The exponential growth of Internet applications has created new challenges for the control and administration of large-scale networks, which consist of heterogeneous elements under dynamically changing traffic conditions. These emerging applications need guaranteed service levels, beyond those supported by best-effort networks, to deliver the intended services to the end user. Several models have been proposed for a Quality of Service (QoS) framework that can provide the means to transport these services. It is desirable to find efficient routing strategies that can meet the strict routing requirements of these applications. QoS routing is considered as one of the major components of the QoS framework in communication networks. In QoS routing, paths are selected based upon the knowledge of resource availability at network nodes and the QoS requirements of traffic. Several QoS routing schemes have been proposed that differ in the way they gather information about the network state and the way they select paths based on this information. The biggest downside of current QoS routing schemes is the frequent maintenance and distribution of global state information across the network, which imposes huge communication and processing overheads. Consequently, scalability is a major issue in designing efficient QoS routing algorithms, due to the high costs of the associated overheads. Moreover, inaccuracy and staleness of global state information is another problem that is caused by relatively long update intervals, which can significantly deteriorate routing performance. Localized QoS routing, where source nodes take routing decisions based solely on statistics collected locally, was proposed relatively recently as a viable alternative to global QoS routing. It has shown promising results in achieving good routing performance, while at the same time eliminating many scalability related problems. In localized QoS routing each source¿destination pair needs to determine a set of candidate paths from which a path will be selected to route incoming flows. The goal of this thesis is to enhance the scalability of QoS routing by investigating and developing new models and algorithms based on the localized QoS routing approach. For this thesis, we have extensively studied the localized QoS routing approach and demonstrated that it can achieve a higher routing performance with lower overheads than global QoS routing schemes. Existing localized routing algorithms, Proportional Sticky Routing (PSR) and Credit-Based Routing (CBR), use the blocking probability of candidate paths as the criterion for selecting routing paths based on either flow proportions or a crediting mechanism, respectively. Routing based on the blocking probability of candidate paths may not always reflect the most accurate state of the network. This has motivated the search for alternative localized routing algorithms and to this end we have made the following contributions. First, three localized bandwidth-constrained QoS routing algorithms have been proposed, two are based on a source routing strategy and the third is based on a distributed routing strategy. All algorithms utilize the quality of links rather than the quality of paths in order to make routing decisions. Second, a dynamic precautionary mechanism was used with the proposed algorithms to prevent candidate paths from reaching critical quality levels. Third, a localized delay-constrained QoS routing algorithm was proposed to provide routing with an end-to-end delay guarantee. We compared the performance of the proposed localized QoS routing algorithms with other localized and global QoS routing algorithms under different network topologies and different traffic conditions. Simulation results show that the proposed algorithms outperform the other algorithms in terms of routing performance, resource balancing and have superior computational complexity and scalability features. / Umm AlQura University, Saudi Arabia

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The first thermal cycling experiments of ionic self-assembled multilayer (ISAM) films have been reported examining their survivability through repeated thermal cycles from -20° C to 120° C in ambient atmospheric conditions. The films were constructed from alternating layers of Nile Blue A and gold nanoparticles which provided a strong absorbance in the optical wavelength range. No degradation of the optical characteristics of the ISAM films was observed [1]. Techniques for measuring the capacitance and resistivity of various ISAM films have also been developed allowing for a more complete electrical characterization of ISAM films. Capacitance measurements enabled a calculation of the dielectric function and breakdown field strength of the ISAM films. The capacitance measurement technique was verified by measuring the dielectric function of a spin-coated thin film PMMA, which has a well characterized dielectric function [2]. Surface-enhanced Raman spectroscopy (SERS) has been studied as a possible detection method for malignant melanoma revealing spectral differences in blood sera from healthy horses and horses with malignant melanoma. A SERS microscope system was constructed with the capability of resolving the Raman signal from biologically important molecules such as beta-carotene and blood sera. The resulting Raman signals from sera collected from horses with malignant melanoma were found to have additional peaks not found in the Raman signals obtained from sera collected from healthy horses. A systematic analysis of the combination of absorbance and fluorescence signals of blood sera collected from populations of healthy dogs and dogs with cancer has resulted in a rapid and cost-effective method for monitoring protein concentrations that could possibly be used as part of a cancer screening process. This method was developed using the absorbance and fluorescence signals from known serum proteins, the combinations of which were used to match the absorbance and fluorescence signals of blood sera allowing for an accurate determination of protein concentrations in blood sera [3]. Finally, a novel method for measuring the melting point of DNA in solution using capacitance measurements is presented. This method allows for the determination of the melting temperature as well as the melting entropy and melting enthalpy of DNA strands. Two different short strands of DNA, 5'-CAAAATAGACGCTTACGCAACGAAAAC-3' along with its complement and 5'-GGAAGAGACGGAGGA-3' along with its complement were used to validate the technique as the characteristics of these strands could be modeled using theoretical methods. This experimental technique allows for the precise determination of the melting characteristics of DNA strands and can be used to evaluate the usefulness of theoretical models in calculating the melting point for particular strands of DNA. Additionally, a micro-fluidic device has been proposed that will allow for a rapid and cost-effective determination of the melting characteristics of DNA [4]. / Ph. D.

