On the fluorescence enhancement mechanism of Er^(3+) in germanate glass containing silver particles

The spectral properties of trivalent erbium ions（Er^3＋） are systematically studied in a melt-quenched germanate glass（60 GeO2-20PbO-10BaO-10K2O-0.1Ag2O） containing silver（Ag） particles.Thermal treatment of the material leads to the precipitation of Ag particles as observed by transmission electron microscopy and confirmed by absorption spectrum for the obvious surface plasmon resonance peak of Ag particles.The fluorescence from Er^3＋ in the 10-min-annealed sample with Ag particles is found to be 4.2 times enhanced compared with the unannealed sample excited by 488-nm Ar＋ laser.A comparison is made between a spectral study performed on the unannealed Er^3＋-doped sample and the one annealed for 20 min.The data of absorption cross section and Judd-Ofelt intensity parameters show the agreement between the two samples no matter whether there are Ag particles,indicating that the introduction of Ag particles by post-heat treatment has no effect on the crystal field environment of Er^3＋ ions.The fluorescence enhancement is attributed to the surface plasmon oscillations of Ag particles in germanate glass.

Enhancement of Heat-Resistance of Carbonyl Iron Particles by Coating with Silica and Consequent Changes in Electromagnetic Properties

Silica-coated carbonyl iron particles （CIPs） are fabricated with the Stober method to improve their heat-resistance and wave-aSsorption properties. The morphology, heat-resistance, electromagnetic properties and microwave absorption of raw-CIPs and silica-coated CIPs are investigated using a scanning electron microscope, an energy dispersive spectrometer, a thermal-gravimetric analyzer, and a network analyzer. The results show that the heat-resistance of silica-coated CIPs is better than that of raw CIFs. The reflection losses exceeding -lOdB of silica-coated CIPs are obtained in the frequency range 9.5-12.4 GHz for the absorber thickness of 2.3 mm, and the same reflection losses of uncoated CIPs reach the data in the lower frequency range for the same thickness. The enhanced microwave absorption of silica-coated CIPs can be ascribed to the combination of proper electromagnetic impedance match and the decrease of dielectric permittivity.

Improved particle swarm optimization based on particles' explorative capability enhancement

Accelerating the convergence speed and avoiding the local optimal solution are two main goals of particle swarm optimization（PSO）. The very basic PSO model and some variants of PSO do not consider the enhancement of the explorative capability of each particle. Thus these methods have a slow convergence speed and may trap into a local optimal solution. To enhance the explorative capability of particles, a scheme called explorative capability enhancement in PSO（ECE-PSO） is proposed by introducing some virtual particles in random directions with random amplitude. The linearly decreasing method related to the maximum iteration and the nonlinearly decreasing method related to the fitness value of the globally best particle are employed to produce virtual particles. The above two methods are thoroughly compared with four representative advanced PSO variants on eight unimodal and multimodal benchmark problems. Experimental results indicate that the convergence speed and solution quality of ECE-PSO outperform the state-of-the-art PSO variants.

Application of Nanogoid Probe Coupled with Silver Enhancement in Rapid cTnI Colorimetric Immunoassay

A rapid, inexpensive, reliable, and flexible quantitative immunoassay for cardiac troponin I （cTnI） based on the concepts of one-step dual monoclonal antibody “sandwich” principle. The low density protein array, the nanogold probe, and the silver enhancement on the gold particle were provided. The whole detection procedure of the assay could be fulfilled within 40 min with the pretreated colloidal gold-labeled detection antibody and supporting substrate. The assay showed good specific response to cTnI with very low cross-reactivity ratio to the skeletal isoforms of troponin I （sTnI）, cardiac troponin T （cTnT）, and myoglobin. 588 serum samples were assayed simultaneously by enzyme-linked immuno sorbent assay （ELISA） and this colloidal gold method to test the validity of the method and the data were analyzed using the statistical package SPSS version 11.0 （SPSS Inc.）. There was no significant difference between these two assays （P=0.66〉0.05）. The agreement between this method （〉 or 〈0.3 ng/mL） and ELISA was 86%.

Study of the morphology and properties of diamond joints brazed with carbide-reinforced Cu-Sn-Ti filler metal

Cu-Sn-Ti brazing filler is a new type of copper-based brazing filler for brazing diamond tools currently used in industry,but it suffers from poor wear resistance,high brazing temperature and low bond strength.This paper provides a way to improve the strength of dia-mond-brazed joints by adding zirconium carbide and tungsten carbide reinforcing phase particles to the Cu-Sn-Ti alloy,respectively.Dia-mond particles were attached to Q460 steel using Cu-Sn-Ti composite filler with the addition of the reinforcing phase,and experimental in-struments such as scanning electron microscope,X-ray diffractometer and energy spectrometer were used to investigate the brazed joint per-formance of the composite brazing material for brazing diamond.The results show that the addition of enhanced phase particles resulted in a metallurgical reaction at the joint of the composite brazed diamond,achieving a higher strength joint with no obvious cracks at the interface,while the addition of 15 wt.%WC resulted in excellent wear resistance and the highest hardness at the joint interface.

Strengthening mechanism of B_4C@APC/Al matrix composites reinforced with bimodal-sized particles prepared by hydrothermal carbonized deposition on chips

A B_(4)C@amorphous carbon(APC)/Al matrix composite was fabricated by using hydrothermal carbonized deposition on chips(HTCDC)process and solid-state synthesis process.The microstructure and mechanical properties of the B_(4)C@APC/Al matrix composite were investigated.After HTCDC process,nano-B_(4)C particles(50 nm)and micron-sized B_(4)C@APC core-shell spheres with a diameter of 2μm were found in the composites.The microhardness of the micron-sized B_(4)C@APC spheres is 1.66 GPa,which is greater than that of theα-Al matrix(1.06 GPa).Dislocation accumulation is observed around the micron-sized B_(4)C@APC spheres,indicating that the micron-sized B_(4)C@APC spheres have a strengthening effect on theα-Al matrix.Due to the formation of micron-sized B_(4)C@APC spheres,the reinforcement of nano-B_(4)C particles into the composites is transformed from single-sized particle enhancement to bimodal-sized particle enhancement.The strengthening mechanism for B_(4)C@APC/Al matrix composites with bimodalsized particles of nano-B_(4)C and micron-sized B_(4)C@APC spheres were analyzed,which includes thermal mismatch strengthening generated by the mismatch of coefficient of thermal expansion(CTE)between micron-sized B_(4)C@APC core-shell spheres andα-Al matrix,Orowan strengthening produced by nano-B_(4)C particles,Hall-Petch strengthening and load transfer strengthening produced by the bimodal-sized enhancement from nano and microspheres.A relationship model between the yield strength(YS)increment and the conversion rate(x)of micron-sized B_(4)C@APC core-shell spheres was estimated.