Over the past couple of decades interest in particle-stabilised emulsions or Pickering emulsions has greatly increased. When using particles as stabilisers, as opposed to surfactants, the interface becomes more rigid and this can lead to interesting physical properties. In addition, the resulting emulsions are found to be longer-lived garnering commercial interest. This thesis aims to explore the mechanical properties of some specific systems containing particle-stabilised interfaces. The main system investigated was the bicontinuous interfacially jammed emulsion gel or bijel. The bijel has two continuous interpenetrating liquid phases separated by a particle-stabilised interface. Therefore, the structure has a very large interface in a fairly small volume and the pore size is under the experimentalist's control giving it promise in a variety of applications, particularly those based on catalysis. The response of bijels stabilised by either spherical particles or anisotropic rod-shaped particles to centrifugal compression has been investigated in this thesis. It was found that, in both cases, the structure was distorted to create anisotropic particle-stabilised sheets orientated perpendicular to the force. The original method for fabricating bijels involves the arrested spinodal decomposition of partially miscible liquids. This method requires partially miscible liquid pairs and particles that are equally wetted by each phase. Due to these requirements, a new method for making bijels using mixing was developed by others and the bijel made by mixing has been tested with oscillatory rheology combined with imaging and squeeze flow experiments. It was found that at low strain the bijel displayed solid-like behaviour and the structure remained intact until well past the yielding point. In addition, two further systems were investigated. The first system was rod-shaped particle-stabilised emulsion droplets that stick together by particle bridging. Bridging is where one particle can stabilise two droplet interfaces, preventing coalescence and leading to droplet clusters. Particle bridging was found to occur regardless of shear rate, particle volume fraction and to some extent aspect ratio with these anisotropic rod-shaped particles. This behaviour is hypothesised to be a consequence of the charged nature of the silica surface above pH 2. The second system was large particle-stabilised water droplets that can sprout tubes by the partitioning of solute from a bath into the droplet. By using different solutes and mixtures of different alcohols, the key requirements for sprouting behaviour have been ascertained. The most important requirement was found to be achieving the correct balance between the interfacial tension and the amount of solute partitioning into the droplet.

DNA scaffolds self-assembled by short-stranded synthetic DNA can be tailored to build thermally reversible hydrogels with target binding sites. These hydrogels exhibit highly selective binding properties due to the specificity of DNA and also provide an aqueous environment for various reactions to happen within the network constraints. Hence, a careful study on the assembly mechanism and other physical aspects of DNA hydrogels is required to facilitate the future design and construction of such materials at the precise control. In this thesis, I present the work on well-designed DNA nano-stars as scaffolds for functional bulk materials with potential applications in bio-sensing. Chapter 1 starts with introducing the fundamental properties of DNA molecules, focusing on the advantages of utilising short-stranded DNA to programme and engineer micro- and macro- materials. Then it briefly reviews the field of rheology and micro-rheology, with the diffusing wave spectroscopy (DWS) technique illustrated explicitly as an example passive micro-rheology tool. Afterwards, a critical literature review on computational modelling of DNA systems is present, followed by the thesis outline at the end. Chapter 2 describes a simple DNA dendrimer system self-assembled from three-armed DNA nano-stars. The characterisation tools such as UV-vis spectroscopy, gel electrophoresis and dynamic light scattering (DLS) are introduced to verify the final production of the complex DNA structures. From this practice, we develop a routine for designing DNA scaffolds that yield optimal productivity. Chapter 3 investigates the mechanical properties of DNA hydrogels made of three-armed DNA nano-stars and how they change upon cooling and heating empolying DWS micro-rheology. The resulting viscoelastic moduli over a broad range of frequencies reveal a clear, temperature-reversible percolation transition coinciding with the melting temperature of the system's sticky ends. This indicates that we can achieve precise control in mechanical properties of DNA hydrogels, which is beneficial for designing more sensitive molecular sensing tools and controlled release systems. Chapter 4 develops a coarse-graining computational model of DNA hydrogels that resembles the system in Chapter 3 using LAMMPS, a classical molecular dynamics code. Thermodynamics, structural analysis and rheology tests were taken, qualitatively reproducing the physical phenomena of DNA assembly of the hydrogel network. Chapter 5 studies the internal behaviours of three-armed DNA complexes using oxDNA model also implemented in LAMMPS, with particular focus on the effect of the inert bases in the core and between double-stranded branches and single-stranded sticky ends. A deep insight into sequence-dependent behaviour of such complex structures can guide the parameter optimisation of the individual building blocks for the model described in Chapter 4. Chapter 6 concludes the thesis and presents an outlook for the future work that emerged out of my experimental and numerical studies.

