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Elastic cushion plays an important role in alleviating the dynamic interaction between train and its running foundation. The ratio of static stiffness to dynamic stiffness is the key parameter to determine the alleviation performance of elastic cushion. Aiming at a new type of honeycomb mesh-type elastic cushion plate structure,a three-dimensional finite element model was established,and the mechanical properties of rubber material were simulated by super-elastic and viscoelastic constitutive models. Under the condition that the material parameters of elastic cushion plate were unchanged,the effects of the change of key parameters such as mesh thickness and aperture on the dynamic and static stiffness of mesh-type elastic cushion plate were studied,and the traditional groove elastic cushion plate was compared. The results show that: under the condition of constant mesh aperture,with the increase of mesh wall thickness,the static stiffness of elastic cushion plate increases and the ratio of dynamic stiffness to static stiffness decreases; under the condition of constant mesh wall thickness,with the increase of mesh aperture,the static stiffness of elastic cushion plate decreases and the ratio of dynamic stiffness to static stiffness increases;compare with the traditional grooved elastic cushion plate with similar static stiffness,the meshed elastic cushion plate has the characteristics of lower dynamic and static stiffness,smaller maximum stress value and more uniform stress distribution.Therefore,reasonable adjustment of mesh wall thickness and aperture size can make mesh elastic cushion plate suitable for track structures with different stiffness requirements,and the application of mesh structure to under rail elastic cushion plate can enhance the force transmission characteristics of cushion plate and prolong the service life of cushion plate.

The loss of water resources caused by mining fissures is a key factor restricting the green development of coal resources in western mining areas. in order to analyze the influence of mining thickness and face width on the development height of water diversion fracture zone, based on the characteristics of overburden in Xinzhuang Coal Mine, the finite difference software FLAC3D is used to simulate and analyze the size effect of water diversion fracture zone height. The simulation results show that the height of the water diversion fracture zone is positively correlated with the increase of mining thickness and working face width. When the mining thickness is 9m and the width of the working face is 240m, the height of the water diversion fracture zone is 115m, and the average distance between the coal layer 8 of Xinzhuang Coal Mine and the bottom of the Cretaceous aquifer is 106.9m, which may cause water inrush in the mine. Therefore, according to the simulation results and referring to the mining size of part of the mine face in the attached Binchang mining area, it is suggested that the mining thickness of Xinzhuang Coal Mine is about 10m and the width of the working face is not more than 200m.

The warpage of brominated flame-retardant PA66 composites was investigated in terms of the compositions without glass fiber and with the circular and flat glass fibers. The warpage of the composites was analyzed on the basis of their mechanical properties, crystallization properties, shrinkage rate and transverse/longitudinal shrinkage ratio. The results indicated that the composites without glass fiber had the highest crystallinity, transverse shrinkage and longitudinal shrinkage, but the lowest transverse/longitudinal shrinkage ratio and warpage. At the same content of glass fibers, the warpage of the composites with the flat glass fiber was obviously better than that of the composite with the circular glass fiber due to a lower ratio of transverse/longitudinal shrinkage. In the case of mechanical properties, the tensile strength and bending strength of the composites with flat glass fibers were lower than that of the composites with the circular glass fiber. The different types of glass fibers had little effect on the crystallization of the composites, and their crystallinity and crystallization peak temperature were very close to each other. At the same content of flame retardant, both the transverse shrinkage and the longitudinal shrinkage of the composites decreased with an increase in the content of the flat glass fiber. However, their transverse/longitudinal shrinkage ratio increased, leading to an increase in the warpage of the composites. [ABSTRACT FROM AUTHOR]

Two diblock copolymers of poly(methyl methacrylate)-block-poly(styrene) with chlorine as terminal group (PMMA-b-PS-Cl) were synthesized via two-step atom transfer radical polymerization. The structures of the block copolymers were characterized by Fourier transform infrared spectroscopy, proton nuclear magnetic resonance, and gel permeation chromatography. Thermal properties including glass transition temperature (Tg) and thermal stability were studied by differential scanning calorimetry and thermogravimetric analysis (TGA), respectively. The block copolymers of PMMA-b-PS-Cl exhibited two glass transitions, which were attributed to the Tgs of PMMA and PS segments, respectively. According to TGA, thermal decompositions of PMMA macro-initiator and PMMA-b-PS-Cl block copolymers had two stages. The weight loss ratio in the second stage was more significant than that in the first stage, which may be attributed to the separation of the halogen atom from the terminal group and the formation of a double bond. The breaking down of the backbone dominates in the second stage in which the weight loss ratio was more than 70%, represented the main stage of pyrolysis. It was found that the introduction of the PS chain remarkably enhanced the thermal stability of the copolymer, thus endowing the block copolymers high activation energy for thermal decomposition. On the other hand, the remaining two pyrolysis procedures further indicated that thermodynamic mechanism didn’t change due to the introduction of PS segments. [ABSTRACT FROM AUTHOR]

