A Survey of the Hard X-Ray Characteristics of Seismically Active and Quiet White-Light Flares

Various mechanisms have been proposed to explain how seismic waves can be generated during a solar flare, several of which include a major role for accelerated electrons. To address this question further, we have selected two samples of white-light flares (WLFs): one that has associated sunquakes, and one that does not. We focus particularly on the spatial characteristics of the hard X-ray (HXR) and WL emission, and the HXR spectral characteristics associated with the flares in both samples, including spectral hardness, HXR source size, and total injected electron power. Coupling the determined rate of energy deposition with the area over which the energy is being deposited suggests that in general the acoustically active flares are associated with a larger and more impulsive deposition of electron energy. However, this does not always correspond to a higher WL contrast.     

Enhancing the interface friction between glass fiber-reinforced polymer sheets and sandy soils through sand coating

ABSTRACT

Soil-pile interface friction is an important geotechnical engineering factor to be considered in achieving a safe and cost-effective design. Conventional materials such as concrete, steel, and wood exhibit serious long-term soil substructure problems, particularly with regard to durability, deterioration, and corrosion. Fiber-reinforced polymer (FRP) composites are potential alternatives for addressing these long-term problems. This paper describes the results of an experimental study of the interface friction between sandy soil and glass FRP (GFRP) sheets coated with different ratios of sand per unit of surface area. A direct shear test was used to study 18 different groups of GFRP specimens. The test parameters were the amount of silica sand coating and normal stresses in the direct shear tests. The GFRP specimens were sheared against three types of soil: sand, silty sand, and sandy lean-clay, of which the first two were used in both dense and loose states. The experimental results showed that coating the GFRP sheets with silica sand was effective in enhancing the interface friction with sandy soils under different normal stresses. A pile implication analysis was also performed to compare the effect of sand coated GFRPs on the load capacity of friction piles with different length to diameter ratios.