The INTERNODES method for the treatment of non-conforming multipatch geometries in Isogeometric Analysis

In this paper we apply the INTERNODES method to solve second order elliptic problems discretized by Isogeometric Analysis methods on non-conforming multiple patches in 2D and 3D geometries. INTERNODES is an interpolation-based method that, on each interface of the configuration, exploits two independent interpolation operators to enforce the continuity of the traces and of the normal derivatives. INTERNODES supports non-conformity on NURBS spaces as well as on geometries. We specify how to set up the interpolation matrices on non-conforming interfaces, how to enforce the continuity of the normal derivatives and we give special attention to implementation aspects. The numerical results show that INTERNODES exhibits optimal convergence rate with respect to the mesh size of the NURBS spaces an that it is robust with respect to jumping coefficients.Comment: Accepted for publication in Computer Methods in Applied Mechanics and Engineerin

The Influence of the Climatic Factors on the Decay of Marbles: an Experimental Study

Stone decay is affected by the influence of climatic factors. In particular marble degradation, that could be expressed by decohesion and /or bowing, is mainly due to the action of temperature and water (rains and relative humidity). In this work non destructive and destructive tests have been performed to evaluate the decay of marble slabs subjected both to natural exposition and to artificial ageing tests (Lab - Bow test). Measurements of Ultrasonic Pulse Velocities (UPV) and bowing have been executed periodically on marble slabs exposed for a period of four years as preliminary field tests. On the base of this work an integrated test methodology to monitoring and previewing the behaviour of façade slabs have been set up. The methodology has been applied on the marble façade of modern building of centre Italy and consists of in situ and laboratory tests. In laboratory a destructive test (flexural strength) has been added to the non destructive tests to evaluate the decay before and after cycles of an ageing test. The results of the analysis, show an evaluative trend of the decay, though it changes its slope after 25 cycles of the ageing test. Moreover this work confirms the effectiveness of the employed non destructive tests and their god correlation with the mechanical tests

Evaluation of errors in quantitative determination of asbestos in rock

The quantitative determination of the content of asbestos in rock matrices is a complex operation which is susceptible to important errors. The principal methodologies for the analysis are Scanning Electron Microscopy (SEM) and Phase Contrast Optical Microscopy (PCOM). Despite the PCOM resolution is inferior to that of SEM, PCOM analysis has several advantages, including more representativity of the analyzed sample, more effective recognition of chrysotile and a lower cost. The DIATI LAA internal methodology for the analysis in PCOM is based on a mild grinding of a rock sample, its subdivision in 5-6 grain size classes smaller than 2 mm and a subsequent microscopic analysis of a portion of each class. The PCOM is based on the optical properties of asbestos and of the liquids with note refractive index in which the particles in analysis are immersed. The error evaluation in the analysis of rock samples, contrary to the analysis of airborne filters, cannot be based on a statistical distribution. In fact for airborne filters a binomial distribution (Poisson), which theoretically defines the variation in the count of fibers resulting from the observation of analysis fields, chosen randomly on the filter, can be applied. The analysis in rock matrices instead cannot lean on any statistical distribution because the most important object of the analysis is the size of the of asbestiform fibers and bundles of fibers observed and the resulting relationship between the weights of the fibrous component compared to the one granular. The error evaluation generally provided by public and private institutions varies between 50 and 150 percent, but there are not, however, specific studies that discuss the origin of the error or that link it to the asbestos content. Our work aims to provide a reliable estimation of the error in relation to the applied methodologies and to the total content of asbestos, especially for the values close to the legal limits. The error assessments must be made through the repetition of the same analysis on the same sample to try to estimate the error on the representativeness of the sample and the error related to the sensitivity of the operator, in order to provide a sufficiently reliable uncertainty of the method. We used about 30 natural rock samples with different asbestos content, performing 3 analysis on each sample to obtain a trend sufficiently representative of the percentage. Furthermore we made on one chosen sample 10 repetition of the analysis to try to define more specifically the error of the methodology

Stone roofing in the Aosta Valley, Italy: Technical properties and durability of traditional Lithotypes

