A Stein Conjecture for the Circle

We discuss the manner in which one might expect directional maximal functions to control the Fourier extension operator via L ² weighted inequalities. We prove a general inequality of this type for the extension operator restricted to circles in the plane.     

Asymptotic behaviour of low density solutions to the generalized Becker-Döring equations

The asymptotic behaviour of solutions to the generalized Becker-D?ring equations is studied. It is proved that solutions converge strongly to a unique equilibrium if the initial density is sufficiently small. Received July 19, 1996     

A spreadsheet-based optimization model for the integrated problem of producing and distributing a major weekly newsmagazine

In this paper, we address the problem of producing and distributing the Brazilian newsmagazine Época, a major weekly publication with one of the 10 largest circulations in the world. This real-world problem had been puzzling magazine publishers in Brazil and remained unsolved for many years. We propose an innovative mixed-integer-linear programming model to determine the number and location of the industrial facilities that should produce the magazines, what destinations should be assigned to each selected facility; the production sequencing and the modes of transportation (air or truck). Our model aims to minimize the total cost while adhering to production capacity and time constraints. The model was implemented in an electronic spreadsheet environment and yielded a savings of 7.1% of the total costs. Given that despite their huge popularity, little has been written on the issues of implementing full-scale optimization models in spreadsheets; thus we also provide the details of the model’s implementation in Excel.     

Motional frequencies in a planar Penning trap

A Penning trap consisting of concentric ring electrodes on a substrate and a magnetic field perpendicular to the substrate plane has been loaded with electrons. In order to demonstrate the performance of the trap we have measured the motional frequencies of the trapped electrons. Frequencies, line shape and width agree well with simulations. Miniaturization of the device is at hand which opens novel possibilities for application in quantum computing. Contribution presented at the TCP06, Vancouver Island, 2006-09-21     

Chaotic Phenomena and Fractional-Order Dynamics in the Trajectory Control of Redundant Manipulators

Redundant manipulators have some advantages when compared with classicalarms because they allow the trajectory optimization, both on the freespace and on the presence of obstacles, and the resolution ofsingularities. For this type of arms the proposed kinematic controlalgorithms adopt generalized inverse matrices but, in general, thecorresponding trajectory planning schemes show important limitations.Motivated by these problems this paper studies the chaos revealed by thepseudoinverse-based trajectory planning algorithms, using the theory offractional calculus.