177,882 research outputs found
PieterjanVerhelst/resident-eel-polder-analysis: Resident eel polder analysis
No full text<p>This is the first release of the R codes for resident eel polder analysis.</p>
Water management Polder 29 Bangladesh
No full textIn this study for a part of Polder 29, one of DDP's pilot polders, it has been determined to which extent the system of channels and structures have a drainage and irrigation capacity which meets the requirements for cultivation of High Yielding Varieties and recommendations have been made how to meet these requirements. Irrigation and drainage requirements are determined by crop characteristics, cultivation practices and climate. The irrigation requirement for High Yielding Varieties for Polder 29 has been determined to be 1.4 l/s.ha (gross requirement), while for the drainage requirement a value of 4.4 l/s.ha was found.WatermanagementCivil Engineering and Geoscience
Dynamical Casimir-Polder forces
No full textWe consider the dynamical (time-dependent) Casimir-Polder force between an atom and a perfectly conducting wall, as well as the dynamical Casimir-Polder force between two atoms in the presence of a boundary condition such as a conducting wall. The dynamical Casimir-Polder forces are obtained from iterative solutions of the Heisenberg equations for the time evolution of the electric and magnetic field operators around one atom in the presence of the conducting wall and related field energy densities, which are valid for any initial state. We consider both the case of an initially bare atomic state and of an initially partially dressed atomic state. The problem of relativistic causality in the field propagation during the atomic self-dressing is also discussed. Finally, we consider a specific model for an atomic partially dressed state and discuss the possibility of experimental observation of the dynamical atom-wall Casimir-Polder force
Casimir-Polder forces, boundary conditions and fluctuations
No full textWe review different aspects of atom–atom and atom–wall Casimir–Polder forces. We first discuss the role of a boundary condition on the interatomic Casimir–Polder potential between two ground-state atoms, and give a physically transparent interpretation of the results in terms of vacuum fluctuations and image atomic dipoles. We then discuss the known atom–wall Casimir–Polder force for ground- and excited-state atoms, using a different method which is also suited to extension to time-dependent situations. Finally, we consider the fluctuation of the Casimir–Polder force between a ground-state atom and a conducting wall, and discuss possible observation of this force fluctuation
Dynamical Casimir-Polder forces
No full textWe consider the dynamical Casimir-Polder force on an atom placed near an infinite conducting wall. The system is initially in a non equilibrium configuration such as a bare or a partially dressed state, and its time evolution is considered as well as the time dependence of the atom-wall Casimir-Polder interaction. A possible scheme to generate experimentally the initial partially dressed state and to detect the dynamical Casimir-Polder force is discussed
Polder system Can Tho City: Impact of the urban polder on Can Tho City
No full textVietnam is one of the five countries that is severely affected by the consequences of climate change. The extreme weather conditions and the increase of the sea level results in floods in the Mekong Delta, located in the South of Vietnam. Can Tho city, found in the heart of the Mekong Delta, is one of the cities that copes with water related issues on a regular basis. To be prepared for the future, the environmental and infrastructural issues need to be tackled. The resiliency of Can Tho got included of the World Bank program. The objective of this project of the World Bank is to reduce the flood risk in the urban core area and to improve connectivity between the city centre and the low risk urban growth areas. The structural solutions of the polder will be sluice gates, tidal sluice gates, the construction of river embankment, rehabilitation of the drainage system and constructing two regulation and water retention lakes. Additionally, building dykes with new roads and expanding or building new bridges will increase the connectivity of the city. All these measures will contribute on the resiliency of the city. The aim of this report is to identify the impact of the polder on the city, considering the infrastructural and the hydraulic aspects. To measure the impact, the current situation is simulated into two models, an infrastructure model and a hydraulic model. The results of hydraulic model show whether and when locations are flooded, whereas the aim of the infrastructure model is to identify flows on the network, the connectivity of the city and the flow changes after implementation of the new roads.CIE4061-09 Multidisciplinary Projec
Een nieuwe route door de polder
No full textEen nieuwe route door de polder, in: J. Bussemaker, R. van der Ploeg (red.), Leven na paars: Linkse visies op de derde weg, Amsterdam: Prometheus, november 2001, pp.150-159
Separation of fresh and brackish water in polder water canals
No full textPolders water canals are sometimes exposed to brackish seepage from the nearby saline sea (salinization). This is a problem because the canal water is used to irrigate crops. A characteristic of water is that less dense (fresh) water floats on top of dense (saline) water. In lakes and oceans, it is common that water layers with various densities flow on top of each other (stratification). However, this has not been observed yet on a small scale, such as in polder water canals. It is assumed that, with a traditional weir, fresh water is discharged, and saline water stays behind. To encounter this, a modified weir is developed. It uses an underflow gate in front of the traditional weir to discharge the bottom water out of the canal. This research aimed to investigate if stratification happens in polder water canals and to explore how a modified weir can be implemented. The Negenboerenpolder in Groningen (the Netherlands) served as an example. Multiple methods are used because of the broad and practical nature of the problem. First, field measurements in the Negenboerenpolder demonstrated stratification in polder water canals. At multiple locations in the polder, the Electrical Conductivity (EC) is measured over the depth or continuously measured at two depths. Secondly, flume experiments gave information about the experimental procedure and implementation of a modified weir. Thirdly, 2D simulations of a modified weir are done in ANSYS Fluent, a Computation Fluid Dynamics (CFD) software. The simulations suggest that a modified weir works as expected, but the model is not completely representative. Observations are that such a weir is more effective in discharging brackish water with a low flow velocity and a larger distance between the underflow gate and the weir. Implementation advice for a modified weir is also included in this research. To conclude, this research implies that a modified weir can be used to discharge brackish water, but the design and implementation need to be done carefully. Recommendations for future research are to experiment with a modified weir in a polder and to build a 3D CFD model to investigate the flow around the underflow gate.Water Managemen
Casimir Polder forces between two accelerating atoms and the Unruh effect
No full textThe Casimir-Polder force between two atoms with equal uniform acceleration and separated by a constant distance R is considered. We show that, in the low-acceleration limit, while the near-zone R-6 behavior of the interatomic interaction energy is not changed by the acceleration of the atoms, the far-zone interaction energy decreases as R-5 instead of the well-known R-7 behavior for inertial atoms. Possibility of an indirect detection of the Unruh effect through measurements of the Casimir-Polder force between the two accelerating atoms is also suggested. We also consider a heuristic model for calculating the Casimir-Polder potential energy between the two atoms in the high-acceleration limit
- …
