High-speed trains rely on pantograph-catenary systems (PCSs) to collect electrical energy from power systems. However, the dynamic interaction between the pantograph and the catenary system may become mismatched once ice accumulates on the overhead conductors. More frequent arcing may occur within the PCS during train operation, posing an unpredictable threat to operational safety. Therefore, it is crucial to evaluate the ability of overhead contact system (OCS) to withstand ice-covered variability during line desgin. A new strategy is proposed to evaluate the adaptive performance of an OCS under various icing conditions. First, a dynamic model considering icing conditions is constructed to simulate the interaction within the PCS. Five different OCS structures with various icing thicknesses are studied. The parameters of the contact force within the PCS and proportion of high-possibility arcing moments are obtained. The dependence of the contact force on the icing thickness and pantograph displacement has been illustrated in the form of cloud maps. Finally, the OCS sensitivity coefficient is calculated, and ice-covered environmental adaptability assessments for the five different OCS oes structures are compared.

This study investigated the influences of polymer types (Super Absorbent Polymer, SAP and Polyanionic Cellulose, PAC), preparation methods (dry-mixed, dry-sprinkled, or wet-mixed), initial polymer loadings (1.0%, 2.5%, 5.0%, 10.0%, and 15.0%), and bauxite liquors (synthetic bauxite liquor, BLS and actual bauxite liquor, BLA) on the polymer elution and the hydraulic conductivity of polymer-bentonite geosynthetic clay liners (PB GCLs). Hydraulic conductivity, total organic carbon analysis, viscosity, scanning electron microscopy, Fourier transforms infrared spectroscopy, and X-ray diffraction tests were combined to investigate the mechanisms controlling the polymer elution and hydraulic conductivity of PB GCLs. The results demonstrated that PB GCLs with high initial polymer loading (10.0%, 15.0%) or prepared using the dry-sprinkled method had low hydraulic conductivities (< 1.0 × 10−10 m/s) and polymer eluting rates (< 10.0 mg/d). PAC-enhanced GCLs had a higher polymer eluting rate than SAP-enhanced GCLs due to the complete water solubility of linear polymer (PAC). When PB GCLs were permeated by BLS (higher ionic strength than BLA), polymer hydrogels had lower viscosity because of coiled or contracted conformation, resulting in a higher polymer eluting rate (> 50.0 mg/d) and hydraulic conductivity (> 1.0 × 10−11 m/s).

As part of the pantograph-catenary system, a catenary covered with ice can affect the current collected by pantograph sliding, posing a threat to the normal operation of the train. At the icing conditions, the speed reduction method is usually adopted in practical engineering to ensure the stable energy transfer quality of the pantograph-catenary system, while its reduction ranges remain unclear. To aim at providing speed recommendations for safe train operation under various ice conditions in practical engineering, the model of the icecovered pantograph-catenary system is established in this work and the effect of ice covering on both the static characteristics of the catenary and the dynamic interaction of the system are investigated. The results indicate ice increases the stiffness and sag of the contact wire, resulting in a significant increase in elastic inhomogeneity across the span of the contact wire. As ice thickness and train speed increase, there is an increase in the vibration amplitude of support point and an increase in the fluctuation range of the contact force. It is suggested that the operational speeds of trains should be less than 350 km/h, 330 km/h, 280 km/h, and 260 km/ h, corresponding to the ice thicknesses of 4 mm, 8 mm, 12 mm, and 16 mm, respectively.

