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排序方式: 共有193条查询结果,搜索用时 62 毫秒
51.
LB Becker RA Berg PE Pepe AH Idris TP Aufderheide TA Barnes SJ Stratton NC Chandra 《Canadian Metallurgical Quarterly》1997,30(5):654-666
There is growing recognition that race and socioeconomic variables in health research demand greater attention. The investigators compared racial differences in health definition, health value, and health-promoting behavior of 62 pairs (N = 124) of Black and White college women matched on age, body mass index, and socioeconomic status. Both groups of women had similar definitions of health, valued health to the same extent, and reported similar levels of self-actualization, health responsibility, exercise, and stress management. Black women, relative to White women, practiced fewer nutrition behaviors and had less interpersonal support. Interventions to reduce health risk associated with nutrition practices of Black women are warranted and further research is needed to explore the influence of the social structure of educational institutions on interpersonal relationships and other health behaviors. When socioeconomic status is taken into consideration, Black and White college women demonstrated more commonalities in health behavior than differences. 相似文献
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The larger pore LaY zeolite catalyst resembles homogeneous metal chloride and heterogeneous silica-alumina acid catalysts since the results are consistent with isomerization being a series of intramolecular 1,2 shifts. On the other hand, isomerization with the smaller pore zeolite, ZSM-5, is very different and the relative rate constants appear to be influenced by diffusion and/or shape selectivity. Disproportionation is a significant reaction with LaY but not with ZSM-5 in the temperature range used for the present study. The small amount of trimethylbenzene formed at low conversions using ZSM-5 is 1,2,4-trimethylbenzene, also providing evidence of shape selectivity influencing the reaction products. 相似文献
55.
SJ Moorhouse N Vranješ A Jupe M Drakopoulos D O'Hare 《The Review of scientific instruments》2012,83(8):084101
A versatile, infrared-heated, chemical reaction cell has been assembled and commissioned for the in situ study of a range of chemical syntheses using time-resolved energy-dispersive X-ray diffraction (EDXRD) on Beamline I12 at the Diamond Light Source. Specialized reactor configurations have been constructed to enable in situ EDXRD investigation of samples under non-ambient conditions. Chemical reactions can be studied using a range of sample vessels such as alumina crucibles, steel hydrothermal autoclaves, and glassy carbon tubes, at temperatures up to 1200 °C. 相似文献
56.
Battaglia DJ Shafer MW Unterberg EA Bell RE Hillis DL LeBlanc BP Maingi R Sabbagh S Stratton BC 《The Review of scientific instruments》2010,81(10):10E533
Tangentially viewing soft x-ray (SXR) cameras are capable of detecting nonaxisymmetric plasma structures in magnetically confined plasmas. They are particularly useful for studying stationary perturbations or phenomenon that occur on a timescale faster than the plasma rotation period. Tangential SXR camera diagnostics are planned for the DIII-D and NSTX tokamaks to elucidate the static edge magnetic structure during the application of 3D perturbations. To support the design of the proposed diagnostics, a synthetic diagnostic model was developed using the CHIANTI database to estimate the SXR emission. The model is shown to be in good agreement with the measurements from an existing tangential SXR camera diagnostic on NSTX. 相似文献
57.
The concept of wireless sensor networks conjures up images of a world of ubiquitous sensing, but it requires a massive increase in the number of sensors available. Although there has been considerable activity in transducer-based 'sensor nets', there have been virtually no corresponding deployments of chemical- or biological-sensing networks - considerable advances in materials science are needed before these can be used on a large scale. 相似文献
58.
The effect of some heat treatment parameters on the dimensional stability of AISI D2 总被引:1,自引:0,他引:1
The tool steel AISI D2 is usually processed by vacuum hardening followed by multiple tempering cycles. It has been suggested that a deep cold treatment in between the hardening and tempering processes could reduce processing time and improve the final properties and dimensional stability. Hardened blocks were then subjected to various combinations of single and multiple tempering steps (520 and 540 °C) and deep cold treatments (−90, −120 and −150 °C). The greatest dimensional stability was achieved by deep cold treatments at the lowest temperature used and was independent of the deep cold treatment time. 相似文献
59.
Paul Stratton 《Journal of Materials Engineering and Performance》2010,19(5):623-626
Aluminum extrusion dies are usually made from H13 steel that is ferritically nitrocarburized to minimize wear and pick-up.
Before being placed in the extrusion press, the dies are preheated to minimize thermal shock at the start of the extrusion
cycle. During the preheating time, the nitrocarburized layer oxidizes. Some of this layer can break away during extrusion
leaving marks on the product. Although inerting the preheat furnaces with nitrogen has been found to reduce the oxidation,
it does not solve the problem completely. Experiments have shown that a small addition of ammonia to the preheating protective
atmosphere could eliminate oxidation and prevent nitrogen loss from the surface nitride layer. 相似文献
60.
Layered‐Double‐Hydroxide Nanosheets as Efficient Visible‐Light‐Driven Photocatalysts for Dinitrogen Fixation 下载免费PDF全文
Yufei Zhao Yunxuan Zhao Geoffrey I. N. Waterhouse Lirong Zheng Xingzong Cao Fei Teng Li‐Zhu Wu Chen‐Ho Tung Dermot O'Hare Tierui Zhang 《Advanced materials (Deerfield Beach, Fla.)》2017,29(42)
Semiconductor photocatalysis attracts widespread interest in water splitting, CO2 reduction, and N2 fixation. N2 reduction to NH3 is essential to the chemical industry and to the Earth's nitrogen cycle. Industrially, NH3 is synthesized by the Haber–Bosch process under extreme conditions (400–500 °C, 200–250 bar), stimulating research into the development of sustainable technologies for NH3 production. Herein, this study demonstrates that ultrathin layered‐double‐hydroxide (LDH) photocatalysts, in particular CuCr‐LDH nanosheets, possess remarkable photocatalytic activity for the photoreduction of N2 to NH3 in water at 25 °C under visible‐light irradiation. The excellent activity can be attributed to the severely distorted structure and compressive strain in the LDH nanosheets, which significantly enhances N2 chemisorption and thereby promotes NH3 formation. 相似文献