Limitations of a Mapping Algorithm with Fragmentation Mimics (MAFM) when modeling statistical data sources based on measured packet network traffic

Knowing the estimation of a statistical process’s parameters for measured network traffic is very important as it can then be further used for the statistical analyses and modeling of network traffic in simulation tools. It is for this reason that different estimation methods are proposed that allow estimations of the statistical processes of network traffic. One of them is our own histograms comparison (EMHC) based method that can be used to estimate statistical data-length process parameters from measured packet traffic. The main part of EMHC method is Mapping Algorithm with Fragmentation Mimics (MAFM).     

Determination of transient two-dimensional heat transfer in ventilated lightweight low sloped roof using Fourier series

In this paper, the analysis of transient two-dimensional (2D) heat transfer in low sloped roof with forced ventilated cavity made from lightweight building elements (LBE) is presented. For the heat transfer analysis the 2D numerical model, which was verified with experiments, was used. Forced ventilated cavity was configured in two different ways. In the first case the cavity was configured with coloured thin metal sheet and in the second case with thin metal sheet with added layer of thermal insulation and radiation barrier. Beside the influence of the ventilated cavity configuration on the transient 2D heat transfer in the LBE and on the cavity outlet air temperature also the influence of the LBE thickness, specific air flow rate through the cavity, inner air temperature and wind velocity was analysed. Multi-parametric equations for determination of Fourier series coefficients were formed. These coefficients were used for evaluation of transient 2D heat transfer on the inner side of the roof and cavity outlet air temperature for a clear day.     

Schrifttumsberichte

Ohne Zusammenfassung     

Isomorphism,form equivalence and sequence equivalence of PD0L forms

It is shown that if two PD0L forms F₁ and F₂ are form equivalent, i.e., generate the same family of languages, then the PD0L sequences E(F₁) and E(F₂) are isomorphic, provided one of the sequences contains a word of length greater than one. This result leads to a simple algorithm of deciding the form equivalence of two PD0L forms F₁ and F₂. Moreover, we obtain the rather surprising result that F₁ and F₂ are form equivalent if and only if they are sequence equivalent, i.e., generate the same family of PD0L sequences (excluding again the trivial case that F₁ and F₂ generate only words of length one).     

Frequency dependence of the conductivity of amorphous germanium films between 20 Hz and 26 GHz

Conductivity measurements on amorphous Ge films in the frequency range 20 Hz–26 GHz are described. Above 100 MHz the frequency dependence of the conductivity at room temperature satisfied the power law σ∝ω^s with s=0.45-0.7. No saturation of the conductivity was observed. When the Ge films were doped with 0.1–1 at. % Sb the conductivity was frequency independent up to 26 GHz. A.c. hopping conduction seems to be compatible with the experimental results.     

Surface charge and function of cellulose battery separators

The results of zeta-potential determination using the electro-osmotic method in dilute (10^–3 mol dm^–3) solutions of NH₄Cl and ZnCl₂ and diffusion parameters measured in 20% NH₄Cl and 30% ZnCl₂ solutions are presented. In both cases cellulosic membrane separators from different manufacturers, already in practical usage in Leclanché cells, were examined. From the measured data, diffusion potentials were calculated and compared with experimental values. Transport numbers calculated from diffusion potentials are compared to values in free solution (i.e. without a membrane). The relevance of these parameters to the role of cellulosic separators in Leclanché-type cells is briefly discussed.