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We perform the first-principles calculations within the framework of density functional theory to determine the electronic structure and optical properties of P-doped and B-doped silicon nanotubes. The results indicate that the electronic structure and optical properties of P-doped and B-doped silicon nanotubes are sensitive to the impurity composition. In particular, when doped with P or B, obviously the band gap decreases and the conductivity enhanced, the P-doped and B-doped silicon nanotubes displays a closer band structure and the unit cell volume of doped silicon nanotubes increased than before doping, the change depends on the doping charge and Si-Si bond length dSi-Si. Moreover, the dielectric constant decreases and increased when doped P and B, the optical absorption peak obviously has a blue shift and red shift respectively. The calculated results provide important theoretical guidance for the applications of Uv detector and the solar cell in optical detectors.

This paper presents a novel parallel tri-axis force sensor with decoupled feature, and performs its performance analysis. Firstly, the structural characteristics of the parallel tri-axis force sensor are introduced and the stress distribution of each limb elastomer is analyzed. To measure the transformation relationship between the force and strain, the electric bridge is formed by pasting strain on the elastic-sensitive element. Then, the finite element simulation of the elastomer is conducted and performance analysis of the sensor is carried out, which shows that the parallel tri-axis force sensor is decoupled, linear and fully-isotropy. The sensor possesses good static performance and can meet the requirements of tri-axis force measurement in general industrial production. The contents of this paper riches the structure type of the multi-component force sensor and will be useful for the research and development of the parallel force sensor.

As an important mechanism with special and extensive application, the three degrees of freedom spherical parallel mechanism is always a research hot in the mechanical fields. In this paper, the feature of the 3-RRR spherical parallel mechanism with coaxial input shafts is introduced, and its motion feature is analyzed based on the screw theory. The mobility of the spherical parallel mechanism is calculated by using the Modified Kutzbach-Grübler criterion, and the inverse displacement problem of the mechanism is solved. Then the expression of the Jacobian matrix is deduced based on the kinematics equation and its inverse solution. The contents of this paper should be useful for the further application of the spherical parallel mechanism.

In the field of spatial orientation, the rotational parallel mechanism is widely used. While the existence of coupling brings about the parallel mechanism some difficulties in kinematics and dynamic analysis, the development of control system, and so on. This condition restricts the application fields and effects of the rotational parallel mechanism. Therefore, this paper proposes a novel 2-DOF (two degrees of freedom) rotational DPM (decoupled parallel mechanism). The feature of the mechanism is described and their movement form is analyzed with screw theory. The proposition of the novel rotational DPM will enrich the configurations of the parallel mechanism, and the contents of this paper should be useful for the further research and application of the rotational parallel mechanism.

A method of abnormal motion detection for intelligent video surveillance is presented, which includes object intrusion detection, object overlong stay detection and object overpopulation detection. Background subtraction algorithm is used to detect moving objects in video streams. Kalman filter is applied for object tracking. By the construction of relation matrix, the tracking process is divided into five statuses for prediction and estimation, which are object disappearing, object separating, new object appearing, object sheltering and object matching. The object parameters and predictive information in the next frame which is used to track moving objects is established by Kalman filter. Then, three types of abnormal motion detection are implemented. The relative position of alarm area or guard line with the rectangle boxes of the moving objects is used to detect whether the object is invading. The existing time of the moving objects in monitor area is counted to detect whether the object is staying too long. Moving objects in the monitor area are classified and counted to detect whether the objects are too much. Alarm will be triggered when abnormal motion detection as defined is detected in the monitor area.