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  • 1
    Electronic Resource
    Electronic Resource
    Mechanisms for collisionless absorption of light waves obliquely incident on overdense plasmas with steep density gradients (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 2702-2709 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: For p-polarized laser light obliquely incident on overdense plasmas with steep density gradients, a new collisionless absorption mechanism (sheath-transit absorption) is studied analytically and numerically. Complementary to Brunel's "not-so-resonant'' resonant absorption, and to the conventional resonant absorption, the sheath-transit absorption is most effective for steep density gradients and when the light pressure is less than the plasma pressure. It is also shown that the assumption of instantaneous particle reflection, usually a reasonable assumption for the normal incidence case, is invalid for the p-polarized oblique incident case. A test-particle model which provides a simple physical picture of the sheath-transit absorption is presented. Absorption coefficients obtained from the test-particle model agree reasonably well with those from particle-in-cell (PIC) simulations. The transition from the resonant absorption to the sheath-transit absorption as the density gradient steepens is demonstrated by PIC simulations with a wide range of density gradients. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871527
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  • 2
    Electronic Resource
    Electronic Resource
    Superthermal electron production from hot underdense plasmas (1987)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 30 (1987), S. 3825-3831 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Very-high-energy electrons of up to an energy of ∼2.3 MeV have been observed to be emitted from the hot underdense exploding thin foil plasmas created by 10.6 μm CO2 laser radiation at intensity levels up to ∼4×1014 W/cm2. As a supplement to the electron measurements the forward and backward scattered light components were also measured. Correlation of these measurements shows that either Raman scattering or the high-temperature version of two-plasmon decay or both, manifesting themselves near the quarter-critical density region, are responsible for the production of a hot (Th∼135 keV) tail of electrons at least up to energies of 1 MeV. There are no indications that the Raman forward scattering (as distinct from Raman backward scattering) at lower densities plays any significant role. These experimental results are consistent with the results from a l 1/2 -dimensional particle-in-cell code simulation with a parabolic density profile resembling the experimental conditions. An apparent anomaly is discussed, which is that hot electrons are produced (both in experiments and simulations) at energies higher than the trapping value appropriate to electron plasma waves whose phase velocity is equal to the matching value (C/(3)1/2) at the turning point for the light of half the laser frequency.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.866420
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  • 3
    Electronic Resource
    Electronic Resource
    Particle-in-cell simulation of the pulsed planar expansion of a fully ionized plasma off a surface (2002)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 9 (2002), S. 3209-3216 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using particle-in-cell computer simulation, the expansion of a plasma formed by isothermal evaporation of ions and electrons off a planar wall into a vacuum is investigated. The hydrodynamical and electrical characteristics of the ion and electron expansion flow during and after the emission phase are analyzed. Ion acceleration is investigated in detail. While during the emission phase a considerable part of the electron energy is stored in thermal motion, and cannot be converted to ion energy, this conversion happens almost completely in the post-emission phase. As a result, the velocity distribution of ions is increased at large velocities by several orders of magnitude. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1487863
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  • 4
    Electronic Resource
    Electronic Resource
    Guiding large-scale spark discharges with ultrashort pulse laser filaments (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 610-615 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using the nonlinear propagation properties of ultrashort laser pulses in air, we were able to produce long ionized filaments that served to guide spark discharges. With a laser pulse energy of 20 mJ, one or two ionized filaments were created and could guide streamer discharges over 2 m air gaps, where the electric field was fairly uniform and had an average value of 0.6 MV/m. Such a guiding effect was observed for times of 1–3 μs after the laser pulse created the ionized filaments. Longer delays (10–15 μs) were recorded at higher laser pulse energy, with a larger number of filaments. Images of the early stages of the discharge of a uniform air gap show that the laser-produced ionized filaments do not initiate the discharge process but act rather as preferred channels where the leader growth is accelerated. In the end, these straight conductive channels carry the arc current as the voltage in the gap breaks down. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373710
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  • 5
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    Earth-to-air heat exchangers for passive houses located in South-Eastern European countries (2015)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2015-08-27
    Description: Earth-to-air heat exchangers (EAHEs) increase the energy performance of passive houses (PHs). The EAHE's performance depends on the climatology of the place and on design and operational parameters. The current commercial practice for implementing EAHEs in the PHs of South-Eastern Europe is by ad litteram importing the existing German design solutions. This is not always a good strategy from the point of view of thermal performance. In this paper, a reference EAHE with fixed design and operational parameters is defined and its performance is studied, when moved in different geographical places in Germany and other Western and South-Eastern European countries. The maximum yearly heating energy for Western Europe is 2730.6 kW h at Stockholm, while in Munich it is 2202.3 kW h. The same quantity in South-Eastern Europe is 2544.4 kW h at Bucharest. The maximum yearly cooling energy in South-Eastern Europe is 973.5 kW h at Belgrade and 739.7 kW h at Bucharest. This quantity is significantly larger than that for Western Europe (149 kW h at Munich). The EAHEs are indeed effective in the climate of South-Eastern Europe, especially as a cooling source during the warm season. Appropriate design solutions and operational parameters are needed in order to obtain the best EAHE's performance. A few practical recommendations for the implementation of EAHEs operating with forced air circulation are given.
