Analytical solution and numerical verification for a pressure-relief method of circular tunnel

This paper presents an elastic analytical solution to a circular tunnel with releasing slots at high stress areas near the hole by using a conformal mapping method and the complex variable theory. Compared to the original stress distribution around the circular hole, the releasing effect on elastic stresses is evaluated. After grooving slots, low stress area is generated where the high stress concentration is located. This is agreeable with what was predicted by the finite difference FLAC2D . Besides, displacements are obtained along the periphery of the released hole and are in accordance with those of FLAC2D . In addition to the intersection of the mapping contour, the influences of the sampling points distribution, series number in mapping function, and slot shape are discussed. It is inevitable that the mapping accuracies for the slot and the circle cannot be satisfied at the same time The mapping effect on the circle has to be considered primarily since the stress distribution around the circle is much more significant than the tunnel stability. The analytical solution can be available and fast method of estimating the releasing effect of the application on the tunnel without rock parameters

Research progress on the role of vitamin D supplementation in adjuvant therapy for COVID-19

The pandemic caused by coronavirus disease of 2019 （COVID-19） has brought severe challenges to public health all over the world. Vitamin D plays an important role in immune regulation and anti-respiratory virus infection as an immune enhancer. Several studies have demonstrated that vitamin D can regulate the angiotensin-converting enzyme 2/angiotensin （1-7）/Mas receptor axis signaling pathway， inhibit the over-activation of renin-angiotensin system signal， fight against SARS-CoV-2 infection and suppress the production of inflammatory cytokine storm， thereby reducing the risk of pneumonia infection and improving acute respiratory distress syndrome， cardiogenic obstruction and thrombosis in COVID-19 patients. In this article， the mechanism of vitamin D in reducing the risk of SARS-CoV-2 infection and mitigating clinical symptoms was reviewed. It is hypothesized that vitamin D plays a critical role in the prevention or adjuvant therapy for novel coronavirus pneumonia and alleviating clinical manifestations in COVID-19 patients

Valorizing Rice Straw and Its Anaerobically Digested Residues for Biochar to Remove Pb(II) from Aqueous Solution

To seek a new path to valorize rice straw (RS) and its anaerobically digested residues (DRS), biochar production at different temperatures for removing Pb(II) from aqueous solution and its basic physicochemical characteristics for elucidating potentially adsorption mechanisms were investigated. Overall, pH, electrical conductivity (EC), ash, specific surface area (SA), micronutrient content, and aromaticity of RS biochars (RSBCs) and DRS biochars (DRSBCs) increased with the promoted pyrolysis temperature, and opposite trends were found on the yield, volatile matter, H, N, and O. Lower pH and K content but higher yield, carbon stability, and N and P content were achieved by DRSBCs. Consequently, DRSBCs exhibited lower Pb(II) removal, which was 0.15–0.35 of RSBCs. Maximum adsorption capacities of 276.3 and 90.5 mg·g−1 were achieved by RSBC and DRSBC, respectively, at 500°C. However, distinct mechanisms dominated Pb(II) removal, in which carbonates and carboxylates were responsible for RSBCs, and phosphate silicate precipitation and complexation with carboxylate groups controlled DRSBCs

How does in situ stress rotate within a fault zone? Insights from explicit modeling of the frictional, fractured rock mass

We quantitatively investigate the spatial stress variations within fault zones by explicitly incorporating macroscopic fracture networks in a multilayer fault zone model. Based on elastic crack theory, we first derive a unified constitutive relationship for frictional fractures, featuring elastic and plastic shear deformation and shear-induced normal dilatancy. To honor the progressively accumulated damage across a fault zone, we establish a fractured multilayer model including randomly-oriented frictional fractures with varying densities from layer to layer. Under the specific boundary conditions of a fault zone, the global mechanical response of each layer is quantitatively related to the deformation of the interior fractures. Stress variations and effective elastic property changes are systematically studied considering the influences of fracture properties and pore pressure. We show that the major principal stress always rotates toward a limiting angle of 45 with respect to the fault slip direction and that differential stress invariantly decreases with the fracture density. However, mean stress increases for an unfavorably-oriented fault and decreases when the regional major principal stress trends at a small angle (< 45°) to the fault slip direction. Accumulated damage also results in a decrease and increase in the effective Young’s modulus and Poisson’s ratio, respectively. The influences of fracture properties, pore pressure and fracture network can be attributed to their control on the fracture deformation components and relative proportion. Our model can predict continuous variations of stresses and effective elastic properties from intact country rock, through fractured damage zone, to the plastic fault core of a mature fault

