No / Porous road surfaces offer an effective means of reducing the generation and propagation of noise from road traffic. However, the porosity of these surfaces can deteriorate over time, leading to a reduction in their noise reducing properties. Efficient methods are therefore required for monitoring this performance. Existing techniques for performing in-situ measurements of acoustic absorption are unsuitable for use within the traffic stream. Static measurements using time domain Maximum Length Sequence (MLS) based techniques have been demonstrated to offer advantages over traditional techniques, presenting the opportunity for measurements under dynamic conditions. This paper describes the design of a system for carrying out dynamic MLS-based measurements. Results are presented which demonstrate that stable dynamic measurements can be carried out at speeds of up to 30 km/h.

Geometric trimming of a surface involves removal of unwanted portions of the surface and providing a new mathematical description for the trimmed patch. This entails creating a new geometry for the trimmed patch, which closely approximates the corresponding portion on the original patch. The procedure is shown to involve obtaining data points on the B-spline surface that lie within the region specified by the parameter values for the trimming curve and describing a new surface which interpolates this new set of data points. This research looks at optimizing the procedure described above by basing the choice of parameter values for the trimming curve, at points where curvature optima occur over the surface. A visualization tool kit has been developed using OpenGL, as a means to discern the difference between the two surfaces. In order to quantify and aid in minimizing the error (difference) in approximating the original surface with the trimmed patch, an error measurement tool developed in MATLAB has been employed. / Master of Science

published_or_final_version / Physics / Doctoral / Doctor of Philosophy

Thesis (M. Phil.)--University of Hong Kong, 1992.

Sulfur adsorbed on metallic and oxide surfaces, whether originating from gaseous environments or segregating as an impurity to metallic interfaces, is linked to the deterioration of alloy performance. This research dealt with investigations on the interactions between sulfur and iron or iron alloy metallic and oxide surfaces under ultrahigh vacuum conditions. Sulfur was either intentionally dosed from a H2S source on an atomically clean metal surface, or segregated out as an impurity from the bulk to the metal surface by annealing at elevated temperatures.

Development of repellent surfaces which can supress bacteria adhesion, blood contamination and thrombosis, and non-specific adhesion on diagnostic devices has been a topic of intense research as these characteristics are in high demand. This thesis focused on design and development of omniphobic surfaces based on hierarchical structures and their application for preventing pathogenic contamination and biosensing. First, a flexible hierarchical heat-shrinkable wrap featuring micro and nanostructures, was developed with straightforward scalable methods which can be applied to existing surfaces. These surfaces reduced biofilm formation of World Health Organization-designated priority pathogens as well as minimized risk of spreading contamination from intermediate surfaces. This is due to the broad liquid repellency and the presence of reduced anchor points for bacterial adhesion on the hierarchical surfaces. Next, the developed surfaces were applied to minimize blood contamination and clot formation as well as facile integration of hydrophilic patterns. This led to droplet compartmentalization and was utilized for detection of Interleukin 6 in a rapid dip-based assay. Furthermore, in a review article the need for anti-viral or virus repellent surfaces and future perspectives were discussed as the global COVID-19 pandemic surged and attracted interest toward innovative technologies for suppressing the spread of pathogens. To address the pressing issue of non-specific adhesion in diagnostics devices, an omniphobic liquid infused electrochemical biosensor was developed. This was achieved by electroplating gold nanostructures on fluorosilanized gold electrodes. These electrodes demonstrated rapid and specific detection of Escherichia coli within an hour in complex biological liquids (blood, urine, etc.) without dilutions or amplification steps from clinical patient samples which are major bottle necks when rapid detection systems are sought for at the point of care. / Thesis / Doctor of Philosophy (PhD) / Repellent surfaces have a variety of applications in healthcare, for coating medical devices (e.g. indwelling implants, stethoscopes, and other external devices.), coating hospital surfaces for blood and pathogen repellency, and for developing anti-fouling diagnostic devices. Furthermore, they can be applied in the food sector for limiting contaminations, and in public areas on high-touch surfaces to eliminate the spread of infection. Therefore, there is a need for repellent surface which can be easily applied to surfaces with various form factors while having an easy fabrication method. Featuring hierarchical structures on a heat-shrinkable material, a repellent wrap was designed to be integrated on existing surfaces and repel pathogens and suppress the spread of infection as an intermediate surface. Similar concept was used for designing blood repellent surfaces which were patterned with hydrophilic regions for a rapid dip-based biosensing platform. Finally, surface textures on conductive materials with liquid infused repellent coatings were investigated for electrochemical biosensing in complex biological liquids.

