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A series of catalysts with different core-shell structures has been successfully prepared by a hydrothermal method. They consisted of CeCoOx @TiO2 (single shell), CeCoOx @Nb2 O5 (single shell) and CeCoOx @Nb2 O5 @TiO2 (double shell) core-shell nanocages and CeCoOx nanocages, in which CeCoOx was the core and TiO2 and Nb2 O5 were shells. The influence of the core-shell structure on the catalytic performance of o-dichlorobenzene was investigated by activity, water-resistance, and thermal stability tests as well as catalyst characterization. The temperatures corresponding to 90 % conversion of o-dichlorobenzene (T90 ) of CeCoOx , CeCoOx @TiO2 , CeCoOx @Nb2 O5 , and CeCoOx @Nb2 O5 @TiO2 catalysts were 415, 383, 362 and 367 °C, respectively. CeCoOx @Nb2 O5 exhibited excellent catalytic activity, mainly owing to the special core-shell structure, large specific surface area, abundant activity of Co3+ , Ce3+ , Nb5+ , strong reducibility, and more active oxygen vacancies. It can be seen that the Nb2 O5 coating can greatly improve the catalytic activity of the catalyst. In addition, due to the protective effect of the TiO2 shell on CeCoOx , CeCoOx @Nb2 O5 @TiO2 catalysts exhibited outstanding thermal and hydrothermal stability for 20 hours. The T90 of CeCoOx @Nb2 O5 @TiO2 was slightly lower than that of CeCoOx @Nb2 O5 , but it had higher stability and hydrothermal stability. Furthermore, possible reaction pathways involving the Mars-van-Krevelen (MvK) and Langmuir-Hinshelwood (L-H) models were deduced based on studies of the temperature-programmed desorption of O2 (O2 -TPD), X-ray photoelectron spectroscopy (XPS), and in situ diffuse reflectance FTIR spectroscopy (DRIFTS) characterization.

Low-temperature plasma surface modification technology can help optimize the physical and chemical properties of materials. In this study, TiO 2 films with thicknesses of approximately 100, 200, and 300 nm are prepared on an electrode surface using the magnetron sputtering method to explore the effect of film thickness on the breakdown characteristics of the liquid dielectric. The breakdown voltage of the liquid dielectric under a non-uniform electric field is determined using the Weibull distribution method. Based on the Kerr electro-optical effect, the changes in the spatial electric field along the symmetrical line of the blade-plate electrode gap are measured. The results show that compared to the undeposited state, the positive breakdown voltage of the liquid dielectric increases by 8.0%, 13.4%, and 15.9% corresponding to film thicknesses of 100, 200, and 300 nm, respectively, whereas the negative breakdown voltage increases by only 2.3%, 4.4%, and 5.7%. The TiO 2 film on the electrode surface has a greater impact on the increase in the breakdown voltage of the positive polarity, resulting in a decrease in the difference between the breakdown voltage of the positive and negative polarity. Therefore, it has great potential in improving the insulation performance of liquid dielectrics under uneven electric fields.

In this work, 100, 200, and 400 nm SiO 2 films are deposited on the electrode surface by magnetron sputtering, and the effect of film thickness on the insulation performance of propylene carbonate is studied. We use the Weibull distribution to calculate the breakdown voltage of propylene carbonate under different conditions. Space charge distribution of the liquid is measured based on the Kerr effect. Test results show that the breakdown voltage of propylene carbonate increases from 8.4 to 18.7% with increasing film thickness compared with the case where the SiO 2 film is not deposited. Bipolar injection mode of space charge is not affected by the increase of SiO 2 film thickness, but the amount of space charge injection is significantly reduced. The thicker the SiO 2 film deposited on the electrode surface, the higher the ratio of increasing the breakdown voltage of propylene carbonate, but the smaller the magnitude of the increase.

