On the Cooling Rate-Microstructure Relationship in Molten Metal Gas Atomization

Metallurgical and Materials Transactions A - Gas atomization is the most used powder production technique since it provides good control on particles shape, surface oxidation and dimension. It is a...     

电缆与连接器(六)

3．2．7关于绕线器件（电容、变压器、扼流圈等）的问题 对于绕线（感性）器件,需要从三个方面进行考虑：杂散磁场的控制、特性参数随电流和温度的变化以及电阻特性。     

电路EMC设计与元器件的选取(四)

（上接2007年第6期91页） 1．6 快速简便的内部测试有助于有源器件的选择 尽管供应商提供了电子器件的EMC性能参数,但在实际工作环境中的EMC性能通常是无法预知的。在设计部门内部可以采取一些简便快捷的EMC测试方法对功能性电路进行测试,但电路中至少要具有时钟、完整的信号或数据输入／输出功能。有些供应商还可提供用于此类测试的评估板。     

Core–shell adsorbents by electrospun MOF-polymer composites with improved adsorption properties: Theory and experiments

A new class of core–shell adsorbents has been created by electrospun metal–organic framework (MOF) particles embedded in polymer nanofibers, which have provided many unique properties compared to the existing MOF coating technologies. For the first time, we demonstrate the improved adsorption selectivity of CO₂ over N₂ using electrospun polymer/ZIF-8 adsorbents in experiments. Furthermore, an analytical model based on the assumption that the diffusivity in core is 10 times higher than that in shell is developed to describe the theory of improved selectivity for core–shell adsorbents that is validated against a more accurate finite element model developed in COMSOL. Our model shows three regimes including exclusive shell uptake, linear core uptake, and asymptotic core uptake. These regimes are related to material properties and uptake times, which could be used as design criteria to balance core stability, maximum selectivity, and maximum uptake. An advanced HAADF STEM tomography (Movie S1 ) shows that the shell thickness in the case of polymer/ZIF-8 is on the order of 10 nm, allowing the regime of maximum selectivity to be realized. Kinetically limited adsorption tests at 45°C demonstrate that these composite fibers can perform in a regime of selectivity and uptake for the separation of CO₂ and N₂ that is unobtainable by either the MOF or fiber independently, showing a great potential for postcombustion CO₂ capture.     

Association of Perfluorooctanoic Acid (PFOA) and Perfluorooctane Sulfonate (PFOS) with age of puberty among children living near a chemical plant

Animal studies suggest that perfluorocarbons (PFCs) may alter sexual maturation. Relationships of human PFC exposure with puberty are not clear. We conducted a cross-sectional study to investigate whether perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) were associated with indicators of sexual maturation in a 2005-2006 survey of residents with PFOA water contamination from the Mid-Ohio Valley. Participants were 3076 boys and 2931 girls aged 8-18 years. They were classified as having reached puberty based on either hormone levels (total >50 ng/dL and free >5 pg/mL testosterone in boys and estradiol >20 pg/mL in girls) or onset of menarche. We estimated the odds of having reached puberty classified by these criteria and the fitted median age of reaching puberty in relation to serum PFOA and PFOS concentrations measured when puberty status was assigned. For boys, there was a relationship of reduced odds of reached puberty (raised testosterone) with increasing PFOS (delay of 190 days between the highest and lowest quartile). For girls, higher concentrations of PFOA or PFOS were associated with reduced odds of postmenarche (130 and 138 days of delay, respectively). In conclusion, our study showed a later age of puberty in this population correlated with PFC concentrations.     

Symbol synchronization using signal samples and interpolation

A method for symbol synchronization using two unsynchronized signal samples per symbol is presented. Signal values between the sample points are calculated by interpolation and then processed digitally to find a suitable strobe point. The interpolated value at the strobe point is used for data detection or input to an equalizer. Simulations show that low variance timing estimates can be made for pulses with raised-cosine spectra degraded by quadratic delay distortion     

“Interpreting the interest-efficacy association from a RIASEC perspective”: Correction.

Reports an error in "Interpreting the interest–efficacy association from a RIASEC perspective" by Patrick Ian Armstrong and David L. Vogel (Journal of Counseling Psychology, 2009[Jul], Vol 56[3], 392-407). In the article, an incorrect value was reported for the correlation between Artistic and Social occupational interests in Table 1 (p. 400), incorrect values were reported for some of the fit indices presented in Table 2 (p. 402), and incorrect values were reported for the fit indices presented in Table 5 (p. 404). The correct value for the correlation between Artistic and Social occupational interests is r = .44. Attached are the fit indices that are correct for the Structural Equation Models presented in Table 2 and Table 5. (The following abstract of the original article appeared in record 2009-10122-005.) Social cognitive career theory (SCCT) defines self-efficacy as the critical variable that influences the development of career-related beliefs and attitudes, including interest. In comparison, the authors propose that J. L. Holland’s (1997) theory of Realistic, Investigative, Artistic, Social, Enterprising, and Conventional (RIASEC) types can be interpreted as supporting an alternative model in which both interest and self-efficacy are components of an individual’s vocational identity. Meta-analytic research indicates that RIASEC-based measures of interest and self-efficacy are positively correlated, but these results are also interpreted as supporting the distinctness of the two constructs. The present study evaluates links between interest and self-efficacy with occupation- and activity-based measures of interest and self-efficacy. Multidimensional scaling, cluster analysis, and structural equation modeling results suggest that observed correlations between interest and self-efficacy measures can be attributed to shared Holland-type characteristics of the measures. These results support a Holland-based integrated model of individual differences, with both interest and self-efficacy indicators of RIASEC types, thereby raising questions about the ordering of self-efficacy and interest measures in the SCCT model but also highlighting the importance of assessing both constructs in applied settings. (PsycINFO Database Record (c) 2010 APA, all rights reserved)