Analysis of EM wave scattering from asphalt and its application to automotive radar

The driver’s safety is one of the problems that is considered by modern vehicle technologies. Many accidents occur due to extreme weather conditions, such as snow or freezing rain. Such weather causes decreases in the friction of the road surface, which cause danger for drivers in this kind of area. To improve the driver’s safety, ADAS (Advanced...

Machine learning for the prediction of the local skin friction factors and Nusselt numbers in turbulent flows past rough surfaces

Turbulent flows past rough surfaces can create substantial energy losses in engineering equipment. During the last decades, developing accurate correlations to predict the thermal and hydrodynamic behavior of rough surfaces has proven to be a difficult challenge. In this work, we investigate the applicability of convolutional neural networks...

Systematic errors observed in CryoSat-2 elevation swaths on mountain glaciers and their implications

Our awareness of ice caps' and mountain glaciers' sensitivity to climate change has driven major advances in the application of remote sensing techniques during the past decade. Regarding ESA's SARIn altimeter CryoSat-2, processing the full waveform to generate swaths of elevation estimates has become standard practice in regions of complex...

Rough-Surface Polarimetry in Companion SAR Missions

Bistatic scattering from rough surfaces is typically approached through the analysis of the scattered field in the conventional H and V polarization basis, which coincides with the zenith and azimuth unit vectors in a spherical reference frame. This study delves into the impacts of different choices of the transmit and receive linear basis on...

Learning to Feel Textures: Predicting Perceptual Similarities From Unconstrained Finger-Surface Interactions

Whenever we touch a surface with our fingers, we perceive distinct tactile properties that are based on the underlying dynamics of the interaction. However, little is known about how the brain aggregates the sensory information from these dynamics to form abstract representations of textures. Earlier studies in surface perception all used...

Dynamic Road Surface Signatures in Automotive Scenarios

A method to compute road surface signatures in the automotive scenario is presented. This method is subsequently applied to a rough asphalt surface without undulations. It is shown that, due to the observation geometry, the road surface signature experiences significant spreading along the Doppler-axis, resulting in a distinct range-Doppler map...

Lubrication of rough copper with few-layer graphene

It has been demonstrated through experiments and simulations that friction decreases significantly when graphene is used as a solid lubricant on various materials. However, the effect of increasing the number of graphene layers on lubrication is controversial. Some studies predict an increase of friction with the number of layers that can be...

On sub-surface stress caused by contact roughness in compressible elastic solids

Contact between elastic bodies with self-affine rough surfaces is mostly studied with a focus on determining surface fields, despite body fields are of great importance to establish, for instance, when and where elasticity breaks down. This work aims at analyzing the effect of contact roughness on the body fields of compressible frictionless...

Modelling adhesion and friction in contact problems

The main objective of this thesis is to obtain a better understanding of adhesive contacts and their frictional behaviour. Both natural and man-made surfaces are rough over a wide range of length scales. Tribological studies of rough surfaces need to account for the interactions between these asperities. In this work a sim- ple atomistically...

Plastic deformation of self-affine rough metal surfaces under contact loading: A green’s function dislocation dynamics analysis

On the proportionality between area and load in line contacts

The relative contact area of rough surface contacts is known to increase linearly with reduced pressure, with proportionality factor κ. In its common definition, the reduced pressure contains the root-mean-square gradient (RMSG) of the surface. Although easy to measure, the RMSG of the entire surface does not coincide, at small loads, with...

Plasticity under rough surface contact and friction

The ultimate objective of this work is to gain a better understanding of the plastic behavior of rough metal surfaces under contact loading. Attention in this thesis focuses on the study of single and multiple asperities with micrometer scale dimensions, a scale at which plasticity is known to be size dependent. The asperities have very simple...

UWB Near-Range GPR Phase-Based Techniques for Profiling Rough Surfaces and Detecting Small Low-Contrast Shallow Subsurface Objects