37 research outputs found
Clustering measure-valued data with Wasserstein barycenters
In this work, learning schemes for measure-valued data are proposed, i.e.
data that their structure can be more efficiently represented as probability
measures instead of points on , employing the concept of probability
barycenters as defined with respect to the Wasserstein metric. Such type of
learning approaches are highly appreciated in many fields where the
observational/experimental error is significant (e.g. astronomy, biology,
remote sensing, etc.) or the data nature is more complex and the traditional
learning algorithms are not applicable or effective to treat them (e.g. network
data, interval data, high frequency records, matrix data, etc.). Under this
perspective, each observation is identified by an appropriate probability
measure and the proposed statistical learning schemes rely on discrimination
criteria that utilize the geometric structure of the space of probability
measures through core techniques from the optimal transport theory. The
discussed approaches are implemented in two real world applications: (a)
clustering eurozone countries according to their observed government bond yield
curves and (b) classifying the areas of a satellite image to certain land uses
categories which is a standard task in remote sensing. In both case studies the
results are particularly interesting and meaningful while the accuracy obtained
is high.Comment: 18 pages, 3 figure
Contingent claim pricing through a continuous time variational bargaining scheme
We consider a variational problem modelling the evolution with time of two
probability measures representing the subjective beliefs of a couple of agents engaged in
a continuous-time bargaining pricing scheme with the goal of finding a unique price for a
contingent claim in a continuous-time financialmarket. This optimization problem is coupled
with two finite dimensional portfolio optimization problems, one for each agent involved in
the bargaining scheme. Undermild conditions, we prove that the optimization problem under
consideration here admits a unique solution, yielding a unique price for the contingent claim.info:eu-repo/semantics/publishedVersio
Microtomographic Analysis of Impact Damage in FRP Composite Laminates: A Comparative Study
With the advancement of testing tools, the ability to characterize mechanical properties of fiber reinforced polymer (FRP) composites under extreme loading scenarios has allowed designers to use these materials in high-level applications more confidently. Conventionally, impact characterization of composite materials is studied via nondestructive techniques such as ultrasonic C-scanning, infrared thermography, X-ray, and acoustography. None of these techniques, however, enable 3D microscale visualization of the damage at different layers of composite laminates. In this paper, a 3D microtomographic technique has been employed to visualize and compare impact damage modes in a set of thermoplastic laminates. The test samples were made of commingled polypropylene (PP) and glass fibers with two different architectures, including the plain woven and unidirectional. Impact testing using a drop-weight tower, followed by postimpact four-point flexural testing and nondestructive tomographic analysis demonstrated a close relationship between the type of fibre architecture and the induced impact damage mechanisms and their extensions
Natural Aging Behaviour Of AA6111 Aluminium
In the continuing drive for weight reduction in new automobile designs, the 6000 series aluminium alloys have emerged as the most promising age-hardenable body sheet material in the automotive industry. Currently, one of the body sheet alloys used for its
combination of strength and formability in the (T4) temper is AA6111, an Al-Mg-Si-Cu alloy. The T4 behaviour of AA6111 has been investigated by means of tensile testing, microhardness measurements, differential scanning calorimetry (DSC), scanning
electron microscopy (SEM), and X-ray analysis. The results show that AA6111 attains a monotonic strength after approximately 120 h of natural aging. The microstructure consists of an aluminium matrix and angular intermetallic particles containing mainly Al, Fe, Cu, Si and Mn dispersed within the microstructure. The intermetallic particles are found
to possess a structural formula of the type AlxFeSi. Compared with other 6xxx series of alloys under the same T4 condition, AA6111 shows superior strength properties. Natural aging is observed to affect the kinetic reaction of AA6111.Dans la
campagne continue pour la réduction en poids dans le nouveau modèle d\' automobile, les séries 6000 d\' aluminium en alliage ont émergé comme le matériau de feuille de carrosserie la plus prometteuse endurcirable avec l\'âge dans l\'industrie de l\' automobile.
Actuellement, l\' un d\' alliage de feuille de carrosserie utilisé pour sa combinaison de solidité et formabilité dans la trempe (T4) AA6111 un alliage de Al-Mg-Si- Cu. Dans cet article, le comportement T4 de AA6111 a été étudié au moyen de l\'essai de traction, l\'évaluation
de microdureté, la calorimétrie de balayage différentiel (CBD), la microscopie électronique à balayage (MEB) et l\'analyse radioscopique. Les résultats montrent que AA6111 atteint une solidité monotone après approximativement 120 h de vieillissement naturel.
