A novel action recognition framework based on integrated model is proposed in the paper. First, the covariance descriptor is utilized to extract features from video sequences, and then each class specific codebook is constructed and appended to the global codebook. A static model applying the template matching technique and a dynamic model employing the trigram model are learned to capture complementary information in an action. And lastly, an integrated model is used to estimate the confidence of the static and dynamic models and produces a reliable result. Comparative experiments show that our presented method achieves superior results over other state-of-the-art approaches. Keywords: human action recognition, covariance descriptor, integrated model
In the study of miniature optically pumped NH3 FIR laser, We found that, when the NH3 gas was pumped by CO29R(16) IR laser, the 90 gm FIR laser line would be obtained with high efficiency. Especielly, in case the length of sample tube is very short for mini-OPFIRL, and the operating gas pressure will be several tens Torrs. So that the pressure broadening was important. In the CO29R(16) pumped NH3 s-aP(7,0) and s-an41) FIR lasers, the lasing frequency of these two transitions are close to each other as shown in Fig. 1 and Fig. 2. So the pressure broadening course part of these laser lines overlap to each other. The 6Ki0 transitions in the molecular system as shown in Fig. 3 are for- bidden, so overlaping of spectral line can only increace the background intensity of the FIR signal, and the FIR laser will be enhanced as shown in Fig. 3. The efficiency of the system will be much increased. We call it the two photon processes interaction enhancement effect.
Theoretical calculation on the output power density of optically pumped far-infrared laser was usually based on three-level system model for simplicity. Considering on the far-infrared self-absorption effect of the operating gas medium, the ready-made calculation should be renewed. The calculating method of self-absorption was proposed.
The tunability of ASE laser with transverse feedback was studied theoretically and experimentally. We found theoretically that a miniature OFFIRL with transverse feedback would give FIR laser with very broad frequency characteristics as shown in Fig.l.
The linewidth of optically pumped FIR laser everywhere in the sample tube of OPFIRL was studied theoretically. The NH<sub>3</sub> gas was chosen as the operating gas and three-level model was used for the theoretical calculation of the linewidth of FIR laser within the sample tube of the laser system. We found that the sample tube could be divided into three regions: A) The laser induced line narrowing region (L < 10 cm ), where the line centers of Is and Gs characteristic curve were approached with each other, so that the larger Is amplified by larger Gs and vice versa, and the linewidth of FIR laser became narrower and narrower after successive amplification in this region. B) The saturation broadening region ( L<sub>opt</sub> < L <10 cm), where Is was large and the Gs at the line center decreased considerably due to the gain saturation effect. In this region, the gain value at the line center was less than its value at off center, so that the spectral line became broader. C) The self-absorption narrowing region ( L < L<sub>opt</sub>). In this region the value Ip was less than its threshold value, and the molecules were not activated. The FIR signal was now interacted vith the unactivated molecular system and absorbed by the molecular system. The linewidth of FIR signal would be narrowed due to the absorption saturation effect.