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61.
The distribution and transfer mechanism of MnS inclusions are distinguished from the solute segregation in a 500 kg steel ball. The increase of MnS inclusions is obvious from the surface to the center of the steel ball, while the increase of solute content is slight. The massive MnS inclusions converge in the channel zone and in heterogeneous zones. During solidification, the interface tension drives MnS inclusions to the frontier of the dendritic zone. Some inclusions trapped may float to induce the channel zone. Solidification contraction tears such channel zone to attract more melt enriched with inclusions. Some inclusions converge in the extra-dendritic melt. At later solidification stage, solidification contraction dominates the macro-distribution of extra-dendritic melt to produce the heterogeneous zones. 相似文献
62.
Lai Wei Ryan McCloy Jie Bao Jesse Cranney 《American Institute of Chemical Engineers》2022,68(11):e17830
Modern chemical processes need to operate around time-varying operating conditions to optimize plant economy, in response to dynamic supply chains (e.g., time-varying specifications of product and energy costs). As such, the process control system needs to handle a wide range of operating conditions whilst optimizing system performance and ensuring stability during transitions. This article presents a reference-flexible nonlinear model predictive control approach using contraction based constraints. Firstly, a contraction condition that ensures convergence to any feasible state trajectories or setpoints is constructed. This condition is then imposed as a constraint on the optimization problem for model predictive control with a general (typically economic) cost function, utilizing Riemannian weighted graphs and shortest path techniques. The result is a reference flexible and fast optimal controller that can trade-off between the rate of target trajectory convergence and economic benefit (away from the desired process objective). The proposed approach is illustrated by a simulation study on a CSTR control problem. 相似文献
63.
Channa Wang Ling Li Huihua Wang Tianpeng Qu Jun Tian Deyong Wang Zhenhui Kang 《加拿大化工杂志》2020,98(8):1784-1793
Cost-effective catalysts for hydrogen evolution reaction (HER) are attractive for sustainable production of H2 fuel. Herein, a series of tunable Ni/Fe-Mo carbide catalysts have been synthesized via a sol-gel method coupling with a subsequent high temperature carbonization process. The amount of nickel and iron was tuned in the Mo7/C precursors, accomplishing a favourable performance of noble-metal-free electrocatalysts for HER. As expected, the designed Ni10Fe4Mo7/C catalyst displays an enhanced catalytic activity toward hydrogen production with an ultralow overpotential (η10 = 110 mV) and striking kinetics (ηonset = 58 mV, k = 54 mV · dec−1) in the alkaline electrolyte (1 M KOH), which are comparable to those of the commercial 20% Pt/C catalyst. Such excellent performance of Ni10Fe4Mo7/C could be attributed to the high intrinsic activities of Ni-based alloys (NiMo4) and Mo2C, as well as to the lattice contraction in the Mo2C unit cell, in accordance with its high electrochemical surface area (~133 m2 · g−1) and low charge-transfer resistance (~31.5 Ω) for the associated electrode. 相似文献
64.
65.
研究通过自行配制的防裂高效减水剂改善路面水泥混凝土的力学性能、细观结构、收缩性能以及耐磨性能,以提高水泥混凝土路面的使用质量和寿命,并以铺筑试验路检测数据检验实际效果,为在特殊路段使用水泥混凝土路面提供广阔的应用前景. 相似文献
67.
68.
The present numerical study concentrates on the effects of moderate and high Reynolds numbers on the laminar flow of a non-Newtonian rigid viscoplastic (Bingham) fluid through a sudden contraction in a pipe. The flow is assumed to be steady, incompressible, and isothermal. Results are presented for a wide range of the governing Reynolds and yield numbers and the significant effects of these two parameters both on the integral and local kinematic properties of the flow field are established. Low yield numbers result in the disappearance of the recirculating flow region at the corner replacing it with a region of very low rates of deformation. The evolution of the centerline velocity in the vicinity of the contraction plane is shown to be independent of the yield number and dependent on the Reynolds number, while the concavities in the streamwise velocity profiles appearing at high Reynolds numbers are independent of the yield number. The pressure losses through the contraction increase with yield number with the effect being more pronounced at lower Reynolds numbers. 相似文献
69.
70.
Deterministic simulation approach was applied to simulating viscoelastic complex flows,in which,the SIMPLE algorithm based on collocated grid was used to solve the conservation equations on the macroscopic level and the spectral method was used to solve the Fokker-Planck equation on the mesoscopic level.Here,the transient 4∶1 planar contraction flow for dilute polymer solution was computed by using the coupled technique and the calculated polymeric stress distributions at steady state were identical with the results of continuum approach as well as the corresponding references.Therefore,the presented results indicated that the SIMPLE algorithm based on collocated grid coupled with the spectral method can be used to simulate viscoelastic complex flows effectively.Moreover,the influence of Deborah number and viscosity ratio on polymeric stress was also investigated. 相似文献