1,071 research outputs found

    The random growth of interfaces as a subordinated process

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    We study the random growth of surfaces from within the perspective of a single column, namely, the fluctuation of the column height around the mean value, y(t)= h(t)-, which is depicted as being subordinated to a standard fluctuation-dissipation process with friction gamma. We argue that the main properties of Kardar-Parisi-Zhang theory, in one dimension, are derived by identifying the distribution of return times to y(0) = 0, which is a truncated inverse power law, with the distribution of subordination times. The agreement of the theoretical prediction with the numerical treatment of the 1 + 1 dimensional model of ballistic deposition is remarkably good, in spite of the finite size effects affecting this model.Comment: LaTeX, 4 pages, 3 figure

    Solution strategies for 1D elastic continuum with long-range interactions: Smooth and fractional decay

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    An elastic continuum model with long-range forces is addressed in this study within the context of approximate analytical methods Such a model stems from a mechanically-based approach to non-local theory where long-range central forces are introduced between non-adjacent volume elements Specifically, long-range forces depend on the relative displacement on the volume product between interacting elements and they are proportional to a proper, material-dependent, distance-decaying function Smooth-decay functions lead to integro-differential governing equations whereas hypersingular, fractional-decay functions lead to a fractional differential governing equation of Marchaud type In this paper the Galerkin and the Rayleigh-Ritz method are used to build approximate solutions to the integro-differential and the fractional differential governing equations Numerical applications show the accuracy of the proposed approximate solutions as compared to the finite difference approximation and to the fractional finite difference approximatio

    A new displacement-based framework for non-local Timoshenko beams

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    In this paper, a new theoretical framework is presented for modeling non-locality in shear deformable beams. The driving idea is to represent non-local effects as long-range volume forces and moments, exchanged by non-adjacent beam segments as a result of their relative motion described in terms of pure deformation modes of the beam. The use of these generalized measures of relative motion allows constructing an equivalent mechanical model of non-local effects. Specifically, long-range volume forces and moments are associated with three spring-like connections acting in parallel between couples of non-adjacent beam segments, and separately accounting for pure axial, pure bending and pure shear deformation modes. The variational consistency of the proposed non-local beam model is demonstrated by minimization of an appropriate total potential energy functional. Numerical results concerning the static behavior for different boundary and loading conditions are presented. It is shown that the proposed non-local beam model is able to capture experimental data on the static deflection of micro-beams, available in the literature

    Potassium partitioning between leaves and clusters: Role of rootstock

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    Different scion/rootstock combinations in grapevine (Vitis vinifera/Vitis spp.) were tested for nutritional properties and juice composition. Chardonnay and Cabernet Sauvignon each grafted on 22 rootstock varieties (10 new crosses and 12 already used in viticulture) were grown in outdoor pots containing very poor nutritional substrate. Crop load had a strong effect on juice composition and potassium nutrition. Results indicate that under our experimental conditions rootstock can have an effect on potassium partitioning between leaves and cluster 9 out of 22 rootstocks that we tried were able to improve leaf potassium content without inducing a significant increase in juice potassium conten

    Wild grapevine (Vitis vinifera var. silvestris) in Italy: Distribution, characteristics and germplasm preservation-1989 report

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    Research on the distribution and characteristics of wild grapevines (Vitis vinifera var. silvestris) in Italy was started whose main goals are: the preservation of the germplasm by setting up plant collections;the furthering of biological knowledge about this plant;the study of relations between wild and cultivated grapevines by means of chemotaxonomic techniques;the assessment of the possibility of using wild plants for genetic improvement of grapevines.The gathering of data began in 1984. 221 sites in 15 out of the 20 Italian regions have been indicated as possible locations in which wild grapevines grow. So far, 49 of these sites have been inspected. The greatest number of individuals were found in central Italy. This population is dioecious (male/female = 1.8) with few (2.0 %) hermaphrodite examples.The leaves of the Italian wild grapevines generally have 3 lobes (57 %), but 5 to 7-lobe (36%) and non-lobed (8.9 %) plants exist. Lower variability exists with regard to leaf shape. The study of seed morphology has classified the plants into three groupe, one of which is very numerous.Two germplasm collections have been established with approximately 400 vines

