Gongcheng Kexue Yu Jishu/Advanced Engineering Science

In order to alleviate the burden of continuous increasing energy consumption falling on the power system and solve the complex calculation problem in the joint dispatching of large-scale electrical equipment, a hybrid decentralized optimization of dispatching the large-scale controllable appliances and energy storage equipment considering demand side response was proposed in this paper. Firstly, two mathematical models of controllable electrical equipment load and energy storage equipment were established. On this basis, a mixed integer non-linear centralized optimization model was mathematically formulated under the constraints of the operation characteristics of the system and equipment, with the objective of minimizing the sum of electricity purchase cost, users’ dissatisfaction cost and energy storage equipment loss cost. Secondly, for tackling the difficult nonlinear centralized optimization problems of high dimensionality, multi objectives and multiple constraints, the Lagrange relaxation method was used to decompose the problem into two sub-problems, namely, optimally scheduling the controllable electrical equipment load and optimizing the dispatch of the energy storage equipment. Then, the former was further decomposed into optimizing dispatch of each controllable electrical equipment and solved by the interior point method, while the latter was decomposed into a set of mixed integer linear optimization sub-problems of scheduling each energy storage equipment and solved in parallel by the Benders decomposition method. Thirdly, a series of numerical simulations together with comparison analysis were performed to verify the effectiveness and superiority of the proposed dispatch optimization method. For example, the optimization objective value and the optimal dispatch solution corresponding to the proposed method were illustrated and compared with those of the centralized method to demonstrate the effectiveness of the hybrid decentralized optimization method. And the influence of different numbers of dispatching equipment on the computation efficiency was investigated on the centralized and decentralized optimization method to show the superiority of the proposed hybrid decentralized optimization method. According to the numerical simulation results, the optimization objective value of the proposed method is basically consistent with that of the centralized. Moreover, the identified dispatch solution enables to efficiently respond to the time-of-use and results in good effect of peak-shaving and valley-filly. Besides, the calculation efficiency of the proposed hybrid decentralized optimization method is of high computation efficiency and not affected by the increasing number of the schedulable electrical equipments.

Exploring the fluid flow mechanism in rock masses is of great significance for preventing water inrush during excavation of underground constructions such as tunnels. Quantitative descriptions of the hydraulic properties of single rock fracture subject to normal stresses and shear displacement are the basis for understanding the coupled hydro-mechanical processes in fractured rock masses; however, the quantitative relationships among stress, deformation, aperture, inertial coefficients have not been developed in previous works. Granite specimens with single fracture were prepared and flow tests with variable water heads were carried out, in which incremental normal stresses were applied at each fixed shear displacement to characterize the evolution of permeability. The surface morphology of fractures was digitalized using a three-dimensional high-resolution scanning system. A self-designed numerical code was employed to calculate the deformation of fractures under normal stresses based on the framework of variational principles in contact mechanics. The fracture deformation and void space variation under different shear displacements and normal stresses were investigated. By extracting the aperture data and solving Navier–Stokes equations using COMSOL software, a series of numerical simulations were performed to investigate the nonlinear flow behavior of fluids within fractures under different shear displacements and normal stresses. The relationships among shear displacement, normal stress, void space distributions and parameters describing the nonlinear flow were quantitatively analyzed. The results showed that the fracture surface damage areas obtained from the experiment agreed well with the numerical simulation results, which verified the reliability of the deformation calculation code. The normal stress and the shear displacement exhibited a decreasing power function and an increasing exponential function with the fracture aperture, respectively. The increase in the shear displacement resulted in the concentration of contact areas. The inertia coefficient B in the Forchheimer equation and the critical hydraulic gradient Jc could quantitatively characterize the nonlinear flow behavior. B and Jc exhibited decreasing power functions with the shear displacement. The increasing rates and ranges of Jc and B decreased gradually as shear advances. When the shear displacement increased from 2 to 8 mm, the range of Jc decreased from 6.10×10–3 to 1.20×10–3 by a rate of 80.32%. The range of B decreased sharply from 2.97×1014 Pa·s2·m–7 to 2.43×1013 Pa·s2·m–7 by a rate of 91.28%. A similar power function relationship existed between RSD～B and between RSD～Jc. Finally, a predictive function was proposed to quantify the onset of nonlinear fluid flow through fractures.

