22,708 research outputs found
Recommended from our members
Impacts of Mixed-Wettability on Brine Drainage and Supercritical CO2 Storage Efficiency in a 2.5-D Heterogeneous Micromodel
Geological carbon storage (GCS) involves unstable drainage processes, the formation of patterns in a morphologically unstable interface between two fluids in a porous medium during drainage. The unstable drainage processes affect CO2 storage efficiency and plume distribution and can be greatly complicated by the mixed-wet nature of rock surfaces common in hydrocarbon reservoirs where supercritical CO2 (scCO2) is used in enhanced oil recovery. We performed scCO2 injection (brine drainage) experiments at 8.5 MPa and 45°C in heterogeneous micromodels, two mixed-wet with varying water- and intermediate-wet patches, and one water-wet. The flow regime changes from capillary fingering through crossover to viscous fingering in the micromodels of the same pore geometry but different wetting surfaces at displacement rates with logCa (capillary number) increasing from −8.1 to −4.4. While the mixed-wet micromodel with uniformly distributed intermediate-wet patches yields ~0.15 scCO2 saturation increase at both capillary fingering and crossover flow regimes (−8.1 ≤ logCa ≤ − 6.1), the one heterogeneous wetting to scCO2 results in ~0.09 saturation increase only at the crossover flow regime (−7.1 ≤ logCa ≤ − 6.1). The interconnected flow paths in the former are quantified and compared to the channelized scCO2 flow through intermediate-wet patches in the latter by topological analysis. At logCa > − 6.1 (near well), the effects of wettability and pore geometry are suppressed by strong viscous force. Both scCO2 saturation and distribution suggest the importance of wettability on CO2 storage efficiency and plume shape in reservoirs and capillary leakage through caprock at GCS conditions
Caging phenomena in reactions: Femtosecond observation of coherent, collisional confinement
We report striking observations of coherent caging of iodine, above the B state dissociation threshold, by single collisions with rare gas atoms at room-temperature. Despite the random nature of the solute–solvent interaction, the caged population retains coherence of the initially prepared unbound wave packet. We discuss some new concepts regarding dynamical coherent caging and the one-atom cage effect
Nonlinear ac response of anisotropic composites
When a suspension consisting of dielectric particles having nonlinear
characteristics is subjected to a sinusoidal (ac) field, the electrical
response will in general consist of ac fields at frequencies of the
higher-order harmonics. These ac responses will also be anisotropic. In this
work, a self-consistent formalism has been employed to compute the induced
dipole moment for suspensions in which the suspended particles have nonlinear
characteristics, in an attempt to investigate the anisotropy in the ac
response. The results showed that the harmonics of the induced dipole moment
and the local electric field are both increased as the anisotropy increases for
the longitudinal field case, while the harmonics are decreased as the
anisotropy increases for the transverse field case. These results are
qualitatively understood with the spectral representation. Thus, by measuring
the ac responses both parallel and perpendicular to the uniaxial anisotropic
axis of the field-induced structures, it is possible to perform a real-time
monitoring of the field-induced aggregation process.Comment: 14 pages and 4 eps figure
Effects of Solution, Soil and Sand Cultures on Nodulation and Growth of Phasey Bean
Plants of phasey bean (Macroptilium lathyroides cv. Murray) were grown in nitrogen-free
nutrient solution, sod, or sand culture in a naturally-Nt glasshouse. Nodulation, dry matter accumulation in plant parts, and seed yields were assessed. Partitioning of symbiotic nitrogen into various
plant parts during vegetative and reproductive growth stages was also determined. In all culture
media, nodule number and size increased with plant age but the rate of increase was generally greater
in solution than in the other cultures. In sand culture, the dry weight per nodule and per plant, and
plant growth were significantly suppressed. Although tap root elongation was consistently better in
solution than soil or sand culture, leaf development and dry matter accumulation in roots and stems
were enhanced by solution culture only during flowering and fruiting stage. Seed yields were significantly
increased by solution culture, an effect apparently associated with increased symbiotic nitrogen
fixation. During vegetative growth, nitrogen accumulated largely in the leaves and stems but pods
were major sinks of nitrogen during the reproductive growth stage. The benefits and applications of
solution culture in the study of nodule development and collection of root samples for acetylene reduction
assays are discussed
Theory of the "honeycomb chain-channel" reconstruction of Si(111)3x1
First-principles electronic-structure methods are used to study a structural
model for Ag/Si(111)3x1 recently proposed on the basis of transmission electron
diffraction data. The fully relaxed geometry for this model is far more
energetically favorable than any previously proposed, partly due to the unusual
formation of a Si double bond in the surface layer. The calculated electronic
properties of this model are in complete agreement with data from
angle-resolved photoemission and scanning tunneling microscopy.Comment: 4 pages, 4 figures, submitted to Phys. Rev. Lett (the ugly postscript
error on page 4 has now been repaired
- …