182 research outputs found

    Non-Darcy flow characteristics of water as influenced by clay concentration

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    The flow of water through saturated samples of montmorillonite and kaolinite was studied to help clarify the existence and nature of non-Darcian flow. No threshold gradients were found in any of the samples studied. Non-Darcy flow was found in 9, 30 and 40 weight percent montmorillonite samples but not in a 50 weight percent montmorillonite or in kaolinite samples. The possible causes of the non-Darcian flow are discussed. A refined technique using a pressure transducer was developed to measure hydraulic conductivities. The hydraulic conductivities of several types of samples under varying conditions were measured. Transport equations for convective diffusion in porous media were derived and tested for capillaries, porous diaphragms, sand columns and clay plugs.U.S. Department of the InteriorU.S. Geological SurveyOpe

    Classical versus quantum dynamics for a driven relativistic oscillator

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    We compare the time evolution of the quantum-mechanical spatial probability density obtained by solving the time-dependent Dirac equation with its classical counterpart obtained from the relativistic Liouville equation for the phase-space density in a regime in which the dynamics is essentially relativistic. For a resonantly driven one-dimensional harmonic oscillator, the simplest nontrivial model system to perform this comparison, we find that, despite the nonlinearity induced by relativity, the classical ensemble description matches the quantum evolution remarkably well

    Determination of rocket engine noise damage to community dwellings near launch sites, volume 1 final report

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    Determination of rocket engine noise damage thresholds of community dwellings near John F. Kennedy Space Cente

    Custom rates and machine rental rates used on Illinois farms, 1966

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    Chiefly tables.Cover title

    Cyclic voltammetry : a tool to quantify 2,4,6-trichloroanisole in aqueous samples from cork planks boiling industrial process

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    Chloroanisoles, namely 2,4,6-trichloroanisole, are pointed out as the primary responsible of the development of musty off-flavours in bottled wine, due to their migration from cork stoppers, which results in huge economical losses for wine industry. A prevention step is the detection of these compounds in cork planks before stoppers are produced. Mass spectrometry gas chromatography is the reference method used although it is far beyond economical possibilities of the majority of cork stoppers producers. In this work, a portable cyclic voltammetry approach was used to detect 2,4,6-trichloroanisole extracted from natural cork planks to the aqueous phase during the cork boiling industrial treatment process. Analyses were carried out under ambient conditions, in less than 15 min with a low use of solvent and without any sample pre-treatment. The proposed technique had detection (0.31±0.01 ng/L) and quantification (0.95±0.05 ng/L) limits lower than the human threshold detection level. For blank solutions, without 2,4,6-trichloroanisole addition, a concentration in the order of the quantification limit was estimated (1.0±0.2 ng/L), which confirms the satisfactory performance of the proposed methodology. For aqueous samples from the industrial cork planks boiling procedure, intra-day repeatabilities were lower than 3%, respectively. Also, 2,4,6-trichloroanisole contents in the aqueous samples determined by this novel approach were in good agreement with those obtained by GC-MS (correlation coefficient equal to 0.98), confirming the satisfactory accuracy of the proposed methodology. So, since this novel approach is a fast, low-cost, portable and user-friendly method, it can be an alternative and helpful tool for in-situ industrial applications, allowing accurate detection of releasable 2,4,6-trichloroanisole in an earlier phase of cork stoppers production, which may allow implementing more effective cork treatments to reduce or avoid future 2,4,6-trichloroanisole contaminations of wine.This work was partially supported by project PEst-C/EQB/LA0020/2011, financed by FEDER through COMPETE - Programa Operacional Factores de Competitividade and by FCT - Fundacao para a Ciencia e a Tecnologia (Portugal)

    Self-regulation: differences by year and area in college students

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    Neste estudo procura-se analisar a existência de diferenças nas estratégias auto-regulatórias de alunos universitários em áreas de formação distintas. Participaram 518 alunos de três níveis (inicial, intermédio e final) das áreas de ciências e humanidades. Aplicou-se a escala “CHE – Comportamentos e hábitos de estudo e aprendizagem”, que avalia cinco dimensões: estratégias cognitivas de transformação e manipulação da informação, organização e planeamento de rotinas, gestão e monitorização, aquisição e selecção da informação, e reforço motivacional. Verificou-se uma maior utilização das estratégias cognitivas e metacognitivas de gestão e monitorização apesar dos resultados não indicarem diferenças substantivas entre os alunos diferenciados por nível e área. Os resultados podem indicar estabilidade nos comportamentos ou limitações no tipo de instrumento e amostra utilizada. O estudo de mudanças nestas estratégias deverá ser conduzido com recurso a delineamentos longitudinais. O impacto da estabilidade deverá ser ponderado na elaboração de projectos de intervenção.In this study we seek to analyze the existence of differences in self-regulating strategies of university students in distinct graduation areas. 518 students of three levels (initial, intermediate and final) of science and humanities fields participated. We used the scale “Behavior and study skill”, which evaluates five dimensions: cognitive strategies of transformation and manipulation of information, organization and planning of routines, management and monitoring, information acquisition and selection, and motivational reinforcement. A higher use of cognitive and metacognitive strategies of management and monitoring was noted although the results do not indicate major differences between students in different levels and graduation areas. The results can indicate stability in the behaviors or limitations in the type of instrument and in the sample used. The study of changes in these strategies must be carried out having in mind longitudinal outlines. The impact of the stability should be taken into account while elaborating intervention projects.(undefined
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