<p>The cylinder liners surface is of major importance in an engine since it interacts with the piston rings and creates a tribologic system. This tribologic system has to be qualified and controlled in order to understand and control wear, oil consumption and shelf life. In this purpose, a program has been created in order to analyze SEM pictures and from them qualify the surface.</p><p>The aim of the project presented here has been to improve the preliminary steps leading to the image computation by standardizing the picture acquisition and improve the image filtering.</p>

Graduation date: 1998

The human visual system has the ability o utilize motion information to infer the shapes of surfaces. More specifically, we are able to derive descriptions of rigidly rotating smooth surfaces entirely from the orthographic projection of the motions of their surface markings. A computational analysis of this ability is proposed based on "shape from motion" proposition. This proposition states that given the first spatial derivatives of the orthographically projected velocity and the acceleration fields of a rigidly rotating regular surface, then the angular velocity and the surface normal at each visible point on that surface are uniquely determined up to a reflection.

In this thesis, we study the mathematical modelling of some problems that involve surface effects. These include an optical biosensor, which uses optical principles qualitatively to convert chemical and biochemical concentrations into electrical signals. A typical sensor of this type was constructed in Badley et al., [6], and Jones et al., [18],but diffusion was considered in only one direction in [18] to simulate the reaction between the antigen and the antibody. For realistic applications, we propose the biosensor model in R3. Our theoretical approach is explicitly presented since it is simple and directly applicable to the numerical part of the thesis. In particular, we present existence and uniqueness results based on Maximum Principle and weak solution arguments. These ideas are later applied to systems and to the numerical analysis of the approximate discretized problems.It should be noted that without one dimensional symmetry, the equations can not be decoupled in order to reduce the problem to a single equation. We also show the long time monotonic convergence to the steady state. Next, a finite volume method is applied to the equations, and we obtain existence and uniqueness for the approximate solution as well as the convergence of the the first order temporal norm and the L2 spatial norm. We illustrate the results via some numerical simulations. Finally we consider a mathematically related system motivated by lagoon ecology. We show that under suitable conditions on the coecients, the system has a periodic solution under harvesting conditions. The mathematical techniques now depend on estimates for periodic parabolic problems. / Applied Mathematics

Thesis (Ph.D.)--University of Delaware, 2006. / Principal faculty advisor: Eric W. Kaler, Dept. of Engineering. Includes bibliographical references.

Layer-by-layer assembly has received much attention over the last fifteen years. This assembly process can be carried out using different methods including hydrogen-bonding, electrostatic, and to a lesser extent, covalent interactions. However, these assemblies are rarely seen on polyolefin substrates due to the lack of functionality on the surface. “Click” chemistry has become very popular in recent years as a means to join modular compounds together. This thesis is the first published report to use “click” chemistry as a means for layer-by-layer assembly on a polymeric substrate. By designing polymers that contain alkyne or azide groups, it is possible to assemble them layer-by-layer on a polyethylene substrate. Polymers based on tert-butyl acrylate were initially designed for use in organic solvents such as tetrahydrofuran. The copper catalyst that facilitated the 1,3-dipolar cycloaddition was air sensitive and expensive. To capture the true essence of “click” chemistry, a new system was designed based on N-isopropyl acrylamide (NIPAM)-based polymers. These polymers were water soluble and allowed for “click” chemistry to be performed in water and open to air in benign conditions. With the development of a water soluble polymer system that could be modified to contain either azide groups or alkyne groups, layer-by-layer assembly was carried out in water. A polyethylene film was modified in a series of reactions to have an alkyne-functionalized surface. The poly(N-isopropyl acrylamide)-based polymers were layered in an alternating fashion to form multilayer assemblies. A series of control reactions were also performed, showing that these layers were interconnected via triazole linkages. These assemblies were monitored by attenuated total reflectance spectroscopy. Once the layers were assembled, the polyvalent nature of the polymers allowed for further functionalization. Various surface functionalizations were established using fluorescence microscopy and contact angle analysis. By using spectroscopic and chemical means, layer-by-layer assembly on polyethylene films was proven. Control reactions showed the necessity of components for triazole formation. Therefore, layer-by-layer assembly using “click” chemistry was achieved.

No description available.

