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Abstract Titanium alloy with high corrosion resistance, high strength-to-density ratio, and excellent biocompatibility has a wide range of applications in the field of biomedical implants. Polishing experiments of titanium alloy with a small size and complex shapes were investigated using an ultrasonic assisted magnetorheological finishing (UMRF) device excited by a three-pole magnetic field generator. The models of the normal force and the shear force were first proposed based on the Preston equation to analyze the mechanism of material removal in the UMRF process. Subsequently, the single-factor experiments using titanium alloy nuts (M3) and the MR polishing fluid with silicon carbide abrasives were carried out. Furthermore, to improve the surface roughness and the change rate of surface roughness of nuts, orthogonal tests with a standard L9(34) orthogonal array were designed and performed based on the optimized process parameters obtained from the single-factor experiment. The results indicated the effect on surface roughness and change rate of surface roughness as applied current > roller speed > ultrasonic amplitude > spindle speed and applied current > roller speed > spindle speed > ultrasonic amplitude, respectively. Moreover, the surface roughness was improved from an initial 1.247 μm to a final 0.104 μm after the polishing for 80 min under these optimal process parameters.

Titanium alloy with high corrosion resistance, high strength-to-density ratio, and excellent biocompatibility has a wide range of applications in the field of biomedical implants. Polishing experiments of titanium alloy with a small size and complex shapes were investigated using an ultrasonic assisted magnetorheological finishing (UMRF) device excited by a three-pole magnetic field generator. The models of the normal force and the shear force were first proposed based on the Preston equation to analyze the mechanism of material removal in the UMRF process. Subsequently, the single-factor experiments using titanium alloy nuts (M3) and the MR polishing fluid with silicon carbide abrasives were carried out. Furthermore, to improve the surface roughness and the change rate of surface roughness of nuts, orthogonal tests with a standard L9(34) orthogonal array were designed and performed based on the optimized process parameters obtained from the single-factor experiment. The results indicated the effect on surface roughness and change rate of surface roughness as applied current > roller speed > ultrasonic amplitude > spindle speed and applied current > roller speed > spindle speed > ultrasonic amplitude, respectively. Moreover, the surface roughness was improved from an initial 1.247 μm to a final 0.104 μm after the polishing for 80 min under these optimal process parameters. [ABSTRACT FROM AUTHOR]

The climbing of trees to pick pinecones is a high-risk exercise. In this study, a mechanical gripper jaw was designed. Frictional characteristics between the pinecones and the mechanical gripper jaw during pinecone picking under different conditions were investigated using a workbench simulation, homemade inclined friction meter, and mass tester. Three-level orthogonal and one-factor tests were conducted. The relationship between the water content and friction properties and between the water content and hardness were investigated, and conclusions were drawn on how water content affected friction properties by influencing hardness. The results showed that the contact material greatly affected the friction properties. The pinecone water content was maintained between 24% and 28% to ensure that the coefficient of friction was maximized and that the pinecones were sufficiently hard to dislodge. Additionally, a prototype machine was used to perform pinecone-gripping experiments to validate the experimental and simulation results. Consequently, the results of this study provide a useful reference for the structural design of pinecone picking robots and the picking reason.

The climbing of trees to pick pinecones is a high-risk exercise. In this study, a mechanical gripper jaw was designed. Frictional characteristics between the pinecones and the mechanical gripper jaw during pinecone picking under different conditions were investigated using a workbench simulation, homemade inclined friction meter, and mass tester. Three-level orthogonal and one-factor tests were conducted. The relationship between the water content and friction properties and between the water content and hardness were investigated, and conclusions were drawn on how water content affected friction properties by influencing hardness. The results showed that the contact material greatly affected the friction properties. The pinecone water content was maintained between 24% and 28% to ensure that the coefficient of friction was maximized and that the pinecones were sufficiently hard to dislodge. Additionally, a prototype machine was used to perform pinecone-gripping experiments to validate the experimental and simulation results. Consequently, the results of this study provide a useful reference for the structural design of pinecone picking robots and the picking reason. [ABSTRACT FROM AUTHOR]

