170,835 research outputs found
On the Choice of Tool Material in Friction Stir Welding of Titanium Alloys
No full textFriction Stir Welding (FSW) is a solid state welding process patented in 1991 by TWI; initially adopted to weld aluminum alloys, is now being successfully used also for magnesium alloys, copper and steels. The wide diffusion the process is having is due to the possibility to weld both materials traditionally considered difficult to be welded or "unweldable" by traditional fusion welding processes due to peculiar thermal and chemical material properties, and complex geometries as sandwich structures and straightening panels. Recently, research is focusing on titanium alloys thanks to the high interest that such materials are getting from the industry due to the extremely high strength-weight ratio together with good corrosion resistance properties. At the moment, the main limit to the industrial applicability of FSW to titanium alloys is the tool life, as ultra wear and deformation resistant materials must be used. In this paper a, experimental study of the tool life in FSW of titanium alloys sheets at the varying of the main process parameters is performed. Numerical simulation provided important information for the fixture design and analysis of results. Tungsten and Rhenium alloy W25Re tools are found to be the most reliable among the ones considered
Valutazione della qualità della vegetazione della torbiera delle Viote del Monte Bondone (TN) con lineamenti di corretta gestione ambientale.
No full text
Progettare la città, progettare il paesaggio. progetto per la riqualificazione urbana e paesaggistica di alcune aree del comune di Ceva.
No full textRemarks on Poincare and interpolation estimates for Truncated Hierarchical B-splines
No full textThis paper should be considered as an addendum to [A. Buffa and C. Giannelli, Adaptive isogeometric methods with hierarchical splines: Error estimator and convergence, Math. Models Methods Appl. Sci. 26 (2016) 1-25] and [A. Buffa and C. Giannelli, Adaptive isogeometric methods with hierarchical splines: Optimality and convergence rates, Math. Models Methods Appl. Sci. 27 (2017) 2781-2802] where Poincare and approximation estimates are used as theoretical tools to study properties of adaptive numerical methods based on hierarchical B-splines. After noting that the support of truncated hierarchical B-splines may be disconnected (and thus no Poincare estimate can hold), we study minimal extensions of their support on suitable mesh configurations such that (i) Poincare estimates can be established on them and (ii) their overlaps stay independent of the number of levels. The Poincare estimates proposed in this note should replace the ones used in the proofs of Theorem 11 and Lemma 7 in [A. Buffa and C. Giannelli, Adaptive isogeometric methods with hierarchical splines: Error estimator and convergence, Math. Models Methods Appl. Sci. 26 (2016) 1-25] and [A. Buffa and C. Giannelli, Adaptive isogeometric methods with hierarchical splines: Optimality and convergence rates, Math. Models Methods Appl. Sci. 27 (2017) 2781-2802], respectively, in order to include the most general meshes, i.e. the cases when the support of truncated basis functions can be disconnected.MN
Actions for plant biodiversity improvement and recovery in lowland ancient woods and artificial forest stands
No full textItalian forest ecosystems, characterized by a long tradition of forestry and agro-pastoral practices that have guided their evolution, have ensured the preservation over time of significant aspects of naturalness to which important landscape,ecological (carbon stock) and recreational values are associated.
These functions have become increasingly important leading to the implementation of several reforestation projects. Nevertheless, the new forest stands, born on lands subject to agricultural use for a long time, evolve into ecologically sustainable ecosystems only in a very long time.
One of the main findings of this process is represented both by the structure of biological communities and their complexity, which remain greatly simplified for a long time.
In particular, nemoral herbaceous species, which represent the most valuable and ecologically significant component of a forest habitat, remain confined to the ―ancient forests‖. These species, closely habitat-specific and substantially unable to adapt to the environmental changes (Buffa and Villani in pubbl.; Eckert, 2002; Honnay et al., 1999), are in risk of local extinction due to the small size and isolation of their populations.
In order to preserve the venetian lowland ecotypes, some experiments were started in 2010 with the aim of producing some target species (Arum maculatum L., Allium ursinum L., Asparagus tenuifolius Lam., Carex remota L., Colchicum autumnale L., Mercurialis perennis L., Lamium orvala L., Leucojum vernum L., Loncomelos pyrenaicum (L.) Hrouda ex J. Holub s.l., Paris quadrifolia L., Ranunculus auricomus L., Viola reichenbachiana Jordan ex Boureau).
The peculiarities of the environment in which these species are adapted impose a continuous integration of autoecology knowledge with plant nursery techniques. Thus in situ (ancient forest) and ex situ (germination room and outdoors cultivation tunnel) germination tests were carried out to understand how soil variables (texture, pH, organic C, N, P), physical environment variables (quantity and quality of light radiation in the undergrowth) and microclimatic variables (soil T at 0 cm) allow to break dormancy, induce germination and promote seedlings recruitment.
The comparison of in situ and ex situ tests showed that for the majority of the species germinating output is significantly higher in natural conditions or artificial conditions that simulate more accurately the natural ones than in germination room.
Seeds of some species kept at 20 ° C in dry storage (eg. Leucojum vernum L., Mercurialis perennis L.) showed a reduction of viability even more than 80% in 6 months since the collection date, proving potential recalcitrance, and explaining the negative results for their germination tests.
The first results encourage further tests in order to implement the knowledge on the production of these species, which is desirable both in terms of biodiversity conservation, and for the reinforcement of existing populations or for the naturalization of artificial forests. A new frontier, finally, may be offered by their use in private gardens (for aesthetic and naturalistic reasons, in a sort of transposition of the bird-gardening practice within the conservation of nemoral species), with the activation of a production chain giving also employment benefits
Dry deposition of particle on urban areas
Get PDFDry deposition process is recognized as an important pathway among the removal processes of radioactive pollutants in atmosphere. There is not a unique and accepted theoretical description of involved dry deposition phenomena due to the complexity of the fluid-dynamic processes that influence the deposition flux, but also because there is a lack of experimental data covering all scenarios of interest. In this paper, that is the result of a National Research Program a research activity conducted by DEIM Department of the University of Palermo and ENEA and funded by the Italian Minister of Economic Development, a new schema for parameterization of particle dry deposition velocity on urban area is proposed. The work required comparisons with some experimental data reported in literature for different particle deposition scenarios. The results show that the proposed approach can catch some aspects of phenomena involved in dry deposition processes for the examined environmental conditions with good agreement
Communication
No full text(1) "On a Paper by Scriabin and Vergin" by Elwood S. Buffa, Graduate School of Management, University of California, Los Angeles. (Comments on Scriabin, M., R. C. Vergin. 1975. Comparison of computer algorithms and visual based methods for plant layout. Management Sci. 22 (2) 172-181) (2) "Computer and Visual Methods for Plant Layout--A Rejoinder" by Michael Scriabin and Roger C. Vergin, Faculty of Management Sciences, Simon Fraser University, Burnaby, British Columbia, Canada. (Comments about details of Scriabin, M., R. C. Vergin. 1975. Comparison of computer algorithms and visual based methods for plant layout. Management Sci. 22 (2) 172-181 where Buffa [Scriabin, M., R. C. Vergin. 1976. Computer and visual methods for plant layout--a rejoinder. Management Sci. 23 (1) 104] felt were defects in research design)
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