659 research outputs found
A difference-equation formalism for the nodal domains of separable billiards
No full textRecently, the nodal domain counts of planar, integrable billiards with Dirichlet boundary conditions were shown to satisfy certain difference equations in Samajdar and Jain (2014). The exact solutions of these equations give the number of domains explicitly. For complete generality, we demonstrate this novel formulation for three additional separable systems and thus extend the statement to all integrable billiards. (C) 2016 Elsevier Inc. All rights reserved
Strain localizations in ultra low carbon steel
No full textUltra low carbon (ULC) steel samples were deformed in near plane-strain compression mode with different strains, strain rates and temperatures. Different aspects of microstructural developments, for deformed gamma (ND//) and theta (ND//) fibre grains, were investigated using X-ray line profiles and high resolution electron diffraction. The study clearly showed increase in grain interior strain localizations and in-grain misorientation at the intermediate deformation temperature. This effect was more apparent in gamma-fibre and can best be explained through orientation sensitive recovery. gamma-fibre also demonstrated higher potential for increase in dislocation density. This was observed experimentally and simulated through discrete dislocation dynamic simulations. Higher textural softening with stronger increase in dislocation density and possible effects of orientation sensitive recovery appears to define the orientation dependent recovery in low carbon steels
Constraints on the binary black hole nature of GW151226 and GW170608 from the measurement of spin-induced quadrupole moments
No full textAccording to the "no-hair" conjecture, a Kerr black hole (BH) is completely described by its mass and spin. In particular, the spin-induced quadrupole moment of a Kerr BH with mass and dimensionless spin can be written as , where . Thus by measuring the spin-induced quadrupole parameter , we can test the binary black hole nature of compact binaries and distinguish them from binaries comprised of other exotic compact objects, as proposed in [N. V. Krishnendu et al., PRL 119, 091101 (2017)]. Here, we present a Bayesian framework to carry out this test where we measure the symmetric combination of individual spin-induced quadrupole moment parameters fixing the anti-symmetric combination to be zero. The analysis is restricted to the inspiral part of the signal as the spin-induced deformations are not modeled in the post-inspiral regime. We perform detailed simulations to investigate the applicability of this method for compact binaries of different masses and spins and also explore various degeneracies in the parameter space which can affect this test. We then apply this method to the gravitational wave events, GW151226 and GW170608 detected during the first and second observing runs of Advanced LIGO and Advanced Virgo detectors. We find the two events to be consistent with binary black hole mergers in general relativity. By combining information from several more of such events in future, this method can be used to set constraints on the black hole nature of the population of compact binaries that are detected by the Advanced LIGO and Advanced Virgo detectors
Comparing gravitational waveform models for binary black hole mergers through a hypermodels approach
No full textThe inference of source parameters from gravitational-wave signals relies on theoretical models that describe the emitted waveform. Different model assumptions on which the computation of these models is based could lead to biases in the analysis of gravitational-wave data. In this work, we sample directly on four state-of-the-art binary black hole waveform models from different families, in order to investigate these systematic biases from the 13 heaviest gravitational-wave sources with moderate to high signal-to-noise ratios in the third Gravitational-Wave Transient Catalog (GWTC- 3). All models include spin-precession as well as higher-order modes. Using the "hypermodels" technique, we treat the waveform models as one of the sampled parameters, therefore directly getting the odds ratio of one waveform model over another from a single parameter estimation run. From the joint odds ratio over all 13 sources, we find the model NRSur7dq4 to be favoured over SEOBNRv4PHM, with an odds ratio of 29.43; IMRPhenomXPHM and IMRPhenomTPHM have an odds ratio, respectively, of 4.70 and 5.09 over SEOBNRv4PHM. However, this result is mainly determined by three events that show a strong preference for some of the models and that are all affected by possible data quality issues. If we do not consider these potentially problematic events, the odds ratio do not exhibit a significant preference for any of the models. Although further work studying a larger set of signals will be needed for robust quantitative results, the presented method highlights one possible avenue for future waveform model development
Crystallographic texture as a factor enabling ductile fracture arrest in high strength pipeline steel
No full textLow ductile crack arrestability in a full-scale burst test of 1420 mm-diameter X80 steel line pipes was accompanied by a high intensity of fracture surface separation. The texture of the steel plates was studied using different techniques in order to evaluate the influence of {001} planes oriented parallel to the rolling plane on the separation intensity during fracture. Though no clear correlation between the content of {001} planes parallel to the rolling plane and intensity of separation was found, the local distribution of the {001} texture component among the microstructure components was different in different steels providing long areas suitable for cleavage fracture parallel to the rolling plane in steel with low arrestability
Characterization and modeling of twinning in a titanium alloy Ti-6Al-4V
