The inter-provincial electricity spot market(IPESM) tariff mechanism is different from the calculation of tariffs under the traditional spot market, which is mainly affected by the declared price and declared capacity of market players, transaction paths, transmission capacity of the channel as well as the ratio of supply and demand, and the research on the prediction of transacted tariffs in the IPESM is of great significance. In this paper, an method based on a graph convolutional network is proposed for predicting transaction fees. Firstly, the input matrix of the prediction model is established by considering the inter-provincial trading paths and the information of market players. Secondly, the GCN was combined with the IPESM trading model for the prediction of electricity turnover and turnover price. Finally, the model prediction results were evaluated using MAPE and MAE. The simulation results show that the graphical neural network can effectively identify the mapping relationship between the characteristics of trading channels and declaration volume and the transacted electricity price in IPESM, and the results have high accuracy.
In this paper, four binary hard sphere crystals were numerically constructed by discrete element method (DEM) through different packing modes under three-dimensional (3D) mechanical vibration. For each crystal, a modified Voronoi tessellation method (called radical tessellation) was utilized to quantitatively investigate the topological and metrical properties of radical polyhedra (RPs). The topological properties such as the number of faces, edges, vertices per RP and the number of edges per RP face as well as the metrical properties such as perimeter, surface area, volume, and relative pore size per RP were systematically characterized and compared. Meanwhile, the mechanism of the binary hard sphere crystallization was also investigated. The results show that the packing sequence and pattern of the large spheres can determine the structure of the binary hard sphere crystal. The RP structures and their metrical and topological properties of the four binary hard sphere crystals (even the packing density of the two crystals is the same) are quite different. Each property can clearly reflect the specific characteristics of the corresponding binary hard sphere crystalline structure. The obtained quantitative results would be useful for the deep understanding of the structure and resultant properties of binary hard sphere crystals.
Abstract The inflow uniformity before selective catalytic reduction (SCR) catalyst carrier is a major issue for DeNO x capability of diesel engine after-treatment. Through the construction of the numerical model and CFD simulation of six perforated plate variations with different structural and positional characteristics, the influence of perforated plates on the uniformity of the airflow velocity at the inlet of the SCR catalyst carrier was analyzed. Comparison of different perforated plate variations shows that the encircling flow is a major hindrance to achieve higher inflow uniformity. Enclosed flow passage can remove the encircling flow and increase inflow uniformity at the cost of increased pressure drop. Rational layout of the perforated plate can achieve uniformity increase, while decrease pressure drop. High-velocity exhaust coupled with larger holes can improve both uniformity and pressure drop. The uniformity index increased from 97.6% of the original design to 98.7% of the optimized design, while pressure drop increased from 11.20 to 12.09 kPa. Weighing the relationship between inflow uniformity and pressure drop is an issue worthy of attention.
The piston cooling of engines are usually controlled by the “cocktail shake” mechanism inside the single cooling cavity, according to most studies of piston cooling published before. This paper researched on flow in multiple cooling cavities which are extensively used on pistons of low-speed engines, revealing that the flow in multi-cavity is quite different from that in a single cooling cavity. In this work, complete reciprocating cycles are captured to study the gas-liquid two-phase flow behavior of each cavity inside the multi-cavity piston, by conducting synchronous experiments using benchmarked high-speed camera and a real size piston. The effects of different engine speeds (40–64 rpm) and different inlet pressures (0.1–0.3 MPa) were investigated. Both the inner and annular cavities are cooled mainly by cocktail shaking, but two cooling mechanisms are observed in the outer cavity, the oscillatory effect and cyclonic effect, providing further development on piston cooling studies. The cyclonic effect enhances the heat transfer capacity of the sidewall surfaces. The coupling effect between multiple cavities produces a secondary mixing effect of the liquid and improves the overall turbulence. In this paper, a comprehensive analysis of the flow mechanism within a typical multi-cavity piston is presented.
Limited understanding of how recycled aggregate (RA) affects the mechanical behaviour of recycled aggregate concrete (RAC) hinders its widespread adoption for sustainable construction. This study addresses the knowledge gap by employing discrete element method to investigate the impact of RA components on RAC mechanics. Results reveal that old aggregates, constituting the dominant volume within RA, determine the overall quality of RA. The mechanical properties of attached mortar and old ITZ can influence the formation of localised microcracks, their influence on the overall mechanical behaviour of RAC becomes negligible when the attached mortar content falls below 30%. Conversely, the strength of ITZ formed between the attached old mortar and the new mortar exhibits a significant influence. In essence, the findings suggest that the influence of RA components on RAC's mechanical performance resembles the well-known "bucket effect" concept. Strategically improving the weakest component within RA could achieve a stiffer and stronger RAC.
When a vibrating thin structure moves in a heavy flow field, the effect of sound waves on the structure cannot be ignored. This effect is especially pronounced when the relative velocity of the structure and the flow field increases. The hybrid numerical method of finite element method (FEM) and convective boundary element method (BEM) is proposed to solve acoustic-structural interaction problems in uniform relative motion between structure source and fluid. Besides, an acoustic-analogy Lorentz transform is proposed to handle the direct convective boundary integral equation (BIE), which makes the convective BIE has the same form as traditional BIE so that there are no more convective terms and extra singular integrals. The continuity condition at the fluid-structure interface is also proposed to generate the coupling equation. Compared with the traditional FEM, this hybrid method has the advantages of greatly reducing the number of finite elements outside the structure as well as automatically satisfying the radiation condition at far field. And compared with the direct convective BIE, this method reduces the computational complexity and time. It is potential to deliver a solver with higher accuracy and less memory consumption. Some numerical examples are designed to study the influence of the convective effect. Keywords: Acoustic-structural interaction, Finite element method, Boundary element method, FEM-BEM coupling
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