242 research outputs found
Inter-vortex spacing in superfluid turbulence: temperature and Reynolds number dependences
No full textThe typical spacing between superfluid vortices in an isothermal turbulent tangle is proportional to the integral scale H rescaled by the quantum Reynolds number Re_K=H.V/K to the power of 3/4, where K is the quantum of circulation around of single vortex [Salort et al.,EPL 2011]. This empirical relation can be seen as the quantum-turbulence version of the corresponding well-know equation giving Kolmogorov dissipative scale in classical turbulence. In 2014, we studied the temperature dependence of the numerical factor (d/H).Re_K^{3/4} in 4He by joint numerical and experimental analysis of steady state turbulence over a wide temperature interval (1.2 - 2.16 K) [Babuin et al., EPL 2014]. Agreement between the two analyses was found good except at the very ends of this temperature interval. We will discuss this issue by presenting additional experimental data obtained by post-processing of superfluid experiments published between 1975 and 1998
Cosmological parameter estimation using Very Small Array data out to ℓ= 1500
No full textWe estimate cosmological parameters using data obtained by the Very Small Array (VSA) in its extended configuration, in conjunction with a variety of other cosmic microwave background (CMB) data and external priors. Within the flat Λ cold dark matter (ΛCDM) model, we find that the inclusion of high-resolution data from the VSA modifies the limits on the cosmological parameters as compared to those suggested by the Wilkinson Microwave Anisotropy Probe (WMAP) alone, while still remaining compatible with their estimates. We find that Ωbh2= 0.0234+0.0012−0.0014, Ωdmh2= 0.111+0.014−0.016, h= 0.73+0.09−0.05, nS= 0.97+0.06−0.03, 1010AS= 23+7−3 and τ= 0.14+0.14−0.07 for WMAP and VSA when no external prior is included. On extending the model to include a running spectral index of density fluctuations, we find that the inclusion of VSA data leads to a negative running at a level of more than 95 per cent confidence ( nrun=−0.069 ± 0.032 ), something that is not significantly changed by the inclusion of a stringent prior on the Hubble constant. Inclusion of prior information from the 2dF galaxy redshift survey reduces the significance of the result by constraining the value of Ωm. We discuss the veracity of this result in the context of various systematic effects and also a broken spectral index model. We also constrain the fraction of neutrinos and find that fν < 0.087 at 95 per cent confidence, which corresponds to mν < 0.32 eV when all neutrino masses are equal. Finally, we consider the global best fit within a general cosmological model with 12 parameters and find consistency with other analyses available in the literature. The evidence for nrun < 0 is only marginal within this model
From ornament to essence - represented by Gustav Klimt and Egon Schiele
No full textGraduate research paper for painting.AR 695, H.V.1979 Spring
2050 Midwest Structural Masterplan & A Transit Hub for St Louis
No full textThe project initiated with researching the condition of the Midwest, it’s major challenges and potential opportunities within the themes of infrastructure, energy, and landscape. After 5 months of research and analysis, the studio produced a 2050 Structural Masterplan for the Midwest. This masterplan involved a strategy for creating a unified, economically strengthened region along with a set of proposals that highlighted potential solutions to some of the specified challenges. This was executed through the lens of large-scale, top down, future vision planning in order to address very complex and challenging issues. Following the research and Masterplan design, each student selected their own site, project, and program within the context of the Midwest: a multi-modal transit hub (highlighting the increased value of passenger rail and the introduction of a maglev high speed rail) within St Louis (at the location of the existing passenger train station). The goal was to test the ideas of the 2050 Structural Masterplan of the Midwest within a city context and at a building scale. The St Louis Transit Hub focused on integrating multiple modes of transportation while providing a more inviting and welcoming experience into the city. This gateway experience became a guiding concept for the project, offering a gateway for the pedestrian, a gateway for the trains, and a symbolic gateway moment for the inhabitants of St Louis: a moment of passing from one mentality to another (an opportunity to offer education, awareness, and understanding about the challenges and opportunities). A gateway in three dimensions.MaterializationArchitectureArchitectur
Materializing Technologies: Surfacing Focal Things and Practices with Design