No full textThe twinning behavior of a commercial Ti-6Al-4V alloy is studied using a combined experimental and numerical approach. An extensive microstructural investigation was performed to identify and quantify the active twin systems. The mechanical behavior as a function of initial texture and strain rate was then modeled using a visco-plastic self-consistent crystal plasticity code (VPSC7). Earlier obtained quasi-static and dynamic data served to fit the parameters of the model, giving good agreement. However, even if the model gave qualitatively good predictions of the stress-strain curves and the texture evolution for the different loadings, the calculated twin fractions differed considerably of the experimental results.status: Publishe
Mesoscopic EBSD analysis and mesomechanical behavior of ridging or roping in AA6XXX alloys
No full textAluminium alloys for car body manufacturing often show a specific type of band-shaped surface roughening upon stretching, called "ridging" or "roping". Experimental researches as well as modelling attempts have indicated that the evolving surface roughness profiles cannot be understood as being merely caused by banding of individual surface texture components, like cube or Goss. Therefore, it is proposed to study banding on the "mesoscopic" scale of texture banding rather than on the "microscopic" scale of orientation banding. In mechanical terms, such patterning in the texture would lead to patterning in, for instance, the Lankford coefficient (r-value), so that the mechanical response can be calculated on an intermediate length scale. The present contribution presents a method for calculating r-value patterning from Electron Backscatter diffraction (EBSD) orientation maps. In a first test case of a strongly ridging AA6xxx sheet, indeed patterning in the r-value is found which corresponds to reported patterning of the surface roughness
Availability of different branded generic vildagliptin after off-patenting: An observation from India
No full textBackground: Branded generics offer comparable therapeutic benefits at a lower cost, making them essential in healthcare systems worldwide. Vildagliptin, a widely prescribed antidiabetic medication, is available in various branded generic forms. However, limited research has been conducted to assess the availability of these branded generics, particularly in a real-world setting. Methods: A cross-sectional observational study evaluated the availability of branded generics of vildagliptin over 3-month period post 6 months of off-patenting of vildagliptin. Additionally, the switching patterns among patients prescribed branded generic vildagliptin were investigated, shedding light on potential challenges and implications for patient care. Results: Each prescription for branded generic vildagliptin resulted in an average of 2.29 pharmacy visits, highlighting potential challenges in ensuring consistent availability of specific branded generics. Reflecting on switching patterns, due to the unavailability of the prescribed branded generic vildagliptin at the pharmacy store, 28% of patients switched to the innovator brand, 41% switched to other branded generics, and only 31% received the prescribed branded generic. These switching patterns suggest a significant proportion of patients who deviate from the initially prescribed branded generic, potentially impacting treatment adherence and outcomes. Conclusion: Strategies aimed at improving availability and promoting appropriate use of branded generics can enhance the overall quality of care for patients requiring vildagliptin treatment. Further research and interventions should be undertaken to improve coordination between healthcare providers, pharmaceutical companies, and pharmacy stores, aiming to enhance the availability and accessibility of affordable generics without compromising patient care
Yield strength anisotropy of steel sheet induced by grain shape and crystal anisotropy
No full textIn crystal plasticity models the crystal anisotropy of the yield strength is accounted for by the yield locus. In the present paper the full constraint Taylor model is used to calculate the yield strength anisotropy of a heavily cold rolled and annealed IF steel. In addition to the crystallographically induced anisotropy also the grain shape anisotropy was taken into account. To this purpose a model is presented in which the grain size that appears in the Hall-Petch relation is substituted by an effective grain size that is dependent of the grain-shape morphology and the crystal orientation. The grain shape of a specific crystal orientation is approximated by an ellipsoid volume of which the major axes are obtained from experimental data. The effective grain size of a specific crystal orientation is determined by the intersection of the most active crystal slip plane of this orientation and the ellipsoid volume
In-situ texture measurements by synchrotron radiation of TRIP steel during an austempering treatment
No full textTexture formation during an austempering treatment of a TRIP-assisted steel was studied by in-situ texture measurements with a high energy source (synchrotron). Samples from a cold rolled sheet were subjected to a complete heat treatment cycle for TRIP steels including reheating to the intercritical (alpha+gamma) temperature region, isothermal soaking and bainitic holding (austempering) at 400 degrees C for 600s. At specific points of the thermal cycle {200}(gamma), {220}(gamma) {222}(gamma), {331}(gamma) and {200}(alpha), {211}(alpha) and {220}(alpha) Debye rings were recorded and the corresponding incomplete pole figures were calculated. The latter were used to derive the orientation distribution functions (ODFs) of BCC and FCC phases at specific steps of the annealing process after assuming the orthotropic sample symmetry. The acquired data for the texture evolution during the alpha-gamma-alpha phase transformation showed that during the reheating for intercritical annealing the gamma phase with {011} orientation is among the first to nucleate from the recrystallized alpha phase during heating and the Goss and Cube orientations are among the principal gamma phase components which transform to BCC phase after cooling
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