Technique to measure heats of reaction of Ti-B, Al-Ti-B, and Al-Ti-B4C powder blends

In this research, a modification to initiation aid ignition in bomb calorimetry that involves systemically blending levels of boron and potassium nitrate initiation aids with a bulk structural energetic elemental power blend is developed. A regression is used to estimate the nominal heat of reaction for the primary reaction. The technique is first applied to the synthesis of TiB2 as a validation study to see if close proximity to literature values can be achieved. The technique is then applied to two systems of interest, Al-Ti-B, and Al-Ti-B4C. In all three investigations, x-ray diffraction is used to characterize the product phases of the reactions to determine the extent and identity of the product phases and any by-products that may have formed as a result of adding the initiation aid. The experimental data indicates the technique approximates the heat of reaction value for the synthesis of TiB2 from Ti-B powder blends and the formation of TiB2 is supported by volume fraction analysis by x-ray diffraction. Application to the Al-Ti-B and Al-Ti-B4C blends show some correlation with variation of the initiation aid, with x-ray diffraction showing the formation of equilibrium products. However, these blends require further investigation to resolve more complex interactions and rule out extraneous variables.

STABILITY ANALYSIS OF THE SLOPE ALONG US-2 BETWEEN EPOUFETTE BAY AND THE CUT RIVER BRIDGE

Recently, water was observed flowing from a section of steep slope along US-2 near St. Ignace, Michigan in addition to soil sloughing in the area where the water is flowing from the slope. An inspection of the area also showed the presence of sinkholes. The original construction drawing for US-2 also indicated that sinkholes were present in this area prior to road construction in 1948. An investigation was conducted to determine the overall stability of the slope. The slope consists primarily of aeolian sand deposits. Laboratory testing determined the shear strength of the slope material to have a friction angle around 30°, which is also the slope angle. Thus, the slope is at its maximum angle for stability—however, the slope is also heavily wooded which provides additional support to the slope. Although the area surrounding the water flow has been sloughing, the remaining slope remains intact.

Fish contaminants through the tribal perspective : an ethnography of the Keweenaw Bay Indian Community's tribal fish harvest

It has been well documented that many tribal populations and minority groups across the nation have been identified as being at high risk of the adverse health effects created by consuming fish that have been contaminated with mercury, PCBs, DDT, dioxins, and other chemicals. Although fish consumption advisories are intended to inform fish consumers of risks associated with specific species and water bodies, advisories have been the subject of both environmental injustices and treaty rights’ injustices. This means that understanding fish contaminants, through community perspectives is essential to good environmental policy. This study examined the fish contaminant knowledge, impacts on fishing and fish consumption, and the factors that contribute to harvesting decisions and behaviors in one tribal nation in the Upper Peninsula of Michigan, the Keweenaw Bay Indian Community. Using ethnographic methods, participant observation and semi-structured interviewing, fieldnotes were kept and all interviews were fully transcribed for data analysis. Among seventeen fishermen and women, contaminants are poorly understood, have had a limited impact on subsistence fishing but have had a substantial impact on commercial fishing activity. But ultimately, all decisions and behaviors are based on their own criteria and within a larger context of knowledge and understanding: the historical and cultural context. The historical context revealed that advisories are viewed as another attack on tribal fishing. The cultural context revealed that it is the fundamental guidance and essential framework associated with all harvesting beliefs, values, and traditional lifeways. These results have implications for advisories. ‘Fish’ and ‘contaminants’ appear differently based on the perceptions and priorities of those who encounter them.

Analysis of transport properties of mechanically alloyed [Pb1-xSnxTe]

