142 research outputs found
The influence of heterogeneous structure on salt precipitation during CO2 geological storage
The presence of rock heterogeneity and fractures may cause abrupt spatial changes in capillary action and flow characteristics, which eventually change the precipitation behavior during CO2 geological storage. Therefore, the salt precipitation mechanism of the heterogeneous structure needs to be studied. In this paper, the salt precipitation behavior in different heterogeneous structures was studied through pore-scale experiments at room temperature and atmospheric conditions. In the up-down heterogeneous structure, the salt precipitation has little effect on the injectivity regardless of the CO2 injection rate. When the CO2 injection rate is low, the salt tends to precipitate in situ in the small pore structure to form a crystal structure. When the CO2 injection rate is high, the salt tends to precipitate in the large pore structure to form a cluster structure. In the left-right heterogeneous structure, regardless of the CO2 injection rate, the precipitated salt is mainly in the cluster structure, and the salt is more dispersed in distribution, the impact on injectivity is small. The injection well can be selected in the formation with strong heterogeneity, to alleviate the blockage caused by salt precipitation. When CO2 leaks in the fractures, salt tends to grow until the fracture is plugged, which is of great significance for the self-healing of the fracture for the caprock.Cited as: He, D., Jiang, P., Xu, R. The influence of heterogeneous structure on salt precipitation during CO2 geological storage. Advances in Geo-Energy Research, 2023, 7(3): 189-198. https://doi.org/10.46690/ager.2023.03.0
Comparison of volume-average simulation and pore-scale simulation of thermal radiation and natural convection in high temperature packed beds
The phenomenon of natural convection and thermal radiation heat transfer in fluid-saturated high temperature packed beds has been widely studied due to its various applications ranging from solar collectors to high temperature gas cooled reactor. With the local thermal non-equilibrium model, the majority of the numerical simulation studies on natural convection and radiation heat transfer in fluid-saturated porous media have limits. In these studies the internal heat transfer coefficients have always been calculated as the existing formulas, which were obtained by the experiments of forced convection in porous media [1-2]. However, natural convection heat transfer in porous media is dominated by the temperature difference between solid particles and fluid, which is different with the forced convection in porous media. For thermal radiation in porous media, the Rosseland diffusion approximation model has always been used in simulations by researchers [3-4], in which the mean absorption coefficient are not calculated according to the experiments and need to be determined by ray-tracing Monte Carlo simulations. Based on high temperature packed pebble beds, this study is aimed to compare the volume-averaged simulations and pore-scale simulations of high temperature packed beds, and predict the effective thermal conductivities of packed beds with temperature up to 1600℃. The effective thermal conductivities of the pebble beds under different temperatures are essential parameters in simulation models to analyze the maximum fuel temperature and temperature distribution in the reactor core in the reactor safety analysis. The SANA test facility was installed at the Research Centre, Julich in Germany specifically to investigate the heat transport mechanisms inside the core of a high temperature gas cooled reactor (HTGR). The validation of the volume-averaged approach and pore-scale approach are based on the experimental data of SANA test [5]. In high temperature helium-saturated annular packed pebble bed, the inner wall has a heat source and the outer wall is isothermally cooled at a lower temperature. The top and bottom walls are kept adiabatic. In the volume-averaged simulations, local thermal non-equilibrium model with the revised internal heat transfer coefficients and radiative heat flux is applied as the energy equation, and no uniform porosity distribution is used. To describe the random packed structure, PFC 3D software is used to simulate the spheres packing, which is used for direct pore-scale numerical simulations. Natural convection and thermal radiation in a 2D circular cross section of the annular pebble bed have been carried out. The effective thermal conductivities and temperature distributions of volume-averaged and pore-scale simulations of the high temperature helium-saturated annular packed pebble bed are corresponded well with the existed experimental data with temperature below 1000℃, and predict the effective thermal conductivities of the pebble bed core with temperature up to 1600℃, which are vital references for thermal hydraulic designs of high temperature gas cooled reactor core
Miscible density driven convective mass transfer process analysis based on Entransy dissipation theory
