2,050 research outputs found

    Na-O Anticorrelation And HB I. The Na-O anticorrelation in NGC 2808

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    We derived atmospheric parameters and elemental abundances of Fe, O and Na for about 120 red giant stars in the Galactic globular cluster NGC 2808. Our results are based on the analysis of medium-high resolution (R=22000-24000) GIRAFFE spectra acquired with the FLAMES spectrograph at VLT-UT2 as a part of a project aimed at studying the Na-O anticorrelation as a function of physical parameters in globular clusters. We present here the anticorrelation of Na and O abundances in NGC 2808, and we discuss the distribution function of stars along this relation. Besides a bulk of O-normal stars, with composition typical of field halo stars, NGC 2808 seems to host two other groups of O-poor and super O-poor stars. In this regard, NGC 2808 is similar to M 13, the template cluster for the Na-O anticorrelation. However, at variance with M 13, most stars in NGC 2808 are O-rich. This might be related to the horizontal branch morphologies which are very different in these two clusters. The average metallicity we found for NGC 2808 is [Fe/H]=-1.10 (rms=0.065 dex, from 123 stars). We also found some evidence of a small intrinsic spread in metallicity, but more definitive conclusions are hampered by the presence of a small differential reddening.Comment: 12 pages, 6 tables, 7 figures. Accepted for publication on A&

    Smart Vehicle to Grid Interface Project: Electromobility Management System Architecture and Field Test Results

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    This paper presents and discusses the electromobility management system developed in the context of the SMARTV2G project, enabling the automatic control of plug-in electric vehicles' (PEVs') charging processes. The paper describes the architecture and the software/hardware components of the electromobility management system. The focus is put in particular on the implementation of a centralized demand side management control algorithm, which allows remote real time control of the charging stations in the field, according to preferences and constraints expressed by all the actors involved (in particular the distribution system operator and the PEV users). The results of the field tests are reported and discussed, highlighting critical issues raised from the field experience.Comment: To appear in IEEE International Electric Vehicle Conference (IEEE IEVC 2014

    Simultaneous management of renal carcinoma with caval vein thrombosis and double coronary artery disease

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    Introduction: Recent advances in surgical and anesthesiology techniques allow simultaneous thoracic and abdominal operations to be performed for severe heart disease and benignant or malignant abdominal diseases. Case report: The simultaneous surgical management in a 75-year-old patient suffering from severe double coronary artery disease and a renal cell carcinoma with extended intravascular growth into the inferior vena cava is reported. Conclusion: The postoperative course was uneventful. Simultaneous surgery proved to be beneficial and safe, showing optimal results in our patient

