3,748 research outputs found
The mechanics of solids in the plastically-deformable state
The mechanics of continua, which is based on the general stress model of Cauchy, up to the present has almost exclusively been applied to liquid and solid elastic bodies. Saint-Venant has developed a theory for the plastic or remaining form changes of solids, but it does not give the required number of equations for determining motion. A complete set of equations of motion for plastic deformable bodies is derived. This is done within the framework of Cauch mechanics. And it is supported by certain experimental facts which characterize the range of applications
Location of Center of Pressure of Airplane Wings
Data obtained in the Gottingen Aerodynamic Laboratory give considerable detail on the resulting air force moment exerted on various wing sections at different angles of attack. The Gottingen data can serve well to test the hydrodynamic theory, which (on the assumption of uniform motion and hence of infinitely wide wings) renders it possible to compute this moment as a function of the angle of attack. The Gottigen data can well serve to test the theory and it may be noted that experiment and computation compare favorably
Numerical Stochastic Perturbation Theory. Convergence and features of the stochastic process. Computations at fixed (Landau) Gauge
Concerning Numerical Stochastic Perturbation Theory, we discuss the
convergence of the stochastic process (idea of the proof, features of the limit
distribution, rate of convergence to equilibrium). Then we also discuss the
expected fluctuations in the observables and give some idea to reduce them. In
the end we show that also computation of quantities at fixed (Landau) Gauge is
now possible.Comment: 3 pages. Contributed to 17th International Symposium on Lattice Field
Theory (LATTICE 99), Pisa, Italy, 29 Jun - 3 Jul 199
On a class of linearizable Monge-Amp\`ere equations
Monge-Amp\`ere equations of the form,
arise in many areas of fluid and solid mechanics. Here it is shown that in the
special case , where denotes an arbitrary function,
the Monge-Amp\`ere equation can be linearized by using a sequence of Amp\`ere,
point, Legendre and rotation transformations. This linearization is a
generalization of three examples from finite elasticity, involving plane strain
and plane stress deformations of the incompressible perfectly elastic Varga
material and also relates to a previous linearization of this equation due to
Khabirov [7]
On the relation between quantum mechanical probabilities and event frequencies
The probability `measure' for measurements at two consecutive moments of time
is non-additive. These probabilities, on the other hand, may be determined by
the limit of relative frequency of measured events, which are by nature
additive. We demonstrate that there are only two ways to resolve this problem.
The first solution places emphasis on the precise use of the concept of
conditional probability for successive measurements. The physically correct
conditional probabilities define additive probabilities for two-time
measurements. These probabilities depend explicitly on the resolution of the
physical device and do not, therefore, correspond to a function of the
associated projection operators. It follows that quantum theory distinguishes
between physical events and propositions about events, the latter are not
represented by projection operators and that the outcomes of two-time
experiments cannot be described by quantum logic.
The alternative explanation is rather radical: it is conceivable that the
relative frequencies for two-time measurements do not converge, unless a
particular consistency condition is satisfied. If this is true, a strong
revision of the quantum mechanical formalism may prove necessary. We stress
that it is possible to perform experiments that will distinguish the two
alternatives.Comment: 16 pages LATEX. Minor corrections, final version to appear in Ann.
Phy
No-reference image quality assessment through the von Mises distribution
An innovative way of calculating the von Mises distribution (VMD) of image
entropy is introduced in this paper. The VMD's concentration parameter and some
fitness parameter that will be later defined, have been analyzed in the
experimental part for determining their suitability as a image quality
assessment measure in some particular distortions such as Gaussian blur or
additive Gaussian noise. To achieve such measure, the local R\'{e}nyi entropy
is calculated in four equally spaced orientations and used to determine the
parameters of the von Mises distribution of the image entropy. Considering
contextual images, experimental results after applying this model show that the
best-in-focus noise-free images are associated with the highest values for the
von Mises distribution concentration parameter and the highest approximation of
image data to the von Mises distribution model. Our defined von Misses fitness
parameter experimentally appears also as a suitable no-reference image quality
assessment indicator for no-contextual images.Comment: 29 pages, 11 figure
The importance of temporal stress variation and dynamic disequilibrium for the initiation of plate tectonics
We use 1-D thermal history models and 3-D numerical experiments to study the impact of dynamic thermal disequilibrium and large temporal variations of normal and shear stresses on the initiation of plate tectonics. Previous models that explored plate tectonics initiation from a steady state, single plate mode of convection concluded that normal stresses govern the initiation of plate tectonics, which based on our 1-D model leads to plate yielding being more likely with increasing interior heat and planet mass for a depth-dependent Byerlee yield stress. Using 3-D spherical shell mantle convection models in an episodic regime allows us to explore larger temporal stress variations than can be addressed by considering plate failure from a steady state stagnant lid configuration. The episodic models show that an increase in convective mantle shear stress at the lithospheric base initiates plate failure, which leads with our 1-D model to plate yielding being less likely with increasing interior heat and planet mass. In this out-of-equilibrium and strongly time-dependent stress scenario, the onset of lithospheric overturn events cannot be explained by boundary layer thickening and normal stresses alone. Our results indicate that in order to understand the initiation of plate tectonics, one should consider the temporal variation of stresses and dynamic disequilibrium
As Consequências Psicológicas da Burocratização
No presente trabalho, o autor discute as consequências psicológicas de preferir um ambiente social e econômico marcado pela organização burocrática ao invés de uma organização econômica racional pautada pelos preços de mercado. No caso da vida social e econômica caracterizada pela burocratização crescente, a tutela paternalista tende a se tornar autoritária e desfavorável ao fortalecimento do senso crítico, sem o qual cria-se a falsa ilusão de que pode haver liberdade sob um sistema de total arregimentação
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