Conservative boundary conditions for 3D gas dynamics problems

A method is described for 3D-gas dynamics computer simulation in regions of complicated shape by means of nonadjusted rectangular grids providing unified treatment of various problems. Some test problem computation results are given

Study of corrections for anomalous coupling limits due to the possible background BSM contributions

The search of the anomalous couplings is one of the possible ways to find any deviation from the Standard Model. The effective field theory is used to parameterize the anomalous couplings in the Lagrangian with the operators of higher dimensions, constructed from the SM fields. In the classical way, the limits on the Wilson coefficients of these operators are set based on beyond the Standard Model contributions induced for signal process, whereas the ones induced for background processes are assumed to be negligible. This article provides a study of the corrections to the limits on Wilson coefficients by accounting beyond the Standard Model contributions induced for background processes. The studies of $Z(\nu\bar{\nu})\gamma jj$ and $W(\ell\nu)\gamma jj$ productions in $pp$ collisions with $\sqrt{s}=13$ TeV and conditions of the ATLAS experiment at the LHC are used as example. Cases of collected during Run II and expected from Run III integrated luminosities of 139 fb$^{-1}$ and 300 fb$^{-1}$ are considered. The expected 95% CL limits on coefficients $f_\text{T0}/\Lambda^4$, $f_\text{T5}/\Lambda^4$, $f_\text{M0}/\Lambda^4$ and $f_\text{M2}/\Lambda^4$ are obtained both in classical way and in the way, where the corrections from background anomalous contributions are applied. Corrected one-dimensional limits from $Z(\nu\bar{\nu})\gamma jj$ and $W(\ell\nu)\gamma jj$ productions are up to 9.1% and 4.4% (depending on operator) tighter than the classical ones respectively. Corrected combined limits are up to 3.0% (depending on operator) tighter than the classical ones. Corrections to two-dimensional limits are also obtained, corrected contours are more stringent, than the classical ones, and the maximal improvement is of 17.2%

Off-the-beaten-path Solutions for Decomposition-based Zero-forcing Precoding in xDSL Multi-user Downlinks

However broad the Decomposition-based Zero-forcing (DBZF) precoder acceptance may be, reducing the computational complexity of its implementation is an absolute necessity for the VDSL networking professionals. The paper digs deeper into this problem from the perspective of matrix inversion which is inherent in the very nature of the DBZF. Five strategies considered here differ in mode of action: three of them include matrix inversion, and two others drop implementing the procedure. While the baseline strategy itemized under No. 1 acts with the Gaussian LU-decomposition, strategy No. 2 deals with the Jordanian LU-decomposition thereby enabling mild reduction of the operation count. Strategy No. 3 works for more significant reduction as it operates with the elimination form of the inverse matrix. The most cost-cutting are strategies excluding the question of matrix inversion and replacing it by far more straightforward linear system solution, as it is in Strategy No. 4. An alternative strategy No. 5 uses the least squares-based square-root-type sequential system solution and it is the most accurate computational procedure when compared with other strategies

Numerically Efficient Kalman Filter Based Channel Estimation for OFDM Data Transmission

Channel estimation and prediction algorithms are developed for use in broadband OFDM data transmission over non-ideal channels. The scalar complex channel coefficients are described by Gauss–Markov AR models of a given order in state space form to model the channel fading statistics. On this basis, the conventional Kalman filtering and prediction algorithm (CKFPA) is presented as a starting point for further development. A novel numerically stable channel estimation algorithm based on the original KFPA solution, the so-called extended Array UD Covariance Filter (eUD-CF) algorithm, is developed. The accuracy of the eUD-CF estimator is analyzed by the method of computational experimentation. The simulation results demonstrate that the developed algorithm can effectively restrain the CKFPAs instability problem. The aspects of a parallel implementation of the suggested algorithms are also considered

Linkages between the circulation and distribution of dissolved organic matter in the White Sea, Arctic Ocean

