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We present a new open-source and modular instrumentation package composed of up to ten automatic infiltrometers connected to data acquisition systems for automatic recording of multiple infiltration experiments. The infiltrometers are equipped with differential transducers to monitor water level changes in a Mariotte reservoir, and, in turn, to quantify water infiltration rates. The data acquisition systems consist of low-cost components and operate on the open-source microcontroller platform Arduino. The devices were tested both in the laboratory and on different urban and agricultural soils in France and India. More specifically, we tested three procedures to treat the transducers readings, including a filtering algorithm that substantially improved the ability to determine cumulative infiltration from raw data. We combined these three procedures with four methods for estimating the soil parameters from infiltrometer data, showing pros and cons of each scenario. We also demonstrated advantages in using the automatic infiltrometers when infiltration measurements were hindered by: i) linearity in cumulative infiltration curves owing to gravity-driven flow, ii) an imprecise description of the transient state of infiltration, and iii) the occurrence of soil water repellency. The use of the automatic infiltrometers allows the user to obtain more accurate estimates of soil hydraulic parameters, while also reducing the amount of effort needed to run multiple experiments.

The objective of this paper was to evaluate a recently proposed comprehensive model for three-dimensional single-ring infiltration and its suitability for estimating soil hydraulic properties. Infiltration data from four different soils with contrasting characteristics were inverted to estimate field-saturated soil hydraulic conductivity, Kfs, values using a total of fourteen different scenarios. Those scenarios differed by: i) the way they constrained the macroscopic capillary length, λ, and the initial and saturated soil water contents, θi and θs, ii) the use of transient or steady-state data, and iii) the fitting methods applied to transient data. For comparative purposes, the SSBI method (Steady version of the Simplified method based on a Beerkan Infiltration run) was also applied. For validation purposes Kfs data estimated from the different scenarios were compared with those values obtained by numerical inverse modeling with HYDRUS-2D/3D. This comparison identified Approaches 1 and 3, which respectively estimate Kfs via optimization and using analytical expressions, as the most accurate methods. The steady-state scenario of Approach 4 and the SSBI method, both of which use a λ value of first approximation, appeared preferable for field campaigns aimed to sample remote or large areas, given that they do not need additional data and still provide acceptable estimates. The reliability of Kfs data was also checked through a comparison with unsaturated hydraulic conductivity, Kh, values measured in laboratory on extracted soil cores, in order to discriminate between theoretically possible (Kfs > Kh) and impossible (Kfs ≤ Kh) situations. Physically possible Kfs values were always obtained with the exception of the crusted soil, where Kfs < Kh situations suggested that the crust layer reduced water flow during ponding experiments in the field. The new comprehensive model tested in this study represents a valuable tool for analyzing both transient and steady-state infiltration data, as well as experiments carried out with different depths of ponded water, ring sizes and ring insertion depths.

In the vadose zone, preferential flow and transport are much more common than uniform water flow and solute transport. In recent decades, several models have been developed for preferential water flow and physical nonequilibrium solute transport. Among these models, the dual-permeability approach is an interesting tool for the conceptualization and modeling of preferential flow. However, this approach has been mainly studied from a numerical point of view. In this study, we developed a new analytical model for water infiltration into dual-permeability soils. The model is based on the analytical model originally proposed for single-permeability soils. The proposed model relies on the assumption that the water exchange rate at the interface between the matrix and fast-flow regions does not change cumulative infiltration at the soil surface, so that the total cumulative infiltration can be set equal to the sum of independent cumulative infiltrations into each region. This assumption was investigated using numerically generated data. The proposed analytical model was then used to evaluate the effects of fast-flow region hydraulic properties and hydraulic conditions on total cumulative infiltration for the case of single- and multi-tension water infiltration experiments. Finally, both single- and dual-permeability models were evaluated with respect to their ability to fit experimental data and associated problems of non-uniqueness in optimized parameters. The proposed model could serve as a new tool for modeling and characterizing preferential flow in the vadose zone.

