The effect of normal load, contact velocity, and dwell time on the coefficient of adhesion at slip in braking was investigated. A test rig that simulated locomotive wheel/rail interactions was used for the experimentation. The results indicated a drop in the coefficient of adhesion with increasing speed. However, normal load, contact velocity, and dwell time, as operating variables, did not have any effect on the variation of the coefficient of adhesion. A description of the investigation and recommendations for further studies is included. / Master of Science

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Contrary to common intuition, free jets of fluid can ``bounce'' off each other on collision in mid-air, through the effect of a lubricating air film that separates the jets. While there has been much work on coalescing jets of fluid and non-coalescence in other systems like drop-drop, drop on a bath, jet on a bath, non-coalescence of fluid jets has been little studied. A simple experimental setup was developed to stably demonstrate and study the non-coalescence of jets upon collision. This thesis presents the results of an experimental investigation of oblique collision between two fluid jets. The transition from bouncing to coalescence of jets is examined for various jet sizes and angles. Results indicate that the transition from bouncing to coalescence can be rationalized in terms of critical value of the dimensionless parameter Normal Weber Number, which represents the ratio between inertial and surface tension forces. A parametric study of the characteristic of bouncing jets, conducted by varying the nozzle diameter, jet velocity, angle of inclination and fluid viscosity reveals the scaling laws for the quantities involved such as contact time. These scaling laws help us in elucidating the role of various physical forces at play such as viscous stresses, capillary force and inertia / Master of Science

The empirical knowledgebase of intergenerational programming (IGP) largely relies on anecdotal reports by staff and family members. The lack of concrete knowledge is particularly evident in the literature regarding IGP involving elders with dementia. In an effort to fill some of the voids in the current literature base, observations were conducted for seven weeks at a co-located child and adult day program to determine the effects of IGP on 10 older adult participants (M age =81 yrs., S.D. = 5.21). All participants (5 male and 5 female) were diagnosed with dementia by a physician and attended the adult day program regularly. Intergroup contact theory, which emphasizes interdependence between groups, informed the development and facilitation of the IGP activities. A structured scale was utilized to assess the elders' social behavior and affect during IGP. Control observations were conducted during adult-only activities representative of traditional dementia-care programming, and qualitative data were collected through participant interviews and facilitator journaling to corroborate the quantitative findings. T-test analyses revealed that the older adults exhibited significantly greater levels of group social behavior and significantly fewer instances of unoccupied behavior during IGP as compared to traditional adult-only activities. The adults also expressed significantly more positive affect during IGP than in the control activities. Findings from the qualitative inquiries supported the quantitative results by emphasizing the meaning and purpose of IGP for the elders. Results indicated that effectively planned and facilitated IGP is an appropriate and interesting activity for elders with dementia. / Master of Science