Localized muscle fatigue (LMF) has been proposed as a surrogate measure to injury, since the onset of fatigue is rapid rather than months or years required to the onset of work related musculoskeletal disorders (WMSDs). The objectives of this study were to estimate LMF and quantify muscle activity of select forearm muscles during simulations of high pressure cleaning lance tasks common in the chemical production industry. Twenty participants, twelve males and eight females, with no musculoskeletal injuries and meeting criteria for upper extremity fitness, performed the simulated task. Independent variables studied include work height (shoulder, waist, and knuckle), lance orientation (parallel to the operator and parallel to the ground), and duty cycle (33, 50, and 67%) based on task analyses of actual work tasks. Dependent variables included mean RMS and rates of change in mean RMS, mean and median power frequency, MVE, and subjective ratings of fatigue. Repeated measures ANOVA was used to test the main effects of the independent variables and appropriate interactions. In general it was found that working at waist height, at higher duty cycles, and with the lance oriented parallel to the operator resulted in higher fatigue measures. Subjective ratings of fatigue were not well correlated with objective measures, similar to findings in previous studies. The simulated task was found to be extremely fatiguing and modifications to task design or job rotation schedules are required to reduce risk associated with injury development. / Master of Science

In this dissertation, I have verified that the striking purple color of the intermetallic compound AuAl₂, also known as purple gold, originates from surface plasmons (SPs). This contrasts to a previous assumption that this color is due to an interband absorption transition. The existence of SPs was demonstrated by launching them in thin AuAl2 films in the Kretschmann configuration, which enables us to measure the SP dispersion relation. I observed that the SP energy in thin films of purple gold is around 2.1 eV, comparable to previous work on the dielectric function of this material. Furthermore, SP sensing using AuAl₂ also shows the ability to measure the change in the refractive index of standard sucrose solution. AuAl₂ in nanoparticle form is also discussed in terms of plasmonic applications, where Mie scattering theory predicts that the particle bears nearly uniform absorption over the entire visible spectrum with an order magnitude higher than a lightabsorbing carbonaceous particle. The second topic of this dissertation focuses on plasmon enhanced fluorescence in gold nanoparticles (Au NPs). Here, I investigated the distance-dependent fluorescence emission of rhodamine green 110 fluorophores from Au NPs with tunable spacers. These spacers consist of polyelectrolyte multilayers (PEMs) consisting of poly(allylamine hydrochloride) and poly(styrene sulfonate) assembled at pH 8.4. The distance between Au NPs and fluorophores was varied by changing the ambient pH from 3 to 10 and back, which causes the swelling and deswelling of PEM spacer. Maximum fluorescence intensity with 4.0-fold enhancement was observed with 7-layer coated Au NPs at ambient pH 10 referenced to pH 3. The last topic of this dissertation examines a novel approach to assemble nanoparticles, in particular, dimers of gold nanospheres (NSs). 16 nm and 60 nm diameter NSs were connected using photocleavable molecules as linkers. I showed that the orientation of the dimers can be controlled with the polarization of UV illumination that cleaves the linkers, making dipolar patches. This type of assembly provides a simple method with potential applications in multiple contexts, such as biomedicine and nanorobotics. / PHD / This dissertation covers three related topics. The first is an investigation of the optical properties of the unusually colored purple gold, which is a blend of gold and aluminum with the chemical formula is AuAl₂. This compound is interesting in that the origin of this color is different from most other metals. In the case of gold, for example, the metal gold is yellow color by absorbing the blue component from white light, leaving behind yellow color reflected light. The blue light is absorbed by electrons that change their state from a lower energy to a higher one. In purple gold, the color results from a different phenomenon known as “surface plasmons.” Surface plasmons are waves consisting of many electrons that move back and forth near an interface between a metal and an electrical insulator. The energy of surface plasmons in purple gold is low and corresponds to the