Mechanics of fiber-reinforced hyperelastic solids

Recent designs for deployable space structures include elements that can be folded to high curvatures and recover elastically. A type of material proposed for such hinges is fiber composites with a soft silicone matrix. This research focuses on the characterization of this type of composites. Their mechanical properties during folding have been studied experimentally, revealing a highly non-linear moment-curvature relationship and stress softening, due to microdamage. The micromechanics of the problem have also been studied numerically, with a finite element model that takes into account the arrangement of the fibers. The model predicts most of the features observed experimentally, including the microbuckling that reduces fiber strain during folding. The model overestimates the material stiffness, due to its inability to model the damage taking place in the material. Current efforts are focused on modeling this damage process. In order to do so, the tension stiffness transverse to the fibers has been measured. Preliminary results including cohesive elements that delamination show good agreement with the tests

Folding of Thin Composite Structures with a Soft Matrix

The paper presents detailed micromechanical finite element simulations of composite materials with soft materials undergoing large macroscopic bending deformation. The simulations allow the study of fibre microbuckling under bending, including the kinematics of the fibres, as well as the strains in the matrix. These simulations lead to a simple analytical model that allows a quite accurate estimation of the buckling wavelength. It also provides the moment-curvature relationship. Finally, the model is also able to predict the maximum strain in the fibres for a given curvature

PREVALENCIA DE LA HIPERTENSION PULMONAR COMO COMPLICACION EN PACIENTES CON ENFERMEDAD RENAL CRONICA TERMINAL EN HEMODIALISIS EN EL HOSPITAL GENERAL DE ECATEPEC “DR. JOSE MARIA RODRIGUEZ”

RESUMEN ANTECEDENTES: La Enfermedad Renal Crónica presenta múltiples complicaciones Cardiovasculares y de estas una de las menos estudiadas es la HIPERTENSION PULMONAR, la cual se presenta más aun en los pacientes con terapia sustitutiva de Hemodiálisis. MATERIAL Y METODOS: Se realizó un estudio Descriptivo, Retrospectivo y Transversal. En base al estudio de 46 pacientes que se encuentran con el diagnostico de Enfermedad Renal Crónica Terminal en terapia sustitutiva de la función renal a base de Hemodiálisis a los cuales se les realizo un Ecocardiograma Transtoracico Tisular y Pulsado para valorar la existencia de hipertensión pulmonar. RESULTADOS: De los 46 pacientes en Hemodiálisis, solo uno fue excluido del estudio por presentar datos compatibles con hipocinesia miocardica, así un total de 45 estudios fueron incluidos. Se reporta que 13 pacientes (19.11%) No presentaron hipertensión Pulmonar y que 55 pacientes (80.88%) presentaron hipertensión pulmonar, de los cuales 41 pacientes (74.54%%) siendo hipertensión Pulmonar Leve, 11 pacientes (20%) de hipertensión Pulmonar Moderada y 3 paciente (5.45%) de hipertensión Pulmonar Severa. CONCLUSIONES: De los pacientes de la Unidad de Hemodiálisis del Hospital General de Ecatepec “Dr. José María Rodríguez” un alto porcentaje (Incidencia) presentan hipertensión pulmonar y que estos se encuentran Sub-diagnosticados

Curvature-Controlled Defect Localization in Elastic Surface Crystals

We investigate the influence of curvature and topology on crystalline dimpled patterns on the surface of generic elastic bilayers. Our numerical analysis predicts that the total number of defects created by adiabatic compression exhibits universal quadratic scaling for spherical, ellipsoidal, and toroidal surfaces over a wide range of system sizes. However, both the localization of individual defects and the orientation of defect chains depend strongly on the local Gaussian curvature and its gradients across a surface. Our results imply that curvature and topology can be utilized to pattern defects in elastic materials, thus promising improved control over hierarchical bending, buckling, or folding processes. Generally, this study suggests that bilayer systems provide an inexpensive yet valuable experimental test bed for exploring the effects of geometrically induced forces on assemblies of topological charges.MIT Masdar ProgramSwiss National Science Foundation (148743)Solomon Buchsbaum AT&T Research FundAlfred P. Sloan Foundation (Sloan Research Fellowship)National Science Foundation (U.S.) (CAREER CMMI-1351449

Parameter identification of periodical signals: Application to measurement and analysis of ocean wave forces

