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Tables of Rosseland mean opacities for candidate atmospheres of life hosting free-floating planets

100%
Badescu V.
Open Physics
|
2010
|
vol. 8
|
issue 3
463-479
EN
The existence of life on a free-floating planet is conditioned by the existence of an optically thick atmosphere. This may ensure the long-term thermal stability of a (liquid) solvent on the surface of that body. Requirements to be fulfilled by a hypothetic gas constituent of a free-floating planet atmosphere are studied. The four gases analyzed here (nitrogen, carbon dioxide, methane and ethane) are candidates. They may induce a higher opacity than molecular hydrogen, which has been considered in previous research. The paper deals with preparation of tables of Rosseland mean opacity values. Selection of the ranges of temperature and pressure is guided by life existence considerations. The range of temperatures involved (50 to 650 K) is lower than usually found in the literature. The tables may be useful for studies related to free-floating planets, where the usage of absorption opacity is a straightforward way to compute the energy flux in the atmosphere. Also, the results are useful in all cases where radiation is transferred through dense layers of the gases considered in this paper.
2
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Exact and approximate statistical approaches for the exergy of blackbody radiation

100%
Badescu V.
Open Physics
|
2008
|
vol. 6
|
issue 2
344-350
EN
There is a long term debate in literature about the exergy of blackbody radiation (BBR). Most authors contributing to this dispute used classical thermodynamics arguments. The objective of this paper is to propose a statistical thermodynamics approach. This gives new perspectives to previous results. Four simple statistical microscopic models are used to derive BBR exergy. They consist of combinations of quantum and classical descriptions of the state occupation number and entropy, respectively. In all four cases the BBR exergy (or exergy flux density) is given by the internal energy (or energy flux density) times an efficiency-like factor containing the environment temperature and the blackbody radiation temperature. One shows that Petela-Landsberg-Press efficiency is the “exact” result while the Jeter (Carnot) efficiency corresponds to the classical approximation. Other two (new) approximate efficiency-like factors are also reported.
3
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Exergy of nuclear radiation - a quantum statistical thermodynamics approach

100%
Badescu V.
Open Physics
|
2009
|
vol. 7
|
issue 1
141-146
EN
The exergy of nuclear radiation is evaluated by using a simple quantum statistical thermodynamic approach. Only radiation particles with non-zero rest mass are considered (i.e. protons, neutrons, alpha and beta particles). The exergy and the exergy flux involve efficiency-like factors affecting the internal energy and the energy flux, respectively. These factors are generally different from both the usual Carnot factor and the Petela-Landsberg-Press factor that appears in the exergy of blackbody radiation. The efficiency-like factors are higher in the case of charged rather than neutral particles and in the case of enclosed rather than free radiation. The results are compared with those obtained previously by using a classical thermodynamic theory.
4
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Hydrodynamics of tsunamis generated by asteroid impact in the Black Sea

63%
Isvoranu D., Badescu V.
Open Physics
|
2012
|
vol. 10
|
issue 2
429-446
EN
Two-dimensional and one-dimensional models are used to evaluate the seashore effects of the tsunami generated by an asteroid hitting the deep water in the Eastern region of the Black Sea. The shallow water theory has been used to describe tsunami propagation. The distance between the impact point and the nearest coast is about 150 km. The effects on the coastal regions depend on many factors among which the most important is asteroid size. The tsunami generated by a 250 m asteroid reaches the nearest dry land location in 20 minutes and needs about two hours to hit all over the Black Sea coast. The horizontal inundation length is also known as run-in or run-off distance, according to the direction of water movement. The run-up values may be up to 39 m in the Eastern basin and a more than ten times smaller in theWestern region. The Northern part of the Black Sea coast is not affected by the tsunami. The run-in values of a tsunami generated by a 1000 m diameter asteroid are sensibly larger than the similar values associated to a 250 m diameter asteroid. The run-in strongly depends on the distance from the impact position to the shore and on coastal topographical profile. For instance, the run-in distance in case of a tsunami generated by a 250 m size asteroid is 0.1 km (at Varna), 0.5 km (Ordu), 0.7 km (Yalta) and 1.4 km (Sochi). In case of the 1000 m diameter asteroid the run-in distance is 0.7 km (at Varna) and 2.9 km (Yalta). The results accuracy is also discussed.
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