A new analytical solution for coupled water-gas transport in unsaturated landfill cover system is proposed, which can consider transient diffusive-advective transport of gas under transient water transport condition. The proposed analytical solution is first verified against the laboratory measurements and numerical simulations. Using the proposed solution, parametric studies are conducted on the coupled transient behaviors of water-gas transport. The results show that ignoring the coupling effect can lead to significant error in gas transport results under various conditions, e.g., the surface gas emission flux is underestimated by about 28.3%similar to 79.8% due to ignoring the spatial and temporal variations of water content induced by transient water transport. The influencing parameters (i.e., initial saturation degree, rainfall patterns, and evaporation rate) all have significant impact on the coupled water-gas transport behaviors. The magnitude of the error induced by ignoring the coupling effect increases with increasing initial saturation degree and increasing evaporation rate (e.g., for initial saturation degree increasing from 0.35 to 0.95, the accumulated percolation at cover bottom increases by 10.9 times and the gas emission flux at cover surface decreases by 64.7%). The results highlight that it's imperative to consider the effect of transient water transport when one needs more accurate assessment of gas transport results in the cover. This analytical solution can also be utilized to aid landfill cover design and to verify other numerical models.
To further promote the research of bird's eye view(BEV)perception algorithms and improve the performance,the advantages and latest work of BEV perception were discussed,and the relevant datasets and performance evaluation metrics of BEV perception were introduced.The BEV perception processing methods in recent years were summarized,and BEV perception was categorized into three types,which were BEV Cameras,BEV Lidars and BEV Fusion based on the input data of BEV sensor,and in-depth descriptions of the three types of algorithms and solutions were provided.Among them,BEV Camera was classified into explicit transformation and implicit transformation according to geometric transformation methods,and the explicit transformation could be classified into"2D-3D"and"3D-2D"methods,while the implicit transformation could be classified into Transformer-based and multilayer perceptron(MLP)-based neural network modeling methods.BEV lidar could be classified into voxel-based method and Pillar-based method according to the method of point cloud feature extraction.BEV fusion could be classified into camera-lidar fusion,temporal-spatial fusion and depth-height fusion according to the form of input data from multiple sensors.In addition,this review also identified six major directions for future research in this field,aiming to provide valuable insights for researchers engaged in BEV perception algorithms and related technologies,and to encourage a broader academic community to devote increased attention and exploration to the research and application of BEV perception.
According to the basic situation of the bridge and the requirement of anti-ship collision level,a pontoon interception system consisting of floats,anchor chains,anchor anchors and cables was designed.A finite element model of the pontoon interception system and the ship was established,and the dynamic process of the ship hitting the interception system was simulated.A fluid-structure coupling method was used to consider the role of the flow field in the collision process,and the effects of different ship masses,velocities,impact points,and the number of anchorages on the interception effect were analyzed.Result shows that the designed interception system can effectively stop the ship for different tonnage and collision speeds to protect the bridge.When the tonnage of the ship increases from 5 kt to double the kinetic energy of 10 kt,the change of the maximum tension of the interceptor net and the anchor chain is less than 30%,which indicates that the interceptor system has a greater applicability.Interception time,vessel and anchor displacement are all much smaller with a double-anchored interception system,and the interception effect is better,while the anchor chain and the interception net axial force increase is not big.
An open-air traveling wave thermoacoustic generator was theoretically modeled by the transfer matrix method and the nonlinear dissipation model of the open end.The relationship among the real part of the impedance of the open end,the volume flow rate at the opening and the pressure loss coefficient affected by the geometry of the open end were obtained.The acoustic characteristic parameters of resonant frequency,internal pressure amplitude and sound pressure level at 1 m far away from the open end were theoretically analyzed.Experiments were carried out by using different resonators with different diameters and cone tubes with different angles.The influence of the length and diameter of the resonator on the frequency of the system was discussed.The results showed that the model in this paper can reflect the influence of the diameter and length of the resonant tube on the frequency,and the calculation error is less than 5％.The cone tube at the open end can reduce the energy loss during suction,and then significantly increase the pressure inside the device.When the cone tube is 40° at the opening and the diameter and length of the resonator is 46 mm and 730 mm,respectively,the sound pressure level at 1 m far away can reach 110.2 dB.
Energy saving has always been a concern in production scheduling, especially in distributed hybrid flow shop scheduling problems. This study proposes a shuffled frog leaping algorithm with Q-learning (QSFLA) to solve distributed hybrid flow shop scheduling problems with energy-saving(DEHFSP) for minimizing the maximum completion time and total energy consumption simultaneously. The mathematical model is provided, and the lower bounds of two optimization objectives are given and proved. A Q-learning process is embedded in the memeplex search of QSFLA. The state of the population is calculated based on the lower bound. Sixteen search strategy combinations are designed according to the four kinds of global search and four kinds of neighborhood structure. One combination is selected to be used in the memeplex search according to the population state. An energy-saving operator is presented to reduce total energy consumption without increasing the processing time. One hundred forty instances with different scales are tested, and the computational results show that QSFLA is a very competitive algorithm for solving DEHFSP.
