Simulation Research on the Time-Varying Meshing Stiffness and Vibration Response of Micro-Cracks in Gears under Variable Tooth Shape Parameters

The gear is one of the important parts of a rotary gearbox. Once catastrophic gear failure occurs, it will cause a great threat to production and life safety. The crack is an important failure factor causing changes in time-varying stiffness and vibration response. It is difficult to effectively identify the vibration response and meshing stiffness changes when there is a fine crack in the gear. Therefore, it is of great importance to improve the accuracy of meshing stiffness calculation and dynamic simulations under micro-cracks. Investigations of meshing stiffness and the vibration response of a gearbox is almost all about fixed gear shape parameters. However, the actual production process of gear system needs to change gear shape parameters. In this paper, the meshing stiffness and vibration response of the dynamic simulation signals of gear teeth with different crack depths at different tooth shape parameters (the pressure angle, the modulus, and the tooth number) were calculated, respectively. The influence of cracks on the vibration response was investigated by the fault detection indicators, the Root Mean Square (RMS), the kurtosis, and the crest factor. The result shows that when the pressure angle and modulus change, the vibration response changes erratically. However, when the tooth numbers change, the vibration response changes regularly. The results could be a guide for choosing gears in different shape parameters when system stability is the aim

Phosphate Removal from Secondary Effluents Using Coal Gangue Loaded with Zirconium Oxide

Phosphorus from secondary effluents and coal gangue from coal mining have caused serious environmental problems. The feasibility of phosphate removal from secondary effluents using calcinated coal gangue loaded with zirconium oxide (CCG-Zr) was explored. Major influencing factors like the calcinated temperature, CCG-Zr ratio, adsorbent dose, time and solution pH, etc. were investigated. Newly developed CCG-Zr accomplished a significantly higher phosphate removal for phosphate (93%) compared with CCG (35%) at a calcinated temperature of 600 °C and CCG-Zr mass ratio of 1:1. For CCG-Zr the maximum phosphate removal rate (93%) was noted at an initial phosphate concentration of 2 mg/L within 20 min. The CCG-Zr displayed a higher phosphate removal rate (85−98%) over a wide range of solution pH (2.5~8.5). The adsorption isotherms fitted better to the Freundlich (R2 = 0.975) than the Langmuir model (R2 = 0.967). The maximum phosphate adsorption capacity of the CCG-Zr was 8.55 mg/g. These results suggested that the CCG-Zr could potentially be applied for the phosphate removal from secondary effluents

Tunable Coupled-Resonator-Induced Transparency in a Photonic Crystal System Based on a Multilayer-Insulator Graphene Stack

We achieve the effective modulation of coupled-resonator-induced transparency (CRIT) in a photonic crystal system which consists of photonic crystal waveguide (PCW), defect cavities, and a multilayer graphene-insulator stack (MGIS). Simulation results show that the wavelength of transparency window can be effectively tuned through varying the chemical potential of graphene in MGIS. The peak value of the CRIT effect is closely related to the structural parameters of our proposed system. Tunable Multipeak CRIT is also realized in the four-resonator-coupled photonic crystal system by modulating the chemical potentials of MGISs in different cavity units. This system paves a novel way toward multichannel-selective filters, optical sensors, and nonlinear devices

Effect of Biochar on Soil Temperature under High Soil Surface Temperature in Coal Mined Arid and Semiarid Regions

High soil surface temperature and loosened soil are major limiting factors of plant productivity in arid and semi-arid coal mining areas of China. Moreover, the extensive and illegitimate burning of crop residues is causing environmental pollution; whereas, these residues could be converted to biochar to benefit soil quality. In this study, the effect of wheat straw biochar (WSB) at rates of 0% (control, CK), 1% (low, LB), 2% (medium, MB) and 4% (high, HB) on soil temperature at different depths (5, 10, 15, and 20 cm) and moisture levels (10 and 20%) was investigated under high soil surface temperature of 50 °C and air humidity of 40%. Our data suggested that soil bulk density was inversely, and soil moisture was directly corelated with soil thermal parameters. Moreover, the increasing rate of WSB addition linearly decreased the soil thermal properties. The maximum decrease in soil bulk density at both moisture levels (10% and 20%) was measured in HB treatment compared to respective CKs. The highest decrease in soil thermal conductivity (59.8% and 24.7%) was found under HB treatment in comparison to respective controls (CK10% and CK20% moisture). The soil volumetric heat capacity was also strongly corelated with soil moisture content (r = 0.91). The WSB treatments displayed differential responses to soil temperature. Under 10% soil moisture, temperature of LB, MB and HB treatments was higher as compared to CK at 5–20 cm depth, and MB treated soil had the smallest increase in temperature. At the 15-cm depth, the MB treatment decreased the temperature by 0.93 °C as compared to the CK20%. Therefore, the effect of WSB on soil temperature was influenced by soil moisture content, soil depth and WSB application rates. It suggested that MB treatment could be a useful farming practice for mitigating soil temperature fluctuation

