Interlaminar Shear Characteristics of Typical Polyurethane Mixture Pavement

Polyurethane (PU) can be used as a road material binder, and its mechanical properties, durability, temperature stability, and other road performance metrics are good. However, the interlayer bonding between PU mixtures and asphalt mixtures is poor. The influence of the pavement structure, interlayer treatment scheme, load, and environmental factors on the interlayer shear characteristics of PU mixture composite pavement is analysed. Further, dynamic modulus, Hamburg rutting, accelerated loading, and inclined shear tests were conducted, and the typical PU mixture pavement shear stress was calculated. The interlaminar shear stress of double layer PU mixture pavement, polyurethane–asphalt composite pavement, and typical asphalt pavement were calculated. The results showed that the PU mixture has a low rutting deformation rate, stable mechanical properties, and strong resistance to the coupled action of temperature, water, and loading. The double-layer PU mixture structure has good water-temperature stability and fatigue resistance; however, freeze–thaw and accelerated loading cause great damage to the double-layer PU mixture structure. The residual shear strength ratio after freeze–thaw cycles and accelerated loading is only 50.3% and 35.6%, respectively, while the influence on the double-layer asphalt mixture structure is less. The theoretical calculation results of different pavement structures show that when the temperature increases from 10 °C to 50 °C, the interlaminar shear stress of polyurethane–asphalt composite pavement increases by about 20%. Additionally, the shear stress of pavement PU mixture pavement and typical asphalt pavement is mainly affected by load, and the temperature changes have an obvious effect on the interlayer shear stress of polyurethane–asphalt composite pavement. The calculated maximum shear stress of the three pavement structures with different working conditions is less than the interlaminar shear strength measured by the inclined shear test, indicating that the interlaminar treatment scheme of composite specimens can meet the shear resistance requirements of the three typical pavement structure types

Laser-induced ultrasonic measurements for the detection and reconstruction of surface defects

Laser-induced ultrasonic measurement is a non-contact non-destructive technology that can be employed for the testing and assessment of surface defects. In order to improve the correct identification of defects, the full matrix capture (FMC) and total focusing method (TFM) are applied on the imaging process. FMC data includes A-scans resulting from the combination of all measurement axes defined by the sequential generation and detection of utilized laser beams in the system. In this paper, an aluminium block with four holes whose diameters range from 1 mm to 2.5 mm is assessed through B-scans, the synthetic aperture focusing technique (SAFT) and FMC/TFM. The results demonstrate that the FMC/TFM technology can significantly improve the imaging quality and signal-to-noise ratio (SNR). In addition, this method has higher lateral resolution and larger imaging range compared with traditional B-scans

Field characterization of steady state focused transducers using hydrophones based on Fresnel approximation

This paper is intended to estimate the spatial averaging effects of the hydrophone in field characterization of focused transducers. The analytical model derived was based on Fresnel approximation and enabled modifications of the results for both on-axis and off-axis measurement arrangements. The axial and lateral field distributions in the focal plane measured by the hydrophone were derived for both non-attenuating and attenuating fluids in the model. The spatial averaging effects result in underestimating the absolute acoustic pressure amplitudes, and overestimating the cross-sectional size of the beam directivity pattern in the focal plane. The validity of the Rayleigh integral and the Fresnel approximation for curved transducers were discussed. The results indicate that, for √k(ah+b)/2≫π (where k is the circular wave number, ah is the chord from the center of curved surface to the boundary and b is the effective radius of the hydrophone), the Fresnel approximation remains valid for all locations of the hydrophone in the focused field. Particularly, in the focal plane, the spatial averaging effects of the hydrophone on the directivity pattern of the acoustic beam can be neglected for k(b2+4ab)/2lf≪1 (where a and lf are the effective radius and focal distance of the focused transducer)

Structures, Electronic Properties and Carrier Transport Mechanisms of Si Nano-Crystalline Embedded in the Amorphous SiC Films with Various Si/C Ratios

Recent investigations of fundamental electronic properties (especially the carrier transport mechanisms) of Si nanocrystal embedded in the amorphous SiC films are highly desired in order to further develop their applications in nano-electronic and optoelectronic devices. Here, Boron-doped Si nanocrystals embedded in the amorphous SiC films were prepared by thermal annealing of Boron-doped amorphous Si-rich SiC films with various Si/C ratios. Carrier transport properties in combination with microstructural characteristics were investigated via temperature dependence Hall effect measurements. It should be pointed out that Hall mobilities, carrier concentrations as well as conductivities in films were increased with Si/C ratio, which could be reached to the maximum of 7.2 cm2/V∙s, 4.6 × 1019 cm−3 and 87.5 S∙cm−1, respectively. Notably, different kinds of carrier transport behaviors, such as Mott variable-range hopping, multiple phonon hopping, percolation hopping and thermally activation conduction that play an important role in the transport process, were identified within different temperature ranges (10 K~400 K) in the films of different Si/C ratio. The changes from Mott variable-range hopping process to thermally activation conduction process with temperature were observed and discussed in detail

Effects of Dietary Fucoidan Supplementation on Serum Biochemical Parameters, Small Intestinal Barrier Function, and Cecal Microbiota of Weaned Goat Kids

The purpose of this study was to evaluate the effects of fucoidan supplementation on serum biochemical parameters, small intestinal barrier function, and cecal microbiota of weaned goat kids. A total of 60 2-month-old weaned castrated male goat kids (Chuanzhong black goat) were used in this 30-day experiment. The goat kids were randomly divided into four groups: a control group (CON) fed the basal diet, and three other groups supplemented with 0.1%, 0.3%, and 0.5% fucoidan in the basal diet (denoted as F1, F2, and F3 groups, respectively). The results indicated that dietary fucoidan supplementation decreased (p p p p p p 2O2) in the duodenum. Dietary fucoidan increased (p p p p Bacteroidetes while decreasing (p Firmicutes. At the genus level, dietary 0.3% and 0.5% fucoidan increased (p Unspecified_Ruminococcaceae, Unspecified_Bacteroidale, Unspecified_Clostridiales, and Akkermansia. In conclusion, dietary fucoidan supplementation had positive effects on intestinal permeability, antioxidant capacity, immunity function, tight junctions, and the cecal microflora balance in weaned goat kids