Controllable and tunable plasma photonic crystals through a combination of photonic crystal and dielectric barrier discharge patterns

We report five types of patterns with square symmetry,including three novel types obtained by inserting a specially designed grid photonic crystal(PC)into a dielectric barrier discharge system.They are studied using an intensified charge-coupled device camera and photomultiplier tubes.The three novel types of patterns are a square pattern with one structure,a square superlattice pattern with four sublattices and a(1/4)K_(grid)(K_(grid)is the basic wave vector of the grid),and another square pattern with a complex inversion discharge sequence.From the application viewpoint,the five types of patterns can be used as plasma photonic crystals(PPCs).Their band diagrams under a transverse-magnetic wave simulated by the finite element method show that there are a large number of band gaps.Compared with the original PC with only a unidirectional band gap,the five types of PPCs have tunable and omnidirectional band gaps,which is very important in controlling the propagation of electromagnetic waves in the mm-wave region.The experimental results enrich the pattern types in the dielectric barrier discharge system and provide a method for obtaining PPCs with symmetry controllability and bandgap tunability.

Surface-enhanced fluorescence and application study based on Ag-wheat leaves

Wheat leaves with natural microstructures as substrates were covered by the silver nanoislands by magnetron to prepare a low-cost, environment-friendly and mass production surface-enhanced fluorescence(SEF) substrate(Ag-WL substrate). The best SEF substrate was selected by repeatly certifying the fluorescence intensity of 10^(-5)M Rhodamine B(RB) and 10^(-5)M Rhodamine 6G(R6G) aqueous solutions. The abundant semi-spherical protrusions and flake-like structures on the surface of the Ag-WL substrate produce high-density hot spots, which provides a new and simple idea for the preparation of biomimetic materials. The results of 3D finite-different time-domain(FDTD) simulation show that the nanoisland gap of semi-spherical protrusions and flake-like structures has produced rich hotspots. By adjusting the time of magnetron sputtering, the enhancement factor(EF) was as high as 839 times, relative standard deviation(RSD) reached as low as 10.7%, and the substrate was very stable and repeatable, which shows that Ag-WL substrate is trustworthy.Moreover, semi-spherical protrusions provide stronger surface-enhanced Raman scattering(SERS) effects compared to flake-like structure. What is more surprising is that the detection limit of the substrate for toxic substance crystal violet(CV) is as low as 10^(-10)M.

An Improved Binary Wolf Pack Algorithm Based on Adaptive Step Length and Improved Update Strategy for 0-1 Knapsack Problems

Binary wolf pack algorithm (BWPA) is a kind of intelligence algorithm which can solve combination optimization problems in discrete spaces.Based on BWPA, an improved binary wolf pack algorithm (AIBWPA) can be proposed by adopting adaptive step length and improved update strategy of wolf pack. AIBWPA is applied to 10 classic 0-1 knapsack problems and compared with BWPA, DPSO, which proves that AIBWPA has higher optimization accuracy and better computational robustness. AIBWPA makes the parameters simple, protects the population diversity and enhances the global convergence.

Hydrophobic epoxy resin coating with ionic liquid conversion pretreatment on magnesium alloy for promoting corrosion resistance

A hydrophobic epoxy resin coating with an environmental-friendly deep eutectic solvent(DES)-based conversion pretreatment was proposed to enhance the corrosion resistance of magnesium alloys.The hydrophobic epoxy resin coatings on the AZ31B magnesium alloy with and without the DES-based conversion pretreatment were thoroughly compared.It is found that the DES-based conversion film on the AZ31B magnesium alloy is mainly composed of MgH2,MgO and MgCO3.Furthermore,the conversion film possesses porous structure,which provides more anchor points for the following epoxy resin coating.However,without the DES-conversion pretreatment,the epoxy resin is difficult to be attached on the substrate during the dip-coating process.The double layered hybrid coating system promotes the corrosion resistance of the magnesium alloys significantly,which can be ascribed to the unique architecture and component including the hydrophobicity of the surface layer,the dense and interlocked epoxy resin,and the corrosion resistant DES-based conversion pretreatment.