415 research outputs found

    Cross-project simulation of construction productivity for caisson fabrication

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    The aims are to (a) predict crew productivity improvement due to the repetitive nature of caisson fabrication as the result of on the job learning and (b) validate the previously specially built simulation platform CaissonSim' in different projects. More specifically, two such marine projects one in Greece and one in Cyprus have been studied

    Additively manufacturable micro-mechanical logic gates.

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    Early examples of computers were almost exclusively based on mechanical devices. Although electronic computers became dominant in the past 60 years, recent advancements in three-dimensional micro-additive manufacturing technology provide new fabrication techniques for complex microstructures which have rekindled research interest in mechanical computations. Here we propose a new digital mechanical computation approach based on additively-manufacturable micro-mechanical logic gates. The proposed mechanical logic gates (i.e., NOT, AND, OR, NAND, and NOR gates) utilize multi-stable micro-flexures that buckle to perform Boolean computations based purely on mechanical forces and displacements with no electronic components. A key benefit of the proposed approach is that such systems can be additively fabricated as embedded parts of microarchitected metamaterials that are capable of interacting mechanically with their surrounding environment while processing and storing digital data internally without requiring electric power

    Safety and patient outcomes with lubiprostone for up to 52 weeks in patients with irritable bowel syndrome with constipation

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    Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90244/1/apt4983.pd

    Nonprofit governance: Improving performance in troubled economic times

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    Nonprofit management is currently pressured to perform effectively in a weak economy. Yet, nonprofit governance continues to suffer from unclear conceptions of the division of labor between board of directors and executive directors. This online survey of 114 executive directors aims to provide clarification and recommendations for social administration

    Discontinuous transitions in double exchange materials

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    It is shown that the double exchange Hamiltonian, with weak antiferromagnetic interactions, has a rich variety of first order transitions between phases with different electronic densities and/or magnetizations. For band fillings in the range 0.3x0.50.3 \le x \le 0.5, and at finite temperatures, a discontinuous transition between phases with similar electronic densities but different magnetizations takes place. This sharp transition, which is not suppressed by electrostatic effects, and survives in the presence of an applied field, is consistent with the phenomenology of the doped manganites near the transition temperature.Comment: three more variational ansatzs considere

    Characterization of 30 76^{76}Ge enriched Broad Energy Ge detectors for GERDA Phase II

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    The GERmanium Detector Array (GERDA) is a low background experiment located at the Laboratori Nazionali del Gran Sasso in Italy, which searches for neutrinoless double beta decay of 76^{76}Ge into 76^{76}Se+2e^-. GERDA has been conceived in two phases. Phase II, which started in December 2015, features several novelties including 30 new Ge detectors. These were manufactured according to the Broad Energy Germanium (BEGe) detector design that has a better background discrimination capability and energy resolution compared to formerly widely-used types. Prior to their installation, the new BEGe detectors were mounted in vacuum cryostats and characterized in detail in the HADES underground laboratory in Belgium. This paper describes the properties and the overall performance of these detectors during operation in vacuum. The characterization campaign provided not only direct input for GERDA Phase II data collection and analyses, but also allowed to study detector phenomena, detector correlations as well as to test the strength of pulse shape simulation codes.Comment: 29 pages, 18 figure

    Background free search for neutrinoless double beta decay with GERDA Phase II

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    The Standard Model of particle physics cannot explain the dominance of matter over anti-matter in our Universe. In many model extensions this is a very natural consequence of neutrinos being their own anti-particles (Majorana particles) which implies that a lepton number violating radioactive decay named neutrinoless double beta (0νββ0\nu\beta\beta) decay should exist. The detection of this extremely rare hypothetical process requires utmost suppression of any kind of backgrounds. The GERDA collaboration searches for 0νββ0\nu\beta\beta decay of 76^{76}Ge (^{76}\rm{Ge} \rightarrow\,^{76}\rm{Se} + 2e^-) by operating bare detectors made from germanium with enriched 76^{76}Ge fraction in liquid argon. Here, we report on first data of GERDA Phase II. A background level of 103\approx10^{-3} cts/(keV\cdotkg\cdotyr) has been achieved which is the world-best if weighted by the narrow energy-signal region of germanium detectors. Combining Phase I and II data we find no signal and deduce a new lower limit for the half-life of 5.310255.3\cdot10^{25} yr at 90 % C.L. Our sensitivity of 4.010254.0\cdot10^{25} yr is competitive with the one of experiments with significantly larger isotope mass. GERDA is the first 0νββ0\nu\beta\beta experiment that will be background-free up to its design exposure. This progress relies on a novel active veto system, the superior germanium detector energy resolution and the improved background recognition of our new detectors. The unique discovery potential of an essentially background-free search for 0νββ0\nu\beta\beta decay motivates a larger germanium experiment with higher sensitivity.Comment: 14 pages, 9 figures, 1 table; ; data, figures and images available at http://www.mpi-hd.mpg/gerda/publi
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