purple color in this compound. Recently, published theoretical work supports the possibility of surface plasmons in purple gold. In this dissertation, I experimentally verify the presence of surface plasmons in purple gold. To launch surface plasmons, light was reflected off of a purple gold film deposited on the hypotenuse of a prism with varying angles of incidence. Surface plasmons can be observed by the sudden dimming of reflected light. From this, I was able to extract the surface plasmon dispersion relation, which is the relation between the inverse of the wavelength and the energy of the surface plasmons. In addition, I computed the light absorption properties of purple v gold when it is used in a nanoparticle form. The computational result showed that small purple gold nanoparticles absorb light very well, which may be useful in photothermal cancer therapy and solar steam generation. The second dissertation topic comprises a study of fluorescent molecules. These are compounds that reemit light with a different and redder color than the color of the light that illuminates them. In this experiment, green fluorescent molecules were placed near the surface of gold nanoparticles to observe how the brightness of the light emission is affected by the distance between the molecule and the metal. The underlying mechanism is based on localized surface plasmon resonances in gold nanoparticles. Localized surface plasmon resonances are waves consisting of many electrons that oscillate inside the particle, and they only occur when light at certain frequency illuminate the particle. On the resonance, the particle also exhibits the brighter light around the particle’s surface but the dimmer light away from the particle’s surface. The light enhancement from the particle can change the light emission of the fluorescent molecules. If the fluorescent molecules were placed in the range of localized surface plasmon resonances, the light emission is increased owing to the brighter light from the particle. However, if the fluorescent molecules were placed further away from the range of localized surface plasmon resonances, the light emission is decreased owing to the dimmer light from the particle. The distance between the surface of gold nanoparticle and the fluorescent molecules was varied by wrapping the gold particles with ultra-thin films of different plastic polymers before attaching fluorescent molecules to the surface of the films. These polymer films have the property that they swell and shrink when the acidity and basicity of the solution of gold particles changes, which allows me to vary the distance between the gold particles and fluorescent molecules. The results showed that the observed light gets dimmer when the solution is more acidic. On the other hand, the brighter light is noticed when the solution is more basic, and this observation is repeatable many times. Moreover, my work differs from other published works vi in that the particles with the polymer films are more robust and stable than the other particles. This allows more design flexibility and suggests applications in biomedical or environmental research where the particles can be used to locally measure properties, such as acidity in confined spacers such as living cells. It may be possible to use this technique for tumor cells in our body or toxic pollutants in the air or water. The last dissertation topic involves assembling nanoparticles to build them into larger structures. In this experiment, I fabricated particle dimers that consisted of two gold nanospheres of different sizes. They were attached together by using small molecules that are sensitive to ultraviolet (UV) light, where these molecules allow small gold nanospheres to be attached to large gold nanospheres only in those locations on the large nanospheres that have been illuminated with a sufficient amount of UV light. To achieve this alignment, UV light with a linear polarization (a specific electric field direction) was used to select the area on the large nanospheres where the UV light was particularly intense and therefore able to break the molecules, leaving positively charged surface patches on the spheres. This results in the electrostatic attraction between the positive patches on the large gold nanospheres and the negatively charged small gold nanospheres. With this method, I was able to make dimers of nanospheres in a preferred alignment by changing the polarization of UV light. The experimental results showed a good yield of dipolar patches, which allows multifunctional nanostructures with applications in nanomedicine, optical sensing, nanoelectronics, etc.

