117,281 research outputs found
La moderna Anestesia Generale:cenni storici e descrizione delle tecniche di applicazione più corrente
No full textAll'inizio sono brevemente elencati i primi passi della moderna anestesia in Italia e si parla poi del dualismo tra scuola Anglo -Americana e scuola Europea per le diverse tendenze nella scelta dei farmaci anestetici.Vengono poi esposte in maniera sintetica, le metodiche usate in epoca attuale
Efficiency of Piles Stabilizing Slopes in Fine-Grained Soils
No full textEqually spaced piles can be designed to ensure the stability of a slope with a desired safety factor or to restrain slow slope movements to prevent damage to existing structures. The piles are usually arranged in lines installed transversally to soil movements or in groups of limited extension in a plan according to their stabilizing or protective function. A numerical study has been performed to analyze the role of some design parameters in the efficiency of equally spaced piles, adopting two-dimensional (2D) and three-dimensional (3D) finite-difference (FD) models. Plane strain models have been used to study the soil arching mechanism and the associated stress transfer from the yielding soil to the stabilizing piles, while 3D numerical analyses have been performed to evaluate the efficiency of pile groups. The effect of varying pile spacing, pile embedded length, soil mechanical properties, and sloping ground conditions have been investigated for two-layer slopes assuming fixed or unconstrained piles. The outcomes of the parametric study made it possible to derive a simple analytical relationship to quantify the resisting contribution provided by the piles in an infinite slope. The paper shows that the proposed approach, even though limited to the ranges of the adopted parameters, can be used for a preliminary design of stabilizing piles to ensure the desired increase in the slope safety factor, as well as to achieve the desired reduction of downhill slope movements
La mitigazione degli effetti indotti dallo scavo di gallerie mediante l’uso di barriere preinstallate: il caso della linea C della metropolitana di Roma
No full textLa rete di trasporti pubblici della città di Roma è attualmente in via di potenziamento con la
costruzione della terza linea della metropolitana, la linea C. Questa sottopassa il centro storico della città con
significative interferenze con monumenti ed edifici esistenti di inestimabile valore storico e artistico. Ciò ha
determinato l’adozione di particolari misure di salvaguardia per prevenire danni ai manufatti più vulnerabili.
A tale scopo, per verificare l’efficienza di barriere preinstallate per la riduzione degli effetti indotti dallo scavo
di gallerie, è stato predisposto un campo prova con una barriera costituita da una fila di pali accostati nel
tratto di linea tra le stazioni di Amba Aradam e San Giovanni, vicino a una sezione di monitoraggio di campo
libero. In questa nota sono mostrati i dati di monitoraggio registrati nella sezione di campo libero e in quella
in cui è presente la barriera. Le misure in sito sono state quindi interpretate con un’analisi a ritroso svolta con
il metodo degli elementi finiti, utilizzando tre procedure 2D di simulazione dello scavo della galleria
Uso di diaframmi in calcestruzzo per la riduzione degli spostamenti indotti dallo scavo di gallerie
No full textLa realizzazione di nuovi attraversamenti sotterranei in aree densamente urbanizzate è fortemente condizio-nata dalla necessità di limitare gli effetti indotti dalle operazioni di scavo sugli edifici posti nelle vicinanze. In questa nota si valuta l’efficacia di barriere costituite da diaframmi in calcestruzzo nella riduzione degli spo-stamenti indotti dallo scavo di gallerie. A tale scopo, sono state eseguite analisi numeriche con il metodo degli elementi finiti, confrontando gli spostamenti verticali calcolati in presenza e in assenza dell’intervento. Nelle analisi si è assunto un terreno a grana fine omogeneo e si sono ipotizzate condizioni di deformazione piana, corrispondenti a un diaframma continuo indefinitamente esteso e a una galleria interamente passata; si è inoltre assunto che l’edificio da proteggere segua gli spostamenti del terreno. L’efficacia dell’intervento è stata valu-tata mediante un’analisi parametrica, confrontando schemi caratterizzati, a parità di configurazione del dia-framma di protezione, da diversi valori del diametro e della copertura della galleria.Ground movements induced by tunnelling in urban areas can be reduced by pre-installing a protective barrier between the tunnel and a nearby building. Acting as a passive intervention, the diaphragm wall limits the propagation of displacements, preventing structure damages with a favourable variation of the displacement field.
