597 research outputs found
PCIExpress Communication Layer for ATCA-based Linear Accelerator Control System
PCIExpress architecture is widely used communication bus designed, among other things, for industrial application. Additionally, according to PICMG 3.4 specification it is part of an ATCA architecture. For that reason PCIExpress was used as communication interface for data transmission between ATCA carrier boards and AMC modules for the new control system for XFEL linear accelerator. In this paper authors present general overview of this system, describe communication protocols designed to exchange data with external user application and show results of performance test
Quiver Diagonalization and Open BPS States
We show that motivic Donaldson–Thomas invariants of a symmetric quiver Q, captured by the generating function P Q, can be encoded in another quiver Q (∞) of (almost always) infinite size, whose only arrows are loops, and whose generating function P Q (∞) is equal to P Q upon appropriate identification of generating parameters. Consequences of this statement include a generalization of the proof of integrality of Donaldson–Thomas and Labastida–Mariño–Ooguri–Vafa invariants that count open BPS states, as well as expressing motivic Donaldson–Thomas invariants of an arbitrary symmetric quiver in terms of invariants of m-loop quivers. In particular, this means that the already known combinatorial interpretation of invariants of m-loop quivers extends to arbitrary symmetric quivers
Permutohedra for knots and quivers
The knots-quivers correspondence states that various characteristics of a
knot are encoded in the corresponding quiver and the moduli space of its
representations. However, this correspondence is not a bijection: more than one
quiver may be assigned to a given knot and encode the same information. In this
work we study this phenomenon systematically and show that it is generic rather
than exceptional. First, we find conditions that characterize equivalent
quivers. Then we show that equivalent quivers arise in families that have the
structure of permutohedra, and the set of all equivalent quivers for a given
knot is parameterized by vertices of a graph made of several permutohedra glued
together. These graphs can be also interpreted as webs of dual 3d
theories. All these results are intimately related to
properties of homological diagrams for knots, as well as to multi-cover skein
relations that arise in counting of holomorphic curves with boundaries on
Lagrangian branes in Calabi-Yau three-folds.Comment: 72 pages, 36 figure
GEOMETRIC ANALYSIS BY CONSTRUCTAL DESIGN OF STIFFENED STEEL PLATES UNDER BENDING WITH TRANSVERSE I-SHAPED OR T-SHAPED STIFFENERS
Several stiffened plates arrangements subjected to bending were configured applying the Constructal Design Method (CDM) and solved by Finite Element Method (FEM), aiming through the Exhaustive Search (ES) technique analyze the influence of transverse I-Shaped or T-Shaped stiffeners in mechanical behavior. Considering a non-stiffened plate as reference and maintaining the total steel volume constant, a portion of the reference plate was deducted from its thickness, and transformed into stiffeners through the ???? volume fraction parameter, which represents the ratio between the steel volume of the stiffeners and the steel volume of the reference plate. Assuming ???? = 0.3, 25 plates with just I-Shaped stiffeners in longitudinal and transverse directions and 25 plates with I-Shaped stiffeners in longitudinal direction and T-Shaped stiffeners in transverse direction were proposed. The results showed that the plates with transverse T-Shaped stiffeners are more effective, reducing the maximum von Mises stress and maximum deflection, respectively, in up to more than 60% and 50% when compared with the plates with just I-Shaped stiffeners
A modified seasonal cycle during MIS31 super-interglacial favors stronger interannual ENSO and monsoon variability
It has long been recognized that the amplitude of the seasonal cycle can
substantially modify climate features in distinct timescales. This study
evaluates the impact of the enhanced seasonality characteristic of the Marine
Isotope Stage 31 (MIS31) on the El Niño–Southern Oscillation (ENSO). Based
upon coupled climate simulations driven by present-day
(CTR) and MIS31 boundary
conditions, we demonstrate that the CTR simulation shows a significant
concentration of power in the 3–7-year band and on the multidecadal
timescale between 15 and 30 years. However, the MIS31 simulation shows
drastically modified temporal variability of the ENSO, with stronger power
spectrum at interannual timescales but the absence of decadal periodicity.
