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In view of the shortcomings of high detection error rate of the existing fall detection algorithm,an improved fall detection algorithm is proposed.First,the Gaussian mixture model is used to detect the foreground object,and then median filtering and morphological processing are used to extract the foreground object.Based on the use of human aspect ratio and effective area ratio,the change of centroid,orientation angle and motion coefficient are taken as features to judge whether the human has fallen.Compared with traditional algorithnal,experimental results show that the proposed algorithm has higher accuracy,higher sensitivity,low algorithm complexity,and can effectively prevent misjudgment.

In view of the increased seriousness of the accident caused by another collision on the scene of traffic accident,a traffic accident scene alarm system based on nRF24L01 is proposed.When a vehicle traffic accident occurs,the nRF24L01 module will keep sending wireless signals to the passing vehicles.After the passing vehicles receive the signals,audio codecs controlled by the STM32F429 master play the voice,and remind the drivers to slow down.Compared with the traditional nRF24L01 module,the transmission distance of the wireless signal amplified by RFX2401C can be farther.Compared with the signal of by light or broadcast,the wireless signal has strong penetration and strong anti-interference ability.Experiments show that the system can achieve long distance reminder to prevent another collision.

GPS is used in ships,vehicles,aircraft and other moving objects.GPS also has the important application in vehicle monitoring system.However,with the expansion of the specialized functions of GPS,its high cost makes so many ordinary consumers unbearable.This paper proposes a simple design of GPS based on singlechip.The design Improves the basic utility functions of system and adds the speed and mileage measurement.GPS module uses the differential technology to improve the positioning accuracy.Therefore,the navigation device is compact,easy to carry and of high precision positioning.Through getting the data of 3D coordinates from the observation point and the factor of position accuracy,the average of which is less than five,indicating that the position accuracy can be improved by differential technology to achieve the desired range.At last,the feasibility of this design is verified through the current data tested in the outdoors.

According to the researches of transmitting downlink signal based on optical carrier suppression, we demonstrate two different ROF systems, one is based on intensity modulation to suppress the optical carrier, another is using phase modulation to generate sidebands to transmit the downlink signal. Simulation results prove the validity and reliability of the systems. A comparative study is carried out to the advantages and disadvantages of the transmission performance of both systems according to the spectra, the parameter of Q value, eye diagrams and BER curve, meanwhile the effectiveness and reliability of system are verified.