| 1. |
- Frühwald, Eva, et al.
(författare)
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Teachers’ view on combining assessment elements into a holistic assessment concept
- 2008
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Ingår i: [Host publication title missing].
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Konferensbidrag (refereegranskat)abstract
- Abstract in UndeterminedAssessments of students’ knowledge and skills are sometimes habitually performed, but the design of proper assessment concepts – beneficial to both teaching and learning – ought to be a central issue for all course planners in higher education. The main purpose of this paper is to discuss a variety of assessment elements, as well as ways in which to combine them. It uses experiences from Lund University’s Faculty of Engineering (LTH) to provide suggestions and advice for course planners. The discussion is based on the combination of a literature review in the field of teaching and learning, of empirical material obtained from surveys and group discussions with 22 teachers at LTH, and of the authors’ own experiences in their capacity as course leaders and teachers. The study reveals a preference for projects and written assessment, as compared with the less preferred individual oral assessment. The paper indicates potential for quality enhancements through the adapted tailoring of assessment elements into holistic assessment concepts.
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| 2. |
- Persson, Magnus, et al.
(författare)
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A profiling TDR probe for water content and electrical conductivity measurements of soils
- 2010
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Ingår i: European Journal of Soil Science. - : Wiley. - 1365-2389 .- 1351-0754. ; 61:6, s. 1106-1112
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Tidskriftsartikel (refereegranskat)abstract
- Measurements of water content profiles are of great interest in hydrology and soil science. Time domain reflectometry (TDR) is a well-established method for water content measurements; however, most TDR probe designs are suitable for measurements in only a small soil volume. In this article, a 1-m long TDR profiling probe with five measurement sections is described. Unlike most other previous profiling probes, our probe allows for both dielectric permittivity (e) and electrical conductivity (sa) measurements. The accuracy of the e and sa measurements was excellent; the precision of the measurements was, however, significantly poorer than with a 0.20-m long standard three rod TDR probe. The new probe was installed in a field and successfully measured water content profiles during the growing season of 2009. During an infiltration experiment it was shown that because of its geometry, the profiling probe over-estimated the wetting-front velocity. At a 0.10-m depth, the over-estimation was almost 30%. The over-estimate will be less significant at greater depths.
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| 3. |
- Persson, Magnus, et al.
(författare)
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A small-scale matric potential sensor based on time domain reflectometry
- 2006
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Ingår i: Soil Science Society of America Journal. - 0361-5995. ; 70:2, s. 533-536
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Tidskriftsartikel (refereegranskat)abstract
- Measurements of soil matric potential (Psi) are needed in many soil science applications. In the present study, a small matric potential sensor having a length of 30 mm and a diameter of 9.6 mm was developed. The sensor consists of two coils made of lacquer-coated copper wires embedded in gypsum. The dielectric constant of the gypsum (K-gypsum) was measured with time domain reflectometry (TDR). The gypsum probes were tested in a sandy loam soil using a pressure extractor to obtain the relationship between K-gypsum and Psi, allowing inference of the soil Psi in equilibrium with the sensor. It was shown that the gypsum probe could give Psi estimates with a root mean square error (RMSE) of around 50 kPa in the range of -20 to -1500 kPa. Most of the sensitivity of the sensor was in the -50- to -1000-kPa range.
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| 4. |
- Persson, Magnus, et al.
(författare)
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Time-domain reflectometry probe for water content and electrical conductivity measurements in saline porous media
- 2004
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Ingår i: Vadose Zone Journal. - 1539-1663. ; 3:4, s. 1146-1151
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Tidskriftsartikel (refereegranskat)abstract
- A new coated time-domain reflectometry (TDR) probe design is described and evaluated. In contrast to previous coated TDR probes, our probe may be used to measure both the dielectric constant (K-a) and bulk electrical conductivity (sigma(a)) in saline porous media. This was made possible by attaching two coaxial cables to a 0.27-m three-rod with a coated central rod. The shield of the first cable was to one of the outer rods and the conductor was connected to the coated central rod. The conductor and shield of the other coaxial cable were connected to each of the two outer rods, respectively. Thus, our probe consists of two unbalanced, two-rod probes. The probe is called coated-uncoated probe (CUP). Four prototypes with two different coating materials (i.e., polyolefin and kynar heat-shrink tubes) were evaluated. The probes were calibrated in several fluids having different K-a and sigma(a). The K-a measurement of the coated part the probe was successfully fitted to target K-a using a two-phase dielectric mixing model. Due to signal attenuation, measurements of K-a were not possible for sigma(a) higher than 9 dS m(-1) for the polyolefin-coated probes whereas the upper limits for the kynar-coated probes and the uncoated probe were 5 and 2.5 dS m(-1), respectively. Measurements of sigma(a) are only possible with the uncoated part. Measurements of K-a and sigma(a) were also taken during three upward infiltration experiments in sand using soil solution electrical conductivities of 0.01, 6.31, and 12.03 dS m(-1). For the uncoated part, K-a could not be measured when sigma(a) was higher than about 2 dS m(-1), whereas K-a measurements were possible using the coated part even when sigma(a) was 3 dS m(-1).
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| 5. |
- Bengtsson, Lars, et al.
(författare)
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Hydrology of transport systems
- 2017
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Ingår i: Handbook of Applied Hydrology, Second Edition. - 9780071835091
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Bokkapitel (refereegranskat)
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| 6. |
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| 7. |
- Aboulila, Tarek Selim, et al.
