Parameter optimization for controlling aluminum loss when laser depositing Ti-6Al-4V

The ability to predict the mechanical properties of engineering materials is crucial to the manufacturing of advanced products. In the aerospace industry, Ti-6Al-4V is commonly used to build structures. Any deviation from the alloy\u27s standard properties can prove detrimental. Thus, the compositional integrity of the material must be controlled. The ability to directly build and repair large, complicated structures directly from CAD files is highly sought after. Laser Metal Deposition (LMD) technology has the potential to deliver that ability. Before this process can gain widespread acceptance, however, a set of process parameters must be established that yield finished parts of consistent chemical composition. This research aims to establish such a set of parameters. Design of Experiments was utilized to maximize the information gained while minimizing the number of experimental trials required. A randomized, two-factor experiment was designed, performed, and replicated. Another set of experiments (nearly identical to the first) was then performed. The first set of experiments was completed in an open environment, while the second set was performed in an argon chamber. Energy Dispersive X-Ray Spectroscopy (EDS) was then used to perform a quantitative microanalysis to determine the aluminum level in each sample. Regression analysis was performed on the results to determine the factors of importance. Finally, fit plots and response surface curves were used to determine an optimal parameter set (process window). The process window was established to allow for consistent chemical composition of laser deposited Ti64 parts --Abstract, page iii

Development of a modeling algorithm to predict lean implementation success

”Lean has become a common term and goal in organizations throughout the world. The approach of eliminating waste and continuous improvement may seem simple on the surface but can be more complex when it comes to implementation. Some firms implement lean with great success, getting complete organizational buy-in and realizing the efficiencies foundational to lean. Other organizations struggle to implement lean. Never able to get the buy-in or traction needed to really institute the sort of cultural change that is often needed to implement change. It would be beneficial to have a tool that organizations could use to assess their ability to implement lean, the degree to which they have implemented lean, and what specific areas they should focus on to improve their readiness or implementation level. This research investigates and proposes two methods for assessing lean implementation. The first is utilizing standard statistical regression. A regression model was developed that can be used to assess the implementation of lean within an organization. The second method is based in artificial intelligence. It utilizes an unsupervised learning algorithm to develop a training set corresponding to low, medium, and high implementation. This training set could then be used along with a supervised learning algorithm to dynamically monitor an organizations readiness or implementation level and make recommendations on areas to focus on to improve implementation success”--Abstract, page iv

Caught in the act: Implications for the increasing abundance of mafic enclaves during the eruption of the Soufriere Hills Volcano, Montserrat

An exceptional opportunity to sample several large blocks sourced from the same region of the growing Soufrière Hills lava dome has documented a significant increase in the presence of mafic enclaves in the host andesite during the course of a long-lived eruptive episode with several phases. In 1997 (Phase I) mafic inclusions comprised ~1 volume percent of erupted material; in 2007 (Phase III) deposits their volumetric abundance increased to 5–7 percent. A broader range of geochemically distinctive types occurs amongst the 2007 enclaves. Crystal-poor enclaves generally have the least evolved (basaltic) compositions; porphyritic enclaves represent compositions intermediate between basaltic and andesitic compositions. The absence of porphyritic enclaves prior to Phase III magmatism at Soufrière Hills Volcano suggests that a mixing event occurred during the course of the current eruptive episode, providing direct evidence consistent with geophysical observations that the system is continuously re-invigorated from depth

Longitudinal stability of genetic and environmental influences on the association between diurnal preference and sleep quality in young adult twins and siblings

