 3 references added, version
which appeared in JCA
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