5,193 research outputs found
Quark-lepton symmetry and complementarity
We argue that the difference between the observed approximate quark-lepton
complementarity and the theoretical prediction based on realistic quark-lepton
symmetry within the seesaw mechanism may be adjusted by means of a triplet
contribution in the seesaw formula.Comment: 7 pages, RevTex
Advanced thermoplastic resins, phase 2
High temperature structural resins are required for use on advanced aerospace vehicles as adhesives and composite matrices. NASA-Langley developed polyimide resins were evaluated as high temperature structural adhesives for metal to metal bonding and as composite matrices. Adhesive tapes were prepared on glass scrim fabric from solutions of polyamide acids of the semicrystalline polyimide LARC-CPI, developed at the NASA-Langley Research Center. Using 6Al-4V titanium adherends, high lap shear bond strengths were obtained at ambient temperature (45.2 MPa, 6550 psi) and acceptable strengths were obtained at elevated temperature (14.0 MPa, 2030 psi) using the Pasa-Jell 107 conversion coating on the titanium and a bonding pressure of 1.38 MPa (200 psi). Average zero degree composite tensile and compressive strengths of 1290 MPa (187 ksi) and 883 MPa (128 ksi) respectively were obtained at ambient temperature with unsized AS-4 carbon fiber reinforcement
A semi-Lagrangian scheme for the game -Laplacian via -averaging
We present and analyze an approximation scheme for the two-dimensional game
-Laplacian in the framework of viscosity solutions. The approximation is
based on a semi-Lagrangian scheme which exploits the idea of -averages. We
study the properties of the scheme and prove that it converges, in particular
cases, to the viscosity solution of the game -Laplacian. We also present a
numerical implementation of the scheme for different values of ; the
numerical tests show that the scheme is accurate.Comment: 34 pages, 3 figures. To appear on Applied Numerical Mathematic
Leptogenesis and Low-energy Observables
We relate leptogenesis in a class of theories to low-energy experimental
observables: quark and lepton masses and mixings. With reasonable assumptions
motivated by grand unification, one can show that the CP-asymmetry parameter
takes a universal form. Furthermore the dilution mass is related to the light
neutrino masses. Overall, these models offer a natural explanation for a lepton
asymmetry in the early universe.Comment: 10 pages, revised discussion on light neutrino masse
Flux tubes in the SU(3) vacuum
We analyze the distribution of the chromoelectric field generated by a static
quark-antiquark pair in the SU(3) vacuum. We find that the transverse profile
of the flux tube resembles the dual version of the Abrikosov vortex field
distribution and give an estimate of the London penetration length in the
confined vacuum.Comment: 7 pages, 3 figures, poster contribution to the XXIX International
Symposium on Lattice Field Theory, LATTICE 201
Verifying Policy Enforcers
Policy enforcers are sophisticated runtime components that can prevent
failures by enforcing the correct behavior of the software. While a single
enforcer can be easily designed focusing only on the behavior of the
application that must be monitored, the effect of multiple enforcers that
enforce different policies might be hard to predict. So far, mechanisms to
resolve interferences between enforcers have been based on priority mechanisms
and heuristics. Although these methods provide a mechanism to take decisions
when multiple enforcers try to affect the execution at a same time, they do not
guarantee the lack of interference on the global behavior of the system. In
this paper we present a verification strategy that can be exploited to discover
interferences between sets of enforcers and thus safely identify a-priori the
enforcers that can co-exist at run-time. In our evaluation, we experimented our
verification method with several policy enforcers for Android and discovered
some incompatibilities.Comment: Oliviero Riganelli, Daniela Micucci, Leonardo Mariani, and Yli\`es
Falcone. Verifying Policy Enforcers. Proceedings of 17th International
Conference on Runtime Verification (RV), 2017. (to appear
An adaptive POD approximation method for the control of advection-diffusion equations
We present an algorithm for the approximation of a finite horizon optimal
control problem for advection-diffusion equations. The method is based on the
coupling between an adaptive POD representation of the solution and a Dynamic
Programming approximation scheme for the corresponding evolutive
Hamilton-Jacobi equation. We discuss several features regarding the adaptivity
of the method, the role of error estimate indicators to choose a time
subdivision of the problem and the computation of the basis functions. Some
test problems are presented to illustrate the method.Comment: 17 pages, 18 figure
Fermion masses and mixings in gauge theories
The recent evidence for neutrino oscillations stimulate us to discuss again
the problem of fermion masses and mixings in gauge theories. In the standard
model, several forms for quark mass matrices are equivalent. They become
ansatze within most extensions of the standard model, where also relations
between quark and lepton sectors may hold. In a seesaw framework, these
relations can constrain the scale of heavy neutrino mass, which is often
related to the scale of intermediate or unification gauge symmetry. As a
consequence, two main scenarios arise. Hierarchies of masses and mixings may be
explained by broken horizontal symmetries.Comment: 25 pages, RevTex, no figures. Few misprints corrected and two
references adde
Advanced thermoplastic resins, phase 1
Eight thermoplastic polyimide resin systems were evaluated as composite matrix materials. Two resins were selected for more extensive mechanical testing and both were versions of LaRC-TPI (Langley Research Center - Thermoplastic Polyimide). One resin was made with LaRC-TPI and contained 2 weight percent of a di(amic acid) dopant as a melt flow aid. The second system was a 1:1 slurry of semicrystalline LaRC-TPI powder in a polyimidesulfone resin diglyme solution. The LaRC-TPI powder melts during processing and increases the melt flow of the resin. Testing included dynamic mechanical analysis, tension and compression testing, and compression-after-impact testing. The test results demonstrated that the LaRC-TPI resins have very good properties compared to other thermoplastics, and that they are promising matrix materials for advanced composite structures
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