The work described in this thesis had two objectives. The first objective was to develop a physically based computational model that could be used to predict the electronic conductivity, Seebeck coefficient, and thermal conductivity of Pb1-xSnxTe alloys over the 400 K to 700 K temperature as a function of Sn content and doping level. The second objective was to determine how the secondary phase inclusions observed in Pb1-xSnxTe alloys made by consolidating mechanically alloyed elemental powders impact the ability of the material to harvest waste heat and generate electricity in the 400 K to 700 K temperature range. The motivation for this work was that though the promise of this alloy as an unusually efficient thermoelectric power generator material in the 400 K to 700 K range had been demonstrated in the literature, methods to reproducibly control and subsequently optimize the materials thermoelectric figure of merit remain elusive. Mechanical alloying, though not typically used to fabricate these alloys, is a potential method for cost-effectively engineering these properties. Given that there are deviations from crystalline perfection in mechanically alloyed material such as secondary phase inclusions, the question arises as to whether these defects are detrimental to thermoelectric function or alternatively, whether they enhance thermoelectric function of the alloy. The hypothesis formed at the onset of this work was that the small secondary phase SnO2 inclusions observed to be present in the mechanically alloyed Pb1-xSnxTe would increase the thermoelectric figure of merit of the material over the temperature range of interest. It was proposed that the increase in the figure of merit would arise because the inclusions in the material would not reduce the electrical conductivity to as great an extent as the thermal conductivity. If this were to be true, then the experimentally measured electronic conductivity in mechanically alloyed Pb1-xSnxTe alloys that have these inclusions would not be less than that expected in alloys without these inclusions while the portion of the thermal conductivity that is not due to charge carriers (the lattice thermal conductivity) would be less than what would be expected from alloys that do not have these inclusions. Furthermore, it would be possible to approximate the observed changes in the electrical and thermal transport properties using existing physical models for the scattering of electrons and phonons by small inclusions. The approach taken to investigate this hypothesis was to first experimentally characterize the mobile carrier concentration at room temperature along with the extent and type of secondary phase inclusions present in a series of three mechanically alloyed Pb1-xSnxTe alloys with different Sn content. Second, the physically based computational model was developed. This model was used to determine what the electronic conductivity, Seebeck coefficient, total thermal conductivity, and the portion of the thermal conductivity not due to mobile charge carriers would be in these particular Pb1-xSnxTe alloys if there were to be no secondary phase inclusions. Third, the electronic conductivity, Seebeck coefficient and total thermal conductivity was experimentally measured for these three alloys with inclusions present at elevated temperatures. The model predictions for electrical conductivity and Seebeck coefficient were directly compared to the experimental elevated temperature electrical transport measurements. The computational model was then used to extract the lattice thermal conductivity from the experimentally measured total thermal conductivity. This lattice thermal conductivity was then compared to what would be expected from the alloys in the absence of secondary phase inclusions. Secondary phase inclusions were determined by X-ray diffraction analysis to be present in all three alloys to a varying extent. The inclusions were found not to significantly degrade electrical conductivity at temperatures above ~ 400 K in these alloys, though they do dramatically impact electronic mobility at room temperature. It is shown that, at temperatures above ~ 400 K, electrons are scattered predominantly by optical and acoustical phonons rather than by an alloy scattering mechanism or the inclusions. The experimental electrical conductivity and Seebeck coefficient data at elevated temperatures were found to be within ~ 10 % of what would be expected for material without inclusions. The inclusions were not found to reduce the lattice thermal conductivity at elevated temperatures. The experimentally measured thermal conductivity data was found to be consistent with the lattice thermal conductivity that would arise due to two scattering processes: Phonon phonon scattering (Umklapp scattering) and the scattering of phonons by the disorder induced by the formation of a PbTe-SnTe solid solution (alloy scattering). As opposed to the case in electrical transport, the alloy scattering mechanism in thermal transport is shown to be a significant contributor to the total thermal resistance. An estimation of the extent to which the mean free time between phonon scattering events would be reduced due to the presence of the inclusions is consistent with the above analysis of the experimental data. The first important result of this work was the development of an experimentally validated, physically based computational model that can be used to predict the electronic conductivity, Seebeck coefficient, and thermal conductivity of Pb1-xSnxTe alloys over the 400 K to 700 K temperature as a function of Sn content and doping level. This model will be critical in future work as a tool to first determine what the highest thermoelectric figure of merit one can expect from this alloy system at a given temperature and, second, as a tool to determine the optimum Sn content and doping level to achieve this figure of merit. The second important result of this work is the determination that the secondary phase inclusions that were observed to be present in the Pb1-xSnxTe made by mechanical alloying do not keep the material from having the same electrical and thermal transport that would be expected from “perfect" single crystal material at elevated temperatures. The analytical approach described in this work will be critical in future investigations to predict how changing the size, type, and volume fraction of secondary phase inclusions can be used to impact thermal and electrical transport in this materials system.

STUDY OF SPARK IGNITION ENGINE COMBUSTION MODEL FOR THE ANALYSIS OF CYCLIC VARIATION AND COMBUSTION STABILITY AT LEAN OPERATING CONDITIONS

A fundamental combustion model for spark-ignition engine is studied in this report. The model is implemented in SIMULINK to simulate engine outputs (mass fraction burn and in-cylinder pressure) under various engine operation conditions. The combustion model includes a turbulent propagation and eddy burning processes based on literature [1]. The turbulence propagation and eddy burning processes are simulated by zero-dimensional method and the flame is assumed as sphere. To predict pressure, temperature and other in-cylinder variables, a two-zone thermodynamic model is used. The predicted results of this model match well with the engine test data under various engine speeds, loads, spark ignition timings and air fuel mass ratios. The developed model is used to study cyclic variation and combustion stability at lean (or diluted) combustion conditions. Several variation sources are introduced into the combustion model to simulate engine performance observed in experimental data. The relations between combustion stability and the introduced variation amount are analyzed at various lean combustion levels.