This study investigated the influences of polymer types, polymer loadings, and preparation methods on the hydraulic conductivity of polymer-enhanced bentonite geosynthetic clay liners (EB GCLs) to coal gangue leachate (CL). Sodium carboxymethylcellulose (CMC) and xanthan gum (XG) were selected to modify the sodium-bentonite GCLs (Na-B GCLs), with a range of polymer contents from 5% to 15%. The EB GCLs were prepared by wet-mixed, dry-mixed, and dry-sprinkled methods. Detection of effluent in the hydraulic conductivity test by inductively coupled plasma mass spectrometry (ICP) and analysis of EB GCLs’ morphologies by scanning electron microscopy (SEM) were conducted to explore the mechanisms controlling the hydraulic conductivity of EB GCLs. The hydraulic conductivity decreased with increasing swelling of the bentonite when the EB GCL had a low polymer loading (5%). However, no significant correlation was observed between the swell index and the hydraulic conductivity when the EB GCL had a high polymer loading (10% and 15%). Moreover, the polymer type and preparation method had little effect on the hydraulic conductivity of the EB GCLs when polymer loading increased to 15%. The ICP results indicated a decrease in ionic strength and an increase in RMD of the CL by cation scavenging, leading to an increase in the possibility of osmotic swelling. Additionally, SEM images showed that the clogging of pore spaces by the polymer was the main reason for the decreased hydraulic conductivity of EB GCLs.

高速列车车载真空断路器(VCB)性能是列车安全稳定运行的重要保证之一.近年来,国外某型号动车在过分相时出现VCB延时断开故障,导致只能通过降弓方式来预防带电过分相引发的安全隐患.针对以上问题,推测其原因是VCB触头间电弧烧蚀或牵引变压器合闸时刻励磁涌流导致的VCB过载造成.主要针对牵引变压器合闸励磁涌流进行研究,通过现场测试和PSCAD仿真探究励磁涌流的影响因素和实际可达到的最大值.结果表明,列车过分相VCB完成合闸后实测最大电流达到 756.67 A,不会对VCB触头造成实质性损伤.牵引变压器励磁涌流大小主要受VCB合闸电压相角和变压器铁芯剩磁影响,且励磁涌流并非导致VCB触头熔焊的主要因素,VCB合断时触头间的电弧烧蚀才是造成VCB触头熔焊的主要原因.

High-speed railway pantograph-catenary system is the only energy transfer pathway to drive a train operation. Energy transfer quality deteriorates with the increasing train speed and harsh service environment, thereby quickly and accurately evaluating the energy transfer quality is very important to guarantee the normal oper-ation of a train. In this study, firstly, the physics-based model to simulate the dynamic interaction of pantograph -catenary system is established and validated. Eleven input parameters involve the essential line design and train operation parameters, and the output parameters that are crucially responsible for energy transfer quality are obtained by feature extraction. Secondly, a sampling strategy is employed to construct the input sampling points, based on which the outputs are computed via physics-based model, then combining them the dataset is obtained. Thirdly, five tree-based classification surrogate models are developed and compared to assess the level of energy transfer quality. Finally, eight regression surrogate models are developed in replacing physics-based model to evaluate the essential values of energy transfer quality. It is found that the gradient boosting decision tree (GBDT)-based surrogate model is the optimal classification model and the multi-layer feed-forward deep neural network (MLF-DNN)-based surrogate model for the optimal regression model. The two surrogate models are expected to quickly find the optimal design parameters and improve the operation control of trains of high-speed railway for the purpose of enhancing the energy transfer quality if coupled with optimization procedure.

时速 400 km高速铁路技术的研发是我国加快建设交通强国的重要环节.国内尚未有适用于 400 km下弓网参数评判标准,且现有弓网结构参数无法满足该速度下列车的稳定受流.在建立弓网动力学模型的基础上,基于高速铁路设计规范,尝试建立适用于时速 400 km下弓网接触力和离线率的评判标准,并提出 400 km/h下弓网各结构参数优化设计方案.结果表明,选用接触线张力 35 kN、承力索张力 21 kN、接触网弛度 0.2‰、弓头悬挂刚度9000 N/m、弓头悬挂质量 6.0 kg、弓头悬挂阻尼 80 N·s/m的参数值时,可将弓网接触力最大值、平均值、标准偏差分别由 318.04,241.34,58.91 N 减小到 280.51,220.59,50.87 N,减小了 11.80％、8.60％、13.65％,将离线率由4.33％减小到 0.94％.优化后的弓网结构参数可以优化接触网弹性均匀程度、增强受电弓与接触网间的跟随性,从而改善弓网匹配效果,提高列车受流质量.研究成果可对 400 km/h弓网参数评判标准的制定提供理论支撑.