Studying soil hydrological processes requires the determination of soil hydraulic parameters whose assessment using traditional methods is expensive and time-consuming. A specific method, Beerkan estimation of soil transfer parameters referred to as BEST was developed to facilitate the determination of both the water retention curve, [theta](h), and the hydraulic conductivity curve, K([theta]), defined by their shape and scale parameters. BEST estimates shape parameters from particle-size distribution analysis and scale parameters from infiltration experiments at null pressure head. Saturated water content is measured directly at the end of infiltration. Hydraulic conductivity and water pressure scale parameters are calculated from the steady-state infiltration rate and prior estimation of sorptivity (S). This is provided by fitting transient infiltration data on the classical two-term equations with values from zero to a maximum corresponding to null hydraulic conductivity and using a data subset for which the two-term infiltration equations are verified as valid. BEST was compared with other fitting methods to estimate sorptivity and hydraulic conductivity from infiltration modeling data on the basis of the same infiltration equations for three contrasting soils: agricultural soil, sandy soil, and a coarser fluviogiacial deposit. The other methods failed sometimes to model accurately experimental data and to provide values in agreement with physical principles of water infiltration (negative values for hydraulic conductivity, too high steady-state infiltration rate). None of these anomalies was encountered when modeling cumulative infiltration with BEST. BEST appears to be a promising, easy, robust, and inexpensive way of characterizing the hydraulic behavior of soil.

A spray pyrolysis method was used to deposit beta-In2S3 and beta-In2-xA1xS3 thin films on different substrates.

CuInS[sub 2] and CuIn[sub (1-x)]Al[sub x]S[sub 2] thin films have been deposited on different substrates using the spray pyrolysis technique at 320 °C. X-ray diffraction, atomic force microscopy, and scanning electron microscopy were used to characterize the structure of the films; the surface compositions of the films were studied by Auger electrons spectroscopy and energy dispersive spectrometry (EDS), the work function and the photovoltage by the Kelvin method. Using these techniques, we have specified the effect of the nature of the substrate, its surface morphology, and the introduction of small amounts of Al in the layer on the properties of the films. The best crystallized composition of CuInS[sub 2] was obtained for deposits on pyrex. This was improved by the introduction of Al atoms. The work function differences (&fgr;[sub material]-&fgr;[sub probe]) for CuInS[sub 2] and CuIn[sub (1-x)]Al[sub x]S[sub 2] deposited on pyrex were equal to -350 meV and to -400 meV, respectively. Putting Al atoms in the film increases &fgr;[sub m] (by about 50 meV) and induces the formation of a negative surface barrier. The best composition was obtained for CuInS[sub 2] deposited on SnO[sub 2] and annealed. Auger studies shows that the concentration of S and C elements increased when the samples were annealed under a vacuum, whereas the concentration of Cu, In, and O decreased. In the case of CuInS[sub 2] grown on pyrex, the introduction of Al increases the O, S, and Cl concentrations and reduces Cu and C concentrations. Analysis of the film compositions by EDS gives the following concentrations [Cu]=24.270%, [In]=24.487%, [S]=46.670%, and [Cl]=4.573%. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

