Results 1 - 10 of 9191
Results 1 - 10 of 9191. Search took: 0.038 seconds
|Sort by: date | relevance|
[en] The charged particle system's energy level separation in the vertical direction of the magnetic field is considered, according to Boltzmann distribution. Several equations are obtained. The effects are obvious under the condition of low temperature and high intensity magnetic field. Several equations of plasma MHD are corrected
[en] Mechanisms of locomotion in microscopic systems are of great interest not only for technological applications but also for the sake of understanding, and potentially harnessing, processes far from thermal equilibrium. Downscaling is a particular challenge and has led to a number of interesting concepts, including thermal ratchet systems and asymmetric swimmers. Here we present a granular ratchet system employing a particularly robust mechanism that can be implemented in various settings. The system consists of wetted spheres of different sizes that adhere to each other, and are subject to a symmetric oscillating, zero average external force field. An inherent asymmetry in the mutual force network leads to force rectification and hence to locomotion. We present a simple model that accounts for the observed behaviour, underscores its robustness and suggests a potential scalability of the concept.
[en] In this Letter we have used the recently introduced redefined Hawking temperature on the event horizon and investigated whether the generalized second law of thermodynamics (GSLT) and thermodynamic equilibrium holds for both the event and the apparent horizons. Here we have considered FRW universe and examined the GSLT and thermodynamic equilibrium with three examples. Finally, we have concluded that from the thermodynamic viewpoint, the universe bounded by the event horizon is more realistic than that by the apparent horizon at least for some examples.
[en] We consider the gravitation-dilaton theory (not necessarily exactly solvable), whose potentials represent a generic linear combination of an exponential and linear functions of the dilaton. A black hole, arising in such theories, is supposed to be enclosed in a cavity, where it attains thermal equilibrium, whereas outside the cavity the field is in the Boulware state. We calculate quantum corrections to the Hawking temperature TH, with the contribution from the boundary taken into account. Vacuum polarization outside the shell tends to cool the system. We find that, for the shell to be in thermal equilibrium, it cannot be placed too close to the horizon. The quantum corrections to the mass due to vacuum polarization vanish in spite of nonzero quantum stresses. We discuss also the canonical boundary conditions and show that accounting for the finiteness of the system plays a crucial role in some theories (e.g., Callan-Giddings-Harvey-Strominger), where it enables us to define the stable canonical ensemble, whereas consideration in an infinite space would predict instability
[en] We investigate the critical behavior of disordered systems transversely driven at a uniform and steady velocity. An intuitive argument predicts that the long-distance physics of D-dimensional driven disordered systems at zero temperature is the same as that of the corresponding -dimensional pure systems in thermal equilibrium. This result is analogous to the well-known dimensional reduction property in thermal equilibrium, which states the equivalence between D-dimensional disordered systems and -dimensional pure systems. To clarify the condition that the dimensional reduction holds, we perform the functional renormalization group (FRG) analysis of elastic manifolds transversely driven in random media. We argue that the nonanalytic behavior in the second cumulant of the renormalized disorder leads to the breakdown of the dimensional reduction. We further found that the roughness exponent is equal to the dimensional reduction value for the single component case, but it is not for the multi-component cases. (paper: disordered systems, classical and quantum)
[en] The surface-atom Casimir-Polder-Lifshitz force out of thermal equilibrium is investigated in the framework of macroscopic electrodynamics. Particular attention is devoted to its large distance limit that shows a new, stronger behaviour with respect to the equilibrium case. The frequency shift produced by the surface-atom force on the centre-of-mass oscillations of a harmonically trapped Bose-Einstein condensate and on the Bloch oscillations of an ultra-cold fermionic gas in an optical lattice are discussed for configurations out of thermal equilibrium
[en] The ability of fewest switches surface hopping (FSSH) approach, where the classical degrees of freedom are coupled to an implicit Langevin bath, to establish and maintain an appropriate thermal equilibrium was evaluated in the context of a three site model for electron transfer. The electron transfer model consisted of three coupled diabatic states that each depends harmonically on the collective bath coordinate. This results in three states with increasing energy in the adiabatic representation. The adiabatic populations and distributions of the collective solvent coordinate were monitored during the course of 250 ns FSSH-Langevin (FSSH-L) simulations performed at a broad range of temperatures and for three different nonadiabatic coupling strengths. The agreement between the FSSH-L simulations and numerically exact results for the adiabatic population ratios and solvent coordinate distributions was generally favorable. The FSSH-L method produces a correct Boltzmann distribution of the solvent coordinate on each of the adiabats, but the integrated populations are slightly incorrect because FSSH does not rigorously obey detailed balance. The overall agreement is better at high temperatures and for high nonadiabatic coupling, which agrees with a previously reported analytical and simulation analysis [J. R. Schmidt, P. V. Parandekar, and J. C. Tully, J. Chem. Phys. 129, 044104 (2008)] on a two-level system coupled to a classical bath
[en] We address estimation of temperature for finite quantum systems at thermal equilibrium and show that the Landau bound to precision , originally derived for a classical not too small system being a portion of a large isolated system at thermal equilibrium, may be also achieved by energy measurement in microscopic quantum systems exhibiting vanishing gap as a function of some control parameter. On the contrary, for any quantum system with a non-vanishing gap Δ, precision of any temperature estimator diverges as . (letter)
[en] In this study, laser-induced breakdown spectroscopy (LIBS) was applied to detect some samples of tea, which were picked in three different seasons: spring, summer, and autumn. The relationship between some elements in the tea and the characteristics of its origin was analyzed. By comparing the relative intensity of the characteristic spectral lines of some elements in the tea samples harvested in different seasons, it was found that the content of some elements varies with the seasons. Besides this, the Pb in tea was quantitatively analyzed by the internal standard method. Then, the detection limit of Pb in the tea samples by LIBS in the experiment was calculated to be about 48.4 mg kg−1. Moreover, the properties of plasma temperature and electron number density were studied and local thermal equilibrium state was verified. The carbon-nitrogen (CN) molecular bands were also clearly observed in the experiment and simulated. The vibrational temperature and rotational temperature of the CN molecules were also obtained, which were 7300 K and 7100 K, respectively. Finally, electron temperature, vibrational temperature and rotational temperature were compared and briefly discussed. (letter)