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Technico-Economical Evaluation of CO2 Transport in an Adsorbed Phase  [PDF]
Mildred Lemus Perez, Manuel Rodriguez Susa, Mario Pellerano, Arnaud Delebarre
Low Carbon Economy (LCE) , 2012, DOI: 10.4236/lce.2012.31004
Abstract: This work considers the possibility to transport CO2 in an adsorbed phase and analyzes its cost as a function of transported quantities, transport conditions and transportation means. CO2 adsorption capacities of 6 different adsorbents, comprising 4 activated carbons and 2 zeolites, were empirically evaluated in a given range of pressure and temperature. The adsorbent with the highest mass adsorption capacity (AC1), as well as another sorbent described in the literature (AC5) were selected to be used for CO2 transportation by ships, trains or trucks. Their characteristics and performances were then used to develop an economic analysis of transportation costs and CO2 emissions generated by the transport with or without storage. Economic evaluation of CO2 batch transport shows that CO2 transported in an adsorbed phase by train was seen to be almost competitive on distances between 250 and 500 km, in comparison to liquefied CO2. One of the activated carbon appeared to be competitive on short distances by truck when transport was not followed by storage. Ship transport of adsorbed CO2 on distances around 1500 km was competitive, when CO2 was used as delivered; there was an over cost of only 16%, when there was storage after the transport. The CO2 emissions generated by CO2 transport and storage when transport is carried out in an adsorbed phase were smaller than the ones generated by liquid phase transport below 1200 km, 500 km and 300 km by ship, train and truck respectively, as a function of the adsorbent used. Adsorbed CO2 transported on 1500 km by ship generated 27% less CO2 emissions than liquid phase and 17% by train for a distance of 250 km and 16% by truck on 150 km, although these differences were decreasing with the distance of transport.
Transport in chemically doped graphene in the presence of adsorbed molecules  [PDF]
E. H. Hwang,S. Adam,S. Das Sarma
Physics , 2006, DOI: 10.1103/PhysRevB.76.195421
Abstract: Motivated by a recent experiment reporting on the possible application of graphene as sensors, we calculate transport properties of 2D graphene monolayers in the presence of adsorbed molecules. We find that the adsorbed molecules, acting as compensators that partially neutralize the random charged impurity centers in the substrate, enhance the graphene mobility without much change in the carrier density. We predict that subsequent field-effect measurements should preserve this higher mobility for both electrons and holes, but with a voltage induced electron-hole asymmetry that depends on whether the adsorbed molecule was an electron or hole donor in the compensation process. We also calculate the low density magnetoresistance and find good quantitative agreement with experimental results.
TECHNOLOGICAL AND ECONOMICAL STRATEGY OF THE CO2-EXTRACTS PRODUCTION AND APPLICATION Технологическая и экономическая стратегия производства и применения СО2-экстрактов  [PDF]
Malashenko N. L.
Polythematic Online Scientific Journal of Kuban State Agrarian University , 2012,
Abstract: The review of the technological and the economical aspects of the vegetative origin CO2–extracts produc-tion and application has been represented in the article
Dirac Point Resonances, Transport Gaps and Conductance Quantization in Graphene Nanoribbons with Adsorbed Atoms and Molecules  [PDF]
S. Ihnatsenka,G. Kirczenow
Physics , 2010,
Abstract: We present calculations of electronic quantum transport in graphene nanoribbons with adsorbed H, F, OH and O, based on a tight binding model derived from extended Huckel theory. The relaxed atomic geometries of the adsorbates and graphene are calculated using density functional theory. Our model includes the effects of the local rehybridization of the graphene from the sp2 to sp3 electronic structure that occurs when H, F, OH or O bonds covalently to the graphene. It captures the physics of the scattering resonances that are induced in the graphene near the Dirac point by the presence of these adsorbates. We find these Dirac point resonances to play a dominant role in quantum transport in ribbons with these adsorbates: Even at low adsorbate concentrations the conductance of the ribbon is strongly suppressed and a transport gap develops for electron Fermi energies near the resonance. The transport gap is centered very near the Dirac point energy of for H, below it for F and OH and above it for O. We predict ribbons with these adsorbed species under appropriate conditions to exhibit quantized conductance steps of equal height similar to those that have been observed by Lin et al. [Phys. Rev. B 78, 161409 (2008)] at moderately low temperatures, even for ribbons with conductances a few orders of magnitude smaller than 2e2/h.
