Wire-arc additive manufacturing (WAAM) has been considered as one of the potential additive-manufacturing technologies to fabricate large components. However, its industrial application is still limited by the existence of stress and distortion. During the process of WAAM, the scanning pattern has an important influence on the temperature field, distortion and final quality of the part. Four kinds of deposition patterns, including sequence, symmetry, in–out and out–in, were designed to deposit H13 steel in this study. An in situ measurement system was set up to record the temperature history and the progress of accumulated distortion of the parts during deposition. An S value was proposed to evaluate the distortion of the substrate. It was shown that the distortion of the part deposited by sequence was significantly larger than those of other parts. The distortion deposited by the out–in pattern decreased by 68.6% compared with sequence. The inherent strain method and strain parameter were introduced to expose the mechanism of distortion reduction caused by pattern variation.

As a promising class of metal-free oxygen reduction reaction (ORR) catalysts, N-doped carbon (NDC) catalysts have attracted widespread attention owing to their high stability, high conductivity, good poison tolerance, and environmental friendliness. We herein report the fabrication of NDC catalysts by using triphenylimidazole-containing polybenzoxazine (TPB) as the precursor. The TPB is firstly Friedel–Crafts cross-linked in CCl ₄ by using anhydrous AlCl ₃ as the catalyst. The cross-linked TPB is then pyrolyzed at 800 °C–1000 °C, giving O-containing NDC catalysts. The as-fabricated NDC-900 catalyst has a particulate morphology together with a high BET surface area (947 m ² g ⁻¹ ) and a highly ORR active N content (3.39 at%). Compared to the commercial Pt/C catalyst, the NDC-900 catalyst exhibits a higher ORR activity in alkaline media as evidenced by the higher onset potential ( E _o , 0.986 vs 0.964 V), higher half-wave potential ( E _1/2 , 0.845 vs 0.815 V), and higher current density at 0.92 V ( J _@0.92 , 0.251 vs 0.141 mA cm ⁻² ). Moreover, the NDC-900-based Zn-air battery achieves a maximum power density of 131.4 mW cm ⁻² at 204.8 mA cm ⁻² and a high specific capacity of 818.4 mAh g ⁻¹ _Zn at 5.0 mA cm ⁻² .

As the facility with the highest utilization rate in the expressway service area, the toilet has the greatest influence on the crowd gathering degree in the expressway service area. In order to study the scale and location of toilets in the Meicun service area, this paper conducts a field survey on the service area of Meicun by means of video recording and crowd tracking questionnaire survey. Through the investigation, the key data such as the probability of customers using toilet and toilet turnover rate were obtained. Based on this, the flow model of the crowd in the high-speed service area is established by using the simulation software of Anylogic. In the simulation, the scale and location of the toilet facilities in the high-speed service area are analyzed and evaluated according to the number of people using the toilet at the same time. The results show the influence of different toilet layout on the efficiency of toilet use and the degree of crowd gathering, and prove that double toilets are more efficient than single toilets, disperse the flow of people, reduce the degree of crowd gathering and avoid crowd crowding.

Baoding city locates on northwestward of the North China Plain, middle section of the Taihang Mountain which is a typical city on groundwater developing in China. Authors summarize the history of groundwater use and contributions of groundwater, analyze environmental geological issues caused by over-exploitation of urban groundwater which are similar with other water-shortage cities. Main environmental geological issues are regional lowing of groundwater table, depression cone of groundwater, land subsidence, land fractures and groundwater pollution. According to exiting issues authors also give some countermeasures on urban groundwater development and utilization.