11,899 research outputs found
Applying uncertainty considerations to energy conservation equations
When applying computer simulation tools in practice uncertainties abound, for example in material properties and boundary conditions. To facilitate the quantification of the effects of uncertainties, the differential, factorial and Monte Carlo methods have been implemented within a simulation tool, ESP-r. These methods require multiple simulations to extract statistical measures of model uncertainty. An alternative approach is to embed uncertainty considerations within the simulation tool's algorithms. The principle advantages of this approach are that the uncertainty is quantified at all times and therefore requires only a single simulation. Coupled with this, it is possible to take control action based on the prevailing effects of uncertainties. This paper details the mathematical techniques required to integrate uncertainty considerations within the energy conservation equations when applied to the simulation of buildings. A comparison is made between the use of this novel approach and traditional mechanisms of assessing uncertainty
Falsification Of The Atmospheric CO2 Greenhouse Effects Within The Frame Of Physics
The atmospheric greenhouse effect, an idea that many authors trace back to
the traditional works of Fourier (1824), Tyndall (1861), and Arrhenius (1896),
and which is still supported in global climatology, essentially describes a
fictitious mechanism, in which a planetary atmosphere acts as a heat pump
driven by an environment that is radiatively interacting with but radiatively
equilibrated to the atmospheric system. According to the second law of
thermodynamics such a planetary machine can never exist. Nevertheless, in
almost all texts of global climatology and in a widespread secondary literature
it is taken for granted that such mechanism is real and stands on a firm
scientific foundation. In this paper the popular conjecture is analyzed and the
underlying physical principles are clarified. By showing that (a) there are no
common physical laws between the warming phenomenon in glass houses and the
fictitious atmospheric greenhouse effects, (b) there are no calculations to
determine an average surface temperature of a planet, (c) the frequently
mentioned difference of 33 degrees Celsius is a meaningless number calculated
wrongly, (d) the formulas of cavity radiation are used inappropriately, (e) the
assumption of a radiative balance is unphysical, (f) thermal conductivity and
friction must not be set to zero, the atmospheric greenhouse conjecture is
falsified.Comment: 115 pages, 32 figures, 13 tables (some typos corrected
Variable structure control for parabolic evolution equations
In this paper it is considered a class of infinite-dimensional control
systems in a variational setting. By using a Faedo-Galerkin method, a sequence
of approximating finite dimensional controlled differential equations is
defined. On each of these systems a variable structure control is applied to
constrain the motion on a specified surface. Under some growth assumptions the
convergence of these approximations to an ideal sliding state for the
infinite-dimensional system is shown. Results are then applied to the Neumann
boundary control of a parabolic evolution equation.Comment: Submitted for presentation to the Joint 44th IEEE Conference on
Decision and Control and European Control Conference ECC 2005; 13 page
Uncertainty Updating in the Description of Coupled Heat and Moisture Transport in Heterogeneous Materials
To assess the durability of structures, heat and moisture transport need to
be analyzed. To provide a reliable estimation of heat and moisture distribution
in a certain structure, one needs to include all available information about
the loading conditions and material parameters. Moreover, the information
should be accompanied by a corresponding evaluation of its credibility. Here,
the Bayesian inference is applied to combine different sources of information,
so as to provide a more accurate estimation of heat and moisture fields [1].
The procedure is demonstrated on the probabilistic description of heterogeneous
material where the uncertainties consist of a particular value of individual
material characteristic and spatial fluctuations. As for the heat and moisture
transfer, it is modelled in coupled setting [2]
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