827 research outputs found

    Design of the Hull Structure of Double-Ended Ferries for the Adriatic

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    The main topic of this paper is a hull structure design of an 80 m double-ended ferry, intended for navigation in the Adriatic Sea. The structural ship elements were dimensioned according to the rules of the Croatian Ship Register using the Mathcad software. The preliminary drawing of the main midship frame was made in AutoCAD. Then follows the verification of previously calculated primary structural elements using beam finite element method model (DNV 3D-Beam software). The obtained results of main deck model and the racking model meet the strength criteria. Docking stress of the bottom structure was also checked and meets the strength criteria. Furthermore, the distribution of global longitudinal stresses in midship section is verified using the finite element method in DNV GeniE software

    Summer drought predictability over Europe: empirical versus dynamical forecasts

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    Seasonal climate forecasts could be an important planning tool for farmers, government and insurance companies that can lead to better and timely management of seasonal climate risks. However, climate seasonal forecasts are often under-used, because potential users are not well aware of the capabilities and limitations of these products. This study aims at assessing the merits and caveats of a statistical empirical method, the ensemble streamflow prediction system (ESP, an ensemble based on reordering historical data) and an operational dynamical forecast system, the European Centre for Medium-Range Weather Forecasts—System 4 (S4) in predicting summer drought in Europe. Droughts are defined using the Standardized Precipitation Evapotranspiration Index for the month of August integrated over 6 months. Both systems show useful and mostly comparable deterministic skill. We argue that this source of predictability is mostly attributable to the observed initial conditions. S4 shows only higher skill in terms of ability to probabilistically identify drought occurrence. Thus, currently, both approaches provide useful information and ESP represents a computationally fast alternative to dynamical prediction applications for drought prediction.We acknowledge the NOAA/OAR/ESRL PSD, Boulder, Colorado, USA, for making the data available on their website http://www.esrl.noaa.gov/psd/. This work was partially funded by the Projects IMPREX (EU–H2020 PE024400) and SPECS (FP7-ENV-2012-308378). Marco Turco was supported by the Spanish Juan de la Cierva Programme (IJCI-2015-26953).Peer ReviewedPostprint (published version

    Acquisition of Conceptual Design Knowledge in Structural Engineering

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    Expert systems integrating fuzzy reasoning techniques represent a powerful tool to support practicing engineers during the early stages of structural design. In this context fuzzy models have proved themselves to be very suitable for the representation of complex design knowledge. However their definition is a laborious task. This paper introduces an approach for the design and the optimization of fuzzy systems based upon Genetic Programming. To keep the emerging fuzzy systems transparent a new framework for the definition of linguistic variables is also introduced

    Dendroarchaeology of Sovjan - the first Early Bronze Age dendrochronological analysis from the southwestern Balkans (Albania)

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    The archaeological site of Sovjan is situated on the north-western edge of the Korçë Basin, south-eastern Albania. The stratigraphy of Sovjan spans from the Neolithic till the Bronze Age. The thoroughly investigated stratigraphic sequence of the site makes it one of the most important prehistoric reference-sites in Albania and the surrounding region. During prehistory Sovjan was situated at various distances from the shores of the former Lake Maliq, which once filled the Korçë Basin, but was definitely drained after the 1940s. The waterlogged conditions on the site allowed for a high degree of preservation of wooden remains. From the two uncovered dwellings from layer 8, the Maison du Canal (House on the Canal) represents probably the best-preserved wooden structure from the Bronze Age Balkans. The predominant use of deciduous oak wood (Quercus spp.) is confirmed in this phase. Through a combination of dendrochronological analysis and 14C-dates (wiggle matching), we were able to define a high-precision chronological placement of the layer with an end-date range falling between 2158 and 2142 cal BC (2σ), the second half of the Early Bronze Age. It was confirmed that the two dwellings and the trackway were built in the same construction event, made of both worked and unworked wood. The utilized construction timber falls into various age-classes, suggesting variable exploitation of the woodland resources. Additionally, through Bayesian modelling of the previously published 14C dates from the transitional layer 7, its chronological placement is narrowed-down to the 22nd – 20th century BC. These new results suggest the contemporaneity of the processes in the Balkan ‘hinterland’ with those occurring in the wider Aegean region

    Absolutely dating the European Neolithic through a rapid 14C excursion.

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    The discovery of abrupt radiocarbon (14C) excursions (Solar Energetic Particle events, or Miyake events) in sequences of radiocarbon measurements from calendar dated tree-rings, has yielded new opportunities to assign absolute, calendar dates to undated wood samples from widely ranging contexts in history and prehistory. We report on an important tree-ring and 14C-dating based study, which secures the Neolithic site of Dispilio, Northern Greece, a key site for the Aegean Neolithic, in absolute, calendar-dated time using the Miyake event of 5259 BC. The last ring of the 303-year-long juniper tree-ring chronology from Dispilio is dated to 5140 BC. Dispilio is thus the first prehistoric site absolutely dated through a 14C signature (Miyake event), but also the first absolutely, calendar-year dated prehistoric site in the wider Mediterranean region

    Severe Atherosclerosis and Hypercholesterolemia in Mice Lacking Both the Melanocortin Type 4 Receptor and Low Density Lipoprotein Receptor

