A single-pulse spot welding test was performed on 0.13C-6.98Mn medium manganese TRIP steel. The test results showed that the joint performance increases with a rise in welding heat input before splashing occurs. Owing to the fusion zone (FZ) being closest to the heat source, its austenite content was completely transformed and its performance was worse than that of the heat affected zone comprising austenite. The segregation bands of C and Mn observed in the FZ were considered to be the main reason for the deterioration of grain boundary strength. These characteristics of the weld zone led to evident intergranular cracking and transgranular fracture in the tensile test, and all samples in this test showed partial or complete interfacial fractures.

The risk factors of bronchiectasis in patients with chronic obstructive pulmonary disease have not yet been established. This systematic review and meta-analysis aimed to investigate and identify potential risk factors for patients with chronic obstructive pulmonary disease accompanied by bronchiectasis. We reviewed eight electronic journal databases from their inception to November 2019 for observational studies with no language restrictions. The Newcastle-Ottawa Scale was applied to evaluate the quality of the literature. Binary variables were pooled using odds ratios and continuous variables using the standardized mean difference with 95% confidence intervals. The confidence of evidence was assessed according to the grading of the recommendations assessment, development, and evaluation method. Eight case-control studies met the inclusion criteria. Tuberculosis history, smoking history, hospitalization stays, admissions in the past year, and duration of symptoms were considered risk factors. In addition, the ratio between the forced expiratory volume in 1s and forced vital capacity, the percentage of forced expiratory volume in 1s, the forced expiratory volume in 1s as a percentage of the predicted value, purulent sputum, purulent mucus sputum, positive sputum culture, Pseudomonas aeruginosa infection, arterial oxygen pressure, daily dyspnea, C-reactive protein, leukocytes, and the percentage of neutrophils were found to be closely related to bronchiectasis. However, these were not considered risk factors. The evidence of all outcomes was judged as “low” or “very low.” Additional prospective studies are required to elucidate the underlying risk factors and identify effective preventive interventions.

Abstract This study conducted high-velocity penetration experiments using conventional ogive-nose, double-ogive-nose, and grooved-tapered projectiles of approximately 2.5 kg and initial velocities between 1000 and 1360 m/s to penetrate or perforate concrete targets with unconfined compressive strengths of nominally 40MPa. The penetration performance data of these three types of projectiles with two different types of materials (i.e., AerMet100 and DT300) were obtained. The crater depth model considering both the projectile mass and the initial velocity was proposed based on the test results and a theoretical analysis. The penetration ability and the trajectory stability of these three projectile types were compared and analyzed accordingly. The results showed that, under these experimental conditions, the effects of these two different kinds of projectile materials on the penetration depth and mass erosion rate of projectile were not obvious. The existing models could not reflect the crater depths for projectiles of greater weights or higher velocities, whereas the new model established in this study was reliable. The double-ogive-nose has a certain effect of drag reduction. Thus, the double-ogive-nose projectile has a higher penetration ability than the conventional ogive-nose projectile. Meanwhile, the grooved-tapered projectile has a better trajectory stability, because the convex parts of tapered shank generated the restoring moment to stabilize the trajectory.