People with osteoarthritis (OA) suffer from joint degeneration and pain as well as difficulty performing daily activities. Joint contact forces (JCF) are important for understanding individual joint loading, however, these contact force cannot be directly measured without instrumented implants. Musculoskeletal modeling is a tool for estimating JCF without the need for surgery. The results from these models can be very different due to different approaches used in the development of a model that was used for simulation. Therefore, the first purpose of this study was to develop and validate a musculoskeletal model in which lower extremity JCF were calculated at the hip, knee, and ankle in 10 participants with hip OA (H-OA) and 10 healthy control participants using OpenSim 4.0 [simtk.org, 23]. The generic gait2392 model was scaled to participant demographics, then the inverse kinematics (IK) solution and kinetic data were input into the Residual Reduction Algorithm (RRA) to reduce modeling errors. Kinematic solutions from RRA were used in the Computed Muscle Control (CMC) tool to compute muscle forces, then JCF were estimated using the Joint Reaction Analysis tool. Validation included JCF comparisons to published data of similar participant samples during level walking, and movement simulation quality was assessed with residual forces and moments applied at the pelvis, joint reserve actuators, and kinematic tracking errors. The computed JCFs were similar to the overall trends of published JCF results from similar participant samples, however the values of the computed JCFs were anywhere from 0.5 times body weight (BW) to 3BW larger than those in published studies. Simulation quality assessment resulted in low residual forces and moments, and low tracking errors. Most of the reserve actuators were small as well, besides pelvis rotation and hip rotation. The computed JCF were then used in the second portion of this study to determine the effect of group and side on JCF during both the weight acceptance and push-off phases of level walking. It was determined that there was a significant difference in the knee and ankle JCF during the weight acceptance portion of stance phase and at all joints during the push-off phase when comparing the H-OA and control groups on the affected limb. A significant interaction between group and limb was found for the peak hip JCF timing (% stance) during the push-off portion of the stance phase (p=0.009). These results demonstrate that H-OA participants experience an earlier peak hip JCF during propulsion on their affected limb. Based on previous research in OA that has examined spatiotemporal measures, this finding suggests that H-OA participants may use step or stride length changes as a strategy to decrease or limit pain and loading on the affected limb. Knowledge of potential JCF differences in H-OA participants, such as timing of the peaks in either portion of the stance phase, could provide useful insight to clinicians and therapists to make decisions on how to proceed with treatment or rehabilitation programs. / Master of Science / People with osteoarthritis suffer from joint degeneration and pain as well as difficulty performing daily activities, like walking. It is important to understand the forces and loading within individual joints. Musculoskeletal modeling is one way that researchers can estimate these joint contact forces (JCF) without needing a joint replacement implant that can measure these forces. When it comes to modeling simulations, there is a wide variety of results. Therefore, the first purpose of this study was to develop and validate a musculoskeletal model in which JCFs were calculated at the hip, knee, and ankle in 10 participants with hip osteoarthritis and 10 healthy adults. Validation of the model was completed through a comparison between computed results and published data of similar participant samples during level walking. The computed results were similar to the overall trends of published JCF results, however the numerical values themselves were larger than those in published studies. The computed JCFs were then used in the second portion of this study to determine how the two groups and limbs differ during level walking. There was a significant difference in the knee and ankle JCF during the first half of the stance phase and in all joints during the second half of stance when comparing the two groups. The hip osteoarthritis participants also experience an earlier peak hip JCF during the second half of stance phase on their affected limb. This finding suggests that hip osteoarthritis participants may change the way they take a step as a strategy to decrease or limit pain and loading on the affected limb. Knowledge of potential JCF differences, such as timing of the peaks in either portion of the stance phase, could provide useful insight to clinicians and therapists to make decisions on how to proceed with treatment or rehabilitation programs.

The rising costs of attending college have students, families, and other stakeholders calling for evidence of gains that result from earning a degree (Burrows, 1999; Jongbloed, Enders and Salerno, 2008; Julian, 2012). They expect that graduates to achieve cognitive gains in communication, critical thinking, and the ability to work independently and in teams (SHEEO, 2005). Additionally, the global marketplace has created the need for graduates to achieve sociocultural gains; they need to understand different cultures and successfully interact with diverse peoples (Gurin, 1999; Leville, 2006). Research has shown that different experiences influence cognitive and sociocultural gains including student faculty interaction (SFI) and intergroup contact (IGC) (Cole, 2007; Kuh and Hu, 2001; Thompson, 2001; Umbach and Porter, 2002). However, cognitive and sociocultural gains have typically been explored independently. Moreover, researchers have not examined the demographic factors that, combined with SFI and IGC, promote such gains. The purpose of this study was to determine if SFI, IGC, and demographic factors (gender, race or academic major) explain variance in cognitive and sociocultural gains among college seniors. The sample included seniors who completed the College Student Experiences Questionnaire (CSEQ) Fourth edition. The results of the hierarchical linear regression revealed that SFI and IGC have a significant influence on both cognitive and sociocultural gains. However, the impact of these predictors is not experienced by every student uniformly; a student's sex, race and academic major matters. / Ph. D.