Density driven convective mass transfer process in porous media is one of the most universal phenomena in underground aquifer. In this study, an original model defining Nu (or Sh) number for miscible mass transfer system was derived, based on basic concept of integrated entransy dissipation rate. Numerical simulation results of density driven convective mass transfer process in a closed Hele-Shaw cell and porous media are analyzed. In the process of dilute brine-water mass transfer system in Hele-Shaw cell, three different stages were observed. Meanwhile, time dependent entransy variation and Nu number using our definition also show three different steps in accordance with the observing phenomenon which are perturbation growing stage, instable mass transfer stage and stabilized stage. Very different fingering patterns were observed in dilute brine-water system and PEG-Water system because the latter one has not only the Non-Monotonic Density-Concentration profile but also the strong dependence of viscosity on concentration which can cause viscous-instability accompanied with density driven instability
Slider-Block Friction Model for Landslides: Application to Vaiont and La Clapiere Landslides
Accelerating displacements preceding some catastrophic landslides have been
found empirically to follow a time-to-failure power law, corresponding to a
finite-time singularity of the velocity [{\it Voight},
1988]. Here, we provide a physical basis for this phenomenological law based on
a slider-block model using a state and velocity dependent friction law
established in the laboratory and used to model earthquake friction. This
physical model accounts for and generalizes Voight's observation: depending on
the ratio of two parameters of the rate and state friction law and on the
initial frictional state of the sliding surfaces characterized by a reduced
parameter , four possible regimes are found. Two regimes can account for
an acceleration of the displacement. We use the slider-block friction model to
analyze quantitatively the displacement and velocity data preceding two
landslides, Vaiont and La Clapi\`ere. The Vaiont landslide was the catastrophic
culmination of an accelerated slope velocity. La Clapi\`ere landslide was
characterized by a peak of slope acceleration that followed decades of ongoing
accelerating displacements, succeeded by a restabilizing phase. Our inversion
of the slider-block model on these data sets shows good fits and suggest to
classify the Vaiont (respectively La Clapi\`ere) landslide as belonging to the
velocity weakening unstable (respectively strengthening stable) sliding regime.Comment: shortened by focusing of the frictional model, Latex document with
AGU style file of 14 pages + 11 figures (1 jpeg photo of figure 6 given
separately) + 1 tabl
Non-monotonicity of the frictional bimaterial effect
Sliding along frictional interfaces separating dissimilar elastic materials
is qualitatively different from sliding along interfaces separating identical
materials due to the existence of an elastodynamic coupling between interfacial
slip and normal stress perturbations in the former case. This bimaterial
coupling has important implications for the dynamics of frictional interfaces,
including their stability and rupture propagation along them. We show that
while this bimaterial coupling is a monotonically increasing function of the
bimaterial contrast, when it is coupled to interfacial shear stress
perturbations through a friction law, various physical quantities exhibit a
non-monotonic dependence on the bimaterial contrast. In particular, we show
that for a regularized Coulomb friction, the maximal growth rate of unstable
interfacial perturbations of homogeneous sliding is a non-monotonic function of
the bimaterial contrast, and provide analytic insight into the origin of this
non-monotonicity. We further show that for velocity-strengthening
rate-and-state friction, the maximal growth rate of unstable interfacial
perturbations of homogeneous sliding is also a non-monotonic function of the
bimaterial contrast. Results from simulations of dynamic rupture along a
bimaterial interface with slip-weakening friction provide evidence that the
theoretically predicted non-monotonicity persists in non-steady, transient
frictional dynamics.Comment: 14 pages, 5 figure
Identification of pathogenic mutations for a Wolfram syndrome pedigree by whole exome sequencing and analysis of its clinical characteristics
Objective·To identify the causative gene and mutations and describe the clinical traits in a Chinese diabetes pedigree suspected of Wolfram syndrome.Methods·A total of 12 subjects from one family were included. The proband was admitted to the Department of Endocrinology, The First Affiliated Hospital of Xinxiang Medical University, for the first time in May 2013. Then he visited the hospital for follow-up in July 2022 and in April 2023, respectively. The other members of this family included the proband′s sister, father, mother, paternal grandfather, paternal grandmother, uncle, aunt, as well as maternal grandfather, maternal grandmother, and two brothers of the proband′s mother. Clinical data of all subjects were collected. The whole exome sequencing was used to screen the pathogenic genes and mutation sites of six members of the family, and Sanger sequencing was used to verify the above results. Effects of the mutation of the pathogenic gene WFS1 in Wolfram syndrome on the function of the wolframin protein were evaluated by bioinformatics softwares, including CADD, DANN, MetaSVM, Polyphen-2, SIFT and M-CAP. The three-dimensional structures of wild-type and mutant wolframin proteins were constructed with Swiss-Model software, and visualized with PyMOL software. Cluster Omega software was used for