Mathematical Optimization Problems for Particle Finite Element Analysis Applied to 2D Landslide Modeling

Mathematical Geosciences - Notwithstanding its complexity in terms of numerical implementation and limitations in coping with problems involving extreme deformation, the finite element method (FEM)...     

Externalities, knowledge spillovers and the spatial distribution of innovation

The aim of the paper is to investigate the process of spatial agglomeration of innovation and production activities and to assess the extent to which the degree of specialisation or diversity externalities in the area may affect the innovative output in a particular local industry. The analysis is carried out thanks to an original databank on innovation and production activity across 85 industrial sectors and 784 Italian Local Labour Systems, which are groupings of municipalities characterised by a high degree of self-contained flows of commuting workers. According to the global and local indicators of spatial association there are clear signs of spatial correlation in the distribution of innovation activities. The econometric analysis shows that the two types of externalities – specialisation and urbanisation economies – are both effective. Moreover, we find evidence for knowledge spillovers since technological activities of a local industry influence positively innovations of the same sectors in contiguous areas.     

Are fiddler crabs potentially useful ecosystem engineers in mangrove wastewater wetlands?

The effect of different organic-rich sewage concentration (0%, 20% and 60% diluted in seawater) and absence or presence of mangrove trees on the survival, bioturbation activities and burrow morphology of fiddler crabs species was assessed. After 6 months, males of both species always showed higher survival (80%) when compared to females (20%). Crabs inhabiting pristine conditions achieved higher survival (67–87%) than those living in sewage-exposed mesocosms (40–71%). At 60% sewage loading, fiddler crabs processed less sediment (34–46%) during feeding and excavated slightly more sediment (45–80%) than at pristine conditions. While percent volume of the burrow chambers increased (13–66%) at contaminated mesocosms for both vegetation conditions, burrows were shallower (33%) in bare cells loaded with sewage. The results show that fiddler crabs presented moderate mortality levels in these artificial mangrove wetlands, but mainly in sewage impacted cells. However, they still function as ecosystem engineers through bioturbation activities and burrow construction.     

Quasi‐static and pseudo‐dynamic testing of unbonded post‐tensioned rocking bridge piers with external replaceable dissipaters

It has been well documented that following a major earthquake a substantial percentage of economic loss results from downtime of essential lifelines in and out of major urban centres. This has thus led to an improvement of both performance‐based seismic design philosophies and to the development of cost‐effective seismic structural systems capable of guaranteeing a high level of protection, low structural damage and reduced downtime after a design‐level seismic event. An example of such technology is the development of unbonded post‐tensioned techniques in combination with rocking–dissipating connections. In this contribution, further advances in the development of high‐performance seismic‐resistant bridge piers are achieved through the experimental validation of unbonded post‐tensioned bridge piers with external, fully replaceable, mild steel hysteretic dissipaters. The experimental response of three 1 : 3 scale unbonded, post‐tensioned cantilever bridge piers, subjected to quasi‐static and pseudo‐dynamic loading protocols, are presented and compared with an equivalently reinforced monolithic benchmark. Minimal physical damage is observed for the post‐tensioned systems, which exhibit very stable energy dissipation and re‐centring properties. Furthermore, the external dissipaters can be easily replaced if severely damaged under a major (higher than expected) earthquake event. Thus, negligible residual deformations, limited repair costs and downtime can be achieved for critical lifeline components. Satisfactory analytical–experimental comparisons are also presented as a further confirmation of the reliability of the design procedure and of the modelling techniques. Copyright © 2008 John Wiley & Sons, Ltd.     

Improvement of HVSR technique by wavelet analysis

In this work we investigate the application of the wavelet analysis to improve the well-known horizontal to vertical spectral ratio (HVSR) technique for site effect estimation. Wavelet analysis has been widely used in the last decade for its capacity to localise the signal in both the time and frequency domains. The wavelet packet transform and the evaluation of a cost function for every node permit one to remove from the signal the least important components and lead to significant improvements in the identification of the fundamental frequency. In this paper a new algorithm is presented based on wavelet analysis, that allows, in some cases, to improve the identification of the peak in the QTS ratio. A number of examples of application are also presented.     

Lethal and estrogenic effects of 4-nonylphenol in the cockle Cerastoderma glaucum

