144,409 research outputs found
Martina Navratilova - Jennifer Capriati - Connors and McEnroe
This past weekend in one of those nameless faceless tennis tournaments that no one pays much attention to, Martina Navratilova made tennis history by becoming the oldest player to ever defeat a number one ranked player. At age 36 years, 3 months and 29 days, Martina beat the 19 year old Monica Seles in three sets, winning a third set tie breaker. This match ended Seles\u27 winning streak at 34 matches
How COVID-19 revealed the politics of our economy
Drawing on a new book on the events of 2020-21, William Davies, Sahil Jai Dutta, Nick Taylor, and Martina Tazzioli offer a critical account of COVID-19 as a political-economic rupture, exposing underlying power struggles and social injustices
Residual stress of as-deposited and rolled Wire + Arc Additive Manufacturing Ti–6Al–4V components
Wire + arc additive manufacturing components contain significant residual stresses, which manifest in distortion. High-pressure rolling was applied to each layer of a linear Ti–6Al–4V wire + arc additive manufacturing component in between deposition passes. In rolled specimens, out-of-plane distortion was more than halved; a change in the deposits' geometry due to plastic deformation was observed and process repeatability was increased. The Contour method of residual stresses measurements showed that although the specimens still exhibited tensile stresses (up to 500 MPa), their magnitude was reduced by 60%, particularly at the interface between deposit and substrate. The results were validated with neutron diffraction measurements, which were in good agreement away from the baseplate
Exotic galilean symmetry and non-commutative mechanics
Some aspects of the "exotic" particle, associated with the two-parameter
central extension of the planar Galilei group are reviewed. A fundamental
property is that it has non-commuting position coordinates. Other and
generalized non-commutative models are also discussed. Minimal as well as
anomalous coupling to an external electromagnetic field is presented.
Supersymmetric extension is also considered. Exotic Galilean symmetry is also
found in Moyal field theory. Similar equations arise for a semiclassical Bloch
electron, used to explain the anomalous/spin/optical Hall effects.Comment: Review paper. Published versio
Attack-Surface Metrics, OSSTMM and Common Criteria Based Approach to “Composable Security” in Complex Systems
In recent studies on Complex Systems and Systems-of-Systems theory, a huge effort has been put to cope with behavioral problems, i.e. the possibility of controlling a desired overall or end-to-end behavior by acting on the individual elements that constitute the system itself. This problem is particularly important in the “SMART” environments, where the huge number of devices, their significant computational capabilities as well as their tight interconnection produce a complex architecture for which it is difficult to predict (and control) a desired behavior; furthermore, if the scenario is allowed to dynamically evolve through the modification of both topology and subsystems composition, then the control problem becomes a real challenge. In this perspective, the purpose of this paper is to cope with a specific class of control problems in complex systems, the “composability of security functionalities”, recently introduced by the European Funded research through the pSHIELD and nSHIELD projects (ARTEMIS-JU programme). In a nutshell, the objective of this research is to define a control framework that, given a target security level for a specific application scenario, is able to i) discover the system elements, ii) quantify the security level of each element as well as its contribution to the security of the overall system, and iii) compute the control action to be applied on such elements to reach the security target. The main innovations proposed by the authors are: i) the definition of a comprehensive methodology to quantify the security of a generic system independently from the technology and the environment and ii) the integration of the derived metrics into a closed-loop scheme that allows real-time control of the system. The solution described in this work moves from the proof-of-concepts performed in the early phase of the pSHIELD research and enrich es it through an innovative metric with a sound foundation, able to potentially cope with any kind of pplication scenarios (railways, automotive, manufacturing, ...)
A regularity result for quasilinear stochastic partial differential equations of parabolic type
We consider a quasilinear parabolic stochastic partial differential equation
driven by a multiplicative noise and study regularity properties of its weak
solution satisfying classical a priori estimates. In particular, we determine
conditions on coefficients and initial data under which the weak solution is
H\"older continuous in time and possesses spatial regularity that is only
limited by the regularity of the given data. Our proof is based on an efficient
method of increasing regularity: the solution is rewritten as the sum of two
processes, one solves a linear parabolic SPDE with the same noise term as the
original model problem whereas the other solves a linear parabolic PDE with
random coefficients. This way, the required regularity can be achieved by
repeatedly making use of known techniques for stochastic convolutions and
deterministic PDEs
Comparing disease control policies for interacting wild populations
We consider interacting population systems of predator-prey type, presenting
four models of control strategies for epidemics among the prey. In particular
to contain the transmissible disease, safety niches are considered, assuming
they lessen the disease spread, but do not protect prey from predators. This
represents a novelty with respect to standard ecosystems where the refuge
prevents predators' attacks. The niche is assumed either to protect the healthy
individuals, or to hinder the infected ones to get in contact with the
susceptibles, or finally to reduce altogether contacts that might lead to new
cases of the infection. In addition a standard culling procedure is also
analysed. The effectiveness of the different strategies are compared. Probably
the environments providing a place where disease carriers cannot come in
contact with the healthy individuals, or where their contact rates are lowered,
seem to preferable for disease containment
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