La microstructure consiste d\'une matrice d\' aluminium et les particules intermétalliques angulaires contenant principalement Al, Fe, Cu, Si, Mn dispersés dans la
microstructure. Les particules intermétalliques sont trouvées de posséder une formule structurelle du type Alx Fe Si. Comparé avec d\' autres séries d\' alliage de
6xxx sous la même condition de T4, AA6111 montre les propriétés de solidité supérieure. Les vieillissement naturel est observé d\' influer sur la réaction cinétique
de AA6111. Ghana Journal of Science Vol. 47 2007: pp. 91-10
Taguchi Optimization of Process Parameters in Friction Stir Welding of 6061 Aluminum Alloy: A Review and Case Study
SCENARIOS FOR PRICE DETERMINATION IN INCOMPLETE MARKETS
We study the problem of determination of asset prices in an incomplete market proposing three different but related scenarios, based on utility pricing. One scenario uses a market game approach whereas the other two are based on risk sharing or regret minimizing considerations. Dynamical schemes modeling the convergence of the buyer and seller prices to a unique price are proposed. The case of exponential utilities is treated in detail, in the simplest possible example of an incomplete market, the trinomial model.Incomplete markets, market games, risk sharing, regret, dynamical schemes
Regulating the Environmental Consequences of Preferences for Social Status within an Evolutionary Framework
Taking as given that we are consuming too much and that overconsumption leads to environmental degradation, the present paper examines the regulator's choices between informative advertisement and consumption taxation. We model overconsumption by considering individuals that care about social status apart from the intrinsic utility, derived from direct consumption. We assume that there also exist individuals that care only about their own private consumption and we examine the evolution of preferences through time by allowing individuals to alter their behavior as a result of a learning process, akin to a replicator dynamics type. We consider the regulator's choice of consumption taxation and informative advertisement both in an arbitrary and an optimal control context. In the arbitrary overconsumption control context we find that the regulator could decrease, or even eliminate, the share of status seekers in the population. In the context of optimal overconsumption control, we show that the highest welfare is attained when status seekers are completely eliminated, while the lowest in the case that the entire population consists of status seekers
On Complexities of Impact Simulation of Fiber Reinforced Polymer Composites: A Simplified Modeling Framework
Impact modeling of fiber reinforced polymer composites is a complex and challenging task, in particular for practitioners with less experience in advanced coding and user-defined subroutines. Different numerical algorithms have been developed over the past decades for impact modeling of composites, yet a considerable gap often exists between predicted and experimental observations. In this paper, after a review of reported sources of complexities in impact modeling of fiber reinforced polymer composites, two simplified approaches are presented for fast simulation of out-of-plane impact response of these materials considering four main effects: (a) strain rate dependency of the mechanical properties, (b) difference between tensile and flexural bending responses, (c) delamination, and (d) the geometry of fixture (clamping conditions). In the first approach, it is shown that by applying correction factors to the quasistatic material properties, which are often readily available from material datasheets, the role of these four sources in modeling impact response of a given composite may be accounted for. As a result a rough estimation of the dynamic force response of the composite can be attained. To show the application of the approach, a twill woven polypropylene/glass reinforced thermoplastic composite laminate has been tested under 200 J impact energy and was modeled in Abaqus/Explicit via the built-in Hashin damage criteria. X-ray microtomography was used to investigate the presence of delamination inside the impacted sample. Finally, as a second and much simpler modeling approach it is shown that applying only a single correction factor over all material properties at once can still yield a reasonable prediction. Both advantages and limitations of the simplified modeling framework are addressed in the performed case study
An integrated multiphysics model for friction stir welding of 6061 Aluminum alloy
This article presents a new, combined ‘integrated’- ‘multiphysics’ model of friction stir welding (FSW) where a set of governing equations from non-Newtonian incompressible fluid dynamics, conductive and convective heat transfer, and plain stress solid mechanics have been coupled for calculating the process variables and material behaviour both during and after welding. More specifically, regarding the multiphysics feature, the model is capable of simultaneously predicting the local distribution, location and magnitude of maximum temperature, strain, and strain rate fields around the tool pin during the process; while for the integrated (post-analysis) part, the above predictions have been used to study the microstructure and residual stress field of welded parts within the same developed code. A slip/stick condition between the tool and workpiece, friction and deformation heat source, convection and conduction heat transfer in the workpiece, a solid mechanics-based viscosity definition, and the Zener-Hollomon- based rigid-viscoplastic material properties with solidus cut-off temperature and empirical softening regime have been employed.
In order to validate all the predicted variables collectively, the model has been compared to a series of published case studies on individual/limited set of variables, as well as in-house experiments on FSW of aluminum 6061