    Electronic ISSN: 1941-7012
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by American Institute of Physics (AIP)
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  • 6
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    Noether’s theorem for dissipative quantum dynamical semi-groups (2015)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2015-02-19
    Description: Noether’s theorem on constants of the motion of dynamical systems has recently been extended to classical dissipative systems (Markovian semi-groups) by Baez and Fong [J. Math. Phys. 54 , 013301 (2013)]. We show how to extend these results to the fully quantum setting of quantum Markov dynamics. For finite-dimensional Hilbert spaces, we construct a mapping from observables to completely positive maps that leads to the natural analogue of their criterion of commutativity with the infinitesimal generator of the Markov dynamics. Using standard results on the relaxation of states to equilibrium under quantum dynamical semi-groups, we are able to characterise the constants of the motion under quantum Markov evolutions in the infinite-dimensional setting under the usual assumption of existence of a stationary strictly positive density matrix. In particular, the Noether constants are identified with the fixed point of the Heisenberg picture semi-group.
    Print ISSN: 0022-2488
    Electronic ISSN: 1089-7658
    Topics: Mathematics , Physics
    Published by American Institute of Physics (AIP)
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  • 7
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    Monthly average daily global and diffuse solar radiation based on sunshine duration and clearness index for Brasov, Romania (2014)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2014-09-25
    Description: The main objective of this study is to develop single location appropriate models for the estimation of the monthly average daily global and diffuse horizontal solar radiation for Brasov, Romania. The study focuses particularly on models based on the sunshine duration and clearness index. The data used for the calibration of the models were collected during a period of 4 yr, between November 2008 and October 2012, at the Transilvania University of Brasov. The testing and validation of the models was carried out using data from the online SoDa database for Brasov for the year 2005. Different statistical error tests were applied to evaluate the accuracy of the models. The predicted values are also compared with values from three other known models concerning the global and diffuse solar radiation. A new mixed model was developed for the estimation of monthly average daily global horizontal solar radiation. The data processing was performed by means of a real-time interface developed with LabVIEW graphical programming language. The parameters taken into account were the relative sunshine, the clearness index, the extraterrestrial radiation, the latitude and the longitude. The methodology is simple and effective and may be applied for any region. Its effectiveness was proven through comparison with global models.
    Electronic ISSN: 1941-7012
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by American Institute of Physics (AIP)
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  • 8
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    Monthly average daily global and diffuse solar radiation based on sunshine duration and clearness index for Brasov, Romania (2014)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2014-10-10
    Description: The main objective of this study is to develop single location appropriate models for the estimation of the monthly average daily global and diffuse horizontal solar radiation for Brasov, Romania. The study focuses particularly on models based on the sunshine duration and clearness index. The data used for the calibration of the models were collected during a period of 4 yr, between November 2008 and October 2012, at the Transilvania University of Brasov. The testing and validation of the models was carried out using data from the online SoDa database for Brasov for the year 2005. Different statistical error tests were applied to evaluate the accuracy of the models. The predicted values are also compared with values from three other known models concerning the global and diffuse solar radiation. A new mixed model was developed for the estimation of monthly average daily global horizontal solar radiation. The data processing was performed by means of a real-time interface developed with LabVIEW graphical programming language. The parameters taken into account were the relative sunshine, the clearness index, the extraterrestrial radiation, the latitude and the longitude. The methodology is simple and effective and may be applied for any region. Its effectiveness was proven through comparison with global models.
    Electronic ISSN: 1941-7012
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by American Institute of Physics (AIP)
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