Study of hot wire techniques in low density flows with high turbulence levels

Prediction of heat, mass, species, and momentum fluxes in a space vehicle and aerodynamic noise production by supersonic jet and rocket exhausts requires a predictability of the associated turbulence fields. The hot wire is a technique that will allow an experimental determination of turbulent properties

Transfer of excitation energy from nitrogen molecules to sodium atoms

Transfer of excitation energy from nitrogen molecules to sodium atom

Coarse Graining Makes It Hard to See Micro-Macro Entanglement

Observing quantum effects such as superpositions and entanglement in macroscopic systems requires not only a system that is well protected against environmental decoherence, but also sufficient measurement precision. Motivated by recent experiments, we study the effects of coarse-graining in photon number measurements on the observability of micro-macro entanglement that is created by greatly amplifying one photon from an entangled pair. We compare the results obtained for a unitary quantum cloner, which generates micro-macro entanglement, and for a measure-and-prepare cloner, which produces a separable micro-macro state. We show that the distance between the probability distributions of results for the two cloners approaches zero for a fixed moderate amount of coarse-graining. Proving the presence of micro-macro entanglement therefore becomes progressively harder as the system size increases.Comment: 5 pages, 3 figure

Dark Energy Survey Year 1 Results: Multi-Probe Methodology and Simulated Likelihood Analyses

We present the methodology for and detail the implementation of the Dark Energy Survey (DES) 3x2pt DES Year 1 (Y1) analysis, which combines configuration-space two-point statistics from three different cosmological probes: cosmic shear, galaxy-galaxy lensing, and galaxy clustering, using data from the first year of DES observations. We have developed two independent modeling pipelines and describe the code validation process. We derive expressions for analytical real-space multi-probe covariances, and describe their validation with numerical simulations. We stress-test the inference pipelines in simulated likelihood analyses that vary 6-7 cosmology parameters plus 20 nuisance parameters and precisely resemble the analysis to be presented in the DES 3x2pt analysis paper, using a variety of simulated input data vectors with varying assumptions. We find that any disagreement between pipelines leads to changes in assigned likelihood Δχ^2 ≤ 0.045 with respect to the statistical error of the DES Y1 data vector. We also find that angular binning and survey mask do not impact our analytic covariance at a significant level. We determine lower bounds on scales used for analysis of galaxy clustering (8 Mpc h^(−1)) and galaxy-galaxy lensing (12 Mpc h^(−1)) such that the impact of modeling uncertainties in the non-linear regime is well below statistical errors, and show that our analysis choices are robust against a variety of systematics. These tests demonstrate that we have a robust analysis pipeline that yields unbiased cosmological parameter inferences for the flagship 3x2pt DES Y1 analysis. We emphasize that the level of independent code development and subsequent code comparison as demonstrated in this paper is necessary to produce credible constraints from increasingly complex multi-probe analyses of current data

Active Brownian particles with velocity-alignment and active fluctuations

We consider a model of active Brownian particles with velocity-alignment in two spatial dimensions with passive and active fluctuations. Hereby, active fluctuations refers to purely non-equilibrium stochastic forces correlated with the heading of an individual active particle. In the simplest case studied here, they are assumed as independent stochastic forces parallel (speed noise) and perpendicular (angular noise) to the velocity of the particle. On the other hand, passive fluctuations are defined by a noise vector independent of the direction of motion of a particle, and may account for example for thermal fluctuations. We derive a macroscopic description of the active Brownian particle gas with velocity-alignment interaction. Hereby, we start from the individual based description in terms of stochastic differential equations (Langevin equations) and derive equations of motion for the coarse grained kinetic variables (density, velocity and temperature) via a moment expansion of the corresponding probability density function. We focus here in particular on the different impact of active and passive fluctuations on the onset of collective motion and show how active fluctuations in the active Brownian dynamics can change the phase-transition behaviour of the system. In particular, we show that active angular fluctuation lead to an earlier breakdown of collective motion and to emergence of a new bistable regime in the mean-field case.Comment: 5 figures, 22 pages, submitted to New Journal of Physic

The emerging communication architecture in electrical energy supply and its implications

In the course of liberalisation of the electrical energy market, the pressure on the utilities to reduce their investment and maintenance costs is increasing. In order to lower these expenses and to be able to offer a more efficient supply with electrical energy, the utilities are increasingly using modern communication techniques. Control mechanisms that have been realized with a huge amount of hardware so far are more and more replaced by softwarebased solutions. Major points of concern in the near future are the standardisation of communication interfaces and protocols, as well as the implementation of autonomously acting entities performing vitally important actions like controlling protective systems

Study of the optimal conditions for NV- center formation in type 1b diamond, using photoluminescence and positron annihilation spectroscopies

We studied the parameters to optimize the production of negatively-charged nitrogen-vacancy color centers (NV-) in type~1b single crystal diamond using proton irradiation followed by thermal annealing under vacuum. Several samples were treated under different irradiation and annealing conditions and characterized by slow positron beam Doppler-broadening and photoluminescence (PL) spectroscopies. At high proton fluences another complex vacancy defect appears limiting the formation of NV-. Concentrations as high as 2.3 x 10^18 cm^-3 of NV- have been estimated from PL measurements. Furthermore, we inferred the trapping coefficient of positrons by NV-. This study brings insight into the production of a high concentration of NV- in diamond, which is of utmost importance in ultra-sensitive magnetometry and quantum hybrid systems applications

Coulombic Energy Transfer and Triple Ionization in Clusters

Using neon and its dimer as a specific example, it is shown that excited Auger decay channels that are electronically stable in the isolated monomer can relax in a cluster by electron emission. The decay mechanism, leading to the formation of a tricationic cluster, is based on an efficient energy-transfer process from the excited, dicationic monomer to a neighbor. The decay is ultrafast and expected to be relevant to numerous physical phenomena involving core holes in clusters and other forms of spatially extended atomic and molecular matter.Comment: 5 pages, 1 figure, to be published in PR

Radio Continuum Jet in NGC 7479

The barred galaxy NGC 7479 hosts a remarkable jet-like radio continuum feature: bright, 12-kpc long in projection, and hosting an aligned magnetic field. The degree of polarization is 6%-8% along the jet, and remarkably constant, which is consistent with helical field models. The radio brightness of the jet suggests strong interaction with the ISM and hence a location near the disk plane. We observed NGC 7479 at four wavelengths with the VLA and Effelsberg radio telescopes. The equipartition strength is 35-40 micro-G for the total and >10 micro-G for the ordered magnetic field in the jet. The jet acts as a bright, polarized background. Faraday rotation between 3.5 and 6 cm and depolarization between 6 and 22 cm can be explained by magneto-ionic gas in front of the jet, with thermal electron densities of ~0.06 cm**(-3) in the bar and ~0.03 cm**(-3) outside the bar. The regular magnetic field along the bar points toward the nucleus on both sides. The regular field in the disk reveals multiple reversals, probably consisting of field loops stretched by a shearing gas flow in the bar. The projection of the jet bending in the sky plane is in the sense opposite to that of the underlying stellar and gaseous spiral structure. The bending in 3-D is most easily explained as a precessing jet, with an age less than 10**6 years. Our observations are consistent with very recent triggering, possibly by a minor merger. NGC 7479 provides a unique opportunity to study interaction-triggered 15-kpc scale radio jets within a spiral galaxy.Comment: 18 pages, 21 figures, accepted for publication in the Astrophysical Journa

Thermophysical and chemical characterization of charring ablative materials Final report

Thermophysical and chemical properties of charring ablative material