Audio Cards for High-Resolution and Economical Electronic Transport Studies  [PDF]
Daniel B. Gopman,Daniel Bedau,Andrew D. Kent
Physics , 2012, DOI: 10.1063/1.4709498
Abstract: We report on a technique for determining electronic transport properties using commercially available audio cards. Using a typical 24-bit audio card simultaneously as a sine wave generator and a narrow bandwidth ac voltmeter, we show the spectral purity of the analog-to-digital and digital-to-analog conversion stages, including an effective number of bits greater than 16 and dynamic range better than 110 dB. We present two circuits for transport studies using audio cards: a basic circuit using the analog input to sense the voltage generated across a device due to the signal generated simultaneously by the analog output; and a digitally-compensated bridge to compensate for nonlinear behavior of low impedance devices. The basic circuit also functions as a high performance digital lock-in amplifier. We demonstrate the application of an audio card for studying the transport properties of spin-valve nanopillars, a two-terminal device that exhibits Giant Magnetoresistance (GMR) and whose nominal impedance can be switched between two levels by applied magnetic fields and by currents applied by the audio card.
Kondo effect in transport through molecules adsorbed on metal surfaces: from Fano dips to Kondo peaks  [PDF]
J. M. Aguiar-Hualde,G. Chiappe,E. Louis,E. V. Anda
Physics , 2007, DOI: 10.1103/PhysRevB.76.155427
Abstract: The Kondo effect observed in recent STM experiments on transport through CoPc and TBrPP-Co molecules adsorbed on Au(111) and Cu(111) surfaces, respectively, is discussed within the framework of a simple model (Phys. Rev. Lett. {\bf 97}, 076806 (2006)). It is shown that, in the Kondo regime and by varying the adequate model parameters, it is possible to produce a crossover from a conductance Kondo peak (CoPc) to a conductance Fano dip (TBrPP-Co). In the case of TBrPP-Co/Cu(111) we show that the model reproduces the changes in the shape of the Fano dip, the raising of the Kondo temperature and shifting to higher energies of the dip minimum when the number of nearest neighbors molecules is lowered. These features are in line with experimental observations indicating that our simple model contains the essential physics underlying the transport properties of such complex molecules.
Seasonal and mesoscale variability of oceanic transport of anthropogenic CO2
Z. Lachkar, J. C. Orr,J.-C. Dutay
Biogeosciences (BG) & Discussions (BGD) , 2009,
Abstract: Estimates of the ocean's large-scale transport of anthropogenic CO2 are based on one-time hydrographic sections, but the temporal variability of this transport has not been investigated. The aim of this study is to evaluate how the seasonal and mesoscale variability affect data-based estimates of anthropogenic CO2 transport. To diagnose this variability, we made a global anthropogenic CO2 simulation using an eddy-permitting version of the coupled ocean sea-ice model ORCA-LIM. As for heat transport, the seasonally varying transport of anthropogenic CO2 is largest within 20° of the equator and shows secondary maxima in the subtropics. Ekman transport generally drives most of the seasonal variability, but the contribution of the vertical shear becomes important near the equator and in the Southern Ocean. Mesoscale variabilty contributes to the annual-mean transport of both heat and anthropogenic CO2 with strong poleward transport in the Southern Ocean and equatorward transport in the tropics. This "rectified" eddy transport is largely baroclinic in the tropics and barotropic in the Southern Ocean due to a larger contribution from standing eddies. Our analysis revealed that most previous hydrographic estimates of meridional transport of anthropogenic CO2 are severely biased because they neglect temporal fluctuations due to non-Ekman velocity variations. In each of the three major ocean basins, this bias is largest near the equator and in the high southern latitudes. In the subtropical North Atlantic, where most of the hydrographic-based estimates have been focused, this uncertainty represents up to 20% and 30% of total meridional transport of heat and CO2. Generally though, outside the tropics and Southern Ocean, there are only small variations in meridional transport due to seasonal variations in tracer fields and time variations in eddy transport. For the North Atlantic, eddy variability accounts for up to 10% and 15% of the total transport of heat and CO2. This component is not accounted for in coarse-resolution hydrographic surveys.
