90 research outputs found
Modulo (1,1) periodicity of Clifford algebras and generalized (anti-)Möbius transformations
No full textSkew polynomial rings and nilpotent derivations
No full textElectrical Engineering, Mathematics and Computer Scienc
Inverse modelling of the rainfall-runoff relation: A multi-objective model calibration approach
No full textCivil Engineering and Geoscience
Investigation on the required processor capability necessary for carrying out the MLS procedural interception using conventional indicators
No full textDit rapport beschrijft het volgende: - Benodigde instrumenten en extra 'annunciators' om een zgn. MLS procedurele interceptie uit te voeren. - Minimum 'Capability' van het processorsysteem welke benodigd is om deze instrumenten aan te sturen. - De eisen aan een (digitaal) filter, nodig om een rustig aanwijsgedrag van de instrumenten te bewerkstelligen als gevolg van het foutgedrag van het MLS. - De parametersets van het gekozen filter.Electrical Engineering, Mathematics and Computer ScienceTelecommunicatie- en Verkeersbegeleidingssysteme
Fall Meeting's First Student and Early Career Conference
No full textIn a tradition that harks back to the ancient Greeks, students and early career scientists organized a symposium to help network, improve academic skills, and collaborate with peers.Water ManagementCivil Engineering and Geoscience
What scientists can learn from Plato's Symposium
No full textWater ManagementCivil Engineering and Geoscience
Agriculture in Kenya: Design of a small-scale irrigation system to stimulate agricultural activities in Kilole.
No full textThis thesis presents the results of a research done on the agricultural situation of Kilole. Kilole is a small Kenyan village located between Mombasa and the Tanzanian border. Looking at the annual rainfall, it can not be said that there is a lack of it in Kilole. However, because of its poor distribution the year is diverted in two rain seasons and two dry seasons. This has great influence on agriculture, because most crops can not withstand drought very easily. To understand the agriculture, a rainfall analysis has been performed first. With daily rainfall data from over thirty years, all kind of analysis have been performed. A trend analysis showed that there is no trend in the annual rainfall data. The long rain season onset has been determined, which is on average the 112th day of the year. Also a dry spell analysis has been done to see in which way drought occurs within the dry season. This showed that most rain falls within a very limited number of days and that the chance of having no rain for a week is already 78%. After an idea how the rain behaves was obtained it was time for a field trip. During two weeks the village of Kilole and its surroundings were visited in order to gather as much of relevant data. With the help of some semi-structured interviewing techniques it was tried to get an idea of the situation Kilole. It turned out that Kilolean farmers mainly grown maize, cassava and tomatoes. A lot of farmers use irrigation techniques to increase the yields of these crops and to make sure multiple crops can be grown each year. About half of the farmers in the village use irrigation, from which surface irrigation is most popular. Everybody digs holes to gain access to the groundwater. This is generally located thirty to one hundred centimeters below ground level, throughout the year. This means that that is always sufficient water for irrigation and that most crops can flourish, even in the dry season. Some people have the idea that the situation in Kilole should be improved. Improved in a way of higher yields, more crops and more irrigation. A number of initiatives have been seen from which three where pointed out to be of the most influence. The first was a dam that the government built a couple of years ago, together with the village. In the river bed paddy rice is grown in the wet season. The Kenyan government is campaigning for more rice production in the country and therefore financed a dam. This dam created a reservoir from which water could be used in the dry season to produce another harvest of rice every year. Due to a poor constructed dam it did not last long. Farmers were very content with the system, but since it does not work anymore and there are no funds, it is no longer used. The second initiative was a farmer which invested his profits in a well which now can be used freely by the villagers for drinking and irrigation. This shows that many people are willing to invest in the village in order to get higher yields and better welfare in general. The last imitative was a group of farmers which got funded with a micro-credit from abroad. This showed that many people are definitely eager to improve their lives and the village, but that a lack of funds often barricades the road to success. It was concluded that there is a general willingness to invest, produce and put effort to gain more. The only thing that withholds most farmers is a lack of knowledge, awareness or funds. Together with the Kilole Primary School it was concluded that one of the things to get this improvement is to start a educational program on irrigation. Hereby it is hoped to get rid of the lack of knowledge and awareness on agriculture and irrigation. Furthermore, this irrigation project would be a new (small) source of income for the school, which can be invested in better overall quality of the school. To achieve this a small-scale irrigation system was designed. Using harvested rainwater, the system is gravity run. This means that to external (mechanical) energy is needed to keep the system running. The only problem is the transport of water from the rainwater storage tank to the small polytank this is located 10 meters further and 1.5 meters above ground level. The solution is to use the energy of the pupils. Every week one of the three highest classes will have duty and with the hole class water is transported with buckets every day. Having the tank emptied twice a day will make sure the tomatoes will grown their best. Tomato crops are located in a greenhouse, to prevent pests, animals and extreme weather to ruined the harvest. Calculations and models showed that the system worked and that a small profit will be made every year. It can be concluded in the end that there are possibilities for Kilole to improve. People do want this and are willing to. The only problem is the lack of knowledge, awareness and funds. The first two will be taken away in time by the irrigation system at the primary school. Only the lack of funds is still a problem which has to be tackled. Though it is shown that there is a proper solution, micro-credits can only solve this problem completely when more people are willing to invest their money in villages like Kilole.Water ManagementCivil Engineering and Geoscience
