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Layer Depth (layer + depth)
Selected AbstractsA pyrolysis model of charring materials considering the effect of ambient oxygen concentrationFIRE AND MATERIALS, Issue 7 2007W. G. Weng Abstract In this paper, a one-dimensional integral model is developed to describe the processes involved in the transient pyrolysis of a semi-infinite charring material subjected to a constant radiant heat flux. In this model, a special factor that shows the effect on pyrolysis is considered, i.e. under the oxygen-containing atmosphere. The model tracks the char layer depth, thermal penetration depth, surface temperature and mass loss rate. Comparison with experimental results demonstrates that the predictions of the mass loss rate and temperature profile within the charring material are in good agreement with the experiment. Copyright © 2007 John Wiley & Sons, Ltd. [source] The influence of seasonal climatic parameters on the permafrost thermal regime, West Siberia, RussiaPERMAFROST AND PERIGLACIAL PROCESSES, Issue 1 2009Valeria V. Popova Abstract Statistical correlations between seasonal air temperatures and snow depths and active layer depths and permafrost temperatures were analysed for tundra (Marre-Salle) and northern taiga (Nadym) sites in Western Siberia. Interannual variations in active layer depth in the tundra zone correlated with the average air temperature of the current summer, and in peatland and humid tundra, also with summer temperatures of the preceding 1,2 years. In the northern taiga zone, the active layer depth related to current summer air temperature and to a lesser extent, to spring and/or winter air temperatures. Variations in summer permafrost temperatures at 5,10,m depth were correlated with spring air temperatures in the current and preceding 1,2 years. The weather regime during the preceding 1,2 years, therefore, reinforced or weakened ground temperature variations in a given year. Overall, the most important factors influencing the permafrost regime were spring and summer air temperatures, and in one case snow depth. However, statistical links between meteorological and permafrost parameters varied between the tundra and northern taiga zones and among landscape types within each zone, emphasising the importance of analyses at short temporal scales and for individual terrain units. Copyright © 2009 John Wiley & Sons, Ltd. [source] Damage to DNA in Bacterioplankton: A Model of Damage by Ultraviolet Radiation and its Repair as Influenced by Vertical Mixing ,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 1 2000Yannick Huot ABSTRACT A model of UV-induced DNA damage in oceanic bacterioplankton was developed and tested against previously published and novel measurements of cyclobutane pyrimidine dimers (CPD) in surface layers of the ocean. The model describes the effects of solar irradiance, wind-forced mixing of bacterioplankton and optical properties of the water on net DNA damage in the water column. The biological part includes the induction of CPD by UV radiation and repair of this damage through photoreactivation and excision. The modeled damage is compared with measured variability of CPD in the ocean: diel variation in natural bacterioplankton communities at the surface and in vertical profiles under different wind conditions (net damage as influenced by repair and mixing); in situ incubation of natural assemblages of bacterioplankton (damage and repair, no mixing); and in situ incubation of DNA solutions (no repair, no mixing). The model predictions are generally consistent with the measurements, showing similar patterns with depth, time and wind speed. A sensitivity analysis assesses the effect on net DNA damage of varying ozone thickness, colored dissolved organic matter concentration, chlorophyll concentration, wind speed and mixed layer depth. Ozone thickness and mixed layer depth are the most important factors affecting net DNA damage in the mixed layer. From the model, the total amplification factor (TAF; a relative measure of the increase of damage associated with a decrease in ozone thickness) for net DNA damage in the euphotic zone is 1.7, as compared with 2.1,2.2 for irradiance weighted for damage to DNA at the surface. [source] Stability of bifurcating solutions of the problem about capillary-gravity surface waves in spatial layer of floating fluidPROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2009Artyom N. Andronov In prolongation of our previous investigations on capillary-gravity surface waves in spatial fluid layers the stability of the bifurcating families of solutions in the horizontal layers of the floating (and without flotation) incompressible heavy capillary fluid is considered. The assumption about layer depth simplifies the proof of the existence of bifurcating solutions at the high dimensions of the linearized operator degeneracy, computation of their asymptotics and as the main subject of this communication the investigation of their stability, relative to perturbations with the same symmetry as bifurcating solutions. Group analysis methods of differential equations are used. (© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Characterization of a Multilayer Aquifer Using Open Well Dilution TestsGROUND WATER, Issue 1 2007L. Jared West An approach to