On the photon Green functions in curved space-time

Quantization of electrodynamics in curved space-time in the Lorenz gauge and with arbitrary gauge parameter makes it necessary to study Green functions of non-minimal operators with variable coefficients. Starting from the integral representation of photon Green functions, we link them to the evaluation of integrals involving Gamma functions. Eventually, the full asymptotic expansion of the Feynman photon Green function at small values of the world function, as well as its explicit dependence on the gauge parameter, are obtained without adding by hand a mass term to the Faddeev--Popov Lagrangian. Coincidence limits of second covariant derivatives of the associated Hadamard function are also evaluated, as a first step towards the energy-momentum tensor in the non-minimal case.Comment: 22 pages, plain Tex. All sections and appendices have been improve

A context-aware multiple Blockchain architecture for managing low memory devices

Blockchain technology constitutes a paradigm shift in the way we conceive distributed architectures. A Blockchain system lets us build platforms where data are immutable and tamper-proof, with some constraints on the throughput and the amount of memory required to store the ledger. This paper aims to solve the issue of memory and performance requirements developing a multiple Blockchain architecture that mixes the benefits deriving from a public and a private Blockchain. This kind of approach enables small sensors - with memory and performance constraints - to join the network without worrying about the amount of data to store. The development is proposed following a context-aware approach, to make the architecture scalable and easy to use in different scenarios

Development of guide lines for the calculation of carbon footprint of peaches and apricots produced in Metapontino area (Basilicata): the project IQuaSoPO

The present study is conducted in the framework of the project IQuaSoPO. financed by the regional funds for rural development of Basilicata Region (Italy). It is a three year project which aims to transfer good sustainable practices to local fruit producers. One of the main expected results of the project is to develop guidelines for the calculation of carbon footprint of peaches and apricots, in a life cycle perspective, referred to the productive and geographical specificities of Metapontino area. These guidelines will be used by the local producer to easily assess and communicate the environmental sustainability of their products, which, in this way, will gain added value on the market. Three experimental fields for the production of peaches and apricots in the area of Metaponto are involved in the transfer of knowledge process, about carbon management and water management sustainable practices, which can influence the entity of GHG emissions, by favouring the accumulation of important amounts of carbon and nitrogen in soil and in the perennial parts of peach tree (trunks, branches, roots). Examples of these sustainable management practices are: reduced tillage, soil grass cover, recycling of pruned materials within the field, deficit controlled irrigation, use of compost. In the framework of this study, the three pilot sites are used for inventory data collection, calculation of the carbon footprint, and development of the guidelines. The whole life cycle of the orchards is considered from the tree nursery stage (one or two years), through the establishment, the young, mature and decay stages, and the final destruction, for an average of 15 years. All the agricultural operations have been included in the accounting, in terms of energy consumption and machinery utilization: soil tillage, thinning, pruning, mulching, harvesting, fertilization, plant protection, irrigation, harvesting. Moreover, the life cycle of all the constituent materials of the orchard’s plant and cover structure has been considered (steel wire, cement and aluminum poles, cement blocks, irrigation pipes and water distribution final devices), as well as all the productive inputs’ life cycle (pests and fertilizers). Not just the production phase of the nitrogen fertilizers has been considered, but also the N2O emissions derived from their use. Two different functional units have been used: one kg of peaches/apricot produced and one hectare of cultivated field. The most innovative part of the present study consists in the integration of GHG fluxes occurring within soil-tree-atmosphere system, into the carbon footprint assessment: our aim is to estimate the soil carbon content change, in the considered time boundaries of the study (medium term perspective), related to soil respiration, plant growing, green and brown pruning decomposition, organic compost utilization, cover crop, through sampling activities at field, and using formulas from literature and different models recently emerging in the international scientific community. The guidelines for the carbon footprint calculation along the peach and apricots productive chain in Metapontino region are developed in accordance to the recently published standard ISO 14067; an innovative label for c-footprint communication could be introduced in order to improve the competitiveness of this products on national and international markets

Evolutionary Modeling to Evaluate the Shear Behavior of Circular Reinforced Concrete Columns