To effectively resolve the inherent conflict between dust control and ice prevention on truck roads during North Surface Coal Mine winters, initially, via monomer preference experiments, the optimal monomers for wetting, moisturizing, and condensing functions were identified as sodium dodecylbenzene sulfonate (B), glycerol (N), and polyacrylamide (R). In parallel, through compound synergistic experiments, the constituent elements of an anti-freezing agent were determined, referred to as F. Subsequently, a four-factor three-level orthogonal test was conducted employing the monomers B, N, R, and the anti-freezing agent F. This evaluation focused on four principal control parameters: penetration rate, evaporation resistance, viscosity, and freezing point. The results led to the identification of the optimal antifreeze and dust suppressant formulation, designated as B2N3R1F3. Within the North Open-Pit Coal Mine, the self-developed dust suppressant was applied to the field test section. Multiple parameters were examined for 6 consecutive days, encompassing the water content of the pavement geotechnical soil, the concentrations of total dust and exhaled dust, and the particle size distribution of dust within this road section. The field test results show that: the average water content of the road surface within the dust suppressant test section measured at 12%; the dust reduction efficiency of total dust and exhaled dust is 93% and 91%; the proportion of dust particles with a size exceeding 500 μm increased by 54.6%. These comprehensive findings provide a empirical framework for the effective resolution of the practical challenge of simultaneously managing dust control and frost protection on truck roads within surface coal mines. [ABSTRACT FROM AUTHOR]

Abstract The strength of the backfill is crucial for safe and efficient mining, and the cementing material is the key to obtaining a strong backfill. In this paper, industrial waste was used as a raw material, into which basis basalt fibres of different lengths and dosages were incorporated. First, the influencing factors were determined through orthogonal test designs. The optimal ratio of solid–liquid ratio of 2 and basalt fiber content of 2% and length of 6 mm was obtained, and thereby the complete proportion of the backfill material was obtained. The compressive strength and slump of the backfill material mixed with basalt fibres were investigated, and the interfacial mechanism of the backfill material was analysed at the microscopic level using scanning electron microscopy and X-ray diffraction. The results indicated that the degrees of influence of the different factors on the mechanical properties of the backfill material decreased in the following order: Solid–liquid ratio > fibre dosage > fibre length. Furthermore, there were different degrees of interaction among them. Under the best test proportion, that is, when the Solid–liquid ratio was 2, the fibre dosage was 2%, and the fibre length was 6 mm, the slump was 210 mm, and the compressive strength was 5.03 MPa. The mechanical properties were the best at this time. Through data regression, the relationship between the fibre dosage and the average peak stress was established, and the full curve expression for the uniaxial compressive stress–strain of the BFGF specimen was obtained. According to a microscopic characterisation analysis, the slag formed C–S–H gel, which contributed to the early-stage strength of the filling material; fly ash and coal gangue contained a large amount of aluminium, which formed hydrated aluminosilicate with a framework structure, and this contributed significantly to the later-stage strength of the backfill material. The addition of basalt fibres reduces the internal defects of the backfill, allowing the internal pore structure of the backfill to be optimised and the compressive strength to be increased. The results of this study have been successfully implemented in actual projects. Additionally, they provide a reference for similar mine management projects and have considerable promotion and application value.

Purposes This work is conducted to achieve the objectives of carbon emission reduction and resource utilization of solid waste. Methods Geopolymer concrete was prepared from red mud and coal-metakaolin, and the effect of four factors on its mechanical properties was investigated with an orthogonal test method. Findings The water-binder ratio was found to have a significant effect on the strength of the geopolymer concrete, followed by Na2O/H2O, while the curing conditions and the aggregate-binder ratio have lesser effect, according to the ANOVA. On the basis of the experimental results, the mathematical model of compressive strength and splitting tensile strength of geopolymer concrete was established, and the fitting effects of the equations were favourable. Further analysis obtained the optimal ratio of geopolymer concrete, and the compressive strength and splitting tensile strengthes of the cube specimens cured for 28 d were 43.6 MPa and 2.87 MPa, respectively. Then, the pore structures of the geopolymer concretes with different W/B ratios were characterised with low-field NMR tests. The results indicate that the geopolymer concrete is predominantly microporous internally. The increased content of evaporable free water increases the porosity and coarsens the pore structure, which macroscopically manifests as a reduction in strength of the material. This study can provide some theoretical guidance for the promotion and engineering application of geopolymer concrete.

Flax is an economically important fiber crop, however, it requires degumming to yield usable fibers. The degumming process of flax roving is a key step in flax processing and production. In this study, deep eutectic solvent (DES; choline chloride–urea) pretreatment was combined with microbial treatment to develop an ecofriendly and effective degumming method for flax roving. The optimal conditions for DES pretreatment (100°C for 120 min with 90% DES) were obtained through orthogonal tests. DES combine microbial treatment could effectively remove gum from the flax fibers. The flax roving fibers were characterized by chemical analyses, scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffractometry, and thermogravimetric analysis. Compared with fibers treated with microbes alone, flax roving fibers subjected to DES combine microbial treatment showed better breaking tenacity (16.77 cN/tex) and average pectin, hemicellulose, and lignin removal rates of approximately 86.4%, 26.7%, and 55.1%, respectively. NMR revealed that the composition of DES was not damaged during pretreatment, which means the bulk solution could be reused. This research showed that DES combine microbial treatment is feasible and effective method for flax roving degumming.

