1,720,981 research outputs found
Effects of Thermal Loads on Concrete Cover of FRP Reinforced Elements: Theoretical and Experimental Analysis
No full textThis paper is devoted to the analysis of fiber-reinforced polymer (FRP) reinforced concrete elements under thermal loads. Nonmetallic reinforcing bars present high values of transverse coefficients of the thermal expansion (CTE) with respect to concrete; as a consequence, when temperature increases, tensile stresses take place within the concrete that may produce splitting cracks and, eventually, the concrete cover failure if the confining action is not sufficient. An analytical model is proposed to determine the values of temperature increase (DT) corresponding to the first appearance of the cracking phenomenon and to the concrete cover failure. An experimental investigation carried out on concrete specimens reinforced with FRP reinforcing bars is described, and obtained results are compared with theoretical predictions
Local Search and Constraint Programming: LS and CP illustrated on a transportation problem
No full textReal-world combinatorial optimization problems have two main characteristics which make them difficult: they are usually large, and they are not pure, i.e., they involve a heterogeneous set of side constraints. Hence, in most cases, exact approaches cannot be appliedto solve real-world problems, whereas incomplete algorithms, and among them Local Search and Metaheuristic methods, have proved to obtain very good results in practice. Moreover, real-world applications typically lead to frequent update/addition of constraints, thus the algorithmic approach requires flexibility, and this flexibility can be guaranteed by Constraint Programming. In this chapter we review hybrid algorithms combining Local Search and Constraint Programming Using a didactic transportation problem to illustrate the techniques. © Kluwer Academic Publishers 2004
Elementi curvi in muratura rinforzati con nastri in FRP: analisi dell’aderenza
No full textL’utilizzo di materiali compositi fibrorinforzati (FRP) negli interventi di ripristino, consolidamento e miglioramento sismico di edifici in muratura esistenti rappresenta ormai da alcuni anni una soluzione alternativa alle ben note tecniche tradizionali, soprattutto qualora risulti necessario mantenere l’assetto statico originario adottando soluzioni poco invasive e reversibili.
Nel caso di applicazione di rinforzi esterni in FRP è fondamentale, come noto, l’adesione del materiale di rinforzo con il substrato esistente. Infatti, sulla base delle ricerche condotte negli ultimi anni, si è evidenziato come, in molte applicazioni, la perdita di aderenza sia la tipologia di crisi più frequente e che limita l’efficacia della tecnica di rinforzo medesima.
Numerosi sono gli studi teorici e sperimentali condotti sull’argomento in riferimento alle strutture in calcestruzzo armato e diverse sono le indicazioni derivanti da Codici Normativi e Linee Guida Progettuali a livello internazionale. Risultano, invece, più limitate le ricerche analoghe condotte su substrati in muratura, in considerazione anche della elevata variabilità delle murature esistenti e, di conseguenza, della difficoltà di comparare o estendere i risultati ottenuti in specifiche situazioni. D’altra parte le uniche indicazioni disponibili dal punto di vista progettuale sono quelle riportate nel documento nazionale del CNR.
I parametri che influenzano il legame d’interfaccia muratura-rinforzo sono diversi, le proprietà del substrato e del sistema di rinforzo, la lunghezza di aderenza, la larghezza del rinforzo, le condizioni di carico, la tecnica di messa in opera del rinforzo stesso, e le condizioni di esercizio, quali fattori ambientali, fenomeni a lungo termine, ecc. Un ulteriore parametro da considerare, è la curvatura del substrato, tipica degli elementi strutturali che si ritrovano di frequente nella strutture storiche in muratura (archi, volte).
Per gli elementi curvi rinforzati con nastri in FRP nascono all'interfaccia tensioni tangenziali e normali; quest’ultime favoriscono la crisi prematura dell’aderenza, quando il rinforzo è applicato sulle superfici intradossali, con conseguenti modalità di rottura di tipo fragile.
Nel presente lavoro viene presentato uno studio volto ad indagare il comportamento all’interfaccia di elementi curvi in muratura rinforzati con nastri in carbonio. A tale scopo sono state eseguite prove di tipo beam-test, analizzando l’influenza di diversi raggi di curvatura del substrato e della presenza di connettori di ancoraggio, in grado di assorbire le tensioni normali e quindi di limitare i fenomeni di crisi all’interfaccia
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
Exploiting Relaxations in CP
No full textIn this chapter, we present the integration of various forms of
problem relaxation in Constraint Programming (CP). The main
motivation for the integration proposed concerns the introduction
in CP languages of some form of {em optimality reasoning}. Indeed,
CP languages provide effective and powerful tools for
reducing the search space of the problem by removing infeasible
values. However, they barely consider the problem objective
function and implement a naive form of branch-and-bound which
poorly reduces the search space to be explored.
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Relaxations can be integrated in CP in different ways. Some approaches
propose to automatically translate the whole CP program in linear form,
while some other focus only on global constraints. In this perspective, a
further differentiation can be noted. Some approaches translate all global
constraints in a unique linear store, while others embed an optimization
component within each global constraint. In other approaches, the part of
the problem to be relaxed is decided by the user that explicitly states it
in the program. First, we provide an introduction on different kinds of
relaxation and we discuss many integration approaches, how they exploit
results coming from the relaxation, providing references to related
bibliography. In the second part of the chapter, we consider global
constraints as suitable software components to integrate relaxations in CP.
We discuss, as a case study, a particular global constraint, the path
constraint, and show different relaxations and their tightness
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
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
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