ABSTRACT Diblock copolymers poly(methyl methacrylate)- block-polystyrene with three different molar ratios [poly(methyl methacrylate)/polystyrene (PS) = 1:1, 1:1.5, and 1:1.8] were synthesized by atom transfer radical polymerization and used as a polymer matrix for gel polymer electrolytes (GPEs). The positron annihilation lifetime spectroscopy was applied to determine the free-volume behaviors of different GPEs, respectively. We illustrated that a proper PS ratio may led to the formation of a high fraction of free volume, and the influence of the PS ratio on the free-volume fraction was caused by the different morphologies of the GPEs because of the different packing densities of the PS rigid block. The ionic conductivity was correlated with the free volume in the GPE through the study of the ionic conductivity dependence on the temperature; this followed the Vogel-Tamman-Fulcher equation. Moreover, an ionic conductive model was proposed, in which variations of the free-volume behavior provide different ionic-conducting abilities. Thermogravimetric analysis indicated that GPEs based on different block copolymers exhibited high liquid-electrolyte preservation properties. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43901. [ABSTRACT FROM AUTHOR]

Chrome tanning agent is the most widely used tanning agent with the best performances of finished leather, but the traditional chrome tanning process poses severe challenges because of the serious chromium pollution, thus the upgrading of cleaner chrome tanning process is imminent. In order to reduce the residual chromium in wastewater and increase the utilization rate of chrome tanning agent, 4-acetyl-heptanediate (AHA), a high exhaustion chrome auxiliary, was developed and applied in chrome retanning process. The results showed that AHA chrome retanning processes (AHA-6 and AHA-4) significantly reduced the chromium content in wastewater by 48.14% and 47.57%, and increased the chromium content in leather by 102.14% and 82.43%. COD and TDS values decreased by 43.82% and 31.46% with AHA-4 method. The addition of AHA obviously reduced the chromium concentration of wastewater, improved the chromium absorption rate, and promoted the cleaner chrome retanning process, which satisfied with the overall requirements of modern sustainable leather industry. The formation of AHA and chromium (III) was discussed using Gaussian 16 program to explain the high exhaustion chrome tanning agent mechanism. The work will guide on design and preparation of new high exhaustion chromium tanning agents for clean leather production. [Display omitted] • AHA, containing carboxylic acid and ketone carbonyl groups, was developed for high exhaustion chromium retanning process. • Chromium content values of effluent liquors reduced sharply with AHA addition. • Total chromium content values of leather samples confirmed that AHA had a positive coordination effect on chromium ions. • Physical and mechanical properties clarified successful collagen modification and enhanced chromium coordination sites. • [Cr (AHA)]+ and [Cr (AHA) 2 ]- coordinations were demonstrated by molecular simulation. [ABSTRACT FROM AUTHOR]

Uranium (Ⅵ) exists as many species in natural water systems. In the recent years, its contamination to groundwater has been reported more frequently. To investigate the effects of speciation on the removal of uranium, this work investigated the uranium adsorption behaviors of a polyamine-grafted silica composite named SAER at the concentration level of μg/L in the alkaline carbonate solutions with other four resins. Results suggested that the change of uranium speciation had minor effect on the adsorption efficiencies of SAER, except the addition of calcium. This was resulted from that the protonated tetraethylenepentamine had a much higher affinity to the electronegative uranyl-carbonate species, leading to the complete removal of uranium through the simultaneous anion exchange and chemical transformation mechanisms; Column experiments confirmed that merely a small portion of calcium while no magnesium cations were involved in the uranium adsorption in the simulated groundwater. Finally, the integrated removal mechanisms were proposed. Overall, this work demonstrated the feasibility of a novel adsorbent for the effective removal of uranium from different water matrices as well as the mechanisms underlying the interaction of uranium and the functional groups on the adsorbents. Furthermore, it enhanced the understanding of uranium removal under environmentally relevant conditions. Image 1 • Uranium species distribution was calculated by PHREEQC software. • Five resins were compared on the adsorption behaviors under different conditions. • The removal efficiencies of uranium were higher than 99% by SAER. • Integrated adsorption mechanism towards uranium in groundwater was proposed. [ABSTRACT FROM AUTHOR]