Analysis of damage and fracture formulations in cold extrusion

In forming processes, components generally undergo large deformations. This induces the evolution of damage, which can influence material and product properties. To capture these effects, a continuum damage mechanics (CDM) model, based on the work of Lemaitre [8] and Soyarslan [13, 14] as well as different fracture criteria according to Cockcroft and Latham [2], Freudenthal [4] and Oyane [10] are implemented and in- vestigated. While the CDM theory considers the evolution of damage and the associated softening, fracture criteria do not affect the results of the mechanical finite element (FE) analysis. However, a coupling is generally possible via element deletion, but material softening cannot be depicted in the simulation. Tensile tests with notched specimens are performed in order to obtain the material parameters associated with these models by inverse parameter identification processes. The optimized set of parameters is finally ap- plied to the damage and fracture models used for the FE simulations of a cold extrusion process, which are investigated in terms of damage evolution and material failure. It is demonstrated that the CDM model predicts the evolution of damage observed for differ- ent process parameters in cold extrusion quantitatively. The prediction of the failure by the fracture criteria does not agree well with the experiments

Decentralized Routing on Spatial Networks with Stochastic Edge Weights

We investigate algorithms to find short paths in spatial networks with stochastic edge weights. Our formulation of the problem of finding short paths differs from traditional formulations because we specifically do not make two of the usual simplifying assumptions: (1) we allow edge weights to be stochastic rather than deterministic; and (2) we do not assume that global knowledge of a network is available. We develop a decentralized routing algorithm that provides en route guidance for travelers on a spatial network with stochastic edge weights without the need to rely on global knowledge about the network. To guide a traveler, our algorithm uses an estimation function that evaluates cumulative arrival probability distributions based on distances between pairs of nodes. The estimation function carries a notion of proximity between nodes and thereby enables routing without global knowledge. In testing our decentralized algorithm, we define a criterion that allows one to discriminate among arrival probability distributions, and we test our algorithm and this criterion using both synthetic and real networks.Comment: 10 pages, 9 figures (some with multiple parts

Beta event-related desynchronization as an index of individual differences in processing human facial expression: further investigations of autistic traits in typically developing adults

The human mirror neuron system (hMNS) has been associated with various forms of social cognition and affective processing including vicarious experience. It has also been proposed that a faulty hMNS may underlie some of the deficits seen in the autism spectrum disorders (ASDs). In the present study we set out to investigate whether emotional facial expressions could modulate a putative EEG index of hMNS activation (mu suppression) and if so, would this differ according to the individual level of autistic traits [high versus low Autism Spectrum Quotient (AQ) score]. Participants were presented with 3 s films of actors opening and closing their hands (classic hMNS mu-suppression protocol) while simultaneously wearing happy, angry, or neutral expressions. Mu-suppression was measured in the alpha and low beta bands. The low AQ group displayed greater low beta event-related desynchronization (ERD) to both angry and neutral expressions. The high AQ group displayed greater low beta ERD to angry than to happy expressions. There was also significantly more low beta ERD to happy faces for the low than for the high AQ group. In conclusion, an interesting interaction between AQ group and emotional expression revealed that hMNS activation can be modulated by emotional facial expressions and that this is differentiated according to individual differences in the level of autistic traits. The EEG index of hMNS activation (mu suppression) seems to be a sensitive measure of the variability in facial processing in typically developing individuals with high and low self-reported traits of autism

Ab initio Modelling of the Early Stages of Precipitation in Al-6000 Alloys

Age hardening induced by the formation of (semi)-coherent precipitate phases is crucial for the processing and final properties of the widely used Al-6000 alloys. Early stages of precipitation are particularly important from the fundamental and technological side, but are still far from being fully understood. Here, an analysis of the energetics of nanometric precipitates of the meta-stable $\beta''$ phases is performed, identifying the bulk, elastic strain and interface energies that contribute to the stability of a nucleating cluster. Results show that needle-shape precipitates are unstable to growth even at the smallest size $\beta''$ formula unit, i.e. there is no energy barrier to growth. The small differences between different compositions points toward the need for the study of possible precipitate/matrix interface reconstruction. A classical semi-quantitative nucleation theory approach including elastic strain energy captures the trends in precipitate energy versus size and composition. This validates the use of mesoscale models to assess stability and interactions of precipitates. Studies of smaller 3d clusters also show stability relative to the solid solution state, indicating that the early stages of precipitation may be diffusion-limited. Overall, these results demonstrate the important interplay among composition-dependent bulk, interface, and elastic strain energies in determining nanoscale precipitate stability and growth

