Increasing the Power Production of Vertical-Axis Wind-Turbine Farms Using Synergistic Clustering

Vertical-axis wind turbines (VAWTs) are being reconsidered as a complementary technology to the more widely used horizontal-axis wind turbines (HAWTs) due to their unique suitability for offshore deployments. In addition, field experiments have confirmed that vertical-axis wind turbines can interact synergistically to enhance the total power production when placed in close proximity. Here, we use an actuator line model in a large-eddy simulation to test novel VAWT farm configurations that exploit these synergistic interactions. We first design clusters with three turbines each that preserve the omni-directionality of vertical-axis wind turbines, and optimize the distance between the clustered turbines. We then configure farms based on clusters, rather than individual turbines. The simulations confirm that vertical-axis wind turbines have a positive influence on each other when packed in well-designed clusters: such configurations increase the power generation of a single turbine by about 10 percent. In addition, the cluster designs allow for closer turbine spacing resulting in about three times the number of turbines for a given land area compared to conventional configurations. Therefore, both the turbine and wind-farm efficiencies are improved, leading to a significant increase in the density of power production per unit land area.     

High‐pressure metamorphic evolution of eclogite and associated metapelite from the Chuacús complex (Guatemala Suture Zone): Constraints from phase equilibria modelling coupled with Lu‐Hf and U‐Pb geochronology

As is common in suture zones, widespread high‐pressure rocks in the Caribbean region reached eclogite facies conditions close to ultrahigh‐pressure metamorphism. Besides eclogite lenses, abundant metapelitic rocks in the Chuacús complex (Guatemala Suture Zone) also preserve evidence for high‐pressure metamorphism. A comprehensive petrological and geochronological study was undertaken to constrain the tectonometamorphic evolution of eclogite and associated metapelite from this area in central Guatemala. The integration of field and petrological data allows the reconstruction of a previously unknown segment of the prograde P–T path and shows that these contrasting rock types share a common high‐pressure evolution. An early stage of high‐pressure/low‐temperature metamorphism at 18–20 kbar and 530–580°C is indicated by garnet core compositions as well as the nature and composition of mineral inclusions in garnet, including kyanite–jadeite–paragonite in an eclogite, and chloritoid–paragonite–rutile in a pelitic schist. Peak high‐pressure conditions are constrained at 23–25 kbar and 620–690°C by combining mineral assemblages, isopleth thermobarometry and Zr‐in‐rutile thermometry. A garnet/whole‐rock Lu‐Hf date of 101.8 ± 3.1 Ma in the kyanite‐bearing eclogite indicates the timing of final garnet growth at eclogite facies conditions, while a Lu‐Hf date of 95.5 ± 2.1 Ma in the pelitic schist reflects the average age of garnet growth spanning from an early eclogite facies evolution to a final amphibolite facies stage. Concordant U‐Pb LA‐ICP‐MS zircon data from the pelitic schist, in contrast, yield a mean age of 74.0 ± 0.5 Ma, which is equivalent to a U‐Pb monazite lower‐intercept age of 73.6 ± 2.0 Ma in the same sample, and comparable within errors with a less precise U‐Pb lower‐intercept age of 80 ± 13 Ma obtained in post‐eclogitic titanite from the kyanite‐bearing eclogite. These U‐Pb metamorphic ages are interpreted as dating an amphibolite facies overprint. Protolith U‐Pb zircon ages of 167.1 ± 4.2 Ma and 424.6 ± 5.0 Ma from two eclogite samples reveal that mafic precursors in the Chuacús complex originated in multiple tectonotemporal settings from the Silurian to Jurassic. The integration of petrological and geochronological data suggests that subduction of the continental margin of the North American plate (Chuacús complex) beneath the Greater Antilles arc occurred during an Albian‐Cenomanian pre‐collisional stage, and that a subsequent Campanian collisional stage is probably responsible of the amphibolite facies overprint and late syncollisional exhumation.     

