Analysis of vibration attenuation characteristics of large thickness carbon fiber composite laminates

The vibration attenuation and damping characteristics of carbon fiber reinforced composite laminates with different thicknesses were investigated by hammering experiments under free boundary constraints in different directions. The dynamic signal testing and analysis system is applied to collect and analyze the vibration signals of the composite specimens, and combine the self-spectrum analysis and logarithmic decay method to identify the fundamental frequencies of different specimens and calculate the damping ratios of different directions of the specimens. The results showed that the overall stiffness of the specimen increased with the increase of the specimen thickness, and when the thickness of the sample increases from 24mm to 32mm, the fundamental frequency increases by 35.1%, the vibration showed the same vibration attenuation and energy dissipation characteristics in the 0° and 90° directions of the specimen, compared with the specimen in the 45° direction, which was less likely to be excited and had poorer vibration attenuation ability, while the upper and lower surfaces of the same specimen showed slightly different attenuation characteristics to the vibration, the maximum difference of damping capacity between top and bottom surfaces of CFRP plates is about 70%

The protective effect of PL 1-3 on D-galactose-induced aging mice

The aging population has become an issue that cannot be ignored, and research on aging is receiving increasing attention. PL 1-3 possesses diverse pharmacological properties including anti-oxidative stress, inhibits inflammatory responses and anti-apoptosis. This study showed that PL 1-3 could protect mice, especially the brain, against the aging caused by D-galactose (D-gal). D-gal could cause oxidative stress, inflammation, apoptosis and tissue pathological injury and so on in aging mice. The treatment of PL 1-3 could increase the anti-oxidative stress ability in the serum, liver, kidney and brain of aging mice, via increasing the total antioxidant capacity and the levels of anti-oxidative defense enzymes (superoxide dismutase, glutathione peroxidase, and catalase), and reducing the end product of lipid peroxidation (malondialdehyde). In the brain, in addition to the enhanced anti-oxidative stress via upregulating the level of the nuclear factor erythroid 2-related factor 2 and heme oxygenase 1, PL 1-3 could improve the dysfunction of the cholinergic system via reducing the active of acetylcholinesterase so as to increase the level of acetylcholine, increase the anti-inflammatory and anti-apoptosis activities via downregulating the expressions of pro-inflammatory cytokines (interleukin-6 and tumor necrosis factor-α) and pro-apoptosis proteins (Bcl-2 associated X protein and Caspase-3) in the D-gal-induced aging mice, to enhance the anti-aging ability via upregulating the expression of sirtuin 1 and downregulating the expressions of p53, p21, and p16. Besides, PL 1-3 could reverse the liver, kidney and spleen damages induced by D-gal in aging mice. These results suggested that PL 1-3 may be developed as an anti-aging drug for the prevention and intervention of age-related diseases

DOA Estimation in Car for Abnormal Sound Localisation

Spurious noise in car cabinet can be not only annoying bust also indicative of some potential faults. A small square microphone array with 4 sensors was adopted in this paper to localize the sound source in car for fault diagnosis. A new voice activity detection (VAD) algorithm was proposed for the typical discontinuous short-time noise in car due to some fault and applied to direction of arrival (DOA) estimation as a pre-processing stage. Four different time delay estimation methods were compared based on the measurements from a typical passenger. Experimental results illustrate that the VAD algorithm is crucial to achieve robust fault localization performance and the generalized cross-correlation method with phase transform weighting function is an appropriate fault localizer in car

A Novel Method for Deposition of Multi-Walled Carbon Nanotubes onto Poly(p-Phenylene Terephthalamide) Fibers to Enhance Interfacial Adhesion with Rubber Matrix

In order to enhance the interfacial adhesion of poly(p-phenylene terephthalamide) (PPTA) fibers to the rubber composites, a novel method to deposit multi-walled carbon nanotubes (MWCNTs) onto the surface of PPTA fibers has been proposed in this study. This chemical modification was performed through the introduction of epoxy groups by Friedel⁻Crafts alkylation on the PPTA fibers, the carboxylation of MWCNTs, and the ring-opening reaction between the epoxy groups and the carboxyl groups. The morphologies, chemical structures, and compositions of the surface of PPTA fibers were characterized by scanning electron microscope, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The results showed that MWCNTs were uniformly deposited onto the surface of PPTA fibers with the covalent bonds. The measurement of contact angles of the fibers with polar solvent and non-polar solvent indicated that the surface energy of deposited fibers significantly increased by 41.9% compared with the untreated fibers. An electronic tensile tester of single-filament and a universal testing machine were utilized to measure the strength change of the fibers after modification and the interfacial adhesion between the fibers and the rubber matrix, respectively. The results showed that the tensile strength had not been obviously reduced, and the pull-out force and peeling strength of the fibers to the rubber increased by 46.3% and 56.5%, respectively