The synthetic jet piezoelectric air pump is a potential miniature device for electronic cooling. In order to improve the performance of the device, a small-sized synthetic jet piezoelectric air pump is proposed in this work, which is mainly characterized by petal-shaped inlet channels. First, the structure and working principle of the piezoelectric vibrator and the proposed pump are analyzed. Then, three synthetic jet piezoelectric air pumps with different inlet channels are compared. These inlets are the direct channels, the diffuser/nozzle channels, and the petal-shaped channels, respectively. Furthermore, the performance of the synthetic jet piezoelectric air pump with the petal-shaped inlet channels is optimized by orthogonal tests. Finally, the simulation was used to investigate the heat dissipation capability of the synthetic jet piezoelectric pump. The experimental results show that among the three inlet channels, the petal-shaped channel can greatly improve the performance of the pump. The unoptimized pump with petal-shaped channels has a maximum flow rate of 1.8929 L/min at 100 V, 3.9 kHz. Additionally, the optimized pump with petal-shaped channels reaches a maximum flow rate of 3.0088 L/min at 100 V, 3.7 kHz, which is 58.95% higher than the unoptimized one. The proposed synthetic jet piezoelectric air pump greatly improves the output performance and has the advantages of simple structure, low cost, and easy integration. The convective heat transfer coefficient of the synthetic jet piezoelectric pump is 28.8 W / (m 2 · ° C) , which can prove that the device has a better heat dissipation capability. [ABSTRACT FROM AUTHOR]

In this study, the effects of coal blending ratio, pyrolysis temperature, pyrolysis atmosphere and coal particle size on the quality of pyrolyzed char were investigated via a combination of orthogonal experimental design and grey relational analysis. Coal-XG and Coal-LL were pyrolyzed under various conditions to produce chars which were characterized to ascertain their properties such as chemical structure and reactivity. The results indicated that the pyrolysis temperature has the most significant impact on the quality of the char, followed by the pyrolysis atmosphere, coal blending ratio and coal particle size. The increase in pyrolysis temperature not only diminished char yield but also accelerated the consumption of oxygen-containing functional groups and the polycondensation of small aromatic ring structures throughout the reaction process. This led to a reduction in the reactivity of pyrolyzed char and the establishment of a more ordered structure. Meanwhile, the involvement of CO 2 and H 2 O prevented the condensation of small aromatic rings and fostered the generation of additional oxygen-containing functional groups, which resulted in lower yield and higher reactivity of the char under these two atmospheres. Through systematic analysis, only the Raman characteristic parameter I (Gr+VL+Vr) /I D exhibited a strong positive linear correlation with char reactivity, making it a reliable indicator for characterizing the reactivity of char. • The orthogonal design was used to study four response factors. • GRA was used to find optimal conditions and impact ranking of different factors. • Linear regression was applied to relate Raman/FTIR parameters to reactivity. • Blend experiments were conducted with two coking coals. [ABSTRACT FROM AUTHOR]

DEFORM-3D software was used to simulate the forging process with liquid core. Three orthogonal tests were designed to obtain the results with solid-phase thickness, reduction amount and pressing speed as three factors. The significant factors were acquired by the range analysis which affected the values of the equivalent strain and the equivalent stress in the solid-phase region, the solid–liquid two-phase region and the liquid-phase region. We mastered the deformation law during the forging process with liquid core. Four groups of the physical models of the multilayer gradient were also established under laboratory conditions. Fifty-three sets of forging parameters data were recorded including the solid-phase thickness, the reduction amount, the pressing speed and the forming pressure in each group. We constructed the relationship equation between the forming pressure and the other three factors in Origin. The equation provided a theoretical basis for selecting the press tonnage during the forging process with liquid core. [ABSTRACT FROM AUTHOR]