    On the vibrations of a mechanically based non-local beam model

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    The vibration problem of a Timoshenko non-local beam is addressed. The beam model involves assuming that the equilibrium of each volume element is attained due to contact forces and long-range body forces exerted, respectively, by adjacent and non-adjacent volume elements. The contact forces result in the classical Cauchy stress tensor while the long-range forces are taken as depending on the product of the interacting volume elements and on their relative displacement through a material-dependent distance-decaying function. To derive the motion equations and the related mechanical boundary conditions, the Hamilton's principle is appliedThe vibration problem of a Timoshenko non-local beam is addressed. The beam model involves assuming that the equilibrium of each volume element is attained due to contact forces and long-range body forces exerted, respectively, by adjacent and non-adjacent volume elements. The contact forces result in the classical Cauchy stress tensor while the long-range forces are taken as depending on the product of the interacting volume elements and on their relative displacement through a material-dependent distance-decaying function. To derive the motion equations and the related mechanical boundary conditions, the Hamilton's principle is applie

    Analysis of VvMybA1 and VvMybA2 genes in grape bud sports

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    Berry skin colour is a fundamental qualitative trait of grape varieties, which has become largely diversified during the centuries of viticulture. Colour mutations in grape berry, resulting in black, red, pink, grey, green and yellow fruits, were relatively frequent events. In the Carpathian Basin there are several berry colour variant groups named conculta, members of which contain bud sports differing in skin colour. In most cases, this difference cannot be detected by microsatellite analysis, therefore we examined the variations of the VvMybA1 and VvMybA2 genes related to anthocyanin biosynthesis. Based on the results of the allelic polymorphisms, we have discriminated the conculta members among the old Hungarian and several other foreign varieties. Based on our results, it was possible to find molecular differences in 10 out of 14 concultas

    The Durability of Composite Wood-Steel Systems

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    Nell\u2019ambito della valutazione e del controllo della qualit\ue0 tecnologica in edilizia, la conoscenza del comportamento nel tempo dei prodotti e componenti complessi per l\u2019edilizia, risulta aspetto fondamentale, in particolare per quei prodotti tecnologicamente \u201cinnovativi\u201d per i quali la normativa non prevede ancora prove specifiche per valutarne la durabilit\ue0. In particolare, oggi risulta sempre pi\uf9 diffuso l\u2019impiego di sistemi assemblati o con connessioni tra materiali di diversa natura, tra cui i sistemi legno-acciaio, ottenuti rinforzando le travi in legno lamellare con piastre in acciaio forate, incollati mediante una resina epossidica bicomponente. Tali sistemi, che sono stati gi\ue0 oggetto di sperimentazione sul comportamento a flessione del sistema trave in legno lamellare e solaio collaborante in calcestruzzo, affidano la loro efficacia in riguardo alla resistenza ed alla rigidezza attraverso gli sforzi di taglio e gli spostamenti relativi che in caso di buona collaborazione legno-acciaio sono molto ridotti. Il presente studio si occupa di indagare la durabilit\ue0 delle caratteristiche di aderenza legno-resina-acciaio del sistema, attraverso una sperimentazione condotta su campioni secondo le procedure della normativa ISO 15686. Dopo una prima fase di studio del sistema agenti-azioni-effetti \ue8 stato messo a punto un ciclo di invecchiamento accelerato e sono state effettuate le indagini in laboratorio in camera climatica. Il comportamento della connessione dopo vari livelli di invecchiamento \ue8 stato analizzato attraverso prove meccaniche di resistenza al taglio, azioni cui il sistema \ue8 sottoposto in esercizio, considerando sia le sollecitazioni climatiche che possono condizionare il comportamento dei singoli componenti del sistema: resina, acciaio e legno lamellare, sia il sistema nel suo insieme per cui risulta critico il comportamento all\u2019interfaccia legno-resina e resina-acciaio. I risultati ottenuti hanno fornito indicazioni interessanti sul comportamento del sistema nel tempo. Infatti con l\u2019avanzare dei cicli di invecchiamento si \ue8 manifestata una progressiva riduzione del carico massimo a rottura, mantenendo caratteristiche di rigidezza elevata, con spostamenti relativi ridottissimi anche sui campioni pi\uf9 invecchiati
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