AbstractThe White Sea is a semi-enclosed Arctic marginal sea receiving a significant loading of freshwater (225–231km3yr−1 equaling an annual runoff yield of 2.5m) and dissolved organic matter (DOM) from river run-off. We report discharge weighed values of stable oxygen isotope ratios (δ18O) of −14.0‰ in Northern Dvina river for the period 10 May–12 October 2012. We found a significant linear relationship between salinity (S) and δ18O (δ18O=−17.66±0.58+0.52±0.02×S; R2=0.96, N=162), which indicates a dominant contribution of river water to the freshwater budget and little influence of sea ice formation or melt. No apparent brine additions from sea-ice formation is evident in the White Sea deep waters as seen from a joint analysis of temperature (T), S, δ18O and aCDOM(350) data, confirming previous suggestions about strong tidal induced vertical mixing in winter being the likely source of the deep waters. We investigated properties and distribution of colored dissolved organic matter (CDOM) and dissolved organic carbon (DOC) in the White Sea basin and coastal areas in summer. We found contrasting DOM properties in the inflowing Barents Sea waters and White Sea waters influenced by terrestrial runoff. Values of absorption by CDOM at 350nm (aCDOM(350)) and DOC (exceeding 10m−1 and 550µmoll−1, respectively) in surface waters of the White Sea basin are higher compared to other river-influenced coastal Arctic domains. Linear relationship between S and CDOM absorption, and S and DOC (DOC=959.21±52.99–25.80±1.79×S; R2=0.85; N=154) concentrations suggests conservative mixing of DOM in the White Sea. The strongest linear correlation between CDOM absorption and DOC was found in the ultraviolet (DOC=56.31±2.76+9.13±0.15×aCDOM(254); R2=0.99; N=155), which provides an easy and robust tool to trace DOC using CDOM absorption measurements as well as remote sensing algorithms. Deviations from this linear relationship in surface waters likely indicate contribution from different rivers along the coast of the White Sea. Characteristics of CDOM further indicate that there is limited removal or change in the DOM pool before it exits to the Barents Sea

Measurement of electroweak Z(νν) γjj production and limits on anomalous quartic gauge couplings in pp collisions at s√ = 13 TeV with the ATLAS detector

The electroweak production of Z(νν¯¯¯)γ in association with two jets is studied in a regime with a photon of high transverse momentum above 150 GeV using proton–proton collisions at a centre-of-mass energy of 13 TeV at the Large Hadron Collider. The analysis uses a data sample with an integrated luminosity of 139 fb−1 collected by the ATLAS detector during the 2015–2018 LHC data-taking period. This process is an important probe of the electroweak symmetry breaking mechanism in the Standard Model and is sensitive to quartic gauge boson couplings via vector-boson scattering. The fiducial Z(νν¯¯¯)γjj cross section for electroweak production is measured to be 0.77+0.34−0.30 fb and is consistent with the Standard Model prediction. Evidence of electroweak Z(νν¯¯¯)γjj production is found with an observed significance of 3.2σ for the background-only hypothesis, compared with an expected significance of 3.7σ. The combination of this result with the previously published ATLAS observation of electroweak Z(νν¯¯¯)γjj production yields an observed (expected) signal significance of 6.3σ (6.6σ). Limits on anomalous quartic gauge boson couplings are obtained in the framework of effective field theory with dimension-8 operators

Measurement of electroweak Z(νν¯)γjj production and limits on anomalous quartic gauge couplings in pp collisions at √s = 13 TeV with the ATLAS detector

The electroweak production of Z(νν¯)γ in association with two jets is studied in a regime with a photon of high transverse momentum above 150 GeV using proton–proton collisions at a centre-of-mass energy of 13 TeV at the Large Hadron Collider. The analysis uses a data sample with an integrated luminosity of 139 fb−1 collected by the ATLAS detector during the 2015–2018 LHC data-taking period. This process is an important probe of the electroweak symmetry breaking mechanism in the Standard Model and is sensitive to quartic gauge boson couplings via vector-boson scattering. The fiducial Z(νν¯)γjj cross section for electroweak production is measured to be 0.77+0.34−0.30 fb and is consistent with the Standard Model prediction. Evidence of electroweak Z(νν¯)γjj production is found with an observed significance of 3.2σ for the background-only hypothesis, compared with an expected significance of 3.7σ. The combination of this result with the previously published ATLAS observation of electroweak Z(νν¯)γjj production yields an observed (expected) signal significance of 6.3σ (6.6σ). Limits on anomalous quartic gauge boson couplings are obtained in the framework of effective field theory with dimension-8 operators

Study of non-collision background from cosmic muons

This report describes the work done as CERN Summer Student project. One of the unavoidable non-collision backgrounds in the experiments at the Large Hadron Collider is the background from cosmic muons. In this work the flow of the cosmic muons is considered and events with cosmic muons and ATLAS detector are simulated. As a result the contribution of cosmic muons to events reconstructed with the ATLAS detector from pp-collisions is estimated