A field campaign was conducted to measure and analyze 13 polycyclic aromatic hydrocarbons (PAHs) in six major zones in the city of Shanghai, P.R. China from August 2006 to April 2007. Ambient air samples were collected seasonally using passive air samplers, and gas chromatography-mass spectroscopy was used in this field campaign. The results showed that there was a sequence of 13 PAHs at Phen > FA > Pyr > Chr > Fl > An > BaA > BbFA > BghiP > IcdP > BkFA > BaP > DahA and the sum of these PAHs is 36.01 +/- 10.85 ng/m(3) in gas phase. FL, Phen, FA, Pyr, and Chr were the dominant PAHs in gas phase in the city. They contributed 90% of total PAHs in the gas phase. Proportion of measured PAHs with three, four, five, and six rings to total PAHs was 53%, 42%, 3%, and 2%, respectively. The highest concentration of SigmaPAHs (the sum of 13 PAHs) occurred in the wintertime and the lowest was in the summer. This investigation suggested that traffic, wood combustion, and metal scrap burn emissions were dominant sources of the concentrations of PAHs in six city zones compared with coal burning and industry emissions. Further, the traffic emission sources of PAHs in the city were attributed mostly to gasoline-powered vehicles compared with diesel-powered vehicles. It was revealed that the seasonal changes in PAHs in the city depended on different source types. Metal scrap burn was found to be the major source of PAHs during the autumn, while the PAH levels in the atmosphere for winter and spring seasons were mainly influenced by wood and biomass combustion. Comparisons of PAHs among different city zones and with several other cities worldwide were also made and discussed.

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Ampere force and Lorentz force are two different definitions in the field of electromagnetism. Some teaching materials have been confused by the relations and differences of the tow definitions. Generally speaking, Ampere force is not the resultant of Lorentz force which all the free electrons have in the carrier wire, either in numerical value or orientation. Acting in numerical value, Ampere force equals the algebra sum of the Lorentz components forces which all the free electrons endured in the (L×B) directions.

During milling of thin-walled components, obtaining minimum distortion is essential in order to achieve production goals. In this study, a mechanical model based on deformation machanism is established, and is help to analyse relationship between residual stress and deformation in component. Researched on simulation and experiment, the stress-deformation characteristics of different component shape is obtained. The results indicate that the deformation of thin-walled component in milling primarily depends on the distribution of initial residual stress, which can generate bending moment and lead to distortion. And then milling stress on the surface is easy to make bending moment baesd on this distortion, and make the deformation of component intensify.