Red-mud leachate from tailings ponds contains Cr(VI), which can pollute groundwater via infiltration through anti-seepage layers. This paper investigates leachate from a red-mud tailings pond in southwest China and the red clay in the surrounding area to simulate the adsorption of Cr(VI) onto clay at different pHs, using geochemical equilibrium software (Visual MINTEQ). We also performed dynamic adsorption testing of Cr(VI) on a clay anti-seepage layer. The dynamic adsorption behaviors and patterns in the dynamic column were predicted using the Thomas and Yoon–Nelson models. Visual MINTEQ predicted that Cr(VI) adsorption in red-mud leachate onto clay was 69.91%, increasing gradually with pH, i.e., adsorption increased under alkaline conditions. Cr(VI) concentration in the effluent was measured using the permeability test through a flexible permeameter when the adsorption saturation time reached 146 days. At a low seepage rate, Cr(VI) adsorption onto the clay anti-seepage layer took longer. Saturation adsorption capacity, q0, and adsorption rate constant, Kth, were determined using the Thomas model; the Yoon–Nelson model was used to determine when the effluent Cr(VI) concentration reached 50% of the initial concentration. The results provide parameters for the design and pollution prediction of the clay anti-seepage layer of red-mud tailings ponds.

Heat transfer within ceramic feedstock powders is still unclear, which impedes optimization of the thermal and mechanical properties of the thermal sprayed coatings. The microspheres (yttria-stabilized zirconia YSZ and lanthanum zirconate LZO) were prepared via the electro-spraying assisted phase inversion method (ESP). The thermal properties of the two ESP microspheres and a commercial hollow spherical powder (HOSP) were investigated by using theoretical, experimental, and simulation methods. Thermal conductivity of the single microsphere was estimated via a novel nest model that was derived from the Maxwell-Eucken 1 and the EMT model. Thermal conductivity of a single YSZ/LZO-ESP microsphere prepared at 1100-1200 degrees C was within 0.36-0.75 W/m K, which was ti 20 % lower than that of a single YSZ-HOSP microsphere with a similar porosity. Heat flux simulation showed that high tortuosity around the multi-scaled voids of the ESP microsphere led to a more efficient decrease in thermal conductivity compared with total porosity.(c) 2022 Published by Elsevier B.V. on behalf of The Society of Powder Technology Japan.

Carbon species incorporation and carbon deposits are common in the manufacture process and application of yttria-stabilized zirconia (YSZ) ceramics, while the potential corrosion induced by the resultant carburization is unclear. The 3YSZ hollow fiber membranes were prepared by wet spinning method. A sintering procedure at 1300-1450 degrees C under 0.02 MPa oxygen partial pressure, and thereafter an oxidation treatment at 800 degrees C were applied to investigate the carbothermal reaction and carburization corrosion mechanism. It was found that the trace carbon species of 1.0-2.2 mol% derived from polymeric precursors triggered the carburizing strengthening of porous YSZ membranes without sacrificing porosity and deformability. However, the carburization corrosion also occurred at the mild oxidation treatment, resulting in deterioration in bending strength and integrated structure converting into fine grains. Raman spectra, XPS bands and HR-TEM images confirmed that the in-situ synthesized ZrCxOy oxidized into monoclinic ZrO2, and micro-cracking formed along grain boundaries, which led to substantial mechanical strength loss.

The thermal cycling lifetime of thermal barrier coatings was doubled when deposited by electro-sprayed (ESP) microspheres instead of by commercial hollow spherical powders. It was believed that partial-molten nodules with featured microstructures inherited from the feedstock microspheres were the main contributor for prolonged thermal cycling durability due to improved fracture toughness and strain tolerance. The maximum lifetime was observed on samples with 20-30 vol.% of partial-molten microspheres. The hierarchy pores may both slow down the crack propagation by triggering multi-deflecting and promote cracking by reducing the tendency of interfacial deflection, the net effect depends on situation. The ESP coatings exhibited bimodal Weibull moduli upon indentation, which was regarded as originated from the hierarchy porous structure. Finally, the criterion was verified by micro-indentation and residual stain-stress evaluation by Raman spectroscopy.

