12,026 research outputs found

    Non-equilibrium ionization around clouds evaporating in the interstellar medium

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    It is of prime importance for global models of the interstellar medium to know whether dense clouds do or do not evaporate in the hot coronal gas. The rate of mass exchanges between phases depends very much on that. McKee and Ostriker's model, for instance, assumes that evaporation is important enough to control the expansion of supernova remnants, and that mass loss obeys the law derived by Cowie and McKee. In fact, the geometry of the magnetic field is nearly unknown, and it might totally inhibit evaporation, if the clouds are not regularly connected to the hot gas. Up to now, the only test of the theory is the U.V. observation (by the Copernicus and IUE satellites) of absorption lines of ions such as OVI or NV, that exist at temperatures of a few 100,000 K typical of transition layers around evaporating clouds. Other means of testing the theory are discussed

    Energy dependence of the quark masses and mixings

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    The one loop Renormalization Group Equations for the Yukawa couplings of quarks are solved. From the solution we find the explicit energy dependence on t=lnE/μt=\ln E/\mu of the evolution of the {\em down} quark masses q=d,s,bq=d,s,b from the grand unification scale down to the top quark mass mtm_{t}. These results together with the earlier published evolution of the {\em up} quark masses completes the pattern of the evolution of the quark masses. We also find the energy dependence of the absolute values of the Cabibbo-Kobayashi-Maskawa (CKM) matrix Vij|V_{ij}|. The interesting property of the evolution of the CKM matrix and the ratios of the quark masses: mu,c/mtm_{u,c}/m_{t} and md,s/mbm_{d,s}/m_{b} is that they all depend on tt through only one function of energy h(t)h(t).Comment: Talk presented at the IX Mexican School on Particles and Fields, August 9-19, Metepec, Pue., Mexico. To be published in the AIP Conference Proceedings. 5 pages and 1 eps figure included in the tex

    Effectively four-dimensional spacetimes emerging from d=5 Einstein-Gauss-Bonnet Gravity

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    Einstein-Gauss-Bonnet gravity in five-dimensional spacetime provides an excellent example of a theory that, while including higher-order curvature corrections to General Relativity, still shares many of its features, such as second-order field equations for the metric. We focus on the largely unexplored case where the coupling constants of the theory are such that no constant-curvature solution is allowed, leaving open the question of what the vacuum state should then be. We find that even a slight deviation from the anti-de Sitter Chern-Simons theory, where the vacuum state is five-dimensional AdS spacetime, leads to a complete symmetry breakdown, with the fifth dimension either being compactified into a small circle or shrinking away exponentially with time. A complete family of solutions, including duality relations among them, is uncovered and shown to be unique within a certain class. This dynamical dimensional reduction scenario seems particularly attractive as a means for higher-dimensional theories to make contact with our four-dimensional world.Comment: 9 pages, 4 figures. v2: New section on geometrical significance of solutions. Final version for CQ

    Retrofit of an Historical Building toward NZEB

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    Abstract The European Directive on Energy Efficiency in Buildings (Directive 2010/31/EU) has introduced the need to transform buildings to nearly zero energy (NZEB) by 2020. Existing buildings represent the major part of the building stock and an interesting challenge is to transfer it toward NZEB. Energy retrofit is even more significant in Italy, where existing buildings stock (mainly residential) is also historic, so it's subject to environmental constraints or architectural-artistic value, and it's influenced by specific regulations and methods of intervention for refurbishment. In this case, the challenge becomes even more important and concerns both the building shell and the systems: retrofitting introduces not originally present in the complex; retrofit is not covered in the maintenance, since it represents an upgrade, an adaptation of the building, specifically in relation to energy efficiency, but also, by extension, other functions / features pertaining to the environment and sustainability. A case study of a radical refurbishment of an historical building is Ca' S. Orsola in Treviso. It is ruled by the Historical and Architectural Veneto Regional Authority. The building has been transformed into a prestigious residential complex by a major renovation that was aimed primarily seismic and energy upgrading. The energy and environmental performance of building have been analyzed by numerical simulation and experimental measurement in the EBC IEA Annex 56 [1] context with the aim to verify that intervention strategies respect to the reduction of energy consumption, the minimization of CO 2 emissions and maximizing the use of sources of renewable energy

    A unified methodology for heartbeats detection in seismocardiogram and ballistocardiogram signals

