Aircraft pipelines are mainly used for the storage and transportation of fuel, hydraulic oil and water, which are mostly bent pipes of non-ferromagnetic materials. We used PPM (Periodic Permanent Magnet) EMAT (Electromagnetic Acoustic Transducer) to detect the defects at 90-degree bends. A simulation model was established by finite element software to study the propagation characteristics and defect detection capability of T (0, 1) mode-guided wave in aluminum pipe bend. In terms of propagation characteristics, the energy of the guided wave was focused in the extrados of the bend, and the guided waves in the intrados and extrados of the bend were separated due to the difference in propagation distance. Regarding defect detection capability, T (0, 1) mode-guided wave had the highest detection sensitivity for the defect in the extrados of the bend and the lowest detection sensitivity for the defect in the middle area of the bend. We designed a PPM EMAT for 320 kHz to verify the simulation results experimentally, and the experimental results are in good agreement with the simulation results.
Background To evaluate dynamic changes in anterior segment biometric parameters after lens extraction (LE) in different subtypes of primary angle-closure glaucoma (PACG). Methods We conducted a prospective cohort study in 35 eyes of 27 patients with PACG who were enrolled between October 2019 and January 2021. Patients underwent ultrasound biomicroscopy before and after LE surgery. All enrolled eyes were classified into two subgroups according to their angle morphology: pure pupillary block group (PPB) and non-pure pupillary block group (NPPB). Follow-up examinations were performed postoperatively (at 1, 3, and 6 months) to observe dynamic changes in the anterior chamber angle. Results PPB was identified in 11 eyes (31%) and NPPB was identified in 24 eyes (69%). The change in anterior chamber depth was similar in both groups, while improvements in the angle opening distance at 500 µm and the trabecular-iris angle were larger in the PPB group than those in NPPB group at 1-month, 3-month, and 6-month follow-up. The trabecular ciliary process distance and the trabecular ciliary angle increased statistically significantly after surgery in both groups. Ciliary body thickness at the scleral spur and iris thickness showed no statistically significant changes postoperatively in either group. Conclusions LE has a weaker long-term effect in widening the anterior chamber angle in eyes with non-pure pupillary block mechanism than in eyes with pure pupillary block mechanism. LE cannot eliminate the configuration of the anterior ciliary position. Clinicians should perform individualized treatments for PACG according to the relevant angle-closure mechanisms.
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