Library 3.0 - The sun: Creator of delight
No full textDe bibliotheek van morgen waarin de gebruiker centraal staat en niet de content. De bibliotheek is gelegen op de RDM Campus te Rotterdam.AE lab4ArchitectureArchitectur
Diurnal differences in vegetation dielectric constant as a measure of water stress
No full textCurrently, vegetation is considered a barrier to soil moisture retrieval by both passive and active remote sensing missions. Microwave emission and backscattering of vegetation is driven by the vegetation dielectric constant, which is a function of vegetation water content. The latter is a measure of root zone water availability. Understanding the variation in dielectric properties of vegetation will contribute to soil moisture retrieval using microwaves in vegetated areas. This study presents a unique dataset of the diurnal pattern of the leaf dielectric properties, which was linked to vegetation water content and water stress. Using a microstrip line sensor, in-vivo dielectric property measurements were conducted on three maize leaves (leaf 8, 10 and 12) from 8 to 19 October 2012. A correlation was found between the resonant frequency of the microstrip line and the leaf water content of maize. This showed that a decrease of leaf water content during the day led to an increase of the resonant frequency. Water stress was quantified by calculating the evaporation deficit and by measuring the soil water tension at 30cm and 50cm depth. It was found that the diurnal difference in resonant frequency of the sensor at leaf 8 increased in similar fashion as the soil tension and evaporation deficit, which indicates a correlation between water stress and vegetation dielectric properties. The upper leaves 10 and 12 responded differently to increased water stress. The diurnal difference in resonant frequency of the sensor at leaf 10 and 12 decreased or was non-existent. The dielectric measurements revealed the complex reaction of vegetation to water stress and pointed out many opportunities for further research. The water-cloud model was used to demonstrate the impact of changing water content at different frequencies and polarizations. For L-,C-,X-,Ku- and Ka-band the sensitivity of radar backscatter to soil moisture and vegetation water content was modeled. This showed that at L-band, for low volumetric soil moisture (<0.2) vegetation is the main contributor to total backscatter. At higher frequencies backscatter was mainly sensitive to leaf water content. Time series analysis of modeled radar backscatter, based on field measurements of vegetation water content and soil moisture, showed that using the standard water-cloud model, the simulated diurnal difference in backscatter was small (0.05 dB). A modified water-cloud model was formulated that takes into account leaf and stalk water content separately. This model simulated a higher diurnal difference in backscatter (0.8 dB) and corresponded better to the trend in decreasing leaf water content and increasing water stress. This study presented interesting results that will hopefully stimulate follow up research projects. As a first step, it already revealed possibilities of using vegetation as an indicator for soil moisture, vegetation water status and water stress. The eventual possibilities of monitoring this at a global scale will lead to new innovative applications that will contribute to improving the state of the world.Water ResourcesWater ManagementCivil Engineering and Geoscience
Partitioning of evaporation fluxes in summer and winter using stable isotope approach
No full textIrrigation is the largest user of fresh water in the world. Unfortunately a large part of irrigation is unsustainable and inefficiently causing water scarcity with sometimes terrible effects on the water cycle, ecology, economy and food production. The key in determining the efficiency of irrigation is to investigate how much irrigation water is indeed used by crops for transpiration. Only this part of the total evaporation is used by crops to produce biomass and can be seen as productive evaporation. To separate evaporation into the productive (transpiration) and non-productive (interception and soil evaporation) terms we use stable isotopes 2-H and 18-O. This research investigates the changes of isotopic composition of stable isotopes 2-H and 18-O in the soil over the year in a lysimeter setup in the Netherlands. When the water balance is combined with isotopic values, an isotope mass balance can be made. This is used to separate evaporation fluxes and makes it possible to determine the transpiration flux of vegetation. During a six month period (November 2010 to June 2011) values of stable isotopes 2-H and 18-O in a lysimeter covered with grass were monitored. Furthermore, during a two month period (May and June 2011) a second lysimeter without vegetation was monitored to find out what the effect is of vegetation on isotope composition. When comparing the lysimeter with and without grass cover, it was found that transpiration plays no role in the non-covered lysimeter. In the latter, higher enrichment of soil water was observed and the isotope regression line had a lower slope. Isotope composition changes during the year. In winter (November to February) soil evaporation and isotopic enrichment were low. In summer (April to June) soil evaporation and isotopic enrichment were high. This research shows that it is possible to separate evaporation into soil evaporation and transpiration. During the cold period (December to February) the amount of transpiration was relatively high (75.0 % - 90.5 %) , since only limited soil evaporation could take place. When less water was available during warm periods (April and May), the share of transpiration in the total evaporation term decreased (47.3% - 53.4 %).Water ManagementCivil Engineering and Geoscience
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