Sabatier-based CO2-methanation by catalytic conversion     

K. Müller  M. Städter  F. Rachow  D. Hoffmannbeck  D. Schmeißer 《Environmental Earth Sciences》2013,70(8):3771-3778

The catalytic conversion of CO₂ is an important component for the reintegration of secondary products like CO₂ or H₂ into the energy supply. An example is the “power to gas” concept with a conversion of CO₂ into CH₄. The CO₂ is transferred into a carrier of chemical energy, with the possibility to feed the produced CH₄ into the existing network of natural gas. At temperatures of around 350 °C, hydrogenation of CO₂ to CH₄ is possible by the Sabatier reaction CO₂ + 4H₂ → CH₄ + 2H₂O. One prerequisite for efficient kinetics of the Sabatier reaction is the application and optimization of catalysts. The focus of catalyst development is given to their performance under the conditions to be expected in the special application. As a part of the project Geoenergy-Research (GeoEn), we address questions related to the catalytic utilization of CO₂ produced in the course of the oxyfuel combustion of lignite. In this contribution, we report on the experimental setup in laboratory scale, which enables an advanced characterization of the catalytic performance, including thermodesorption measurements at atmospheric pressure in order to determine the amount of adsorbed CO₂ under real conditions. We also show data for activation energies, the catalytic performance as function of temperature and the long time stability of a commercial Ru-based catalyst.  相似文献   

Impacts of the use of the geological subsurface for energy storage: an investigation concept     

Sebastian Bauer  Christof Beyer  Frank Dethlefsen  Peter Dietrich  Rainer Duttmann  Markus Ebert  Volker Feeser  Uwe Görke  Ralf Köber  Olaf Kolditz  Wolfgang Rabbel  Tom Schanz  Dirk Schäfer  Hilke Würdemann  Andreas Dahmke 《Environmental Earth Sciences》2013,70(8):3935-3943

  相似文献   

A mineralogical and geochemical study of polymict eucrite discovered in Sahara of southwest Algeria     

Abdelmadjid Seddiki  Bertrand Moine  Jean Yves Cottin  Jérôme Bascou  Marguerite Godard  François Faure  Michèle Bourot-Denise  Nacera Remaci 《Arabian Journal of Geosciences》2013,6(9):3175-3184

NWA2268 is a polymict eucrite discovered in the Sahara, at southwest Algeria, close to the region of Tindouf. This meteorite weighs 65 g and presents a thin black fusion crust. The rock is fine- to medium-grained breccia and contains mineral fragments of plagioclases, pyroxenes, spinel, olivine and silica. The rock contains some basaltic fragments with sub-ophitic or cumulative textures, constituted by plagioclases and exsolved pigeonite. Pyroxferroite grains are present and locally destabilised in an association of hedenbergite, fayalite and silica. It also presents unequilibrated eucritic clast with heterogeneous pyroxenes and plagioclases compositions. Pyroxenes in the all of the other clasts have equilibrated composition, with exolved pigeonites with augite lamellaes. This polymict eucrite contains also partially devitrified glass that represents impact melts linked to impact event. None recrystallization of this glass confirms a lack of post-brecciation metamorphism. Diogenitic fragments are less abundant than 10 %. The oxygen isotopic composition of NWA2268 is Δ¹⁷O (?0.43). This meteorite is interpreted as belonging to the HED group attributed to the 4-Vesta asteroid.  相似文献   

Linear modelling in vertical ionospheric sounding     

Jaromír Bordovský  Reviewer M. Šisler  Reviewer V. Fiala 《Studia Geophysica et Geodaetica》1989,33(3):268-286

Summary Applying the methods of computing N(h) profiles to scalar product spaces provides a more general view of the differences between the individual ionospheric models, which enables a better selection of the optimum model.

---

u n¶rt; m¶rt;uu ama N(h) nu nmama a nu¶rt;u anauam u ¶rt; a au ¶rt; m¶rt;u uu ¶rt;u, m nm nmm uam nmua ¶rt;.

  相似文献   

A survey of possible effects of long-lasting absence of solar activity on climate and some speculations on possible mechanisms   总被引：1，自引：0，他引：1  

G. Y. Molnár 《Climatic change》1981,3(2):189-203

This paper deals with the prolonged lack (or existence) of solar activity, such as the Maunder or Spörer minima, since considerable climatic changes barely occur within a shorter time interval. For this aim, first the possible influences of the present-day 11-yr solar cycle are considered for higher atmospheric regions, and found scarcely to be responsible for inducing climatic changes. On the other hand, solar activity-generated changes of the solar parameter in the visible spectrum are estimated too. The results of these simple considerations indicate that the external manifestations of the solar cycle hardly can cause observable change in the tropospheric weather (and so the long-lasting solar quiets seem not climatically significant), and seem indirectly to support the possibility, that the Milankovitch mechanism plays an important role in forcing the ice-age oscillations at least during the Quaternary period. Besides it can be concluded, that greater (≥ 0.1%, measured from satellite platform) solar parameter variations cannot be in close connection with the known forms of solar activity, which suggest that the possible, significant secular solar luminosity changes could be generated deep inside the Sun and/or could not be closely related to the sunspot cycle.  相似文献   

