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Planetary gear train is mainly used for power transmission, so it is of great significance to study its self-locking and efficiency. In this study, the self-locking analysis and efficiency maximization design of a 3K-H planetary gear train are carried out. Firstly, the efficiency of the positive and negative mechanism of the gear train is calculated using the transmission ratio method. Then, a unified formula for the efficiency of the planetary gear train is summarized. Furthermore, the efficiency curve is drawn by Matlab. Next, the trend of efficiency change of the planetary gear train and the conditions for realizing self-locking are analyzed. Finally, how to maximize the efficiency of the opposite mechanism under the condition of self-locking is studied.

Polyoxometalates (POMs) have shown great potential for applications in photocatalysis due to their unique structural features, tunable band gap, and environmental benignity. Herein, a Fe ion-incorporated Co4W6O21(OH)2·4H2O sphere network POM was successfully synthesized via a simple hydrothermal process. A DFT calculation proved that the Fe ion partially replaced cobalt atoms, forming FexCo4−xWOH, which played a crucial role in modulating the electron state and the band structure. The as-prepared FexCo4−xWOH exhibited excellent Fenton-like photocatalytic activity; the degradation rate of RhB improved 3.69 times compared with the sample without doping. The favorable performance of FexCo4−xWOH is a result of the synergistic effects of the Fenton reaction and the activation of H2O2 under visible irradiation, which can generate a mass of •O2− and •OH species in the unique sphere network structure. This study supplied a new idea for designing highly-active Fenton-like POM photocatalysts for environmental remediation. [ABSTRACT FROM AUTHOR]

Summary: Polyhydride electrocatalysts integrated directly into metal substrates have attracted attention because they can provide high electrochemical specific surface area and excellent mechanical properties. In this work, through the classical hydrothermal method and subsequent phosphating procedure, we synthesized for the first time an electrocatalyst with a pyramid‐shaped MnCO3 as the main structure, P and Co as co‐doping elements, named Co, P‐MnCO3, and used it as hydrogen evolution reaction (HER). The experimental results show that the excellent catalytic activity in alkaline media, with current densities of 10 and 200 mA∙cm−2 at 61 mV and 158 mV and low overpotentials, which are better than P‐Co (108/234 mV) and P‐MnCO3 (175 mV/340 mV), etc. it has more electrochemically active sites, faster charge transfer rate and lower resistance. The excellent electrochemical properties benefit from the unique highly active binary Co, P‐MnCO3 pyramid brick sites shortened the ion transfer distance and optimized synergistic effect between the doped metal elements (Co,P between MnCO3), the porous connection between Co, P‐MnCO3 and the high conductivity substrate, increased the electron‐transfer efficiency between the substrate and material, accelerating the conversion of H+ to H2; facilitated the release of bubbles and provided excellent mechanical properties for improved catalyst stability. This work provides a new idea for the synthesis of multi‐element electrocatalysts. [ABSTRACT FROM AUTHOR]

In order to solve the problems such as singleness of the absorption mechanism, difficulty of dispersion and inability of broadband absorption, carbon nanotubes were successfully prepared on the surface of acid oxidized carbon fiber by chemical grafting method. The effect of oxidation treatment on the carbon nanotubes modified carbon fiber and their electromagnetic properties were investigated. The results showed that the graft amount and graft efficiency of CNT were improved by oxidation treatment, resulting in the enhancement of the dielectric constant and the electromagnetic wave loss performance. At the condition of the nitric acid concentration of 65% and the reaction time of 8h, the grafted CNTs on the surface of CF reached 15.3% without agglomeration, which showed a good electromagnetic wave absorption property. [ABSTRACT FROM AUTHOR]

Due to the capability of perfect absorption, metamaterial becomes a hot research topic of wave absorbing materials in recent years. However, conventional metamaterials absorber is passive absorption and has the disadvantage that the wave-absorbing property can't be changed once the molding performed. Therefore, tunable metamaterials absorber gradually becomes one of the main research directions. Base on the research developments of tunable metamaterials absorber both of the domestic and foreign, several tunable methods were introduced in classification. Matrix structure and tunable mechanism was chief expounded. Furthermore, the tendency of change of wave absorbing characteristics curve and relationship between wave absorbing characteristics and effect factor were concluded. Finally, full text was summarized. The development trend of tunable metamaterials prospected. The important faction of tunable metamaterials absorber was explained. [ABSTRACT FROM AUTHOR]

An explicit upper bound Z(2, n) ≤ n + m - 1 is derived for the number of zeros of Abelian integrals M1(h) = ∮γ(h) P(x, y) dy - Q(x, y) dx on the open interval (0, 1/6), where γ(h) is an oval lying on the algebraic curve Hλ = (1/2)x2 + (1/2)y2 - (1/3)x3 - λy3 = h, P(x, y), Q(x, y) are polynomials of x and y, and max{deg P(x, y), deg Q(x, y)} = n. The proof exploits the expansion of the first order Melnikov function M1(h, λ) near λ = 0 and assume (∂m/∂λm)M1(h, λ)|λ = 0 not vanish identically. [ABSTRACT FROM AUTHOR]