The increase in the magnitude of local electric fields through resonances of plasmonic excitations in metallic nanoparticles is a major area of current optical research. This dissertation is focused on plasmon-enhanced second harmonic generation of organic ionic self-assembled films via localized surface plasmon resonance of gold nanorods. By matching the plasmon resonance of the gold nanorods to the wavelength of the fundamental light, it is possible to greatly enhance the SHG efficiency. To demonstrate this, the surface of the gold nanorods was functionalized with a nonlinear-optical (NLO) polymer, PCBS, via the layer-by-layer method and deposited on a polymer thin film created on a glass substrate using the ionic self-assembled multilayer (ISAM) method. The sample fabrication is divided into two parts: gold nanorod synthesis and functionalization. The gold nanorods were synthesized by the seed-mediated method with varying amounts of silver ions to control their LSPR wavelengths. The functionalization started by replacing the original thick CTAB bilayer on the surface of the gold nanorods by a thin PAH-DTC layer via dialysis. The nanorods were then alternately coated with PAH (polycation) and PCBS (NLO polyanion) up to three bilayers of PAH/PCBS. The number of polymer layers on the nanorods was chosen in consideration of the LSPR decay length (a few nm). The functionalized gold nanorods were then deposited on either PAH/PCBS or PAH/PSS ISAM films. Characterization was performed via optical spectral measurement, zeta potential measurement, and field-emission scanning electron microscopy (FESEM). The LSPR wavelength shifted when the surrounding medium changed. It was red-shifted for each added polymer layer on the nanorod surface. However, when the functionalized nanorods were deposited on the ISAM film, the resonance peak blue-shifted. The zeta potential confirmed the proper electric charge of each polymer layer coated on the nanorods. Finally, FESEM was performed on the samples for visual inspection of the nanorod deposition and distribution after the SHG measurement was complete. The SHG from the functionalized gold nanorods was measured using a Maker-like fringe method. In this method, second harmonic waves generated from the front and rear sides of the substrate interfere constructively and destructively when the sample is rotated with respect to the incoming pump wave. Electrical noise reduction techniques were implemented to improve the SHG signal readings. Signal processing was implemented using LabVIEW software in order to read a reliable SHG signal from the setup. The maximum tolerable fluence of the gold nanorods was determined in order to prevent optical damage. The interference fringe pattern was observed from the functionalized gold nanorods and compared with that from the conventional ISAM film. The enhancement from the gold nanorods was as high as 600 times compared to the bare films. Polarization dependent SHG measurements were conducted to ascertain the effect of coupling between p- or s-polarized fundamental incident light to the SH light. To further improve the SHG enhancement, the self-assembly method herein can be extended from a monolayer to multilayers of functionalized gold nanorods. / Ph. D. / The field of optics examines the interactions of light and matter. The most commonly observed optical phenomena are the reflection and refraction of light where the frequency of light remains unchanged. However, when light becomes intense, interesting optical phenomena occur where the frequency of the outgoing light differs from that of the incoming light. With the invention of the first working laser in 1960, many interesting nonlinear phenomena were experimentally confirmed, including second harmonic generation (SHG) which was the first nonlinear optical process to be observed. In the original SHG experiment, a visible ruby laser was illuminated into a quartz crystal which produced UV light. This demonstrated light frequency doubling corresponding to wavelength halving from 694 nm (ruby laser) to 347 nm (UV light). Following progress in molecular engineering, many organic materials and polymers have been employed to study nonlinear optics for applications such as optical frequency conversion, electro-optic modulation, and second harmonic generation imaging microscopy. Nonetheless, the SHG conversion efficiency is very low due to phase-mismatch. This stems from frequency dispersion in a medium, where the incoming light and the generated light travel at different velocities. In the past, efforts toward enhancing the SHG conversion efficiency was focused on selecting specific crystals in which the incoming light and the second harmonic light pass through different effective path lengths in the medium. Although the phase-matching method is the most effective method to achieve high conversion efficiency it is also important to increase the intrinsic nonlinearity of a material. A new multidisciplinary approach using the surface plasmon resonance has become an important technique for improving the conversion efficiency. Plasmons are the collective oscillation of electrons on a metal surface. At the resonant optical frequency, the amplitude of the plasmon oscillation becomes maximized. When metallic nanoparticles are resonantly illuminated with light, the electric field can be locally intensified at the sharp boundaries of the nanoparticle. Since the intensity of SHG increases by the square of the incoming light intensity, the SHG efficiency can be greatly enhanced via surface plasmons on the metal nanoparticles. In this dissertation, the fabrication of new optical materials incorporating gold plasmonic nanoparticles for SHG enhancement was demonstrated. The plasmonic nanomaterials were fabricated by coating the surface of gold nanorods with nonlinear polymer films and depositing them on another polymer thin film on a flat glass substrate. The enhanced SHG intensity was measured and compared with that of the conventional nonlinear polymer films alone. It was observed that the enhancement from the gold nanorods was as high as 600 times. To further improve the SHG enhancement, the surface modified gold nanorods can be extended from a single layer to multilayers on the polymer film substrate.