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Beauvais Frederick; Chavez Ernest L.; Oetting Eugene R.; Deffenbacher Jerry L.; Cornell Greg R. 《Canadian Metallurgical Quarterly》1996,43(3):292
Problem-prone behaviors of White American, Mexican American, and American Indian high school dropouts, students in good academic standing, and students in poor academic standing were surveyed. Generally, dropouts were most involved with drugs, perpetration of violence, and victimization by violence, students in poor standing were the next most involved, and students in good standing were least involved. Ethnicity did not interact with academic status, suggesting that differences between dropouts and students were similar across ethnic groups. Some ethnicity and gender main effects were found. Findings were related to R. Jessor's (see record 1992-23064-001) theory of problem-prone behaviors, to peer cluster theory, and to intervention design. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
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Backward priming was investigated under conditions similar to those used in lexical ambiguity research. Ss received prime-target word pairs that were associated either unidirectionally (BABY-STORK) or bidirectionally (BABY-CRY). In Exp 1, targets were presented 500 ms following the onset of visual primes, and Ss made naming or lexical decision responses to the targets. Forward priming was obtained in all conditions, while backward priming occurred only with lexical decision. In Exp 2, primes were presented auditorily, either in isolation or in a sentence. Targets followed the offset of the primes either immediately or after 200 ms. Backward priming occurred with both response tasks, but only when the prime was an isolated word. Backward priming decreased over time with the naming task, but not with lexical decision. These results suggest that the locus of the backward priming effect is different for the 2 response tasks. Results support a context-independent view of lexical access. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
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The supply and return piping of passive solar domestic hot water systems (SDHWS) is typically exposed to ambient weather conditions, and damaging pipe freeze is a major concern. This paper presents a pipe-freeze model that accounts for hot water draws and uses 30 years of actual weather data. The simulation results are cast in terms of pipe-freeze probabilities. Using contour maps of the continental United States, the pipe-freeze probabilities for residential, commercial, and seasonal passive SDHWS are presented for various pipe and insulation geometries. 相似文献
6.
Bray James H.; Adams Gerald J.; Getz J. Greg; McQueen Amy 《Canadian Metallurgical Quarterly》2003,71(3):553
The study used latent growth modeling to investigate longitudinal relationships between individuation, peer alcohol use, and adolescent alcohol use among African American, Mexican American, and non-Hispanic White adolescents (N=6,048) from 7th, 8th, and 9th grades over a 3-year period. Initial levels of peer alcohol use were significantly related to changes in adolescents' alcohol use, whereas initial adolescent alcohol use also significantly related to changes in peers' alcohol use, suggesting a bidirectional relationship. Higher levels of intergenerational individuation were related to smaller increases in adolescent alcohol use and higher levels of separation were related to larger increases in youth drinking. The findings were similar across ethnic groups. Implications for development of prevention and intervention programs are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
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The use and impacts of accelerated weathering of limestone (AWL; reaction: CO2+H2O+CaCO3→Ca2++2(HCO3−) is explored as a CO2 capture and sequestration method. It is shown that significant limestone resources are relatively close to a majority of CO2-emitting power plants along the coastal US, a favored siting location for AWL. Waste fines, representing more than 20% of current US crushed limestone production (>109 tonnes/yr), could provide an inexpensive or free source of AWL carbonate. With limestone transportation then as the dominant cost variable, CO2 mitigation costs of $3-$4/tonne appear to be possible in certain locations. Perhaps 10–20% of US point–source CO2 emissions could be mitigated in this fashion. It is experimentally shown that CO2 sequestration rates of 10−6 to 10−5 moles/sec per m2 of limestone surface area are achievable, with reaction densities on the order of 10−2 tonnes CO2 m−3day−1, highly dependent on limestone particle size, solution turbulence and flow, and CO2 concentration. Modeling shows that AWL would allow carbon storage in the ocean with significantly reduced impacts to seawater pH relative to direct CO2 disposal into the atmosphere or sea. The addition of AWL-derived alkalinity to the ocean may itself be beneficial for marine biota. 相似文献
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Hydrophobically modified alkali-soluble emulsion (HASE) polymers are an important class of rheology modifiers for waterborne
coatings applications. They are typically prepared as terpolymers by emulsion polymerization of ethyl acrylate (EA), methacrylic
acid (MAA), and an associative macromonomer. The viscosity development and shear responses of HASE solutions depend on a number
of factors. This article presents rheological data reflecting the impacts of three key variables: hydrophobe size, acid content,
and molecular weight, on model HASE thickening and rheological performance. The relative contributions of hydrophobic association,
chain expansion, and polymer chain length are discussed.
In steady shear flow, all thickener solutions approached some constant low-shear viscosity at small deformation rates. At
the same molar composition, larger hydrophobe size resulted in higher viscosity development and greater shear thinning behavior.
The amount of acid monomer in HASE polymers can influence the balance between hydrophobic attraction and electrostatic repulsion
forces. It was found that a minimum of 15 wt% MAA was required to effect dissolution and thickening of the model HASE polymers.
Increasing the MAA level yielded higher zero-shear viscosity and storage modulus G’ with maximal values being obtained at
40% MAA.
The molecular weight of the model thickeners was controlled by the amount of chain transfer agent (CTA) added during polymerization.
When the CTA level was below 0.1 wt% based on total monomers, the polymer solutions displayed shear-thinning behavior. A small
increase in CTA concentration beyond 0.1% resulted in a dramatic change to Newtonian flow, and the solution viscosity was
nearly two orders of magnitude lower.
The model thickeners were also tested in a vinyl acrylic architectural paint formulation. The effects of each individual factor
on paint thickener efficiency, high-shear, and low-shear properties are discussed and compared with solution rheology for
predictive relationships.
Presented at the 81st Annual Meeting of the Federation of Societies for Coatings Technology, November 11–12, 2003, in Philadelphia,
PA. 相似文献
10.
Greg R. Leist 《臭氧:科学与工程》1992,14(6):501-516
The treatment chemical ozone has now been successfully used in the United States in municipal water and wastewater plants for many years. To insure continuous, successful operations of these applications, operating obstacles had to be dealt with and overcome.
In this paper, examples of field operating problems and their solutions are described. The experiences at specific municipal water and wastewater installations are reviewed in detail. Discussed for each example are : the background and effects of the problem, the problem-solving process, and the eventual resolution of the problem. The examples include simple unit operations to entire processes.
By observing the ozone installation's operation several years after start-up, the design of future ozone systems can be improved and operating problems minimized. 相似文献