Thermal error prediction and compensation of CNC machine tools is an important technology to improve the machining accuracy and reliability of CNC machine tools. The thermal error of machine tool is time-varying and nonlinear. To improve the accuracy and robustness of thermal error prediction, a numerical control machine tool thermal error prediction model based on attention mechanism and deep learning network was proposed. Using the data conversion strategy, the original temperature data of CNC machine tool was transformed into temperature image, which could be directly used as the input of deep learning network. The complete information of the temperature field of the machine tool was retained by converting the temperature field data into the temperature image points. At the same time, the nonlinear and coupling problems between the temperature measuring points were avoided by using the deep learning modeling method. A recognition network of temperature sensitive points based on attention mechanism was proposed. According to the correlation degree between temperature measuring points and thermal error, different weights were given to each temperature measuring point to avoid the disadvantages of artificial selection of temperature measuring points. A 12–layer deep CNN learning prediction network was established to mine the nonlinear mapping relationship between temperature image and thermal error by using its powerful image feature learning ability. This method does not need to preselect the key temperature points, retained more relationship between thermal error and machine temperature characteristics, and can significantly improve the prediction accuracy of the model. In order to improve the accuracy and generalization ability of thermal error model, dropout regularization method and Adam optimization algorithm were introduced to optimize the structure and parameters of deep convolution neural network. The method shows high prediction accuracy in the thermal error verification of G460L CNC lathe. Compared with the thermal error models based on BP neural network, multiple regression and CNN network, the proposed method performs better in generalization performance.

Landslide dams are usually formed instantaneously by natural forces, the accumulation bodies have the characteristics of complex space structure, wide gradation of dam materials, poor dam stability, and they are easy to fail under the flow erosion. As a major natural disaster of flood and drought, safety evaluation and disaster prediction of landslide dams have been the focus of attention by the scholars around the world, but many questions remain unanswered, which are mainly manifested in: 1) Accumulation bodies are composed of natural wide-graded rockfill materials with significant state-dependent correlation, there is a lack of the state-dependent dilatancy theory and constitutive model of wide-graded rockfill materials. 2) After the formation of landslide dams, they would be affected by external loads, such as the rise of upstream water level of dammed lake, continuous unsteady seepage, landslide surge in the dammed lake, and earthquake, there is also a lack of standards and methods for stability evaluation. 3) Due to the lack of necessary flood relief facilities, the landslide dams are prone to fail; under the action of outburst flow, obvious nonlinear characteristics are manifested during the breach development, as well as strong unsteady flow characteristics of the hydraulic elements; there is a lack of numerical models for landslide dam breaching which can reflect the erosion mechanisms of wide graded materials. Therefore, it is necessary to conduct integrated scientific measures, such as field explorations, multi-scale physical model tests, and numerical simulation methods, so as to reveal the physical description, internal structure, macroscopic mechanical properties of the landslide dams and their spatial and temporal variations; and then, a state-dependent (i.e., gradation, pore ratio, and stress level) dilatancy equation for wide-graded landslide deposit will be presented, and a generalized elastic-plastic constitutive model that can adapt to complex stress paths and the limit equilibrium analysis method of landslide dam body will be established. Large-scale hydraulic model tests and centrifugal model tests of dam breaching will be conducted to reveal the dynamic erosion characteristics of landslide dam materials and the evolution law of breaches under the action of unsteady flow. Subsequently, the erosion equation of sand-laden flow under the dynamic boundary condition by the action of unsteady flow will be established, and the numerical model for dam breach process considering the fluid-solid interaction will be put forward to realize the numerical simulation of the characteristics of water flow movement, the law of dam material transport, the evolution process of breaches, and the structural instability of landslide dam in the whole process of overtopping and seepage failure. Integrating the reliability theory and numerical simulation method of dam breach process, an integrated numerical simulation platform for seepage, deformation, stability, and failure process of landslide dams considering fluid-solid will be developed; consequently, the theoretical system and method of safety evaluation and disaster prediction of the full-life cycle of the landslide dams will be established. The expected results achieved in the project will provide scientific theory and key technological support for improving the decision-making level of disaster prevention and reduction of landslide dams in China.

The mechanical properties of the interface between soil and structure have always been a hot topic in geotechnical engineering. In order to explore the interfacial shear characteristics of non-water reaction polymer and concrete, the effects of vertical stress and shear rate on shear strength and shear modulus of polymer concrete interface were studied based on monotonic direct shear test. The experimental results showed that: under the given vertical stress and shear rate, with the increase of shear displacement, the polymer concrete interface presented shear softening phenomenon. The shear rate had little effect on the interfacial shear strength, cohesion and friction angle, but had a significant impact on the interfacial shear modulus, and the shear modulus value decreased with the increase of shear rate, and the decrease amplitude was obvious; the vertical stress had a significant impact on the shear strength and shear modulus of polymer concrete interface, and the shear strength and shear modulus of polymer concrete interface changed with the increase of shear rate. The vertical stress increased continuously. At the same time, the hyperbolic constitutive model formula of polymer concrete interface was systematically deduced, and the validity of the model was preliminarily verified according to the relevant experimental results.