47 research outputs found
Higher order correlations for fluctuations in the presence of fields
The higher order moments of the fluctuations for the thermodynamical systems
in the presence of fields are investigated in the framework of a theoretical
method. The metod uses a generalized statistical ensemble consonant with the
adequate expression for the generalized internal energy. The applications refer
to the case of a system in magnetoquasistatic field. In the case of linear
magnetic media one finds that for the description of the magnetic induction
fluctuations the Gaussian approximation is good enough. For nonlinear media the
coresponding fluctuations are non-Gaussian, they having a non-null asymmetry.
Aditionally the respective fluctuations have characteristics of leptokurtic,
mesokurtic and platykurtic type, depending of the value of the magnetic field
strength comparatively with a scaling factor of the magnetization curve.Comment: 10 pages, REVTe
Fluctuations in the presence of fields -Phenomenological Gaussian approximation and a new class of thermodynamic inequalities-
The work approaches the study of the fluctuations for the thermodynamic
systems in the presence of the fields. The approach is of phenomenological
nature and developed in a Gaussian approximation. The study is exemplified on
the cases of a magnetizable continuum in a magnetoquasistatic field, as well as
for the so called discrete systems. In the last case one finds that the
fluctuations estimators depends both on the intrinsic properties of the system
and on the characteristics of the environment. Following some earlier ideas of
one of the authors we present a new class of thermodynamic inequalities for the
systems investigated in this paper. In the case of two variables the mentioned
inequalities are nothing but non-quantum analogues of the well known quantum
Heisenberg (''uncertainty'') relations. Also the obtained fluctuations
estimators support the idea that the Boltzmann's constant k has the
signification of a generic indicator of stochasticity for thermodynamic
systems.
Pacs number(s): 05.20.-y, 05.40.-a, 05.70.-a, 41.20.GzComment: preprint, 24 page
Attenuation of Noise and Vibration Caused by Underground Trains
Abstract Tunnels are used to convey transportation in dense urban areas, especially by underground trains. Underground trains radiate noise and vibration by airborne sound and by transmission of vibration through the rails to the surrounding ground. The acoustic wave propagates through the ground, being transmitted by soil-structure interactions to nearby buildings. The transportation induced vibrations add to the static and other types of loads, and their specific spectral features are well distinguished and perceived as nuisance to people. The disturbing effect caused by these solid borne vibrations can be significantly mitigated by soil replacement of the material under the rails. This technique, which was described in previous publications by the authors, is further developed and analyzed here by modeling and numerical analysis, for underground applications. Illustrative examples show through spectral analysis the role of soil replacement, avoiding sound bridges. In this context, the required thickness of the soil replacement layer was considered. It is shown that a 0.5 m thick layer may be sufficient for most practical purposes
Storage of electromagnetic field energy in matter
The partitioning, uniqueness and form of field energy stored in matter,
and its properties as a state function, is established. Consequently, the
first and second laws apply to the nonfield and field parts of the
internal energy as separate entities. This provides a bridge between
thermodynamics and the classical theory of electromagnetism.
Presentation of the temperature as the sum of nonfield and field
contributions is used to establish field dependent barriers to
temperature decrease toward the absolute zero, and the existence of
field induced temperature jumps. These temperature jumps appear at
the instant the field is switched on, or turned off. The partitioning of
field and nonfield energies is illustrated for a specific case of an ideal
gas, and the heat absorbed by the field is derived in terms of difference
in adiabatic magnetization. Finally, the current, restrictive, form of
electromagnetic field energy density is redefined with respect to the
effect of field energy stored outside the system boundaries