8,818 research outputs found

    Understanding fragility in supercooled Lennard-Jones mixtures. I. Locally preferred structures

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    We reveal the existence of systematic variations of isobaric fragility in different supercooled Lennard-Jones binary mixtures by performing molecular dynamics simulations. The connection between fragility and local structures in the bulk is analyzed by means of a Voronoi construction. We find that clusters of particles belonging to locally preferred structures form slow, long-lived domains, whose spatial extension increases by decreasing temperature. As a general rule, a more rapid growth, upon supercooling, of such domains is associated to a more pronounced super-Arrhenius behavior, hence to a larger fragility.Comment: 14 pages, 14 figures, minor revisions, one figure adde

    Modeling of Euclidean braided fiber architectures to optimize composite properties

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    Three-dimensional braided fiber reinforcements are a very effective toughening mechanism for composite materials. The integral yarn path inherent to this fiber architecture allows for effective multidirectional dispersion of strain energy and negates delamination problems. In this paper a geometric model of Euclidean braid fiber architectures is presented. This information is used to determine the degree of geometric isotropy in the braids. This information, when combined with candidate material properties, can be used to quickly generate an estimate of the available load-carrying capacity of Euclidean braids at any arbitrary angle

    Delayed Graduation and Overeducation: A Test of the Human Capital Model Versus the Screening Hypothesis

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    The academic circles are devoting a growing interest to delayed graduation and overeducation, but none has analyzed the joint consequences of these two phenomena. Thus, this paper studies the link between graduation not within the minimum period and overeducation, and the effects of these variables on wages, using the ISFOL-Plus data. According to the human capital model, delayed graduation increases a student\u2019 human capital and should, therefore, reduce her probability of being overeducated, while increasing her wage. According to the screening hypothesis, instead, delayed graduation signals low skills and therefore increases the chances of being overeducated, while bearing a wage penalty. The evidence lines towards predictions based on the screening hypothesis. First, delayed graduation increases the chances of overeducation. In addition, the direct wage penalty associated to delayed graduation equals 7% of the median wage. However, being a determinant of overeducation, it also indirectly contributes to the penalty of 19.8% of the median wage associated to overeducation. These effects are sizeable, considering the very low returns to higher education in Italy reported in previous studies

    E-ABR in patients with cochlear implant: A comparison between patients with malformed cochlea and normal cochlea

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    OBJECTIVES: This study aims to compare the electrical auditory brainstem response (EABR) following cochlear implant (CI) surgery in pediatric subjects with cochlear malformation and a normal cochlea, in order to assess the sensitivity of EABR and to evaluate the surgery outcome. MATERIALS and METHODS: A total of 26 pediatric subjects who were deaf and scheduled for CI surgery were enrolled into this case control study. Group A (n=20) included subjects with a normo-conformed cochlea. Group B (n=6) included subjects with cochlear malformation. Subjects were evaluated with EABR immediately (T0) and 6 months (T1) post-CI surgery. The EABR Waves III and V average amplitude and latency were compared across time, separately for each group, and across groups, separately for each time. RESULTS: Auditory brainstem response (ABR) could only be recorded in Group A. We were able to record EABR from all subjects at T0 and T1, and waves III and V were present in all the recorded signals. There were no statistically significant differences between T0 and T1 in EABR Waves III and V in terms of average amplitude and latency in neither group. When comparing Groups A and B, the only statistically significant difference was the average amplitude of wave V, both at T0 and T1. CONCLUSION: EABR is a valid tool to measure the auditory nerve integrity after CI surgery in patients with a normal and malformed cochlea, as shown by its ability to measure waves III and V when ABR is absent. The EABR testing should be performed before and after CI surgery, and EABR should be used as a measure of outcome, especially in patients with a malformed cochlea

    Advanced radar absorbing ceramic-based materials for multifunctional applications in space environment

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    In this review, some results of the experimental activity carried out by the authors on advanced composite materials for space applications are reported. Composites are widely employed in the aerospace industry thanks to their lightweight and advanced thermo-mechanical and electrical properties. A critical issue to tackle using engineered materials for space activities is providing two or more specific functionalities by means of single items/components. In this scenario, carbon-based composites are believed to be ideal candidates for the forthcoming development of aerospace research and space missions, since a widespread variety of multi-functional structures are allowed by employing these materials. The research results described here suggest that hybrid ceramic/polymeric structures could be employed as spacecraft-specific subsystems in order to ensure extreme temperature withstanding and electromagnetic shielding behavior simultaneously. The morphological and thermo-mechanical analysis of carbon/carbon (C/C) three-dimensional (3D) shell prototypes is reported; then, the microwave characterization of multilayered carbon-filled micro-/nano-composite panels is described. Finally, the possibility of combining the C/C bulk with a carbon-reinforced skin in a synergic arrangement is discussed, with the aid of numerical and experimental analyses

    Overeducation at a glance. Determinants and wage effects of the educational mismatch, looking at the AlmaLaurea data

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    This paper provides the first available estimates of the impact of overeducation on wages of AlmaLaurea university graduates. The analysis focuses on jobs held 5 years after the graduation attained in 2005. Overeducation / overskilling are relatively high when compared to those in similarly advanced economies, and persistent over the years after graduation. Ceteris paribus they tend to be more frequent among children of parents with lower educational levels, through school tracking. The degrees more frequently associated to overeducation are: Agriculture, Arts, Education, Languages, Physical Education, Political Sciences and Psychology. Working while studying and having started the university later than the curricular years are also factors. Moreover, we estimate a conditional wage penalty of about 10% of the median wage when we adopt the “to get” (overeducation) and of about 6.7% when we adopt the “to do” (overskilling) definition. However, the personal attributes that dispose individuals to be mismatched might also reduce the probability of finding a job. Controlling for this source of sample selection bias by using the Heckit procedure, we find that the wage penalty associated to overeducation / overskilling goes up to 35 and 74 percent, respectively. This is support for the job competition and the job assignment models versus the search theoretical model, suggesting that the non-employed would be more likely overeducated / overskilled if they found a job

    Optimized random phase approximations for arbitrary reference systems: extremum conditions and thermodynamic consistence

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    The optimized random phase approximation (ORPA) for classical liquids is re-examined in the framework of the generating functional approach to the integral equations. We show that the two main variants of the approximation correspond to the addition of the same correction to two different first order approximations of the homogeneous liquid free energy. Furthermore, we show that it is possible to consistently use the ORPA with arbitrary reference systems described by continuous potentials and that the same approximation is equivalent to a particular extremum condition for the corresponding generating functional. Finally, it is possible to enforce the thermodynamic consistence between the thermal and the virial route to the equation of state by requiring the global extremum condition on the generating functional.Comment: 8 pages, RevTe
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