Ellipsometry was used to study the effects of surface energetics and temperature on the equilibrium adsorptive behavior exhibited by β-lactoglobulin. β-Lactoglobulin isotherms at 25, 37, and 55°C were constructed for this purpose. The surfaces of acrylic, polycarbonate, polyester, glass, and #304 stainless steel were contacted with protein solutions of varying concentration, buffered at pH 6.7 with mono- and dibasic sodium phosphate. After three hours, the surfaces were mildly rinsed with deionized water and dried overnight. Optical properties of each film were ellipsometrically measured and the adsorbed mass was calculated as a function of film thickness and refractive index. Contact angle methods were used to measure the hydrophobicity exhibited by each of the five solid surfaces. However, interpretation of protein adsorption results based solely on solid surface hydrophobicity proved unworkable. For polymers (low-energy surfaces), the adsorbed mass of protein was explained with reference to the degree of extensibility of molecular structure. Glass (a high-energy surface) was observed to adsorb the greatest mass of β-lactoglobulin. Stainless steel was observed to adsorb the least mass of β-lactoglobulin and the plateau values of protein adsorption were found to be consistent with those reported elsewhere, and to lie within the range of adsorbed mass on metal surfaces in general. The temperature dependence of β-lactoglobulin adsorption could not be clearly quantified. Apparently, any differences in adsorbed mass were too small to be detected by the instrument. In any event, other investigators have not detected any significant difference in adsorbed mass as long as the temperature was below the denaturation temperature of the protein. / Graduation date: 1991

Scanning Tunneling Microscopy (STM) has been used to study the physisorption and chemisorption behaviour for three simple organic haloalkanes; 1,5 Dichloropentane (DCP), Bromomethane (CH3Br) and Chloromethane (CH3Cl)) on Si(100) 2x1, at temperatures ranging from 270 K to room temperature. The results were interpreted by Density Functional Theory (DFT) performed by collaborators at McGill University and the University of Liverpool. Physisorbed molecules of DCP were found to self assemble into stable lines aligned predominantly perpendicular to the Si dimer pair rows on the surface. A novel mechanism for line formation of Dichloropentane, termed, Dipole Directed Assembly (DDA), was elucidated by DFT calculations. For CH3Br three different patterns of dissociative attachment of reaction products (CH3 and Br/Cl) were observed, and assigned to three reaction pathways. These experimentally determined relative yields were used to obtain differences in reaction activation energy, Delta Ea, between the reaction pathways. These, in turn, were compared with computed differences in reaction barriers, Delta Eb, obtained ab initio for the same pathways by DFT. For CH3Cl, two single-molecule patterns of attachment were found, and a new reaction pathway for attaching CH3Cl in long chains of alternating CH3 and Cl was discovered. The mechanisms for chain growth were determined experimentally by examination of single molecular steps. This mechanism was explained ab initio by DFT to be the result of relative barrier heights for the possible chain-growth pathways.

Scanning Tunneling Microscopy (STM) has been used to study the physisorption and chemisorption behaviour for three simple organic haloalkanes; 1,5 Dichloropentane (DCP), Bromomethane (CH3Br) and Chloromethane (CH3Cl)) on Si(100) 2x1, at temperatures ranging from 270 K to room temperature. The results were interpreted by Density Functional Theory (DFT) performed by collaborators at McGill University and the University of Liverpool. Physisorbed molecules of DCP were found to self assemble into stable lines aligned predominantly perpendicular to the Si dimer pair rows on the surface. A novel mechanism for line formation of Dichloropentane, termed, Dipole Directed Assembly (DDA), was elucidated by DFT calculations. For CH3Br three different patterns of dissociative attachment of reaction products (CH3 and Br/Cl) were observed, and assigned to three reaction pathways. These experimentally determined relative yields were used to obtain differences in reaction activation energy, Delta Ea, between the reaction pathways. These, in turn, were compared with computed differences in reaction barriers, Delta Eb, obtained ab initio for the same pathways by DFT. For CH3Cl, two single-molecule patterns of attachment were found, and a new reaction pathway for attaching CH3Cl in long chains of alternating CH3 and Cl was discovered. The mechanisms for chain growth were determined experimentally by examination of single molecular steps. This mechanism was explained ab initio by DFT to be the result of relative barrier heights for the possible chain-growth pathways.