In this paper, the effectiveness of a continuous diaphragm, made of adjacent concrete panels, was investigated carrying out plane-strain numerical analyses, assuming the building to follow the ground movements. Simplified soil conditions of a homoge-neous deposit of sandy silt were also assumed to car-ry out the parametric study. Two values of the tunnel diameters were considered and the depth of the tun-nel axis was changed to simulate the schemes of shallow, intermediate and deep tunnel characterised by cover to diameter ratio C/Dt = 1.6, 2, 3.2 respec-tively. In all the analyses, the achievement of a no-tional volume loss at the ground surface VL = 1% was imposed; the offset of the diaphragm from the tunnel axis was equal to d = 0.8·Dt, and its length was set to L = z0 + Dt, where Dt is the tunnel diame-ter. Moreover, a fully rough interface was assumed at the soil-diaphragm contact that provides lower values of efficiency, thus representing a conservative assumption (Rampello et al., 2016a).
The capacity of a protecting diaphragm to reduce the ground movements was evaluated through the comparison of the displacements fields computed beyond the wall in the presence and in absence of the intervention. A local and an integral efficiency were defined, the first providing the settlement re-duction at a given distance from the tunnel axis, while the second providing an overall index of set-tlement reduction. The highest reduction of soil set-tlement beyond the diaphragm is computed for the shallow tunnels (C/Dt = 1.6), with values of loc = 91% irrespective of tunnel diameter. Local ef-ficiency reduces with increasing distance from tun-nel axis, with settlement reduction in the range of about 60% to 80% at a distance x =2Dt from the tunnel axis. Local efficiency also decreases with in-creasing the cover to diameter ratio. This can be as-cribed to the higher level of soil strength mobilisa-tion induced into the soil to get the same volume loss for deeper tunnels. Therefore, the shear stresses mo-bilised at the soil-diaphragm interface increase, this resulting in a reduction of the efficiency.
Consistently with the above observations, the in-tegral efficiency, which represents an overall index of settlement reduction, decreases about linearly as the C/Dt ratio increases, providing similar values irre-spective of the tunnel diameter: from int ≈ 85% for C/Dt = 1.6 to int ≈ 70% for C/Dt = 3.2
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
In tema di Autotrasfusione: salasso preoperatorio immediato ed emodiluizione moderata con Destrano 70.000
No full textDopo alcuni cenni storici relativi alla metodica vengono ricordati i vari tipi di tecniche in uso per realizzare l'autotrasfusione.
La tecnica adottata dagli autori e realizzata in vari tipi di chirurgia, prevede un salasso preoperatorio immediato con emodiluizione moderata ottenuta con destrano 70.000; il sangue prelevato è stato sempre trasfuso durante o al termine degli intervent
Variazione della glicemia dopo somministrazione e.v. diBenzodiazepine,di morfino-simili e durante chirurgia addominale in anestesia endovenosa bilanciata
No full textIl comportamento della glicemia viene controllato in una serie di valutazioni sotto l'effetto delle benzodiazepine diverse e di farmaci morfinosimili somministrati via e.v. quindi durante interventi di colecistectomia
Square Dancing with the Stars to Enhance Dynamic Hirschman Linkages?
No full textIn this Presidential Address, the author takes the reader on a reconnaissance of his life and time as a regional scientist. He points out scenery he found scintillating along the way, hoping that some may pick up the banner and chew on a few of the ideas for a while. He suggests a revisit to Albert O. Hirschman’s notion of key sectors and more empirical analysis related to Marcus Berliant’s and Masahisa Fujita’s notion of knowledge creation and transfer.Presidential Address, San Antonio, Texas, March 29, 2014 (53rd Meetings of the Southern Regional Science Association
Behaviour of stabilizing piles arranged with different layouts
No full textStabilizing piles can be designed to increase the safety factor of a landslide (acting as a stabilization countermeasure) or to reduce slope displacements (acting as a protection countermeasure). Equally spaced piles are usually installed, in one or more rows transversal to ground movements, adopting a linear arrangement. Since piles must be designed to ensure adequate safety factors for both slope stability and pile structural integrity, the paper focuses on a different plane layout, namely a quincunx array, that can be an alternative design choice. A 2D and 3D numerical study has been developed, with the aim to compare the overall behaviour of a two-layer slope reinforced with one row of piles arranged with linear or quincunx layouts: soil arching effect, ground movements and resisting forces are analysed and discussed in the pape
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe 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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