Abstract Background: Anterior Cervical Corpectomy and Fusion(ACCF), which is one of the common surgeries used to treat cervical spine diseases, has been widely applied in clinical practice. The commonly used internal fixation forms in ACCF surgery include the traditional anterior vertebral body screw-plate (AVBSP) structure and the anterior cervical pedicle screw-plate (APSP) structure, both of which are combined with titanium mesh to achieve support and bone fusion. Objetives: The purpose was to investigate the effects of different surgical plans on cervical spine biomechanics and the interplay between internal fixation instruments after surgery. Methods: In this study, a finite element model of the human lower cervical spine (C3-C7) after ACCF surgery was established. The surgical plan consisted of two internal fixation forms (AVBSP and APSP) and two titanium mesh forms (linear and curved), combined in different ways. Results: The mechanical sensitivity of adjacent intervertebral disc nuclei to different surgical plans was significantly different. The stress concentration areas on the vertebral body entry surface varied with different entry methods, and the stress values were greatly affected by cervical movements. The related instrument studies showed that the choice of anterior fixation method would affect the stress level and distribution of the titanium mesh. Theoretically, the combination of curved titanium mesh and AVBSP is beneficial to reducing the overall stress level of the internal fixation instruments and titanium mesh. Conclusion:The research provides theoretical basis for the selection of clinical surgical plans. It is advantageous in enhancing postoperative stability of cervical vertebrae while reducing the risk of recurrence or other complications such as adjacent segment disease. Clinically, when selecting the excision fusion surgical plan based on the condition of the patient's cervical lesion, consideration should also be given to the matching characteristics between internal fixation methods and titanium mesh forms, as well as their effects on the biomechanics of adjacent segments.

Background: The locomotive traction motor has gradually shifted from DC motors to AC motors in high-speed railways, and the traction motor needs to be regularly maintained and tested frequently. Objective: The aim of this study was to test the related motor performance by obtaining and analyzing motor data from the test according to the standard "Three-phase Asynchronous Motor Test Method (GB-T 1032-2012)". The performance of the tested motor has been evaluated to meet the relevant requirements of the application. Thus, reasonable and scientific references have been offered for the maintenance and repair of the motor. Methods: A three-phase AC asynchronous motor test system based on LabVIEW and an AC power dynamometer was constructed based on the needs of the factory and type test of a three-phase AC asynchronous motor. Ambient temperature measurement, insulation resistance measurement, DC resistance measurement, no-load characteristics test, overspeed test, blocking characteristics test, load test, and temperature rise test have been carried out. The data on voltage, current, speed, power, and so on, have been collected. A 125 kW three-phase asynchronous motor was tested with the designed system, and the parameters obtained from the system were compared with those from the motor labels. Results: The three-phase AC asynchronous motor test system was designed based on LabVIEW and AC dynamometer operating on an industrial computer with a precision measuring instrument. The most advanced virtual instrument technology was used to combine the powerful data computing and processing ability with the measurement and control ability of instrument hardware. The software proved to be able to acquire data display, control, storage, and analysis simultaneously. In addition, a high degree of intelligence, an automatic motor start and stop control, automatic synchronous acquisition of test data, automatic data processing and calculation, and automatic test report generation and printing function were covered in this system. The simulated results of the system agreed well with the actual performance of the three-phase asynchronous motor, and helped the motor to operate well. Conclusion: The designed testing system exhibited a high automation ability, reliability, and accuracy. It proved to be a time and manpower-saving technical method, improving the actual test efficiency, and helped to reduce labor intensity dramatically.

Abstract The proportion of aerodynamic resistance in train operation resistance is increasing as the speed of the train continues to increase. A streamlined front can reduce train running resistance effectively. Windshields and pantographs cause sudden changes in the geometric shape of the train's longitudinal section also have a significant impact on train running resistance. High-speed trains generally use external windshields, which can reduce the impact of sudden changes on the running resistance to geometric shape of the train end connection. The article constructs a 3-group calculation model based on the true geometric shape of high-speed trains to study the aerodynamic drag reduction effect of the external windshield with three-dimensional, steady, incompressible N-S equations and k-ε are adopted to calculate the flow field distribution and pressure distribution of the external windshield of trains operating on open lines at a speed of 250km/h, 300km/h, 350km/h, 400km/h or 450km/h separately. The aerodynamic resistance and lift of the external windshield were fitted, although the train operating speed changed, it was a variation curve.

AbstractIn this work, a novel functional polylactic acid (PLA) was prepared by melt blending using epoxy Joncryl ADR 4468 (ADR) as chain extender. The effects of the epoxy chain expander ADR on the molecular structure, crystallization properties, rheological properties, and mechanical properties of PLA were studied. Furthermore, the chain expansion mechanism was analyzed. It was found that the epoxy group of the epoxy chain extender reacted with the terminal hydroxyl and terminal carboxyl groups of PLA in the molten state, thus significantly increasing the molecular weight of PLA. Meanwhile, the weight average molecular weight of PLA increased by 42.51% when the maximum additional amount of epoxy chain extender was 1.2 wt%. The dynamic rheological experiments also confirmed that ADR can effectively improve the storage modulus, loss modulus and complex viscosity of PLA systems and the Cole‐Cole diagram reveals the branched structure of PLA chain expansion systems. The formation of this branched structure will destroy the regularity of the PLA chain, reduce the crystallization capacity of PLA, and increase the cold crystallization temperature of the PLA system. Through SEM and mechanical property tests, it is found that the addition of ADR makes the molecular chain form a micro‐crosslinked structure, thereby improving the tensile strength of PLA. Therefore, the molecular structure of PLA was effectively regulated and exhibited a promising performance, which greatly expands the potential applications of PLA.