433 research outputs found
Neural networks for fatigue crack propagation predictions in real-time under uncertainty
Crack propagation analyses are fundamental for all mechanical structures for which safety must be guaranteed, e. g. as for the aviation and aerospace fields. The estimation of life for structures in presence of defects is a process inevitably affected by numerous and unavoidable uncertainty and variability sources, whose effects need to be quantified to avoid unexpected failures or excessive conservativism.
In this work, residual fatigue life prediction models have been created through neural networks for the purpose of performing probabilistic life predictions of damaged structures in real-time and under stochastically varying input parameters. In detail, five different neural network architectures have been compared in terms of accuracy, computational runtimes and minimum number of samples needed for training, so to determine the ideal architecture with the strongest generalization power. The networks have been trained, validated and tested by using the fatigue life predictions computed by means of simulations developed with FEM and Monte Carlo methods. A real-world case study has been presented to show how the proposed approach can deliver accurate life predictions even when input data are uncertain and highly variable.
Results demonstrated that the “H1-L1” neural network has been the best model, achieving an accuracy (Mean Square Error) of 4.8e-7 on the test dataset, and the best and the most stable results when decreasing the amount of data. Additionally, since requiring only very few parameters, its potential applicability for Structural Health Monitoring purposes in small cost-effective GPU devices resulted to be attractive
Molecular identification of Contracaecum rudolphii A and B (Nematoda: Anisakidae) from cormorants collected in a freshwater ecosystem of the pre-alpine area in Northern Italy
Contracaecum rudolphii (s.l.) is a complex of sibling species with different genetic structure and ecological preference. This study reports the presence of specimens of Contracaecum rudolphii (s.l.) from sedentary and wintering cormorants (Phalacrocorax carbo sinensis) from the pre-mountain area of the Alps in Northern Italy, an important crossroads for most of the bird migration routes. A total of 48 specimens of cormorants collected from two adjacent freshwater habitats were analysed and C. rudolphii nematodes were retrieved in 100% of the examined specimens. A subsamples of 115 C. rudolphii individuals were genetically characterized and found to belong to the sibling species C. rudolphii B (n = 90) and C. rudolphii A (n = 25). C. rudolphii B were retrieved from both locations and included adults as well as larvae, while only adults of C. rudolphii A were detected, and in just one location. As expected for a freshwater environment, C. rudolphii B constitutes the largest sibling fraction, indicating that this likely is the endemic species, while cormorants originating from the breeding brackish lagoons and marine coastal environments of central and northern Europe could have brought C. rudolphii A from their breeding sites or migration stopovers
Profile of Trypanosoma cruzi Infection in a Tropical Medicine Reference Center, Northern Italy
Chagas disease (CD) is endemic in Central and South America, Mexico and even in some areas of the United States. However, cases have been increasingly recorded also in non-endemic countries. The estimated number of infected people in Europe is in a wide range of 14000 to 181000 subjects, mostly resident in Spain, Italy and the United Kingdom
The Framingham cardiovascular risk score in multiple sclerosis
Background and purpose: Cardiovascular risk factors can increase the risk of multiple sclerosis (MS) and modify its course. However, such factors possibly interact, determining a global cardiovascular risk. Our aim was to compare the global cardiovascular risk of subjects with and without MS with the simplified 10-year Framingham General Cardiovascular Disease Risk Score (FR) and to evaluate its importance on MS-related outcomes. Methods: Age, gender, smoking status, body mass index, systolic blood pressure, type II diabetes and use of antihypertensive medications were recorded in subjects with and without MS to estimate the FR, an individualized percentage risk score estimating the 10-year likelihood of cardiovascular events. Results: In total, 265 MS subjects were identified with 530 matched controls. A t test showed similar FR in cases and controls (P = 0.212). Secondary progressive MS presented significantly higher FR compared to relapsing-remitting MS (P < 0.001). Linear regression analysis showed a direct relationship between FR and Expanded Disability Status Scale (P < 0.001) and MS Severity Scale (P < 0.001). Conclusion: The FR, evaluating the global cardiovascular health by the interaction amongst different risk factors, relates to MS disability, severity and course
First-order phase transition vs. spin-state quantum-critical scenarios in strain-tuned epitaxial cobaltite thin films
Pr-containing perovskite cobaltites exhibit unusual valence transitions,
coupled to coincident structural, spin-state, and metal-insulator transitions.