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    Dysfunction of the melanocortin system can result in severe obesity accompanied with dyslipidemia and symptoms of the metabolic syndrome but the effect on vascular atherogenesis is not known. To study the impact of obesity and dyslipidemia on the cardiovascular system, we generated mice double-deficient for the melanocortin type 4 receptor (Mc4r(mut) mice) and the LDL receptor (Ldlr(-/-) mice). Mc4r(mut) mice develop obesity due to hyperphagia. Double-mutant mice (Mc4r(mut);Ldlr(-/-)) exhibited massive increases in body weight, plasma cholesterol and triacylglycerol levels and developed atherosclerosis. Atherosclerotic lesion size was affected throughout the aortic root and brachiocephalic artery not only under semisynthetic, cholesterol-containing diet but also under cholesterol-free standard chow. The Mc4r(mut) mice developed a hepatic steatosis which contributes to increased plasma cholesterol levels even under cholesterol-free standard chow. Transcripts of cholesterol biosynthesis components and liver cholesterol levels did not significantly differ between wild-type and all mutant mouse strains but RNA sequencing data and biochemical measurements point to an altered bile acid elimination in Mc4r(mut);Ldlr(-/-). Therefore, the unchanged endogenous cholesterol biosynthesis together with a reduced hepatic VLDL and LDL-cholesterol clearance most likely led to increased plasma lipid levels and consequently to atherosclerosis in this animal model. Our data indicate that dysfunction of the melanocortin-regulated food intake and the resulting obesity significantly add to the proatherogenic lipoprotein profile caused by LDL receptor deficiency and, therefore, can be regarded as relevant risk factor for atherosclerosis

    Dendroarchaeology at Lake Ohrid: 5th and 2nd millennia BCE tree-ring chronologies from the waterlogged site of Ploča Mičov Grad, North Macedonia

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    On the prehistoric site of Ploča Mičov Grad (Ohrid, North Macedonia) on the eastern shore of Lake Ohrid a total of 799 wooden elements were recorded from a systematically excavated area of nearly 100 square meters. Most of them are pile remains of round wood with diameters up to almost 40 cm. A comprehensive dendrochronological analysis allowed the construction of numerous well-replicated chronologies for different species. High agreements between the chronologies prove that oak, pine, juniper, ash and hop-hornbeam can be cross-dated. The chronologies were dated by means of radiocarbon dating and modelling using wiggle matching. An intensive settlement phase is attested for the middle of the 5th millennium BCE. Further phases follow towards the end of the 5th millennium BCE and in the 2nd millennium around 1800, 1400 and 1300 BCE. Furthermore, the exact, relative felling dates allow first insights into the minimum duration of the settlement phases, which lie between 17 and 87 years. The multi-centennial chronologies presented in this study represent a first robust dating basis for future research in the numerous not yet dated prehistoric lake shore settlements in the southwestern Balkans with excellently preserved wooden remains

    Obsolete or Viable? Revision of Lane-Change Manoeuvre Duration Empirical Calculation

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    This study presents a calculation of the time required to execute a lane-change manoeuvre. Compared with other (and older) calculation methods, an analysis was conducted to determine which approach could yield the most reliable results. This study aimed to present a universal calculation method for different road surfaces, surface conditions (dry and wet road surface), and vehicle types (i.e., from small vehicles to SUVs). A total of 108 comparable manoeuvres with modern vehicles were used as a basis for statistical analysis. A new mathematical constant was found based on a regression analysis, adjusting one of the older calculation methods (so-called Kovařík equation), providing the best match between real and calculated manoeuvre duration

    Packed Ultra-wideband Mapping Array (PUMA): A Radio Telescope for Cosmology and Transients

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    PUMA is a proposal for an ultra-wideband, low-resolution and transit interferometric radio telescope operating at 2001100MHz200-1100\,\mathrm{MHz}. Its design is driven by six science goals which span three science themes: the physics of dark energy (measuring the expansion history and growth of the universe up to z=6z=6), the physics of inflation (constraining primordial non-Gaussianity and primordial features) and the transient radio sky (detecting one million fast radio bursts and following up SKA-discovered pulsars). We propose two array configurations composed of hexagonally close-packed 6m dish arrangements with 50% fill factor. The initial 5,000 element 'petite array' is scientifically compelling, and can act as a demonstrator and a stepping stone to the full 32,000 element 'full array'. Viewed as a 21cm intensity mapping telescope, the program has the noise equivalent of a traditional spectroscopic galaxy survey comprised of 0.6 and 2.5 billion galaxies at a comoving wavenumber of k=0.5hMpc1k=0.5\,h\mathrm{Mpc}^{-1} spanning the redshift range z=0.36z = 0.3 - 6 for the petite and full configurations, respectively. At redshifts beyond z=2z=2, the 21cm technique is a uniquely powerful way of mapping the universe, while the low-redshift range will allow for numerous cross-correlations with existing and upcoming surveys. This program is enabled by the development of ultra-wideband radio feeds, cost-effective dish construction methods, commodity radio-frequency electronics driven by the telecommunication industry and the emergence of sufficient computing power to facilitate real-time signal processing that exploits the full potential of massive radio arrays. The project has an estimated construction cost of 55 and 330 million FY19 USD for the petite and full array configurations. Including R&D, design, operations and science analysis, the cost rises to 125 and 600 million FY19 USD, respectively.Comment: 10 pages + references, 3 figures, 3 tables; project white paper submitted to the Astro2020 decadal survey; further details in updated arXiv:1810.0957
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