1,720,967 research outputs found
A dynamic evolution model for perfectly plastic plates
No full textWe consider the dynamic evolution of a linearly elastic-perfectly plastic plate subject to a purely vertical body load. As the thickness of the plate goes to zero, we prove that the three-dimensional evolutions converge to a solution of a certain reduced model. In this limit model admissible displacements are of Kirchhoff-Love type. Moreover, the motion of the body is governed by an equilibrium equation for the stretching stress, a hyperbolic equation involving the vertical displacement and the bending stress, and a rate-independent plastic flow rule. Some further properties of the reduced model are also discussed
A compatible-incompatible decomposition of symmetric tensors in Lp with application to elasticity
No full textOne-month follow-up of patients treated by intravenous clodronate for acute pain induced by osteoporotic vertebral fracture.
No full textSMALL BOWEL STROMAL TUMORS. REPORT OF TWO CASES
No full textAIM OF THE STUDY: The Authors report on two cases of small bowel stromal tumours and underline more recent findings regard to histogenesis, etiopathogenesis and classification as well examine the problems related to diagnosis, surgical management and prognosis of these pathology. CONCLUSIONS: At present, surgical treatment is the best therapy even in patients with local relapse and/or metastasis. Whereas in unresectable patients a new therapeutic possibility is given to the use of Imatinib mesylate, nevertheless is still to prove its effectiveness in regard to survival or as adyuvant treatment in resectable patients with high risk of relapse
Existence and regularity of solutions for an evolution model of perfectly plastic plates
No full textWe continue the study of a dynamic evolution model for perfectly plastic plates, recently derived in [19] from three-dimensional Prandtl-Reuss plasticity. We extend the previous existence result by introducing non-zero external forces in the model, and we discuss the regularity of the solutions thus obtained. In particular, we show that the first derivatives with respect to space of the stress tensor are locally square integrable
Quasistatic evolution of perfectly plastic shallow shells: a rigorous variational derivation
No full textIn this paper, we rigorously deduce a quasistatic evolution model for shallow shells by means of (Formula presented.)-convergence. The starting point of the analysis is the three-dimensional model of Prandtl–Reuss elasto-plasticity. We study the asymptotic behaviour of the solutions, as the thickness of the shell tends to zero. As in the case of plates, the limiting model is genuinely three-dimensional, limiting displacements are of Kirchhoff–Love type, and the stretching and bending components of the stress are coupled in the flow rule and in the stress constraint. However, in contrast with the case of plates, the equilibrium equations are not decoupled, because of the presence of curvature terms. An equivalent formulation of the limiting problem in rate form is also discussed
A compatible-incompatible decomposition of symmetric tensors in Lp with application to elasticity
No full textIn this paper, we prove the Saint-Venant compatibility conditions in L-p for p is an element of(1, +infinity), in a simply connected domain of any space dimension. As a consequence, alternative, simple, and direct proofs of some classical Korn inequalities in L-p are provided. We also use the Helmholtz decomposition in L-p to show that every symmetric tensor in a smooth domain can be decomposed in a compatible part, which is the symmetric part of a displacement gradient, and in an incompatible part, which is the incompatibility of a certain divergence-free tensor. Moreover, under a suitable Dirichlet boundary condition, this Beltrami-type decomposition is proved to be unique. This decomposition result has several applications, one of which being in dislocation models, where the incompatibility part is related to the dislocation density and where 1 < p < 2. This justifies the need to generalize and prove these rather classical results in the Hilbertian case (p = 2), to the full range p is an element of(1,+infinity)
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
Comparison between Eight-Axis Articulated Robot and Five-Axis CNC Gantry Laser Metal Deposition Machines for Fabricating Large Components
Full text linkFeatured Application: Laser metal deposition of large axisymmetric components. Laser metal deposition (LMD) is an additive manufacturing (AM) process capable of producing large components for the aerospace and oil and gas industries. This is achieved by mounting the deposition head on a motion system, such as an articulated robot or a gantry computer numerical control (CNC) machine, which can scan large volumes. Articulated robots are more flexible and less expensive than CNC machines, which on the other hand, are more accurate. This study compares two LMD systems with different motion architectures (i.e., an eight-axis articulated robot and a five-axis CNC gantry machine) in producing a large gas turbine axisymmetric component. The same process parameters were applied to both machines. The deposited components show no significant differences in geometry, indicating that the different performances in terms of accuracy of the two machines do not influence the outcome. The findings indicate that LMD can consistently produce large-scale axisymmetric metal components with both types of equipment. For such an application, the user has the option of using an articulated robot when flexibility and cost are essential, such as in a research context, or a CNC machine where ease of programming and process standardization are important elements, such as in an industrial environment
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