Effect of residual stress on recrystallization behavior of mechanically alloyed steels

This paper presents a finite element modeling analysis of deformation on iron-base mechanically alloyed oxide dispersion strengthened alloy by spherical indentations (Brinell test). Results of the model are used to interpret the role of residual shear stresses on the development of recrystallized grain structure and the temperature at which recrystallization occurs.I. Toda Caraballo acknowledges the Spanish Ministerio de Ciencia e Inovacio´n for financial support in the form of Ph.D. research grant (FPI). The authors acknowledge financial support for this investigation from the Spanish Ministerio de Educacio´n y Ciencia through the Plan Nacional 2006 ENE2006-15170-C02- 01/ALT.Peer reviewe

Tangential Touch between the Free and the Fixed Boundary in a Semilinear Free Boundary Problem in Two Dimensions

The main result of this paper concerns the behavior of a free boundary arising from a minimization problem, close to the fixed boundary in two dimensions

A Bose-Einstein Approach to the Random Partitioning of an Integer

Consider N equally-spaced points on a circle of circumference N. Choose at random n points out of $N$ on this circle and append clockwise an arc of integral length k to each such point. The resulting random set is made of a random number of connected components. Questions such as the evaluation of the probability of random covering and parking configurations, number and length of the gaps are addressed. They are the discrete versions of similar problems raised in the continuum. For each value of k, asymptotic results are presented when n,N both go to infinity according to two different regimes. This model may equivalently be viewed as a random partitioning problem of N items into n recipients. A grand-canonical balls in boxes approach is also supplied, giving some insight into the multiplicities of the box filling amounts or spacings. The latter model is a k-nearest neighbor random graph with N vertices and kn edges. We shall also briefly consider the covering problem in the context of a random graph model with N vertices and n (out-degree 1) edges whose endpoints are no more bound to be neighbors

Many-body-QED perturbation theory: Connection to the Bethe-Salpeter equation

The connection between many-body theory (MBPT)--in perturbative and non-perturbative form--and quantum-electrodynamics (QED) is reviewed for systems of two fermions in an external field. The treatment is mainly based upon the recently developed covariant-evolution-operator method for QED calculations [Lindgren et al. Phys. Rep. 389, 161 (2004)], which has a structure quite akin to that of many-body perturbation theory. At the same time this procedure is closely connected to the S-matrix and the Green's-function formalisms and can therefore serve as a bridge between various approaches. It is demonstrated that the MBPT-QED scheme, when carried to all orders, leads to a Schroedinger-like equation, equivalent to the Bethe-Salpeter (BS) equation. A Bloch equation in commutator form that can be used for an "extended" or quasi-degenerate model space is derived. It has the same relation to the BS equation as has the standard Bloch equation to the ordinary Schroedinger equation and can be used to generate a perturbation expansion compatible with the BS equation also for a quasi-degenerate model space.Comment: Submitted to Canadian J of Physic

Deuteron Magnetic and Quadrupole Moments with a Poincar\'e Covariant Current Operator in the Front-Form Dynamics

The deuteron magnetic and quadrupole moments are unambiguosly determined within the front-form Hamiltonian dynamics, by using a new current operator which fulfills Poincar\'e, parity and time reversal covariance, together with hermiticity and the continuity equation. For both quantities the usual disagreement between theoretical and experimental results is largely removed.Comment: To appear in Phys. Rev. Let

Individual Rights Under State Constitutions in 2018: What Rights are Deeply Rooted in a Modern-Day Consensus of the States?

This Article is actually the third and final article in a series that began with (A) Steven G. Calabresi & Sarah E. Agudo, Individual Rights Under State Constitutions When the Fourteenth Amendment Was Ratified in 1868: What Rights Are Deeply Rooted in American History and Tradition?; and (B) Steven G. Calabresi, Sarah E. Agudo, and Kathryn L. Dore, State Bills of Rights in 1787 and 1791: What Individual Rights Are Really Deeply Rooted in American History and Tradition?. This Article looks at what rights are protected by state constitutions today, in 2018, and compares our findings with the data we collected in our earlier two articles, which looked at rights under state constitutional law in 1868 when the Fourteenth Amendment was ratified, and at what rights were protected in state constitutional law in 1791 when the Federal Bill of Rights with its Ninth Amendment was ratified

Graft Neutrophil Sequestration and Concomitant Tissue Plasminogen Activator Release During Reperfusion in Clinical Kidney Transplantation

Background. Inflammation, coagulation, and fibrinolysis are tightly linked together. Reperfusion after transient ischemia activates both neutrophils, coagulation, and fibrinolysis. Experimental data suggest that tissue plasminogen activator (tPA) regulates renal neutrophil influx in kidney ischemia and reperfusion injury. Methods. In 30 patients undergoing kidney transplantation, we measured renal neutrophil sequestration and tPA release from blood samples drawn from the supplying artery and renal vein early after reperfusion. tPA antigen levels were measured using a commercial enzyme-linked immunosorbent assay kit. For each parameter, transrenal difference (Delta) was calculated by subtracting the value of the arterial sample (ingoing blood) from the value of the venous sample (outgoing blood). Results. Positive transrenal gradients of tPA antigen occurred at 1 minute [Delta = 14 (3-46) ng/mL, P <.01] and 5 minutes [Delta = 5 (-3 to 27) ng/mL, P <.01] after reperfusion. At 5 minutes after reperfusion, a negative transrenal gradient of neutrophils was observed [Delta = -0.17 (-1.45 to 0.24) x 10E9 cells/L, P <.001]. At 1 minute after reperfusion, neutrophil sequestration into the kidney (ie, negative transrenal neutrophil count) correlated significantly with tPA release from the kidney (ie, positive transrenal tPA concentration), (R = -0.513 and P = .006). Conclusions. The findings suggest a proinflammatory role for tPA in ischemia and reperfusion injury in human kidney transplantation.Peer reviewe

H^s versus C^0-weighted minimizers

We study a class of semi-linear problems involving the fractional Laplacian under subcritical or critical growth assumptions. We prove that, for the corresponding functional, local minimizers with respect to a C^0-topology weighted with a suitable power of the distance from the boundary are actually local minimizers in the natural H^s-topology.Comment: 15 page

A numerical model for simulating the effect of strain rate on eutectic band thickness

Large tensile strains acting on the solidifying weld metal can cause the formation of eutectic bands along grain boundaries. These eutectic bands can lead to severe liquation in the partially melted zone of a subsequent overlapping weld. This can increase the risk of heat-affected zone liquation cracking. In this paper, we present a solidification model for modeling eutectic bands. The model is based on solute convection in grain boundary liquid films induced by tensile strains. The proposed model was used to study the influence of strain rate on the thickness of eutectic bands in Alloy 718. It was found that when the magnitude of the strain rate is 10 times larger than that of the solidification rate, the calculated eutectic band thickness is about 200 to 500% larger (depending on the solidification rate) as compared to when the strain rate is zero. In the paper, we also discuss how eutectic bands may form from hot cracks