Regional ground‐motion prediction equations for amplitude‐, frequency response‐, and duration‐based parameters for Greece

Although all of the main properties of a ground motion cannot be captured through a single parameter, a number of different engineering parameters has been proposed that are able to reflect either one or more ground‐motion characteristics concurrently. For many of these parameters, especially regarding Greece, there are relatively few or no predictive models. In this context, we present a set of new regionally‐calibrated equations for the prediction of the geometric mean of the horizontal components of 10 amplitude‐, frequency response‐, and duration‐based parameters for shallow crustal earthquakes. These equations supersede previous empirical relationships for Greece since their applicability range for magnitude, and epicentral distance has been extended down to M_w 4 and up to 200 km, respectively, the incorporation of a term accounting for anelastic attenuation has been investigated, while their development was based on a ground‐motion dataset spanning from 1973 to 2014. For all ground‐motion parameters, we provide alternative optimal equations relative to the availability of information on the different explanatory variables. In all velocity‐based and contrary to the acceleration‐based parameters, the anelastic attenuation coefficient was found statistically insignificant when it was combined with the geometric decay and the coefficient accounting for saturation with distance. In the regressions where the geometric decay coefficient simultaneously incorporated the contribution of anelastic attenuation, its increase was found to be much less considerable in the velocity‐based than in the acceleration‐based parameters, implying a stronger effect of anelastic attenuation on the parameters that are defined via the acceleration time history.     

Spacecraft trajectories to the L<Subscript>3</Subscript> point of the Sun–Earth three-body problem

Of the three collinear libration points of the Sun–Earth Circular Restricted Three-Body Problem (CR3BP), L₃ is that located opposite to the Earth with respect to the Sun and approximately at the same heliocentric distance. Whereas several space missions have been launched to the other two collinear equilibrium points, i.e., L₁ and L₂, taking advantage of their dynamical and geometrical characteristics, the region around L₃ is so far unexploited. This is essentially due to the severe communication limitations caused by the distant and permanent opposition to the Earth, and by the gravitational perturbations mainly induced by Jupiter and the close passages of Venus, whose effects are more important than those due to the Earth. However, the adoption of a suitable periodic orbit around L₃ to ensure the necessary communication links with the Earth, or the connection with one or more relay satellites located at L₄ or L₅, and the simultaneous design of an appropriate station keeping-strategy, would make it possible to perform valuable fundamental physics and astrophysics investigations from this location. Such an opportunity leads to the need of studying the ways to transfer a spacecraft (s/c) from the Earth’s vicinity to L₃. In this contribution, we investigate several trajectory design methods to accomplish such a transfer, i.e., various types of two-burn impulsive trajectories in a Sun-s/c two-body model, a patched conics strategy exploiting the gravity assist of the nearby planets, an approach based on traveling on invariant manifolds of periodic orbits in the Sun–Earth CR3BP, and finally a low-thrust transfer. We examine advantages and drawbacks, and we estimate the propellant budget and time of flight requirements of each.     

Theoretical Study on the TBM Tool-Rock Interaction

Despite several decades of academic rock mechanics and practical rock engineering there is still a lack of some fundamental knowledge on rock-tool interaction. A model is considered in this paper that takes the constitutive law of the rock, the presence of the tunnel head, the discontinuities and the amount of the natural stress due to the high overburden in the presence of the forces caused by the TBM disk on the tunnel head, into account in the failure mode.     

The influence of temperature and seawater composition on calcite crystal growth mechanisms and kinetics: Implications for Mg incorporation in calcite lattice

The composition of carbonate minerals formed in past and present oceans is assumed to be significantly controlled by temperature and seawater composition. To determine if and how temperature is kinetically responsible for the amount of Mg incorporated in calcite, we quantified the influence of temperature and specific dissolved components on the complex mechanism of calcite precipitation in seawater. A kinetic study was carried out in artificial seawater and NaCl-CaCl₂ solutions, each having a total ionic strength of 0.7 M. The constant addition technique was used to maintain [Ca²⁺] at 10.5 mmol kg⁻¹ while [] was varied to isolate the role of this variable on the precipitation rate of calcite.Our results show that the overall reaction of calcite precipitation in both seawater and NaCl-CaCl₂ solutions is dominated by the following reaction:

     

The people’s food: the ingredients of “ethnic” hierarchies and the development of Chinese restaurants in Rome

In the last 20 years, the growth of Chinese immigration in Italy has increased, being characterized by multiple migration strategies linked to transnational economic activities. This has been particularly the case with the Chinese immigrant community in Rome, where many of these immigrants are involved in the restaurant or import–export business. In this context, the Chinese immigrant presence in the restaurant sector will be analysed in detail within a multimethod approach developed to explore the number, location and characteristics of all Chinese restaurants that were opened and closed since the 1970s. This exercise in economic geography is linked to other questions such as power and cultural relations, urban planning practices and the discourses of racism. The development and the geography of the Chinese restaurants allow us to understand not only how far or close they are to the mainstream Italian restaurant sector, but also the spatial trajectories of Roman Chinese in general within the urban landscape. As Chinese restaurants outside China have become a symbol of transnational Chinese identity, it is worth considering the real spatial practices attached to the construction and negotiation of this transnationality.     

