On a multiscale strategy and its optimization for the simulation of combined delamination and buckling

This paper investigates a computational strategy for studying the interactions between multiple through-the-width delaminations and global or local buckling in composite laminates taking into account possible contact between the delaminated surfaces. In order to achieve an accurate prediction of the quasi-static response, a very refined discretization of the structure is required, leading to the resolution of very large and highly nonlinear numerical problems. In this paper, a nonlinear finite element formulation along with a parallel iterative scheme based on a multiscale domain decomposition are used for the computation of 3D mesoscale models. Previous works by the authors already dealt with the simulation of multiscale delamination assuming small perturbations. This paper presents the formulation used to include geometric nonlinearities into this existing multiscale framework and discusses the adaptations that need to be made to the iterative process in order to ensure the rapid convergence and the scalability of the method in the presence of buckling and delamination. These various adaptations are illustrated by simulations involving large numbers of DOFs

Why do Gull-billed Terns Gelochelidon nilotica feed on fiddler crabs Uca tangeri in Guinea-Bissau?

Gull-billed Terns Gelochelidon nilotica wintering in Guinea Bissau mainly fed on fiddler crabs Uca tangeri and were occasionally seen feeding on fish and locusts. As fiddler crabs have a low energy content, terns need a large gross intake to meet daily energy demands. Fiddler crabs also have a low ratio of digestible flesh to exoskeleton, and therefore tern food intake may be limited by gut capacity. Activity budgets of Gullbilled Terns feeding on fiddler crabs showed that a considerable part of the time was spent resting. The duration of resting intervals increased with energy intake and was positively correlated with the metabolisable energy content of the crab eaten, suggesting that resting periods were required for a proper digestion. The poor quality of fiddler crabs was offset by high capture rates. So daily energy expenditure of the terns could easily be met by feeding on fiddler crabs. Even when resting pauses were included in foraging time, foraging for only 1.5 hours on fiddler crabs satisfied the terns&rsquo; daily energy demands. Instead, feeding on energy-rich fish would require about 2.5 hours to satisfy daily energy demands. Compared to the more specialised piscivorous Little Tern Sternula albifrons and Sandwich Tern Sterna sandvicensis, capture rate of fish was poor in Gull-billed Terns. From an energetic point of view, wintering Gull-billed Terns feeding on fiddler crabs seem to have an easy living in Guinea Bissau.<br /

Virtual Delamination Testing through Non-Linear Multi-Scale Computational Methods: Some Recent Progress

This paper deals with the parallel simulation of delamination problems at the meso-scale by means of multi-scale methods, the aim being the Virtual Delamination Testing of Composite parts. In the non-linear context, Domain Decomposition Methods are mainly used as a solver for the tangent problem to be solved at each iteration of a Newton-Raphson algorithm. In case of strongly nonlinear and heterogeneous problems, this procedure may lead to severe difficulties. The paper focuses on methods to circumvent these problems, which can now be expressed using a relatively general framework, even though the different ingredients of the strategy have emerged separately. We rely here on the micro-macro framework proposed in (Ladev\`eze, Loiseau, and Dureisseix, 2001). The method proposed in this paper introduces three additional features: (i) the adaptation of the macro-basis to situations where classical homogenization does not provide a good preconditioner, (ii) the use of non-linear relocalization to decrease the number of global problems to be solved in the case of unevenly distributed non-linearities, (iii) the adaptation of the approximation of the local Schur complement which governs the convergence of the proposed iterative technique. Computations of delamination and delamination-buckling interaction with contact on potentially large delaminated areas are used to illustrate those aspects

Identifying and Avoiding Survey Nonresponse and Noncompliance

In the last five years, researchers have seen a notable increase in difficulty of collecting valid and useful survey data. Respondents, likely attracted to the prospect of receiving prizes or other compensation after survey completion, submit survey responses that are irrelevant to the questions asked, relevant but unusable due to the respondent not identifying as a member of the target population, or comprised of nonsense (such as paragraphs of lorem ipsum text or copy-pasted from other sources). As a result of experiencing a high volume of invalid survey responses to a qualitative survey aiming to research identity narrative formation among Irish women, this project highlights the forms in which invalid survey responses appear and analyzes the ways in which this might be avoided. Previous research has suggested the use of internet protocol (IP) address analysis and attention checks to prevent survey nonresponse as well as responses from non-target populations and invalid responses. For this project, tactics such as attention checks, skip logic, CAPTCHA, and highly specific population-relevant questions were experimented with to lessen invalid responses from both human respondents and bots, as well as to lessen the amount of data cleaning needed to find relevance in responses. Analysis of these methods and a conclusion of suggested best practices to avoid survey nonresponse and noncompliance are offered for future surveying

