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Increasing fracture aperture by lowering effective normal stress and by inducing dilatant shearing and thermo-elastic effects is essential for transmissivity increase in enhanced geothermal systems. This study investigates transmissivity evolution for fluid flow through natural fractures in granodiorite at the laboratory scale. Processes that influence transmissivity are changing normal loads, surface deformation, the formation of gouge and fracture offset. Normal loads were varied in cycles between 1 and 68 MPa and cause transmissivity changes of up to three orders of magnitude. Similarly, small offsets of fracture surfaces of the order of millimeters induced changes in transmissivity of up to three orders of magnitude. During normal load cycling, the fractures experienced significant surface deformation, which did not lead to increased matedness for most experiments, especially for offset fractures. The resulting gouge material production may have caused clogging of the main fluid flow channels with progressing loading cycles, resulting in reductions of transmissivity by up to one order of magnitude. During one load cycle, from low to high normal loads, the majority of tests show hysteretic behavior of the transmissivity. This effect is stronger for early load cycles, most likely when surface deformation occurs, and becomes less pronounced in later cycles when asperities with low asperity strength failed. The influence of repeated load cycling on surface deformation is investigated by scanning the specimen surfaces before and after testing. This allows one to study asperity height distribution and surface deformation by evaluating the changes of the standard deviation of the height, distribution of asperities and matedness of the fractures. Surface roughness, as expressed by the standard deviation of the asperity height distribution, increased during testing. Specimen surfaces that were tested in a mated configuration were better mated after testing, than specimens tested in shear offset configuration. The fracture surface deformation of specimen surfaces that were tested in an offset configuration was dominated by the breaking of individual asperities and grains, which did not result in better mated surfaces.

Time crystals are an eagerly sought phase of matter with broken time-translation symmetry. Quantum time crystals with discretely broken time-translation symmetry have been demonstrated in trapped ions, atoms and spins whereas continuously broken time-translation symmetry has been observed in an atomic condensate inside an optical cavity. Here we report that a classical metamaterial nanostructure, a two-dimensional array of plasmonic metamolecules supported on flexible nanowires, can be driven to a state possessing all of the key features of a continuous time crystal: continuous coherent illumination by light resonant with the metamolecules’ plasmonic mode triggers a spontaneous phase transition to a superradiant-like state of transmissivity oscillations, resulting from many-body interactions among the metamolecules, characterized by long-range order in space and time. The phenomenon is of interest to the study of dynamic classical many-body states in the strongly correlated regime and applications in all-optical modulation, frequency conversion and timing.So far, a continuous time crystal has only been implemented on a quantum system. Optically driven many-body interactions in a nanomechanical photonic metamaterial now allow the realization of a classical continuous time crystal.

To understand the influence of shear on the hydraulic properties of rock fractures, shear-flow tests were carried out on rock fractures with different surface roughnesses. Each rough-walled fracture was replicated in four specimens, which were sheared at different displacements under normal stresses that varied from 0.5 to 2.0 MPa. At each shear displacement, a series of hydraulic tests with different hydraulic gradients were performed, and the nonlinear flow regimes of the fluid within the fractures were investigated. The results show that Forchheimer’s law can well describe the nonlinear relationship between the flow rate and the hydraulic gradient in rough-walled fractures. Both the linear coefficient and nonlinear coefficient decrease during shearing but increase as the normal stress increases. The critical hydraulic gradient increases with an increase in the shear displacement and normal stress. With an increase in the joint roughness coefficient, the critical hydraulic gradient decreases. The normalized transmissivity exhibits a strong correlation with the Reynolds number. As the shear displacement increases, the fitted curves of the normalized transmissivity versus the Reynolds number shift upward but the curves shift downward with an increase in normal stress. Additionally, the Forchheimer coefficient decreases with an increase in the shear displacement but increases with an increase in the applied normal stress. Visualization tests show that the number of flow paths is large when the shear displacement is small due to various distributions of the contact areas and that the flow of dyed water over the entire fracture decreases. As the shear displacement increases, the flow resistance decreases due to the shear dilation-induced increase in the aperture, and the advantage channel flow is distinct in the fracture. The contact ratio rapidly decreases as the shear displacement increases from 1 to 3 mm and then slightly varies with a continuously increasing maximum shear displacement of 9 mm.

