As the number of Internet of Things Devices (IoTDs) increases, the building Structural Health Monitoring (SHM) system is subject to the enormous amount of data collected from sensors. To tackle this challenge, we investigate an Unmanned Aerial Vehicle (UAV)-enabled Wireless Powered Communication Network (WPCN) in a building SHM scenario where a UAV is dispatched to provide wireless charging and data relaying services for IoTDs on the building. For preventing the channel blockage caused by the building, we place the UAV and Access Points (APs) in specific trajectory and locations, respectively. To improve the system's throughput, we maximize the minimum data volume among devices in a given period by formulating an optimization problem in which we jointly optimize the link schedule, the power and time allocation and the hovering positions of the UAV. However, the formulated problem is a mixedinteger nonlinear programming and is hard to solve. Therefore, we adopt a bottleneck-aware idea to reduce the dimensionality of the optimization variables in order to obtain a simplified problem that can be solved in a low-complexity way. Also, the Block Coordinate Descent (BCD) method is applied to reduce the complexity of the problem. Meanwhile, we further propose a method to deal with the heterogeneous problem for improving the generalizability of our algorithm. To estimate the performance of our proposed algorithm, we compare it with the Monte Carlo (MC) method, Game Theory (GT) and Particle Swarm Optimization (PSO). The simulation results indicate that our algorithm can obtain better performance.
In this presented work, by the seepage experiment for three groups of shale ceramsite concrete with different mixing ratio, it produced its impermeability mark and analyzed how the three factors of pressure holding time, water cement ratio and ceramsite pre-wetting time to impact the penetration depth; also a three-layer neural network model was built up by collecting 20 groups of testing and experiment data of actual projects data of ceramsite concrete chloride penetrability, and performed the chloride experimental simulation and prediction with the model, got comparatively accurate predicted values of chloride permeability coefficient.The study results provide some reference for similar studies.
New full hall scaffolds with pulley-clip style formwork support system is adopted in the concert hall of Changsha. This paper presents the concept of the complete equivalent initial imperfection according to the characteristics of too many influential factors on the high formwork supporting frame,then makes the complete equivalent initial imperfectione equivalent to assumed equivalent horizontal load in order to ensure the safety of the frame. At the same time, it gets a three-dimensional model by the general finite element software ANSYS 10.0. Based on the results of experiment and finite element analysis, it gets the recommended value of assumed equivalent horizontal load. The study on the high formwork supporting frame with pulley-clip style provides some reference for other similar projects.
Nanoscale cementite can be obtained in 0.17% carbon steel during isothermal treatment at 500oC after ultra fast cooling (UFC) and thermo-mechanical treatment. The precipitation strengthening contribution to yield strength was more than 250 MPa, when the heat treatment time was less than 20 min. The carbon diffusion is impacted by Mn and Si, which are redistributed during the precipitation process. All the effects induced by substitutional elements can be manifested through the restricted carbon diffusion, which is equal to the carbon diffusion multiplied by adjustable parameters. Based on this, a kinetic model has been adapted to simulate the precipitation behaviors of cementite involving the evolution of the number density per unit volume, radius of cementite over time, and the evolution of carbon concentration in matrix. An excellent agreement in mean radius of particles between the predictions of the model and experimental observations was obtained. It was found that the nucleation period of cementite was very short and did not exceed 0.2 s, and there was an overlap between the nucleation period and the growth period, and the coarsening period began at about 1s. In the growth stage, the carbon concentration in the matrix dropped rapidly and the mean radius of particles increased quickly. In the coarsening stage, the carbon concentration remained unchanged and the number of particles per unit volume fell sharply.
This thesis investigated the mechanical property of the semi-rigid steel beam-column connection and its influence upon the propery of the framework; grounded on several foreign common mathematical models on the moment-rotation relationship of semi-rigid connection, and on the basis of exponent function model, it derived the ultimate bearing capacity (Mμ) and initial connection stiffness (Rki) which act as controlling function in the formula. Also, it imitated the typical connection of top-seat-angle with double web-angle, ensured its moment-rotation curve, and provided a reference for the analysis of the ultimate bearing capacity in the second-order effect of light steel frame structure.
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