Damping of thermoelastic structures

Report ascertains the effects of thermoelastic damping on the propagation of longitudinal waves in cylindrical rods. Review of results of wave propagation in unbounded elastic solids and in elastic cylinders precedes consideration of thermal modification of elastic properties

Variation and Evolution of Fruit Ripening Traits in Tomato Species

As angiosperm seeds mature within their ovaries, ovary tissue tends to grow and transform itself into fruit, which aids the success of the seeds. Fruits that are fleshy provide numerous ways to aid in the protection and the dispersal of seeds. First, they keep seeds hidden, encased in hard walls, surrounded by poisons and unpalatable compounds, and second, they undergo developmental changes that facilitate seeds’ release. Tomatoes, a model fleshy fruit, have all these protective traits, and over the course of ripening they become the familiar fruit that is a staple crop around the world. The wild relatives of cultivated tomatoes, however, have substantial variation in ripening habits. I characterized several fruit traits and their change during ripening in wild tomato species to get a better understanding of the phenotypic variation that exists in fruits. Acquiring this background for the clade enables further investigation of genes behind these variable traits and inferences of how the traits have evolved. To associate fruit traits with genes and genomic regions for further analysis I grew introgression lines (ILs) stemming from introgressions of small portions of the genome of the tomato clade outgroup Solanum lycopersicoides, in the background of the cultivated tomato, S. lycopersicum. With these lines, I found regions of the genome that are associated with change of fruit firmness during ripening, providing data for further investigation of the genetics behind this trait. I also investigated the genetic basis of ripe fruit color variation by characterizing the gene CYC-B, which produces the enzyme responsible for turning red lycopene into the orange β-carotene, across the tomato clade. My results suggest that regulation of CYC-B has been key to the evolution of different fruit colors across the clade, and that the promoter region of the gene is involved in differentiating a β-carotene accumulating plant from a lycopene accumulating plant. The research performed here enhances our understanding of phenotypic and genotypic variation in an understudied angiosperm organ that can alter how plant species interact with animals around them, contributing to our knowledge of how fruit traits evolve and how they can enable plant success

Guard Your Heart, “by Force, if Necessary”: Faith, Virginity, and Shame in the Evangelical Purity Movement

In the 1990s and 2000s, American evangelical church culture experienced a shift in its sex education methodology. Known as the purity movement, or purity culture, teachings about sex and dating became inextricably linked to fear and shame. Emerging from this movement in 1997 was a 21-year-old named Joshua Harris. According to Harris, it was not enough to declare a life of abstinence if true holiness were to be achieved. As he declared in his purity manifesto I Kissed Dating Goodbye, one needed to completely renounce dating altogether. The book outlines what a pure life looks like for Christian youth with its many rules and accompanying hypothetical scenarios illustrating these rules as though they were parables of the New Testament. Rather than reiterating the message of his contemporaries that dating was to be done carefully, Harris declares that dating itself is the problem and goes so far as to present relationships as irremovable stains on the individual’s heart. In 2004, Brian Dannelly’s film Saved! portrays the same extreme culture surrounding sexuality and faith through archetypal characters and their varied experiences. Some of the teenagers are on the receiving end of shame, others are participating in cultivating a shame culture. The film and Harris’s book share a common thread in that both tell stories about the ethics of purity culture by incorporating its power to generate great shame. Sara Ahmed defines shame as a failure to adhere to the ideal behavior in the presence of a witness that is either a real or imaginary other. Within a Christian context, this shame is easy to generate; God is always watching, therefore the imagined (as in, not physically present) other is the most important other, the other that supposedly determined the ideal in the first place. My project aims to answer the following: How did teenagers become so easy to mobilize as warriors in the purity movement? What brought Joshua Harris to write such an extremist text at the young age of 21? How does Saved! offer a different way to participate in the conversation around sexuality, particularly within a movement that eliminates LGBTQ+ people? What role does American identity play in purity culture, from the national sex education curriculum to the inseparable identities of “American” and “Christian”? How does the intensified responsibility placed on young women as opposed to young men enable a violent, patriarchal culture? Finally, has this movement ended, or has it simply found a new method of performance

Lighthouses as an overlapping boundary between maritime and terrestrial landscapes : how lighthouses served to connect the growing industries of the Keweenaw Peninsula with the world market

