Radiative forcing of climate

An update of the scientific discussions presented in Chapter 2 of the Intergovernmental Panel on Climate Change (IPCC) report is presented. The update discusses the atmospheric radiative and chemical species of significance for climate change. There are two major objectives of the present update. The first is an extension of the discussion on the Global Warming Potentials (GWP's), including a reevaluation in view of the updates in the lifetimes of the radiatively active species. The second important objective is to underscore major developments in the radiative forcing of climate due to the observed stratospheric ozone losses occurring between 1979 and 1990

Temperature-dependent quantum pair potentials and their application to dense partially ionized hydrogen plasmas

Extending our previous work \cite{filinov-etal.jpa03ik} we present a detailed discussion of accuracy and practical applications of finite-temperature pseudopotentials for two-component Coulomb systems. Different pseudopotentials are discussed: i) the diagonal Kelbg potential, ii) the off-diagonal Kelbg potential iii) the {\em improved} diagonal Kelbg potential, iv) an effective potential obtained with the Feynman-Kleinert variational principle v) the ``exact'' quantum pair potential derived from the two-particle density matrix. For the {\em improved} diagonal Kelbg potential a simple temperature dependent fit is derived which accurately reproduces the ``exact'' pair potential in the whole temperature range. The derived pseudopotentials are then used in path integral Monte Carlo (PIMC) and molecular dynamics (MD) simulations to obtain thermodynamical properties of strongly coupled hydrogen. It is demonstrated that classical MD simulations with spin-dependent interaction potentials for the electrons allow for an accurate description of the internal energy of hydrogen in the difficult regime of partial ionization down to the temperatures of about $60 000$ K. Finally, we point out an interesting relation between the quantum potentials and effective potentials used in density functional theory.Comment: 18 pages, 11 figure

Performance analysis of OFDM and DAB receivers in the presence of spurious tones

A number of mechanisms can result in the generation of spurious tones in Orthogonal Frequency Division Multiplexing (OFDM) receivers. In this work we determine the Signal-to-Noise-Ratio (SNR) degradation at the output of the Fast-Fourier-Transform (FFT) block and evaluate the performance of a Digital Audio Broadcasting (DAB) receiver in the presence of such tonal interference. We show that the degradation varies with the central frequency of the interference and demonstrate that relatively weak spurious tones can compromise the performance of a DAB receiver. We provide specific evaluations of the severity of the above effect for all possible DAB systems parameterizations and evaluate the permissible levels of spurious tones in such systems. It is shown that for DAB EEP Mode A protection level 4, tonal interference of 14 dB lower than the signal can compromise the receiver performance. © 2010 Springer Science+Business Media, LLC