Team projects in engineering are critical sites for professional and personal development as students interact with peers and faculty on projects designed to simulate engineering work. These projects allow students to try on professional roles and establish a sense of identity within their field, which in turn influences their retention through college and into engineering careers. However, team projects can present challenges specific to students from underrepresented populations. While research on women's team experiences is strong, few researchers have studied African-Americans. To fill this gap, the current study explores the experiences of African-American males on multiracial student teams and the impact of those teams on these students' identities. This qualitative study employed a phenomenological approach, using a three-interview sequence with eight African-American male engineering students as they worked on team projects at a predominantly white institution (PWI). The interviews gathered background information about each participant, explored the team functionality during the project, and enabled participants to reflect on the team experience. Two theoretical frameworks were considered during the study design: 1) intergroup contact theory provided a lens to explore interracial interactions, and 2) multiple identities provided a lens to analyze the impact of team dynamics on students' intersecting identities. The findings provide a rich understanding of the team experiences of African-American male students that can enhance project-based teaching within engineering to more explicitly attend to team dynamics, including interracial interactions for students of color. Both positive and negative impacts on African-American males in engineering emerged from the intergroup contact within the team environment. Specifically, the results indicate that these participants enjoyed their multiracial student teaming experiences, supported by informal social interactions among team members and generally positive professional interactions. However, the study participants also entered their team experiences fully aware of the negative stereotypes about African-Americans in engineering and proactively worked to dispel those stereotypes. / Ph. D.

This dissertation presents an analytical study of a class of problems involving discontinuities, also referred to as shocks, propagating through one dimensional flexible objects such as strings and rods. The study entails interrogation of the classical balance laws of momentum, angular momentum, and energy across propagating discontinuities. A major part of this dissertation also concerns itself with a non-classical entity called the ``material momentum''. The balance of material momentum is studied in a variational context, where both the local and singular forms of it are derived from an action principle. A distinguishing aspect of discontinuities propagating in continua is that, unlike in the bulk, the balance of momentum and angular momentum are not sufficient to describe their mechanics, even when the discontinuities are energy conserving. In this work, it is shown that the additional information required to close the system of equations at propagating discontinuities can be obtained from the singular form of energy balance across them. This entails splitting of the energy balance by its invariance properties, and identifying the non-invariant and invariant part of the source term with the power input and energy dissipation respectively at the shock. This approach is in contrast with other treatments of such problems in the literature, where additional non-classical concepts such as ``material momentum'' and ``configurational force'' have been invoked. To further our understanding of the connections between the classical and non-classical approaches to problems involving discontinuities, a detailed exposition of the concept of material momentum is presented. The balance and conservation laws associated with material momentum are derived from an action principle. It is shown that the conservation of material momentum is associated with the material symmetry of the continuum, and that the conditions for the conservation of physical and material momentum are independent of each other. A new classification of the deformed configurations of the planar Euler elastica based on conserved quantities associated with the spatial and material symmetry of the rod is proposed. The manifestation of the balance of material momentum in seemingly unrelated fields of research, such as fracture mechanics, ideal fluids, and the mechanics of rods with discontinuities, is also discussed. / Ph. D. / One dimensional flexible bodies such as strings and rods can exhibit fascinating and counterintuitive behavior when they interact with rigid obstacles. For instance, a chain falling on a rigid surface falls faster than it would have if it were falling freely. When one end of a long chain piled up in a container placed at an elevation is pulled across the rim and let go, the chain flows out of the container like a water fountain. Discontinuities in the cross-sectional properties of an elastic rod contained in a curved frictionless channel can result in the generation of forces that propel the rod along the channel. Such counterintuitive phenomena are a consequence of the physics taking place at the point of partial contact where the flexible body comes in contact with a rigid surface. The purpose of this dissertation is to study the mechanics of such points of discontinuity. Several such phenomena where effectively one dimensional bodies interact with rigid surfaces are all around us. A familiar example is the peeling of an adhesive tape, where the peeling front qualifies as a point of discontinuity propagating through the tape as the peeling progresses. A good understanding of the mechanics of the peeling front is crucial in estimating the strength of the adhesive. Another such example of practical importance is a mooring line being placed on the seabed. In such situations, the existence of a reaction force acting at the touchdown point depends on whether or not the cable develops a kink at that point. Similar questions of importance can be asked in the context of deployment and unspooling of space tethers. In this dissertation, an analytical study of the general physics of the phenomena described above is presented. Standard theoretical tools of classical physics are employed to understand the mechanics of points of partial contact between flexible and rigid bodies. The conditions under which a flexible body could experience sharp changes in its geometry (e.g. a kink) at such points are investigated. In addition to that, we explore the implications of a nonclassical law of physics called the balance of “material momentum” in the context of such problems.

