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We analyze the focusing properties of Fresnel zone plates fabricated over steel tapes using laser ablation. Our intention is to implement the use of micro-optical elements when the use of conventional chrome-glass elements is not indicated. Because of the manufacture process, the surface presents a certain anisotropic roughness, which reduces the focusing properties. First, we develop numerical simulations by means of the Rayleigh--Sommerfeld approach, showing how roughness in both levels of the Fresnel zone plate affects the focalization of the lens. We also manufacture Fresnel zone plates over steel tape, and perform experimental verification that corroborates the numerical results. [c] 2010 Optical Society of America OCIS codes: 050.1965, 240.3990, 240.5770.

The skin-friction topology of a 12:6:1 semi-ellipsoid wing at incidence intersecting a plane wall was examined using flow-visualization techniques. Symmetry, low, intermediate and high incidences form the divisions between general ranges that are marked by significant variations in the topology. Three-dimensional pressure gradients and transition to turbulence affect the topological evolution as a function of incidence. Slight geometric asymmetries significantly influence the topology and related separation modes.

Radial unpremeditated loading influences the buckling of shells. Early structural defects in the shell form increase the severity of the buckling reaction. Stochastic modelling of the defects are usually noted. The probabilistic presentation of uncertainty is substituted by convex models. The characteristics of structural uncertainties yield limited amount of data appropriate for convex models. The upper limits of the pulse reaction is gauged by an ellipsoidal convex model which relies on primary structurally uncertain features of the shell such as the form causing the defects, restrictions on the amplitudes and size of the shell.

The manipulability ellipsoids are proposed in robotics as a measure of manipulators' performances achievable during tasks execution. The definition of these geometrical entities is based on the Jacobian of the manipulator, and the physical meaning given to the ellipsoids is related to the capability of the mechanism to apply forces with the end effector or to move the tool in some directions of the task-space. This concept has been recently extended to the case of cooperating manipulators. Nevertheless, some questions are still open, both with respect to the basic definition and use of manipulability ellipsoids. Moreover, some problems are found by using a technique proposed in literature for their extension to a multiarm system.

The friction generated along the two principal axes of a solid aluminum ellipsoid, when sliding on a rubber substrate is studied, during an effort to quantitatively separate hyseteretic friction from adhesional friction. An experimental approach is presented to show that contact area is dependant upon direction of sliding, which negates the assumptions upon which the original theory was based.

A new measure based on confidence ellipsoids is developed for judging the contribution of each data point to the determination of the least squares estimate of the parameter vector in [...]

Articles written by R. Friedberg and R.H. Good in the American Journal of Physics focused on the link between the surface charge density functions on a conducting disk and a conducting sphere that has the same charge. Computations show that the same concept applies in the acquisition of the charge densities of both elliptic disks and charged conducting ellipsoids. In addition, the charge distribution of ellipsoids can also be determined using the elliptic disk's principal cross section.