Estudo teórico-experimental em via de determinação de lei de atrito em escoamentos de fluidos hiperconcentrados

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Study of interstitial oxygen mobility in RuSr2GdCu2O8 by internal friction

The discovery of the spatial uniform coexistence of superconductivity and ferromagnetism in ruthenocuprates, RuSr2GdCu2O8 (Ru-1212), has spurred an extraordinary development in the study of the competition between magnetism and superconductivity. However, several points of their preparation process and characterization that determine their superconductive behaviour are still obscure. The improvement of sample preparation conditions involves some thermal treatments in inert atmosphere. Anelastic spectroscopy measurements were made using an inverted torsion pendulum, operating with an oscillation frequency of 38 Hz, temperature in the 90 and 310 K range, heating rate of 1 K/min, and vacuum better than 10(-3) Pa. The results show anelastic relaxation peaks at 210 K related to the presence of interstitial oxygen atoms. The peaks decrease significantly with the oxygen loss caused by the heat treatments in vacuum, appearing again after the annealing of the sample in an oxygen atmosphere. These observed peaks are clearly related to the additional oxygen atoms, with activation energy 0.13 and 0.36 eV, and can be explained in terms by diffusional jumps of interstitial oxygen in the RuO2 planes. (C) 2009 Elsevier B.V. All rights reserved.

New laws for author's rights: adequate for digital preservation?

Introduction. Besides technical and economic-organisational problems, digital preservation also faces legal issues, especially regarding copyright legislation, since all digital preservation strategies involve copying materials and/or using software which is typically copyrighted. The purpose of this paper is to ascertain the extent to which current copyright laws meet the preservation requirements of library materials..Methodology. A cross-sectional analysis of recently updated national copyright laws as well as the impact of the other two protection methods: contractual and technological.Results. Even after the latest updates current copyright legislation is almost useless for digital preservation activities since the opportunities provided by WIPO Copyright Treaty to adapt and extend copyright exceptions and limitations have been used to the full.Conclusion. We need a legislation reform that will make it possible to carry out all required copying and communication activities and software use, even if circumventing technological protection is needed. But that is not enough for licensed works. The best solution for this kind of work is to include specific clauses in the licences that facilitate preservation activities. Thus, cooperation between both parties, libraries and rights' holders, is essential.

Library exceptions in the copyright laws of Ibero-American countries

The development of the digital setting has made it absolutely necessary to revise copyright legislation as a whole, including the exceptions that benefit libraries and similar institutions. Unfortunately, adaptation to the new technological reality is not taking place satisfactorily in most countries - the predominating trend is a refortification of copyright as opposed to user interests, and the maintenance of a certain pre-digital philosophy. In the case of Ibero-America the problem is twofold: aside from obsolescence or a lack of adaptation to the new technological setting, there are countries that have not yet included library-related exceptions in the national laws. Moreover, these happen to be developing countries, whose needs and interests do not coincide with those of the richer nations who paved the path to be followed by international treaties and copy- or copyright agreements. This study looks into the situation of exceptions to copyright to benefit libraries in the countries constituting Ibero-America, with a comparative analysis of the most significant characteristics of their national laws. It is concluded that it is crucial for these countries to take advantage of the options offered through the WIPO Copyright Treaty of 1996 and the results of the WIPO Development Agenda to update their legislation, in order that copyright will be respected, while at the same time making it easier for libraries to continue carrying out their social function in an adequate manner, always with the understanding of the developmental context of these countries.

Debris, Roughness and Friction of Stainless Steel Archwires Following Clinical Use

Objective: To investigate the degree of debris, roughness, and friction of stainless steel orthodontic archwires before and after clinical use.Materials and Methods: For eight individuals, two sets of three brackets (n = 16) each were bonded from the first molar to the first premolar. A passive segment of 0.019- x 0.025-inch stainless steel archwire was inserted into the brackets and tied by elastomeric ligature. Debris level (via scanning electron microscopy), roughness, and frictional force were evaluated as-received and after 8 weeks of intraoral exposure. Mann-Whitney, Wilcoxon signed-rank, and Spearman correlation tests were used for statistical analysis at the .05 level of significance.Results: There were significant increases in the level of debris (P = .0004), roughness of orthodontic wires (P = .002), and friction (P = .0001) after intraoral exposure. Significant positive correlations (P < .05) were observed between these three variables.Conclusion: Stainless steel rectangular wires, when exposed to the intraoral environment for 8 weeks, showed a significant increase in the degree of debris and surface roughness, causing an increase in friction between the wire and bracket during the mechanics of sliding. (Angle Orthod. 2010;80:521-527.)

FLOW PROPERTIES and TUBE FRICTION FACTOR of MILK CREAM: INFLUENCE of TEMPERATURE and FAT CONTENT

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Friction factors, convective heat transfer coefficients and the Colburn analogy for industrial sugarcane juices

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Friction losses in valves and fittings for liquid food products

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Bicomplexes and conservation laws in non-Abelian Toda models

A bicomplex structure is associated with the Leznov-Saveliev equation of integrable models. The linear problem associated with the zero-curvature condition is derived in terms of the bicomplex linear equation. The explicit example of a non-Abelian conformal affine Toda model is discussed in detail and its conservation laws are derived from the zero-curvature representation of its equation of motion.

On the control of a non-ideal engineering system: A friction-driven oscillating system with limited power supply

In this work a switching feedback controller for stick-slip compensation of a 2-DOF mass-spring-belt system which interacts with an energy source of limited power supply (non-ideal case) is developed. The system presents an oscillatory behavior due to the stick-slip friction. As the system equilibrium for a conventional feedback controller is not the origin, a switching control law combining a state feedback term and a discontinuous term is proposed to regulate the position of the mass. The problem of tracking a desired periodic trajectory is also considered. The feedback system is robust with respect to the friction force that is assumed to be within known upper and lower bounds.

On stick-slip homoclinic chaos and bifurcations in a mechanical system with dry friction

In this paper we consider a self-excited mechanical system by dry friction in order to study the bifurcational behavior of the arisen vibrations. The oscillating system consists of a mass block-belt-system which is self-excited by static and Coulomb friction. We analyze the system behavior numerically through bifurcation diagrams, phase portraits, frequency spectra and Poincare maps, which show the existence of nonhomoclinic and homoclinic chaos and a route to homoclinic chaos. The homoclinic chaos is also analyzed analytically via the Melnikov prediction method. The system dynamic is characterized by the existence of two potential wells in the phase plane which exhibit rich bifurcational and chaotic behavior.

On Lugre Friction Model to Mitigate Nonideal Vibrations

In this paper, a nonideal mechanical system with the LuGre friction damping model is considered. The mechanical model of the system is an oscillator not necessarily linear connected with an unbalanced motor of excitation with limited power supply. The control of motion and the attenuation of the Sommerfeld effect of the considered nonideal system are analyzed in this paper The mathematical model of the system is represented by coupled non-linear differential equations. The identification of some interesting nonlinear phenomenon in the transient and steady state motion of the system during the passage through resonance (using applied voltages at dc motor as control parameter) is investigated in detail using numerical simulation. [DOI: 10.1115/1.3124783]

Friction losses in valves and fittings for power-law fluids

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)