Quaternary normal faulting in southeastern Sicily (Italy):a seismic source for the 1693 large earthquake

We present geological and morphological data, combined with an analysis of seismic reflection lines across the Ionian offshore zone and information on historical earthquakes, in order to yield new constraints on active faulting in southeastern Sicily. This region, one of the most seismically active of the Mediterranean, is affected by WNW–ESE regional extension producing normal faulting of the southern edge of the Siculo–Calabrian rift zone. Our data describe two systems of Quaternary normal faults, characterized by different ages and related to distinct tectonic processes. The older NW–SE-trending normal fault segments developed up to ≈400  kyr ago and, striking perpendicular to the main front of the Maghrebian thrust belt, bound the small basins occurring along the eastern coast of the Hyblean Plateau. The younger fault system is represented by prominent NNW–SSE-trending normal fault segments and extends along the Ionian offshore zone following the NE–SW-trending Avola and Rosolini–Ispica normal faults. These faults are characterized by vertical slip rates of 0.7–3.3  mm  yr ⁻¹ and might be associated with the large seismic events of January 1693. We suggest that the main shock of the January 1693 earthquakes ( M ~ 7) could be related to a 45  km long normal fault with a right-lateral component of motion. A long-term net slip rate of about 3.7  mm  yr ⁻¹ is calculated, and a recurrence interval of about 550 ± 50  yr is proposed for large events similar to that of January 1693.     

Analysis of the Voyager storm

We analyse the wind and wave conditions present in the Mediterranean Sea at the time and location when the cruise ship Voyager was reportedly hit by one or more big waves and suffered substantial damage. The analysis is done using wind and wave modelling supported by satellite and buoy wind and wave data. Granted the hindcast of the storm, we also analyse the local conditions for the possibility of freak waves.     

The spread of Caulerpa racemosa var. cylindracea in the Mediterranean Sea: an example of how biological invasions can influence beta diversity

The present study aims to evaluate if invasion of Caulerpa racemosa var. cylindracea can affect both alpha and beta diversity in Mediterranean coastal system. The following hypotheses were tested: (i) measures of alpha diversity differ between invaded and non-invaded assemblages (ii) this pattern is consistent between different habitats, (iii) assemblages from habitats which are naturally very different tend to be more similar when invaded compared to non-invaded situations. Results showed that Mediterranean benthic assemblages invaded by C. racemosa var. cylindracea were characterized by lower values of alpha diversity than non-invaded assemblages; moreover, differences between deep (25 m) and shallow water (5m) assemblages appeared lower in invaded than in non-invaded areas, with a decrease of beta diversity. This homogenisation of habitats was related to a lack of several characteristic species and to a higher abundance of few opportunistic species in invaded areas, particularly turf-forming algae. Moreover, variability in taxa composition was lower in invaded than in non-invaded assemblages in both habitats.     

Organic waste impact of capture-based Atlantic bluefin tuna aquaculture at an exposed site in the Mediterranean Sea

A variety of pelagic and benthic parameters were measured at an aquaculture farm used for the fattening of Atlantic bluefin tuna (Thunnus thynnus) which is located at an exposed site (700 m from the coast, average bottom depth of 45 m and average current speed of 6 cm s⁻¹) in the Mediterranean Sea. The objective was to test whether modern off-shore tuna fattening industries can exert a sustainable organic waste impact on the receiving environment as has been reported for the offshore culture of more traditional Mediterranean species such as sparids. In the water column, the concentration of phytopigments, organic matter, heterotrophic bacteria and the taxonomic abundance of mesozooplankton (at the species level) were assessed. In the sediment, we assessed the concentration of reduced sulphur pools, phytopigments, organic matter, heterotrophic bacteria and the taxonomic abundance of meiofauna (at the taxa level) and nematodes (at the genus level). For most parameters, we found no substantial differences between farm and control sites. Deviations of farm values from control values, when they occurred, were small and did not indicate any significant impact on either the pelagic and benthic environment. Deviations were more apparent in the benthic compartment where lower redox potential values, higher bacterial production rates and a change in nematode genus composition pointed out to early changes in the sediment's metabolism. In addition, indigenous potential pathogenic bacteria showed higher concentration at the fish farm stations and were a warning of an undesirable event that may become established following aquaculture practice in oligotrophic environments. The overall data from this study provide extensive experimental evidence to support the sustainability of modern offshore farming technology in minimizing the hypertrophic-dystrophic risks associated with the rapidly-expanding tuna-fattening industry in the Mediterranean Sea.     