The compression strength and breakage mechanism of a hierarchical porous sphere in hundred-micron size were investigated in the present work. 3 mol% yttria-stabilized zirconia (YSZ) microspheres were prepared by electrospraying associated with phase inversion (ES-PI) technique. The characteristic compression strengths of the ES-PI microspheres were measured by quasi-static uniaxial compression test, which increased from 19 MPa to 155 MPa as the sintering temperature increased from 1100 degrees C to 1400 degrees C. With the similar porosity, the compression strength of the hierarchical structure microsphere was almost three times higher than that of the hollow microsphere. Further, the breakage mechanism of the ES-PI microspheres was proposed by the honeycomb model of cellular materials, which suggested that the breakage of the ES-PI microsphere initiated from the elastic instability of the walls around the finger-like pores. These findings can help the mechanical performance optimization for ceramic microspheres with lightweight structure.

During high temperature service, a series of microstructure and phase evolutions occur in thermal barrier coatings (TBCs), which result in degradation of thermal insulation and durability. In this study, the sintering behavior of an air plasma sprayed 8 wt% YSZ coating deposited using electro-sprayed nanostructured particles (ESP) as feedstock powder was investigated and compared with conventional YSZ coating deposited using hollow spherical powders (HOSP). Due to the distinct asymmetric porous structure formed by nanosized YSZ particles, the ESP powder was partially melted in the plasma jet during the deposition, which resulted in the formation of a nanostructured coating that consisted of porous nanozones and dense zones. The ESP coating not only shows a significantly lower initial thermal conductivity of 0.70 W/mK, but also exhibits a stronger sintering resistance in terms of phase stability and thermal insulation compared to the conventional coating. When subjected to prolonged sintering at 1400 degrees C for 128 hours, the thermal conductivity of the ESP coating would gradually increase to about half that of the HOSP coating at 1.29 W/mK. These differences are ascribed to the interaction among different sintering behavior between nanozones and dense zones.

Hydrophobic coatings that could survive in harsh environment have a wide range of applications from industry to houseware. However, the state-of-the-art polymer-based coatings cannot meet such requirements due to their low melting point and poor wear resistance. In this study, we reported a plasma sprayed ceramic coating made of ceria with exceptional hydrophobicity, high-temperature stability, and good wear resistance. The coating exhibited a water contact angle (WCA) up to 139 degrees, due to the intrinsic hydrophobicity of ceria and unique surface morphology produced by plasma spraying. The WCA only slightly decreased to 131 degrees after annealing at 773 K. In addition, the polished coating (WCA similar to 116 degrees) was still more hydrophobic than the sintered bulk specimen (WCA similar to 95 degrees) with the same composition and roughness, which can be attributed to the surface chemistry change induced by Ar+ ion bombing by plasma. It is believed that such robust hydrophobic coating should have great potential in engineering application.

Y2SiO5 is a promising material for the thermal barrier coatings due to its low thermal conductivity, high temperature stability and exceptional resistance for molten silicate attack. However, it suffers low fracture toughness and low coefficient of thermal expansion compared with yttria-stabilized zirconia (YSZ). In this study, a composite coating approach, i.e., incorporating YSZ into Y(2)SiO(5 )coating, was employed to overcome those limitations. The double-layered Y2SiO5-YSZ/YSZ coatings were fabricated using atomospheric plasma spraying and tested under thermal cycling at 1150 degrees C. The phase compositions, microstructure, mechanical properties and the failure behavior were evaluated. It was found that the amorphous phase during spraying would crystallize at high temperature accompanied by volume shrinkage, leading to cracks and spallation in the coating. With YSZ addition, the composite coatings exhibited a much longer lifetime than the single phase Y2SiO5 coating due to a lower volume shrinkage and enhanced toughness.

