1,720,978 research outputs found
Non destructive assessment of in situ concrete strength: comparison of approaches through an international benchmark
No full textStrength assessment of concrete in existing structures is a key issue. Many non destructive techniques (NDT) are available which can provide information about the material condition and several approaches can be used to derive strength estimates from NDT test results. However, common practice suffers from many drawbacks: (a) it is difficult to ascertain the level of accuracy/confidence of concrete strength estimates, (b) one lacks established guidelines for estimating the concrete strength variability, (c) the best way to combine NDT methods and coring remains an open issue. The RILEM TC 249 “Non destructive in situ strength assessment of concrete” is addressing these problems. A benchmark was carried out in order to compare (a) how experts define and can carry out an NDT investigation program and (b) how experts derive strength values from the NDT measurements. The benchmark was based on synthetic simulations which reproduced a synthetic data set corresponding to a grid of twenty 3 m-high columns defining a single-storey building structure. The comparison of the various strategies and the analysis of results enabled identification of the most influential parameters that define an investigation approach and influence its efficiency and accuracy. A special emphasis was placed on the magnitude of the measurement error. A model of the investigation strategy is proposed, that will be detailed in future guidelines. The reader is invited to refer to a companion paper (Alwash et al. in Mater Struct, 1. doi:10.1617/s11527-016-0962-x), based on more extensive Monte-Carlo simulations of the same case-study, which analyzes and quantifies the efficiency of the investigation strategies with respect to both average strength and strength variability assessment, in order to draw conclusions based on rational analyses rather than on the element of chance. © 2017, RILEM
Evaluation of concrete strength by means of ultrasonic waves: A method for the selection of coring position
No full textThe evaluation of the concrete properties in a structure has a fundamental importance for safety and structural integrity assessments. An adequate knowledge of the structural concrete performances can be obtained from a large number of cores where performing destructive tests. Non-destructive ultrasonic waves test can be performed before other kind of tests, allowing to improve the assessment of the structural concrete performances and to extend the results to the same kind of elements of the structure, not directly investigated by destructive tests. The aim of this work is to test a new method to identify a good practice to select the position of testing points on which extract the cores starting from an analysis of a preliminary campaign of non-destructive measurements. In this way it is possible to reduce risk of errors of the compressive strength evaluation by a different approach from those used nowadays. The data obtained from an experimental campaign with both non-destructive and destructive tests on 75 concrete columns were considered to validate the new method. The implications of a completely random choice and the guided choice, using the method proposed, were analysed with an iterative and exhaustive approach. European Standard (EN 13791) was followed for in situ measurements and preliminary data analysis. © 2014 Published by Elsevier Ltd
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Dispositivo multisensoriale "Airbox" per la qualità dell'aria. Dalla progettazione alla messa in esercizio
Full text linkScopo di questo documento è la descrizione delle attività che hanno portato alla progettazione e realizzazione di un dispositivo per il rilevamento di inquinanti atmosferici gassosi, polveri sottili, e parametri ambientali, utili a definire il grado di qualità dell’aria in ambienti indoor/outdoor”. Interamente progettato e realizzato all’interno del Laboratorio Test Sensori del Centro Ricerche ENEA di Brindisi, il dispositivo ha come punti di forza la versatilità nel poter essere allestito con sensori di tipologia differente senza alcuna modifica sulla parte hardware del dispositivo, la semplicità di installazione e messa in esercizio, contenuti consumi energetici, alto grado di portatilità, capacità di acquisire autonomamente in locale dati di misura georeferenziati e, al tempo stesso, di trasmetterli in remoto per un pronto utilizzo in tempo reale per il supporto alle decisioni. Il dispositivo è stato replicato in più unità che hanno consentito la messa in campo di una rete di nodi di misura di inquinanti atmosferici, con collocazione su strutture fisse e mezzi mobili, ed ha trovato una pronta e fattiva applicazione in contesto smart cities nell’ambito del Progetto RES-NOVAE a partire da luglio 2015.Aim of this document is to describe the experimental activities and measurements by means of a designed and fabricated multi-parametric sensor-device to monitor air pollution (e.g., gases and particulate matter) including environmental parameters (e.g., temperature, relative humidity, CO2). The sensor-system has been completely designed and implemented in the Sensor Test Lab of the ENEA Research Center in Brindisi. Its main features are: i) capability to be equipped with various types of environmental sensors without any modification of hardware parts, ii) simple installation procedures with standard interface, iii) low power consumption, iv) high portability level, v) capability to get and store locally digital geographic information data and finally vi) to transmit data in real time towards central server. We have fabricated more items of this environmental sensor-system deployed on field to create a sensor network for urban monitoring of air pollutants thanks to Italian National Project RES-NOVAE in smart cities context
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
A case-study of microsensors for landfill air-pollution monitoring applications
No full textThe purpose of this paper is to present a research study on application of low-cost solid-state gas microsensors for odour control and air-pollution monitoring in a landfill. The method introduces microsensors based on commercial devices of n-type metal oxides for cost-effective and real-time monitoring. This research provides a comparative study and assessment of the sensor response for odour detection and potential continuous monitoring of methane (CH4) and Non-Methanic Hydro-Carbons (NMHC) in a landfill. This leads to an insight into low-cost gas sensing capability for practical applications. The environmental measurements have been performed by a sensor-array with multiple sensing elements for high sensitivity and broad selectivity detection. This sensor technology may be useful for the development of a portable, compact, wireless and cost-effective system for gas monitoring applications and industrial process control. The results are discussed as the outcome of an experimental work carried in field at a landfill and demonstrate the efficiency of the low-cost chemo-resistors array for odour sensing and environmental monitoring. Additional long-term investigations need to address some drawbacks on sensors stability and cross-sensitivity. © 2014 Elsevier B.V
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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