Pancreatoscopy-guided electrohydraulic lithotripsy in a patient with calcific chronic pancreatitis

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Masonry behaviour and modelling

In this Chapter we present the basic experimental facts on masonry materials and introduce simple and refined models for masonry. The simple models are essentially macroscopic and based on the assumption that the material is incapable of sustaining tensile loads (No-Tension assumption). The refined models account for the microscopic structure of masonry, modeling the interaction between the blocks and the interfaces.(undefined

Point-Coupling Models from Mesonic Hypermassive Limit and Mean-Field Approaches

In this work we show how nonlinear point-coupling models, described by a Lagrangian density that presents only terms up to fourth order in the fermion condensate $(\bar{\psi}\psi)$, are derived from a modified meson-exchange nonlinear Walecka model. The derivation can be done through two distinct methods, namely, the hypermassive meson limit within a functional integral approach, and the mean-field approximation in which equations of state at zero temperature of the nonlinear point-coupling models are directly obtained.Comment: 18 pages. Accepted for publication in Braz. J. Phy

Preventing Atomicity Violations with Contracts

Software developers are expected to protect concurrent accesses to shared regions of memory with some mutual exclusion primitive that ensures atomicity properties to a sequence of program statements. This approach prevents data races but may fail to provide all necessary correctness properties.The composition of correlated atomic operations without further synchronization may cause atomicity violations. Atomic violations may be avoided by grouping the correlated atomic regions in a single larger atomic scope. Concurrent programs are particularly prone to atomicity violations when they use services provided by third party packages or modules, since the programmer may fail to identify which services are correlated. In this paper we propose to use contracts for concurrency, where the developer of a module writes a set of contract terms that specify which methods are correlated and must be executed in the same atomic scope. These contracts are then used to verify the correctness of the main program with respect to the usage of the module(s). If a contract is well defined and complete, and the main program respects it, then the program is safe from atomicity violations with respect to that module. We also propose a static analysis based methodology to verify contracts for concurrency that we applied to some real-world software packages. The bug we found in Tomcat 6.0 was immediately acknowledged and corrected by its development team

Endometriosis: A Rare Cause of Large Bowel Obstruction.

Large bowel obstruction can result in significant morbidity and mortality, especially in cases of acute complete obstruction. There are many possible causes, the most common in adults being colorectal cancer. Endometriosis is a benign disease, and the most affected extragenital location is the bowel, especially the rectosigmoid junction. However, transmural involvement and acute occlusion are very rare events. We report an exceptional case of acute large bowel obstruction as the initial presentation of endometriosis. The differential diagnosis of colorectal carcinoma may be challenging, and this case emphasizes the need to consider intestinal endometriosis in females at a fertile age presenting with gastrointestinal symptoms and an intestinal mass causing complete large bowel obstruction.info:eu-repo/semantics/publishedVersio

FE homogenized limit analysis code for masonry buildings

In this paper, a FE homogenized limit analysis code for the collapse analysis of 3D masonry buildings subjected to horizontal actions is presented. In the code, masonry is modelled through a fictitious macroscopic homogeneous material. Masonry macroscopic mechanical properties are obtained by means of a recently presented equilibrated limit analysis approach performed on a suitable unit cell, which generates the entire structure by repetition. Masonry homogenised failure surfaces are then implemented in the 3D code here outlined. With respect to previously presented models, the algorithm allows to analyze real scale buildings for coupled in-plane and out-of-plane actions. The possible presence of steel, RC and ring beams is also considered introducing in the numerical model two-node beam elements. A relevant 3D structural example consisting of a masonry school subjected to horizontal actions is treated. Full sensitivity analyses and a comparison with results obtained with a commercial elasto-plastic software are also presented to validate the model proposed

Simple homogenized model for the non-linear analysis of FRP strengthened masonry structures. Part I : theory

A suitable and simple two-step model able to predict the non-linear response of FRP strengthened 13 three-dimensional masonry structures is presented. In the first step, non-strengthened masonry is 14 substituted by a macroscopically equivalent homogeneous material through a kinematic model 15 based on finite elements and working on a heterogeneous assemblage of blocks. Non-linearity is 16 concentrated exclusively on joints reduced to interfaces, exhibiting a frictional behavior with 17 limited tensile and compressive strength with softening. The homogenized stress-strain behavior 18 evaluated at the meso-scale is then implemented at a structural level in a finite element non-linear 19 code, relying on an assemblage of rigid infinitely resistant six-noded wedge elements and non-linear 20 interfaces, exhibiting deterioration of the mechanical properties. FRP reinforcing strips are modeled 21 through rigid triangles and non-linear interfaces between adjoining triangles. Delamination from the 22 support is accounted for, by modeling FRP-masonry bond by means of non-linear softening 23 triangular interfaces. Italian code CNR DT 200 (2004) formulas are used to evaluate peak interface 24 tangential strength and post peak behavior. In this first part, the theoretical base of the model and 25 the non-linear stress strain behavior at a cell level are discussed. Structural examples will be 26 analyzed in the accompanying paper devoted to the structural scale