Preparation of Silver Nanoparticles Loaded Photoresponsive Composite Microgels and Their Light-Controllable Catalytic Activity

A new type of smart composite microgels, which are able to control the catalytic activity of their loaded silver nanoparticles by light, was designed and fabricated based on the idea of function transfer between their constituent components. First, the surfaces of monodisperse gold nanorods (AuNRs) with strong photothermal effect were coated with poly­(<i>N</i>-isopropyl­acrylamide) (PNIPAM) hydrogel by seed precipitation polymerization to prepare the two-component composite microgels with core–shell structure (AuNR@PNIPAM microgels). Then, Ag⁺ ions coordinated into the shell of AuNR@PNIPAM microgels were <i>in situ</i> reduced by sodium borohydride to produce silver nanoparticles (AgNPs) loaded three-component composite microgels (AuNR@(AgNPs/PNIPAM) microgels). The characterization results obtained by transmission electron microscopy show that the gold nanorod is located at the center of the three-component composite microgels and AgNPs with the average particle diameters of 6–10 nm are evenly distributed within its shell. The hydrodynamic diameters of the composite microgels, measured by dynamic light scattering before or after exposure of their aqueous dispersion to near-infrared (NIR) laser of 808 nm wavelength, indicate that they have photoresponsive property. The AgNPs and AuNR inside AuNR@(AgNPs/PNIPAM) microgels hold their respective localized surface plasmon resonance (LSPR) optical property, and the longitudinal LSPR wavelength of the latter is blue-shifted with increasing content of the former. Moreover, the LSPR efficiency of the AgNPs and the longitudinal LSPR wavelength of the AuNR are capable of being changed in response to the NIR illumination, and the stimulus-responsive behavior is reversible. AuNR@(AgNPs/PNIPAM) microgels are able to be used as the smart microreactor for reducing 4-nitrophenol by NaBH₄, and the reaction rate can be modulated by power density of the NIR light, demonstrating that the three-component composite microgels have light-controllable catalytic activity

Horizontal Heat Impacts of a Building on Various Soil Layer Depths in Beijing City

There is a lot of research on the urban thermal environment, mainly on air temperature. However, fewer studies focus on soil temperature that is influenced by built environment, especially on the horizontal heat impacts from buildings. In this research, soil temperature was investigated at different depths in Beijing, China, to compare the differences between two locations. One was next to the building and the other was far away from the building (10 m). The locations are referred to as site A and site B, respectively. These two sites were chosen to compare the differences in soil temperatures between them to present the horizontal heat impact from facade. The results show that facades caused horizontal heat impacts on the soil at different depths in the winter, spring, and summer. Basically, facades functioned as heat sources to the soil surrounding them. The mean temperature differences between the two sites were 3.282, 4.698 and 0.316 K in the winter, spring and summer, respectively. Additionally, the thermal effects of the buildings were not only exhibited as higher soil temperatures but the temporal appearance of the maximum and minimum temperature was also influenced. Buildings functioned as heat sources to heat soil in the winter and spring and stabilized soil temperature so that it would not fluctuate too much in the summer. Additionally, the coefficient of variation indicates that buildings primarily increased the soil temperature in the winter and spring and stabilized the soil temperature in the summer

A water-soluble PAAs sizing agent for enhancing interfacial adhesion of carbon fiber reinforced polyphenylene sulfide composites (CF/PPS)

Due to low activity and poor wettability of carbon fiber (CF), the interaction between CF and polyphenylene sulfide (PPS) matrix is weak, which decreases the mechanical properties of CF reinforced PPS （CF/PPS） composites. In this article, the interfacial adhesion of CF/PPS composites was strengthened by using a water-soluble poly (amic acid) ammonium salt (PAAs) as sizing agent. This PAAs-based sizing agent had good compatibility with PPS and formed hydrogen bonds with CF activated by Meldrum’s acid. Significantly, the PAAs sizing agent can be soluble in water (up to 20 wt % high solid content) without organic solvents and surfactants, which shows huge potential in industrial applications. Experimental results demonstrated that the interlaminar shear strength (ILSS), flexural strengths, and moduli of modified CF/PPS composites increased by 19.5%, 24.9%, and 10.1%, respectively. According to the SEM images on fractured surfaces of composites, fiber and PPS resin were tightly packed, and the failure mechanism was interface deformation or resin breakage.</p