Gongcheng Kexue Yu Jishu/Advanced Engineering Science

Hysteresis is one of the important characteristics of automatic adjustment of river system, while there are few studies on the law of sediment delayed response in the Three Gorges Reservoir (TGR). Based on the delayed response model, the measured data were analyzed and the delayed response model was modified by considering the sediment concentration and sediment particle size in order to construct the delayed response model in accordance with the characteristic of sediment deposition in TGR. Firstly, the changes of water and sediment conditions and sediment deposition characteristics since the impoundment of TGR were counted, and the influence of cascade reservoirs in the upper Yangtze River was analyzed. In order to simulate and analyze the sedimentation delayed response law in different periods of TGR, the existing model was used and modified. Based on the existing and modified response model simulation results, it can be seen that 1) The modified response model can better simulate the sediment deposition process of TGR after the impoundment of cascade reservoirs because of the consideration of sediment concentration and sediment particle size. 2) After the impoundment of cascade reservoirs, the fluctuation range of inflow and sediment decreases, the sediment inflow of TGR is more concentrated in flood season, both of which make the channel adjustment rate increase, the delayed response time of sediment deposition in TGR is shortened from the early 4 years to the early 3 years. 3) After the impoundment of cascade reservoirs, the influence weight of sediment concentration on the sediment deposition process increases, while the influence weight of flow and water level in front of dam decreases. By using the modified model, it can be seen that the inflow of sediment concentrates more in the flood season, which make the delayed response time of sedimentation in TGR shorten, and the influence weight of sediment on the sediment deposition increases.

Onshore ground motions were widely used for seismic analysis of sea-crossing bridges, and the difference between the onshore and offshore ground motions were ignored. Due to soil loss around piles scoured by water for a long time, the stability of substructure of bridge in marine environment was reduced. Taking an approach part of a sea-crossing bridge as an example, a finite element model for this approach part was built by using the ABAQUS software. The pile-soil effect and hydro dynamic force were considered in the model. The probabilistic seismic demand analysis method was used with the fragility analysis of bridge piers under onshore and offshore ground motions with different scour conditions. By drawing the transcendence probability vulnerability curves and the transcendence probability increase diagrams of piers and bearings, the damage regularities of bridges under the onshore and offshore ground motions and different scour depths of bridges key components were studied. The results showed that the bridge piers were more vulnerable under offshore motions than that under onshore motions. With the increase of the local soil scour depth, the failure probability of the bridge piers and bearings increased. The effect of scour depth had a more obvious effect on the failure exceeding probability of the piers. The failure exceeding probability of the piers in bridge longitudinal direction was higher than that in bridge transverse direction under the same intensity of ground motion. The bearings were more vulnerable than bridge piers under the same working conditions. The increase of failure exceeding probability of the bearings under the offshore motions was also generally higher than that under the onshore. As the scour depth increased, the failure exceeding probability of the bearing gradually increased. Comparing with the onshore motions, the scour depth had a more obvious influence on the failure exceeding probability of bridge piers under the offshore motions with the increase of the ground motion intensity.

As the basic part of motion of humanoid robots, human-like motion planning of the anthropomorphic arm is always one of the research hotspots and difficulties. A novel human-like motion planning method based on movement primitives was proposed. This method can satisfy the feature of arm motion and improve the accuracy. Firstly, the arm structure was decoupled and the arm model was built to express different arm movements. The methods of extraction and connection about movement primitives were established. The mapping relations between the arm models and inverse kinematic (IK) solutions were established. Meanwhile, a motion framework was proposed. The joint trajectories of a certain platform can be generated to accomplish required tasks with this motion framework. Secondly, according to the motion features of different movement primitives, the associated Human Performance Measures for different movement primitives were constructed to solve the IK problem. Finally, the proposed method was verified by the similarity experiment and the human-like movement experiment for the general motion of humanoid robot NAO. In the similarity experiment, the robot NAO generated the human-like movements with the proposed method. The motion data were compared with the real data generated by humans. All the errors were less than 1 cm, which satisfied the accuracy requirements of human-like movements. In the human-like movement experiment, the robot NAO performed a human-like arm movement with the proposed method. The proposed method was also compared with the minimum total potential energy method and the last norm algorithm. Using the proposed method, 7% and 58 % increase in similarity were achieved respectively, compared with those two methods. With the proposed method, the complex motion models were decoupled into different simple sub-movements and the classification of the movements reduced the calculation amount. The experiments proved that the anthropomorphic arm can generate human-like movements accurately.

Industrial and agricultural activities lead to increasing soil cadmium (Cd) pollution. As an important functional component of soil colloid, both montmorillonite (Me) and humic acid (HA) have good adsorption properties for Cd. Four molecular weight grades of HA were obtained by tangential flow ultrafiltration. FTIR, element determination, functional group titration were used to study the effect of HA with different molecular weight on the adsorption of Cd on montmorillonite and the mechanism of action. The results showed that with the increase of molecular weight of HA, the content of hydroxyl and carboxyl groups decreased while the phenolic hydroxyl group and methyl group increased, the aromaticity increased, the hydrophobicity became stronger, and the pH value increased. The contents of Cd and HA adsorbed by montmorillonite in the ternary system increased with the increase of molecular weight. When the initial concentration of Cd was 50 mg/L, the adsorption capacity of HA, HA1, HA2, HA3, HA4 montmorillonite system for Cd was 1.99, 2.11, 2.46, 4.12, 4.88 mg/g, respectirely. And the Cd adsorbed under the action of each molecular weight HA was mainly reducible state. The smaller HA was easier to compete for the adsorption of the Cd already bound on the surface of montmorillonite, and due to its strong hydrophilicity, the Cd adsorbed by small HA would be brought into the solution, reducing the content of Cd absorbed by the system. With the increase of molecular weight, its competition effect with montmorillonite was reduced, and the HA was difficult to enter into the montmorillonite layers. At this time, under the hydrophobic effect, the large molecule HA adsorbed Cd would cover the surface of montmorillonite, thus increasing the adsorption amount of Cd in the system.

The composite strengthening method with near surface mounted steel bars and wrapped fiber reinforced polymer strips can improve the bearing capacity and deformation behavior of timber columns effectively, and enhance their working performance greatly. To propose the load-bearing capacity formula of short timber columns strengthened with near surface mounted steel bars and wrapped carbon fiber reinforced polymer (CFRP) strips, a total of 42 reinforced specimens (12 groups) were tested under axial compression. The test results indicated that the failure of timber columns mainly occurred where the initial defects concentrated , and the bearing capacity and deformation performance of timber columns could be improved through the composite strengthening, showing significant strengthening effectiveness.Based on the typical strength model of concrete columns wrapped with fiber reinforced polymer strips, three strength models of timber columns with wrapped CFRP strips by analyzing and fitting the relevant experiment data were proposed. Through the comparison between theoretical and test values, the feasible strength model for the calculation of timber columns confined by CFRP strips was selected, and then the calculation formula of bearing capacity for the circular timber columns with composite reinforcement method was obtained. According to the additional experiment results and the comparison calculation for test data in existed research, it can be obtained that the theoretical calculation was able to predict the test results,which verified the reliability of the formula for the calculation of the strengthened timber columns' load-bearing capacity.