In this paper, a simple method to enhance the H2O resistance of Ru/TiCeOx catalysts for o-DCB catalytic combustion by constructing superhydrophobic coating of phenyltriethoxysilane (PhTES) was proposed. The effect of PhTES content on the pore structure, specific surface area, H2O resistance, contact angle (CA) value, and catalytic activity of the catalyst was studied. When water was added, the pristine Ru/TiCeOx catalytic activity decreased by about 26%, while the Ru/TiCeOx-16Ph activity hardly decreased. According to the analysis results of XRD, FT-IR, SEM, and CA, PhTES was closely coated on the surface of Ru/TiCeOx to produce a more hydrophobic surface. The Ru/TiCeOx-16Ph catalyst had strong hydrophobicity, and the contact angle was 159.8°, which not only significantly enhanced the water resistance and self-cleaning activity but also showed a good elimination temperature (T90 = 341 °C) for the o-DCB. The enhanced water resistance of Ru/TiCeOx-XPh catalysts resulted from the reduction of the active centers consumed (water occupying oxygen vacancy sites). The reaction mechanism of the Ru/TiCeOx-16Ph catalyst based on surface oxygen species and the Deacon reaction was proposed. This method provided new idea for the design of a new water-resistant composite catalyst and promoted the practical application of the composite catalyst in the catalytic oxidation of o-DCB.

Liquid dielectrics are widely used in high-voltage transformers owing to their excellent insulation properties. Space charge injected from electrodes can damage power systems. It is believed that space charge dynamics are related to the electrodes surface closely. In this study, surface modifications of copper and stainless-steel electrodes deposited by SiO2 and TiO2 nanostructured films with radio frequency magnetron sputtering were investigated. The films were characterized. The effects of the films on the breakdown voltage and space charge dynamics characteristics of the propylene carbonate were studied. These results indicate that when a TiO2 nanostructured film was deposited on the stainless-steel electrode, the breakdown voltage of the propylene carbonate increased by 7.3%, and when SiO2 and TiO2 films were deposited on the copper electrode, the increases were 7.4% and 10.2%, respectively. Furthermore, the amount of charge injection of the stainless-steel electrode was lower than that of the copper electrode, and the nanostructured films markedly suppressed the space charge. Both the TiO2 and SiO2 nanostructured films sputtered on the electrode surface changed the barrier height of the solid–liquid interface and reduced the depth and amount of charge injection. Compared with a sputtered SiO2 film, the TiO2 film had a better space charge suppression effect.

Insulating and energy-storage materials, such as propylene carbonate, require high dielectric strength. To improve insulation performance of propylene carbonate, we surface treated a copper electrode with a low-temperature plasma based on liquid nanometer modification technology. Thus, a TiO 2 nano-modified liquid was prepared and the surface of the copper electrode was modified by sputtering a TiO 2 film. The surface morphologies of the electrode surface before and after modification and the impulse breakdown voltages and space charge distributions of pure and nano-modified propylene carbonate were studied. These results indicate that the TiO 2 film deposition on the surface of the copper electrode markedly reduced the surface roughness. Furthermore, after the surface modification, the breakdown voltage of pure propylene carbonate and nano-modified propylene carbonate increased by 9.4 and 14.3%, respectively. We analyzed the effects of the electrode surface modification and nanoparticles on the breakdown voltage of propylene carbonate from the perspective of space charge. The nanoparticles introduced shallow traps, which increased the rate of charge dissipation. Furthermore, surface modification of the electrodes inhibited charge injection into the liquid, which affected the generation and development of streamers in the liquid, thereby further improving the breakdown performance of the propylene carbonate.