Despite their frequent occurrence in practice, only limited studies on the shear behavior of reinforced concrete (RC) circular members are available in the literature. Such studies are based on poor assumptions about the physical model, often resulting in being too conservative, as well as technical codes that essentially propose empirical conversion rules. On this topic in this paper, an evolutionary approach named EPR is used to create a structured polynomial model for predicting the shear strength of circular sections. The adopted technique is an evolutionary data mining methodology that generates a transparent and structured representation of the behavior of a system directly from experimental data. In this study experimental data of 61 RC circular columns, as reported in the technical literature, are used to develop the EPR models. As final result, physically consistent shear strength models for circular columns are obtained, to be used in different design situations. The proposed formulations are compared with models available from building codes and literature expressions, showing that EPR technique is capable of capturing and predicting the shear behavior of RC circular elements with very high accuracy. A parametric study is also carried out to evaluate the physical consistency of the proposed models

Will the Proliferation of 5G Base Stations Increase the Radio-Frequency "Pollution"?

A common concern among the population is that installing new 5G Base Stations (BSs) over a given geographic region may result in an uncontrollable increase of Radio-Frequency "Pollution" (RFP). To face this dispute in a way that can be understood by the layman, we develop a very simple model, which evaluates the RFP at selected distances between the user and the 5G BS locations. We then obtain closed-form expressions to quantify the RFP increase/decrease when comparing a pair of alternative 5G deployments. Results show that a dense 5G deployment is beneficial to the users living in proximity to the 5G BSs, with an abrupt decrease of RFP (up to three orders of magnitude) compared to a sparse deployment. We also analyze scenarios where the user equipment minimum detectable signal threshold is increased, showing that in such cases a (slight) increase of RFP may be experienced.Comment: Cite as: Luca Chiaraviglio, Giuseppe Bianchi, Nicola Blefari-Melazzi, Marco Fiore, Will the Proliferation of 5G Base Stations Increase the Radio-Frequency "Pollution"?, IEEE 91st Vehicular Technology Conference (VTC-Spring), Antwerp, Belgium, May 202

On the Fresh/Hardened Properties of Cement Composites Incorporating Rubber Particles from Recycled Tires

This study investigates the ameliorative effects on some properties of cement-based materials which can be obtained by incorporating rubber particles as part of the fine aggregates. The aim is to find out optimal cement composite/mortar mixtures, containing recycled-tyre rubber particles, suitable for specific engineering applications. Different percentages of rubber particles, from 0% to 75%, were used and, for each percentage, the suitable amount of sand was investigated in order to achieve the best fresh/hardened performances. In particular the following characteristics were examined: density, compressive strength, modulus of elasticity, shrinkage, weight loss, flexural behaviour, thermal conductivity, rapid freezing and thawing durability, and chloride permeability. The experimental results were compared with the ones of cement composite specimens without rubber aggregates. Test results show that the proposed rubberized mortar mixes are particularly suitable for some industrial and architectural applications, such as under-rail bearings, road constructions, paving slabs, false facades, and stone backing

Nonstationary First Threshold Crossing Reliability for Linear System Excited by Modulated Gaussian Process

A widely used approach for the first crossing reliability evaluation of structures subject to nonstationary Gaussian random input is represented by the direct extension to the nonstationary case of the solution based on the qualified envelope, originally proposed for stationary cases. The most convenient way to approach this evaluation relies on working in the time domain, where a common assumption used is to adopt the modulation of stationary envelope process instead of the envelope of modulated stationary one, by utilizing the so-called "preenvelope" process. The described assumption is demonstrated in this work, also showing that such assumption can induce some errors in the envelope mean crossing rate

DAMEWARE - Data Mining & Exploration Web Application Resource

Astronomy is undergoing through a methodological revolution triggered by an unprecedented wealth of complex and accurate data. DAMEWARE (DAta Mining & Exploration Web Application and REsource) is a general purpose, Web-based, Virtual Observatory compliant, distributed data mining framework specialized in massive data sets exploration with machine learning methods. We present the DAMEWARE (DAta Mining & Exploration Web Application REsource) which allows the scientific community to perform data mining and exploratory experiments on massive data sets, by using a simple web browser. DAMEWARE offers several tools which can be seen as working environments where to choose data analysis functionalities such as clustering, classification, regression, feature extraction etc., together with models and algorithms.Comment: User Manual of the DAMEWARE Web Application, 51 page