31,381 research outputs found
Luminosity Scans for Beam Diagnostics
A new type of fast luminosity separation scans ("Emittance Scans") was
introduced at the CERN Large Hadron Collider (LHC) in 2015. The scans were
performed systematically in every fill with full-intensity beams in physics
production conditions at the Interaction Point (IP) of the Compact Muon
Solenoid (CMS) experiment. They provide both emittance and closed orbit
measurements at a bunch-by-bunch level. The precise measurement of beam-beam
closed orbit differences allowed a direct, quantitative observation of
long-range beam-beam PACMAN effects, which agrees well with numerical
simulations from an improved version of the TRAIN code
Data Analysis in Multimedia Quality Assessment: Revisiting the Statistical Tests
Assessment of multimedia quality relies heavily on subjective assessment, and
is typically done by human subjects in the form of preferences or continuous
ratings. Such data is crucial for analysis of different multimedia processing
algorithms as well as validation of objective (computational) methods for the
said purpose. To that end, statistical testing provides a theoretical framework
towards drawing meaningful inferences, and making well grounded conclusions and
recommendations. While parametric tests (such as t test, ANOVA, and error
estimates like confidence intervals) are popular and widely used in the
community, there appears to be a certain degree of confusion in the application
of such tests. Specifically, the assumption of normality and homogeneity of
variance is often not well understood. Therefore, the main goal of this paper
is to revisit them from a theoretical perspective and in the process provide
useful insights into their practical implications. Experimental results on both
simulated and real data are presented to support the arguments made. A software
implementing the said recommendations is also made publicly available, in order
to achieve the goal of reproducible research
The Global Risks Report 2016, 11th Edition
Now in its 11th edition, The Global Risks Report 2016 draws attention to ways that global risks could evolve and interact in the next decade. The year 2016 marks a forceful departure from past findings, as the risks about which the Report has been warning over the past decade are starting to manifest themselves in new, sometimes unexpected ways and harm people, institutions and economies. Warming climate is likely to raise this year's temperature to 1° Celsius above the pre-industrial era, 60 million people, equivalent to the world's 24th largest country and largest number in recent history, are forcibly displaced, and crimes in cyberspace cost the global economy an estimated US$445 billion, higher than many economies' national incomes. In this context, the Reportcalls for action to build resilience – the "resilience imperative" – and identifies practical examples of how it could be done.The Report also steps back and explores how emerging global risks and major trends, such as climate change, the rise of cyber dependence and income and wealth disparity are impacting already-strained societies by highlighting three clusters of risks as Risks in Focus. As resilience building is helped by the ability to analyse global risks from the perspective of specific stakeholders, the Report also analyses the significance of global risks to the business community at a regional and country-level
Resonant and random excitations on the proton beam in the Large Hadron Collider for active halo control with pulsed hollow electron lenses
We present the results of numerical simulations and experimental studies
about the effects of resonant and random excitations on proton losses,
emittances, and beam distributions in the Large Hadron Collider (LHC). In
addition to shedding light on complex nonlinear effects, these studies are
applied to the design of hollow electron lenses (HEL) for active beam halo
control. In the High-Luminosity Large Hadron Collider (HL-LHC), a considerable
amount of energy will be stored in the beam tails. To control and clean the
beam halo, the installation of two hollow electron lenses, one per beam, is
being considered. In standard electron-lens operation, a proton bunch sees the
same electron current at every revolution. Pulsed electron beam operation
(i.e., different currents for different turns) is also considered, because it
can widen the range of achievable halo removal rates. For an axially symmetric
electron beam, only protons in the halo are excited. If a residual field is
present at the location of the beam core, these particles are exposed to
time-dependent transverse kicks and to noise. We discuss the numerical
simulations and the experiments conducted in 2016 and 2017 at injection energy
in the LHC. The excitation patterns were generated by the transverse feedback
and damping system, which acted as a flexible source of dipole kicks. Proton
beam losses, emittances, and transverse distributions were recorded as a
function of excitation patterns and strengths. The resonant excitations induced
rich dynamical effects and nontrivial changes of the beam distributions, which,
to our knowledge, have not previously been observed and studied in this detail.