VR video is increasingly popular due to the recent advances in VR technology and hardware. The bulky size of VR video, however, impose new challenges in its storage and processing. In this paper, we focus on the research problems of VR video representation and objective quality assessment. Distinct from traditional 2D video, a VR video is displayed and represented in a form of spherical surface. For encoding purpose, a VR video frame needs to be projected to a 2D flat plane. Existing projection methods usually lead to much redundancy or significant violation in the correlation of neighbor pixels, which are not encoding friendly or are creating visible edge artifacts. To alleviate these problems, we propose in this paper our Quadrangle Affine Square Projection (QASP). QASP is a novel representation for VR video frames, which can reduce the redundant pixels over the traditional projections. In particular, all the inner pixels in QASP remain connected, i.e. the correlations between neighbors pixels are well maintained, which is a desirable feature for video encoding and edge-artifact-free viewing experience. Besides, we also investigated in predicting the optimal rotation angle for QASP frames for higher encoding efficiency. In addition to VR video representation, we also investigate in this paper accurate objective quality measurement for VR video. The traditional video quality measurements, e.g. PSNR, are not suitable to measure the quality of VR videos since they will take the redundant pixels into account. In this paper, we propose a new quality measurement for VR videos, named as Resized-PSNR (R-PSNR). With R-PSNR, only the “meaningful” pixels are considered for quality measurement while the redundant pixels are discarded. To evaluate QASP and R-PSNR, experiments are conducted based on standard VR video sequences. The experimental results show that the proposed projection method achieves noticeable improvement over traditional methods, and the proposed quality assessment method outperforms the traditional measurements in terms of consistency with subjective evaluation.

Three types of alpine plant species, Carex montis-everestii, Quercus aquifolioides and Stipa capillacea, along an altitudinal gradient of 3005–5025 m on the Tibetan Plateau, were chosen to test the generality of the hypothesis that foliar carbon isotope composition (δ13C) of C3 plants increases significantly with altitude and to determine climate drivers shaping its altitudinal pattern. Temperature and relative humidity showed significantly negative correlations with altitude; however, precipitation and soil water potential remained unchanged with altitude. Foliar δ13C of C. montis-everestii, Q. aquifolioides, S. capillacea alone or combined together did not significantly increase with altitude, which does not support the leading hypothesis of increased foliar δ13C with altitude. There was no difference in foliar δ13C among all three species. Multi-factor correlation analyses showed that temperature, precipitation and relative humidity alone did not affect foliar δ13C of C. montis-everestii and S...

Nanostructured dielectric composite has been considered as a promising manner in improving the flashover performance of oil-paper which has been widely used in power systems. In this paper, plasma-enhanced chemical vapor deposition (PECVD) is used to deposit SiO2 on the ceramic fiber-reinforced insulating paper. Scanning electron microscope images show a large number of SiO2 nanoparticles with diameters of 100 nm–250 nm uniformly attached to the fiber surface after the plasma deposition. The surface flashover voltage of the insulating paper was tested in the air and the transformer oil, respectively. Results show that the corresponding DC surface flashover voltages increased by 15.1% in the air and breakdown between liquid and solid interface increased by 24.6% after the PECVD. It is believed that nanoparticles constructed in ceramic fibers change the electron injection barrier which inhibits the injection of negative charges and hinders the accumulation of charges in the dielectric. Nanoparticles can capture electric charges formed in the transformer oil which affects the generation and development of streamers, resulting in an increased dielectric strength. This study provides a new method to comprehensively improve the surface insulating property which has the prospect of promoting other dielectric materials.

Ordered mesoporous TiO2–ZrO2 materials were prepared by evaporation-induced self-assembly (EISA). The CeSn/TizZr10-zOx catalysts were prepared by impregnation method, and its catalytic performance was evaluated for the removal of 1,2-dichlorobenzene (o-DCB). The structure and properties of CeSn/TizZr10-zOx were characterized by N2 adsorption-desorption, XRD, Raman, SEM, TEM, XPS and temperature programmed techniques. The results showed that Ce and Sn oxides were highly dispersed on TiO2–ZrO2 surface. Ti–Zr mixed oxides not only contributed to the formation of ordered mesopores, but also to the formation of strong acid sites. When the molar ratio of Ti/Zr was 6:4, the catalyst exhibited the excellent catalytic activity and outstanding stability and repeatability for the o-DCB elimination reaction because of its superior chlorine resistance. Furthermore, the reaction mechanism of o-DCB catalytic oxidation reduction was proposed based on surface lattice oxygen.