The synthetic jet piezoelectric air pump is a potential miniature device for electronic cooling. In order to improve the performance of the device, a small-sized synthetic jet piezoelectric air pump is proposed in this work, which is mainly characterized by petal-shaped inlet channels. First, the structure and working principle of the piezoelectric vibrator and the proposed pump are analyzed. Then, three synthetic jet piezoelectric air pumps with different inlet channels are compared. These inlets are the direct channels, the diffuser/nozzle channels, and the petal-shaped channels, respectively. Furthermore, the performance of the synthetic jet piezoelectric air pump with the petal-shaped inlet channels is optimized by orthogonal tests. Finally, the simulation was used to investigate the heat dissipation capability of the synthetic jet piezoelectric pump. The experimental results show that among the three inlet channels, the petal-shaped channel can greatly improve the performance of the pump. The unoptimized pump with petal-shaped channels has a maximum flow rate of 1.8929 L/min at 100 V, 3.9 kHz. Additionally, the optimized pump with petal-shaped channels reaches a maximum flow rate of 3.0088 L/min at 100 V, 3.7 kHz, which is 58.95% higher than the unoptimized one. The proposed synthetic jet piezoelectric air pump greatly improves the output performance and has the advantages of simple structure, low cost, and easy integration. The convective heat transfer coefficient of the synthetic jet piezoelectric pump is 28.8 W/(m2·°C), which can prove that the device has a better heat dissipation capability.

• Material removal modeling of cylindrical polishing considering multi-scale contact. • Surface roughness modeling by Hertz contact, G-W model and single grain cutting. • Taguchi orthogonal experiments, ANOVA and level average response analysis. • Discussion of contact area, contact gap, single grain's cutting depth. • Investigation on influences of loading force and grain size at multi-scale. In this paper, the material removal and the surface roughness in the cylindrical polishing with a soft pad and free abrasives are investigated theoretically and experimentally. Existing our studies have suggested that there is different contact deformation at dimension scales of millimeter, micrometer and nanometer. On that basis, the material removal model is proposed by integrating the contact at different scales in accordance with the Hertz contact, the Greenwood and Williamson's model (G-W model) of rough contact and the single grain's cutting depth. Furthermore, a model of surface roughness is built based on the idea that more materials are removed at the peak on the workpiece's surface, whereas few materials are removed at the valley. The polishing experiments and simulation of cylindrical AISI 52100 steel using the polyurethane polishing pad and the free abrasives of aluminum oxide powder were performed through the Taguchi orthogonal tests, which indicated that the simulation results were well consistent with the experimental results. Under the optimal conditions, the material removal rate (MRR) of 0.40 μm/min was achieved, and the surface roughness R a was reduced from 104.90 to 20.22 nm after the polishing for 12 min. The contributions of the loading force, the abrasives concentration and the grain size on the MRR and the surface roughness are investigated in accordance with the variance and the level average response, and their reasons are discussed at different scales. It is revealed that the influences of loading force and grain size are significantly different at multi-scale. Furthermore, the parameters related to the contact (e.g., nominal contact area, average contact gap and single grain's cutting depth) under different conditions are studied. [Display omitted] [ABSTRACT FROM AUTHOR]

In this paper, TiO 2 -based geopolymer microspheres (TiO 2 @GMs) were prepared by dispersion-suspension-solidification technique using water glass activated metakaolin-based geopolymer slurry as a binder. The effects of different factors on the sphericity and particle size of TiO 2 @GMs were investigated, and the order of importance was found to be TiO 2 dosage > water volume > water glass modulus > rotation speed. Secondly, in the Fenton system under UV light irradiation, TiO 2 @GMs exhibited excellent performance in the degradation of tetracycline hydrochloride (TC). At a TC concentration of 20 mg/L, liquid-to-solid ratio of 0.3 g/L, H 2 O 2 (30 wt%) of 10 mM, and pH = 4.47, 98.6% TC was degraded by TiO 2 @GMs within 30 min TiO 2 @GMs can be easily separated from the reaction product and showed excellent recycling performance, with a degradation efficiency of 90.6% after five success reuses. Finally, a plausible photocatalytic degradation mechanism of TiO 2 @GMs for TC was discussed. This newly designed TiO 2 @GMs composite can be deemed as an alternative material for the degradation of TC and other similar antibiotic on large scale. [Display omitted] • Preparation of different TiO 2 @GMs by suspension dispersion solidification method. • The degradation process of TC by TiO 2 @GMs includes adsorption and photocatalytic. • The degradation rate of TC by TiO 2 @GMs is better than that of similar catalysts. • TiO 2 @GMs have excellent recycling and rapid settling properties. • The photocatalytic degradation mechanism of TC by TiO 2 @GMs was explained. [ABSTRACT FROM AUTHOR]