71,293 research outputs found
Best Effort and Practice Activation Codes
Activation Codes are used in many different digital services and known by
many different names including voucher, e-coupon and discount code. In this
paper we focus on a specific class of ACs that are short, human-readable,
fixed-length and represent value. Even though this class of codes is
extensively used there are no general guidelines for the design of Activation
Code schemes. We discuss different methods that are used in practice and
propose BEPAC, a new Activation Code scheme that provides both authenticity and
confidentiality. The small message space of activation codes introduces some
problems that are illustrated by an adaptive chosen-plaintext attack (CPA-2) on
a general 3-round Feis- tel network of size 2^(2n) . This attack recovers the
complete permutation from at most 2^(n+2) plaintext-ciphertext pairs. For this
reason, BEPAC is designed in such a way that authenticity and confidentiality
are in- dependent properties, i.e. loss of confidentiality does not imply loss
of authenticity.Comment: 15 pages, 3 figures, TrustBus 201
Connected component identification and cluster update on GPU
Cluster identification tasks occur in a multitude of contexts in physics and
engineering such as, for instance, cluster algorithms for simulating spin
models, percolation simulations, segmentation problems in image processing, or
network analysis. While it has been shown that graphics processing units (GPUs)
can result in speedups of two to three orders of magnitude as compared to
serial codes on CPUs for the case of local and thus naturally parallelized
problems such as single-spin flip update simulations of spin models, the
situation is considerably more complicated for the non-local problem of cluster
or connected component identification. I discuss the suitability of different
approaches of parallelization of cluster labeling and cluster update algorithms
for calculations on GPU and compare to the performance of serial
implementations.Comment: 15 pages, 14 figures, one table, submitted to PR
Using Local Knowledge to Shrink the Individual Carbon Footprint
Entire texts have been devoted to exploring the meaning of the term âlifestyleâ and sociological understandings of lifestyle are complex and nuanced.For present purposes, however, a more simple articulation of the term will suffice. Lifestyle can mean âmode of living,â including âpatterns of actionâ and âpatterns of ways of living.â Without rendering judgment, one observation that can fairly be made about the current lifestyles and associated behaviors of Americans is that they indirectly and directly lead to the emission of a high volume of greenhouse gases (âGHGsâ).7 Although an American diplomat is said to have remarked in preparing for the Rio Earth Summit that ââthe American lifestyle is not up for negotiation,ââ a growing number of legal scholars recognize the need for environmental policy to capture individual GHG emissions, and have begun to explore whether and how the law can or should be used to change individual, GHG-emitting lifestyles and behaviors. One consideration in designing a policy aimed at individual, GHG-emitting behaviors will be the division of authority between different levels of government. As evidenced by the opening quotations, local governments are often characterized as well-situated to influence individual behavior, particularly GHG-emitting behaviors. This Idea links concepts developed in the environmental federalism literature with work discussing the use of law to influence environmental behaviors to consider the competence of local governments with respect to influencing individual, GHG-emitting lifestyle and behavior choices
Physics-related epistemic uncertainties in proton depth dose simulation
A set of physics models and parameters pertaining to the simulation of proton
energy deposition in matter are evaluated in the energy range up to
approximately 65 MeV, based on their implementations in the Geant4 toolkit. The
analysis assesses several features of the models and the impact of their
associated epistemic uncertainties, i.e. uncertainties due to lack of
knowledge, on the simulation results. Possible systematic effects deriving from
uncertainties of this kind are highlighted; their relevance in relation to the
application environment and different experimental requirements are discussed,
with emphasis on the simulation of radiotherapy set-ups. By documenting
quantitatively the features of a wide set of simulation models and the related
intrinsic uncertainties affecting the simulation results, this analysis
provides guidance regarding the use of the concerned simulation tools in
experimental applications; it also provides indications for further
experimental measurements addressing the sources of such uncertainties.Comment: To be published in IEEE Trans. Nucl. Sc
Activation and radiation damage in the environment of hadron accelerators
A component which suffers radiation damage usually also becomes radioactive,
since the source of activation and radiation damage is the interaction of the
material with particles from an accelerator or with reaction products. However,
the underlying mechanisms of the two phenomena are different. These mechanisms
are described here. Activation and radiation damage can have far-reaching
consequences. Components such as targets, collimators, and beam dumps are the
first candidates for failure as a result of radiation damage. This means that
they have to be replaced or repaired. This takes time, during which personnel
accumulate dose. If the dose to personnel at work would exceed permitted
limits, remote handling becomes necessary. The remaining material has to be
disposed of as radioactive waste, for which an elaborate procedure acceptable
to the authorities is required. One of the requirements of the authorities is a
complete nuclide inventory. The methods used for calculation of such
inventories are presented, and the results are compared with measured data. In
the second part of the paper, the effect of radiation damage on material
properties is described. The mechanism of damage to a material due to
irradiation is described. The amount of radiation damage is quantified in terms
of displacements per atom. Its calculation and deficiencies in explaining and
predicting the changes in mechanical and thermal material properties are
discussed, and examples are given.Comment: 27 pages, contribution to the CAS - CERN Accelerator School: Course
on High Power Hadron Machines; 24 May - 2 Jun 2011, Bilbao, Spai
Animal welfare science: recent publication trends and future research priorities
Animal welfare science is a young and thriving field. Over the last two decades, the output of scientific publications on welfare has increased by c. 10-15% annually (tripling as a proportion of all science papers logged by ISIâs Web of Science), with just under half the c. 8500 total being published in the last 4 years. These papers span an incredible 500+ journals, but around three quarters have been in 80 animal science, veterinary, ethology, conservation and specialized welfare publications, and nearly 25% are published in just two: Animal Welfare and Applied Animal Behaviour Science. Farmed animals â especially mammals â have attracted by far the most research. This broadly reflects the vastness of their populations and the degree of public concern they elicit; poultry, however, are under-studied, and farmed fish ever more so: fish have only recently attracted welfare research, and are by far the least studied of all agricultural species, perhaps because of ongoing doubts about their sentience. We predict this farm animal focus will continue in the future, but embracing more farmed fish, reptiles and invertebrates, and placing its findings within broader international contexts such as environmental and food security concerns. Laboratory animals have been consistently well studied, with a shift in recent years away from primates and towards rodents. Pets, the second largest animal sector after farmed animals, have in contrast been little studied considering their huge populations (cats being especially overlooked): we anticipate research on them increasing in the future. Captive wild animals, especially mammals, have attracted a consistent level of welfare research over the last two decades. Given the many thousands of diverse species kept by zoos, this must, and we predict will, increase. Future challenges and opportunities including refining the use of preference tests, stereotypic behaviour, corticosteroid outputs and putative indicators of positive affect, to enable more valid conclusions about welfare; investigating the evolution and functions of affective states; and last but not least, identifying which taxonomic groups and stages of development are actually sentient and so worthy of welfare concern
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