Finite element optimizations for efficient non-linear electrical tomography reconstruction

Electrical Tomography can produce accurate results only if the underlying 2D or 3D volume discretization is chosen suitably for the applied numerical algorithm. We give general indications where and how to optimize a finite element discretization of a volume under investigation to enable efficient computation of potential distributions and the reconstruction of materials. For this, we present an error estimator and material-gradient indicator as a driver for adaptive mesh refinement and show how finite element mesh properties affect the efficiency and accuracy of the solutions

Epsilon Expansion for Multicritical Fixed Points and Exact Renormalisation Group Equations

The Polchinski version of the exact renormalisation group equations is applied to multicritical fixed points, which are present for dimensions between two and four, for scalar theories using both the local potential approximation and its extension, the derivative expansion. The results are compared with the epsilon expansion by showing that the non linear differential equations may be linearised at each multicritical point and the epsilon expansion treated as a perturbative expansion. The results for critical exponents are compared with corresponding epsilon expansion results from standard perturbation theory. The results provide a test for the validity of the local potential approximation and also the derivative expansion. An alternative truncation of the exact RG equation leads to equations which are similar to those found in the derivative expansion but which gives correct results for critical exponents to order $\epsilon$ and also for the field anomalous dimension to order $\epsilon^2$. An exact marginal operator for the full RG equations is also constructed.Comment: 40 pages, 12 figures version2: small corrections, extra references, final appendix rewritten, version3: some corrections to perturbative calculation

Relative entropy in 2d Quantum Field Theory, finite-size corrections and irreversibility of the Renormalization Group

The relative entropy in two-dimensional Field Theory is studied for its application as an irreversible quantity under the Renormalization Group, relying on a general monotonicity theorem for that quantity previously established. In the cylinder geometry, interpreted as finite-temperature field theory, one can define from the relative entropy a monotonic quantity similar to Zamolodchikov's c function. On the other hand, the one-dimensional quantum thermodynamic entropy also leads to a monotonic quantity, with different properties. The relation of thermodynamic quantities with the complex components of the stress tensor is also established and hence the entropic c theorems are proposed as analogues of Zamolodchikov's c theorem for the cylinder geometry.Comment: 5 pages, Latex file, revtex, reorganized to best show the generality of the results, version to appear in Phys. Rev. Let

EVALUATION OF THE ECOLOGICAL EFFECT OF BIODEGRADABLE WASTE PROCESSING IN A COMPREHENSIVE MUNICIPAL WASTE MANAGEMENT SYSTEM

AbstractRecycling of biodegradable waste is one of the trends in the recovery of organic matter together with its use for reclamation, but most importantly the reduction of biodegradable waste and the reduction of waste for disposal. The paper presents the use of the decision analysis method in the selection of the most advantageous organic recycling solution in a large agglomeration. The proposed method uses the tool of life cycle analysis (LCA) and decisional analysis

The doppler subspace of functional ultrasound imaging

Doppler ultrasound has a rich history, tracing back to advances in the field of sound navigation and ranging (sonar) after the sinking of the Titanic in 1912. In more recent times, it has flourished as a promising field of research, in part due to its contributions in the field of neuroscience through a technique built upon Doppler ultrasound, named functional ultrasound (fUS). With fUS imaging, we can track how the brain blood hemodynamics change over longer periods of time in response to a presented stimulation paradigm. fUS is an ultrasound imaging modality that is often compared to functional magnetic resonance imaging (fMRI), as they both measure proxies for neuronal activity. Due to its portability, price, and higher spatial/ temporal resolutions, fUS has proven to be a great tool for neuroscientific research.In this dissertation we present contributions to various stages of the Doppler ultrasound acquisition pipeline. This dissertation includes: a computationally efficient method for removing tissue clutter, analysis of the Doppler frequency spectrum during functional ultrasound recordings, a method for vessel orientation extraction to add directional information to the traditional power Doppler imaging, a method for the manufacturing of anatomically accurate Doppler ultrasound flow phantoms, and a novel method for volumetric Doppler imaging of the mouse brain using a 1D-array transducer, named Swept-3D.<br/

Exact Renormalization Group Equations. An Introductory Review

We critically review the use of the exact renormalization group equations (ERGE) in the framework of the scalar theory. We lay emphasis on the existence of different versions of the ERGE and on an approximation method to solve it: the derivative expansion. The leading order of this expansion appears as an excellent textbook example to underline the nonperturbative features of the Wilson renormalization group theory. We limit ourselves to the consideration of the scalar field (this is why it is an introductory review) but the reader will find (at the end of the review) a set of references to existing studies on more complex systems.Comment: Final version to appear in Phys. Rep.; Many references added, section 4.2 added, minor corrections. 65 pages, 6 fig

Energy calibration of the NEXT-White detector with 1% resolution near Q ββ of 136Xe

Excellent energy resolution is one of the primary advantages of electroluminescent high-pressure xenon TPCs. These detectors are promising tools in searching for rare physics events, such as neutrinoless double-beta decay (ββ0ν), which require precise energy measurements. Using the NEXT-White detector, developed by the NEXT (Neutrino Experiment with a Xenon TPC) collaboration, we show for the first time that an energy resolution of 1% FWHM can be achieved at 2.6 MeV, establishing the present technology as the one with the best energy resolution of all xenon detectors for ββ0ν searches. [Figure not available: see fulltext.

Sensitivity of a tonne-scale NEXT detector for neutrinoless double beta decay searches

The Neutrino Experiment with a Xenon TPC (NEXT) searches for the neutrinoless double-beta decay of Xe-136 using high-pressure xenon gas TPCs with electroluminescent amplification. A scaled-up version of this technology with about 1 tonne of enriched xenon could reach in less than 5 years of operation a sensitivity to the half-life of neutrinoless double-beta decay decay better than 1E27 years, improving the current limits by at least one order of magnitude. This prediction is based on a well-understood background model dominated by radiogenic sources. The detector concept presented here represents a first step on a compelling path towards sensitivity to the parameter space defined by the inverted ordering of neutrino masses, and beyond.Comment: 22 pages, 11 figure