Lighthouses are an important part of the industrial heritage of the Keweenaw Peninsula in Michigan. They functioned as an integrated system that facilitated shipping on Lake Superior and supported the growing industry of the Keweenaw Peninsula. For this reason, lighthouses can be considered as an overlapping boundary between the maritime and terrestrial landscapes. As shipping and industry changed, the lighthouse boundary also changed. Changes to the boundary are reflected in the contractors involved in the construction of lighthouses and the decisions they made with the resources, principally building materials and knowledge, which they had at their disposal. The decline of shipping on the Great Lakes due to the increased use of roads and railroads for commerce and transportation and the decline of industry on the Keweenaw due to the decreasing profitability of the mines are reflected in gradual end of lighthouses functioning as a network

Development of Thermoplastic Composite Reinforced Ultra-High Performance Concrete Panels for Impact Resistance

Recent studies investigating the impact performance of ultra-high performance concrete (UHPC) reported a quasi-brittle flexural failure that transitioned to a brittle punching-shear failure as the size of the impact head was reduced. A potential technology to increase the flexural strength and impact resistance of concrete is applying fiber reinforced polymer (FRP) composites to the exterior faces of the beam or slab. In this work, E-glass fiber reinforced thermoplastics were utilized in two different systems to apply reinforcement to UHPC. Thermoplastic materials were chosen over traditional thermoset materials for their unique advantages, such as rapid fabrication, automated manufacturing and the ability to weld to the material. These advantages could create an ideal system for large scale production of UHPC panels with thermoplastic reinforcement for use in protective systems. The two systems investigated were stamped thermoforming and vacuum infusion. For stamped thermoforming, the UHPC, fiber reinforced prepreg tapes and an additional layer of thermoplastic resin were heated then consolidated. Upon cooling the multiple prepreg layers of thermoplastic tapes were formed into a complete laminate, which was completely bonded to the UHPC core. The second system to reinforce the UHPC was vacuum infusion using a two-part liquid thermoplastic resin-system and a woven roving fabric. The impact performance of the thermoplastic composite reinforced UHPC panels was characterized using a combination of drop-weight impact testing and quasi-static testing. After testing it was confirmed that the application of thermoplastic composite skins to UHPC panels improved the impact resistance of the UHPC. Preliminary results showed little or no performance differences between the thermoplastic tapes and the vacuum infused panels. Thermoplastic tape reinforcement may have a fabrication method well suited for automated production, which is an advantage over the labor intensive vacuum infusion procedure. More work must be performed in order to optimize the thermoplastic composite reinforced UHPC panel design for impact resistance

Transition from KPZ to Tilted Interface Critical Behavior in a Solvable Asymmetric Avalanche Model

We use a discrete-time formulation to study the asymmetric avalanche process [Phys. Rev. Lett. vol. 87, 084301 (2001)] on a finite ring and obtain an exact expression for the average avalanche size of particles as a function of toppling probabilities depending on parameters $\mu$ and $\alpha$. By mapping the model below and above the critical line onto driven interface problems, we show how different regimes of avalanches may lead to different types of critical interface behavior characterized by either annealed or quenched disorders and obtain exactly the related critical exponents which violate a well-known scaling relation when $\alpha \ne 2$.Comment: 10 page

Experimental data and model for the turbulent boundary layer on a convex, curved surface

Experiments were performed to determine how boundary layer turbulence is affected by strong convex curvature. The data gathered on the behavior of the Reynolds stress suggested the formulation of a simple turbulence model. Data were taken on two separate facilities. Both rigs had flow from a flat surface, over a convex surface with 90 deg of turning and then onto a flat recovery surface. The geometry was adjusted so that, for both rigs, the pressure gradient along the test surface was zero. Two experiments were performed at delta/R approximately 0.10, and one at weaker curvature with delta/R approximately 0.05. Results show that after a sudden introduction of curvature the shear stress in the outer part of the boundary layer is sharply diminished and is even slightly negative near the edge. The wall shear also drops off quickly downstream. When the surface suddenly becomes flat again, the wall shear and shear stress profiles recover very slowly towards flat wall conditions. A simple turbulence model, which was based on the theory that the Prandtl mixing length in the outer layer should scale on the velocity gradient layer, was shown to account for the slow recovery