The ability to produce precision ring shaped parts using the turning process depends significantly on the workholding characteristics. Workholding parameters such as the number of jaws and chucking force are known to influence the roundness tolerance of ring shaped parts commonly used in bearing applications. Experimental trial and error methods are often used in practice to optimize the workholding parameters to achieve the desired part quality. This thesis develops a systematic mathematical approach for optimizing these parameters using a finished cut roundness prediction model and a model for determining the reaction force between the chuck jaws and the ring. The roundness prediction model is verified through experiments for different cutting conditions. The optimization approach takes as input the required roundness tolerance, geometry and mechanical properties of the ring, cutting forces, and the coefficient of friction between the jaws and the ring. The output consists of the minimum number of jaws and the range of acceptable chucking forces that satisfy the required tolerance while preventing slip of the ring. Simulation examples are used to illustrate the proposed workholding optimization approach for a hard turning application. In addition, based on the optimization model, the thesis proposes a novel concept of dynamic chucking force control that promises to yield part roundness that is superior to conventional chucking.

This thesis endeavors to develop a new locking method for a twisted morphing wing spar. The conventional wing has to have hinges and a discontinuous surface. These cause air separation that decreases aerodynamic performance. Unlike this old concept, the new airfoil comprises a square cross section spar into the wing blade. Twisting the spar changes the airfoil?s angle of attack to control lifting and thrust force without a discontinuous surface. A nastic actuator generates shear stress for twisting the spar. A thermoplastic polymer locks the twisted shape. Applying heat and solidifying the polymer makes the beam lock into the twisted position even after removing the shear stress. This concept was evaluated by computer simulation and an experiment with a prototype construction. The analysis with 5m long spar shows that +450Pa shear stress generated +2 degrees twist and maximum 1.49MN/m spring constant at the spar tip. This spring constant helps a designer select the locking material, Ultem. The analysis proves that the Ultem film?s shear spring constant is high enough to hold the aluminum spar?s spring back. Physical experiment conditions might differ from computer simulation because environmental limitations might be present. The prototype spar has to be less than 300mm long to fit in an electric oven. Tension made the beam twist and baked it with locking material. When the polymer softened, the beam was taken from the oven and cooled. The solidified locking material held the spar at twisted status. The observation shows no detectable spring back after removing tension. Analytic solution also presents no spring back in twisting the prototype section spar. The FEA of the section spar verifies the physical experiment results. As a normal polymer, the Ultem shows stress relaxation. The load drop affects deceasing elastic modulus. Subsequently, the Ultem is able to lock the twisted spar even after the relaxation.

Take the Quadrangular-Pyramid-Shaped Fiber Endface(QPSFE) and the Conical-Wedge-Shaped Fiber Endface(CWSFE) for example, the present procedure of grinding asymmetric optical fiber endface demands three to four steps. These steps take time and are lack of repeatability and high yield. Aim at the shortcomings, this study develops a set of mechanism to attach to the original optical fiber grinding machine. The mechanism makes the normal pressure between the endface and the grinding plate change periodically to modify the removing rate of the material, thus enables the clipped flat endface of the optical fiber be ground into an elliptic-cone-shaped in a single grinding step, and then becomes a lens after its tip being fused by the arc. This mechanism reduces the fabricating time and cost, and consequently improve the economic benefits as well by simplifying the complicated manufacturing processes that represented before. Besides, for its single-step grinding characteristic, the offset between the center of the fiber and the elliptic-cone can thus be slashed to promote the yield. This study reviews the anterior references, including the papers and the patents, to begin, and then proposes the current means to compare with. Its contents involve the development of the forming principle, which proposes how the variation of the normal pressure takes influence on the removing rate of the material, and the required mechanism for the design procedure. The mechanism, the research result, and those needed to be ameliorated will be demonstrated in the conclusion and discussion part, so as to offer the investigating direction in the future.