Experiment on Chloride Ion Content of Concrete Structure in Coastal Salt-fog Area

This paper chose the south-east coastal salt-fog area Shantou to carry out the experiment study on chloride ion content of concrete structure, through the chloride ion content field test on reinforced concrete structure in Shantou, respectively for the slat-fog atmosphere zone and the splash zone in marine environment, discuss the corrosion by chloride ion of long-time existing concrete structure.And then measure the chloride ion content of concrete cover in different depth, and determine the chloride ion diffusion model in different conditions concrete through comparative analysis.The result of study, can be used in directing the selection of design scheme for building in planning, and also it will help predict the corrosion time of reinforcement inside the concrete on different positions for existing structure

Experiment on Chloride Ion Content of Concrete Structure in Coastal Salt-fog Area

This paper chose the south-east coastal salt-fog area Shantou to carry out the experiment study on chloride ion content of concrete structure, through the chloride ion content field test on reinforced concrete structure in Shantou, respectively for the slat-fog atmosphere zone and the splash zone in marine environment, discuss the corrosion by chloride ion of long-time existing concrete structure.And then measure the chloride ion content of concrete cover in different depth, and determine the chloride ion diffusion model in different conditions concrete through comparative analysis.The result of study, can be used in directing the selection of design scheme for building in planning, and also it will help predict the corrosion time of reinforcement inside the concrete on different positions for existing structure

Experiment on Chloride Ion Content of Concrete Structure in Coastal Salt-fog Area

This paper chose the south-east coastal salt-fog area Shantou to carry out the experiment study on chloride ion content of concrete structure, through the chloride ion content field test on reinforced concrete structure in Shantou, respectively for the slat-fog atmosphere zone and the splash zone in marine environment, discuss the corrosion by chloride ion of long-time existing concrete structure.And then measure the chloride ion content of concrete cover in different depth, and determine the chloride ion diffusion model in different conditions concrete through comparative analysis.The result of study, can be used in directing the selection of design scheme for building in planning, and also it will help predict the corrosion time of reinforcement inside the concrete on different positions for existing structure

Newly Generated Ca-Feldspar during Sintering Processes Enhances the Mechanical Strength of Coal Gangue-Based Insulation Bricks

Coal gangue is a solid waste with low carbon content discharged during the course of the coal mining process. The resource utilization of coal gangue could solve environmental problems caused by its excessive production, such as soil contamination and land occupation. This study proposed to produce high-strength thermal insulation bricks using coal gangue as the primary material and three other mineral powders as auxiliary materials, including K-feldspar, CaCO3 and fly ash. A systematic analysis was conducted to explore the optimum raw material addition ratio and optimum sintering temperature; then, the intrinsic structure of thermal insulation bricks and their sintering formation mechanisms were revealed. The results showed that the optimal ratios of coal gangue, K-feldspar, CaCO3 and fly ash were 65 wt%, 15 wt%, 10 wt% and 10 wt%, respectively; the compressive strength of the thermal insulation brick produced under this ratio was 22.5 MPa; thermal conductivity was 0.39 W m−1 k−1. During sintering processes, mineral powders sufficiently fused to form a skeleton, and the CO2 derived from CaCO3 formed pores. The optimum sintering temperature was 1150 °C, because at this temperature, K-feldspar had the best effect in promoting the conversion of CaCO3 to Ca-feldspar. The high level of the relative crystallinity of Ca-feldspar (about 76.0%) helped raise the Si–O network’s polymerization degree (NBO/T = 1.24), finally raising the compressive strength of thermal insulation bricks. The innovative method of using coal gangue to make thermal insulation bricks not only solved the environmental pollution caused by coal gangue but also provided excellent construction materials with high practical application value