Instability inspection of parametric vibrating rectangular Mindlin plates lying on Winkler foundations under periodic loading of moving masses

Parametric resonance is one of the most important issues in the study of dynamical behavior of structures. In this paper, dynamic instability of a moderately thick rectangular plate on an elastic foundation is investigated in the case of parametric and external resonances due to periodic passage of moving masses. The governing coupled partial differential equations (PDEs) of the system, with consideration of the first-order shear deformation theory (FSDT) or Mindlin plate theory, are presented and they are reduced to a set of ordinary differential equations (ODEs) with time-dependent coefficients using the Galerkin procedure. All inertial components of the moving masses are adopted in the dynamical formulation. Instability survey is carried out for three different loading trajectories considerably interested in many practical applications of the issue, i.e. rectilinear, diagonal and orbiting trajectories. In order to analyze the resonance conditions, the incremental harmonic balance (IHB) method is introduced to calculate instability boundaries, as well as external resonance curves in parameters plane. A comprehensive study is done to assess effects of thickness ratio and foundation stiffness on the resonance conditions. It is found that an increase in the plate's thickness ratio leads to a reduction in values of critical parameters. Moreover, it is observed that in creasing the foundation stiffness moves the in stability regions and resona nee curves to higher frequencies of the moving masses and also leads to further stability of the parametrically excited system at lower frequencies. Time response simulations done via Runge-Kutta method confirmed the results predicted by IHB method.

Enhancing oxygen evolution reaction by cationic surfactants

Oxygen evolution reaction is critical for water splitting or metal-air batteries,but previous research mainly focuses on electrode material or structure optimization.Herein,we demonstrate that surfactant modification of a NiFe layered double hydroxide (LDH) array electrode,one of the best catalysts for oxygen evolution reaction (OER),could achieve superaerophobic surface with balanced surface charges,affording fast mass transfer,quick gas release,and boosted OER performance.The assembled surfactants on the electrode surface are responsible for lowering the bubble adhesive force (~ 1.03 μN) and corresponding fast release of small bubbles generated during OER.In addition,the bipolar nature of the hexadecyl trimethyl ammonium bromide (CTAB) molecule lead to bilayer assembly of the surfactants with the polar ends facing the electrode surface and the electrolyte,resulting in neutralized charges on the electrode surface.As a result,OH-transfer was facilitated and OER performance was enhanced.With the modified superaerophobic surface and balanced surface charge,NiFe LDHs-CTAB nanostructured electrode showed ultrahigh current density increase (9.39 mA(mV·cm^2)),2.3 times higher than that for conventional NiFe LDH nanoarray electrode),dramatically fast gas release,and excellent durability.The introduction of surfactants to construct under-water superaerophobic electrode with in-time repelling ability to the as-formed gas bubbles may open up a new pathway for designing efficient electrodes for gas evolution systems with potentially practical application in the near future.

Comprehensive Evaluation of OxyCup Process for Steelmaking Dust Treatment Based on Calculation of Mass Balance and Heat Balance

Through the mass balance and thermal balance calculation for a typical OxyCup （or OxiCup） furnace process featuring a capacity of 380 kt/a of steel plant residuMs, the material flow and thermal flow diagrams were firstly obtained. Then, the performance of the main fuel in the OxyCup process, i.e. coke and carbon dust, was ana lyzed, and the results indicated that coke was mainly used as the stock column skeleton for the furnace and exothermal agent with a weak reduction ability; whereas carbon dust was mixed in the C-brick to reduce the iron oxide. In addition, the comparison between OxyCup process and traditional blast furnace process indicated that the reduction and melting processes in the OxyCup process were relatively isolated, while in the traditional blast furnace process, they were mixed with each other in the high temperature zone. Moreover, oxidizing atmosphere is necessary in part of the OxyCup furnaces to ensure the complete combustion of part of the coke, while only reducing atmosphere is al lowed in traditional blast furnaces. Finally, it was confirmed that oxygen enrichment can make a remarkable increase of the energy income and high temperature blast makes oMy a small contribution to energy income as the energy from the combustion of carbon takes up nearly 90% of the total income.