G. Arbat

Subsurface drip irrigation emitter spacing effects on soil water redistribution, corn yield and water productivity

Emitter spacings of 0.3 to 0.6 m are commonly used for subsurface drip irrigation (SDI) of corn on the deep, silt loam soils of the U.S. Great Plains. Subsurface drip irrigation emitter spacings of 0.3, 0.6, 0.9 and 1.2 m were examined for the resulting differences in soil water redistribution, corn grain yield, yield components, seasonal water use, and water productivity in a 4-year field study (2005 through 2008) at the Kansas State University Northwest Research-Extension Center, Colby, Kansas.

Using Computational Fluid Dynamics to Predict Head Losses in the Auxiliary Elements of a Microirrigation Sand Filter

It is often assumed that total head losses in a sand filter are solely due to the filtration media and that there are analytical solutions, such as the Ergun equation, to compute them. However, total head losses are also due to auxiliary elements (inlet and outlet pipes and filter nozzles), which produce undesirable head losses because they increase energy requirements without contributing to the filtration process. In this study, ANSYS Fluent version 6.3, a commercial computational fluid dynamics (CFD) software program, was used to compute head losses in different parts of a sand filter. Six different numerical filter models of varying complexities were used to understand the hydraulic behavior of the several filter elements and their importance in total head losses. The simulation results show that 84.6% of these were caused by the sand bed and 15.4% were due to auxiliary elements (4.4% in the outlet and inlet pipes, and 11.0% in the perforated plate and nozzles). Simulation results with different models show the important role of the nozzles in the hydraulic behavior of the sand filter. The relationship between the passing area through the nozzles and the passing area through the perforated plate is an important design parameter for the reduction of total head losses. A reduced relationship caused by nozzle clogging would disproportionately increase the total head losses in the sand filter.

Peer and Self-Assessment Applied to Oral Presentations from a Multidisciplinary Perspective.

This article analyses the use of peer and self-assessment in oral presentations as complementary tools to assessment by the professor. The analysis is based on a study conducted at the University of Girona (Spain) in seven different degree subjects and fields of knowledge. We designed and implemented two instruments to measure students’ peer and self-assessment, and a rubric to guide the assessment process. Results were compared with the marks awarded by the professor. In contrast with studies by other authors, which show a high correlation between these different assessment systems, our study revealed significant deviations. Applying peer and self-assessment to oral presentation activities also demonstrates their formative value above and beyond their summative usefulness.

Nonlinear numerical simulation of rainwater infiltration through road embankments by FEM

Abstract This paper presents the results of nonlinear numerical simulations carried out to analyze rainwater infiltration through a road embankment structure using the finite element method (FEM) technique. The analysis of this paper includes a simplification of a cross-sectional road embankment located in Santander (Northern Spain) and considers different realistic hydraulic material parameters, according to the relevant literature, in order to study their effect on water movement throughout the section over time. The model solved the nonlinear Richards’ equation using the constitutive relationships of van Genuchten–Mualem. Finally, the analysis of the numerical results reveals four main conclusions: (1) models based on FEM are suitable for analyzing rainwater infiltration in road structures, (2) the hard-shoulder area of the highway represents an important infiltration point for rainwater in road structures, (3) the embankment material can greatly affect the soil’s water content in this part of the road, and (4) the analysis of the soil water retention curve of the embankment material provides relevant information about its hydraulic behavior under unsaturated conditions.

A new predictive model for the filtered volume and outlet parameters in micro-irrigation sand filters fed with effluents using the hybrid PSO-SVM-based approach

