Gongcheng Kexue Yu Jishu/Advanced Engineering Science

The main purpose of video background separation is to extract objects of interest from the video, but it is still one of the most challenging tasks in computer vision and other fields due to the influence of noise and lighting changes. The truncated nuclear norm (TNN) algorithm is a classic robust principal component analysis (RPCA) algorithm, which is widely used to separate the background and the front of the video. However, the truncated kernel norm in this algorithm does not have a high degree of approximation to the rank function in the traditional robust principal component analysis, resulting in poor stability and low accuracy in separating the front and background of the video in some complex scenes. To solve this problem, this paper proposes an improved truncated nuclear norm (improved truncated nuclear norm, ITNN) algorithm. The algorithm first replaces the kernel norm in the TNN model with a non-convex γ norm, and analyzes that the non-convex γ norm has a higher degree of approximation to the rank function than the kernel norm . Corresponding model; secondly, in order to solve the proposed model, this paper introduces the generalized alternating direction method of multipliers (GADMM) to solve the model; finally, the proposed ITNN algorithm is applied to multiple public videos In the previous background separation experiment, and by showing the foreground effects of different videos, the effectiveness of the ITNN algorithm was verified from a visual point of view. At the same time, the F-measure value of the video foreground extracted by the proposed algorithm and the comparison algorithm is calculated, which further verifies the effectiveness of the ITNN algorithm from the perspective of quantification. In addition, the experiment also recorded the running time of the video front and background separation of each algorithm, which verified the efficiency of the ITNN algorithm. In a word, this paper verifies the effectiveness and superiority of the proposed ITNN algorithm in the separation of video front and background through experiments.

Rotary vane steering gear has the advantages of compact structure, high mechanical efficiency, and easy installation, and is widely used in ships. The existing rotary vane steering gear is a single-layer hydraulic swing cylinder, and the rotation range of the rudder blade is restricted by the structure of the swing cylinder and has saturated nonlinearity. In addition, the phenomena of rudder impingement, lag and running caused by hydrodynamic interference seriously affect the ship’s course control and rudder anti-roll effect. Aiming at the above problems, a new steering principle of compound structure swing cylinder is proposed based on the mathematical model of direct drive electro-hydraulic servo rotary vane actuator and the analysis of the interference of hydrodynamic force on rudder angle. The double-layer structure is adopted for the compound swing cylinder, the inner layer is rudder driving cylinder, the outer layer is torque decoupling cylinder. The inner and outer rotors rotate in the same direction, which can increase the working range of the rudder blade. Meanwhile, the torque decoupling cylinder rotor outputs boost torque acting on the rudder drive cylinder rotor, which can offset the load torque generated by the hydrodynamic force on the drive cylinder rotor. Improve the rotation accuracy of the rudder blade and solve the problem of force-position coupling in the movement of the rudder. The reverse rotation of the inner and outer rotors can make the steering gear brake and change direction in time, and improve the steering performance. The compound swing cylinder is used for the vane steering gear. The steering gear system has a large stability margin, with amplitude margin of 45.3 dB and phase margin of 99.2°, which meets the design index of servo system. Simulation analysis shows that, compared with the single-layer swing cylinder plus control strategy, the compound swing cylinder has faster response speed and no overshoot, the speed of reaching steady state increased by about 36%, the steady-state error is maintained within ±0.05° under external load interference. When tracking a slope signal with a slope of 0.01°/s, the steering accuracy can be maintained within the ±0.03° position error band, which has high position control accuracy.

