114 research outputs found
Run-up tests on a permeable slope
No full textThis report is the result of the Master of Science thesis of the author, at the Delft University of Technology, sub-Faculty of Civil Engineering. Although a lot is known nowadays about the run-up on smooth and impermeable slopes as well as the run-up on slopes covered with a rock armour layer, the physical properties of the armour layer of a rubble mound breakwater are not incorporated in the relations describing the run-up on a breakwater's slope. The roughness of a slope and its permeability, which can be described by a characteristic diameter of the armour unit and the porosity of the layer, are not used in the description of the run-up. This report is an attempt to get insight into the influence that the roughness and the permeability of a slope have on the run-up on this slope. In order to achieve this goal, dimensional parameters are derived describing the roughness of a slope and its permeability. Firstly, the framework of the design of a breakwater is given in order to place the run-up on a rough, permeable slope. The run-up itself is dealt with separately. Experiments were performed in order to obtain data that can be used to quantify the influence of the roughness of the slope and its permeability. The experiments were performed leaving the permeability of the whole structure out of consideration. To achieve a difference in porosity of the armour layer, rock armour units were used as well as tetrapod armour units. Two approaches of data analysis are applied on the data obtained from these experiments. This first approach describes the run-up on a rough, permeable slope by a combination of a roughness parameter, a permeability parameter and the breaker parameter. The roughness parameter and the permeability parameter are derived by forming non-dimensional parameters that describe roughness and permeability. The run-up, usually made non-dimensional using the wave height (H) is made non-dimensional here using the nominal diameter. This gave better results in combination with the derived parameters describing the roughness and the permeability of a slope. The second approach describes the run-up on a rough, permeable slope by using the relative run-up R.lH and a newly derived non-dimensional parameter resembling the Iribarren parameter, but incorporating the influence of the permeability of the armour layer. When the relative run-up is put against the Iribarren parameter and is put against the newly derived non-dimensional parameter, the appearing scatter is less in the latter case. In both approaches, two relations describing the run-up on a rough permeable slope are derived. One for breaking waves and one for non-breaking waves. For the second approach, the found relations have a significant resemblance with the known formulae for run-up on a slope covered with rock armour units, derived by van der Meer and Starn. When the relations derived following the both approaches are compared, the relations derived by the second approach are the relations that give the best feeling with the physical processes as they occur. The relation for non-breaking waves, derived using the first approach, is applied on data obtained from physical model tests on a breakwater covered with tetrapod armour units. The calculated nondimensional run-up is compared with the measured non-dimensional run-up. The results show that the permeability of the whole structure can not be neglected, especially inthe case of non-breaking waves.Hydraulic EngineeringCivil Engineering and Geoscience
Coupling light to periodic nanostructures
No full textThis thesis describes coupling of light to periodic structures. A material is patterned with a regular pattern on a length scale comparable to the wavelength of light. With these structures, light can be manipulated very precisely. The structures find applications in semiconductor lasers, light emitting diodes (LEDs), photovoltaic cells, and detectors of light.
A periodic array of holes in a layer of semiconductor or in a thin metal film causes a coupling between the incident light and light that is trapped inside the layer. This coupling can be studied by measuring the reflection and transmission. The environment has an important role here; e.g. placing glass antennas in the holes can increase the coupling between light and plasmons.
