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Food metabolism is one of the basic processes of urban metabolism. Continuously growing urban population drives sharply increasing food demand with related impacts. Aimed at providing adequate information about dynamic process of urban food metabolism and related environmental footprint to identify measures for future diet optimization and impact reduction, this study systematically analyzed the dynamic characteristics of urban food metabolism on metabolic flux, structure and efficiency during 1978- 2015 based on a case study of Beijing. Life cycle assessment (LCA) approach was used to calculate water-carbon footprint caused by food consumption, and an eco-efficiency index E was constructed to evaluate the efficiency of food metabolism in Beijing. At last, this study explored several effective ways to optimize urban food metabolism. The results indicated that: 1) In 2015, the urban food metabolic flux was 881.4×104 t in Beijing, which increased 3.3 times compared with the one in 1978, while water footprint and carbon footprint increased 6.1 times and 4.4 times respectively. 2) The structure of both metabolic flux and environmental footprint presented the evolution characteristics of shifting from staple food as main food to non-staple food as main food and from plant-derived food dominated diet to diet with equal importance of plant- derived food and animal- derived food. 3) The over-consumption diets, especially high proportion of meat consumption, not only affected the health status of urban inhabitants in Beijing, but also pushed tempestuously per capita environmental footprint of urban inhabitants into a high level, resulting in the eco-efficiency’s decreasing from 1.27 to 0.32. 4) Alleviating the environmental footprint impacts of urban food metabolism should be based on the following aspects: optimizing the industrial supply chain; sparkplugging healthy diet habits and sustainable consumption patterns. [ABSTRACT FROM AUTHOR]

The wettability and spreadability of weld beads have significant influences on the forming accuracy of spare parts of armored equipments by welding rapid forming technology. The wettability and spreadability was characterized by the weld bead reinforcement, weld width and wetting angle. Effects of contents of FeSi45 and FeS in flux-cored components on wettability and spreadability for weld beads were researched by single weld bead. The transition mode of weld droplets was investigated by high velocity camera. The results indicate that the weld beads have better wettability and spreadability when the quality percent contents of FeSi45 and FeS in flux-cored components are 11.21% and 0.2% than other conditions. Under welding conditions with small current, the transition mode of weld droplets keeps big droplet without converting for the addition of FeSi45 and FeS. The transition process is steady, and there are no visible spatters. The superior enthalpy of droplets is important reason, for the good wettability and spreadability of weld beads. [ABSTRACT FROM AUTHOR]

Relationship between the rotor iron loss equivalent resistor and slip can be derived through analysis of iron loss of induction motor. From the relationship between the proportion of rotor iron loss as to total iron loss and the electrical angular frequency of the flux, it is shown that the effect of rotor iron loss on the efficiency of induction motor is distinct at low speed. Taking the rotor iron loss into account,a loss model of induction motor is set up. The efficiency maximization control condition for induction motor vector control drive at steady state condition is derived using the Lagrange theorem. The experimental results show that the proposed model is accurate within the whole speed range, and the efficiency maximization control condition is valid. [ABSTRACT FROM AUTHOR]