Explore the vast range of titles available.

A bstract We systematically investigate the electromagnetic form factors of heavy-light pseudo-scalar and vector mesons within the Dyson-Schwinger/Bethe-Salpeter equations framework for the first time. It is found that the charge radius of vector meson is larger than that of its pseudo-scalar counterpart. In heavy-light systems, the flavor symmetry breaking will lead to a splitting of the form factor of different quark, and the distribution range of lighter and heavier quark gradually expands and contracts, respectively. The competition between them together generates the electromagnetic form factors of meson. Our results can be compared with other theoretical calculations and future experimental data.

The flow direction is generally different from the gravity direction in geotechnical structures or slopes, the effect of which during suffusion remains unclear. This paper presents a coupled computational fluid dynamics and discrete element method approach to simulate the particle–fluid interaction relevant to this problem. The CFD-DEM approach is first benchmarked by a classic granular system problem, which is then used to investigate the characteristics of suffusion and its impact on the mechanical behavior. Five different angles between gravity and seepage directions for gap-graded soils with two fines contents are examined. Both the macroscopic and microscopic characteristics during suffusion and triaxial loading tests are analyzed. The direction angle is found to play a significant role affecting the erosion process and the mechanical consequence of soils. The results show that the greater the angle is, the harder it is for suffusion to occur and continue.

The microstructure of microbially induced carbonate precipitation (MICP) stabilized soils is typically used to explain the macro‐scale properties of the soils. However, the microstructure is usually inferred from scanning electron microscopy results after breakage, as directly observing the processes inside the pores is challenging. Microfluidics technique provides the solution for visually observing the in situ precipitation process at pore scales. This work endeavors to visually observe and quantitatively analyze the pore scale precipitation process of MICP in characteristic pore structures with the help of the microfluidics technique. Pore structure is one of the most important factors affecting the flow field in pore networks, which might further affect the transport of reactive components and the distribution of precipitates in pores. Therefore, two groups of simplified pore networks were designed to investigate the influence of pore structure. The current work gives an implication of how pore structure and flow rate influence the MICP process and precipitation efficiency at the pore scale. The results also highlight the importance of the diffusion of reactants, and the dissolution and scouring of crystals on the distribution of precipitates at pore scale. Key Points Simplified pore structures (series and parallel structures) are designed to study the pore‐scale CaCO3 precipitation induced by microbes An image processing method is proposed to obtain high‐resolution raw and binarized images of whole chip to analyze precipitation kinetics Flow fields, derived from bacterial migration and simulation, are used to analyze their impact on pore‐scale MICP process

Quantum key distribution (QKD) provides a promising solution for sharing information-theoretic secure keys between remote peers with physics-based protocols. According to the law of quantum physics, the photons carrying signals cannot be amplified or relayed via classical optical techniques to maintain quantum security. As a result, the transmission loss of the channel limits its achievable distance, and this has been a huge barrier towards building large-scale quantum-secure networks. Here we present an experimental QKD system that could tolerate a channel loss beyond 140 dB and obtain a secure distance of 833.8 km, setting a new record for fibre-based QKD. Furthermore, the optimized four-phase twin-field protocol and high-quality set-up make its secure key rate more than two orders of magnitude greater than previous records over similar distances. Our results mark a breakthrough towards building reliable and efficient terrestrial quantum-secure networks over a scale of 1,000 km.Twin-field (TF) quantum key distribution (QKD) over a secure distance of 833.8 km is demonstrated even in the finite-size regime. To this end, an optimized four-phase TF-QKD protocol and a high-speed low-noise TF-QKD system are developed.

This study presents an integrated approach to evaluate inundation risks, in which an algorithm is proposed to integrate the storm water management model (SWMM) into a geographical information system (GIS). The proposed algorithm simulates the flood inundation of overland flows and in metro stations for each designed scenario. It involves the following stages: (i) determination of the grid location and spreading coefficient and (ii) an iterative calculation of the spreading process. In addition, an equation is proposed to calculate the inundation around a metro station and to predict the potential inundation risks of the metro system. The proposed method is applied to simulate the inundation risk of the metro system in the urban centre of Shanghai under 50-year, 100-year, and 500-year rainfall intensities. Both inundation extent and depth are obtained and the proposed method is validated with records of historical floods. The results demonstrate that in the case of a 500-year rainfall intensity, the inundated area with a water depth excess of 300 mm covers up to 5.16 km2. In addition, four metro stations are inundated to a depth of over 300 mm.

Despite the extensive research on crack propagation in brittle solids, numerous unexplored problems still necessitate in-depth study. In this work, we focus on numerical modeling of multi-crack growth, aiming to explore the effect of material heterogeneity and multi-crack interaction on this process. To do this, an improved singular-finite element method (singular-FEM) is proposed with incorporation of heterogeneity and crack interaction. An efficient algorithm is proposed for simulating multi-crack propagation and interaction. Stress singularity near crack tip is reproduced by the singular elements. The singular-FEM is convenient and cost-effective, as the zone far away from crack tips is directly discretized using linear elements, in contrast to the quadratic or transition elements utilized in traditional FEM. Next, the proposed method is validated through benchmark study. Numerical results demonstrate that the superiority of the singular-FEM, which combines the merits of low cost and high accuracy. Then, the mechanics of crack growth are explored in more complex scenarios, accounting for the effects of crack interaction, loading condition and heterogeneity on crack trajectory, stress field and energy release rate. The findings reveal that the combined effect of heterogeneity and crack interaction plays a critical role in the phenomenon of crack growth, and the proposed method is capable of effectively modeling the process.