The Aosta Valley Region has promulgated in 1990 a law to partially finance stone roofs to the owners of houses in the historic centers of the valley, provided that the stone material chosen was suitable for this use. This suitability was certified by physical, mechanical and durability tests. More than twenty years ago, roofing slabs were extracted in north-western Alps mainly from schistose rocks. In recent time instead roofing slabs, according to global market, have an international origin. All the traditional stones tested showed excellent technical features according to the local legislation on roof slates. One of these traditional stones is a phyllite whose trade name is “Porfiroide” having the best physical and mechanical properties compared to the other kinds of traditional stones, but with a high standard deviation in the results of flexural strength performed after the freeze and thaw cycles. In the roofing installed 40 years ago, despite their best technical features, the “Porfiroide” roof slabs show a poor state of conservation with widespread detachments, fractures, growth of mosses and lichens, variations in colours. Otherwise, stones with a lower value of flexural strength and higher water absorption instead show good behaviour in the roofing in situ and also in terms of colour change. Evidently the only characterisation of the stone materials is not sufficient but it must be associated to a on-site verification, comparing each slab to be installed with a reference sample, part of the sample submitted to the tests, and to a control on site of the resistance of the stones to degradation

Comminution Effects on Mineral-Grade Distribution: The Case of an MVT Lead-Zinc Ore Deposit

Every mining operation is followed by a beneficiation process aimed at delivering quality materials to the transformation industry. Mainly, in order to separate valuable minerals from gangue in mineral processing, the crushing and grinding of extracted ore are crucial operations for the following separation steps. Comminution is the most energy-consuming operation in mining, and the quality of the results is strictly related to the characteristic of the material under treatment, the type of equipment used in comminution, and the circuit design adopted. A preliminary study was performed in order to understand the crushing behavior under different comminution forces of a high-grade mixed Zn-Pb sulfide ore sample, collected in a Mississippi-Valley Type (MVT) deposit, and the distribution of the target minerals among the products of the process. Ore samples were examined and characterized through thin section observation and SEM analyses for the determination of grain size and texture features, while X-ray powder diffraction (XRPD) quantitative analyses were performed for the definition of target mineral concentrations of comminuted product samples. The selected crushing and grinding circuit comprised lab-scale equipment. For each stage of the process, products below the estimated free-grain size threshold were collected, and particle size analyses were carried out. Comminution products were divided into size distribution classes suitable for further separation operations, and XRPD analyses showed a mineral-grade distribution varying with the dimensions of the products. Characterization of the ore material after crushing and grinding force applications in terms of the distribution of target minerals among different-sized classes was achieved. The important trends highlighted should be considered for further investigation related to an efficient separation

Ornamental Stone Cutting Processing and Sludge Production Evaluation with the Goal of Ending Waste

In the quarry sector, the reduction of landfill material may be obtained not only by finding a suitable recovery of the material as a by-product, but also by identifying the best available cutting technique to be used on the basis of the physical, chemical, and mechanical characteristics of the stones. The choice of the best cutting technique could lead to high efficiency and performance, high quality of the cut surfaces, and a very low environmental impact by reducing energy consumption, decreasing the concentration of heavy metals in the sludge, and producing less waste. In this context, an analysis of the procedures for cutting different types of ornamental stones into slabs together with the evaluation of sludge production for the different cutting methods has been carried out. Two types of analysis were carried out in parallel: evaluation of the stones workability and calculation of the amount of sludge produced in the three different cutting technologies and from the cutting of blocks. A comparison was carried out on the quality of the sludge produced, on type and quantity of metals present, taking into account the different cutting technologies. The performed tests were: chemical analysis, magnetic separation test, and SEM analysis of the metal fraction. The study could provide stone producers with a technological, scientific instrument to identify the best cutting techniques for the processing of their stones, in order to obtain a high-efficiency process, optimize the recovery process, increase the economic advantages, and evaluate the possible reuse of the sludge through a proactive waste management strategy

Ornamental stone cutting processing and sludge production evaluation with the goal of ending waste.