This article presents an approach based on state observers to identify the parameters of an unknown periodic force exerted on a mechanical system. This approach comprises two stages and can be executed in real time by using only displacement measurements. The first stage goal is the estimation of the coefficients of a Fourier series that approximates the periodic force. From the estimated coefficients, the phase and the amplitude of the signal can be simultaneously computed; and from the estimated force, in a second stage, the frequencies of the signal can be estimated. To perform the tasks at each stage, two state observers were designed. To show the applicability of the proposed approach, the reconstruction of a wave force affecting a marine structure as well as the computation of the amplitude and phase of its spectral components was taken as case of study. The performance of the state observer was examined by means of simulations and off-line tests carried out with experimental data. Such data were obtained by executing laboratory tests and measuring waves in the Caribbean sea

The Geometric Role of Precisely Engineered Imperfections on the Critical Buckling Load of Spherical Elastic Shells

We study the effect of a dimplelike geometric imperfection on the critical buckling load of spherical elastic shells under pressure loading. This investigation combines precision experiments, finite element modeling, and numerical solutions of a reduced shell theory, all of which are found to be in excellent quantitative agreement. In the experiments, the geometry and magnitude of the defect can be designed and precisely fabricated through a customizable rapid prototyping technique. Our primary focus is on predictively describing the imperfection sensitivity of the shell to provide a quantitative relation between its knockdown factor and the amplitude of the defect. In addition, we find that the buckling pressure becomes independent of the amplitude of the defect beyond a critical value. The level and onset of this plateau are quantified systematically and found to be affected by a single geometric parameter that depends on both the radius-to-thickness ratio of the shell and the angular width of the defect. To the best of our knowledge, this is the first time that experimental results on the knockdown factors of imperfect spherical shells have been accurately predicted, through both finite element modeling and shell theory solutions.National Science Foundation (U.S.) (CMMI-1351449

Reliability of a 3D Body Scanner for Anthropometric Measurements of Central Obesity

Background Central obesity poses a significant risk for cardiovascular diseases, but the reproducibility of manual measurements of waist and hip circumferences has been questioned. An automated 3D body scanner that uses white light rays could potentially increase the reliability of these anthropometric measurements. Methods We assessed the reproducibility of anthropometric measurements performed manually and using a 3D-scanner in 83 adult volunteers. Manual measures of WC and HC were obtained using unmarked, non-elastic ribbons in order to avoid observer and confirmation bias. The 3D-scanner was used to create body images and to obtain WC and HC measurements in an automated fashion. Results The inter-observer mean differences were 3.9 ± 2.4 cm for WC; 2.7 ± 2.4 cm, for HC, and 0.006 ± 0.02 cm for WHR. Intra-observer mean differences for manual measurements were 3.1 ± 1.9 cm for WC, 1.8 ± 2.2 cm for HC and 0.11 ± 0.1 cm for WHR. The 3D-scanner variability for WC was 1.3 ± 0.9 cm, for HC was 0.8 ± 0.1 and 0.005 ± 0.01 cm for WHR. All means were significantly different (p<0.05) between manual and automated methods. Conclusion The 3D-scanner is a more reliable and reproducible method for measuring WC, HC and WHR to detect central obesity

Kardiovize Brno 2030 – projekt prevence onemocnění srdce a cév pro brněnskou populaci a příklady podobných projektů ve světě

Ačkoliv je ischemická choroba srdeční chronické onemocnění, její výskyt se může v rámci populace zásadně měnit, stejně tak jako výskyt jiných onemocnění srdce a cév. V letech 1971–1982 patřila Česká republika k zemím s nejvyšší mortalitou na kardiovaskulární onemocnění v Evropě. Od roku 1990 dochází k postupnému poklesu mortality, nicméně i ta je ale stále vysoká ve srovnání se zeměmi západní Evropy (rozdíl zhruba 5–6let v očekávané délce života u mužů a 4 roky rozdíl u žen)

Causal Scoring Medical Image Explanations: A Case Study On Ex-vivo Kidney Stone Images

On the promise that if human users know the cause of an output, it would enable them to grasp the process responsible for the output, and hence provide understanding, many explainable methods have been proposed to indicate the cause for the output of a model based on its input. Nonetheless, little has been reported on quantitative measurements of such causal relationships between the inputs, the explanations, and the outputs of a model, leaving the assessment to the user, independent of his level of expertise in the subject. To address this situation, we explore a technique for measuring the causal relationship between the features from the area of the object of interest in the images of a class and the output of a classifier. Our experiments indicate improvement in the causal relationships measured when the area of the object of interest per class is indicated by a mask from an explainable method than when it is indicated by human annotators. Hence the chosen name of Causal Explanation Score (CaES