Increased meridional gradient of sea surface temperature (SST) and wind
stress in the Northern Hemisphere subtropics are revealed to be the primary
candidates responsible for changes in the equatorial variability. The oceanic
response to the MIS31 ENSO extends to the extratropics, and fits nicely with
SST anomalies delivered by paleoreconstructions. The implementation of the
MIS31 conditions results in a distinct global monsoon system and its link to
the ENSO in respect to current conditions. In particular, the Indian monsoon
intensified but no correlation with ENSO is found in the MIS31 climate,
diverging from conditions delivered by our current climate in which this
monsoon is significantly correlated with the NIÑO34 index. This indicates
that monsoonal precipitation for this interglacial is more closely connected
to hemispherical features than to the tropical–extratropical climate
interaction.</p
Structural and optical investigation of non-polar (1-100) GaN grown by the ammonothermal method
We studied the structural and optical properties of state-of-the-art non-polar bulk GaN grown by the ammonothermal method. The investigated samples have an extremely low dislocation density (DD) of less than 5 × 104cm-2, which results in very narrow high-resolution x-ray rocking curves. The a and c lattice parameters of these stress-free GaN samples were precisely determined by using an x-ray diffraction technique based on the modified Bond method. The obtained values are compared to the lattice parameters of free-standing GaN from different methods and sources. The observed differences are discussed in terms of free-electron concentrations, point defects, and DD. Micro Raman spectroscopy revealed a very narrow phonon linewidth and negligible built-in strain in accordance with the high-resolution x-ray diffraction data. The optical transitions were investigated by cathodoluminescence measurements. The analysis of the experimental data clearly demonstrates the excellent crystalline perfection of ammonothermal GaN material and its potential for fabrication of non-polar substrates for homoepitaxial growth of GaN based device structures. © 2013 AIP Publishing LLC
Implication of backward contact tracing in the presence of overdispersed transmission in COVID-19 outbreaks
Introduction: Contact tracing has the potential to control outbreaks without the need for stringent physical distancing policies, e.g. civil lockdowns. Unlike forward contact tracing, backward contact tracing identifies the source of newly detected cases. This approach is particularly valuable when there is high individual-level variation in the number of secondary transmissions (overdispersion). Methods: By using a simple branching process model, we explored the potential of combining backward contact tracing with more conventional forward contact tracing for control of COVID-19. We estimated the typical size of clusters that can be reached by backward tracing and simulated the incremental effectiveness of combining backward tracing with conventional forward tracing. Results: Across ranges of parameter values consistent with dynamics of SARS-CoV-2, backward tracing is expected to identify a primary case generating 3-10 times more infections than a randomly chosen case, typically increasing the proportion of subsequent cases averted by a factor of 2-3. The estimated number of cases averted by backward tracing became greater with a higher degree of overdispersion. Conclusion: Backward contact tracing can be an effective tool for outbreak control, especially in the presence of overdispersion as is observed with SARS-CoV-2
Trump vs. Hillary: What went Viral during the 2016 US Presidential Election
In this paper, we present quantitative and qualitative analysis of the top
retweeted tweets (viral tweets) pertaining to the US presidential elections
from September 1, 2016 to Election Day on November 8, 2016. For everyday, we
tagged the top 50 most retweeted tweets as supporting or attacking either
candidate or as neutral/irrelevant. Then we analyzed the tweets in each class
for: general trends and statistics; the most frequently used hashtags, terms,
and locations; the most retweeted accounts and tweets; and the most shared news
and links. In all we analyzed the 3,450 most viral tweets that grabbed the most
attention during the US election and were retweeted in total 26.3 million times
accounting over 40% of the total tweet volume pertaining to the US election in
the aforementioned period. Our analysis of the tweets highlights some of the
differences between the social media strategies of both candidates, the
penetration of their messages, and the potential effect of attacks on bothComment: Paper to appear in Springer SocInfo 201
Characteristics of human encounters and social mixing patterns relevant to infectious diseases spread by close contact: a survey in Southwest Uganda.
BACKGROUND: Quantification of human interactions relevant to infectious disease transmission through social contact is central to predict disease dynamics, yet data from low-resource settings remain scarce. METHODS: We undertook a social contact survey in rural Uganda, whereby participants were asked to recall details about the frequency, type, and socio-demographic characteristics of any conversational encounter that lasted for ≥5 min (henceforth defined as 'contacts') during the previous day. An estimate of the number of 'casual contacts' (i.e. < 5 min) was also obtained. RESULTS: In total, 566 individuals were included in the study. On average participants reported having routine contact with 7.2 individuals (range 1-25). Children aged 5-14 years had the highest frequency of contacts and the elderly (≥65 years) the fewest (P < 0.001). A strong age-assortative pattern was seen, particularly outside the household and increasingly so for contacts occurring further away from home. Adults aged 25-64 years tended to travel more often and further than others, and males travelled more frequently than females. CONCLUSION: Our study provides detailed information on contact patterns and their spatial characteristics in an African setting. It therefore fills an important knowledge gap that will help more accurately predict transmission dynamics and the impact of control strategies in such areas
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