Flow separation and vortical dynamics generated by second-order Stokes waves propagating over a submerged rectangular breakwater supported on a rubble mound were investigated using particle image velocimetry (PIV) technology and numerical model based on Reynolds–averaged-Navier–Stokes equations (RANS). Experimental wave surfaces show nonlinear deformation before and after the structure. The asymmetry and skewness of the weatherside wave profile are –0.21 and 0.04, respectively, which indicates a steep front face and gentle rear face. The asymmetry and skewness of the leeside wave profile are –0.39 and 0.99, respectively, which indicates more significant lack of symmetry relative to vertical and horizontal axes. Phase-averaged velocity and vortex fields calculated from PIV data show that clockwise and counterclockwise vortices are generated periodically on the weatherside and leeside of the structure. However, these vortices are not fully developed. The subsequent flow reversal moves the vortices towards the free surface or the structure to make them dissipated. The weatherside vortex pair is confined within a relatively narrow region of about 0.5 times Keulegan–Carpenter number from the weatherside of the structure, which implies smaller wave energy dissipation. Meanwhile, the leeside vortex pair is confined within a relatively wide region of about 1.0 times Keulegan–Carpenter number from the leeside of the structure, which indicates greater dissipation of wave energy. In addition, a small circulation system is found above the upstream shoulder of the rubble mound and its movement is confined within two times the unperturbed wave particle trajectory, which may lead to local scouring. A numerical wave flume was established based on RANS–VOF mode and then verified by experimental results. The applicability of different wave-making methods and the effect of energy dissipation by sponge layer were analyzed. The RANS–VOF model was then used to further study the flow separation of shear boundary layers. Numerical results show that the supply of vorticity mainly comes from the shear boundary layers at the surface of the structure. The adverse vorticity in the shear boundary layers is induced by the adverse pressure gradient imposed by the movement of the vortices previously shed from the structure. The generation, shedding, stretching, advection and dissipation of vortices is expected to significantly change the local flow around submerged structures and hence cause local scour as well as additional loading. Therefore, the effect of the complex flow induced by vortices should be taken into account in engineering design.

The double steel plate composite shear wall structure is widely used in the high-rise buildings due to its advantages of good integrity, high rigidity and high shear bearing capacity. In this paper, the mechanical characteristics of L-shaped section double steel plate composite shear wall structure were analyzed. The finite element software ABAQUS was used to model and analyze the L-shaped section double steel plate composite shear wall, and the results were compared with the experimental results, through the finite element parametric modeling, the influence and characteristics of the main parameters such as axial compression ratio, steel plate thickness, steel plate strength grade, concrete strength grade, end H-beam size and other parameters on the hysteretic performance of the shear wall were studied. Results showed that the finite element model fit well with the test results; the bearing capacity of specimens increased with decreasing height–width ratio; increasing the thickness of the steel plate and the size of the H-beam at the end, increasing the strength grade of the steel plate and the strength grade of the concrete would increase the bearing capacity of the L-shaped section double steel plate composite shear wall; the strength of the concrete and the addition of H-shaped steel at the flangeless web were the main factors affecting the bearing capacity. It is recommended that the design axial compression ratio of the L-shaped section double steel plate composite shear wall should be restricted under 0.4.

In order to study the effect of Nano–particles on the low organic waste activated sludge fermentation performance. The WAS were fermented in the nanometer CuO (Nano–CuO) and nanometer ZnO (Nano–ZnO) fermentation systems. The results showed that the hydrolytic acidizing property of Nano--ZnO fermentation system was significantly higher than Nano--CuO fermentation system. Protease increased with the addition of Nano--ZnO and Nano--CuO, and the maximal value was 25.15 EU/mg VSS (Nano--CuO) and 46.71 EU/mg VSS (Nano--ZnO), respectively. The α--glucosidase increased firstly and then decreased with the addition of Nano--ZnO and Nano--CuO, the maximal value were 0.0037 EU/mg VSS of 10 mg/L (Nano-- CuO) and 0.0039 EU/mg VSS of 1 mg/L (Nano--ZnO), respectively.Alkaline phosphatase and acid phosphatase declined with the Nano–ZnO and Nano–CuO addition however the Nano–ZnO system was higher than Nano–CuO system. The coenzyme 420 declined with the increase of Nano–ZnO but increased with the increase of Nano–CuO . Theterrimonas , chryseolinea and ferruginibacter were enriched in Nano–ZnO fermentation system which resulted in the higher SCFAs production.