The End-of-waste concept was introduced by the ‘Thematic Strategy on the prevention and recycling of waste’ adopted by the European Commission, in which it proposed to specify the conditions for the cessation of waste status as part of the revision of the Waste Framework Directive (Directive 2008/98/EC). The Directive states that a waste shall lose its status if it is submitted to a recovery operation (including recycling) and comply with specific eligibility criteria. The strategic goal of the End-of-waste is to promote recycling, helping to ensure a high level of environmental protection through the reduction of the consumption of critical raw materials and the quantities of waste destined for disposal. In the mining sector, the reduction of landfill material may be obtained not only by finding a suitable recovery of the material as a by-product, but also identifying the best available cutting technique to be used on the basis of the physical, chemical and mechanical characteristics of the stones. The choice of the best cutting technique could lead to high efficiency and performance, high quality of the cut surfaces and a very low environmental impact by reducing energy consumption, decreasing the concentration of heavy metals in the sludge and producing less waste. In this context, an analysis of the procedures for cutting different types of ornamental stones into slabs together with the evaluation of sludge production for the different cutting methods has been carried out. Three types of analysis were conducted in parallel. The first concerns the characterization of the stones and the choice of the type of cutting machine. The analyses carried out were: petrographic analysis, compression strength, flexural strength, apparent density and water absorption. Also ultrasonic pulse velocity (UPV) and Knoop analyses were performed in order to establish the workability class of the stones, and their classification in accordance with previous research works (EASE R3). The second analysis involves calculating the amount of sludge produced in the three different cutting technologies, taking into account the same block characteristics. The third analysis was conducted on the sludge resulting from the processing of blocks cut into slabs. A comparison was carried out on the quality of the sludge produced, or type and quantity of metals present, taking into account the three different technologies. The tests carried out were: chemical analysis, magnetic separation test and SEM analysis of the metal fraction. The study could provide stone producers with a technological, scientific instrument to identify the best cutting techniques for the processing of their stones, in order to obtain a good efficiency process, optimize the recovery process, increase the economic advantages, and evaluate the possible reuse of the sludge through a proactive waste management strategy

Performance of mesenchymal cell-scaffold constructs in human oral reconstructive surgery: a systematic review

Background: Different sources of cultured cells combined with different scaffolds (allogenic, xenogeneic, alloplastic or composite materials) have been tested extensively in vitro and in preclinical animal studies, but there have been only a few clinical trials involving humans. Aim: This study reviewed all of the English language literature published between January 1990 and December 2015 to assess the histological performance of different mesenchymal cell-scaffold constructs used for bone regeneration in human oral reconstructive procedures. Methods: An electronic search of the MEDLINE and Cochrane Central Register of Controlled Trials databases complemented by manual searching was conducted to identify studies involving histological evaluation of mesenchymal cell-scaffold constructs in human oral surgical procedures. The methodological quality of randomized controlled clinical trials and controlled clinical trials was assessed using the Cochrane Collaboration tool for assessing the risk of bias. Heterogeneity was assessed using Review Manager software. Considering the heterogeneity, the data collected were reported by descriptive methods and a meta-analysis was applied only to the articles that reported the same outcome measures. The articles were classified and described based on the material scaffolds used. Results: The search identified 1030 titles and 287 abstracts. Full-text analysis was performed for 32 articles, revealing 14 studies that fulfilled the inclusion criteria. Three randomized controlled clinical trials were identified as potentially eligible for inclusion in a meta-analysis. The studies were grouped according to the scaffold materials used: bone allograft (three studies), polyglycolic-polylactic scaffold (four studies), collagen sponge (two studies), and bovine bone matrix (five studies). The stem cells used in these studies had been sourced from the iliac crest, periosteum, dental pulp and intraoral sites. Conclusions: The very small amount of available data makes it impossible to draw any firm conclusions regarding the increase in bone formation in human oral reconstructive procedures when using graft materials engineered with autogenous stem cells

Marble Durability Assessment by Means of Total Optical Porosity and Adjacent Grain Analysis

The presence of pores, cracks and microcracks in marble is one of the main features that govern the processes of decay of this stone material and, although marble is characterised by a modest porosity, there is a clear correlation between the presence and movement of fluids, and the phenomena of alteration. Through the study of porosity, it is possible to better understand the phenomena of alteration and degradation in order to obtain useful information, not only in the field of modern building, but also for the protection and recovery of historical and artistic heritage goods. This study was conducted through the characterisation of parameters directly related with the degree of alteration of the materials: water absorption at atmospheric pressure (EN 13755), open porosity (EN 1936), flexural strength (EN 12372) and bowing (EN 16306 par. 8.2). The physical and mechanical measurements have been compared with the Total Optical Porosity method (TOP) and the Adjacent Grain Analysis (AGA) index (a suggested method to evaluate the marbles’ tendency to bow, in EN 16306 annex C); two different methodologies both based on image analysis. The purpose of this study is to demonstrate the effectiveness, for the assessment of marble durability, of the two techniques of microscopic image analysis, the first correlating to the grain shape and the second to the open porosity index. This was done by comparing the microscopic image analysis results with the physical and mechanical properties, both after artificial ageing and after ten years of natural ageing. The results obtained with the TOP method seem to represent the tendency to decay better than the AGA index. The comparison of image analysis of the thin sections, in different portions of the marble specimens, shows the development of degradation due to atmospheric agents, from the surface to the inside, of naturally aged specimens, confirming recent studies made on different marbles