The metabolic syndrome – What is the value of its identification?

The identification of the metabolic syndrome (MS) has been under discussion and intense investigation since 1998. Only recently does it appear that consensus is being reached between different organisations regarding its identification. Nonetheless, the true value in identifying the MS remains under question, as does the debate around its existence. The real value in identifying the MS may simply be the ability to identify individuals at increased risk for developing cardiovascular disease (CVD) and diabetes. Further identification of abnormalities associated with the MS should encourage practitioners to investigate and search for other risk factors associated with CVD and diabetes. Part of the problem in identifying and treating the MS is that the cause of associated abnormalities remains unclear. However current research seems to indicate that oxidative stress and inflammation may play a pivotal role in the development of insulin resistance (IR) and the MS. Regardless of the usefulness of indentifying the MS and its contributing causes, certain take home messages for practitioners remain the same, including emphasis on the importance of weight loss in overweight patients, the role of regular exercise and diet quality, with a new emphasis on the role of an adequate micronutrient intake and specifically nutrients with antioxidant properties.

The effects of postactivation potentiation on sprint and jump performance of male academy soccer players.

The purpose of this investigation was to evaluate the postactivation potentiation (PAP) effects of both dynamic and isometric maximum voluntary contractions (MVCs) on sprint and jump performance and establish whether PAP methods could be used effectively in warm up protocols for soccer players. Twelve male soccer players performed 4 warm up protocols in a cross-over, randomized, and counterbalanced design. In addition to a control warm up, subjects performed deadlift (5 repetitions at 5 repetitions maximum), tuck jump (5 repetitions), and isometric MVC knee extensions (3 repetitions for 3 s) as PAP treatments in an otherwise identical warm up protocol. After each treatment, the subjects underwent 3 10 m and 20 m sprints 4, 5, and 6 minutes post-warm up and 3 vertical jumps (VJ) at 7, 8, and 9 minutes post-warm up. Repeated measures analysis of variance showed no significant differences in the first 10 m (p = 0.258) and 20 m (p = 0.253) sprint and VJ (p = 0.703) performance and the average 10 m (p = 0.215), 20 m (p = 0.388), and VJ (p = 0.529) performance between conditions. There were also no significant differences in performance responses between the strongest and weakest subjects, but large variations in individual responses were found between the subjects. The findings suggest that there was no significant group PAP effect on sprint and jump performance after dynamic and isometric MVCs compared with a control warm up protocol. However, the large variation in individual responses (-7.1% to +8.2%) suggests PAP should be considered on an individual basis. Factors such as method, volume, load, recovery, and interindividual variability of PAP must be considered in the practical application of PAP and the rigorous research design of future studies to evaluate the potential for performance enhancement

Boosting Reading Scores by Adding in Technology Based Interventions

The purpose of this action research project was to determine if adding a technology based literacy apps in a general education second grade classroom could increase the reading scores of the Informal Decoding Inventory that was given to second grade students, throughout a four month period to check personal growth. It will also look at other reading assessments in reading throughout the time frame, but for the purpose and time of this project the researcher will strictly be looking at growth through the inventory. Technology enriched phonemic awareness with a focus on decoding words, recognizing word patterns and fluency interventions and apps were provided weekly over a period of two months. Data was collected through qualitative observations and quantitative Decoding Inventory scores. Analysis of the data collected suggests that second grade student’s word decoding scores increased when students were introduced to technology based interventions