The effect of weak magnetic field (WMF) on Acid Orange 7 (AO7) removal by ZnO@Fe3O4/peroxymonosulphate (PMS) was investigated. The results showed that the AO7 sequestration rate enhanced progressively to 0.14183 min-1 in the presence of WMF, approximately 3 times the 0.04966 min-1 in the absence of WMF. SO4˙-/SO5˙- and O2˙- radicals were generated from the decomposition of PMS catalyzed by ZnO@Fe3O4 causing the degradation of AO7. In addition, a weak magnetic field promoted the production of O2˙- radicals and transition of Fe3+ to Fe2+. Radical-pair theory was used in this study to describe the role of WMF and a possible reaction mechanism was derived. Based on that, the influence of magnetic field flux intensity, pH and the reusability of ZnO@Fe3O4 were investigated in this paper.
Abstract High junction temperature (T j ) of LED will affect the performance and life of LED, so this paper proposes a high-power LED junction temperature test method. Mainly aiming at the problem that the accuracy of the forward current method (FCM) will be affected by the calibration procedure, equipment aging, and technical differences when batch testing LED T j , this paper uses the relationship between relative current and T j to calibrate the procedure based on this method, to limit the negative affection of sample heterogeneity. Ten LED samples were tested in the experiment, and the T j errors under two test methods were obtained. The results showed that the improved method was more accurate than the traditional method. Then, the T j error of the improved method was compared with that of the forward voltage method, and the error of the new method was smaller.
Fall detection plays an important role in the healthcare of older adults. Falls are reported to be the leading cause of death in people over the age of 65. For fall detection, computer vision-based methods are currently the best performing methods. This paper proposes a fall detection system with a Orangepi 5B development board as the core processor and a shape and motion change method. First, we use the VIBE detection algorithm to extract human silhouettes from the video, and improve the effect through certain post-processing. Then, the information obtained by ellipse fitting and the vertical and horizontal projections in the projection map are used as features to distinguish different postures of the human body. The abnormal downward movement speed measured by the optical flow method was used to preliminarily judge the fall, and then the occurrence of the fall was determined by the auxiliary judgment of the posture feature. Experiments show that our fall detection system achieves good performance in terms of both accuracy and error.
This article analyzes the phenomenon of LED junction temperature changing with the circuit and environment, and proposes an improved measurement of LED junction temperature based on infrared thermal imaging method. By fitting the curve between heat transfer parameters and LED chip and packaging parameters, an LED experimental model is constructed, and junction temperature detection experiments and theoretical simulations are carried out. The results indicate that compared to traditional infrared thermal imaging methods, this method is more convenient and intuitive, and can quickly measure LED junction temperature. Finally, this article compares the LED junction temperature detection results under different experimental conditions to verify the universality of this method.
In order to easily and accurately measure the junction temperature of high-power LED, this paper designs a new k-value calibration module based on LabVIEW platform, and develops an improved LED junction temperature measurement system by combining hardware equipment such as thermostat, data acquisition card, constant current source and temperature sensor, aiming at the huge workload brought by fitting the voltage temperature coefficient K under large current with small current data and the measurement error caused by self heating effect. The measurement system can measure the LED junction temperature in real time and store the required data. Compared with the measured junction temperature by forward voltage method, the maximum relative error is 1.4%, which indicates that the system has high measurement accuracy.
In this study, an algorithm based on improved maximum stable extremum region (MSER) was used to match and recognize the content of signage in the airfield, so as to overcome unrecognizable signage caused by low visibility or an overlapping field of view of multiple aircrafts. Firstly, the MSER algorithm was employed to combine regional structure similarity with feature space to realize the matching and recognition of signage in airport flight areas and improve the stability of signage content recognition. Secondly, the threshold of repeated recognition content was eliminated using the NMS algorithm to handle the repeated recognition caused by the MSER algorithm. Finally, an identification card of the taxiing paths in an airport flight area was selected for simulation. The experimental results demonstrated that the accuracy of identification card content can be improved by the optimized MSER algorithm.
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