Single facility location problems with unbounded unit balls

In this paper we consider a new class of continuous location problems where the distances are measured by gauges of closed (not necessarily bounded) convex sets. These distance functions do not satisfy the definiteness property and therefore they can be used to model those situations where there exist zero-distance regions. We prove a geometrical characterization of these measures of distance as the length of shortest paths between points using only a subset of directions of their unit balls. We also characterize the complete set of optimal solutions for this class of continuous single facility location problems and we give resolution methods to solve them. Our analysis allows to consider new models of location problems and generalizes previously known results.     

Direction of magnetization and domain wall mobility in (Dy,Y)Fe2

Magnetization measurements in the (Dy _x Y_1−x )Fe₂ intermetallic compounds show evidence of blocking of domain wall motion. This effect is a function of concentrationx. The direction of magnetization is also dependent on the Dy concentration. We have used the Mossbauer spectroscopy of⁵⁷Fe to verify the direction of magnetization in the series as a function ofx and temperature. The results show that this change in easy direction occurs at higher temperatures than those where the blocking is detected through DC magnetization measurements. supported by RHAE/SCT.     

Scattering states of charged particles in the ℤ2 gauge theoriesgauge theories

Scattering states of charged particles in a massive Euclidean lattice gauge model are constructed.Partially supported by CNPq     

Stark broadening of neutral helium lines and spectroscopic diagnostics of pulsed helium plasma

Stark broadening parameters (widths and shifts) of two He I isolated spectral lines are measured in a plasma of a low-pressure pulsed arc. Plasma electron densities, determined by spectroscopic method based on previously calibrated He I lines, ranges from 1 x 10¹⁶ cm^-3 to 6 x 10¹⁶ cm^-3. The plasma electron temperature acquired by a Boltzmann plot of several He I lines, lies in the interval 8 000-30 000 K. Results of this work are compared with theoretical predictions and with other experimental data.Received: 30 April 2003, Published online: 29 July 2003PACS: 52.70.-m Plasma diagnostic techniques and instrumentation - 52.70.Kz Optical (ultraviolet, visible, infrared) measurements - 32.70.Jz Line shapes, widths, and shiftsR. Santamarta: Present address: DESY/ZEUS Hamburg, Germany.     

Description of pulse propagation in a dispersive medium by use of a pulse quality factor

We investigated how the duration of short laser pulses evolves in a dispersive material, using rms widths and a propagation law based on a pulse quality factor. Experiments were carried out with femtosecond pulses (10 to 25fs at the temporal waist) propagating in bulk fused silica. Excellent agreement was found between theory and experiment. This approach does not require complete characterization of laser pulses and eliminates the need for any assumption regarding the interpretation of autocorrelation traces. The method is of general validity, and it can be applied to pulses of arbitrary shape.     

On the piezoelectricity of anionic collagen films

In this paper, we report results of a study of the physicochemical, dielectric and piezoelectric properties of anionic and native collagen films, considering the development of new biomaterials which have potential applications in coating of cardiovascular prostheses, support for cellular growth and in systems for controlled drug delivery. The piezoelectric strain tensor element d₁₄, the elastic constant s₅₅, and the dielectric permittivity ?₁₁ were measured for the anionic and native collagen films. It was observed that the collagen samples submitted to the alkaline treatment present lower thermal stability than those made from native collagen. However, the treated samples present a higher piezoelectricity compared with the native collagen. The frequency constant fL and the piezoelectric strain element d₁₄, obtained for the alkaline-treated sample (72 h), present the highest values for the samples under study (444.1 kHz m and 0.079 pC/N, respectively). We believe that the alkaline treatment led to an increase of the organization of the microscopic fiber structure of the sample, which could result in an increase of the piezoelectricity.     

Characteristic Features of Magnetization Reversal of Exchange Coupled Tb–Co/FeNi Film Structures in a Temperature Range Including the Compensation Point of the Ferrimagnetic Layer

Physics of the Solid State - The results of the study of the magnetic properties of exchange coupled Tb–Co/FeNi film structures obtained by magnetron sputtering in a wide range of...