ABSTRACT
Objective To establish a 3D finite element model of an anti-shearing force Ni-Ti memory shape alloy patella claw for fixing patellar fracture, and analyze its mechanical performance. Methods The internal fixation model of transverse patellar fracture by patella claw was established by Pro/E 5.0, and then imported it into ABAQUS 10.1 for finite element analysis on its mechanical properties. The mechanical performance and deformation of the patella claw under two different patella femoral joint forces FQ at the knee flexion angle of 30°, 60°, 90° were analyzed, respectively. Results Under the same boundary condition, with the respective FQ as 367.5 N and 3 675 N, the maximum displacements of deformation were different at different flexion angles. As compared to fixation by tension band, using patella claw was preferable, with stronger resistance to tension and more stable anti-shearing force. Conclusions Deformation and displacement of the patella claw are in accordance with the biomechanical results needed in clinic, and its stability can satisfy clinical requirements for functional exercise as early as possible.
ABSTRACT
The natural ventilation widely used in greenhouses has advantages of saving energy and reducing expense. In order to provide information for climate control of greenhouse, a model was developed to predict the variation of air temperature in the naturally ventilated greenhouse equipped with insect-proof screen. Roof ventilation and combined roof and sidewall ventilation were considered in the model. This model was validated against the results of experiments conducted in the greenhouse when the wind was parallel to the gutters. The model parameters were determined by the least squares method. In the used model, effects of wind speed and window opening height on the air temperature variation were analyzed. Comparison between two types of ventilation showed that there existed a necessary ventilation rate which results in air temperature decrease in natural ventilation under special climatic conditions. In our experiments when wind speed was less than 3.2 ms(-1), wind had a more gradual effect on greenhouse temperature for roof ventilation, compared with combined roof and sidewall ventilation, which had greater air temperature decrease than roof ventilation only.
Subject(s)
Air Conditioning , Methods , Air Movements , Computer Simulation , Computer-Aided Design , Equipment Design , Equipment Failure Analysis , Methods , Insect Control , Methods , Models, Theoretical , Plant Development , Plastics , Rheology , Methods , Temperature , WindABSTRACT
The behavioral responses of a tilapia (Oreochromis niloticus) school to low (0.13 mg/L), moderate (0.79 mg/L) and high (2.65 mg/L) levels of unionized ammonia (UIA) concentration were monitored using a computer vision system. The swimming activity and geometrical parameters such as location of the gravity center and distribution of the fish school were calculated continuously. These behavioral parameters of tilapia school responded sensitively to moderate and high UIA concentration. Under high UIA concentration the fish activity showed a significant increase (P<0.05), exhibiting an avoidance reaction to high ammonia condition, and then decreased gradually. Under moderate and high UIA concentration the school's vertical location had significantly large fluctuation (P<0.05) with the school moving up to the water surface then down to the bottom of the aquarium alternately and tending to crowd together. After several hours' exposure to high UIA level, the school finally stayed at the aquarium bottom. These observations indicate that alterations in fish behavior under acute stress can provide important information useful in predicting the stress.