Search results for "mixture"
showing 10 items of 1178 documents
Impact of dust and smoke mixing on column-integrated aerosol properties from observations during a severe wildfire episode over Valencia (Spain)
2017
The most destructive wildfire experienced in Spain since 2004 occurred close to Valencia in summer 2012. A total of 48.500ha were affected by two wildfires, which were mostly active during 29-30 June. The fresh smoke plume was detected at the Burjassot measurement station simultaneously to a severe dust episode. We propose an empirical method to evaluate the dust and smoke mixing and its impact on the microphysical and optical properties. For this, we combine direct-sun measurements with a Cimel CE-318 sun-photometer with an inversion methodology, and the Mie theory to derive the column-integrated size distribution, single scattering albedo (SSA) and asymmetry parameter (g). The mixing of d…
Empirical estimates of the radiative impact of an unusually extreme dust and wildfire episode on the performance of a photovoltaic plant in Western M…
2019
Abstract We have estimated the radiative impact produced by an unusually extreme dust and wildfire episode on the performance of a photovoltaic (PV) plant. The dust and wildfire events were mostly active on 26–28 and 29–30 June 2012, respectively. We took advantage of the consecutiveness of both events to separate and derive empirically the radiative effect of dust and smoke aerosols. With this purpose, we employed measurements of aerosol load, radiation and PV power output from a collocated atmospheric station and PV plant located at Burjassot (Valencia, Spain). The empirical estimates were obtained by direct comparison with a summer background day, happened right before the two consecutiv…
The effect of physical education students' beliefs and values on their physical activity: A growth mixture modelling approach
2013
This study examined the change in adolescents' expectancy-related beliefs and task values towards physical education (PE). In addition, the physical activity (PA) growth trajectories of the identified adolescent subpopulations were examined. This study comprised 812 students (age M = 12.31, range: 11–13), who answered questionnaires four times during Grades 6–9. This study found that expectancy-related beliefs declined, while task values increased across the middle school transition. Adolescents who valued PE highly and experienced an increase in their expectancy-related beliefs became physically more active across time, while adolescents with the lowest levels and the most negative change …
Trajectories of depressive symptoms during emerging adulthood: Antecedents and consequences
2008
In order to examine what kinds of trajectories of depressive symptoms young adults show during emerging adulthood, and their antecedents and consequences, 297 university students completed the revised Beck's depression inventory seven times over a 10-year period, and other measures at the beginning and the end of the study. The growth mixture modelling for depressive symptoms ended up in a 3-group solution: 23% of the participants were typified by a low level of symptoms, 61% showed a moderate level, and 16% fell into the third group with high and increasing levels of depressive symptoms during emerging adulthood. Those on the high-depressive trajectory had a poorer quality of relationships…
The effectiveness of increased support in reading and its relationship to teachers' affect and children's motivation
2016
Abstract The aims of this study were, firstly, to identify different groups of teacher–child dyads on the basis of the longitudinal associations between teachers' individual support in reading and children's reading skills, and, secondly, to examine whether the groups thus identified differ with respect to various teacher- and child-related factors. A total of 372 teacher–child dyads were examined. The reading skills of 6- to 7-year-old Finnish-speaking children were measured at the beginning and end of Grade 1. The amount of teachers' support in reading for a particular child was gathered from teachers by questionnaires. Regression Mixture Modeling identified three latent groups of teacher…
A LASER-INDUCED FLUORESCENCE (LIF) METHOD FOR MONITORING OXYGEN–ALKALI DELIGNIFICATION OF SOFTWOOD KRAFT PULP
2002
ABSTRACT A laser-induced fluorescence (LIF) method for monitoring the oxygen–alkali delignification of pine (Pinus sylvestris) kraft pulp was tested. The fluorescence intensity of the effluent was found to increase systematically during treatment as the lignin content of the pulp decreased. This emission method, compared, for example, to a UV/Vis absorption method, seems to have potential for large-scale applications. Owing both to the complex chemical nature of the effluent from oxygen–alkali delignification and to the complex nature of the fluorescence method, further work on this method is needed before it can be used for industrial purposes.
FTIR Monitoring of Chemical Changes in Softwood During Heating
2000
Abstract A multivariate chemometric method for monitoring the mass loss of Scots pine (Pinus sylvestris) and Norway spruce (Picea abies) by IR spectroscopic determination of chemical changes occurring during the heat treatment (160 - 260 °C, 2 - 8 h) of these wood materials was developed. The method was based on the handling of FTIR data on treated and untreated wood powder samples by the partial least squares (PLS) method. In addition, unknown samples (treated and untreated pine and spruce) were classified into separate groups by the principal component analysis (PCA) method. The chemical changes occurring in the wood samples during heating were also briefly discussed.
Thermochemical behavior of Norway spruce ( Picea abies ) at 180-225 °C
2002
Norway spruce (Picea abies) was heated for 2–8 h in the temperature range 180–225 °C, under a steam atmosphere. The chemical analyses of the treated feedstock samples indicated that during heating (total mass loss 1.5–12.5% of the initial DS) carbohydrates (hemicelluloses and cellulose) were clearly more amenable to various degradation reactions than lignin. In addition, major water-soluble products released from the feedstock material during the treatments were classified into several compound groups and changes in the relative mass portion of these groups were monitored by GC during a separate experiment.
Role of rock fragment cover on runoff generation and sediment yield in tilled vineyards
2017
The soil in conventional Mediterranean vineyards is an active and non-sustainable source of sediment and water. Lack of vegetation cover, small soil organic matter content and intense ploughing result in large rates of erosion in a millennia-old tillage system. There is a need for soil conservation strategies that enable sustainability of wine and grape production; therefore, it is essential to measure the rates and to investigate the processes and factors of soil erosion. This study evaluated factors that can reduce soil losses in traditional Mediterranean vineyards. The investigation was carried out with 96 rainfall simulation experiments at the pedon scale (0.24 m2) to measure soil detac…
Mechanisms for Translocation of Heavy Metals from Soil to Epigeal Mosses
2011
The mechanisms for translocation of heavy metals from soil to epigeal mosses were investigated. The first mechanism was demonstrated for (137)Cs and involved the uplifting of the pollutant-containing dust from the soil, followed by the local secondary deposition on surfaces of epigeal mosses and epiphytic lichens. The second mechanism involved the diffusion of metal cations from the soil through water wetting the moss into the gametophyte. The mechanism was demonstrated by measuring the electric conductance of wetted gametophytes with single ends immersed in solutions of Cu and Na salts. In addition, the concentrations of Cu and Cd were compared in moss samples exposed to the natural soil a…