β-In[sub 2]S[sub 3] and β-In[sub 2-x]Al[sub x]S[sub 3] thin films have been deposited on different substrates using the spray pyrolysis technique at 320 °C. X-ray diffraction, atomic force microscopy, and scanning electron microscopy were used to characterize the structure of the films; the surface compositions of the films were studied by Auger electrons spectroscopy and energy dispersive spectrometry (EDS), the work function and the photovoltage by the Kelvin method. Using these techniques, we have specified the effect of the nature of the substrate, of its surface morphology, of the introduction of small amounts of Al in the layer, on the properties of the films. The best crystallized of β-In[sub 2]S[sub 3] were obtained for deposits on pyrex. This was improved by the introduction of Al atoms. The work function differences (φ[sub material]-φ[sub probe]) for β-In[sub 2]S[sub 3] and β-In[sub 2-x]Al[sub x]S[sub 3] deposited on steel were equal to -150 meV and to -180 meV, respectively. Putting Al atoms in the film increases φ[sub m] (by about 30 meV) and induces the formation of a negative surface barrier. The concentration of In, S, and O elements increased when the samples were annealed under a vacuum, whereas the concentration of carbon decreased. The best composition was obtained for In[sub 2]S[sub 3] deposited on SnO[sub 2] and annealed. The introduction of Al increases O and C concentrations and reduce In, Cl, and S concentrations. Analysis of the film compositions by EDS gives the following concentrations [In]=37%, [S]=52%, and [Cl]=11%. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Examines the modifications of the electronic properties of cleaved GaAs (110) surfaces induced by oxygen adsorption, using contact potential difference measurement. Factors that affect the initial work function and surface photovoltage topographies; Indicators of the density and energy of induced states; Analysis of noticeable surface modification that appears at low exposures.

The structure, surface composition and electronic properties of CuInS2 and CuIn(sub 1-x)Al(sub x)S2 films, which are deposited on various substrates using chemical spray pyrolisis technique, are investigated. From these studies, it was possible to determine the quality of the surface and therefore select the best process to produce material convenient for a good epitaxy.

The permeable pavement is a compensatory drainage technique for urban waters that aims to control runoff and to ensure ideal hydrological conditions. This work had as main objectives to evaluate the infiltration capacity of a permeable pavement (PP) at real scale, through analytical and numerical modeling. It relies on water infiltration experiments and related modeling for the hydrodynamic characterization of the coating layer (saturated hydraulic conductivity, Ks, and sorptivity, S). A large panel of analytical and numerical models was considered, and several estimates were obtained. Then, the criteria for the evaluation of the maintenance requirement of the permeable pavements were computed for all the Ks-estimates considering the NCRS standards (assessment of permeability levels). The results indicated nice fits and accurate estimates for both the saturated hydraulic conductivity and the sorptivity. However, the Ks-estimates depended on the considered model and led to contrasting results in terms of classification. For 8 of the 9 models, the value of the Ks-estimate leads to the classification of “Group A” of the NCRS soil classification, meaning a very permeable material. In contrasts, the last method (numerical inverse modeling) classified the permeable pavement as “Group D”, i.e., soils with low permeability. Those results show the importance of the selection of characterization methods regarding the assessment of the hydrological classification of permeable pavements.

The determination of soil hydraulic properties is important in several environmental sciences but may be expensive and time consuming. Therefore, during the last decades, a great effort has been made in soil sciences to develop relatively easy, robust, and inexpensive methods for soil hydraulic characterization. In this manuscript, we reviewed and discussed different infiltrometer techniques in light of the available experimental applications. More specifically, we considered the simplified falling head (SFH) infiltrometer technique and the single-ring infiltration experiment of the Beerkan type. Concerning this latter method, we considered different algorithms for data analysis: two simplified methods based on the analysis of transient (TSBI) and steady (SSBI) Beerkan infiltration data, and the Beerkan Estimation of Soil pedoTransfer parameters algorithm (BEST), that allows to estimate the soil characteristics curves, i.e., the soil water retention curve and hydraulic conductivity functions. For a given method, after dealing briefly theory and practice, available literature references were reported to account for specific applications in order to provide findings on method validation and application. With the aim to provide practical information on available tools for a simpler application of the reviewed methods, several video tutorials were reported to show i) how to conduct correctly field experiments and ii) how to calculate saturated hydraulic conductivity or soil hydraulic functions using user-friendly tools for data analysis. Finally, details on a new automated single-ring infiltrometer for Beerkan infiltration experiments (i.e., construction, assembly and field use) were presented.

Investigates the modification of the electronic properties of indium phosphide (110) surfaces induced by oxygen exposure. Expectations from the exothermic reaction between oxygen and the substrate; Cause of the incorporation of oxygen into the substrate lattice; Influence of the initial oxygen exposure on the Schottky barrier height.