Mesh sensitivity in discrete element simulation of flexible protection structures

The Discrete Element Method (DEM) has been employed in recent years to simulate flexible protection structures undergoing dynamic loading due to its inherent aptitude for dealing with inertial effects and large deformations. The individual structural elements are discretized with an arbitrary number of discrete elements, connected by spring-like remote interactions. In this work, we implement this approach using the parallel bond contact model and compare the numerical results at different discretization intervals with the analytical solutions of classical beam theory. Successively, we use the same model to simulate the punching test of a steel wire mesh and quantify the influence of a different number of elements on the macroscopic response

Micro-Drilling of ZTA and ATZ Ceramic Composit: Effect of Cutting Parameters on Surface Roughness

Ceramics are a class of materials widely used during last fifteen years for orthopaedic applications. It is well known that they are characterized by low wear rate, and friction coefficient. However, these materials are very difficult to machine into complex shapes because of their brittleness and high hardness. The most effective method to increase the crack resistance is the formation of a composite structure. This class of materials, composed by two or more different ceramics, can present higher characteristic respect to the single component, like fracture toughness and flexural strength. This paper presents a study of the influence of cutting parameters (cutting speed, feed rate and step number) onto the hole surface roughness and deformation due to the drill operation. The ceramic composite materials AZT (alumina toughened zirconia) and ZTA (zirconia toughened alumina) were first characterized in terms of hardness and roughness. After the drilling test, the holes were analyzed using scanning electron microscope (SEM) and an advanced 3-dimensional non-contact optical profilomete

Geopan at@s: A brokering based gateway to georeferenced historical maps for risk analysis

Importance of ancient and historical maps is nowadays recognized in many applications (e.g., urban planning, landscape valorisation and preservation, land changes identification, etc.). In the last years a great effort has been done by different institutions, such as Geographical Institutes, Public Administrations, and collaborative communities, for digitizing and publishing online collections of historical maps. In spite of this variety and availability of data, information overload makes difficult their discovery and management: Without knowing the specific repository where the data are stored, it is difficult to find the information required. In addition, problems of interconnection between different data sources and their restricted interoperability may arise. This paper describe a new brokering based gateway developed to assure interoperability between data, in particular georeferenced historical maps and geographic data, gathered from different data providers, with various features and referring to different historical periods. The developed approach is exemplified by a new application named GeoPAN Atl@s that is aimed at linking in Northern Italy area land changes with risk analysis (local seismicity amplification and flooding risk) by using multi-Temporal data sources and historic maps

20 years of cryogenic particle detectors: past, present and future

In 1984 different authors presented a new approach for detecting elementary particles: the cryogenic (sometimes also called bolometric) particle detector. The basic idea was very simple but at the same time completely different with respect to other classical methods. The generation of the signal is produced by phonons with a mean energy around 10 −4 − 10 −5 eV and this aspect changes completely the evaluation of the theoretical energy resolution. In these 20 years substantial progress has been made in the development of cryogenic particle detectors, many experiments have been realized and some are still running. Detector performances are greatly improved and very massive detectors have been constructed. For specific experiments, detectors with simultaneous measurements of heat and ionization (or scintillation) were also developed. Cryogenic particle detectors have been applied in many fields, not only in particle physics experiments, thanks to some peculiar characteristics that they exhibit. Experiments on double beta decay take advantage from the good energy resolution and the flexibility in selecting materials; low energy thresholds and high efficiencies to nuclear recoils of these detectors are very interesting in the search for dark matter; the impressively high energy resolution of microcalorimeters is suitable for X-ray spectroscopy and direct neutrino mass measurements. Other experiments in particle physics use the cryogenic approach, but it is important to note that applications to surface analysis with Total Reflection X-ray Fluorescence (TXRF) for industry and measurements of protein fragments for biology have been also proposed. In the near future, new experiments will be realized using this technique. Very important technical challenges are still open, such as: realization of very large detectors (at the one ton scale), improvements in energy resolution and energy thresholds, maximization of the time resolution. A short history and the state of the art of cryogenic particle detectors will be presented; some aspects of their applications in the past and for the future will be briefly discussed