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The development of fatigue damage in reinforced concrete (RC) beams is affected by various factors such as repetitive loads and material properties, and there exists a complex nonlinear mapping relationship between their fatigue performance and each factor. To this end, a fatigue performance prediction model for RC beams was proposed based on the deep belief network (DBN) optimized by particle swarm optimization (PSO). The original database of fatigue loading tests was established by conducting fatigue loading tests on RC beams. The mid-span deflection, reinforcement strain, and concrete strain during fatigue loading of RC beams were predicted and evaluated. The fatigue performance prediction results of the RC beam based on the PSO-DBN model were compared with those of the single DBN model and the BP model. The models were evaluated using the R2 coefficient, mean absolute percentage error, mean absolute error, and root mean square error. The results showed that the fatigue performance prediction model of RC beams based on PSO-DBN is more accurate and efficient.

OBJECTIVE: To introduce a new type of simple adjustable bilateral bi-directional traction device of PVC (Polyvinylchloride) tube, and discusses the application value of this device before operation in patients with lower limb fractures. METHODS: To introduce the manufacturing process of adjustable bilateral traction device of PVC pipes. From August 2018 to November 2019, the data of 36 patients with lower limb fractures treated with this traction device were analyzed retrospectively. The results of treatment were analyzed, including limb length of both lower limbs, fracture reduction, lower limb mobility, visual analogue scale (VAS), incidence of complications, and patient satisfaction. RESULTS: All patients can perform MRI examination immediately after using the device, which is conducive to rapid and comprehensive diagnosis of diseases. The patient's pain is significantly reduced and were free to turn over during bed rest, with the length of the affected limb restored to equal to that of the healthy limb. 34 patients were satisfied with the reduction of fractured end, 2 patients with tibiofibular fracture showed angular displacement of fractured end, and the reduction was satisfactory after adjusting the position of bone traction needle; 7 patients had deep venous thrombosis of affected lower limb during traction; no pressure sore, vascular nerve injury, with an overall complication rate of 25% (9/36). All patients and their families were satisfied with this treatment the results. CONCLUSION: The device can be temporarily assembled by the physician according to the specific conditions of different heights, fracture sites and uses of patients according to the needs of clinical treatment, and also has the advantages of economy, practicality, simple use and light weight. The device proved to be an effective and acceptably safe device for patients with lower limb fractures before operation temporary treatment. Especially suitable for patients with severe combined injury who need MRI examination urgently.

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