In this paper, MCNP was used to simulate the shielding efficiency of different shielding materials and the new 3D alloy (an alloy of Ta and W) with different surface densities for the low energy X-ray spectrum (<200keV), and the transmission efficiency of the new 3D alloy with different single energy X-ray spectrum. The simulation results show that the new 3D alloy is a shielding material with high X-ray shielding efficiency, which is approximate to W. The higher the surface density is, the greater the shielding efficiency of the new 3D alloy is. With the increase of energy, the X-ray transmissivity increases. At about 69keV, the transmissivity suddenly decreases to the minimum, and then increases with the increase of energy. And the X-ray transmission verification experiment is designed, and the experimental results are in good agreement with the simulation results.

The complex interplay among several active degrees of freedom (charge, lattice, orbital, and spin) is thought to determine the electronic properties of many oxides. We report on combined ultrafast electron diffraction and infrared transmissivity experiments in which we directly monitored and separated the lattice and charge density reorganizations that are associated with the optically induced semiconductor-metal transition in vanadium dioxide (VO₂). By photoexciting the monoclinic semiconducting phase, we were able to induce a transition to a metastable state that retained the periodic lattice distortion characteristic of the semiconductor but also acquired metal-like mid-infrared optical properties. Our results demonstrate that ultrafast electron diffraction is capable of following details of both lattice and electronic structural dynamics on the ultrafast time scale.

Laboratory fluid flow experiments through hydraulically transmissive fractures in carbonate rocks subjected to mechanical loading and acidizing illuminate how dissolution processes enhance fracture transmissivity. Fracture plane roughness and the size of unmated (i.e., non-contact) regions are critically important. In particular, rough surfaces promote transmissivity enhancement. By contrast, smoother surfaces with higher levels of matedness and contact areas between the opposing fracture planes remain unaffected by chemical degradation. Such surfaces do not illuminate relevant mechanical variations. Grain-supported rocks with high calcium contents and rough surfaces show the most significant increase in fracture transmissivity after acidizing. Contrastingly, fracture transmissivity after acid treatment in matrix-supported rocks with high calcium contents is low, even in samples with rough fractures and unmated surfaces. These results inform geochemical models in the presence of acid injection and make hydrocarbon reservoir simulations more robust. Moreover, these results provide valuable insights and trends for understanding the interaction of rocks with other types of reactive fluids, such as carbon dioxide.HighlightsLaboratory flow experiments along fractures in carbonate rocks illuminate how mineralogy and stress impact dissolution processes and transmissivity.Fracture plane roughness and the size of non-contact area between opposing surfaces play a critical role for flow behavior.Evolution of fracture transmissivity following acidification is further governed by mineralogy along fracture surfaces.

Rock weathering fractures in nature are complex and fracture healing is an effective strategy for rock weathering mitigation. This study is a first attempt to apply microbially induced calcium carbonate precipitation (MICP) technology in the healing of nature-weathering-like rough fractures (NWLRF). Sandstone was studied as an example due to its wide distribution as construction, sculpture and monument materials all over the world. To achieve a high healing efficiency, a repeated mixture injection strategy was proposed. Based on a series of laboratory MICP injection experiments on four types of NWLRF, we systematically explored the fundamental micro-healing mechanism and the influence factors including fracture aperture, characteristics of branch fractures, and cementation solution concentration. Experimental results demonstrated that MICP healing with the repeated mixture injection strategy had the ability to efficiently heal the penetrated NWLRF well with length in centimeter scale and aperture in millimeter scale, but cannot heal the non-penetrated branch fractures under low injection pressure. The repeated mixture injection strategy furtherly achieved a high apparent fracture healing ratio and a significant reduction of transmissivity. The apparent fracture healing ratios of all main fractures were higher than 80% and the maximum was 96.3%. Fracture transmissivity was reduced by at least three orders of magnitude from about 1 × 10–4 m2/s to less than 1 × 10–7 m2/s, and the highest reduction reached to four orders of magnitude. For the aspect of the effects, larger cementation solution concentration, finer aperture and penetrated branch fracture were beneficial to improve the healing effect. Moreover, the MICP healing mechanism with high fracture healing ratio and significant reduction of transmissivity on sandstone NWLRF was also analyzed. The research results have important theoretical significance and technical guidance value for the disaster prevention and mitigation of rock weathering.

