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Teachers' practical knowledge is closely related to teaching practice. The purpose of this research was to develop an instrument for assessing upper-secondary school science teachers' perceived practical knowledge about practical work. The development of this instrument was based on five components in the conceptual framework of PCK about practical work: orientations of practical work, knowledge of curriculum materials in practical work, knowledge of students in practical work, knowledge of educational strategies for practical work, and knowledge of assessment in practical work. After the questionnaire was developed, 636 Chinese upper-secondary school science teachers participated in this research voluntarily. The results from exploratory factor analysis, correlation analysis and confirmatory factor analysis provided sufficient evidence for the construct validity of instrument. The high Cronbach coefficient indicated that the instrument had good internal consistency reliability. Finally, an instrument with six factors and 25 items was documented. The instrument would benefit science teacher educators and researchers.

To explore the friction and wear performance of the valve pair with different wetting combinations under various working conditions in hydraulic oil lubrication, a low surface energy modification method was adopted in this paper to improve the surface wettability of the upper sample composed of SAF2507 and the lower sample composed of CFRPEEK, and to prepare valve plate pairs with different wetting combinations. The MMU-5G friction and wear testing machine was used to investigate its friction and wear characteristics under hydraulic oil lubrication. The results show that the surface free energy of SAF2507 and CFRPEEK decreased significantly after the treatment with a low surface energy solution, and the surface free energy of the upper and lower samples decreased by 41.9% and 42.2%, respectively. The oil contact angle of samples remained lipophilic, but the oil contact angle increased significantly. Under the working condition of low speed (800 r/min), the surface wettability of the valve plate pair has a great influence on its friction and wear characteristics. When operating at high speed (1200 r/min), the surface wettability of the valve plate pair has little influence on its friction and wear characteristics. [ABSTRACT FROM AUTHOR]

In order to control the surface wettability of the port pair and improve the tribological properties, the upper sample super duplex stainless steel SAF2507 and the lower sample carbon fiber reinforced polyetheretherketone (CFR-PEEK) with different wettability were prepared by the low surface energy modification method. Using standard friction and wear testing machine MMD-5A,the friction and wear properties of test specimens with different wetting combinations were studied under three different working media, the pure water, seawater and L-HM46 anti-wear hydraulic oil. The test results show that the low surface energy modification changes the surfaces of SAF2507 and CFRPEEK from hydrophobic to hydro-phobic, and the upper and lower samples are still hydrophilic surfaces, but the oil contact angle increases significantly. The friction coefficient of the same port pair decrease sequentially in oil, seawater, and water media. In water, seawater and oil media, the friction coefficient of the double-modified surface port pair is reduced by 8. 2%,38. 2%, and 24. 4% compared with the double-hydrophilic surface port pair, respectively. The depth of wear scars of the same distribution pair decreases sequentially in water, seawater and oil media. The friction between SAF2507 and CFRPEEK is mainly due to the furrow effect and adhesive wear. The double low surface energy match achieves the effect of friction reduction by reducing the viscous resistance of the lubricating fluid. [ABSTRACT FROM AUTHOR]

Eolian loess deposits contain valuable information about past climate changes and erosion history in dust source regions. In contrast to the extensive investigations of paleoclimatic implications of Eurasian loess, continental erosion information in the loess deposits has received less attention, particularly on the global or hemispheric scales. The present study combines citrate‐bicarbonate‐dithionite (CBD) magnetic mineral extraction procedures and linear regression of magnetic parameters to analyze Eurasian loess. We find that lithogenic susceptibility of Quaternary loess deposits in Central Asia, Europe and the Chinese Loess Plateau shows synchronous long‐term increases since ∼0.6–0.5 Ma, suggesting intensive glacial erosion and/or river incision to have occurred in the surrounding mountains of dust source regions after the mid‐Pleistocene climate Transition. The dramatic increase in lithogenic susceptibility of Eurasian loess provides new insights into the close relationships between global climate changes and dust source erosion since the late Cenozoic. Plain Language Summary: Eolian loess deposits are valuable materials for elucidating the development and mechanisms of dust activities in Eurasia and their links with global climate changes and erosion processes in mountainous areas of dust sources on tectonic and orbital time scales. Continental erosion information retrieved from the Eurasian loess, however, has rarely been reported. A comprehensive analysis of lithogenic magnetic signals in Eurasian loess through mathematical and CBD extraction approaches demonstrates that lithogenic susceptibility of Quaternary loess‐paleosol sequences in Eurasia increased significantly after ∼0.6–0.5 Ma, in coincidence with increasing global ice volume and climatic instability after the mid‐Pleistocene climate Transition (MPT). We suggest that increased ice volume and climate fluctuation amplitudes after the MPT produced vast amounts of fresh Fe‐bearing silicate particles and detrital magnetite in mountainous areas of Eurasia, which can be attributed to a dramatic intensification of glacial erosion and river incision, thereby causing the loess lithogenic susceptibility increase. The results demonstrate that variations in lithogenic magnetic properties of loess deposits can be used to reconstruct the erosional history of main mountains surrounding the dust source regions in Eurasia over geological timescales. Key Points: Lithogenic magnetic susceptibility of Quaternary loess deposits in Eurasia increased synchronously after ∼0.6–0.5 MaGlobal cooling may account for the increase in lithogenic susceptibility of Eurasian loessSpatial variations of lithogenic susceptibility of Eurasian loess are related to varying distances between the source and the sink region [ABSTRACT FROM AUTHOR]