An approach to make air plasma sprayed (APS) thermal barrier coatings (TBCs) with the enhanced strain and damage tolerance was reported, using a novel hollow spheres produced by electro-spraying (ESP) technique. Compared with agglomerated & sintered (A&S) and hollow spherical (HOSP) yttria-stabilized zirconia (YSZ) powders, the ESP powder showed a unique network microstructure and the TBCs exhibited a 2-3 times longer thermal cycling lifetime. The splat morphology and the top coats microstructure were investigated. Some semi-melted ESP particles were observed in the as-sprayed top coat. The indentation coupled with the Raman mapping technique was employed to evaluate the strain and damage tolerance of the TBCs. The coatings deposited by the ESP powder show a lower in-plane stiffness determined by three-point bending tests. It is proposed that the superior performance is attributed to the lower amount of the short microcracks (0.5-4 μm) with low angle (< 45°) and the semi-melted ESP particles remained in the YSZ top coat.

In-depth temperature sensing in air plasma sprayed (APS) thermal barrier coatings (TBCs) has been achieved with europium (Eu) and dysprosium (Dy) doped yttria stabilized zirconia (YSZ) sensor coatings. The luminescence properties of YSZ:Eu and YSZ:Dy, including spectrum, intensity and lifetime, were evaluated and their temperature sensing performances were compared using a lifetime-based measurement system. Both sensor TBCs display excellent temperature sensitivity in high temperature environment (400–800°C for YSZ:Eu, 500–900°C for YSZ:Dy) with a topcoat thickness up to 300μm. It was found that the upper limit of temperature sensing was determined by the ratio between luminescence intensity and background thermal radiation (signal-background-ratio). YSZ:Dy showed higher luminescent intensity than YSZ:Eu at elevated temperatures, and therefore displayed better temperature sensing performance with an increased limit. The effect of topcoat thickness on the temperature sensing performance was also evaluated, showing that the attenuation factor of YSZ increased significantly with topcoat thickness. Interestingly, it was found that the topcoat attenuation factor gradually decreased as temperature increased, which improved the temperature sensing performance of sensor TBCs at elevated temperature. The findings in the temperature sensing of APS TBCs provide basis for the future development of on-line APS TBCs temperature monitoring technology.

A micrometer scale method based on the principle of liquid rope coiling with the assistance of nonsolvent-induced phase inversion is introduced to fabricate YSZ coils. The YSZ coils with the filament diameter of several hundreds of micrometer exhibit stable spring properties and excellent elongation at failure. With the spring rate in the range from similar to 2 N/mm to similar to 21 N/mm and the elongation up to 4.36%, both the two properties can be effectively controlled and tailored since they both strongly depend on the geometric dimensions varied with the process parameters. Besides, the simple method provides an alternative method for the large-scale production and customization of ceramic coils with diverse applications.

Hollow microspheres were prepared by a combination method of electro-spraying and non-solvent induced phase separation, using a slurry of polymer with Y2O3-stabilized ZrO2 powder (YSZ). Subsequent sintering was carried out to obtain porous hollow YSZ microspheres with proper strength aiming to be thermal spraying feedstock. The ESNP particle size and distribution strongly depended on the applied voltage of the electro-spraying process and the jet nozzle diameter. The YSZ microspheres always consisted of a thin spongy shell and highly porous interior structure. The microsphere size decreased from 1000 to 100μm with increasing voltage (10–20kV). The cone-jet mode of electrospray reached steady as the nozzle diameter varied from 0.5 to 0.8mm. Compared with the coatings made from commercial hollow spherical powder, the coatings prepared by ESNP powder had enhanced resistance to sintering and exhibited a longer life than commercial spray powder. It has demonstrated that the ESNP method provides a versatile way to manipulate the microstructure of ceramic microspheres, and could been used to fabricate high performance thermal barrier coatings by plasma spraying.