    Systematic mapping of power system models: Expert survey

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    The power system is one of the main subsystems of larger energy systems. It is a complex system in itself, consisting of an ever-changing infrastructure used by a large number of actors of very different sizes. The boundaries of the power system are characterised by ever-evolving interfaces with equally complex subsystems such as gas transport and distribution, heating and cooling, and, increasingly, transport. The situation is further complicated by the fact that electricity is only a carrier, able to fulfil demand for such things as lighting, heat or mobility. One specific and fundamental feature of the electricity system is that demand and generation must match at any time, while satisfying technical and economic constraints. In most of the world’s power systems, only relatively small quantities of electricity can be stored, and only for limited periods of time. A detailed analysis of supply and demand is thus needed for short time intervals. Mathematical models facilitate power system planning, operation, transmission and distribution, demonstrating problems that need to be solved over different timescales and horizons. The use of modelling to understand these processes is not only vital for the system’s direct actors, i.e. the companies involved in the generation, trade, transmission, distribution and use of electricity, but also for policy-makers and regulators. Power system models can provide evidence to support policy-making at European Union, Member State and Regional level. As a consequence of the growth in computing power, mathematical models for power systems have become more accessible. The number of models available worldwide, and the degree of detail they provide, is growing fast. A proper mapping of power system models is therefore essential in order to: - provide an overview of power system models and their applications available in, or used by, European organisations; - analyse their modelling features; - identify modelling gaps. Few reviews have been conducted to date of the power system modelling landscape. The mission of the Knowledge for the Energy Union Unit of the Joint Research Centre (JRC) is to support policies related to the Energy Union by anticipating, mapping, collating, analysing, quality checking and communicating all relevant data/knowledge, including knowledge gaps, in a systematic and digestible way. This report therefore constitutes: - From the energy modelling perspective, a useful mapping exercise that could help promote knowledge-sharing and thus increase efficiency and transparency in the modelling community. It could trigger new, unexplored avenues of research. It also represents an ideal starting point for systematic review activities in the context of the power system. - From the knowledge management perspective, a useful blueprint to be adopted for similar mapping exercises in other thematic areas. Finally, this report is aligned with the objectives of the European Commission's Competence Centre on Modelling, (1) launched on 26 October 2017 and hosted by the JRC, which aims to promote a responsible, coherent and transparent use of modelling to support the evidence base for European Union policies. In order to meet the objectives of this report, an online survey was used to collect detailed and relevant information about power system models. The participants’ answers were processed to categorise and describe the modelling tools identified. The survey, conducted by the Knowledge for the Energy Union Unit of the JRC, comprised a set of questions for each model to ascertain its basic information, its users, software characteristics, modelling properties, mathematical description, policy-making applications, selected references, and more. The survey campaign was organised in two rounds between April and July 2017. 228 surveys were sent to power system experts and organisations, and 82 questionnaires were completed. The answers were processed to map the knowledge objectively. (2) The main results of the survey can be summarised as follows: - Software-related features: about two thirds of the models require third-party software such as commercial optimisation solvers or off-the-shelf software. Only 14% of the models are open source, while 11% are free to download. - Modelling-related features: models are mostly defined as optimisation problems (78%) rather than simulation (33%) or equilibrium problems (13%). 71% of the models solve a deterministic problem while 41% solve probabilistic or stochastic problems. - Modelled power system problems: the economic dispatch problem is the most commonly modelled problem with a share of approximately 70%, followed by generation expansion planning, unit commitment, and transmission expansion planning, with around 40‒43% each. Most of the models (57%) have non-public input data while 31% of models use open input data. - Modelled technologies: hydro, wind, thermal, storage and nuclear technologies are widely taken into account, featuring in around 83‒94% of models. However, HVDC, wave tidal, PSTs, and FACTS (3) are not often found unless the analysis is specifically performed for those technologies. - Applicability in the context of European energy policy: more than half of the mapped models (56%) were used to answer a specific policy question. Of the five Energy Union strategic dimensions, integration of the European Union internal energy market was addressed the most often (27%), followed by climate action (23%), research, innovation and competitiveness (21%), and energy efficiency (15%). This report includes JRC recommendations based on the results of the survey, on future research avenues for power system modelling and its applicability within the Energy Union strategic dimensions. More attention should be paid, for example, to model uncertainty features, and collaboration among researchers and practitioners should be promoted to intensify research into specific power system problems such as AC (4) optimal power flow. The report includes factsheets for each model analysed, summarising relevant characteristics based on the participants’ answers. While this report represents a scientific result per se, one of the expected (and welcomed) outcomes of this mapping exercise is to raise awareness of power system modelling activities among European policy makers.JRC.C.7-Knowledge for the Energy Unio

    A masonry catalogue for the Groningen region

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    Human induced seismicity has become an uprising problem in the Groningen region of The Netherlands, in which the vast majority of buildings are non-seismically engineered unreinforced masonry houses. In order to accurately assess the seismic vulnerability of these buildings, a characterization of the constitutive masonry is required. In 2015, as a part of a larger project, a campaign on the material characterization of existing buildings was performed, including laboratory and in-situ testing of the masonry walls. The campaign constitutes the germ for the creation of a regional material properties database. 16 buildings were tested in total, comprising residential structures and schools, dating from the early ‘20s to 2005. The constitutive walls included both clay and calcium silicate brick masonry of various qualities and conditions. The in-situ testing included non-destructive tests such as rebound hammer and sonic tests, and semidestructive test, i.e. flat jack and shove test. Samples were carefully taken to the laboratory, where the destructive campaign took place, including compressive, flexural, shear and bond wrench tests. Despite of the limited number of sampled buildings, the campaign provided a better insight of the researched material. The available data suggests that the use of sub-typologies (e.g. depending of the masonry quality or condition) could reduce the dispersion on the results. A first attempt of correlation between in-situ and laboratory tests is proposed, which could benefit from further calibration. In this paper, the material characterization campaign is described, and the main outcomes are discussed