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    This work presents a methodology to analyze and segment both seismocardiogram (SCG) and ballistocardiogram (BCG) signals in a unified fashion. An unsupervised approach is followed to extract a template of SCG/BCG heartbeats, which is then used to fine-tune temporal waveform annotation. Rigorous performance assessment is conducted in terms of sensitivity, precision, Root Mean Square Error (RMSE) and Mean Absolute Error (MAE) of annotation. The methodology is tested on four independent datasets, covering different measurement setups and time resolutions. A wide application range is therefore explored, which better characterizes the robustness and generality of the method with respect to a single dataset. Overall, sensitivity and precision scores are uniform across all datasets (p > 0.05 from the Kruskal–Wallis test): the average sensitivity among datasets is 98.7%, with 98.2% precision. On the other hand, a slight yet significant difference in RMSE and MAE scores was found (p < 0.01) in favor of datasets with higher sampling frequency. The best RMSE scores for SCG and BCG are 4.5 and 4.8 ms, respectively; similarly, the best MAE scores are 3.3 and 3.6 ms. The results were compared to relevant recent literature and are found to improve both detection performance and temporal annotation errors

    Detection and analysis of heartbeats in seismocardiogram signals

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    This paper presents an unsupervised methodology to analyze SeismoCardioGram (SCG) signals. Starting from raw accelerometric data, heartbeat complexes are extracted and annotated, using a two-step procedure. An unsupervised calibration procedure is added to better adapt to different user patterns. Results show that the performance scores achieved by the proposed methodology improve over related literature: on average, 98.5% sensitivity and 98.6% precision are achieved in beat detection, whereas RMS (Root Mean Square) error in heartbeat interval estimation is as low as 4.6 ms. This allows SCG heartbeat complexes to be reliably extracted. Then, the morphological information of such waveforms is further processed by means of a modular Convolutional Variational AutoEncoder network, aiming at extracting compressed, meaningful representation. After unsupervised training, the VAE network is able to recognize different signal morphologies, associating each user to its specific patterns with high accuracy, as indicated by specific performance metrics (including adjusted random and mutual information score, completeness, and homogeneity). Finally, a Linear Model is used to interpret the results of clustering in the learned latent space, highlighting the impact of different VAE architectural parameters (i.e., number of stacked convolutional units and dimension of latent space)

    proposal of a methodology for achieving a leed o m certification in historic buildings

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    Abstract Nowadays resources are running out quickly, it's necessary to consider how the construction industry influences the environment using different materials and sources during all the building's life cycle. For this reason, in every transformation phases it's necessary to consider concepts as sustainability and green buildings. These are diffused from hundreds kind of green assessment tools, developed to measure sustainability goals in building sector and to compare the project with possible best practices or other green buildings. In this background, the rating system LEED (Leadership in Energy and Environmental Design) aims to examine and classify buildings according to energetic and environmental requirements. The particular LEED O+M (Building Operations and Maintenance) is developed for existing buildings undergoing improvement work or little to no construction and is based on the operative and management aspects. The certification process results, at a first analysis, hard to follow due to the complexity of internal parameters and the documentation required. The paper consists in a methodology and in an univocal work program of LEED O+M, trying to obtain the minimum requested certification score with optimization of the technical resources and documents. This methodology has application in a case study of historic building: the Ca' Rezzonico Museum, in the center of Venice

    Cost-Optimal measures for renovation of existing school buildings towards nZEB

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    Abstract The energy policies of the European Union (EU) encourage the member states to convert building stock into nearly Zero-Energy Buildings (nZEB) and national public authorities to adopt exemplary actions. Directive 2010/31/EU (EPBD recast) introduces the concept of nZEB as a building that has a very high energy performance and its energy need is covered to a very significant extent by energy from renewable sources (RES). Moreover the Directive refers to the cost-optimal methodology for fixing building energy requirements. This paper presents the results of the application of the cost-optimal methodology in a couple of existing school buildings located in the North East of Italy. The analysed buildings are a primary and a secondary schools that differ in construction period, in compactness ratio, in buildings envelope materials and systems. Several combinations of retrofit measures have been applied in order to derive cost-effective efficient solutions for retrofitting according to the methodology proposed by the project Annex56 "Cost Effective Energy & CO2 Emissions Optimization in Building Renovation". The cost-optimal level has been identified for each building and the best performing solutions have been selected considering a financial analysis and the application of "Conto Termico 2.0" government incentives. The results show the suitability of the proposed methodology to assess cost-optimality and energy efficiency in school building refurbishment. Moreover, this study shows different possibility providing the most cost-effective balance between costs and energy saving
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