Influence of Negative Pressure Gradient on Pressure Distribution and Gas-Solid Flow Pattern of Solid Feed Systems

A series of experiments on a solid feed system was performed to investigate the effect of negative pressure gradient on the gas-solid flow pattern and hydrodynamic characteristics.Based on the non-fluidized gas-solid two phase flow and particulate mechanics in the standpipe,a method for predicting the pressure of the air passing through the recycle chamber and the pressure drop through the loop seal slit in these systems is also presented.The predicted pressure profile along the negative pressure gradient from the proposed model exhibits a good agreement with the experimental data.The experimental data show that the gas flow in the standpipe is always upward in the negative pressure gradients,while the direction ofthe superficial gas velocity through the recycle chamber of the loop seal does not affect the pressure drop in standpipe.It increases with an increasing negative pressure gradient.

Multiple super-resolution imaging in the second band of gradient lattice spacing photonic crystal flat lens

Based on the triangular lattice two-dimensional photonic crystal(PC), the lattice spacing along the transverse direction to propagation is altered, and a gradient PC(GPC) flat lens is designed. The band structures and equal frequency curves of the GPC are calculated;then, the imaging mechanism and feasibility are analyzed. The imaging characteristics of the GPC flat lens are investigated. It is observed that the GPC can achieve multiple types of super-resolution imaging for the point source. This GPC lens is allowed to be applied to imaging and other fields such as filtering and sensing.

Excitation and propagation of surface plasmon polaritons on a non-structured surface with a permittivity gradient

Accompanied by the rise of plasmonic materials beyond those based on noble metals and the development of advanced materials processing techniques,it is important to understand the plasmonic behavior of materials with large-scale inhomogeneity(such as gradient permittivity materials)because they cannot be modeled simply as scatterers.In this paper,we theoretically analyze the excitation and propagation of surface plasmon polaritons(SPPs)on a planar interface between a homogeneous dielectric and a material with a gradient of negative permittivity.We demonstrate the following:(i)free-space propagating waves and surface waves can be coupled by a gradient negative-permittivity material and(ii)the coupling can be enhanced if the material permittivity variation is suitably designed.This theory is then verified by numerical simulations.A direct application of this theory,‘rainbow trapping’,is also proposed,considering a realistic design based on doped indium antimonide.This theory may lead to various applications,such as ultracompact spectroscopy and dynamically controllable generation of SPPs.

An improved method for evaluating the rotational speed stability of a hydro-viscous clutch in mixed lubrication

Rotational speed stability is an important evaluation indicator of the performance of a hydro-viscous clutch(HVC).To improve the rotational speed stability of HVCs in mixed lubrication and the running condition of the friction pairs,the speed stability of an HVC in mixed lubrication was studied.To this end,the friction coefficients of both copper-based and paper-based friction pairs were experimentally tested using an MM1000-III wet friction machine.Theoretically,a torsional vibration model of the system is presented.The phase plane analysis method is applied to evaluate the stability of the torsional vibration model,where a critical negative gradient(CNG)is defined.The results show that the friction coefficient in mixed lubrication is an important parameter for the stability of the rotational speed.The system will be unstable when the negative gradient of the friction coefficient-slip speed is larger than the CNG.According to the definition of the CNG,suggestions regarding choice of friction pairs are made to improve the rotational speed stability of an HVC in mixed lubrication.

An improved trust region method for unconstrained optimization

In this paper,we propose an improved trust region method for solving unconstrained optimization problems.Different with traditional trust region methods,our algorithm does not resolve the subproblem within the trust region centered at the current iteration point,but within an improved one centered at some point located in the direction of the negative gradient,while the current iteration point is on the boundary set.We prove the global convergence properties of the new improved trust region algorithm and give the computational results which demonstrate the effectiveness of our algorithm.