91 research outputs found
A simplified approach to the topology optimization of structures in case of unilateral material/supports
A simplified method to cope with the topology optimization of truss–like structures in case of unilateral behavior of material or supports is presented. The conventional formulation for volume–constrained compliance minimization is enriched with a set of stress constraints that enforce a suitable version of the Drucker–Prager strength criterion in order to prevent the arising of tensile (or compressive) members
in the whole domain or within limited regions in the vicinity of the supports. The adopted numerical framework combines an ad hoc selection strategy along with the use of aggregation techniques that succeed in driving the energy–based minimization towards feasible designs through the enforcement of a limited number of stress constraints. Numerical simulations assess the proposed optimization framework in comparison with methods that are based on a full non–linear modeling of unilateral material/supports. An extension to the safety analysis of structures made of no–tension material is also highlighted
Point configurations that are asymmetric yet balanced
A configuration of particles confined to a sphere is balanced if it is in
equilibrium under all force laws (that act between pairs of points with
strength given by a fixed function of distance). It is straightforward to show
that every sufficiently symmetrical configuration is balanced, but the converse
is far from obvious. In 1957 Leech completely classified the balanced
configurations in R^3, and his classification is equivalent to the converse for
R^3. In this paper we disprove the converse in high dimensions. We construct
several counterexamples, including one with trivial symmetry group.Comment: 10 page
Contribution of positron emission tomography in pleural disease.
INTRODUCTION: Positron emission tomography (PET) now plays a clear role in oncology, especially in chest tumours. We discuss the value of metabolic imaging in characterising pleural pathology in the light of our own experience and review the literature. BACKGROUND: PET is particularly useful in characterising malignant pleural pathologies and is a factor of prognosis in mesothelioma. Metabolic imaging also provides clinical information for staging lung cancer, in researching the primary tumour in metastatic pleurisy and in monitoring chronic or recurrent pleural pathologies. CONCLUSIONS: PET should therefore be considered as a useful tool in the diagnosis of liquid or solid pleural pathologies
Poly[ethylenediammonium [tris[μ3-hydrogenphosphato(2−)]dicadmium] monohydrate]
The title compound, {(C2H10N2)[Cd2(HPO4)3]·H2O}n, was synthesized under hydrothermal conditions. The structure of this hybrid compound consists of CdO6, CdO5 and PO4 polyhedra arranged so as to build an anionic inorganic layer, namely [Cd2(HPO4)3]2−, parallel to the ab plane. The edge-sharing CdO6 octahedra form infinite chains running along the a axis and are linked by CdO5 and PO4 polyhedra. The ethylenediammonium cation and the water molecule are located between two adjacent inorganic layers and ensure the cohesion of the structure via N—H⋯O and O—H⋯O hydrogen bonds
Malignant mesothelioma
Malignant mesothelioma is a fatal asbestos-associated malignancy originating from the lining cells (mesothelium) of the pleural and peritoneal cavities, as well as the pericardium and the tunica vaginalis. The exact prevalence is unknown but it is estimated that mesotheliomas represent less than 1% of all cancers. Its incidence is increasing, with an expected peak in the next 10–20 years. Pleural malignant mesothelioma is the most common form of mesothelioma. Typical presenting features are those of chest pain and dyspnoea. Breathlessness due to a pleural effusion without chest pain is reported in about 30% of patients. A chest wall mass, weight loss, sweating, abdominal pain and ascites (due to peritoneal involvement) are less common presentations. Mesothelioma is directly attributable to occupational asbestos exposure with a history of exposure in over 90% of cases. There is also evidence that mesothelioma may result from both para-occupational exposure and non-occupational "environmental" exposure. Idiopathic or spontaneous mesothelioma can also occur in the absence of any exposure to asbestos, with a spontaneous rate in humans of around one per million. A combination of accurate exposure history, along with examination radiology and pathology are essential to make the diagnosis. Distinguishing malignant from benign pleural disease can be challenging. The most helpful CT findings suggesting malignant pleural disease are 1) a circumferential pleural rind, 2) nodular pleural thickening, 3) pleural thickening of > 1 cm and 4) mediastinal pleural involvement. Involvement of a multidisciplinary team is recommended to ensure prompt and appropriate management, using a framework of radiotherapy, chemotherapy, surgery and symptom palliation with end of life care. Compensation issues must also be considered. Life expectancy in malignant mesothelioma is poor, with a median survival of about one year following diagnosis
From Architectured Materials to Large-Scale Additive Manufacturing
The classical material-by-design approach has been extensively perfected by materials scientists, while engineers have been optimising structures geometrically for centuries. The purpose of architectured materials is to build bridges across themicroscale ofmaterials and themacroscale of engineering structures, to put some geometry in the microstructure. This is a paradigm shift. Materials cannot be considered monolithic anymore. Any set of materials functions, even antagonistic ones, can be envisaged in the future. In this paper, we intend to demonstrate the pertinence of computation for developing architectured materials, and the not-so-incidental outcome which led us to developing large-scale additive manufacturing for architectural applications
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