Initiation of Coronal Mass Ejections by Sunspot Rotation     

T. Török  M. Temmer  G. Valori  A. M. Veronig  L. van Driel-Gesztelyi  B. Vršnak 《Solar physics》2013,286(2):453-477

We study a filament eruption, two-ribbon flare, and coronal mass ejection (CME) that occurred in NOAA Active Region 10898 on 6 July 2006. The filament was located South of a strong sunspot that dominated the region. In the evolution leading up to the eruption, and for some time after it, a counter-clockwise rotation of the sunspot of about 30 degrees was observed. We suggest that the rotation triggered the eruption by progressively expanding the magnetic field above the filament. To test this scenario, we study the effect of twisting the initially potential field overlying a pre-existing flux-rope, using three-dimensional zero-β MHD simulations. We first consider a relatively simple and symmetric system, and then study a more complex and asymmetric magnetic configuration, whose photospheric-flux distribution and coronal structure are guided by the observations and a potential field extrapolation. In both cases, we find that the twisting leads to the expansion of the overlying field. As a consequence of the progressively reduced magnetic tension, the flux-rope quasi-statically adapts to the changed environmental field, rising slowly. Once the tension is sufficiently reduced, a distinct second phase of evolution occurs where the flux-rope enters an unstable regime characterised by a strong acceleration. Our simulations thus suggest a new mechanism for the triggering of eruptions in the vicinity of rotating sunspots.  相似文献   

Multi-Waveband Emission Maps of Blazars     

Alan Marscher  Svetlana G. Jorstad  Valeri M. Larionov  Margo F. Aller  Anne Lähteenmäki 《Journal of Astrophysics and Astronomy》2011,32(1-2):233-237

We are leading a comprehensive multi-waveband monitoring program of 34 γ-ray bright blazars designed to locate the emission regions of blazars from radio to γ-ray frequencies. The ‘maps’ are anchored by sequences of images in both total and polarized intensity obtained with the VLBA at an angular resolution of ～0.1 milliarcseconds. The time-variable linear polarization at radio to optical wavelengths and radio to γ-ray light curves allow us to specify the locations of flares relative to bright stationary features seen in the images and to infer the geometry of the magnetic field in different regions of the jet. Our data reveal that some flares occur simultaneously at different wavebands and others are only seen at some of the frequencies. The flares are often triggered by a superluminal knot passing through the stationary ‘core’ on the VLBA images. Other flares occur upstream or even parsecs downstream of the core.  相似文献   

The orbital and superhump periods of the dwarf nova HS 0417+7445 in Camelopardalis     

J.H. Shears  B.T. Gänsicke  S. Brady  P. Dubovský  I. Miller  B. Staels 《New Astronomy》2011,16(5):311-316

We present the 2005–2010 outburst history of the SU UMa-type dwarf HS 0417+7445, along with a detailed analysis of extensive time-series photometry obtained in March 2008 during the second recorded superoutburst of the system. The mean outburst interval is 197 ± 59 d, with a median of 193 d. The March 2008 superoutburst was preceded by a precursor outburst, had an amplitude of 4.2 magnitudes, and the whole event lasted about 16 days. No superhumps were detected during the decline from the precursor outburst, and our data suggests instead that orbital humps were present during that phase. Early superhumps detected during the rise to the superoutburst maximum exhibited an unusually large fractional period excess of ? = 0.137 (P_sh = 0.0856(88) d). Following the maximum, a linear decline in brightness followed, lasting at least 6 days. During this decline, a stable superhump period of P_sh = 0.07824(2) d was measured. Superimposed on the superhumps were orbital humps, which allowed us to accurately measure the orbital period of HS 0417+7445, P_orb = 0.07531(8) d, which was previously only poorly estimated. The fractional superhump period excess during the main phase of the outburst was ? = 0.037, which is typical for SU UMa dwarf novae with similar orbital period. Our observations are consistent with the predictions of the thermal-tidal instability model for the onset of superoutbursts, but a larger number of superoutbursts with extensive time-series photometry during the early phases of the outburst would be needed to reach a definite conclusion on the cause of superoutbursts.  相似文献   

CTBT seismic monitoring using coherent and incoherent array processing     

Kværna  Tormod  Gibbons  Steven J.  Näsholm  Sven Peter 《Journal of Seismology》2021,25(5):1189-1207

Journal of Seismology - The detection and location capability of the International Monitoring System for small seismic events in the continental and oceanic regions surrounding the Sea of Japan is...  相似文献   

Trends and variability of ocean waves under RCP8.5 emission scenario in the Mediterranean Sea     

De Leo  Francesco  Besio  Giovanni  Mentaschi  Lorenzo 《Ocean Dynamics》2021,71(1):97-117

Ocean Dynamics - Wind-generated ocean waves are key inputs for several studies and applications, both near the coast (coastal vulnerability assessment, coastal structures design, harbor...  相似文献