Prediction of sand filter outlet values allows assessing drip emitter clogging risk.A hybrid model based on SVMs with the PSO technique was used for this prediction.The developed model predicted satisfactorily sand filter outlet parameters.Performance of the PSO-SVM model was better than with other techniques. Filtration is a key operation in micro-irrigation for removing the particles carried by water that could clog drip emitters. Currently, there are not sufficiently accurate models available to predict the filtered volume and outlet parameters for the sand filters used in micro-irrigation systems. The aim of this study was to obtain a predictive model able to perform an early detection of the filtered volume and sand filter outlet values of dissolved oxygen (DO) and turbidity, both related to emitter clogging risks. This study presents a novel hybrid algorithm, based on support vector machines (SVMs) in combination with the particle swarm optimization (PSO) technique, for predicting the main filtration operation parameters from data corresponding to 769 experimental filtration cycles in a sand filter operating with effluent. This optimization technique involves kernel parameter setting in the SVM training procedure, which significantly influences the regression accuracy. To this end, the most important physical-chemical parameters of this process are monitored and analyzed: effective sand media size, head loss across the filter and filter inlet values of dissolved oxygen (DO), turbidity, electrical conductivity (Ec), pH and water temperature. The results of the present study are two-fold. In the first place, the significance of each physical-chemical variables on the filtration is presented through the model. Secondly, a model for forecasting the filtered volume and sand filter outlet parameters is obtained with success. Indeed, regression with optimal hyperparameters was performed and coefficients of determination equal to 0.74 for outlet turbidity, 0.82 for filtered volume and 0.97 for outlet dissolved oxygen were obtained when this hybrid PSO-SVM-based model was applied to the experimental dataset, respectively. The agreement between experimental data and the model confirmed the good performance of the latter.

Using peer assessment to evaluate teamwork from a multidisciplinary perspective

Abstract This article analyses the use of peer evaluation as a tool for evaluating teamwork and students’ perceptions of this type of evaluation. A study was conducted of six subjects included on five degree courses at the University of Girona. In all of these subjects, students carried out a team activity, evaluated the performance of the team and the involvement of its different members, and responded to a survey on their perceptions of this evaluation system. We found the main factors influencing the evaluation and perception of teamwork to be teachers’ and students’ prior experience in this type of evaluation activity, the field where it is applied, the academic year students are enrolled on and the weight of the activity in the final mark. The results show that, in general, students’ views regarding such evaluation procedures are positive.

FEM-based Numerical Simulation of Water Flow Through a Road Shoulder Structure

Abstract Water infiltration and its effects on road structures is a topic of great interest in civil engineering. Water is one of the primary factors which affects the mechanical function of roads. Road structures are more often found in unsaturated conditions as opposed to saturated ones. Under unsaturated conditions water flow is primarily by capillarity, while under saturation gravity is the primary force causing water movement. Moreover, under unsaturated conditions the equations describing water flow into soils are highly nonlinear, showing a higher difficulty in its numerical solution. At present there is a limited volume of literature on the hydraulic properties and numerical simulation of water flow in road structures under unsaturated conditions. This paper presents experimental data and nonlinear numerical simulations using the finite element method (FEM) to analyze the water infiltration through a road should structure in unsaturated conditions. Results show that the shoulder section evaluated in this study does not represent a zone of high water infiltration due to the low infiltration capacity of the materials evaluated, and that hydraulic properties measured in the laboratory can be successfully used in numerical codes for assessing water flow through road structures in future analysis. This work indicates that continuous rainfall events, even of low intensity, can cause more infiltration than a single rainfall event of high intensity.

Irrigation Performance and Water Productivity in Ornamental Plant Production in Girona (Spain)

The ornamental plant production in Girona (Spain) represents an important economic sector, being with 1200 hectares one of the first production zones in Southern Europe.

Filter and emitter performance of micro-irrigation systems using secondary and tertiary effluents.

The performance of four filtration systems (sand, screen, disc and a combination of screen and disc) and six emitter types (four pressure compensated and two non-pressure compensated), using secondary and tertiary effluents from a wastewater treatment plant, was studied for 1000 h. Only sand filtration significantly reduced turbidity and suspended solids. The best emission uniformity was obtained by the emitters placed after the sand filter and the screen filter with the secondary and tertiary effluent, respectively. On the other hand, emitters that operated with disc filters showed the worst emission uniformity for both effluents. Emitter type P2 was the only one achieving values of emission uniformity higher than 90% with all filtration systems and effluents except the screen filter and the tertiary effluent.