Not invasive analyses on a tin-bronze dagger from Jericho. A case study

Tin-bronze makes its appearance in Southern Levant during the Early Bronze IV, the post-urban phase of the last centuries of the 3rdmillennium BC, when arsenical copper was still the most widespread copper alloy. Only from the following Middle Bronze Age tin-bronze will be the utmost spread alloy. The adoption of tin as alloying metal purports new technological skills, and a changed trade supply system, through new routes, thanks to itinerant coppersmiths. The examination of dagger TS.14.143 found in an EB IV (2300-2000 BC) tomb at Jericho by mean of trace elements and Energy Dispersive X-ray Diffraction analyses, provided info about its metal composition and technology. The detection of tin, testified only by a few specimens at the site so far, allows some reflections about the beginning of diffusion tin-bronze, and the presence of a small-scale melting activity in the post-urban phase in the key-site of Jericho

Enhanced tunneling conductivity induced by gelation of attractive colloids

We show that the formation of a gel by conducting colloidal particles leads to a dramatic enhancement in bulk conductivity, due to inter-particle electron tunneling, combining predictions from molecular dynamics simulations with structural measurements in an experimental colloid system. Our results show how colloidal gelation can be used as a general route to huge enhancements of conductivity, and suggest a feasible way for developing cheap materials with novel properties and low metal content.Comment: 8 pages, 8 figures, 2 table

Large-Amplitude Velocity Fluctuations in Coronal Loops: Flare Drivers?

Recent space observations of coronal lines broadening during a flare occurrence suggest that unresolved nonthermal velocity rises well above the background level before the start of the flare, defined as the start of hard X-ray emission. Using a new shell model to describe the Alfvenic turbulence inside a coronal loop, it is shown that the occurrence of high values (of the order of 100 km s-1) of the large-scale fluctuating velocity can represent an efficient trigger to a nonlinear intermittent turbulent cascade and then to the generation of a burst of dissipated energy. The numerical results of the model furnish a well-supported physical explanation for the reason why large velocity fluctuations represent the flare trigger rather than the result of the later energy deposition

A Practice-Oriented Procedure for Seismic Reliability Assessment of RC Structures Affected by Carbonation-Induced Degradation

Existing reinforced concrete (RC) buildings in Europe have generally been designed without proper consideration of seismic actions and capacity design principles, and thus they tend to be vulnerable to earthquakes. Moreover, since a significant proportion of the aforementioned buildings were developed during the 1950s and 1960s, they are currently close to the end of their service life. Therefore, seismic assessment of existing RC building is a major issue in structural engineering and construction management, and the related seismic analyses should take into account the effect of material ageing and degradation. This paper proposes a practice-oriented procedure for quantifying seismic reliability, taking into account the main effects of carbonation-induced degradation phenomena. It summarizes the main aspects of the most up-to-date models for the seismic degradation of concrete and RC members and shows how nonlinear static (pushover) analyses can be utilized (in lieu of the most time-consuming non-linear time history analyses) in quantifying seismic reliability with respect to the performance levels of relevance in seismic engineering. A relevant case study is finally considered with the aim to showing how some parameters, such as exposure class and cover thickness, affect the resulting seismic reliability of existing RC buildings

Preliminary design, modeling and control of a fully actuated quadrotor UAV

In this paper a preliminary study on a new concept of fully actuated Unmanned Aerial Vehicle (UAV), named ODQuad (OmniDirectional Quadrotor), is presented. By exploiting two additional actuators, the designed UAV can simultaneously modify the tilting angle of all the propellers, in such a way to decouple position and attitude motions. This solution, differently from other fully actuated UAVs with tilted propellers, avoids internal forces and energy dissipation, due to non-parallel propellers’ axes. A preliminary mechanical design and the kinematic and dynamic models are developed. Moreover, a motion control scheme, based on a hierarchical two loop, has been designed. Simulations are provided in order to show the feasibility of the concept and the effectiveness of the control scheme

Deterministic entangling gates with nonlinear quantum photonic interferometers

The quantum computing paradigm in photonics currently relies on the multi-port interference in linear optical devices, which is intrinsically based on probabilistic measurements outcome and thus non-deterministic. Devising a fully deterministic, universal, and practically achievable quantum computing platform based on integrated photonic circuits is still an open challenge. Here we propose to exploit weakly nonlinear photonic devices to implement deterministic entangling quantum gates, following the definition of dual rail photonic qubits. It is shown that a universal set of single- and two-qubit gates can be designed by a suitable concatenation of few optical interferometric elements, with optimal fidelities arbitrarily close to 100% theoretically demonstrated through a bound constrained optimization algorithm. The actual realization would require the concatenation of a few tens of elementary operations, as well as on-chip optical nonlinearities that are compatible with some of the existing quantum photonic platforms, as it is finally discussed

Void Fraction Near Surfaces Immersed in Fluidized Beds by Heat Transfer Measurements

A semi-empirical model is used to calculate the averaged surface void fraction in fluidized beds, εw, starting from experimental data on surface-to-bed heat transfer coefficient. The model is able to describe the effect of the main process parameters and shows that εw increases with minimum fluidization void fraction and particle Archimedes number

A Sardinian early 1st millennium BC bronze axe from Motya

An Iron Age bronze axe was found in Motya (Sicily, Italy) in a prehistoric layer dating from the 10th century BC underneath the 4th century BC patrician residency known as “Casa dei mosaici”. The axe belongs to the double-looped socketed type well known in central Mediterranean in the time span 1200-900 BC, and it is comparable with some coeval Sardinian specimens. The bronze has been characterised using the backscattering electron signal of a SEM (Scanning Electron Microscope) and EDX (Energy Dispersive X-ray Spectroscopy). The resulting composition of the metal alloy is Cu-Sn-As with an addition of Pb in some specific spots

Electro-optically induced absorption in α-Si:H/α-SiCN waveguiding multistacks

Electro optical absorption in hydrogenated amorphous silicon (α-Si:H) - amorphous silicon carbonitride (α-SiCxNγ) multilayers have been studied in two different planar multistacks waveguides. The waveguides were realized by plasma enhanced chemical vapour deposition (PECVD), a technology compatible with the standard microelectronic processes. Light absorption is induced at λ = 1.55 μm through the application of an electric field which induces free carrier accumulation across the multiple insulator/ semiconductor device structure. The experimental performances have been compared to those obtained through calculations using combined two-dimensional (2-D) optical and electrical simulations. © 2008 Optical Society of America

A Comparison between High-order Temporal Integration Methods Applied to the Discontinuous Galerkin Discretized Euler Equations

Abstract In this work we present a high-order Discontinuous Galerkin (DG) space approximation coupled with two high-order temporal integration methods for the numerical solution of time-dependent compressible flows. The time integration methods analyzed are the explicit Strong-Stability-Preserving Runge-Kutta (SSPRK) and the Two Implicit Advanced Step-point (TIAS) schemes. Their accuracy and efficiency are evaluated by means of an inviscid test case for which an exact solution is available. The study is carried out for several time-steps using different polynomial order approximations and several levels of grid refinement. The effect of mesh irregularities on the accuracy is also investigated by considering randomly perturbed meshes. The analysis of the results has the twofold objective of (i) assessing the performances of the temporal schemes in the context of the high-order DG discretization and(ii) determining if high-order implicit schemes can displace widely used high-order explicit schemes