Strange Nonchaotic Attractors in Harper Maps

We study the existence of Strange Nonchaotic Attractors (SNA) in the family of Harper maps, proving that they are typical but not robust in this family. Our approach is based on the theory of linear skewproducts and the spectral theory of Schrodinger operators

TR-2015-1 Preliminary Hydraulic Design of a Step-Pool-Type, Nature-Like Fishway March 30, 2015

This technical report presents a method for the preliminary hydraulic design of a step-pool type, nature-like fishway. The method and its companion example, “Nature-Like Fishway at the Obex Mills dam site”, are presented as an instructional exercise illustrating how one may bridge the gap between a conceptual layout and subsequent, more detailed, design phases. This report is intended to supplement the “Federal Interagency Nature-like Fish Passage Guidelines for Atlantic Coast Diadromous Fishes” (unpublished; forthcoming 2015)

Semi-analytical computation of heteroclinic connections between center manifolds with the parameterization method

This paper presents methodology for the computation of whole sets of heteroclinic connections between iso-energetic slices of center manifolds of center x center x saddle fixed points of autonomous Hamiltonian systems. It involves: (a) computing Taylor expansions of the center-unstable and center-stable manifolds of the departing and arriving fixed points through the parameterization method, using a new style that uncouples the center part from the hyperbolic one, thus making the fibered structure of the manifolds explicit; (b) uniformly meshing iso-energetic slices of the center manifolds, using a novel strategy that avoids numerical integration of the reduced differential equations and makes an explicit 3D representation of these slices as deformed solid ellipsoids; (c) matching the center-stable and center-unstable manifolds of the departing and arriving points in a Poincar\'e section. The methodology is applied to obtain the whole set of iso-energetic heteroclinic connections from the center manifold of L2 to the center manifold of L1 in the Earth-Moon circular, spatial Restricted Three-Body Problem, for nine increasing energy levels that reach the appearance of Halo orbits in both L1 and L2. Some comments are made on possible applications to space mission design.Comment: 36 pages, 14 figure

Possible polarisation and spin dependent aspects of quantum gravity

We argue that quantum gravity theories that carry a Lie algebraic modification of the Poincare' and Heisenberg algebras inevitably provide inhomogeneities that may serve as seeds for cosmological structure formation. Furthermore, in this class of theories one must expect a strong polarisation and spin dependence of various quantum-gravity effects.Comment: Awarded an "honourable mention" in the 2007 Gravity Research Foundation Essay Competitio

El miedo a lo desconocido en "El almohadón de plumas", de Horacio Quiroga, y "El huésped", de Amparo Dávila: un enfoque comparatístico

La tematología es un método que utiliza la Literatura Comparada para analizar dos obras a partir del tema del que hablan. Cada uno de estos temas se construye a partir de unidades más pequeñas, llamadas motivos. Cuando los motivos se modifican ocurre un desplazamiento temático, lo que origina una actualización del tema en una determinada obra. Tanto “El almohadón de plumas”, de Horacio Quiroga, como “El huésped”, de Amparo Dávila, están construidos a partir del mismo tema: el miedo a lo desconocido. Sin embargo, cada actualización es diferente, lo que puede apreciarse gracias a la modificación de cuatro motivos: la focalización del narrador, la triada trágica, la nominalización de los antagonistas y los desdoblamientos

TR-2013-1 Fishway Inspection Guidelines (6/5/2013)

This technical report provides guidance for engineers, biologists, operators, regulators and dam owners involved in the inspection of fishways at dams. Volitional fish ladders, fish lifts, and other fish passage and protection facilities are devices of varying complexity frequently integrated into sophisticated reservoir management and hydropower installations. As with any device, maintenance of fish passage facilities is necessary to ensure their proper operation. Improper operation of fishways may limit or eliminate entire year classes of diadromousfish. Routine fishway inspections are a critical component of an overall fish passage operation and maintenance plan