Statistical analysis of some main geomechanical formulations evaluated with the Kaniadakis exponential law

The following paper reviews four well-known geomechanical equations, i.e. the elastic modulus of the rock mass as function of the Rock Mass Rating (RMR) system, the relation between Rock Quality Designation (RQD) and spacing distribution of the natural discontinuities in the rock mass, the distribution of the discontinuity spacing along a straight line for a rock mass and the intact rock strength in function of the specimen diameter by using a power-law flat tails equation based on the theory of Kaniadakis. The results show that by using novel formulations, the experimental data are better approximated by the power-law flat tails statistical approach, which shows a trend similar to ordinary exponential for a certain part of the interval of variability of x; the tails, however, follow the power law for extreme values of x. It was, therefore, possible to obtain new formulations able to better represent some fundamental aspects of geomechanics.     

The response of drainage basins to the late Quaternary tectonics in the Sicilian side of the Messina Strait (NE Sicily)

Despite more than 40 yr of research attributing temporal changes in streambank erosion rates to subaerial processes, little quantitative information is available on the relationships between streambank erodibility (k_d) and critical shear stress (τ_c) and the environmental conditions and processes that enhance streambank erosion potential. The study goal was to evaluate temporal changes in k_d and τ_c from soil desiccation and freeze–thaw cycling. Soil erodibility and τ_c were measured monthly in situ using a multiangle, submerged jet test device. Soil moisture, temperature, and bulk density as well as precipitation, air temperature, and stream stage were measured continuously to determine changes in soil moisture content and state. Pairwise Mann–Whitney tests indicted k_d was 2.9 and 2.1 times higher (p < 0.0065) during the winter (December–March) than in the spring/fall (April–May, October–November) and the summer (June–September), respectively. Regression analysis showed 80% of the variability in k_d was explained by freeze–thaw cycling alone. Study results also indicated soil bulk density was highly influenced by winter weather conditions (r² = 0.86): bulk density was inversely related to both soil water content and freeze–thaw cycling. Results showed that significant changes in the resistance of streambank soils to fluvial erosion can be attributed to subaerial processes. Water resource professionals should consider the implications of increased soil erodibility during the winter in the development of channel erosion models and stream restoration designs.     

Relation water content ratio-to-liquidity index versus the Atterberg limits ratio evaluated with the Kaniadakis exponential law

Water content ratio (WCR) is defined as the ratio water content to liquid limit (LL) and it is proved to be a good replacer of the well-known parameter liquidity index (LI) to predict shear strength of fine-grained soils. An interesting correlation between the slope of LI and WCR and LL/PL ratio was observed. However, this trend is poorly described by conventional regression functions. By employing the Kaniadakis exponential law based on the relativistic mechanics, 22 data set, considering the LL/PL vs the slope of LI and WCR, were very-well matched.     

Analyses of the Distribution and Nature of the Natural Cementation of Quaternary Sediments: The Case of the Turin Subsoil (Italy)

The finding of a remarkable number of stratigraphies from mechanical surveys and water research wells, drilled in the urban area of Turin over the last few decades, has made it possible to reconstruct the geology of the subsoil in great detail. In particular, it has been possible to define the distribution of the cementation in the Quaternary alluvial sediments through geological planimetries that refer to different depths from the ground level. The cementation map of the Turin subsoil can be considered very useful for the planning of future underground works and for the definition of the necessary construction methods. An accurate mineralogical analysis has identified a “meniscus” type structure of the cementation; this leads us to believe that the cementation has formed in a vadose environment. The reason for the precipitation of the calcium carbonates is therefore probably due to infiltration of the slightly acidic meteoric water into the subsoil and not to the mixing of water with different temperatures, hardness and pH values, as some authors believed in the past.     

A Combined Analytical and Numerical Approach for the Evaluation of Radial Loads on the Lining of Vertical Shafts

The evaluation of the load acting on a shaft support is of fundamental importance for the correct dimensioning of the structure. The load acting on the support can appear somewhat complex. One approach to define the load on the lining may be to use the convergence-confinement method (CCM) normally used in the tunneling design. This process involves intersecting the convergence-confinement (CC) curve with the support reaction line. However, in order to be able to adopt this technique, it is necessary to know the radial displacement of the shaft wall at the point in which the support is to be installed. Using the equations of Vlachopoulos and Diederichs (Rock Mech Rock Eng 42:131–146, 2009) the reaction line of the support can be calculated. Numerical models developed with Flac 2D v.6.0 considering the Mohr–Coulomb criterion and an ideal elasto-plastic behavior simulating stepwise excavation and support installation were developed. The relation between applied internal stress and radial displacement of the wall shaft, obtained by the numerical simulation was compared with the CC curve obtained by the CCM and it showed a good match between the two methods. However, an iterative procedure has also been used to insert the reaction line in the CC graph. The result shows lower initial displacements (and therefore greater radial stress) when compared with the values obtained by numerical calculation with the axisymmetric model. It is therefore recommended the combined use of the CCM (analytical method) and the axisymmetric numerical model (step by step simulation) to obtain the values of the final load on the lining and the final plastic radius, necessary for the correct design of supporting structures on the shaft wall.