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No description available.

Piezoelectric composites have been investigated for use in a variety of areas, including flow control, structural control, energy harvesting, and fuel ignition systems. While many of the investigations conducted in these areas have utilized traditional piezo actuation systems, such as unimorphs or stack actuators, a growing number of research groups are examining the increased performance derived from the mechanical advantage, and enhanced domain rotation, found in prestressed unimorph designs. Prestressed devices, like Thunder® and LIPCA, have been shown well suited for a number of applications; however, the price associated with these devices can often prevent them from being implemented. In an effort to produce a low cost unimorph device that possesses a performance-enhancing curved form, the present investigation presents a novel technique for manufacturing prestressed piezoelectric actuators that are capable of meeting the same high displacement and load bearing capabilities exhibited by conventional prestressed devices. The newly proposed mechanically prestressed composite device, or MPC, is similar in form and function to well-documented thermally prestressed devices like Thunder®. However, rather than deriving its characteristic curved form from a thermally induced stress, the present class of devices relies on the resorting force incited in the piezoelectric ceramic upon adhesion to a mechanically deformed substrate to provide both the performance-enhancing prestress and final form of the device. To aid in refinement of the newly proposed design, beam theory was used to model the stress developed within the device. The model allowed designers to investigate the limitations imposed on the performance-enhancing curved form of the device by the stresses developed in the ceramic as a result of the curvature. Findings derived from the model were experimentally verified before a finalized design was specified for the composite, and a number of devices were manufactured. An initial characterization of the device was carried out based on the composite's response to mechanical and electrical loading. By determining the slope of the electrically and mechanically induced displacement response of the device, the investigation was able to define the center displacement constant and effective spring constant of the unimorph. These parameters not only allow designers to predict the displacement that will occur in response to a given electric field or tensile load, but also to allow for comparison with various devices. In the present investigation, the performance characteristics of mechanically prestressed composites were assessed as a function of substrate thicknesses and adhesive properties. With composites constructed using substrates approximately 9.2cm in length, devices were found to have typical center displacement constants on the order of 1.59 to 7.78kV/mm2 while retaining an effective stiffness between 4.5 to 7.5N/mm. These values were found to be similar to the .71 to 3.85kV/mm2 center displacement constants demonstrated by similarly sized and shaped Thunder® devices, which posses an effective stiffness in the range of 10 to 16.3N/mm. A comprehensive presentation of the test methods and procedures used to determine these values, along with other performance characteristics, are provided.

The construction of mechanically interlocked molecules has been the subject of decades of research. The efficiency of strategies for preparing these molecules has increased continuously. In recent years, the transition metal templation strategy has played quite a remarkable role in the synthesis of entwined or mechanically bonded structures due to the metals’ diverse coordination chemistry and ability to chelate ligands. In the early stages of this method’s development, the metal ions were used as integral part of the scaffold for such components as rings and stoppers to generate the interlocked structures. In newly developed active metal templation strategies, metal ions are used to promote covalent bond forming reactions while simultaneously acting as structural supports. In this thesis, three main aspects are expanded for the discussion of the application of metal template strategies. First of all, the newly developed strategy - active metal template - will be described and exemplified using the Huisgen-Meldal-Fokin Cu(I)- catalyzed 1,3-cycloaddition of azides with terminal alkynes (the CuAAC “click” reaction), the Cu(I)-mediated Cadiot-Chodkiewicz heterocoupling of an alkyne halide with a terminal alkyne, and the Ni(II)-catalyzed Csp3-Csp3 homocoupling reaction. Secondly, the thesis discusses the use of these strategies to obtain several hard-to-access structures, including the first high-yielding doubly threaded [3]rotaxanes, heterocircuitcatenanes and the one pot synthesis of homocircuit-catenanes, and the smallest molecular trefoil knot prepared to date. Lastly, as an extension of the metal temptation strategy, the final chapter of this thesis will discuss the assembly of inorganic metal-organic catenanes by metal coordination.