Heteroepitaxial strain was recently used to control these phenomena in the
model (PrY)CaCoO system, stabilizing a
nonmagnetic insulating phase under compression (with a room-temperature
valence/spin-state/metal-insulator transition) and a ferromagnetic metallic
phase under tension, thus exposing a potential spin-state quantum critical
point. The latter has been proposed in cobaltites and can be probed in this
system as a function of a disorder-free variable (strain). We study this here
via thickness-dependent strain relaxation in compressive
SrLaAlO(001)/(PrY)CaCoO
epitaxial thin films to quasi-continuously probe structural, electronic, and
magnetic behaviors across the nonmagnetic-insulator/ferromagnetic-metal
boundary. High-resolution X-ray diffraction, electronic transport,
magnetometry, polarized neutron reflectometry, and temperature-dependent
magnetic force microscopy provide a detailed picture, including abundant
evidence of temperature- and strain-dependent phase coexistence. This indicates
a first-order phase transition as opposed to spin-state quantum-critical
behavior, which we discuss theoretically via a phenomenological Landau model
for coupled spin-state and magnetic phase transitions.Comment: main text + supplementary materia
Inequalities in higher education in low‐ and middle‐income countries:A scoping review of the literature
Motivation: Higher education is regarded as a key instrument to enhance socioeconomic mobility andreduce inequalities. Recent literature reviews have examined inequalities in the higher education systemsof high-income countries, but less is known about the situation in low- and middle-income countries,where higher education is expanding fast.Purpose: The article reviews the academic literature on higher education in low- and middle-incomecountries using a research framework inspired by social justice and capability approaches. It considers the financial, socio-cultural, human, and political resource domains on which people draw, and how they relate to access, participation, and outcomes in higher education.Methods: A literature search for studies explicitly discussing in-country inequalities in higher education revealed 22 publications. Substantial knowledge gaps remain, especially regarding the political (and decision-making) side of inequalities; the ideologies and philosophies underpinning higher education systems; and the linkages between resource domains, both micro and macro.Findings: The review highlights key elements for policy-makers and researchers: (1) the financial lens alone is insufficient to understand and tackle inequalities, since these are also shaped by human and other non-financial factors; (2) socio-cultural constructs are central in explaining unequal outcomes; and (3) inequalities develop throughout one’s life and need to be considered during, but also before and afterhigher education. The scope of inequalities is wide, and the literature offers a few ideas for short-term fixes such as part-time and online education.Policy implications: Inclusive policy frameworks for higher education should include explicit goals related to (in)equality, which are best measured in terms of the extent to which certain actions or choices are feasible for all. Policies in these frameworks, we argue, should go beyond providing financial support, and also address socio-cultural and human resource constraints and challenges in retention, performance, and labour market outcomes. Finally, they should consider relevant contextual determinants of inequalities.</p
Search for Gravitational Waves Associated with 39 Gamma-Ray Bursts Using Data from the Second, Third, and Fourth LIGO Runs
We present the results of a search for short-duration gravitational-wave
bursts associated with 39 gamma-ray bursts (GRBs) detected by gamma-ray
satellite experiments during LIGO's S2, S3, and S4 science runs. The search
involves calculating the crosscorrelation between two interferometer data
streams surrounding the GRB trigger time. We search for associated
gravitational radiation from single GRBs, and also apply statistical tests to
search for a gravitational-wave signature associated with the whole sample. For
the sample examined, we find no evidence for the association of gravitational
radiation with GRBs, either on a single-GRB basis or on a statistical basis.
Simulating gravitational-wave bursts with sine-gaussian waveforms, we set upper
limits on the root-sum-square of the gravitational-wave strain amplitude of
such waveforms at the times of the GRB triggers. We also demonstrate how a
sample of several GRBs can be used collectively to set constraints on
population models. The small number of GRBs and the significant change in
sensitivity of the detectors over the three runs, however, limits the
usefulness of a population study for the S2, S3, and S4 runs. Finally, we
discuss prospects for the search sensitivity for the ongoing S5 run, and beyond
for the next generation of detectors.Comment: 24 pages, 10 figures, 14 tables; minor changes to text and Fig. 2;
accepted by Phys. Rev.
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