Point process-based modeling of multiple debris flow landslides using INLA: an application to the 2009 Messina disaster

We develop a stochastic modeling approach based on spatial point processes of log-Gaussian Cox type for a collection of around 5000 landslide events provoked by a precipitation trigger in Sicily, Italy. Through the embedding into a hierarchical Bayesian estimation framework, we can use the integrated nested Laplace approximation methodology to make inference and obtain the posterior estimates of spatially distributed covariate and random effects. Several mapping units are useful to partition a given study area in landslide prediction studies. These units hierarchically subdivide the geographic space from the highest grid-based resolution to the stronger morphodynamic-oriented slope units. Here we integrate both mapping units into a single hierarchical model, by treating the landslide triggering locations as a random point pattern. This approach diverges fundamentally from the unanimously used presence–absence structure for areal units since we focus on modeling the expected landslide count jointly within the two mapping units. Predicting this landslide intensity provides more detailed and complete information as compared to the classically used susceptibility mapping approach based on relative probabilities. To illustrate the model’s versatility, we compute absolute probability maps of landslide occurrences and check their predictive power over space. While the landslide community typically produces spatial predictive models for landslides only in the sense that covariates are spatially distributed, no actual spatial dependence has been explicitly integrated so far. Our novel approach features a spatial latent effect defined at the slope unit level, allowing us to assess the spatial influence that remains unexplained by the covariates in the model. For rainfall-induced landslides in regions where the raingauge network is not sufficient to capture the spatial distribution of the triggering precipitation event, this latent effect provides valuable imaging support on the unobserved rainfall pattern.     

Experimental assessment of the seismic performance of hospital cabinets using shake table testing

An experimental investigation of hospital building equipment is presented. Dynamic properties and seismic performance of typical ambulatory freestanding cabinets are assessed by unidirectional and bidirectional shake table tests, also considering the presence of internal partitions and cabinet contents. Vulnerability analysis is performed according to the most recent and reliable assessment methods, evaluating the influence of different parameters of the sample cabinets. The performance criteria referred within this research are the limit states reached by the specimens (ie, rocking and overturning) and by their contents (ie, overturning and breaking). Fragility curves are evaluated for the components and the contents, considering both acceleration and velocity intensity measures, and also using dimensionless intensity measures developed in recent studies. The outcomes of the present study confirm the findings of previous laboratory tests and numerical simulations carried out by the same authors and provide a further insight for the reliable seismic performance assessment of hospital cabinets and their contents.     

Modelling rocking response via equivalent viscous damping

The assessment of the out-of-plane response of masonry structures has been largely investigated in literature assuming that walls respond as rigid or semi-rigid bodies, and relevant equations of motion of single-degree-of-freedom and multi-degree of freedom systems have been proposed. Therein, energy dissipation has been usually modelled resorting to the classical hypotheses of impulsive dynamics, delivering a velocity-reduction coefficient of restitution applied at impact. In fewer works, a velocity-proportional damping force has been introduced, by means of a viscous coefficient being constant or variable. A review of such models is presented, a criterion for equivalence of dissipated energy is proposed, equations predicting equivalent viscous damping ratios are derived and compared with experimental responses. Finally, predictive equations are examined in terms of incremental dynamic analyses for large sets of natural ground motions.     

X‐ray computed tomography: Morphological and porosity characterization of giant Antarctic micrometeorites

Giant micrometeorites (MMs; 400–2000 µm) are exceedingly rare and scientifically valuable. Three‐dimensional nondestructive characterization by X‐ray computed tomography (X‐CT) provides information on the petrography and thus petrogenesis of MMs and serves as a guide to maximize subsequent multi‐analytical studies on such precious planetary materials. Here, we discuss the results obtained by X‐CT on 22 giant MMs and the classification based on their 3‐D density contrast images. Scoriaceous and unmelted MMs have distinct porosity ranges (10–40 vol% versus 0–25 vol%, respectively). We observe a porosity variation inside scoriaceous MMs, which allows their atmospheric entry flight history to be resolved. For the first time, spinning entry is explicitly demonstrated for four partially melted MMs. Furthermore, we are able to resolve the thermal gradient in a single particle, based on porosity variation (seen as a progressive increase in pore abundance and size with higher peak temperatures). Moreover, we explore parent body alteration through the 3‐D analysis of pores distribution, showing that shock fabrics are either absent or weakly developed in our data set. Finally, owing to the detection of pseudomorphic chondrules, we estimate that the intensively aqueously altered C1 or CI‐like material could represent 18% of the MM flux at this size fraction (400–1000 µm).