Three-dimensional mixed convection flow with variable thermal conductivity and frictional heating

In this article,three-dimensional mixed convection flow over an exponentially stretching sheet is investigated.Energy equation is modelled in the presence of viscous dissipation and variable thermal conductivity.Temperature of the sheet is varying exponentially and is chosen in a form that facilitates the similarity transformations to obtain self-similar equations.Resulting nonlinear ordinary differential equations are solved numerically employing the Runge-Kutta shooting method.In order to check the accuracy of the method,these equations are also solved using bvp4c built-in routine in Matlab.Both solutions are in excellent agreement.The effects of physical parameters on the dimensionless velocity field and temperature are demonstrated through various graphs.The novelty of this analysis is the self-similar solution of the threedimensional boundary layer flow in the presence of mixed convection,viscous dissipation and variable thermal conductivity.     

2个位势的Ablowitz-Ladik等谱方程的Complexiton解

借助双Casoratian技巧和构造双Wronski行列式元素的矩阵方法,求出2个位势的Ablowitz-Ladik等谱方程的Complexiton解和周期解,并通过将矩阵取成不同的组合类型,进而分别得到该方程具有双Casorati行列式形式的新解,即Complexiton解与类有理解的混合解、Complexiton解与Matveev解的混合解.     

Comment on: “Entanglement in three coupled oscillators” [Phys. Lett. A 384 (2020) 126134]

In this comment we analyze a method for the solution of the eigenvalue equation for three coupled harmonic oscillators proposed recently. We argue that the authors did not obtain the frequencies and coordinates of the normal modes that make the Hamiltonian operator diagonal but merely six transcendental equations for the relevant parameters that they did not attempt to solve. We derive the conditions for the existence of bound states that the authors did not appear to be able to obtain probably because of the complexity exhibited by those equations.     

“翻转+分段式”有机化学实验教学设计及实践研究

以FeCl3·6H2O催化合成乙酸乙酯为教学内容,采用“翻转+分段式”混合教学方法对整个实验过程进行了改革探索。通过教师准备学习资源,学生自主学习,课堂分段讲解,互动交流以及跟踪评价等,探讨了大学有机化学实验实施“翻转+分段式”混合教学方法的有效途径。实践结果表明:混合教学模式能够显著促进学生对实验内容的理解和掌握,明显增加学生自主操作的时间,还能有效降低实验过程中的安全隐患。     

SCR performance enhancement of NiMnTi mixed oxides catalysts by regulating assembling methods of LDHs-Based precursor

A series of NiMnTi mixed metal oxides (Ni/Mn-TiO₂, Mn/NiTi-LDO and TiO₂/NiMn-LDO, NiMnTi-LDO) were synthesized via different assembling methods and evaluated in the selective catalytic reduction of NO_x with NH₃(NH₃-SCR). As the results presented, catalysts via diverse assembling methods of LDHs templates afforded different catalytic denitrification (DeNO_x) performance, which might be related to the exposure degree of active constituents and the interaction intensity between metal components. Noticeably, compared with Ni/Mn-TiO₂, Mn/NiTi-LDO and TiO₂/NiMn-LDO catalysts, the NiMnTi-LDO catalyst deriving from one step in-situ method NiMnTi-LDH precursor template exhibited the most desirable performance at temperature window of 150–360 °C in NH₃-SCR (above 90% NO_x conversion with 95% N₂ selectivity). The specific structure and property of samples were correlated by means of a series of characterizations, where the results indicated that NiMnTi-LDO possessed the highest surface area, the strongest redox ability, the most abundant acid amount and the best dispersion.     

Recent advances on the use of active anodes in environmental electrochemistry

Active anodes, especially those consisting of metal mixed oxides (MMOs) containing Ru and/or Ir oxides, have been applied in the treatment of wastewater, especially when chloride ions are present. Their characteristics continuously drive the study of applications of these materials, be they in the degradation of different organic molecules, the preparation of new electrode materials and in the association of various processes to increase pollutant removal. Thus, this brief review aims to present some of the recent advances in the application of active anode materials in environmental electrochemistry. Focussing on the 2018–2020 period, it is possible to note many applied studies, using commercially available materials, covering a wide range of target pollutants. Still other studies aim to modify the catalyst surfaces to increase the mineralization capacity, and the use of these anodes in the production of free chlorine species to mediate indirect organic reduction is observed.     

基于比率的三种群混合扩散模型的动力学行为

讨论了一类基于比率的非自治三种群混合扩散模型,三种群间既有捕食关系又有竞争关系.我们研究了该模型的动力学行为:包括一致持久性,全局渐近稳定性,周期解,概周期解的存在唯一性.表明即使食饵种群在某些孤立的斑块中可能绝灭,也可以通过适当选取扩散率来保证系统持续生存.