    Time and spatial filtering for echo reduction in antenna measurements

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    During the last years, new algorithms, based on time filtering, spatial or modal filtering, have been designed for echo reduction techniques applied to antenna measurements. These algorithms have been used for different applications where the effect of the echoes is important, as far field system, VHF or UHF applications, automotive systems, small antennas, etc. The authors, in previous papers, have analysed the effect of different algorithms: time filtering (fft, non uniform dft or matrix pencial), modal filtering based on Spherical modes (MV-Echo) and spatial filtering based on Integral Equations (Insight) and holographic techniques (fft and dft) to cancel the effect of the reflections. This comparison has been applied to the measurements of a dipole antenna (SD1900) using a StarLab system. It is observed that each of the algorithms is better for different situations, depending on the source of the echo. For instance, time filtering techniques are good for reflections coming from different distances with respect the direct ray, but not so good for close reflections. In addition hey need a large frequency band to work properly. Spatial algorithms can correct the effect of positioners or other structures close to the antenna under test, but they are better for planar near field acquisitions and worse for classical single probe spherical near field where the antenna is rotated and probe is fixed (e.g. roll-over-azimuths systems). Moreover, they require extra information of the AUT geometry. This paper presents first a comparison of each algorithm and then, a combination of time and spatial techniques based on uniform or non-uniform DFT to take advantage of the benefits of each algorithm for different origins of the reflections

    Prototype and mass production tests of avalanche photodiodes for the electromagnetic calorimeter in the ALICE experiment at LHC

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    Avalanche PhotoDiodes (APD) have been chosen as photonsensors for the new Electromagnetic Calorimeter (EMCal) of the ALICE experiment at the LHC. The size of the calorimeter requires the overall use of more than 12 000 APDs, all of which have to be tested and characterized individually. A procedure for the test of a large amount of APDs has been developed and is here described in detail, together with results from a first sample of devices

    Smoking influence in Takotsubo syndrome: insights from an international cohort

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    Takotsubo syndrome; Mortality; Smoking habitSíndrome de Takotsubo; Mortalidad; Hábito de fumarSíndrome de Takotsubo; Mortalitat; Hàbit de fumarAims: To assess the influence of tobacco on acute and long-term outcomes in Takotsubo syndrome (TTS). Methods: Patients with TTS from the international multicenter German Italian Spanish Takotsubo registry (GEIST) were analyzed. Comparisons between groups were performed within the overall cohort, and an adjusted analysis with 1:1 propensity score matching was conducted. Results: Out of 3,152 patients with TTS, 534 (17%) were current smokers. Smoker TTS patients were younger (63 ± 11 vs. 72 ± 11 years, p < 0.001), less frequently women (78% vs. 90%, p < 0.001), and had a lower prevalence of hypertension (59% vs. 69%, p < 0.01) and diabetes mellitus (16% vs. 20%, p = 0.04), but had a higher prevalence of pulmonary (21% vs. 15%, p < 0.01) and/or psychiatric diseases (17% vs. 12%, p < 0.01). On multivariable analysis, age less than 65 years [OR 3.85, 95% CI (2.86–5)], male gender [OR 2.52, 95% CI (1.75–3.64)], history of pulmonary disease [OR 2.56, 95% CI (1.81–3.61)], coronary artery disease [OR 2.35, 95% CI (1.60–3.46)], and non-apical ballooning form [OR 1.47, 95% CI (1.02–2.13)] were associated with smoking status. Propensity score matching (PSM) 1:1 yielded 329 patients from each group. Smokers had a similar rate of in-hospital complications but longer in-hospital stays (10 vs. 9 days, p = 0.01). During long-term follow-up, there were no differences in mortality rates between smokers and non-smokers (5.6% vs. 6.9% yearly in the overall, p = 0.02, and 6.6%, vs. 7.2% yearly in the matched cohort, p = 0.97). Conclusions: Our findings suggest that smoking may influence the clinical presentation and course of TTS with longer in-hospital stays, but does not independently impact mortality.FIC (Fundación Interhospitalaria para la Investigación en Cardiología) supported RETAKO
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