No abstract

To study the influence of different resistance lines and rows delay intervals on the shape of the muck pile and the throwing distance of open-pit bench blasting based on the open-pit bench blasting test, two-dimensional particle flow code (PFC2D) is used for numerical simulation. The experimental and simulation data were compared and analyzed, and the error value was acceptable. Meanwhile, different resistance lines and row delay intervals are used to conduct numerical simulation analysis. The results show that the height change of the muck pile is directly proportional to the resistance line, and the rock throwing distance is inversely proportional to the resistance line change. The best resistance line is 1.75 m in the actual working condition, according to the effect of the muck pile. By fitting the relationship between the resistance line and rock throwing distance and blasting muck pile’s height, it is found that the relationship is nonlinear. By simulating different row delays, the optimal row delay time difference in the bench blasting model is determined to be 25 ms under similar working conditions. It provides a guiding significance for the blasting parameter design under similar working conditions.

Aim: To explore the efficacy of presetting catheter sheaths for uterine arterial embolization in the cesarean section of pernicious preplacental placenta. Materials and Methods: The clinical records of 37 patients with pernicious preplacental placenta were retrospectively analyzed. Sixteen patients who underwent cesarean section postoperative uterine artery embolization (UAE) were classified into group A, while 21 patients who received preset femoral catheterization followed with immediate UAE after the fetus was delivered by cesarean section were classified into group B. The therapeutic effects were compared. Results: The average amount of blood loss and infusion of patients in groups A and in B was 2,621 ± 626 ml and 6.23 ± 2.66 U and 1455 ± 486 ml and 3.03 ± 2.12 U, respectively (p < 0.01). One patient of group A received hysterectomy and no hysterectomy was seen in patients of group B. Conclusion: Intraoperative UAE using preset femoral artery catheterization prior to cesarean section has effectively reduced blood loss and infusion.