The lethal and sublethal effects of the xenoestrogen 4-nonylphenol (NP) were evaluated in the cockle Cerastoderma glaucum. In a 96-h lethality test, bivalves were exposed to 0, 0+ acetone, 0.19, 0.38, 0.75, 1.5 and 3.0 mg NP/l. The 96-h LC₅₀ value was 0.3 mg NP/l. No mortality was observed at 0.1 mg NP/l. The potential estrogenicity of NP was studied in both sexually undifferentiated (resting phase) and differentiated (pre-spawning phase) cockles, exposed for 7 and 14 days to 0, 0+ acetone, 0.0125, 0.025, 0.05, and 0.1 mg NP/l. Vitellogenin (Vg)-like protein levels were determined in both haemolymph and digestive gland by the alkali-labile phosphate (ALP) assay. In the resting phase, exposure for 7 days to 0.1 mg NP/l resulted in significant increases in ALP in both haemolymph and digestive gland, compared with controls. A significant increase was also observed in digestive gland of animals exposed to 0.0125 mg NP/l-exposed animals. After 14 days of exposure, haemolymph ALP levels were significantly increased in exposed animals at all NP concentrations tested, whereas no difference was recorded in digestive gland. In the pre-spawning phase, exposure for 7 days to NP significantly increased ALP levels in haemolymph from males exposed at all NP concentrations tested, whereas no significant variations were found in haemolymph from females. NP (0.05 and 0.1 mg/l) was also shown to increase ALP concentrations significantly in digestive gland of males, but not in those of females. Likewise, after 14 days’ exposure, ALP levels significantly increased in haemolymph from males only at 0.1 mg NP/l. Conversely, NP caused significant increases in ALP levels in digestive gland from both males (at all NP concentrations tested) and females (at 0.025 and 0.1 mg NP/l). These results demonstrate that NP induces Vg synthesis in C. glaucum. Interestingly, males were more responsive to NP than females.     

Stromboli Island (Italy): Scenarios of Tsunamis Generated by Submarine Landslides

Stromboli is an Italian volcanic island known for its persistent state of activity, which leads to frequent mass failures and consequently to frequent tsunamis ranging from large (and rare) catastrophic events involving the entire southern Tyrrhenian Sea to smaller events with, however, extremely strong local impact. Most of tsunamigenic landslides occur in the Sciara del Fuoco (SdF) zone, which is a deep scar in the NW flank of the volcano, that was produced by a Holocene massive flank collapse and that is the accumulation area of all the eruptive ejecta from the craters. Shallow-water bathymetric surveys around the island help one to identify submarine canyons and detachment scars giving evidence of mass instabilities and failures that may have produced and might produce tsunamis. The main purpose of this paper is to call attention to tsunami sources in Stromboli that are located outside the SdF area. Further, we do not touch on tsunami scenarios associated with gigantic sector collapses that have repeat times in the order of several thousands of years, but rather concentrate on intermediate size tsunamis, such as the ones that occurred in December 2002. Though we cannot omit tsunamis from the zone of the SdF, the main emphasis is on the elaboration of preliminary scenarios for three more possible source areas around Stromboli, namely Punta Lena Sud, Forgia Vecchia and Strombolicchio, with the aim of purposeful contributing to the evaluation of the hazard associated with such events and to increase the knowledge of potential threats affecting Stromboli and the nearby islands of the Aeolian archipelago. The simulations show that tsunami sources outside of the SdF can produce disastrous effects. As a consequence, we recommend that the monitoring system that is presently operating in Stromboli and that is focussed on the SdF source area be extended in order to cover even the other sources. Moreover, a synoptic analysis of the results from all the considered tsunami scenarios leads to a very interesting relation between the tsunami total energy and the landslide potential energy, that could be used as a very effective tool to evaluate the expected tsunami size from estimates of the landslide size.     

Combining Seismic Noise Techniques for Landslide Characterization

A strong topographic relief and the presence of weakly consolidated sediments create favorable conditions for the development of landslides around the eastern rim of the Fergana Basin (Central Asia). In summer 2012, a field experiment employing small aperture seismic arrays was carried out on an unstable slope, using ambient vibration recordings. The aim of the study was to constrain the seismic response of a potential future landslide and to map lateral and vertical changes in the shear-wave velocity of the surficial soil layers. Strong variations of horizontal-to-vertical spectral ratios in terms of amplitude and directionality indicated clear differences in local site effects, probably reflecting the stability of different sections of the slope. Results further showed resonant frequencies of both the entire unstable block, as well as for smaller, individual parts. The use of an ad hoc, passive seismic tomography approach based on noise correlograms allowed for the mapping of the shear-wave velocities of the sliding material, even in cases of significant topography relief. Based on the recording of seismic noise only, we clearly identified a low-velocity body of weakly consolidated claystone and limestone material, which can be interpreted as the landslide body, with laterally varying thickness.     

River,Coastal and Estuarine Morphodynamics Selected papers from the 10th anniversary of the RCEM Symposium

This Special Issue collects 17 selected contributions from participants to the 10th edition of the RCEM (River, Coastal and Estuarine Morphodynamics) Symposium, organized in Padova-Trento (Italy) in September 2017. The series of biennial RCEM symposia has the key goal of enhancing interaction and promoting integration among the scientific communities focused on the morphological dynamics of river, coastal and estuarine environments, through various combinations of theoretical, observational, experimental and modelling approaches. The 17 contributions to this Special Issue contain four state-of-science reviews and overall offer a broad view of the cross-cutting perspective adopted when addressing morphodynamics. Such a perspective accounts for the mutual interplay between morphology, fluid dynamics and other environmental factors, and has presently become a widespread paradigm to address landscape evolution. © 2020 John Wiley & Sons, Ltd.