For the application of advanced hydrogel-based artificial muscle systems, conventional polymeric hydrogels usually suffer from various limitations such as structural inhomogeneity and poor mechanical strengths. Thus, improving the mechanical strength of a specific hydrogel system while maintaining its other useful properties become increasingly important. In this project, three different approaches were employed to improve the mechanical properties of hydrogels though microstructural control, including physical cross-links, copolymerisation, and interpenetrating systems. Analytical tools such as FTIR and XRD were used to confirm the success of sample preparation. Morphological SEM characterisations were applied to reveal direct graphic information on hydrogels microstructures. Equilibrium water swelling tests as well as uniaxial compression measurements were conducted to evaluate the influences of various experimental parameters on the hydrogels water-holding and mechanical properties. The physical cross-linker approach was proved to be successful since comparable swelling capacities and dramatically enhanced mechanical strength were achieved in nanocomposite systems in comparison with conventional chemically cross-linked gel systems, due to the presence of flexible cross-linking points and the multifunctional cross-linker role played by clay. The copolymerisation approach, both between two neutral monomers and between one neutral and the other ionic monomer, was unsuccessful in terms of mechanical property enhancement due to the low cross-linking density as a result of the dominate competition of copolymerisation rather than cross-lining kinetics. The interpenetrating approach was concluded as successful since hugely improved mechanical toughness and slightly reduced swelling capacities were observed in most IPN gel systems.

Signal Amplification by Reversible Exchange, or SABRE, is a type of PHIP (ParaHydrogen Induced Polarization) pioneered by Duckett, Green, and co-workers where an organometallic catalyst is used to co-locate parahydrogen (pH2) and a molecular substrate to be hyperpolarized. Like traditional PHIP, SABRE is of interest because it is cost-effective, potentially continuous, scalable, and rapid (achieving polarization enhancement in seconds). However unlike traditional PHIP, SABRE does not require permanent alteration of the substrate to hyperpolarize it. In addition to achieving 1H polarizations of several percent, SABRE in microTesla fields has enabled the creation of ~10% polarization for heteronuclear (15N) spins. I will discuss on a series of novel catalysts that I developed in my Ph.D program. Firstly of all, a heterogeneous SABRE ("HET-SABRE") catalyst where catalytic moieties were tethered to solid supports. Although NMR enhancements were modest (5), this initial work showed the feasibility of the approach. Next, two types of nanoscale catalysts were created to explore SABRE at the interface between heterogeneous and homogeneous conditions. Nanoparticle and polymer comb variants were synthesized by covalently tethering Ir-based catalysts to support materials comprised of TiO2/PMAA (poly methacrylic acid) and PVP (polyvinyl pyridine), respectively, and characterized by AAS, NMR, and DLS. Following pH2 delivery to mixtures containing one type of "nano-SABRE" catalyst, a target substrate, and ethanol, up to ~(-)40-fold and ~(-)7-fold 1H NMR signal enhancements were observed for pyridine using the nanoparticle and polymer comb catalysts, respectively, following transfer to high field (9.4 T). These enhancements appear to result from intact particles and not from any catalyst molecules leaching from their supports. Unlike the case with homogeneous SABRE catalysts, high-field (in situ) SABRE effects were generally not observed with the nanoscale catalysts. The potential for separation and reuse of such catalyst particles