1,722,041 research outputs found
Scuola di formazione di italiano lingua seconda straniera competenze d’ uso e integrazione
No full textAncora a proposito della riforma della legittima difesa. tra ragioni di 'liceità' e cause di 'scusa'
Full text linkYield, Quality and Antioxidant Properties of Indian Mustard (Brassica juncea L.) in Response to Foliar Biofortification with Selenium and Iodine
No full textOne of the possible ways to challenge selenium (Se) and iodine (I) deficiency in human
beings is the joint biofortification of plants with these elements. Though the relationship between
Se and I is highly pronounced in mammals, little is known about their interactions in plants where
Se and I are considered not to be essential. Peculiarities of Se and I assimilation by a natural Se
accumulator, such as Brassica juncea L., cultivar Volnushka, were assessed upon joint and separate
plant foliar supply with sodium selenate (50 mg Se L1) and potassium iodide (100 mg I L1), in two
crop seasons (spring, summer). Conversely to the individual application of Se and I, their joint
supply did not stimulate plant growth. Separate use of sodium selenate enhanced I accumulation
by 2.64 times, while biofortification with I increased the Se content in plant leaves by 4.3 times; this
phenomenon was also associated with significant increase of total soluble solids and ascorbic acid
content in leaves. The joint supply of Se and I did not affect the mentioned parameters. Both joint
and separate application of Se and I led to synergism between these elements in: inhibiting nitrate
accumulation; stimulating flavonoids biosynthesis (2–2.3 times compared to control plants) as well as
Al and B accumulation; decreasing Cd and Sr concentrations. Plant biofortification with I increased
the content of Mn and decreased K and Li. The consumption of 100 g Brassica juncea leaves provided
100% of the adequate human requirement of Se and 15.5% of I
Frequency split and vibration localization in imperfect rings
No full textThe dynamics of linearly elastic, imperfect rings vibrating in their own plane is considered in this paper. Imperfections are modeled as perturbations of the uniform linear mass density and bending stiffness of a perfect ring. A perturbation expansion and a spectral representation are employed, and a variational formulation of the vibration problem is obtained. A linear theory is deduced by retaining only the leading-order terms in the variational formulation. The linear theory yields simple, closed-form expressions for the eigenfrequencies and the modal shapes, which are accurate when the imperfections are sufficiently small. An enhanced, nonlinear theory is also derived, which is accurate even when the ring imperfections are not small: in this case, an iterative solution procedure is developed. The proposed theories are validated by considering some case-study problems and using the Ritz-Rayleigh solution as a benchmark. Finally, the linear theory is applied to the frequency trimming problem of an imperfect ring. A simple, closed-form expression for the trimming masses is presented, valid for trimming any selected number of eigenmodes. 2007 Elsevier Ltd. All rights reserved
Un modello omogeneizzato per l'analisi dinamica di strutture con periodicità rotazionale
Full text linkThis paper deals with the dynamic analysis of rotationally periodic structures. In particular, a structure composed of angularly equally-spaced blades mounted on a flexible ring is considered. A simplified model of the dynamical behavior of the structure is obtained by employing a homogenization technique. The eigenfrequencies and eigenmodes evaluated by applying the proposed model are compared to the corresponding ones obtained via a finite-element approach
Analysis of the vibration localization phenomenon in imperfect rings
Full text linkThe modal analysis of imperfect rings vibrating in their own plane is considered in this paper. The imperfections are modeled as generic perturbations, depending on the angular variable, of the linear mass density and the bending stiffness of the ring. The Euler-Bernoulli theory is used to develop the dynamical model of the ring, and a perturbation expansion of the solution is performed in order to find out the modal split eigenfrequencies and the relevant perturbed modal shapes. Finally, some case-study problems are considered and the analytical results obtained by using the proposed approach are compared to results obtained by employing a finite-element model of the imperfect ring
Closed-form formulas for the optimal pole-based design of tuned mass dampers
No full textThis paper deals with the analysis and optimization of tuned mass dampers (TMDs). It provides design formulas for maximizing the exponential time-decay rate (ETDR) of the system transient response. A detailed analysis is presented for the classical TMD configuration, involving an auxiliary mass attached to the main structure by means of a spring and a dashpot. Analytic expressions of the optimal ETDR are obtained for any mass ratio and tuning condition. Then, a further optimization with respect to the latter is performed. The proposed method is applied also to other TMD configurations involving an auxiliary mass connected to both the main structure and the ground, as well as to a piezoelectric damping device. A justification to the well-known heuristic optimality condition based on the enforcement of coincident couples of complex conjugate poles is presented. That condition is shown, however, to fail in providing optimal solutions for some mass ratio values and/or TMD configurations, and the optimality conditions prevailing in those cases are derived. The present analysis, besides its theoretical interest, may be useful in practical applications, e.g., to assess the sensitivity of the optimal ETDR with respect to the design parameters or to promptly adjust some of those parameters during service, after any variation of the operative conditions
Mindlin-type finite elements for piezoelectric sandwich plates
No full textNew finite-element formulations are developed for the analysis of a plate having thin piezoelectric actuators bonded on its upper and/or lower surfaces. The proposed finite elements are two-dimensional, quadrangular, four-node, Mindlin-type, locking-free, and have five degrees of freedom per node. These are the deflection of the middle plane of the plate, the rotations of the fibers normal to the middle plane and the actuation electric potentials of the piezoelectric actuators. The effectiveness of the proposed finite-element formulations is shown by studying some case problems, whose analytical solutions are available
Preface for the special issue “NFT-05: Italy and Greece”: nuclear fission technology in Italy
No full textAfter the successful experience in the ‘60s and ‘70s, a bright future for nuclear energy suddenly became opaque after the Chernobyl accident; however, nuclear energy still can hold its promises. Noticeably, some research continued after that event, and valuable expertise has persisted in industry, research centers, and universities. The commitment to research on the safety aspects of current reactor generations and advanced reactors using passive safety systems should be underlined. Even though Large Reactor Units (LRUs) have demonstrated the capability to benefit a country like Italy, Small Modular Reactor (SMR) technology might have a role in fulfilling the zero carbon target. In fact, in the short term, light water SMR designs appear to be a target of the strategy for the Italian government to fulfil the zero-carbon target. Notably, there is also interest in the future deployment of Gen-4 reactors, particularly lead-cooled fast reactors, considering the expertise in the country. Greek scientists did not participate in the activities of the present VSI. Therefore, the discussion below deals with Italy only
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