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Water Processes (water + process)

Distribution by Scientific Domains

Earth and Environmental Science	40%

Selected Abstracts

Growth Per Cycle in Atomic Layer Deposition: Real Application Examplesof a Theoretical Model,

CHEMICAL VAPOR DEPOSITION, Issue 6 2003
R.L. Puurunen
Abstract In a previous paper, a theoretical model was derived to describe the growth per cycle in atomic layer deposition (ALD) as a function of the chemistry of the growth when compounds are used as reactants. This paper presents examples of how the model can be applied to investigate the mechanisms of real ALD processes. Three processes that represent different classes of compound reactants were selected for study: the trimethylaluminum/water process to grow aluminum oxide, the yttrium 2,2,6,6-tetramethyl-3,5-heptanedionate (thd)/ozone process to grow yttrium oxide, and the titanium tetrachloride/water process to grow titanium dioxide. The results obtained by applying the model were, in general, consistent with the results obtained through separate investigations of the reaction mechanisms. The model was shown to be a useful tool in investigations of the reaction chemistry of real ALD processes. [source]

The behavior of specific sediment yield in different grain size fractions in the tributaries of the middle Yellow River as influenced by eolian and fluvial processes

EARTH SURFACE PROCESSES AND LANDFORMS, Issue 8 2008
Jiongxin Xu
Abstract Based on data from 35 stations on the tributaries of the Yellow River, annual specific sediment yield (Ys) in eight grain size fractions has been related to basin-averaged annual sand,dust storm days (Dss) and annual precipitation (Pm) to reveal the influence of eolian and fluvial processes on specific sediment yield in different grain size fractions. The results show that Ys in fine grain size fractions has the highest values in the areas dominated by the coupled wind,water process. From these areas to those dominated by the eolian process or to those dominated by the fluvial process, Ys tends to decrease. For relatively coarse grain size fractions, Ys has monotonic variation, i.e. with the increase in Dss or the decrease in Pm, Ys increases. This indicates that the sediment producing behavior for fine sediments is different from that for relatively coarse sediments. The results all show that Ys for relatively coarse sediments depends on the eolian process more than on the fluvial process, and the coarser the sediment fractions the stronger the dependence of the Ys on the eolian process. The Ys,Dss and Ys,Pm curves for fine grain size fractions show some peaks and the fitted straight lines for Ys,Dss and Ys,Pm relationships for relatively coarse grain size fractions show some breaks. Almost all these break points may be regarded as thresholds. These thresholds are all located in the areas dominated by the coupled wind,water process, indicating that these areas are sensitive for erosion and sediment production, to which more attention should be given for the purpose of erosion and sediment control. A number of regression equations were established, based which the effect of rainfall, sand,dust storms and surface material grain size on specific sediment yield can be assessed. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Modeled interactive effects of precipitation, temperature, and [CO2] on ecosystem carbon and water dynamics in different climatic zones

GLOBAL CHANGE BIOLOGY, Issue 9 2008
YIQI LUO
Abstract Interactive effects of multiple global change factors on ecosystem processes are complex. It is relatively expensive to explore those interactions in manipulative experiments. We conducted a modeling analysis to identify potentially important interactions and to stimulate hypothesis formulation for experimental research. Four models were used to quantify interactive effects of climate warming (T), altered precipitation amounts [doubled (DP) and halved (HP)] and seasonality (SP, moving precipitation in July and August to January and February to create summer drought), and elevated [CO2] (C) on net primary production (NPP), heterotrophic respiration (Rh), net ecosystem production (NEP), transpiration, and runoff. We examined those responses in seven ecosystems, including forests, grasslands, and heathlands in different climate zones. The modeling analysis showed that none of the three-way interactions among T, C, and altered precipitation was substantial for either carbon or water processes, nor consistent among the seven ecosystems. However, two-way interactive effects on NPP, Rh, and NEP were generally positive (i.e. amplification of one factor's effect by the other factor) between T and C or between T and DP. A negative interaction (i.e. depression of one factor's effect by the other factor) occurred for simulated NPP between T and HP. The interactive effects on runoff were positive between T and HP. Four pairs of two-way interactive effects on plant transpiration were positive and two pairs negative. In addition, wet sites generally had smaller relative changes in NPP, Rh, runoff, and transpiration but larger absolute changes in NEP than dry sites in response to the treatments. The modeling results suggest new hypotheses to be tested in multifactor global change experiments. Likewise, more experimental evidence is needed for the further improvement of ecosystem models in order to adequately simulate complex interactive processes. [source]

Convective Available Potential Energy (CAPE) in mixed phase cloud conditions

THE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 624 2007
B. Früh
Abstract An approximate but pragmatic approach is presented to define Convective Available Potential Energy (CAPE) in mixed phase cloud conditions. The underlying process calls for mixed (i.e. liquid and ice) phase parcels and assumes the liquid fraction to be a unique function of temperature. The approach is meant to represent average conditions. Differences between this and more traditional approaches are quantified and discussed for mean tropical conditions. Generally freezing increases parcel temperature and, hence, buoyancy. If freezing occurs isobarically (as was often assumed in the past), all water changes phase at a single level resulting in a discontinuity in buoyancy at that level. By contrast, the mixed phase parcel process implies a continuous phase transition in a finite range of temperatures Tfs , T , Tfe, leading to a gradual change of buoyancy with altitude and preventing any temperature inversion. The details of this gradual change depend on the choice of the specified temperature range [Tfs, Tfe]. High in the troposphere, where all water is frozen irrespective of the details, the differences between the buoyancy profiles are small (but finite). CAPE is very sensitive to the treatment of the freezing process. Isobaric freezing at a relatively high temperature (e.g. , 5 °C) in a reversible process may increase CAPE by a factor of 2 to 3, and this increase is similar in magnitude to the difference between the pseudo-adiabatic and the reversible processes for pure water parcels. Both of these processes are considered less realistic than the reversible mixed phase process with continuous freezing over a broad temperature range [Tfs, Tfe] = [,5 °C, , 40 °C]; the corresponding CAPE lies about half way between the reversible and irreversible pure water processes. For clouds with finite precipitation efficiency the effect of freezing is less pronounced than for reversible conditions. Copyright © 2007 Royal Meteorological Society [source]