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Carbon material, because of its high thermal conductivity, ablation resistance and friction resistance, has been widely used in the field of electrical engineering. When confronted strong thermal shock, the interface structure of carbon material would cause thermal shock damage by the rapid temperature difference. In order to systematically and quantificationally study the thermal shock damage of carbon materials, an experimental system that can provide rapid temperature difference was built. The experimental results showed that undergoing a temperature difference of 485 °C, more micro-cracks and holes arose in the pure carbon material, resulting in an increase of porosity by 26.39%, an increase friction coefficient by 48.65%, and a decrease of compressive strength by 23.96%. It was also found the ultrasonic velocity linearly decreased with the increase of porosity and the decrease of the compressive strength caused by thermal shock, which meant the non-destructive ultrasonic testing can be used to conveniently and accurately quantify the thermal shock damage. This conclusion also applies when testing copper-impregnated carbon material, making it a potential method to be used in the maintenance of pantograph which can effectively avoid in rail transit accidents.

As common electric contact materials, copper‐carbon electrode pairs are widely used in the field of electric contact such as in high‐speed railways, motor collector rings and grounding brushes. They play a key role in energy transmission in the above‐mentioned systems. Arc erosion has become a key issue threatening system safety. In this work, a dedicated arc erosion platform was built to study the polarity effect of copper‐carbon electrode pairs. It was found that arc dynamics and electrodes erosion behaviours were significantly different under different polarities, which could be understood from the mechanism of heat transfer, cooling and electron emission of the electrode. Then, when the carbon material was used as an anode, the arc caused carbon transfer: the carbon material sublimated quickly due to electron condensation and thermal conduction and quickly condensed on the low‐temperature metal electrode, while the carbon material transfer could partly inhibit the oxidation of the cathode metal electrode. In addition, the rapid sublimation of the carbon material produced high‐temperature airflow, which would make the arc impedance fluctuate and cause the arc voltage to jump. Finally, the anode heat transfer and cathode cooling mechanism directly affected the material state, and the erosion of the anode material was more serious.

Parents are often considered the pivotal stakeholders in Family Language Policy (FLP). However, grandparents are increasingly acting as surrogate parents among multi-generational families around the globe including in dual-career families in Singapore. Analysing family interactions and interviews, this study examines how grandparent's language ideologies contribute to shaping the language ideology, management, and practices of the family, even to the extent of overwriting and becoming the dominant voice in the family's FLP. Our findings show that the grandparents seem to be driving the shift towards English. In addition, the negotiation of FLP within the Singaporean context provides insight into how ideologies and the choice of languages can be deeply intertwined with harmony within the family unit and respect for one's elders. Nanyang Technological University This work was supported by the AcRF Tier 1 Research Project 2019-T1-001-080 (Cavallaro), Nanyang Technological University, Singapore

With the increase of high-speed railway speed and traction power, bouncing separation between pantograph and catenary, and arcs are frequent. The high temperature and high energy of the pantograph arc has become a key factor threatening the safety of the system. In this paper, a combination of experiment and simulation was used to establish a pantograph arc ablation model, and the pantograph arc behavior was regulated by means of an external magnetic field. The study found that the arc produces directional movement under the action of the Lorentz force of the magnetic field, and disperses the energy, which can effectively reduce the ablation of the catenary wire. At the same time, as the strength of the magnetic field increased, the arc motion behavior accelerated, and the degree of electrode erosion was further dispersed. Finally, from the perspective of arc root transfer, the reason for arc energy dispersion was explained. The results of the study provide a reference basis for preventing catenary wire disconnection.

Carbon/Copper (C/Cu) composites have been widely used in aerospace, transportation and military products because of their excellent properties of mechanical strength, self-lubrication and electrical conductivities. One of the challenges in preparing C/Cu composites materials is how to overcome the poor wettability between Cu and carbon. In this study, ultrafine iron oxide (Fe2O3), as a precursor, was introduced into the carbon matrix to improve the C/Cu interfacial bonding of C/Cu composites prepared by pressure infiltration. The effect of Fe on the phase composition, microstructure and properties of C/Cu composites were systematically evaluated. The results revealed that the interfacial bonding between Cu and carbon was enhanced by the “bridge architecture” of iron carbide (Fe3C). The wettability between Cu and carbon improved for the contact angle decreased from 124° to 38°. Compared with the unmodified composites, the composites doping 5 wt% Fe2O3 exhibited best performance. The compression and flexural strength increased by 37.4% and 120.4% respectively. Meanwhile, the electrical conductivity improved by 283.7%. It was concluded that the Fe3C layer had an important effect on the electron transport and crack propagation of the C/Cu composites.

Graphite matrix/copper composites have found significant potential uses in numerous areas. Until now, a high ambient gas pressure has to be applied to overcome the non-wettability between the copper melt and graphite matrix, which has restricted the technological and economic efficiencies, as well as the composite performance. In this paper, we have proposed a pressureless infiltration strategy to realize the preparation of highly conductive graphite matrix/copper composites. A tungsten carbide network is first in situ constructed in the graphite matrix, transforming the capillary force from the resistance mode to the impetus mode. Results show that the contact angle of graphite/copper decreased from 138.5° to 23° due to the constructed tungsten carbide network. The composites exhibit good interfacial bonding, and the electrical conductivity reaches 15.1 × 105 S/m, far higher than the requirement of the industry standard.

The paper mainly introduced the basic principle and method of Object-oriented classification technology and made studies and research on decision tree classification technology. In addition, the remote sensing image was classified with Object- oriented way by using C5.0 algorithm, and compared with the result based on pixels classification and the result of SVM Object-oriented classification, which has improved that the accuracy and effectiveness of decision tree classification can be used in Object-oriented remote sensing image classification.

Airborne radar altimetry sometimes records abnormal phenomenon. In this case, information of real terrain must be incorporated to analyze the abnormality region. This paper applies terrain information of a test area organized by a spatial geographical information system (GIS) to the radar signal analysis. With the support of Global Positioning System (GPS) and Inertial Navigation System (INS), we can simulate the radar altimeter data by organizing and analyzing three-dimensional terrain information inside of the radar beam.