In-Vivo Bytecode Instrumentation for Improving Privacy on Android Smartphones in Uncertain Environments

In this paper we claim that an efficient and readily applicable means to improve privacy of Android applications is: 1) to perform runtime monitoring by instrumenting the application bytecode and 2) in-vivo, i.e. directly on the smartphone. We present a tool chain to do this and present experimental results showing that this tool chain can run on smartphones in a reasonable amount of time and with a realistic effort. Our findings also identify challenges to be addressed before running powerful runtime monitoring and instrumentations directly on smartphones. We implemented two use-cases leveraging the tool chain: BetterPermissions, a fine-grained user centric permission policy system and AdRemover an advertisement remover. Both prototypes improve the privacy of Android systems thanks to in-vivo bytecode instrumentation.Comment: ISBN: 978-2-87971-111-

Forensic Identification of Condom Lubricants by Advanced Statistical Analysis Processing of Direct Analysis in Real Time Mass Spectrometric Data – Towards Development of a Condom Residue Database for Forensic Science Practitioners

The ability to identify condom derived trace evidence is gaining importance because of the increasing frequency with which perpetrators of sexual assault use condoms in order to avoid leaving behind incriminating DNA evidence that might link them to the crime. Although DNA remains the gold standard for sexual assault evidence, other forms of trace evidence are needed in its absence. When condoms are used, the lubricants associated with them are the trace evidence. For the lubricant residue to be useful in a forensics context, a database of chemical signatures of lubricants against which acquired evidence can be screened is required, so that condom brands and types can be identified from the trace evidence. Towards the goal of developing such a database, this study used direct analysis in real time-high resolution mass spectrometry (DART-HRMS) to analyze 110 different types of condoms representing 16 brands. Over 700 spectra were acquired, each serving as a chemical fingerprint for the analyzed condom. The results showed that condoms of the same type within different brands exhibited the same chemical signatures, which differed from condoms of other brands, even when the condoms were advertised to have the same characteristics. For example, the mint flavored condoms of different brands had distinct diagnostic chemical signatures that allowed them to be distinguished from one another, even though they all contained the same chemical components that conferred the mint flavor. Both supervised and unsupervised multivariate statistical analyses were performed on the data. Hierarchical clustering analysis (unsupervised) showed that condoms could be differentiated by brand. Kernel discriminant analysis (supervised) showed that condoms within a given brand could be distinguished. The observed leave-one-out cross validation was 90-100% depending upon the brand. This indicates that a strong database has been developed with the capability of serving as a presumptive test that can be used not only to identify brands, but also the particular condom type within a brand. This database can be readily expanded as additional condom types emerge, and may be particularly useful for corroborating the accounts of victims, or exonerating the falsely accused in cases where DNA evidence is lacking. The positive brand identification of unknown condom residues implies that the database could serve as a tool to assist forensic science practitioners in prosecuting sexual assault cases

Damage mechanics of interfacial media: Basic aspects, identification and application to delamination

International audienceThis chapter presents the development of a model to bridge between damage mechanics and delamination by including all the damage mechanisms in delamination analysis. For this, a damage meso-modeling that includes both inner layer damage mechanisms and interracial ones is used. Delamination often appears as the result of interactions among different damage mechanisms, such as fiber-breaking, transverse microcracking, and debonding of the adjacent layers themselves. At the meso-level, the laminate is described as a stacking sequence of inelastic and damageable homogeneous layers throughout the thickness and of damageable interlaminar interfaces. One limitation of the meso-modeling is that the fracture of the material is described by means of only two types of macrocracks: (1) delamination cracks within the interfaces and (2) cracks, orthogonal to the laminate, with each cracked layer being completely cracked in its thickness. The ideas and framework that govern the interface damage modeling are similar to those which are used for deriving the layer damage modeling

Quoi de neuf dans les hypophysites ?

Hypophysitis is a rare disorder. As clinical manifestations and radiologic signs are non specific, the diagnosis is difficult. Pathogenesis of hypophysitis remains largely unknown but new histological and etiological variants have been recently reported. Primary hypophysitis is the main form. For the first time, hypophysitis in ANCA-associated vasculitides has been reported. An entity of IgG4 related plasmatic hypophysitis has been described and well-defined diagnostic criteria have been proposed. Monoclonal antibodies directed against the cytotoxic T-lymphocyte antigen-4 (CTLA-4), investigated in metastatic cancer, can induce hypophysitis. Several candidate pituitary auto-antigens have been described in the last decade, although none has proven to be useful as a diagnostic tool