A thin, superconducting wire can be used as a detector of light. To increase the surface area, the wire is folded into a meander. The optical properties of this detector are very dependent on the polarization, due to the regular periodic structure of the meander. Moreover, we found that the absorption of a very thin absorbing layer can be almost 100%, when it is illuminated under the right angle, from the substrate. This can be used to increase the efficiency of the detectors.LEI Universiteit LeidenUBL - phd migration 201
Electrodynamic response and local tunneling spectroscopy of strongly disordered superconducting TiN films
No full textWe have studied the electrodynamic response of strongly disordered superconducting TiN films using microwave resonators, where the disordered superconductor is the resonating element in a high-quality superconducting environment of NbTiN. We describe the response assuming an effective pair-breaking mechanism modifying the density of states and compare this to local tunneling spectra obtained using scanning tunneling spectroscopy. For the least disordered film (kFl=8.7, Rs=13 ?), we find good agreement, whereas for the most disordered film (kFl=0.82, Rs=4.3 k?), there is a strong discrepancy, which signals the breakdown of a model based on uniform properties.QN/Quantum NanoscienceApplied Science
One- and two-photon spectroscopy of a flux qubit coupled to a microscopic defect
No full textWe observed the dynamics of a superconducting flux qubit coupled to an extrinsic quantum system (EQS). The presence of the EQS is revealed by an anticrossing in the spectroscopy of the qubit. The excitation of a two-photon transition to the third excited state of the qubit-EQS system allows us to extract detailed information about the energy-level structure and the coupling of the EQS. We deduce that the EQS is a two-level system, with a transverse coupling to the qubit. The transition frequency and the coupling of the EQS changed during experiments, which supports the idea that the EQS is a two-level system of microscopic origin.Kavli Institute of NanoscienceApplied Science
Triggering elderly's behavior to an energy neutral and healthy use of the facade
No full textThe goal to achieve energy neutral buildings in 2020 is getting closer. To achieve energy neutral buildings, not only new buildings have to be innovative, also the existing building stock has to be improved in terms of energy efficiency. Besides that, the occupants have to be involved in this process too, in the end they have to use the façade in an energy efficient way. The purpose of this research was to find suitable solutions for the renovation of porch apartments in the Netherlands. The 2nd skin that will be applied in this design should not only be energy efficient, but should also trigger the occupants to use it in an energy efficient and healthy way. The target group on which these designs were tested are elderly. Because of their different deterioration aspects and the fact they have to live independently longer, we should make sure they are able to use this façade too (in an energy efficient and healthy way). This research has resulted in a few integrated final designs that mainly consist of two parts; a design for a home energy management system (HEMS) and a façade element design. The HEMS designs focus on how to trigger different user profiles of elderly to live energy neutral and besides that make elderly aware of the necessity to ventilate regularly (to improve the health of their indoor climate). The façade element mainly focuses on the comfort preferences of elderly and the improvement of their mental and physical health. Besides that of course the façade element meets the stricter rules regarding to the energy efficiency. All designs are projected on a reference project; the BAM 2nd skin project in Rotterdam. Several participating elderly gave me insight in their behavior and habits according to energy efficiency and comfort. The designs have been evaluated by them, the defined user profiles and a requirement list several times.Building TechnologyArchitecture and The Built Environmen
Numerieke berekeningen aan 3D-diffusieproblemen bij Thermische Desorptie-experimenten
No full textTechnische MateriaalwetenschappenMechanical, Maritime and Materials Engineerin
Microwave-induced nonequilibrium temperature in a suspended carbon nanotube
No full textAntenna-coupled suspended single carbon nanotubes exposed to 108?GHz microwave radiation are shown to be selectively heated with respect to their metal contacts. This leads to an increase in the conductance as well as to the development of a power-dependent DC voltage. The increased conductance stems from the temperature dependence of tunneling into a one-dimensional electron system. The DC voltage is interpreted as a thermovoltage, due to the increased temperature of the electron liquid compared to the equilibrium temperature in the leads.QN/Quantum NanoscienceApplied Science
Fabrication and performance verification of a 961 pixel Kinetic Inductance Detector system for future space borne observatories 9914-138
No full textAstronomical observations at infrared, sub-millimetre, and millimetre wavelengths are essential for addressing many of the key questions in astrophysics. Future ground- and space based observatories need large detector arrays with a sensitivity limited only by the noise of the radiation background. We demonstrate that antenna coupled Microwave Kinetic Inductance Detectors allow us to create kpixel large arrays with background limited sensitivity over the entire FIR/mmwavelength range. We discuss in detail the readout system and experimental results of a 961 pixel array, optimised for 850 GHz radiation that is read out with a single readout chain.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Tera-Hertz SensingQN/Quantum NanoscienceQN/Mol. Electronics & Device
Asymmetry reversal and waveguide modes in photonic crystal slabs
No full textThe measured reflection spectra of two-dimensional photonic crystal slabs consist of an asymmetric peak on top of an oscillating background. For p-polarized light, the asymmetry of the peak flips for angles of incidence beyond Brewster’s angle. We explain the observed line shapes with a Fano model that includes loss and use a waveguide model to predict the resonance frequencies of the photonic crystal slab. Finite-difference time domain calculations support the model and show that the resonance due to a higher order mode disappears when the substrate refractive index is increased beyond ns = 2.04. This is readily explained by the cut-off condition of the modes given by the waveguide model.NanofacilityApplied Science
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