No full textToday, the world is populated with what we colloquially refer to as “black boxes.” These are technologies that perform sophisticated operations but obfuscate these complex operations, providing us with little context to what they do, how they work, and the role they play in our lives. In simple terms, this thesis addresses the following broadly framed questions: what parts of these black boxes should be made legible to the layperson? And regarding these parts: how can design be harnessed to reframe them as legible?Ethics & Philosophy of TechnologyHuman Information Communication Desig
Experiments on a natural circulation loop - from void fraction to nuclear
No full textApplied Science
Signal detection in fractional Gaussian noise and an RKHS approach to robust detection and estimation
No full textThis thesis is divided into two parts. In the first part, the problem of signal detection in fractional Gaussian noise is considered. To facilitate the study of this problem, several results related to the reproducing kernel Hilbert space of fractional Brownian motion are presented. In particular, this reproducing kernel Hilbert space is characterized completely and an alternative characterization for the restriction of this class of functions to a compact interval (0,T) is given. Infinite-interval whitening filters for fractional Brownian motion are also developed. Application of these results to the signal detection problem yields necessary and sufficient conditions for a deterministic or stochastic signal to produce a nonsingular shift when embedded in additive fractional Gaussian noise. Also, a formula for the likelihood ratio corresponding to any deterministic nonsingular shift is developed. Finally, some results concerning detector performance in the presence of additive fractional Gaussian noise are presented.In the second part of the thesis, the application of reproducing kernel Hilbert space theory to the problems of robust detection and estimation is investigated. It is shown that this approach provides a general and unified framework in which to analyze the problems of L\sp2 estimation, matched filtering, and quadratic detection in the presence of uncertainties regarding the second-order structure of the random processes involved. Minimax robust solutions to these problems are characterized completely, and some results concerning existence of robust solutions are presented.Made available in DSpace on 2011-05-07T14:14:57Z (GMT). No. of bitstreams: 2
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Difference-operator-based models in statistical signal processing
No full textDifference-operator-based models are an alternative to conventional shift-operator-based models for modeling stationary discrete-time random processes obtained by sampling continuous-time processes, when the sampling rate is rapid relative to the dynamics of the continuous-time process. In this regime, statistical signal processing procedures derived from the difference-operator-based models tend to be better-conditioned than their conventional analogues, resulting in better numerical performance when implemented using finite-precision arithmetic. Unlike the situation for shift-operator models, estimating the parameters of a difference-operator-based model involves solving a non-Toeplitz system of linear equations. We derive an algorithm for efficiently estimating these parameters, analogous to the Levinson algorithm for conventional models. Numerical results have been obtained that indicate that, in the presence of roundoff errors, the new algorithm gives better results than the Levinson algorithm. We also present a class of algorithms that solve for the model parameters by obtaining triangular factorizations of the covariance matrix of differenced data. These algorithms have the added advantage of not requiring the computation of any n-dimensional inner products, thus rendering them suitable for parallelization. They also suggest a lattice implementation of the modeling filter, in which the basic block is a discrete-time integrator, rather than a delay.Made available in DSpace on 2011-05-07T14:20:34Z (GMT). No. of bitstreams: 2
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No new cosmological concordance with massive sterile neutrinos
No full textIt has been claimed recently that massive sterile neutrinos could bring about a new concordance between observations of the cosmic microwave background, the large-scale structure of the Universe, and local measurements of the Hubble constant, H0. We demonstrate that this apparent concordance results from combining data sets which are in significant tension, even within this extended model, possibly indicating remaining systematic biases in the measurements. We further show that this tension remains when the cosmological model is further extended to include significant tensor modes, as suggested by the recent BICEP2 results. Using the Bayesian evidence, we show that the cold dark matter model with a cosmological constant is strongly favored over its neutrino extensions by various combinations of data sets. Robust data combinations yield stringent limits of ∑mν≲0.3 eV and meffν,sterile≲0.3 eV at 95% C.L. for the sum of active and sterile neutrinos, respectively
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