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The utilization of magnetic nanofluids as the base carrier fluid of magnetorheological fluids represents an effective approach to enhance the magnetorheological effect. However, achieving highly stable nano-composite magnetorheological fluids remains a significant challenge, encompassing both the synthesis of magnetic nanofluids and the prevention of composite particle agglomeration. In this study, Fe3O4 silicone oil-based magnetic nanofluids were prepared using silane coupling agent KH550 as a dispersant, followed by a novel process of co-coating dispersants to obtain nano-composite magnetorheological fluids. The surface morphology, physical phase composition and magnetic properties were characterized and analyzed using XRD, FI-IR, TEM, FE-SEM and VSM. The sedimentation stability and redispersibility of the novel nano-composite magnetorheological fluids were investigated. The results show that surface modification of micron-sized particles significantly enhances the stability and redispersibility of the nano-composite magnetorheological fluids, with optimal sedimentation stability and redispersibility observed at nanoparticle volume fraction of 8%. Furthermore, the novel nano-composite magnetorheological fluids demonstrate superior temperature resistance, remaining stable within the temperature range form -40 °C to 120 °C over extended durations. Rheological properties of novel nano-composite magnetorheological fluid were also investigated demonstrating higher off-state viscosity and magnetorheological effect in comparison to conventional magnetorheological fluids. Moreover, both static and dynamic yield stresses increase with nanoparticle concentration and magnetic field strength. [ABSTRACT FROM AUTHOR]

Corn oil as a nanofluid base fluid has the problem of easy oxidation, and the addition of tertiary butyl-hydroquinone is expected to improve the antioxidant property of corn oil. In this paper, a new environmentally friendly nanofluid was prepared by using corn oil as a base fluid, A12O3 as nanoparticles, and tertiary butylhydroquinone as an antioxidant to study its settlement stability and antioxidant properties. The content of oxidation products and viscosity of the nanofluids at different times were investigated from the perspectives of particle size, particle mass fraction, antioxidant type, and antioxidant addition. The results showed that the nanofluids produced without surfactant, 100 mL of corn oil, Al2O3 nanoparticles with a particle size of 20 nm and a particle mass fraction of 1.1083% had the best sedimentation stability. The nanofluid with 0.7% of tertiary butylhydroquinone added had the optimum antioxidant properties. There are two phenolic hydroxyl groups in the molecule of tertiary butylhydroquinone, and each of the two phenolic hydroxyl groups provides one hydrogen ion, which forms stable quinone compounds in corn oil, making the oxidation rate of the corn oil slower. When the content of tertiary butylhydroquinone was added at less than 0.4%, the content of tertiary butylhydroquinone was not enough to effectively retard the oxidation reaction of the oil. When the addition of tertiary butylhydroquinone exceeded 0.7%, the antioxidant property of the nanofluid could only be improved slightly, and the oxidation induction time increased slowly, but on the contrary, the viscosity of the nanofluid would be increased greatly. The nanofluid prepared in this paper has the characteristics of environmental friendly and good antioxidant performance, which can effectively slow down the generation of oxidised substances. This study contributes to the further development of antioxidant research of environmentally friendly nanofluids. [ABSTRACT FROM AUTHOR]