Simple homogenized model for the non-linear analysis of FRP strengthened masonry structures. Part II : structural applications

The homogenized masonry nonlinear stress-strain curves obtained through the simple micromechanical model developed in the first part of the paper are here used for the analysis of strengthened masonry walls under various loading conditions. In particular, a deep beam and a shear wall strengthened with fiber-reinforced polymer (FRP) strips are analyzed for masonry loaded in-plane. Additionally, single and double curvature masonry structures strengthened in various ways, namely a circular arch with buttresses and a ribbed cross vault, are considered. For all the examples presented, both the nonstrengthened and FRP–strengthened cases are discussed. Additional nonlinear finite-element analyses are performed, modeling masonry through an equivalent macroscopic material with softening to assess the present model predictions. Detailed comparisons between the experimental data, where available, and numerical results are also presented. The examples show the efficiency of the homogenized technique with respect to (1) accuracy of the results; (2) low number of finite elements required; and (3) independence of the mesh at a structural level from the actual texture of masonry

Monte Carlo homogenized limit analysis model for randomly assembled blocks in-plane loaded

A simple rigid-plastic homogenization model for the limit analysis of masonry walls in-plane loaded and constituted by the random assemblage of blocks with variable dimensions is proposed. In the model, blocks constituting a masonry wall are supposed infinitely resistant with a Gaussian distribution of height and length, whereas joints are reduced to interfaces with frictional behavior and limited tensile and compressive strength. Block by block, a representative element of volume (REV) is considered, constituted by a central block interconnected with its neighbors by means of rigid-plastic interfaces. The model is characterized by a few material parameters, is numerically inexpensive and very stable. A sub-class of elementary deformation modes is a-priori chosen in the REV, mimicking typical failures due to joints cracking and crushing. Masonry strength domains are obtained equating the power dissipated in the heterogeneous model with the power dissipated by a fictitious homogeneous macroscopic plate. Due to the inexpensiveness of the approach proposed, Monte Carlo simulations can be repeated on the REV in order to have a stochastic estimation of in-plane masonry strength at different orientations of the bed joints with respect to external loads accounting for the geometrical statistical variability of blocks dimensions. Two cases are discussed, the former consisting on full stochastic REV assemblages (obtained considering a random variability of both blocks height an length) and the latter assuming the presence of a horizontal alignment along bed joints, i.e. allowing blocks height variability only row by row. The case of deterministic blocks height (quasi-periodic texture) can be obtained as a subclass of this latter case. Masonry homogenized failure surfaces are finally implemented in an upper bound FE limit analysis code for the analysis at collapse of entire walls in-plane loaded. Two cases of engineering practice, consisting on the prediction of the failure load of a deep beam and a shear wall arranged with random texture are critically discussed. In particular, homogenization results are compared with those provided by a heterogeneous approach. Good agreement is found both on the failure mechanism and on the distribution of the collapse load

Blast analysis of enclosure masonry walls using homogenization approaches

A simple rigid-plastic homogenization model for the analysis of enclosure masonry walls sub- jected to blast loads is presented. The model is characterized by a few material parameters, is numerically inexpensive and very stable, and allows full parametric studies of entire walls subject to blast pressures. With the aim of considering the actual brickwork strength along vertical and horizontal axes, masonry out-of-plane anisotropic failure surfaces are obtained by means of a compatible homogenized limit analysis approach. In the model, a 3D system of rigid infinitely strong bricks connected by joints reduced to interfaces is identified with a 2D Kirchhoff-Love plate. For the joints, which obey an associated flow rule, aMohr-Coulomb fail- ure criterion with a tension cutoff and a linearized elliptic compressive cap is considered. In this way, the macroscopic masonry failure surface is obtained as a function of the macroscopic bending, torque, and in-plane forces by means of a linear programming problem in which the internal power dissipated is minimized. Triangular Kirchhoff-Love elements with linear in- terpolation of the displacements field and constant moment within each element are used at a structural level. In this framework, a simple quadratic programming problem is obtained to analyze entire walls subjected to blast loads. The multiscale strategy presented is adopted to predict the behavior of a rectangular wall supported on three sides (left, bottom, and right) representing an envelope wall in a building and subjected to a standardized blast load. The top edge of the wall is assumed unconstrained due to an imperfect connection (often an inter- layer material is used to prevent damage in the in-fill wall). A comparison with a standard elastic-plastic heterogeneous 3D analysis conducted with a commercial FE code is also pro- vided for a preliminary verification of the procedure at a structural level. The good agreement found and the very limited computational effort required for the simulations conducted with the presented model indicate that the proposed simple tool can be used by practitioners for the safety assessment of out-of-plane loaded masonry panels subjected to blast loading. An ex- haustive parametric analysis is finally conducted with different wall thicknesses, joint tensile strengths, and dynamic pressures, corresponding to blast loads (in kilograms of TNT) ranging from small to large