Nanoscale surface-engineering plays an important role in improving the performance of battery electrodes. Nb2 O5 is one typical model anode material with promising high-rate lithium storage. However, its modest reaction kinetics and low electrical conductivity obstruct the efficient storage of larger ions of sodium or potassium. In this work, partially surface-amorphized and defect-rich black niobium oxide@graphene (black Nb2 O5-x @rGO) nanosheets are designed to overcome the above Na/K storage problems. The black Nb2 O5-x @rGO nanosheets electrodes deliver a high-rate Na and K storage capacity (123 and 73 mAh g-1 , respectively at 3 A g-1 ) with long-term cycling stability. Besides, both Na-ion and K-ion full batteries based on black Nb2 O5-x @rGO nanosheets anodes and vanadate-based cathodes (Na0.33 V2 O5 and K0.5 V2 O5 for Na-ion and K-ion full batteries, respectively) demonstrate promising rate and cycling performance. Notably, the K-ion full battery delivers higher energy and power densities (172 Wh Kg-1 and 430 W Kg-1 ), comparable to those reported in state-of-the-art K-ion full batteries, accompanying with a capacity retention of ≈81.3% over 270 cycles. This result on Na-/K-ion batteries may pave the way to next-generation post-lithium batteries.

Inspired by the dynamic gait adopted by gecko, we had put forward GPL (Gecko-inspired mechanism with a Pendular waist and Linear legs) model with one passive waist and four active linear legs. To further develop dynamic gait and reduce energy consumption of climbing robot based on the GPL model, the gait design and trajectory planning are addressed in this paper. According to kinematics and dynamics of GPL, the trot gait and continuity analysis are executed. The effects of structural parameters on the supporting forces are analyzed. Moreover, the trajectory of the waist is optimized based on system energy consumption. Finally, a bioinspired robot is developed and the prototype experiment results show that the larger body length ratio, a certain elasticity of the waist joint, and the optimized trajectory contribute to a decrease in the supporting forces and reduction in system energy consumption, especially negative forces on supporting feet. Further, the results in our experiments partly explain the reasonability of quadruped reptile’s kinesiology during dynamic gait.

SUMMARYThis paper proposes a modular caterpillar climbing robot using spines as the attaching tools. To improve the reliability of the spines' engagement and disengagement, this paper discusses the reasonable trajectory of the spine and designs a driving mechanism of the spine based on the compliant mechanism theory. Then some compliant modules are designed and realized to build the caterpillar climbing robot. A climbing gait is designed to avoid collisions between the spines and the wall, and allows the robot to climb on a stucco-like wall with a 72○ incline. The real tests reveal that the deformation of the compliant toes reduces the sliding forces between the spines and the wall, and improve the climbing action obviously.

Electrodes are damaged by external forces, mechanical wear, and electrochemical corrosion during long-term operation in power systems, resulting in rough electrode surfaces. Space charge injected into the liquid by a rough electrode under a strong electric field causes electric field distortion and leads to breakdown. Moreover, the charge injection is associated with the energy barrier at the electrode-liquid interface. The combined effect mechanism of nanoparticles and electrode surface condition on the insulating characteristics of transformer oil was investigated using various surface condition aluminum plate electrodes. The breakdown voltages and space charge patterns in pure transformer oil and Al2O3 nano-modified transformer oil under impulse voltage were measured in this study through Kerr electro-optic field mapping measurement. The test results indicate that the breakdown voltage of nano-modified transformer oil depends on voltage polarity and electrode surface conditions and the charge injection shows the same mode in pure transformer oil using different surface condition electrodes, but the magnitude of charge injection differs considerably. Due to nanoparticle’s ability of shielding space charges of different polarities and the charge injection of different surface condition electrodes, they have different effects on the breakdown process of transformer oil between different surface condition electrodes. An interfacial model was formed to explore the mechanism of the effect of nanoparticles and electrode surface conditions on the insulation performance of liquid dielectrics and analyze the breakdown process using the space charge injection behaviors.