Ensenada Center for Scientific Research and Higher Education

About: Ensenada Center for Scientific Research and Higher Education is a facility organization based out in Ensenada, Mexico. It is known for research contribution in the topics: Population & Nonlinear system. The organization has 1934 authors who have published 3733 publications receiving 63115 citations.

Theoretical aspects of particle movement in flowing magma: implications for the anisotropy of magnetic susceptibility of dykes

Abstract: Abstract Most studies of the anisotropy of magnetic susceptibility (AMS) of dykes have assumed that the axes of maximum susceptibility (kmax) should define an opposed imbrication pointing along the direction of magma flow, and that this orientation should be preserved along the dyke. This assumption is partially based on a model predicting the orientation of ellipsoidal particles floating in a moving liquid although the model actually predicts a cyclic movement of the particles that has been overlooked in msot AMS studies without further justification. The consequences of considering the full rotation of the ellipsoidal particles, as actually predicted by the theory, in the expected AMS of dykes are examined in this work. The complete version of the motion of ellipsoidal particles is then incorporated in a model of magma movement that takes into consideration the distribution of shear deformation within the dyke as predicted from the velocity gradient of the moving magma. Results of this model show that both particle elongation and the amount of shear that is sampled will affect the quality of the AMS results. By paying attention to the systematic variations of the AMS predicted by the theory, however, it is possible to devise sampling schemes that can be used to add more confidence to the interpretation of the AMS results. Although based on an idealized scenario of magma movement within a dyke, the model developed here explains satisfactorily the sometimes observed variation of AMS along flow direction in one dyke, and provides a simple explanation for many of the ‘abnormal’ magnetic fabrics that have been reported in dyke swarms around the world.

Connectivity in the Northern Gulf of California From Particle Tracking in a Three-Dimensional Numerical Model

Abstract: The northern Gulf of California, Mexico, is one of the most productive and diverse marine ecosystems in the world. It currently harbors three marine protected areas, including two biosphere reserves. Despite its significance as a conservation site and its importance for Mexico's fisheries, proper knowledge of population connectivity and larvae dispersal from spawning sites is largely lacking. Our study focuses on connectivity in the northern gulf resulting from advection by currents and turbulent diffusion during summer, the main spawning period of various key commercial species. We calculated connectivity matrices in the northern Gulf from currents produced by the output of a three-dimensional baroclinic numerical model and a random walk process to simulate turbulent motions. We released 2000 hypothetical passive particles in each of 21 areas along the coast (between 0–60 m deep) during the summer and followed their trajectories for periods of 2, 4, 6, and 8 weeks. For the case of full time transport, the effects of tidal currents are minimal in the overall dispersal of passive particles on the time scales studied. However, this can be substantially altered if the particles are allowed to avoid being transported for periods of time; this is illustrated by striking differences between the connectivity matrices obtained by modeling also night-only and day-only advection. This “order zero” connectivity study (i.e., not including realistic larvae behavior, which is species-specific) reveals that during the summer spawning season of key commercial species, regional hydrodynamics produce a cyclonic downstream connectivity along the coast, from the mainland to the Baja California coast. Our results provide the basis for a full connectivity study where larvae behavior and settlement habitat will be included.

A novel global asymptotic stable set-point fuzzy controller with bounded torques for robot manipulators

Abstract: This paper addresses the set-point control of robot manipulators with friction where avoiding saturation of the actuators is a major issue. The original contribution is a novel direct fuzzy control system dealing with both practical constraints in mechanical manipulators: saturation and friction. The control system is made by taking advantage of input-output properties of the so-called sectorial fuzzy controllers. When friction is considered, we prove, via Lyapunov theory, that the steady state position errors owing to static friction are inside of a global attractor, which can be arbitrarily reduced. In case of absence of friction, the closed-loop system becomes globally asymptotic stable. In both cases, the important theoretical and practical feature of maintaining the control actions always within prescribed limits according to the actuator torque capabilities is guaranteed. Experimental evaluation of the proposed direct fuzzy control system on a nonlinear direct-drive robot arm is presented to validate its effectiveness.