Greening—increasing leaf area index—affects regional climate in a number of contradictory ways. The net global effect is now revealed to be cooling that has offset the equivalent of 12% of global land-surface warming over the past 30 years. The surface air temperature response to vegetation changes has been studied for the extreme case of land-cover change 1 , 2 , 3 , 4 , 5 ; yet, it has never been quantified for the slow but persistent increase in leaf area index (LAI) observed over the past 30 years (Earth greening) 6 , 7 . Here we isolate the fingerprint of increasing LAI on surface air temperature using a coupled land–atmosphere global climate model prescribed with satellite LAI observations. We find that the global greening has slowed down the rise in global land-surface air temperature by 0.09 ± 0.02 °C since 1982. This net cooling effect is the sum of cooling from increased evapotranspiration (70%), changed atmospheric circulation (44%), decreased shortwave transmissivity (21%), and warming from increased longwave air emissivity (−29%) and decreased albedo (−6%). The global cooling originated from the regions where LAI has increased, including boreal Eurasia, Europe, India, northwest Amazonia, and the Sahel. Increasing LAI did not, however, significantly change surface air temperature in eastern North America and East Asia, where the effects of large-scale atmospheric circulation changes mask local vegetation feedbacks. Overall, the sum of biophysical feedbacks related to the greening of the Earth mitigated 12% of global land-surface warming for the past 30 years.

Atmospheric transmissivity (τ) is a critical factor in climatology, which affects surface energy balance, measured at a limited number of meteorological stations worldwide. With the limited availability of meteorological datasets in remote areas across different climatic regions, estimation of τ is becoming a challenging task for adequate hydrological, climatic, and crop modeling studies. The availability of solar radiation data is comparatively less accessible on a global scale than the temperature and precipitation datasets, which makes it necessary to develop methods to estimate τ. Most of the previous studies provided region specific datasets of τ, which usually provide local assessments. Hence, there is a necessity to give the empirical models for τ estimation on a global scale that can be easily assessed. This study presents the analysis of the τ relationship with varying geographic features and climatic factors like latitude, aridity index, cloud cover, precipitation, temperature, diurnal temperature range, and elevation. In addition to these factors, the applicability of these relationships was evaluated for different climate types. Thus, empirical models have been proposed for each climate type to estimate τ by using the most effective factors such as cloud cover and aridity index. The cloud cover is an important yet often overlooked factor that can be used to determine the global atmospheric transmissivity. The empirical relationship and statistical indicator provided the best performance in equatorial climates as the coefficient of determination (r2) was 0.88 relatively higher than the warm temperate (r2 = 0.74) and arid regions (r2 = 0.46). According to the results, it is believed that the analysis presented in this work is applicable for estimating the τ in different ecosystems across the globe.

Perovskite/organic tandem solar cells (PO-TSCs) exploit the advantages of cost-effective fabrication, orthogonal solvent processing for perovskite and organic absorber layers, and compatibility with low-temperature, high-throughput deposition techniques. However, their performance remains hampered by energy losses of subcells and interconnecting layers (ICLs). Here, an energy loss management strategy for PO-TSCs is proposed, focusing on the simultaneous regulation of defect states in perovskite front subcells and the reduction of optical and electrical losses in the ICL. The synergistic effect of hydrogen bonding and coordination interactions between the pyridinium bromide perbromide and perovskite layer effectively mitigates ion migration, thereby minimizing energy losses. Meanwhile, the optimized V 2 O 5 -based ICL structure not only demonstrates excellent transmissivity for near-infrared photons but also allows for barrier-free extraction of charge carriers. Such structure can provide a low-loss interface, facilitating light management within the bulk heterojunction, which effectively balances the current between the front and rear subcells. Taken together, the resulting PO-TSCs deliver a power conversion efficiency of 25.1% with a high open-circuit voltage of 2.10 V. The performance of perovskite/organic tandem solar cells remains hampered by the energy losses of subcells and interconnecting layers (ICLs). Here, authors introduce pyridinium bromide perbromide into perovskites and employ a V 2 O 5 -based ICL, achieving a maximum efficiency of 25.1% in tandem devices.