This study aimed at understanding the adhesion between wood fibers and thermoplastics. Direct applications include the development of better wood fiber composites and better paper coatings. The objectives of the study were two-fold. First, to quantify the effects of surface treatments on the surface properties, and, second, to determine if adhesion can be described in terms of surface properties. A model consisting of amorphous cellulose spherical beads was used to eliminate the effects of morphology, composition, and fiber size and orientation; adhesion was studied only in terms of surface properties. The surface of the cellulose beads was modified by blending, by coating or by chemical surface reaction. Surface modification by blending was achieved by dissolving cellulose along with another polymer (cellulose propionate) and by beading the mixed solution. An alternative consisted of coating the beads with a thin layer of polymer, such as poly(4-vinyl-pyridine-co-styrene). Finally the surface was also modified by grafting functional groups or polymer segments onto the hydroxyl groups of cellulose. A thin layer of cellulose derivative, such as cellulose trifluoroethoxyacetate or cellulose laurate was produced on the bead surface. Polystyrene and polypropylene segments were grafted onto cellulose to create an interphase. The surface properties of the cellulose beads were then fully characterized. The surface composition was analyzed by X-ray Photoelectron Spectroscopy (XPS), and the morphology was investigated through Scanning Electron Microscopy. Inverse Gas Chromatography (IGC) was used to measure the surfaces' energetics. Two kinds of probes were used: alkanes to measure the dispersive component of adhesion, and acid/base probes to quantify the specific properties. Composites having variable bead content were made by injection molding. The adhesion between the cellulose beads and the thermoplastics were measured by tensile testing and by DMTA using the modified Nielsen Model with the damping factor (tan δ). The surface energy of cellulose was found to depend mostly on the presence and concentration of free hydroxyl groups on the surface. For low degrees of substitution (DS), how these OH groups are replaced by modification, whether by fatty acid type substituents or by fluorine-containing groups, is essentially irrelevant for surface characteristics. The dispersive component of the surface energy (γs^D) declined with DS, almost irrespective of substituent type. The acidic character of the cellulose surface is attributed mainly to the presence of hydroxy groups. It was furthermore established that, while wetting is a necessary condition, it is in itself insufficient for achieving good adhesion and adequate composite strength characteristics. The mechanical properties of polyethylene, polypropylene and polystyrene all decreased as cellulose beads were added in increasing amounts. It was found that improved cellulose fiber-reinforced composite performance requires the development of an interphase, such as by grafting polymer segments onto the cellulose surface which are capable of entanglement with the thermoplastic polymer in the melt. Maleic anhydride/polypropylene copolymers were found to be efficient coupling agents that better transmit stress when their molecular size increased. Adsorption of poly(4-vinylpyridine-co-styrene) [basic] by the cellulose beads [acidic] resulted in completely coated surfaces. However, strength differences between composites, with coated and uncoated beads, were insignificant probably owing to the large bead sizes used. / Ph. D.

The primary focus of this study is the reduction of sensitivity to contamination of the battery pack surfaces. During the project, information on adhesion mechanisms that cause particles to accumulate on surfaces has been collected through literature research. This has been done to create a fundamental understanding regarding the factors that affect dust and particle accumulation. In addition, an in-depth study of articles concerning the modification of surface structure has been carried out. In connection with the literature study, an experimental analysis was carried out where a number of surfaces provided by Scania were examined to understand their structure and properties. This was done in order to identify suitable surface treatments/methods that could be applied. The experimental results show that all the surfaces consist of only micro-level structures. Two of the samples showed increased risk for dust accumulation due to one of them having a step profile and the other having a wavy surface structure with peaks and valleys. Previous research suggests that surfaces that are structured on the micro- and nano-level are essential to achieve dust- and particle-free/repellent surfaces. By structuring surfaces at the micro- and nano-level, a so-called hierarchical structure inspired by the natural self-cleaning mechanisms of the lotus leaf can be achieved. This results in surfaces with a high water contact angle and low surface energy, which contribute to minimized adhesion forces and in turn particle repellent surfaces.

