2 resultados para Large type books

em Universidad de Alicante


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The discovery of very slow pulsations (Pspin =5560 s) has solved the long-standing question of the nature of the compact object in the high-mass X-ray binary 4U 2206+54 but has posed new ones. According to spin evolutionary models in close binary systems, such slow pulsations require a neutron star magnetic field strength larger than the quantum critical value of 4.4 × 1013 G, suggesting the presence of a magnetar. We present the first XMM–Newton observations of 4U 2206+54 and investigate its spin evolution. We find that the observed spin-down rate agrees with the magnetar scenario. We analyse Integral Spacecraft Gamma-Ray Imager (ISGRI)/INTErnational Gamma-RAy Laboratory (INTEGRAL) observations of 4U 2206+54 to search for the previously suggested cyclotron resonance scattering feature at ∼30 keV. We do not find a clear indication of the presence of the line, although certain spectra display shallow dips, not always at 30 keV. The association of these dips with a cyclotron line is very dubious because of its apparent transient nature. We also investigate the energy spectrum of 4U 2206+54 in the energy range 0.3–10 keV with unprecedented detail and report for the first time the detection of very weak 6.5 keV fluorescence iron lines. The photoelectric absorption is consistent with the interstellar value, indicating very small amount of local matter, which would explain the weakness of the florescence lines. The lack of matter locally to the source may be the consequence of the relatively large orbital separation of the two components of the binary. The wind would be too tenuous in the vicinity of the neutron star.

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As BIM adoption continues, the goal of a totally collaborative model with multiple contributors is attainable. Many initiatives such as the 2016 UK government level 2 BIM deadline are putting pressure on the construction industry to speed up the changeover. Clients and collaborators have higher expectations of using digital 3D models to communicate design ideas and solve practical problems. Contractors and clients are benefitting from cost saving scheduling and clash detection offered by BIM. Effective collaboration on the project will also give speed and efficiency gains. Despite this, many businesses of varying sizes are still having problems. The cost of the software and the training provides an obvious barrier for micro-enterprises and could explain a delay in adoption. Many studies have looked at these problems faced by SME and micro-enterprises. Larger companies have different problems. The efforts made by government to encourage them are quite comprehensive, but is anything being done to help smaller sectors and keep the industry cohesive? This limited study examines several companies of varying size and varying project type: architectural design businesses, main contractor, structural engineer and building consultancy. The study examines the barriers to a truly collaborative BIM workflow facing different specialities on a larger project and a contrasting small/medium project. The findings will establish that different barriers for each sector are actually pushing further apart, thus potentially creating a BIM-only construction elite, leaving the small companies remaining on 2D based drawing.