Global Frictional Equilibrium via Stochastic, Local Coulomb Frictional Slips

Natural variability of fault friction and slip uncertainty exist in the Earth&rsquo;s crust. To what extent it influences crustal stress and its evolution is intriguing. We established a quasi-static, 2D model to simulate the stress evolution due to Coulomb frictional slips in the brittle crust. The model simply features randomly-oriented fractures with heterogeneous frictional coefficients. We emphasized the global stress response by summing the contribution of cascades of local frictional slip under specific boundary conditions. We illustrated that the decrease in stress difference manifests as a self-organized process that ultimately leads to frictional equilibrium. The model informs that the frictional equilibrium of a stochastic system can depart substantially from a deterministic estimation. Although the model quantitatively corroborates the notion of frictional equilibrium in places where fracture slip is the dominant mechanism for stress release, it reveals far more profound influence of system heterogeneity on the local and global stress evolution

Global Frictional Equilibrium via Stochastic, Local Coulomb Frictional Slips

Based on the assumption that fault slip dominates in the stress relaxation in the brittle crust, Coulomb theory allows for the crustal stress estimation with an empirical frictional coefficient. However, natural variability of fault friction and slip uncertainty exist in the Earth's crust. To address the extent to which heterogeneous frictional slips influence crustal stress and its evolution, we establish a quasi-static, 2D model to represent the fractured crustal rock mass. The model consists of randomly oriented fractures with heterogeneous distribution of frictional coefficients. The global mechanical response is quantitatively related to the cascades of local frictional slips under specific boundary conditions. The temporal evolution of stress is explicitly modeled by an iterative process where a simple slip law is assumed for critical fractures. We particularly illustrate the stress evolution in a normal faulting stress regime, considering different distributions of frictional coefficients. All cases indicate that the decrease in differential stress manifests as a self-organized process, eventually leading to the frictional equilibrium of the fractured rock mass. The final stress state upon equilibrium jointly depends on the orientation and frictional coefficient of all fractures therein. The model informs that the global stress state of a stochastic system can depart substantially from a deterministic estimation via an empirical frictional coefficient. This model quantitatively corroborates and extends the notion of frictional equilibrium, and reveals far more profound influence of system heterogeneity on the local and global stress evolution.ISSN:2169-9313ISSN:0148-0227ISSN:2169-935

Numerical investigation of the effect of distributed heat sources on heat-to-sound conversion in a T-shaped thermoacoustic system

10.1016/j.apenergy.2015.01.091Applied Energy144204-21

Competitive Hole Transfer from CdSe Quantum Dots to Thiol Ligands in CdSe-Cobaloxime Sensitized NiO Films Used as Photocathodes for H-2 Evolution

Quantum dot (QD) sensitized NiO photocathodes rely on efficient photoinduced hole injection into the NiO valence band. A system of a mesoporous NiO film co-sensitized with CdSe QDs and a molecular proton reduction catalyst was studied. While successful electron transfer from the excited QDs to the catalyst is observed, most of the photogenerated holes are instead quenched very rapidly (ps) by hole trapping at the surface thiols of the capping agent used as linker molecules. We confirmed our conclusion by first using a thiol free capping agent and second varying the thiol concentration on the QD's surface. The later resulted in faster hole trapping as the thiol concentration increased. We suggest that this hole trapping by the linker limits the H-2 yield for this photocathode in a device

Enhancing the hot carrier injection of perovskite solar cells by incorporating a molecular dipole interlayer

Surface passivation engineering of perovskite films via organic functional small molecules has emerged as an effective strategy for improving the efficiency and stability of perovskite solar cells (PSCs). However, a systematic understanding of underlying mechanisms behind these improvements is still missing. In this work, two new naphthalimide-based organic small molecules (PX, X = F, I) are designed and employed to efficiently passivate the surface defects of perovskite films in PSCs. Consequently, superior photovoltaic properties for PI-treated PSCs are achieved with a power conversion efficiency of 23.06%, which is significantly higher than that of the reference device without passivators (20.45%). Theoretical calculations reveal that PX can give rise to interfacial electrical dipole. It is found that incorporating a dipole interlayer between perovskite layer and hole transport layer can enhance ultrafast charge-carrier injection and suppress the charge-carrier recombination in device, which is illustrated by transient absorption spectroscopy. These present results can provide valuable information on the understanding interfacial charge-carrier dynamics in PSCs to further improve the device performance.Y.H. thanks National Natural Science Foundation of China (22065038), the Key Project of Natural Science Foundation of Yunnan (KC10110419), High-Level Talents Introduction in Yunnan Province (C619300A010), the Fund for Excellent Young Scholars of Yunnan (K264202006820), International Joint Research Center for Advanced Energy Materials of Yunnan Province (202003AE140001), the Program for Excellent Young Talents of Yunnan University and Major Science and Technology Project of Precious Metal Materials Genetic Engineering in Yunnan Province(No. 2019ZE001-1 and 202002AB080001-6)for financial support. T.W. acknowledges the support from the Yunnan University Research Innovation Found for Graduate Students(2021Z095)