We conclude with a discussion of the tolerable and achievable residual fields
and proposals for further studies.Comment: 33 pages, 32 figures, 46 references. Revised manuscript submitted to
Phys. Rev. Accel. Beam
EEG source connectivity to localize the seizure onset zone in patients with drug resistant epilepsy
Visual inspection of the EEG to determine the seizure onset zone (SOZ) in the context of the presurgical evaluation in epilepsy is time-consuming and often challenging or impossible. We offer an approach that uses EEG source imaging (ESI) in combination with functional connectivity analysis (FC) to localize the SOZ from ictal EEG.
Ictal low-density-scalp EEG from 111 seizures in 27 patients who were rendered-seizure free after surgery was analyzed. For every seizure, ESI (LORETA) was applied on an artifact-free epoch selected around the seizure onset. Additionally, FC was applied on the reconstructed sources. We estimated the SOZ in two ways: (i)the source with highest power after ESI and (ii)the source with the most outgoing connections after ESI and FC. For both approaches, the distance between the estimated SOZ and the resected zone (RZ) of the patient were calculated.
Using ESI alone, the SOZ was estimated inside the RZ in 31% of the seizures and within 10mm from the border of the RZ in 42%. For 18.5% of the patients, all seizures were estimated within 10mm of the RZ. Using ESI and FC, 72% of the seizures were estimated inside the RZ, and 94% within 10mm. For 85% of the patients, all seizures were estimated within 10mm of the RZ. FC provided a significant added value to ESI alone (p<0.001).
ESI combined with subsequent FC is able to localize the SOZ in a non-invasive way with high accuracy. Therefore it could be a valuable tool in the presurgical evaluation of epilepsy
Numerical and experimental characterization of a railroad switch machine
This contribution deals with the numerical and experimental characterization of the structural behavior of a railroad switch machine. Railroad switch machines must meet a number of safety-related conditions such as, for instance, exhibiting the appropriate resistance against any undesired movements of the points due to the extreme forces exerted by a passing train. This occurrence can produce very high stress on the components, which has to be predicted by designers. In order to assist them in the development of new machines and in defining what the critical components are, FEA models have been built and stresses have been calculated on the internal components of the switch machine. The results have been validated by means of an ad-hoc designed experimental apparatus, now installed at the facilities of the Department of Industrial Engineering of the University of Bologna. This apparatus is particularly novel and original, as no Standards are available that provide recommendations for its design, and no previous studies have dealt with the development of similar rigs. Moreover, it has wide potential applications for lab tests aimed at assessing the safety of railroad switch machines and the fulfilment of the specifications by many railway companies
Regression Concept Vectors for Bidirectional Explanations in Histopathology
Explanations for deep neural network predictions in terms of domain-related
concepts can be valuable in medical applications, where justifications are
important for confidence in the decision-making. In this work, we propose a
methodology to exploit continuous concept measures as Regression Concept
Vectors (RCVs) in the activation space of a layer. The directional derivative
of the decision function along the RCVs represents the network sensitivity to
increasing values of a given concept measure. When applied to breast cancer
grading, nuclei texture emerges as a relevant concept in the detection of tumor
tissue in breast lymph node samples. We evaluate score robustness and
consistency by statistical analysis.Comment: 9 pages, 3 figures, 3 table
Atomically precise lateral modulation of a two-dimensional electron liquid in anatase TiO2 thin films
Engineering the electronic band structure of two-dimensional electron liquids
(2DELs) confined at the surface or interface of transition metal oxides is key
to unlocking their full potential. Here we describe a new approach to tailoring
the electronic structure of an oxide surface 2DEL demonstrating the lateral
modulation of electronic states with atomic scale precision on an unprecedented
length scale comparable to the Fermi wavelength. To this end, we use pulsed
laser deposition to grow anatase TiO2 films terminated by a (1 x 4) in-plane
surface reconstruction. Employing photo-stimulated chemical surface doping we
induce 2DELs with tunable carrier densities that are confined within a few TiO2
layers below the surface. Subsequent in-situ angle resolved photoemission
experiments demonstrate that the (1 x 4) surface reconstruction provides a
periodic lateral perturbation of the electron liquid. This causes strong
backfolding of the electronic bands, opening of unidirectional gaps and a
saddle point singularity in the density of states near the chemical potential
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