The utilization of magnetic nanofluids as the base carrier liquid proves to be an effective strategy for enhancing the stability of magnetorheological fluids. However, the preparation method for bidispersed magnetorheological fluids still deserves further investigation. In this study, Fe3O4 nanoparticles were synthesized through chemical co-precipitation, and aviation hydraulic oil-based magnetic nanofluids were prepared using myristic acid as a surfactant. Micron-sized particles, modified with the same surfactant, were dispersed into the magnetic nanofluids, resulting in a novel bidisperse magnetorheological fluid (C-MRFF). The coated particles underwent physical phase analysis and magnetic property testing through an x-ray diffractometer, Fourier infrared spectrometer, transmission electron microscope, scanning electron microscope, and vibrating sample magnetometer. Due to the addition of nanoparticles, C-MRFFs exhibited superior stability to micron-sized particle-based magnetorheological fluids. They demonstrated the best sedimentation stability and redispersibility at a 9% mass fraction of nanoparticles. Thanks to the protection of the micron-sized particle surface coating, C-MRFFs displayed superior sedimentation stability to traditional bidisperse magnetorheological fluids over a wide temperature range. The magnetorheological properties of C-MRFFs were studied. The results indicated that the yield stress of C-MRFFs increased with increasing magnetic field strength or decreasing temperature. The increase in the mass fraction of nanoparticles was beneficial to the increase in yield stress until severe settling of C-MRFFs occurred. In comparison to micron-sized particle-based magnetorheological fluids, C-MRFFs exhibited higher yield stresses. Although the yield stress of C-MRFFs was slightly lower than that of traditional bidisperse magnetorheological fluids due to the surface coating of larger particles, they exhibited stronger shear resistance over a wide temperature range. [ABSTRACT FROM AUTHOR]

To solve the problem of the error of frequency measurement algorithm with time-varying frequency in mine power supply system, an improved software zero-crossing algorithm is proposed.The relationship among the phase angle, the time and the frequency of the voltage of the system is established.The relation formula between the real-time frequency and the period of zero-crossing point is derived when rate of frequency variation is not zero according to the relationship between two adjacent with the direction of the zero-crossing phase difference of 2π.The exact calculation formula of the period is obtained by using the Newton three interpolation polynomial, the Newton iteration method and the Qin Jiushao algorithm.Hence, the frequency and rate of frequency variation can be obtained.A variety of situations , including signals without harmonics, signals with harmonics and random noise, as well as the frequency rapid decline process in system failure, are simulated using MATLAB, The simulation results show that the algorithm of this paper can accurately measure the real-time frequency of the system and rate of frequency variation in above situations, and this method is superior to conventional zero-crossing algorithm in measurement accuracy, instantaneity and computation.This algorithm is suitable for application of protection, control and monitoring devices and automation equipment in mine intelligent power supply system.

In order to research the sedimentation stability of water-based magnetic fluid, the sedimentation stability of water-based Ni0.5Zn0.5 Fe2O4 magnetic fluid at different pH values was studied, and the experimental phenomena were analyzed. The results show that when the mass fraction of OA (oleic acid) is 4%, the mass fraction of SDS (sodium dodecyl sulfate) is 3%, and the mass fraction of Ni0.5Zn0.5 Fe2O4 is 2. 5%, the magnetic fluid as-prepared has the best stability. When pH value is <7, the sedimentation stability of magnetic fluid decreases with the decrease of pH value, but the viscosity increases with the decrease of pH value. When pH is >7, the sedimentation stability of MHD decreases with the increase of pH value. The higher the temperature is, the better the dispersion is. The pH value has a certain influence on the thermal dispersion of the magnetic fluid. The pH value has an important influence on the magnetic field settling stability and magnetic viscosity of magnetic fluid. Under the action of constant or increasing magnetic fields, the settling coefficient and viscosity of magnetic fluid change with the change of magnetic field and pH value. [ABSTRACT FROM AUTHOR]

The unsaturated hydraulic characteristics of waste soil are an essential basis for predicting and evaluating leachate migration and distribution in landfills. The saturated water content and permeability coefficient were measured, and a multi-step drainage monitoring experiment was conducted indoors at different dry densities, particle sizes, and degradation ages. Single and dual permeability models were adopted to determine the unsaturated hydraulic characteristic parameters of waste. Results show that dry density and particle size are the key factors affecting the saturated water content and permeability of waste. A single degradation age has little effect on it. Respectively, the saturated water content has a linear relationship with dry density, and permeability has an exponential relationship with dry density under limited experimental data. The overflow numerical inversion method can accurately obtain the unsaturated hydraulic characteristic parameters of wastes and summarizes the values of the unsaturated hydraulic characteristic parameters of wastes with different attributes in the literature and the results of this study. The dual-permeability model performed significantly better than the single-permeability model for water movement, suggesting that a dual-domain description is required for water flow in landfills. [ABSTRACT FROM AUTHOR]