Adaptive stochastic resonance method for weak signal detection based on particle swarm optimization

In order to solve the parameter adjustment problems of adaptive stochastic resonance system in the areas of weak signal detection,this article presents a new method to enhance the detection efficiency and availability in the system of two-dimensional Duffing based on particle swarm optimization.First,the influence of different parameters on the detection performance is analyzed respectively.The correlation between parameter adjustment and stochastic resonance effect is also discussed and converted to the problem of multi-parameter optimization.Second,the experiments including typical system and sea clutter data are conducted to verify the effect of the proposed method.Results show that the proposed method is highly effective to detect weak signal from chaotic background,and enhance the output SNR greatly.     

Weak boundary layers on vulcanized styrene–butadiene rubber treated with sulfuric acid

A synthetic vulcanized styrene-butadiene rubber (R2) was used in this study. The presence of paraffin wax and zinc stearate in the rubber composition prevented the adhesion of R2 rubber to solvent-based polyester-urethane adhesive. To increase the adhesion properties of R2 rubber, a surface treatment with sulfuric acid (cyclization) was applied, and the length of the immersion in sulfuric acid and the time between the immersion time and the neutralization were varied. The treated R2 rubber surfaces were characterized using ATR-IR spectroscopy, contact angle measurements (water, ethanediol), and scanning electron microscopy (SEM). The mechanical properties of the treated rubber were obtained from stress-strain experiments. The joint strength was obtained from the T-peel test on treated R2 rubber/polyurethane adhesive joints. Due to the penetration of the sulfuric acid into the R2 rubber bulk, the mechanical properties decreased. The treatment with sulfuric acid produced several chemical modifications on the rubber surface: sulfonation of the butadiene and the creation of C C and C O bonds. Furthermore, the surface treatment of the R2 rubber with sulfuric acid removes paraffin wax from the rubber surface, which had a beneficial effect on adhesion to the polyurethane adhesive. To remove the wax layer, the surface was wiped with petroleum ether solvent after treating the R2 rubber with sulfuric acid. However, in some experiments a progressive migration of wax from the R2 rubber bulk to the surface with time happened. The migration of wax was prevented by increasing the immersion time in H₂SO₄ by more than 5 min.     

Weak boundary layers on wood surfaces

Adoption of the weak boundary layer (WBL) concept in wood adhesion science and a general extension of the concept are suggested. A distinction is made between a chemical weak boundary layer (CWBL) and a mechanical weak boundary layer (MWBL). Definitions of both CWBL and MWBL are proposed. On wood, a CWBL is caused mainly by extractives migrating to the wood surface after machining, whereas an MWBL is caused mainly by the machining operation itself or by degradation of the fibres at the surface, in practice mainly by natural (UV) light irradiation. Sawn endgrain and planed side-grain surfaces of softwoods have been studied by scanning electron microscopy [SEM and environmental SEM (ESEM)]. Both sawn and planed wood surfaces are deformed to a depth of 0.1-0.2 mm to such an extent that one cannot expect the same strength at the surface as in the intact wood material. The crushed and damaged surface can be expected to contain failure initiation sites when the glueline, especially in an end-grain joint, or a coating is exposed to stresses. Furthermore, this crushed and damaged surface can be expected to be a barrier for adhesives and coatings to penetrate into the material and anchor to intact wood material. A comparison between microtomed and sawn end-grain surfaces has shown that the damaged fibres seem, to some extent, to improve the glue joint performance, using a conventional glue. Reasons for this are discussed.