Corner breakage was less analyzed in pile–soil interaction research, causing the mechanism of particular pile load behaviors in coral sand to remain unclear. This study investigates the particle corner breakage effect on pile load performance in coral sand at both the macro-scale and particle-scale via indoor pile load model testing and Discrete Element Method and Finite Difference Method (DEM–FDM) coupled simulations. In numerical simulations, corner grains were constructed by the cluster method. Results revealed that compared with the fracture breakage, the corner breakage has a more obvious soil loosening effect. The coupled effect of corner interlock and corner breakage well explained the side friction distributions and the load share of pile tips in breakable corner grains. Besides, after obvious corner breakage, a much narrower pile-affected width around pile sides and a deeper stress transmission under pile tips were discovered in corner grains. Moreover, the decrease in effective contacts and change in soil skeletons have been proven to be essential factors behind the narrower pile-affected width and deeper stress transmission in breakable corner grains. Finally, compared with breakage effects in the previous research, the particle corner breakage effect was proved to have advantages in explaining large and sudden settlements of piles in coral sand with the use of a positive feedback loop. This study highlights the advantages of using particle corner breakage effects to explain specific pile load behaviors in coral sand and provides insight into the mechanism of pile–soil interaction in breakable granular soils.

Particle size strongly influences the shear strength of granular materials. However, previous studies of the particle size effect have focused mainly on the macroscopic behavior of granular materials, neglecting the associated micro-mechanism. In this study, the effect of particle size on the shear strength of uncrushable granular materials in biaxial testing is investigated using the discrete element method (DEM). First, a comprehensive calibration against experimental results is conducted to obtain the DEM parameters for two types of quartz sand. Then, a series of biaxial tests are simulated on sands with parallel particle size distributions to investigate the effect of particle size on macro- and microscopic behaviors. Finally, by adopting the rolling resistance method and the clump method, irregular-shaped particles are simulated to investigate how the particle size effect will be influenced by the particle shape. Simulation results demonstrate that (1) the peak shear strength increases with particle size, whereas the residual shear strength is independent of particle size; (2) the thickness of the shear band increases with the particle size, but its ratio decreases with particle size; (3) the particle size effect can be explained by the increase of friction utilization ratio with particle size; and (4) the particle size effect is more significant in granular materials that consist of particles with higher angularity.

A series of uniaxial and triaxial compression tests were performed on slate samples with different diameters at different foliation orientations with respect to the direction of the major principal stress. The size effect and anisotropy in slate, as a transversely isotropic rock, were investigated, and the research focused on aspects of elastic properties, uniaxial compressive strength (UCS), triaxial compressive strength (TCS), and triaxial residual strength (TRS). In the five elastic constants for slate, only the Young’s modulus parallel to the isotropic plane is size dependent. The UCS follows a descending size-effect model developed from coal. The size-effect behaviors of the UCS and TCS are similar. Two size-dependent failure criteria are proposed by incorporating the size-effect model for UCS into the modified Hoek–Brown and Saeidi failure criteria and are verified against experimental data. This is the first time that the relationship among the compressive strength, specimen size, foliation orientation and confining pressure has been comprehensively captured for transversely isotropic rock. Without an evident size effect, the anisotropic TRS has also been effectively captured by a modified cohesion loss model, and two bound equations for the brittleness index are finally proposed for transversely isotropic rock. This work promises to provide an upscaling method for determining the mechanical parameters of transversely isotropic rocks in practical engineering.

A transversely isotropic rock, slate, was utilized to investigate the size effect and anisotropy on its deformation, tensile strength, and failure mechanism. A series of Brazilian tests were conducted on slate samples of six different sizes from 25 to 100 mm in diameter at seven different loading-foliation angles from 0° to 90°. The results indicate that the Young’s modulus in the plane of transverse isotropy increases, while the Young’s modulus and shear modulus perpendicular to the plane of transverse isotropy decrease with specimen size. The tensile strength of the slate increases with increasing loading-foliation angle, the variation of which is well captured by the Nova–Zaninetti criterion. Furthermore, the tensile strength of the slate increases with specimen size at loading-foliation angles from 0° to 45°, while it increases first and then decreases with specimen size at loading-foliation angles from 60° to 90°. A unified size-effect relation including two equations is proposed and verified against the experimental data on slate. The size-effect relation reveals the relationship among the tensile strength, specimen size, and loading-foliation angle for the transversely isotropic rock. Finally, the slate samples exhibit an increased brittle failure with specimen size, which is consistent with the observations in various isotropic rocks. It is also found that the specimen size, loading-foliation angle, and loading configuration together control the failure mechanism of transversely isotropic rocks in the Brazilian test.