The invention of electric arc welding revolutionized the steel construction industry, but also brought some problems when the welded region has inferior properties compared to the plate metal. A major cause of brittle failure was identi ed as hydrogen embrittlement of the weld zone, although a comprehensive understanding of this phenomenon is not, even now, available. Hydrogen in solution in the weld zone is found in arc welds, due to the intense conditions in the welding arc. There is invariably a sufficient source in the form of moisture and hydrocarbon residue to give a few parts-per-million (ppm) by mass of hydrogen in the weld pool, which is a sufficient concentration to bring the possibility of hydrogen cold cracking in the completed weld. Hydrogen is significantly mobile in steels at room temperature, which is certainly why a few ppm of hydrogen can concentrate on a microscopic scale and initiate cracks, but also means that on a macroscopic scale there is hydrogen dispersion, which can relieve the cracking risk or place hydrogen in hydrogen cracking susceptible regions. The understanding of solubility and mobility of hydrogen in steels of different compositions and microstructures is therefore paramount. The question investigated in this work is whether the characteristics of the weld hydrogen cracking tendency can be explained by the features of weld hydrogen transport, especially when steel selection is a variable. Plate steel ranging from a 0.22%C pearlitic steel to a 0.05%C thermo-mechanically controlled-rolled and accelerated-cooled (TMCR-AC) high strength low alloy (HSLA) steel with no pearlite, plus a 0.4%C non-plate steel, were included in the experimental program. Welds were made with rutile ux-cored-wire (R-FCW) at two hydrogen levels, together with rutile shielded-metal-arc (R-SMA) welds. In order to investigate the di usion rates, a novel experiment has been devised. The welded plate has been milled away at an angle from the underside of the weld to provide increasing distances between the fusion boundary and the plate under-surface. The formation of hydrogen bubbles in glycerol enabled the measurements of the time dependent diffusion distances. The results clearly show a square root time correlation, as expected from the Fickian mechanism and enabled the calculation of diffusion coefficients for different steels. A nearly four fold difference was found between the steels, with the fastest hydrogen movement in the TMCR-AC steel. To reveal the initial distribution of hydrogen some samples were frozen immediately after welding and machined under liquid nitrogen. This test ruled-out any signi cant hydrogen dispersion during the deposition of the weld and during the cooling down period. The experimental data were interpreted using a new numerical computer model, based on random jumps of hydrogen between equivalent lattice sites. It is shown that this numerical model gives identical results to the analytical Fickian approach, but has the advantage that it can be used for any boundary shape. When this model has been applied to the experimental data, some unexpected features have been found. The amount of hydrogen emerging at surfaces distant to the weld was higher than expected from a concentration-driven mechanism; suggesting that a di erent transport mechanism should be applied. The numerical model has also indicated a discontinuity in the hydrogen concentration at the fusion boundary. It is a consequence of the model that hydrogen solubilities and di usivities are inversely related properties of the metal; a feature which is supported by experimental evidence. The tendency of hydrogen cracking to appear in the weld metal rather than in the heat-a ected-zone (HAZ) can thus be explained by higher di usivity of hydrogen in the plate metal. It appears that there is a relationship between the diffusivity and the microstructure, particularly when the content and form of carbon is considered.

The effects of the fortification of tortilla chips with mechanically expelled soy flour as well as baking and frying processes on the properties of tortilla chips were evaluated. Sensory characteristics, texture, thickness, color, protein and oil content were evaluated. Texture was measured by objective and subjective tests. Sensory properties were evaluated using a nine point hedonic scale. Soybeans (food grade Hartz) were mechanically expelled to obtain partially defatted soy flour of 6.7% final oil content. Dry masa flour (DMF) was replaced with 0, 10, 20 and 30% mechanically-expelled soy flour (MESF). The equilibrated tortilla was either fried in oil or baked in an air-impingement oven followed by convection oven drying. Overall, fried tortilla chips were harder and thicker than baked tortilla chips. Fried tortilla chips with 20 and 30% soy flour substitution required less force to break. In fried tortilla chips, as MESF increased, force and work levels decreased, where 20% MESF had the lowest force values. Thickness measurements of tortilla chips showed that as the thickness increased, the force and work also increased. Protein increased linearly in baked and fried tortilla chips where 30% resulted in the highest protein level. In fried tortilla chips, MESF fortification increased oil levels linearly as well. Baked tortilla chips were lighter than fried tortilla chips. In a consumer sensory evaluation, fried tortilla chips were preferred more than the baked ones. In fried tortilla chips, 20% had the highest sensory scores overall. Ten and 20% MESF fortification in fried tortilla chips were the most acceptable of all. In all treatments, regardless of type of processing, panelists could not detect any “beany” flavors in any of the samples. Therefore, dry extrusion followed by mechanical expelling proved successful in creating a suitable soy flour for tortilla chip production. MESF can be added at 10-30% levels in tortilla chips. Up to 20% would be recommended. Frying results in higher acceptability consumer scores over baking.

