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As the computer vision develops, real-time fall detection based on computer vision has become increasingly popular in recent years. In this paper, a novel real-time indoor fall detection method based on computer vision by using geometric features and convolutional neural network (CNN) is proposed. Gaussian mixture model (GMM) is applied to detect the human target and find out the minimum external elliptical contour. Differently from the traditional fall detection method based on geometric features, we consider the importance of the head in fall detection and propose to use two different ellipses to represent the head and the torso, respectively. Three features including the long and short axis ratio, the orientation angle and the vertical velocity are extracted from the two different ellipses in each frame, respectively, and fused into a motion feature based on time series. In addition, a shallow CNN is applied to find out the correlation between the two elliptic contour features for detecting indoor falls and distinguishing some similar activities. Our novel method can effectively distinguish some similar activities in real time, which cannot be distinguished by some traditional methods based on geometric features, and has a better detection rate. [ABSTRACT FROM AUTHOR]

In this work, the electroless nickel plating on Nylon 12 (PA12) powders was developed. The effect of ultrasonic vibration on activation-electroless plating on PA12 powders were investigated systematically using scanning electron microscopy and X-ray diffraction. Results showed amine groups attached on the surface of KH550-modified PA12 powders. The surface structure of modified powders could adsorb the tin and palladium ions, which used as catalyst for the Ni plating. Ultrasonic vibration-assisted activating would facilitate the adsorption of Pd atoms on the surface of PA12 powders, however, hinder nickel atoms plated on the PA12 surface. When the PA12 powders were plated with and without ultrasonic vibration, the palladium content of activated powders were 0.15 and 0.04%, the nickel content of plated powders were 4 and 10%, amorphous shells and nickel particles plated on the surface of PA12 powders, respectively. [ABSTRACT FROM AUTHOR]

In this work, the effects of plating time on structural properties of Ni-plating coating on Nylon 12 (PA12) powders modified with 3-amino-propyltriethoxysilane (KH550) solution were investigated systematically using scanning electron microscopy and X-ray diffraction. Results showed amine groups attached on surface of KH550-modified PA12 powders, which could adsorb Sn and Pd used as sensitizer and activator, respectively. The relative concentration of Sn and Pd on sensitized and activated PA12 surface were 0.15 and 0.04%. When the plating time increased from 1 to 60 min, the crystallinity of Ni-plating coating enhanced and Ni-particle deposited content increased from 3.8 to 28%. Moreover, the Ni-plating particles firstly showed discrete distribution on the PA12 surface, average Ni-particle size was little changed at about 0.18 μm, and then showed continuous distribution with the average size increased to 0.32 μm. [ABSTRACT FROM AUTHOR]