Macro and micro grouting process and the influence mechanism of cracks in soft coal seam

Grouting is an important method to reinforce soft coal roadway,and the presence of primary cracks in the coal body has an important influence on the grouting effect.With the discrete element simulation method,the grouting process of the soft coal seam was simulated.The mechanism of primary cracks on grouting was revealed,while the influence of fracture characteristics and grouting pressure on the grouting effect was analyzed.The results demonstrated that grouting in the soft coal seam involves the stages of seepage,rapid splitting,slow splitting,and stability.Due to the presence of primary cracks,the grouting diffusion radius increased significantly.Under the slurry pressure,the tensile stress concentration was formed at the crack tip,and the slurry split the coal once the splitting pressure was reached.In addition,the distribution characteristics of fractures are found to have a great influence on the grouting effect.It is observed that smaller fracture spacing is associated with a larger slurry diffusion radius and thus easier penetration of the primary crack tips.The fracture angle affects the direction of fracture propagation.The secondary fracture formed by splitting is a tensile fracture,which is more likely to extend along the direction parallel to the maximum principal stress.Overall,these simulation results have guiding significance for the setting of reasonable spacing of grouting holes in the practice of grouting engineering.

Low-noise InGaAs/InP single-photon detector with widely tunable repetition rates

InGaAs/InP avalanche photodiodes typically work in the gated Geiger mode to achieve near-infrared singlephoton detection. By using ultrashort gates and combining with the robust spike-canceling technique that consists of the capacitance-balancing and low-pass filtering technique, we demonstrate an InGaAs/InP single-photon detector(SPD) with widely tunable repetition rates in this paper. The operation frequency could be tuned conveniently from 100 MHz to 1.25 GHz with the SPD's performance measured to maintain good performance, making it quite suitable for quantum key distribution, laser ranging, and optical time domain reflectometry. Furthermore,the SPD exhibited extremely low-noise characteristics. The detection efficiency of this SPD could reach 20% with the dark count rate of 2.5 × 10^(-6)∕gate and after-pulse probability of 4.1% at 1 GHz.

Imaging Fast Cellular Uptake of Polymer Dots via Receptor‑Mediated Endocytosis

During the past decade,semiconducting polymer dots(Pdots)have been prevailing in the family of fluorescent probes due to its high photon budget,excellent photo stability,and good biocompatibility.In this study,holo-Transferrin human(Tf)was utilized to covalently couple with Pdots for a highly efficient endocytosis process through transferrin receptors(TfRs)mediated internalization.As a result,the endocytosis efficiency of Tf-conjugated Pdots in HeLa cells dramatically increased as compared to that of unconjugated Pdots in the same condition.This acute increment demonstrates that holo-Transferrin molecules are of great capability for intracellular delivery of Pdots to TfRs overexpressed cells.The transportation route of Tf-conjugated Pdots is quite different from the uptake mechanism of unconjugated Pdots via nonspecific endocytic trafficking pathway.Considering the overexpression of TfRs in various cancer cells,Tf-conjugated Pdots hold potential to function as a nanocarrier for efficient drug delivery in cancer diagnostics and therapy.