Une surface K3 est une surface X complexe compacte projective lisse qui a fibré canonique trivial et h0;1(X) = 0. Dans cette thèse on s'intéresse à deux problèmes pour ces surfaces. D'abord on considère des surfaces K3 obtenues comme recouvrement double de P2 ramifié le long d'une sextique. On classifie les fibrations elliptiques sur ces surfaces et leur groupe de Mordell-Weil, c'est-à-dire le groupe des sections. Vu que une section de 2-torsion définit une involution de la surface (dite involution de van Geemen-Sarti), alors en classifiant les fibrations et les section de 2-torsion on obtient une classification complète des involutions de van Geemen-Sarti sur ce type de surfaces K3. On montre aussi comment calculer l'équation de la fibration et on étudie le quotient par l'involution de van Geemen-Sarti. Ensuite on montre la construction de Berglund-Hübsch-Chiodo-Ruan (BHCR): il s'agit d'une construction miroir qui part d'un polynôme dans un espace projectif à poids et d'un groupe d'automorphismes (avec certaines propriétés) et qui donne, en toute dimension, des paires de variétés Calabi-Yau. Ces deux variétés sont l'une miroir de l'autre en sense classique. On classifie toutes les paires de surfaces K3 obtenues avec cette construction qui aient en plus un automorphisme non{symplectique d'ordre premier p > 3. Pour les surfaces K3 une autre notion de symétrie miroir a été introduite par Dolgachev et Nikulin : la symétrie pour K3 polarisées (LPK3). On montre dans la thèse comment polariser les surfaces obtenues avec la construction BHCR et on preuve que deux surfaces miroir au sense BHCR, dûment polarisées, appartiennent à deux familles miroir LPK3. / A K3 surface is a complex compact projective surface X which is smooth and such that its canonical bundle is trivial and h0;1(X) = 0. In this thesis we study two different topics about K3 surfaces. First we consider K3 surfaces obtained as double covering of P2 branched on a sextic curve. For these surfaces we classify elliptic fibrations and their Mordell-Weil group, i.e. the group of sections. A 2-torsion section induces a symplectic involution of the surface, called van Geemen-Sarti involution. The classification of elliptic fibrations and 2-torsion sections allows us to classify all van Geemen-Sarti involutions on the class of K3 surfaces we are considering. Moreover, we give details in order to obtain equations for the elliptic fibrations and their quotient by the van Geemen-Sarti involutions. Then we focus on the mirror construction of Berglund-Hübsch-Chiodo-Ruan (BHCR). This construction starts from a polynomial in a weighted projective space together with a group of diagonal automorphisms (with some properties) and gives a pair of Calabi-Yau varieties which are mirror in the classical sense. The construction works for any dimension. We use this construction to obtain pairs of K3 surfaces which carry a non-symplectic automorphism of prime order p > 3. Dolgachev and Nikulin proposed another notion of mirror symmetry for K3 surfaces: the mirror symmetry for lattice polarized K3 surfaces (LPK3). In this thesis we show how to polarize the K3 surfaces obtained from the BHCR construction and we prove that these surfaces belong to LPK3 mirror families.

Le manque croissant en eau potable dans le monde est un problème d’envergure pour la population. La filtration par des membranes des eaux usées, insalubres ou la désalination apparaît comme une alternative viable pour le futur. La modification de membranes d’ultrafiltration par l’assemblage couche-par-couche permet d’obtenir des propriétés de nanofiltration en contrôlant avec une précision nanométrique l’épaisseur de la couche active de séparation déposée. Lors de cette thèse, nous avons étudié la construction de la couche de séparation ainsi que sa régénérabilité. Pour ce faire, nous avons développé des surfaces « membrane-like » pour étudier la construction sur des surfaces possédant des fonctions chimiques similaires à l’applicative. Par ailleurs, le temps de déposition a aussi été investigué afin de déterminer si les propriétés de séparation des membranes modifiées dépendaient du nombre de couches déposé ou du temps de dépôt. Les membranes ainsi développées présentent une couche de séparation régénérable et des propriétés de nanofiltration. / The increasing lack of drinking water in the world is of major concern for the population. Membrane filtration of brackish water, seawater appears to be a viable alternative for the future. Nanofiltration membranes can be obtained by modifying ultrafiltration membranes by the Layer-by-Layer (LbL) technique. This method also the deposition of an ultra-thin separation layer with a nanoscale precision and with tunable properties. During this PhD thesis, the build-up and the regenerability of the separation layer was investigated. For this purpose, mimicry surfaces were developed in order to study the LbL-assembly on surfaces presenting similar chemical functions as the applicative one. In addition, the deposition time was also investigated in order to determine if the separation properties of the membrane depend on the number of deposited layers or on the coating time. The developed membranes possessed a regenerable separation layer presenting nanofiltration properties.