is also demonstrated. Besides the effort on green chemistry of SABRE catalyst, I have been investigating the preparation of different variants of the "standard" SABRE catalyst--[IrCl(COD)(IMes)] (IMes = 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene; COD=cyclooctadiene)]--for performing SABRE in otherwise "pure" aqueous environments. Because of the poor aqueous solubility of SABRE catalysts, previous promising efforts have used co-solvents to achieve SABRE in aqueous/organic mixtures. However, I have found that the chemical changes that accompany this catalyst's activation also endow it with water solubility. Complete removal of the organic solvent following activation and subsequent re-constitution of the activated structure in deuterated water allowed up to ~(-)33-fold 1H signal enhancements to be obtained for nicotinamide. Additionally, I have investigated chemical alteration of the structure of the pre-activated catalyst to endow greater water solubility. PEGylation of the aromatic carbine moiety provided much greater aqueous solubility, but while SABRE-active in organic solutions, the catalyst lost activity in >50% water (an effect under ongoing study). As an alternative approach, synthesis of a di-Ir complex precursor where the COD rings have been replaced by CODDA (1,2-dihydroxy-3,7-cyclooctadiene) permits creation of a water-soluble catalyst [IrCl(CODDA)IMes] that enables aqueous SABRE in a single step without need for any organic co-solvent; the potential utility of the catalyst is demonstrated with the ~(-)32-fold enhancement of 1H signals of pyridine in water with only 1 atm of pH2. Taken together, these results support the utility of rational design for improving SABRE and HET-SABRE for applications varying from fundamental studies of catalysis to biomedical imaging. In the following, I also investigate different aspects of how catalyst structure can affect resulting SABRE enhancements, including the interplay of catalyst structure and temperature for optimal SABRE, as well as the confounding effects on catalyst activation. Results from the "standard" Ir SABRE catalyst (1)--[IrCl(COD)(IMes)] (IMes = 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene; COD=cyclooctadiene)]--are compared with those obtained with variants respectively created by synthetically replacing the -Cl moiety with 4-amino-pyridine (4AP, 2), (diphenylphosphino)ethylamine (DPPA, 3), triphenyl phosphine (TPP, 4), and tribenzyl phosphine (TBP, 5); a sixth variant (6) was serendipitously created by an alternate synthetic route for (1) that appears to result in a polymorph according to x-ray crystallography. Studies of activation rate found that (4) and (5) activated the fastest under pH2 exposure (~20 s, an order of magnitude faster than (1)); activation rate was inversely correlated with SABRE enhancement, with peak 1H polarization enhancement ( ranging from only ~(-)44 for (4) to nearly ~(-)1900 for (1) (or PH~6%) for pyridine at 9.4 T, and ~(-)240 for nicotinamide. Although (1) gave the overall highest  values as expected, other catalysts gave rise to better SABRE performance in other temperature regimes: Optimal temperatures varied significantly, e.g. ~273 K for (2) to ~310-320 K for (1); the optimal temperature for (6) was considerably lower (<273 K) than that for (1), despite the apparent structural similarity. Taken together, these results show that full optimization of SABRE enhancement for a given experiment (with respect to substrate, target nucleus, etc.) may require systematic variation of parameters including catalyst ligand choice and temperature (to modulate binding affinities and off rates with respect to relevant spin-spin couplings), in addition to pH2 partial pressure, flow rate, and magnetic field. Finally, some research on an ssNMR will be represented, to show the potential application of ssNMR on the coating detection.

