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Under the guidance of the calculation of phase diagrams method, the self-organized Cu alloy/ stainless steel composite powders with a core/shell microstructure were developed based on the gas atomization process, and the formation evolution of self-organized core/shell structure composite powders was modeled by the phase field method. This paper gives a more detailed explanation for the formation of self-organized core/shell structure composite powders from the viewpoints of thermodynamics and kinetics. Such core/shell structure composite powders have good combination of high strength and corrosion resistance ͑Fe-rich phase͒ and high electric and thermal conductivities ͑Cu-rich phase͒ with many potential advanced applications in electronic devices.

We compared sexual and reproductive health (SRH)-related knowledge, attitude and behavior among unmarried rural-urban female migrants in Shanghai coming from different regions of China. A total of 944 unmarried rural-urban female migrants were recruited from three districts of Shanghai. We used an interviewer-administered structured questionnaire to collect information from each participant and a multivariate logistic regression to examine the association between premarital sex and risk factors. We found the rates of premarital sex, pregnancy and abortion among unmarried rural-urban female migrants were 28.2%, 5.2% and 5.0%, respectively. Participants from the east of China were more likely to engage in premarital sex than those from the mid-west (p < 0.001). The analysis showed premarital sex was associated with age, hometown, education, current residential type, knowledge of sexual physiology and safe sex, attitude to SRH and safe sex, and permissive attitude to sex. Unmarried rural-urban female migrants lack SRH related knowledge and the data suggests high levels of occurrence of premarital sex. The results indicate that programs to promote safe sex, especially to those migrants coming from eastern China, should be a priority.

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[1] A one-dimensional kinetic model is constructed to simulate the electron acceleration by inertial Alfven waves. The electrons are divided into cold and hot electrons and treated separately. Cold components are described by the fluid equation and hot ones by the Vlasov equation, both carrying field-aligned currents. Intense variation of Alfven speed has been introduced by inclusion of cold electrons. The model results show that the exponential decrease of the plasma density plays a key role, which leads to the sharp gradient of both Alfven velocity and electron inertial length. When Alfven waves encounter this sharp gradient at lower altitudes, the electrons accelerated by the waves become super-Alfvenic, and the width of burst structures becomes much wider than the electron inertial length. Consequently, the background electrons carry the oppositely field-aligned current due to plasma oscillation. It is demonstrated that the current carried by the electrons exceeding the wavefront is balanced by the reverse current carried by background electrons. This mechanism can be used to reasonably explain observations of the electron bursts accompanied by little net field-aligned current. Furthermore, our simulation indicates another type of Alfven wave reflection due to mirror force and wave-particle interaction.