Full current statistics for a disordered open exclusion process

We consider the nonabelian sandpile model defined on directed trees by Ayyer et al. (2015 Commun. Math. Phys. 335 1065). and restrict it to the special case of a one-dimensional lattice of n sites which has open boundaries and disordered hopping rates. We focus on the joint distribution of the integrated currents across each bond simultaneously, and calculate its cumulant generating function exactly. Surprisingly, the process conditioned on seeing specified currents across each bond turns out to be a renormalised version of the same process. We also remark on a duality property of the large deviation function. Lastly, all eigenvalues and both Perron eigenvectors of the tilted generator are determined.

The statistics of the second order response of an FPSO in spreading seas

An expression for the probability density function of the second order response of a general FPSO in spreading seas is derived by using the Kac-Siegert approach. Various approximations of the second order force transfer functions are investigated for a ship-shaped FPSO. It is found that, when expressed in non-dimensional form, the probability density function of the response is not particularly sensitive to wave spreading, although the mean squared response and the resulting dimensional extreme values can be sensitive. The analysis is then applied to a Sevan FPSO, which is a large cylindrical buoy-like structure. The second order force transfer functions are derived by using an efficient semi-analytical hydrodynamic approach, and these are then employed to yield the extreme response. However, a significant effect of wave spreading on the statistics for a Sevan FPSO is found even in non-dimensional form. It implies that the exact statistics of a general ship-shaped FPSO may be sensitive to the wave direction, which needs to be verified in future work. It is also pointed out that the Newman's approximation regarding the frequency dependency of force transfer function is acceptable even for the spreading seas. An improvement on the results may be attained when considering the angular dependency exactly. Copyright © 2009 by ASME.

The ensemble statistics of the band-averaged energy of a random system

This paper is concerned with the response statistics of a dynamic system that has random properties. The frequency-band-averaged energy of the system is considered, and a closed form expression is derived for the relative variance of this quantity. The expression depends upon three parameters: the modal overlap factor m, a bandwidth parameter B, and a parameter α that defines the nature of the loading (for example single point forcing or rain-on-the-roof loading). The result is applicable to any single structural component or acoustic volume, and a comparison is made here with simulation results for a mass loaded plate. Good agreement is found between the simulations and the theory. © 2003 Published by Elsevier Ltd.

The ensemble statistics of the energy of a random system subjected to harmonic excitation

This paper is concerned with the ensemble statistics of the response to harmonic excitation of a single dynamic system such as a plate or an acoustic volume. Random point process theory is employed, and various statistical assumptions regarding the system natural frequencies are compared, namely: (i) Poisson natural frequency spacings, (ii) statistically independent Rayleigh natural frequency spacings, and (iii) natural frequency spacings conforming to the Gaussian orthogonal ensemble (GOE). The GOE is found to be the most realistic assumption, and simple formulae are derived for the variance of the energy of the system under either point loading or rain-on-the-roof excitation. The theoretical results are compared favourably with numerical simulations and experimental data for the case of a mass loaded plate. © 2003 Elsevier Ltd. All rights reserved.

Statistics of dissipation and enstrophy induced by localized vortices

The ratios of enstrophy and dissipation moments induced by localized vorticity are inferred to be finite. It follows that the scaling exponents for locally averaged dissipation and enstrophy are equal. However, enstrophy and dissipation exponents measured over finite ranges of scales may be different. The cylindrical vortex profile that yields maximal moment ratios is determined. The moment ratios for cylindrical vortices are used to interpret differences in scale dependence of enstrophy and dissipation previously found in numerical simulations.

Effects Of Subgrid-Scale Modeling On Lagrangian Statistics In Large-Eddy Simulation

The application of large-eddy simulation (LES) to turbulent transport processes requires accurate prediction of the Lagrangian statistics of flow fields. However, in most existing SGS models, no explicit consideration is given to Lagrangian statistics. In this paper, we focus on the effects of SGS modeling on Lagrangian statistics in LES ranging from statistics determining single-particle dispersion to those of pair dispersion and multiparticle dispersion. Lagrangian statistics in homogeneous isotropic turbulence are extracted from direct numerical simulation (DNS) and the LES with a spectral eddy-viscosity model. For the case of longtime single-particle dispersion, it is shown that, compared to DNS, LES overpredicts the time scale of the Lagrangian velocity correlation but underpredicts the Lagrangian velocity fluctuation. These two effects tend to cancel one another leading to an accurate prediction of the longtime turbulent dispersion coefficient. Unlike the single-particle dispersion, LES tends to underestimate significantly the rate of relative dispersion of particle pairs and multiple-particles, when initial separation distances are less than the minimum resolved scale due to the lack of subgrid fluctuations. The overprediction of LES on the time scale of the Lagrangian velocity correlation is further confirmed by a theoretical analysis using a turbulence closure theory.

Fracture statistics of brittle materials: Weibull or normal distribution

The fit of fracture strength data of brittle materials (Si3N4, SiC, and ZnO) to the Weibull and normal distributions is compared in terms of the Akaike information criterion. For Si3N4, the Weibull distribution fits the data better than the normal distribution, but for ZnO the result is just the opposite. In the case of SiC, the difference is not large enough to make a clear distinction between the two distributions. There is not sufficient evidence to show that the Weibull distribution is always preferred to other distributions, and the uncritical use of the Weibull distribution for strength data is questioned.

Influence of threshold stress on the estimation of the Weibull statistics

The influence of threshold stress on the estimation of the Weibull statistics is discussed in terms of the Akaike information criterion. Numerical simulations show that, if sample data are limited in number and threshold stress is not too large, the two-parameter Weibull distribution is still a preferred choice. For example, the fit of strength data of glass and ceramics to the two- and three-parameter Weibull distributions is compared.

Soporte vital y terapia intensiva.Muerte intervenida

El concepto de muerte intervenida comprende todas aquellas situaciones clínicas en las que la abstención o retiro de algún método de soporte vital en el transcurso de la asistencia médica se propone como un límite en el tratamiento, quedando vinculado el mismo con la llegada de la muerte cardiorrespiratoria tradicional. La presencia de una tecnología médica (soporte vital) común en todos los casos, permite la consideración comprensiva de todo su conjunto. Finalmente, en todos ellos la muerte se vincula a una acción u omisión de la tecnología médica. Una evaluación común de estos casos no sólo tiene una lógica derivada de la operatividad que hizo posible la existencia de estos pacientes sino que además promueve la interpretación verdadera y correcta de los hechos por parte de la sociedad. La reflexión sobre la muerte intervenida como un fenómeno emergente de nuestra cultura resulta imprescindible para que la sociedad se involucre y participe en un tema que le incumbe en forma absoluta y exclusiva.

Agotamiento vital en pacientes hipotiroideos antes y después del tratamiento con levotiroxina

Resumen: El objetivo de este trabajo fue comprobar la existencia de Agotamiento Vital (AV) en pacientes con Hipotiroidismo Primario (HP), si el tratamiento del HP modifica el AV, y si existe asociación entre TSH y respuesta del AV al tratamiento. Se agruparon estos teniendo en cuenta la similitud clínica entre el AV y el HP y el riesgo cardiovascular implicado. En una muestra de 31 mujeres con HP, se midió AV y TSH pre y pos tratamiento del HP. Posteriormente se estudió la relación entre el nivel TSH y la respuesta al AV. Conclusiones: La mayoría de los pacientes con HP presentaron AV, situación que se revierte luego del tratamiento del HP. Existe un grupo de pacientes en los que persiste el AV luego del tratamiento y en los cuales el valor de TSH es mayor que en los que el AV revierte.