(författare)
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Assessment of inter-plant emitter distance and effects of irrigation water salinity on APRDI using Hydrus-2D
- 2011
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Ingår i: European Journal of Scientific Research. - 1450-216X. ; 58, s. 266-277
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Tidskriftsartikel (refereegranskat)abstract
- Abstract in UndeterminedModern irrigation techniques are becoming increasingly important in water-scarce countries. In this study, a two-dimensional water and solute transport model, Hydrus-2D, was used to assess the impact of inter-plant emitter distance (IPED) and irrigation water salinity on soil moisture and salinity distribution as well as on water balance components under alternate partial root-zone surface drip irrigation (APRDI) of tomato growing in loamy sand soil. Three IPED (20, 30, and 40 cm) and three irrigation water salinity levels (0, 1, and 2 dS/m) were used to execute different simulation scenarios. Simulation results indicated that the fluctuations in water content within the root zone were more pronounced in case of 20 cm IPED. The root water uptake increased as the IPED decreased. Using brackish irrigation water in APRDI caused significant augmentation in soil salinity in the top soil layer especially at the location of plant. The impact of irrigation water salinity on root water uptake increased as the IPED increased. As irrigation water salinity increased the root water uptake decreased. At plant location, soil salinity reached its highest values at the top soil layer in case of 30 and 40 cm IPED with brackish irrigation water. However, high soil salinity values were observed between the 40 and 65 cm depths in case of 20 cm IPED. Based on the results, it appears that APRDI with non-saline irrigation water is more effective with short IPED considering that approximately half of the root system was exposed to drying cycle. In addition, short IPED is recommended in APRDI when using brackish irrigation water especially for plants with shallow root system taking into account crop salinity tolerance.
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| 8. |
- Aboulila, Tarek Selim, et al.
(författare)
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Field experiment and numerical simulation of point source irrigation with multiple tracers.
- 2013
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Ingår i: International Journal of Sustainable Water and Environmental Systems. - 1923-7545.
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- In this study, three plots in sandy soil in northern Tunisia were irrigated by a single irrigation dripper with a solution containing dye and bromide for three successive hours. Fifteen hours after ceasing of infiltration, horizontal 5 cm trenches were dug. Dye pattern, bromide concentration, and water content were recorded. Indication of preferential flow due to water repellency of initial dry soil was found during the early stages of infiltration. However no deep preferential flow occurred. This enables the use of drip irrigation to improve the sustainability of irrigation systems. Numerical simulation using Hydrus-2D was conducted for the field experiment. It was found that in both field experiments and numerical simulation the mobility of the bromide is different from the mobility of dye; the dye was retarded approximately twice by volume compared to bromide. The simulation results support the use of Hydrus-2D as a roughly, rapid and labor saving tool for investigation tracers’ mobility in sandy soil under point source irrigation.
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| 9. |
- Aboulila, Tarek Selim, et al.
(författare)
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Influence of geometric design of alternate partial root-zone subsurface drip irrigation (APRSDI) with brackish water on soil moisture and salinity distribution
- 2012
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Ingår i: Agricultural Water Management. - : Elsevier BV. - 1873-2283 .- 0378-3774. ; 103, s. 182-190
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Tidskriftsartikel (refereegranskat)abstract
- In alternate partial root-zone irrigation (APRI) a significant amount of irrigation water can be saved without considerable yield reduction. In this paper, Hydrus-2D/3D was used to investigate the impact of geometric design of alternate partial root-zone subsurface drip irrigation (APRSDI) with brackish water for growing tomato on soil moisture and salinity distribution. Three inter-plant emitter distances (IPED; 20, 30, and 40 cm), two emitter depths (10 and 20 cm), and three irrigation water salinity levels (0, 1, and 2 dS m-1) were used to implement the proposed simulation scenarios in loamy sand soil during a 40-day simulation period. The simulation results showed that higher soil moisture content was found beneath the plant trunk in case of 20 cm (short IPED) and near the domain border in case of 30 and 40 cm IPED. Short IPED guarantees more water in the maximum root density zone. A deeper wetting front occurred for deep emitter depth, while the wetting front reached the soil surface for shallow emitter depth. Salinity results revealed that as irrigation water salinity increased, the salinity in the top soil increased. In addition, the salinity at the soil surface increased as IPED and emitter depth increased. Higher root water uptake rates were recorded in the case of 20 cm IPED while the emitter depth did not show any considerable effect on root water uptake rates. Moreover, the applied irrigation water was fully consumed by the plant in case of short IPED. Emitter depth and salinity of irrigation water had negligible effect on amount of irrigation water extracted by plant roots and percolated amount below the bottom boundary of the flow domain. Overall, short IPED is recommended in APRSDI with or without brackish irrigation water regardless of the emitter depth.
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| 10. |
- Aboulila, Tarek Selim, et al.
(författare)
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Numerical evaluation of subsurface trickle irrigation with brackish water
- 2013
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Ingår i: Irrigation Science. - : Springer Science and Business Media LLC. - 0342-7188 .- 1432-1319. ; 31:5, s. 1125-1137
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Tidskriftsartikel (refereegranskat)abstract
- In this study, an assessment for a proposed irrigation system in the El-Salam Canal cultivated land, Egypt, was conducted. A numerical model (HYDRUS-2D/3D) was applied to investigate the effect of irrigation amount, frequency, and emitter depth on the wetted soil volume, soil salinity levels, and deep percolation under subsurface trickle irrigation (SDI) of tomato growing with brackish irrigation water in three different soil types. The simulations indicated that lower irrigation frequency increased the wetted soil volume without significant increase in water percolate below the plant roots. Deep percolation decreased as the amount of irrigation water and emitter depth decreased. With the same amount of irrigation water, the volume of leached soil was larger at lower irrigation frequency. The salinity of irrigation water under SDI with shallow emitter depth did not show any significant effect on increasing the soil salinity above tomato crop salt tolerance. Based on the results, it appears that the use of SDI with brackish irrigation water is an effective method for growing tomato crop in El-Salam Canal cultivated land especially with shallow emitter depth.
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