No description available.

Degradation in visibility is often introduced to images captured in poor weather conditions, such as fog or haze. In this paper, a fusion-based transmission estimation method is introduced to adaptively combine two different transmission models. Specifically, the new fusion weighting scheme and the atmospheric light computed from the Gaussian-based dark channel method improves the estimation of the locations of the light sources. To reduce the flickering effect introduced during the process of frame-based dehazing, a flicker-free module is formulated to alleviate the impacts. The system assessments show this approach is capable of superior defogging and dehazing performance, compared to the state-of-the-art methods, both quantitatively and qualitatively

Recently, there is great interest in achieving higher-level integration, higher data rates, and reduced overall costs. At millimeter-wave (mm-wave) bands, the wavelength is small enough to realize an antenna-on-chip (AoC), which is an ideal solution for high compactness and lower costs. However, the main drawback of AoC is the low resistivity (10 Ω-cm) Si substrate used in the standard CMOS technology, which absorbs most radio-frequency (RF) power that was supposed to be radiated by the on-chip antenna. Moreover, due to the high relative permittivity (11.9) and relatively large electrical thickness of the Si, higher order surface wave modes get excited, which further degrade the antenna radiation performance. In order to alleviate the above-mentioned issues with the low gain of AoC, a combination of an artificial magnetic conductor (AMC) surface, a high dielectric constant superstrate, and a Fresnel lens is presented in this work. The AMC is realized in standard CMOS technology along with the AoC, whereas the superstrate and lens are part of a smart packaging solution. The AMC surface can change wave propagation characteristics at the operating frequency to achieve in-phase reflection, resulting in gain enhancement by reducing the loss in the substrate. The high dielectric constant superstrate behaves as an impedance transformer between the Si substrate and air, thus enhancing the coupling to air. Finally, the Fresnel lens enhances the gain by focusing the electromagnetic (EM) radiation beam at the boresight. For AoC realization, a standard 0.18 μm CMOS process was utilized. A coplanar waveguide (CPW) fed monopole on-chip antenna at 71 GHz, along with the corresponding driving circuit, was designed and fabricated. The AMC enhances the gain by 3 dB. Since the chip needs to be packaged anyways, in this work, we optimize the package to provide further gain enhancement. This smart package, comprising a superstrate and a Fresnel lens, provides a gain enhancement of 16 dB. The overall combination of the optimized AMC surface, superstrate layer, and lens package can provide a gain enhancement of around 19 dB. Furthermore, the package has been realized through additive manufacturing techniques that ensure lower costs for the overall system.

This thesis is divided into two general sections. The first deals with the theory of digital magnetic recording and surveys the more common techniques used in digital magnetic tape recording. A new recording format is described which leads to a greater data rate at normal recording densities. The design and implementation of a recording system using this technique is described. The second section outlines the design of a portable digital recording system compatible with the peripheral unit described in section 1. The application of this system to the acquisition of data from a radioisotope scanner used in nuclear medicine is described and some basic results obtained from the system are demonstrated. Fundamental work towards image enhancement is outlined. / Thesis / Master of Engineering (ME)

The following work presents the ongoing philosophical debate regarding the use of biotechnology to improve human capabilities and attempts to apply the insights drawn from these debates to the regulation of non-medical uses of reproductive technology. After presenting the criticisms towards a hardline approach that would ban all attempts to enhance humans, we evaluate various alternative frameworks and adopt a framework called Genetic Justice, which can be understood as an application of Rawlsian distributive justice to biological assets. After improving on this moral framework by incorporating various institutional considerations into it, we apply it to the evaluation of non-medical uses of a screening technique called preimplantation genetic diagnosis and propose recommendations for its regulation.

The power amplifiers are typically the most power-consuming block in wireless communication systems. Spectrum is expensive, and newer technologies demand transmission of maximum amount of data with minimum spectrum usage. This requires sophisticated modulation techniques, leading to wide, dynamic signals that require linear amplification. Although linear amplification is achievable, it always comes at the expense of efficiency. Most of the modern wireless applications such as WCDMA use non-constant envelope modulation techniques with a high peak to average ratio. Linearity being a critical issue, power amplifiers implemented in such applications are forced to operate at a backed off region from saturation. Therefore, in order to overcome the battery lifetime limitation, a design of a high efficiency power amplifier that can maintain the efficiency for a wider range of radio frequency input signal is the obvious solution. A new technique that improves the drain efficiency of a linear power amplifier such as Class A or AB, for a wider range of output power, has been investigated in this research. The Doherty technique consists of two amplifiers in parallel; in such a way that the combination enhances the power added efficiency of the main amplifier at 6dB back off from the maximum output power. The classes of operation of power amplifier (A, AB, B, C etc), and the design techniques are presented. Design of a 2.14 GHz Doherty power amplifier has been provided in chapter 4. This technique shows a 15% increase in power added efficiency at 6 dB back off from the compression point. This PA can be implemented in WCDMA base station transmitter. / Master of Science

<p> The phenomena of energy gap and transition temperature enhancement have been studied on very thin (35-80 A° ) aluminum films, using the technique of electron tunneling through a thin insulating barrier. Transition temperatures as high as 2.16°K have been measured, and the corresponding measured energy gaps are found to be unique. In addition, these thin superconducting films exhibit stable transition temperatures when held in a vacuum. However, upon breaking vacuum, oxide growth occurs, and the tunneling barrier becomes impenetrable. Existing theories proposed to explain the observed enhancements, are discussed in the light of present accumulated experimental evidence. However, it is found that none are capable of explaining adequately the observed enhancements. </p> / Thesis / Master of Science (MSc)

No description available.