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Very high temperature (>900 °C) contact metamorphism and metasomatism of aluminous schist xenoliths in the mafic to ultramafic Cortlandt Complex, New York, resulted in formation of bodies of unusual Fe- and Al-oxide-rich rock called emery. During contact heating, disequilibrium thermal decomposition of the protolith schists in one closely examined xenolith produced two end-member materials: a quartzo-feldspathic water-undersaturated melt which partitioned much of the silica and calcium and all of the alkalis of the original schist; and a highly aluminous fine-grained emery residuum which contained spinel, magnetite, ilmenohematite, sillimanite, and sporadically corundum. During cooling, melt within the xenoliths was injected as cm-scale veinlets into the silica-poor solid residuum. Local increase in silica activity resulted in progressive silication reactions of spinel-rich residuum to several silicates. A simple model of progressive silication would require that reactions should occur from lower to higher silica content of product silicates in stages, e.g., spinel – sapphirine (Si/O=0.10), sapphirine – garnet (0.25), garnet – orthopyroxene (0.28), rather than directly from spinel to higher-silica minerals which would overstep intermediate reaction steps. However, observed reaction textures indicate the latter more complex behavior in which spinel may have reaction rims of, or occur as inclusions within, any of the three silicate minerals. Statistical analysis of several samples has shown the mode to be the spinel-orthopyroxene reaction rim boundary although orthopyroxene is the highest-silica product mineral, based on Si/O ratio. Chi-square test results are significant and show that the textural relations observed among spinel, sapphirine, garnet, and orthopyroxene are dependent. Increased silica activity therefore cannot be the only factor controlling the reaction sequence. Microprobe data has been collected in an attempt to correlate mineral compositions with the different textural occurrences. The effects of local equilibria appear to be the dominant factors in the overstepping of sequential reactions. Qualitative activity-activity diagrams proved useful for examining the effects of bulk composition on the relative stabilities of spinel and the three silicates, including variations in Fe/(Fe+Mg), bulk Mn and Zn contents, and minor local variation in oxygen fugacity. Matrix spinel compositions (i.e., those not modified by reaction to silicates) fall into two groups: a more magnesian one containing spinels with average Fe/(Fe+Mg) (Fe#) of 0.49 and a less magnesian one, average Fe# of 0.67. With regard to this bulk compositional effect, the more magnesian composition should reduce garnet stability due to the strong fractionation of Fe into garnet, thus favoring the reaction of spinel to orthopyroxene within silica-rich areas. In more aluminous areas, spinel will react to form sapphirine, then garnet, then possibly orthopyroxene. A less magnesian composition would expand the stability of garnet at the expense of sapphirine and, to a lesser extent, orthopyroxene. Zinc has a subtle effect on mineral stabilities. Because Zn is strongly partitioned into spinel, higher zinc contents (concentrations in some spinels are as high as 14.9 mol% gahnite) may expand the stability of that mineral considerably. Consequently, spinel stability may increase relative to the three silicates, but this may be quite variable due to variable reaction stoichiometry and different reaction-boundary slopes in the activity-activity diagram. In general, spinels with the highest Zn content occur next to orthopyroxene (ave. 4.9 mol% gahnite in spinels) for which the stability appears to be only slightly affected by this increase in Zn. The greatest decrease in silicate stability is observed in sapphirine. Spinels adjacent to sapphirine contain no more than 1.3 mol% gahnite. The effects of manganese and oxygen fugacity were also examined. Mn increases the stability of garnet due to strong partitioning of Mn into this mineral. It can be inferred using statistical and chemical data that this has some bearing on textural relations in garnet-bearing samples, but the lack of obvious Mn fractionation by other minerals examined makes it impossible to interpret the effects of Mn in the garnet-free samples. Calculated ferric-ferrous ratios in analyzed minerals were examined in an attempt to study the effect of oxygen fugacity on the stabilities of minerals. In the more magnesian compositions, which may correlate with slightly higher fO2 during reactions, spinels should react to form sapphirine, then possibly garnet or orthopyroxene with further silica activity increase. In lower-fO2 environments (perhaps those with higher bulk Fe#), spinel should react directly to form orthopyroxene. The coexistence of magnetite and ilmenohematite dictates T-fO2 conditions very nearly at those of the Hematite-Magnetite buffer. Minor fO2 variations that might have had an effect on silicate-forming reactions would only be recorded by small variations in magnetite and ilmenohematite solid solutions (ulvospinel and ilmenite contents, respectively). These data were not acquired in this study, however, so no definite conclusions could be made. / Master of Science