High-precision single-axis rotation measurement method of multi-rudders based on monocular vision.

To evaluate the assembly accuracy of rudders during the production of aerospace vehicles, a measurement method based on monocular vision is proposed in this paper. Compared with existing methods that adopt cooperative targets pasted manually, the proposed method avoids pasting cooperative targets on the surface of rudders and calibrating the original position of rudders in advance. First, we use two known position markers on the surface of the vehicle and multiple feature points of the rudder to solve the relative pose between the camera and the rudder by employing the PnP algorithm. Then, we measure the rotation angle by converting the change of the camera's pose to the rotation angle of the rudder. Finally, a tailored error compensation model is introduced into the proposed method to increase the accuracy of the measurement. Experiment results show that the average measurement absolute error of the proposed method is less than 0.08° overall, which is remarkably superior to existing methods and satisfies the requirement of practical industrial production.

[Influence of different degrees of chronic intermittent hypoxia on c-fos protein and apoptosis in rats].

OBJECTIVE: To establish different degrees and duration of animal hypoxia model of sleep apnea hypopnea syndrome according to the mechanism of intermittent hypoxia, to observe the effect of c-fos protein and apoptosis, and to explore the mechanism of nervous system injury. METHODS: By using the model of chronic intermittent hypoxia in rats, male Wistar rats (n = 72) were randomly divided into three groups: 5% of chronic intermittent hypoxia group (the fraction of oxygen volume reduced to 5% under hypoxia), 10% of chronic intermittent hypoxia group (the fraction of oxygen volume reduced to 5% under hypoxia) and control group. The levels of on c-fos protein and apoptosis of hippocampal cell in three groups were detected at the 2nd, 4th, 6th and 8th week respectively. The expression of c-fos protein in hippocampal cell was detected by immunohistochemical method and the apoptosis of hippocampal cell was detected by TUNEL. RESULTS: The relative quantity of c-fos protein and apoptotic index in CIH groups were significantly higher than that of the control group on the 2nd, 4th, 6th and 8th weeks (F were 44.52, 57.56, 24.20 and 13.18, P < 0.05), and these were higher obviously in 5% CIH group than that in 10% CIH group (P < 0.05). The expression of c-fos protein and apoptotic index in two CIH groups was different depending upon the different degree and duration of chronic intermittent hypoxia. With increased exposure time, the expression of c-fos protein and apoptotic index was high generally at first, peaked at 6th week, then down at 8th week (P < 0.05). While it in UC group was invariability in different time (P > 0.05). The correlation between the relative quantity of c-fos protein and apoptotic index in two CIH groups was positive (r were 0.816 and 0.701, P < 0.01). CONCLUSION: Moderate and severe intermittent hypoxia induced the excessive expression of c-fos protein in hippocampus, caused nerve cell apoptosis, and may play an important role in the mechanism of early brain injury of intermittent hypoxia.

[The relation of learning deficits with oxidative stress in rats exposed to severe intermittent hypoxia].

OBJECTIVE: To observe the relations between learning memory function and oxidative stress in rats exposed to severe intermittent hypoxia (IH). METHODS: Adult male Wistar rats (n = 48) were randomly assigned to 2 groups: untreated control group (UC) and 5% intermittent hypoxia group (5%IH). At 2, 4, 6 and 8 weeks, the learning and memory ability of the rats in each group were assessed with the Morris water maze (MWM) test. The ultrastructural changes in the hippocampus of the rats were observed with transmission electron microscopy (TEM). The levels of malondialdehyde (MDA) and superoxide dismutase (SOD) were detected by colorimetric method. RESULTS: The water maze test showed that the rats in the 5% IH group had prolonged latency in escaping, reduced target quadrant time in crossing and reduced frequency of crossing the platform, as compared to the UC group (P < 0.05). With longer time of hypoxia, the damage became more significant. It was observed that the structure of neuron cell was complete and organelles were abundant in UC groups. With the extension of exposure time, the number of hippocampus neurons and synaptic were decreased in 5%IH groups, nucleus shrank, synaptic frame became indefinite and synaptic cleft widen. Comparing with control group, the level of MDA in the hippocampal region group was significantly higher (P < 0.05) and the activity of SOD significantly was lower (P < 0.05) in 5%IH, along with the time expand, which aggravated. CONCLUSION: Severe intermittent hypoxia that results in learning and memory dysfunction. It is possible that oxidative stress change the quantity and structure of hippocampal neurons and synaptic, which aggravates along with the intermittent low oxygen time expand.