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A new scheme of asymmetric elliptic-cone-shaped microlens (AECSM) employing a single-step fabrication technique for efficient coupling between the high-power 980nm laser diodes and the single-mode fibers is proposed. The asymmetric elliptic-cone-shaped fiber endface (AECSFE) was fabricated by a single-step grinding and polishing a cleaved fiber by applying a periodically variable torque on the fiber ferrule to change the grinding pressure. The periodically variable torque was made by an eccentric mass with a constant rotation speed double that of the fiber. After the AECSFE was formed, an AECSM was obtained by heating the fiber tip in a fusing splicer. In comparison with the previous works on asymmetric fiber microlenses fabricated by the multi-step processes with complicated fabrication, the advantages of the AECSM structure for achieving high coupling are a single-step fabrication, a reproducible process, and a high-yield output. In this study, we demonstrated that the average grinding offset of the AECSM structure for 30 measurements was about 0.4 £gm, the average coupling efficiency was 71%, and the maximum of the measured coupling efficiency was 83%. The yield of the AECSM for coupling efficiency over 70% was 47%, for coupling efficiency over 60% was almost 100%.

Abstract We propose a new scheme of lensed fiber employing a quadrangular-pyramid-shaped fiber endface (QPSFE) for the coupling high-power 980nm laser diodes and single-mode fibers. The quadrangular-pyramid-shaped fiber was accomplished by first grinding and polishing a flat surface to the center of fiber at the desired inclination angle of £c, rotating the fiber to £p and polishing to the center of fiber, repeating the same process on the other sides of the fiber by rotating the fiber to £k-£p and £p. Then the QPSFE was fabricated by heating the tip of quadrangular-pyramid-shaped fiber in a fusing splicer to form an elliptical microlens endface. A coupling efficiency of 85% has been demonstrated. This higher coupling efficiency of the QPSFE lensed fiber is attributed to the better matching of the elliptical Gaussian field distribution between the laser source and the fiber.

Safety-shaped median barriers have long been employed to keep misguided vehicles on the roadway. In recent years there has been a growing national desire for more aesthetically pleasing roadside safety systems. Adding surface texture is one of the most popular ways to make a more aesthetically pleasing barrier. This practice of adding surface texture can potentially reduce the safety performance of the barrier. The purpose of this research was to develop guidelines for the aesthetic surface treatment of safety-shaped median barriers. Numerical simulation was utilized to develop these guidelines. This was done by first validating the vehicle model that was used in this research, which was the National Crash Analysis Center (NCAC) 2000P Detailed Pickup Truck model. The validity of the vehicle model could be determined by comparing the vehicle dynamics of the simulation to the actual crash test data for the smooth surfaced Single Slope and New Jersey Safety-Shaped barriers. Crash tests involving concrete median barriers most commonly fail crash testing criteria given by the National Cooperative Highway Research Program (NCHRP) Report 350 by excessive Occupant Compartment Deformation (OCD). OCD is excessive deformation of the occupant compartment that would cause severe harm to the occupant. Current simulation vehicle models do not give reliable direct measurement of OCD. To take the place of direct measurement, several parameters were measured to find the best surrogate measure of OCD. The internal energy of the floorboard in the NCAC 2000P Detailed Pickup Truck model gave the best correlation to OCD. By simulating several different past crash tests with passing and failing OCD, limits of internal energy in the floorboard could determine if a simulation had passing, marginal, or failing amounts of OCD. Using the surrogate measure of OCD a parametric study was then evaluated by NCHRP Report 350 standards. The parametric study of 29 simulations varied width and depth of recess between asperities for two different angles of asperities. Guidelines were determined for the 45? and 90? angles of asperities as a curve on depth vs. width of recess between asperities from the results of this parametric study.

<p>Shaped charges are a well established type of projectile, subjected to a lot of research ever since emerging as a viable technology in the 1940s. The penetration achieved by shaped charges decreases with increased standoff distance. This is often attributed to the shaped charge jet losing its coherence. The Swedish Defence Research Agency however, noted no such loss of coherence in its experiments. An alternative explanation to the decrease of penetration was instead proposed. The object of this thesis was to investigate this proposed theory. To this end, the hydrocode Autodyn was used, modelling the impact of a high-velocity projectile into a generic target and analysing the resulting behaviour of the target. Several setups were used and several parameters were considered when evaluating the results. The conclusion of this thesis is that the alternative explanation offered is not supported by the observed behaviour of the target in the computer model.</p>