The purpose of the work resulting in this report is to develop a mechanically enhanced breaking bar, or prying bar, for bringing down trees. There was already a prototype to study, which was assembled by welded steel components. A specification of demands took form after continuous technical discussions with the inventor, assignee and mentors. When an analysis of this device and its function was made, the work continued with calculations to establish the foundation to design a mechanical model. Geometrical relationships were established to design the sub-components of the breaking bar and its functions. Simulations regarding material strength and mechanical function were made by the use of different modules in the CAD-software Solid Works and led to a simplified version of the breaking bar. The new simplified version was accepted by the inventor and the drawings for the new tool could now be made. During the time of this work the inventor has prepared his patent request and therefore this work has been classified and considered under secrecy for the inner circle persons containing the Kogertek-employees. The breaking bar which was produced with its powerful gear ratio is amplifying the force from the handle by a factor 25 and lifts 50 mm in the felling cut of the tree. In theory the tool would weigh approximately 1800 grams and can be used to bring down a tree with a diameter of at most 40 cm. Drawings for the constituent components were sent to a workshop to be manufactured and a mechanical breaking bar was assembled and tested.

This thesis is a development project for a myoelectric prosthetic hand. That means a mechanical hand that is controlled and actuated by the user's own muscles on the residual limb. The thesis has led to a theoretical concept of a complete prosthesis and a non-complete physical prototype that provides proof of concept and functions. The thesis was as a means of providing the mechanical development of an alternative model of the prosthesis that is more functional and has the ability to offer the users a lower price than current models. The foundation of the project is that the development has been done on a user needs basis. This leads to customer requirements that are derived from the users themselves. The development begun with a wide research to obtain user feedback as well as technical data of different mechanical solutions. The focal point of the thesis is the mechanical aspect of the prosthetic while the electronic and sensory systems were implemented with the use of standardized components.

Two separate experiments were used to investigate iron bioavailability of mechanically-deboned meats using hemoglobin regeneration to measure iron utilization. In both studies, male weanling rats were made anemic by bleeding and being fed a low-iron diet. Experimental diets were control fed to the animals and final hemoglobin concentrations were recorded. Animals were sacrificed and liver iron concentrations determined. The first experiment measured the iron bioavailability of mechanically-deboned and hand-deboned beef plate was better utilized by rats than the iron from mechanically- deboned shank and mechanically-deboned plate. The effect of lipid source and level on iron bioavailability of mechanically-deboned turkey meat was investigated in the second experiment. Fat from the meat was extracted before individual diets were prepared. Four lipids (corn oil, pork fat, turkey fat, or beef tallow) at three different levels (12%, 24%, or 36%) served as dietary fat sources, the effect of lipid dietary fat source and level on iron utilization was found to be negligible.

The efficacy of USDA approved antimicrobials was evaluated in reducing Salmonella and Campylobacter on ground chicken frames and chicken breast fillets. Chicken frames dip treated with peracetic acid (PAA), lauric arginate (LAE), cetylpyridinium chloride (CPC) and acidified lactic acid (ALA) reduced Salmonella and Campylobacter counts in ground chicken frames without affecting meat pH and color. PAA and LAE reduced Salmonella by 0.9 log on d0 whereas on d1, PAA and CPC reduced by 1.4 and 0.9 log CFU/g respectively. PAA, ALA, propionic acid and LAE significantly reduced Campylobacter by 0.7, 1.0, 1.3, and 1.2 log CFU/g, respectively. On chicken breast fillets, 30 s application of PAA (0.04% and 0.07% pH 6.5) reduced loosely attached Salmonella by 0.5 and 0.8 log CFU/ml, respectively. ALA, octanoic acid and PAA reduced loosely attached Campylobacter by 1 log while all treatments except propionic acid were effective against strongly attached cells on chicken breast fillets.