Long-term drivers of broadband traffic in next-generation networks

This paper is concerned with long-term (20+ years) forecasting of broadband traffic in next-generation networks. Such long-term approach requires going beyond extrapolations of past traffic data while facing high uncertainty in predicting the future developments and facing the fact that, in 20 years, the current network technologies and architectures will be obsolete. Thus, "order of magnitude" upper bounds of upstream and downstream traffic are deemed to be good enough to facilitate such long-term forecasting. These bounds can be obtained by evaluating the limits of human sighting and assuming that these limits will be achieved by future services or, alternatively, by considering the contents transferred by bandwidth-demanding applications such as those using embedded interactive 3D video streaming. The traffic upper bounds are a good indication of the peak values and, subsequently, also of the future network capacity demands. Furthermore, the main drivers of traffic growth including multimedia as well as non-multimedia applications are identified. New disruptive applications and services are explored that can make good use of the large bandwidth provided by next-generation networks. The results can be used to identify monetization opportunities of future services and to map potential revenues for network operators

Small-particle effects in Mössbauer spectra of a carbon-supported iron catalyst

\u3cp\u3eHighly dispersed iron catalysts, consisting of 5 wt % Fe on high-purity carbon black (Carbolac-1), have been studied by in situ Mössbauer spectroscopy at 295, 77, and 4 K. About 75-80% of the iron in the Fe/C-1 catalyst is reduced to α-Fe in H\u3csub\u3e2\u3c/sub\u3e at 740 K, whereas the remaining iron is present as Fe\u3csup\u3e2+\u3c/sup\u3e. The α-Fe particles in reduced Fe/C-1 exhibit behavior characteristic of very small (2 nm) particles. First, the most interesting feature of this work is the occurrence of substantial contributions of superparamagnetic α-Fe in the Mössbauer spectra at 295 and 77 K. Second, the magnetic hyperfine fields of the α-Fe in the spectra at 4 K are enhanced by about 7 kOe, due to the influence of the demagnetizing field in the particle. Third, the effective Debye temperatures of the Fe/C-1 catalysts are much smaller than in iron bulk compounds. Exposure of reduced Fe/C-1 to air results in the oxidation of all iron to Fe\u3csup\u3e3+\u3c/sup\u3e. Carburization in syngas (H\u3csub\u3e2\u3c/sub\u3e/CO = 3) converts all α-Fe in the reduced catalyst to iron carbides, whereas the Fe\u3csup\u3e2+\u3c/sup\u3e remains unaffected. Conversion of the Fe\u3csup\u3e2+\u3c/sup\u3e spectrum from a singlet at room temperature to a doublet at 77 K shows that the unusual ferrous singlet is caused by cancellation of electron and lattice field gradients of opposite sign. The work illustrates the usefulness of in situ Mössbauer spectroscopy at cryogenic temperatures in the investigation of highly dispersed systems.\u3c/p\u3

Oxidative coupling of methane to ethylene with 85% yield in a gas recycle electrocatalytic or catalytic reactor-separator

Methane was oxidatively coupled to ethylene with very high yield in a novel gas recycle reactor-separator operated in a batch or continuous flow mode. The recycled gas passes continuously through a molecular sieve trap in the recycle loop which adsorbs and thus protects from further oxidation a controllable percentage of ethylene and ethane. The products are obtained by subsequent heating of the molecular sieve trap. Ethylene yield up to 85%, i.e. 88% selectivity to ethylene at 97% CH4 conversion, has been obtained in the batch mode of operation using a Ag-Sm2O3 or Ag electrocatalyst and electrochemical supply of oxygen through a ZrO2-Y2O3 solid electrolyte. Using the continuous flow mode of operation with gaseous O-2 supply in the recycle loop and a Sr(1wt%)/La2O3 catalyst we have obtained ethylene yields up to 50%, i.e. 65% C2H4 selectivity at 76% CH4 conversion. The synergy of the catalytic and molecular sieve materials is discussed and modelled in view of the predominantly consecutive nature of the oxidative coupling of methane (OCM) network

The oxidative transformation of methane over the nickel-based catalysts modified by alkali metal oxide and rare earth metal oxide

Two completely different behaviors of the oxidative transformation of methane were performed over the nickel-based catalysts because of the different modifications by alkali metal oxide and rare earth metal oxide and the different interactions between nickel and supports, and two types of catalysts, namely the LiNiLaOx catalyst with a good Oxidative Coupling of Methane (OCM) performance and the LiNiLaOx/Al2O3 supported catalyst with an excellent performance of the Partial Oxidation of Methane to Syngas (POM) reaction were obtained. Several techniques, such as now-reaction, pulse-reaction, XRD, H-2-TPR, XPS, TPO, and TG, etc., were employed to investigate the relation among the preparation and composition of catalysts, the structures of catalysts and the catalytic performances, especially effects of each component, the active phases and their precursors, the redox behaviors and the states of nickel present in those nickel-based catalysts.' The effects of acid-base properties on the states of nickel present and on the directions of the oxidative transformation of methane, the interaction between nickel and other components and the deposition of surface carbon over catalysts were studied. The types of active centers, the modes of the activation of methane and the reaction mechanisms were discussed in detail