evaluating species conservation of WFS1 gene mutation sites. JNetPRED software was used for online prediction of wolframin protein secondary structure.Results·The proband and his sister both carried R558H and S411Cfs*131 mutations, two compound heterozygous mutations of the Wolfram syndrome pathogenic gene WFS1. The proband′s father and parental grandfather both carried the R558H mutation, while the proband′s mother and maternal grandfather both carried the S411Cfs*131 mutation. The R558H mutation was a rare missense mutation, and the S411Cfs*131 mutation was a novel frameshift mutation. Bioinformatics analysis softwares predicted that the R558H mutation located in the α-helical structure of the wolframin protein. This mutation was a damage mutation and the amino acid sequence of the mutation region was highly conservative among 12 species with varying degrees of evolution, including humans.Conclusion·Two causative mutations of WFS1 gene are identified in a Chinese diabetes pedigree by whole exome sequencing. The study supplements the existing genotype and phenotype profiles of Wolfram syndrome, which can realize early diagnosis of diabetes pedigrees and help in performing timely follow-up of patients, so as to achieve early intervention and treatment of this disease
Acoustic radiation controls friction: Evidence from a spring-block experiment
Brittle failures of materials and earthquakes generate acoustic/seismic waves
which lead to radiation damping feedbacks that should be introduced in the
dynamical equations of crack motion. We present direct experimental evidence of
the importance of this feedback on the acoustic noise spectrum of
well-controlled spring-block sliding experiments performed on a variety of
smooth surfaces. The full noise spectrum is quantitatively explained by a
simple noisy harmonic oscillator equation with a radiation damping force
proportional to the derivative of the acceleration, added to a standard viscous
term.Comment: 4 pages including 3 figures. Replaced with version accepted in PR
Earthquakes: from chemical alteration to mechanical rupture
In the standard rebound theory of earthquakes, elastic deformation energy is
progressively stored in the crust until a threshold is reached at which it is
suddenly released in an earthquake. We review three important paradoxes, the
strain paradox, the stress paradox and the heat flow paradox, that are
difficult to account for in this picture, either individually or when taken
together. Resolutions of these paradoxes usually call for additional
assumptions on the nature of the rupture process (such as novel modes of
deformations and ruptures) prior to and/or during an earthquake, on the nature
of the fault and on the effect of trapped fluids within the crust at
seismogenic depths. We review the evidence for the essential importance of
water and its interaction with the modes of deformations. Water is usually seen
to have mainly the mechanical effect of decreasing the normal lithostatic
stress in the fault core on one hand and to weaken rock materials via
hydrolytic weakening and stress corrosion on the other hand. We also review the
evidences that water plays a major role in the alteration of minerals subjected
to finite strains into other structures in out-of-equilibrium conditions. This
suggests novel exciting routes to understand what is an earthquake, that
requires to develop a truly multidisciplinary approach involving mineral
chemistry, geology, rupture mechanics and statistical physics.Comment: 44 pages, 1 figures, submitted to Physics Report
A nonplanar slow rupture episode during the 2000 Miyakejima dike intrusion
Magmatic intrusions release extensional strain in the Earth's crust upon availability of magma. Intrusions are typically accompanied by earthquake swarms and by surface faulting that is often larger than what is expected from the magnitude of the induced earthquakes. The 2000 Miyakejima dike intrusion triggered the largest volcanic earthquake swarm monitored so far, with five Ml>6 earthquakes. We analyze the seismicity and deformation induced by the Miyakejima dike with the aim of constraining the timescale and mechanisms of slow strain release during the episode. In six earthquake bursts lasting few hours and migrating at 3c1 km h 121 we find candidates for slow earthquakes. Each burst nucleated at the tips of previous bursts, suggesting stress interaction. The variability of fault plane solutions indicates that the bursts occurred on a complex system of fractures, consistent with weakly consolidated surface layers strained by spatially inhomogneous stresses that change in time, such as those induced by a dike. Based on dislocation models, we find that deformation is best explained by aseismic slip (in addition to the seismic burst), with a moment 1.3 to 2.3 times larger than the earthquakes' seismic moment, and opening of 0.20 \ub1 0.07 m on the dike. The aseismic slip occurred over a few hours, with moment, duration, and migration velocity consistent with that of previously observed slow slip events. We argue that the seismic bursts are likely driven by slow slip, sharing most properties with tectonic slow slip events and swarms, but occurring on a set of nonaligned faults
MicroRNA-24 inhibits growth, induces apoptosis, and reverses radioresistance in laryngeal squamous cell carcinoma by targeting X-linked inhibitor of apoptosis protein
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