Overlapping genetic influences have been implicated in diurnal preference and subjective sleep quality. Our overall aim was to examine overlapping concurrent and longitudinal genetic and environmental effects on diurnal preference and sleep quality over ~5 years. Behavioural genetic analyses were performed on data from the longitudinal British G1219 study of young adult twins and non-twin siblings. 1556 twins and siblings provided data on diurnal preference (Morningness-Eveningness Questionnaire) and sleep quality (Pittsburgh Sleep Quality Index) at time 1 (mean age=20.30 years, SD=1.76; 62% female); and 862 participated at time 2 (mean age=25.30 years, SD=1.81; 66% female). Preference for eveningness was associated with poorer sleep quality at both time-points (r=.25[95% confidence intervals, (CI)=.20-.30], and r=.21[CI=.15-.28]). There was substantial overlap in the genetic influences on diurnal preference and sleep quality individually, across time (genetic correlations [rA’s]: .64[95% CI = .59-.67] and .48[95% CI = .42-.53]). There were moderate genetic correlations between diurnal preference and sleep quality concurrently and longitudinally (rAs=.29-.60). Non-shared environmental overlap was substantially smaller for all cross-phenotype associations (non-shared environmental correlations [rE’s]=-.02-.08). All concurrent and longitudinal associations within and between phenotypes were largely accounted for by genetic factors (explaining between 60%-100% of the associations). All shared environmental effects were non-significant. Non-shared environmental influences played a smaller role on the associations between phenotypes (explaining between -.06%-40% of the associations). These results suggest that to some extent similar genes contribute to the stability of diurnal preference and sleep quality throughout young adulthood, but also that different genes play a part over this relatively short time-frame. While there was evidence of genetic overlap between phenotypes concurrently and longitudinally, the possible emergence of new genetic factors (or decline of previously associated factors) suggests that molecular genetic studies focussing on young adults should consider more tightly specified age-groups, given that genetic effects may be time-specific

Quaternary Geology and Seismic Hazard of the Sierra Madre and Associated Faults, Western San Gabriel Mountains

This detailed study of a 40-km-long section of the Sierra Madre and associated fault zones in the central transverse Ranges, along the south side of the San Gabriel Mountains, is aimed at providing information for evaluating the seismic hazard that these faults pose to the heavily populated area immediately to the south. Evidence on the location of fault strands and the style and timing of fault movements during the Quaternary was obtained from detailed geologic mapping, aerial-photograph interpretation, alluvial stratigraphy, structural and stratigraphic relations in some 33 trench excavations at critical localities, and subsurface data. We present a time-stratigraphic classification for the Quaternary deposits in the study area, based on soil development, geomorphology, and contact relations among the alluvial units. We distinguish four units, with approximate ages, as follows: unit 4, about 200,000 yr to middle Quaternary; unit 3: about 11,000 to 200,000 yr; unit 2; about 1,000 to 11,000 yr; and unit 1; younger than about 1,000 yr. We use this classification to evaluate on a semi-quantitative basis the evidence for fault activity in the study area and to infer the relative seismicity of different segments of the Sierra Madre fault zone during the Quaternary. Alluvial-fan development (particularly fanhead incision and the ages of alluvial-fan deposits) also gives clues as to relative seismicity. The most active segment of the Sierra Madre fault zone within the study area is the westernmost section, adjacent to the faults that broke during the 1971 San Fernando, Calif., earthquake. The age of activity, as indicated by the occurrence of Holocene faulting, decreases toward the east. Along the Sierra Madre fault, through La Canada, Altadena, Sierra Madre, and Duarte, is abundant evidence of late Pleistocene faulting. Total vertical displacement is more than 600 m, but there is no evidence for Holocene fault movement. These observations suggest that the presently applicable recurrence interval between major earthquakes in the central and eastern sections of the Sierra Madre fault zone is longer than about 5,000 yr. The local magnitude (M_L) of the largest credible earthquake that could occur on the Sierra Madre fault zone in the study area is estimated at 7, on the grounds that the fault zone is probably limited mechanically by subdivision into separate arcuate segments about 15 km long. The Raymond fault, which branches southwestward from the Sierra Madre fault in the eastern part of the study area, shows well-defined evidence of a late Quaternary history of repeated fault movements. Displacements of alluvial strata observed in trench excavations across the fault give evidence of five major seismic events, whose times of occurrence can be estimated from radiometric dating at approximately 36,000, 25,000, 10,000-2,200 (two events), and 2,200-1,500 yr B.P. Further evidence suggests at least three more faulting events in the past 29,000 yr, for which specific dates cannot be determined. Because some additional events probably remain undetected, we infer that an average recurrence interval of about 3,000 yr, with an average vertical displacement of 0.4 m per event, is applicable to the Raymond fault in its present state, as indicated by its history of movement over the past 36,000 yr. This level of activity is distinctly higher than that found for the Sierra Madre fault zone in the central and eastern parts of the study area. If the entire 15-km length of the Raymond fault would rupture in a single event, as seems likely, a maximum credible earthquake of M_L 6 3/4 can reasonably be assumed