characterization of multilayer aquifer systems using open well borehole dilution is described. The approach involves measuring observation well flow velocities while a nearby extraction well is pumped by introducing a saline tracer into observation wells and collecting dilution vs. depth profiles. Inspection of tracer profile evolution allows discrete permeable layers within the aquifer to be identified. Dilution profiles for well sections between permeable layers are then converted into vertical borehole flow velocities and their evolution, using an analytic solution to the advection-dispersion equation applied to borehole flow. The dilution approach is potentially able to measure much smaller flow velocities that would be detectable using flowmeters. Vertical flow velocity data from the observation wells are then matched to those generated using a hydraulic model of the aquifer system, "shorted" by the observation wells, to yield the hydraulic properties of the constituent layers. Observation well flow monitoring of pumping tests represents a cost-effective alternative or preliminary approach to pump testing each layer of a multilayer aquifer system separately using straddle packers or screened wells and requires no prior knowledge of permeable layer depths and thicknesses. The modification described here, of using tracer dilution rather than flowmeter logging to obtain well flow velocities, allows the approach to be extended to greater well separations, thus characterizing a larger volume of the aquifer. An example of the application of this approach to a multilayer Chalk Aquifer in Yorkshire, Northeast England, is presented. [source] The influence of seasonal climatic parameters on the permafrost thermal regime, West Siberia, RussiaPERMAFROST AND PERIGLACIAL PROCESSES, Issue 1 2009Valeria V. Popova Abstract Statistical correlations between seasonal air temperatures and snow depths and active layer depths and permafrost temperatures were analysed for tundra (Marre-Salle) and northern taiga (Nadym) sites in Western Siberia. Interannual variations in active layer depth in the tundra zone correlated with the average air temperature of the current summer, and in peatland and humid tundra, also with summer temperatures of the preceding 1,2 years. In the northern taiga zone, the active layer depth related to current summer air temperature and to a lesser extent, to spring and/or winter air temperatures. Variations in summer permafrost temperatures at 5,10,m depth were correlated with spring air temperatures in the current and preceding 1,2 years. The weather regime during the preceding 1,2 years, therefore, reinforced or weakened ground temperature variations in a given year. Overall, the most important factors influencing the permafrost regime were spring and summer air temperatures, and in one case snow depth. However, statistical links between meteorological and permafrost parameters varied between the tundra and northern taiga zones and among landscape types within each zone, emphasising the importance of analyses at short temporal scales and for individual terrain units. Copyright © 2009 John Wiley & Sons, Ltd. [source] Modelling the wet deposition of reduced nitrogen over the British Isles using a Lagrangian multi-layer atmospheric transport modelTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 606 2005N. Fournier Abstract Wet deposition of reduced nitrogen is estimated for the United Kingdom using a Lagrangian long-term, long-range atmospheric transport model. Such long-range transport models are used to develop emission-control strategies to combat environmental acidification in the sensitive regions of the United Kingdom and Europe. These models currently consider the wet deposition as a loss term using scavenging rates and a simple seeder,feeder effect. The seeder,feeder effect is assumed to be the main process producing orographic precipitation since the majority of British Isles annual rainfall falls in frontal events. This paper focuses on the analysis of different parametrizations of the removal process by wet deposition. It is shown that the seeder,feeder effect is very dependent on flow direction. Therefore, a model of directional orographic enhancement of precipitation is developed to simulate this effect. A revised formulation of the wet deposition parametrization is suggested, incorporating the directional orographic precipitation produced with this model. This new formulation also takes into account the larger concentrations of ions dissolved in rain water measured in mountainous areas. Moreover, a new representation of the wet deposition process is developed by considering explicitly the mixing layer's depth calculated in the model. The results from the atmospheric model, with these revised parametrizations of the wet deposition, are then compared with measured wet deposition of reduced nitrogen. Firstly, with the new directional orographic rainfall, the modelled United Kingdom reduced nitrogen wet deposition budget is still underestimated but an increased correlation with measurements is obtained. Secondly, the inclusion of the calculated mixing layer's depth leads to a considerable improvement in the modelled reduced nitrogen wet deposition budget compared with measurements. Copyright © 2005 Royal Meteorological Society. [source] | ||||||||||