Seasonal and mesoscale variability of oceanic transport of anthropogenic CO2  [PDF]
Z. Lachkar,J. C. Orr,J.-C. Dutay
Biogeosciences Discussions , 2009,
Abstract: Estimates of the ocean's large-scale transport of anthropogenic CO2 are based on one-time hydrographic sections, but the temporal variability of this transport has not been investigated. We have evaluated this variability with the aid of an eddy-permitting version of the coupled ocean sea-ice model ORCA-LIM. As for heat transport, the seasonally varying transport of anthropogenic CO2 is largest within 20° of the Equator and shows secondary maxima in the subtropics. Ekman transport generally drives most of the seasonal variability, but the contribution of the vertical shear becomes important near the Equator and in the Southern Ocean. Mesoscale variabilty contributes to the annual-mean transport of both heat and anthropogenic CO2 with strong poleward transport in the Southern Ocean and equatorward transport in the tropics. This "rectified" eddy transport is largely baroclinic in the tropics and barotropic in the Southern Ocean due to a larger contribution from standing eddies. Our analysis revealed that most previous hydrographic estimates of meridional transport of anthropogenic CO2 are severely biased because they neglect temporal fluctuations due to non-Ekman velocity variations. In each of the three major ocean basins, this bias is largest near the Equator and in the high southern latitudes. In the subtropical North Atlantic, where most of the hydrographic-based estimates have been focused, this uncertainty represents up to 20% and 30% of total meridional transport of heat and CO2. Generally though, outside the tropics and Southern Ocean, there are only small variations in meridional transport due to seasonal variations in tracer fields and time variations in eddy transport. For the North Atlantic, eddy variability accounts for up to 10% and 15% of the total transport of heat and CO2. This component is not accounted for in coarse-resolution hydrographic surveys.
The importance of ocean transport in the fate of anthropogenic CO2  [PDF]
L. Cao,M. Eby,A. Ridgwell,K. Caldeira
Biogeosciences Discussions , 2008,
Abstract: We assess uncertainties in projected oceanic uptake of anthropogenic CO2 associated with uncertainties in model ocean transport using a suite of climate/carbon-cycle models. In response to a CO2 pulse emission of 590 Pg C (corresponding to an instantaneous doubling of atmospheric CO2 from 278 to 556 ppm), the fraction of CO2 emitted absorbed by the ocean (model mean ±2σ) is 37±8%, 56±10%, and 81±4% in year 30, 100, and 1000 after the emission pulse, respectively. Modeled oceanic uptake of excess CO2 on timescales from decades to about a century is strongly correlated with simulated present-day uptake of chlorofluorocarbons (CFCs) and anthropogenic CO2, while the amount of excess CO2 absorbed by the ocean from a century to a millennium is strongly correlated with modeled radiocarbon in the deep Southern and Pacific Ocean. The rates of surface-to-deep ocean transport are determined for individual models from the instantaneous doubling CO2 experiments, and they are used to calculate oceanic uptake of CO2 in response to emission pulses of 1000 and 5000 Pg C. These results are compared with simulated oceanic uptake of CO2 from a number of model simulations with the coupling of climate-ocean carbon cycle and without it. This comparison demonstrates that the impact of different ocean transport rate across models on the oceanic uptake of anthropogenic CO2 is of similar magnitude as that of climate-carbon cycle feedbacks in a single model associated with changes in temperature, circulation, and marine biology, emphasizing the importance of ocean transport in the fate of anthropogenic CO2.
Dirac point resonances due to atoms and molecules adsorbed on graphene and transport gaps and conductance quantization in graphene nanoribbons with covalently bonded adsorbates  [PDF]
S. Ihnatsenka,G. Kirczenow
Physics , 2010, DOI: 10.1103/PhysRevB.83.245442
Abstract: We present a tight binding theory of the Dirac point resonances due to adsorbed atoms and molecules on an infinite 2D graphene sheet based on the standard tight binding model of the graphene p-band electronic structure and the extended Huckel model of the adsorbate and nearby graphene carbon atoms. The relaxed atomic geometries of the adsorbates and graphene are calculated using density functional theory. Our model includes the effects of the local rehybridization of the graphene from the sp^2 to sp^3 electronic structure that occurs when adsorbed atoms or molecules bond covalently to the graphene. Unlike in previous tight-binding models of Dirac point resonances, adsorbed species with multiple extended molecular orbitals and bonding to more than one graphene carbon atom are treated. More accurate and more general analytic expressions for the Green's function matrix elements that enter the T-matrix theory of Dirac point resonances than have been available previously are obtained. We study H, F, OH and O adsorbates on graphene and for each we find a strong scattering resonance (two resonances for O) near the Dirac point of graphene, by far the strongest and closest to the Dirac point being the resonance for H. We extract a minimal set of tight binding parameters that can be used to model resonant electron scattering and electron transport in graphene and graphene nanostructures with adsorbed H, F, OH and O accurately and efficiently. We also compare our results for the properties of Dirac point resonances due to adsorbates on graphene with those obtained by others using density functional theory-based electronic structure calculations, and discuss their relative merits. We then present calculations of electronic quantum transport in graphene nanoribbons with these adsorbed species...
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