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Rising demand for improved fuel economy and structural efficiency are the key factors for use of aluminum alloys for light weighting in aerospace industries. Precipitation strengthened 2XXX and 7XXX aluminum alloys are the key aluminum alloys used extensively in aerospace industry. Welding and joining is the critical step in manufacturing of integrated structures. Joining of precipitation strengthened aluminum alloys using conventional fusion welding techniques is difficult and rather undesirable in as it produces dendritic microstructure and porosities which can undermine the structural integrity of weldments. Friction stir welding, invented in 1991, is a solid state joining technique inherently benefitted to reduces the possibility of common defects associated with fusion based welding techniques. Weldability of various 2XXX and 7XXX aluminum alloys via friction stir welding was investigated. Microstructural and mechanical property evolution during welding and after post weld heat treatment was studied using experimental techniques such as transmission electron microscopy, differential scanning calorimetry, hardness testing, and tensile testing. Various factors such as peak welding temperature, cooling rate, external cooling methods (thermal management) which affects the strength of the weldment were studied. Post weld heat treatment of AL-Mg-Li alloy produced joint as strong as the parent material. Modified post weld heat treatment in case of welding of Al-Zn-Mg alloy also resulted in near 100% joint efficiency whereas the maximum weld strength achieved in case of welds of Al-Cu-Li alloys was around 80-85% of parent material strength. Low dislocation density and high nucleation barrier for the precipitates was observed to be responsible for relatively low strength recovery in Al-Cu-Li alloys as compared to Al-Mg-Li and Al-Zn-Mg alloys.

Strengthening, resistant and shielding properties, to name a few, can be achieved by implementing a surface material coating onto an engineering component. Various elements of these compounded parts can augment the functionality of the part, such as, increased life time and more interactive surfaces. Tungsten has proven to be a challenge to plate with other metals, but if done correctly, the results can allow for the cold spray of tungsten. Cold spraying tungsten particles alone provides a challenge because the powder is too hard and instead of adhering, it erodes the surface it is attempting to plate. Coating tungsten in a softer metal, like copper, will allow for the particles to adhere to the surface and create a strengthened and radiation shielded component. It also yields a better surface to electroplate onto in the future, as tungsten itself is hard to plate onto, so the copper layer provides the ability to easily plate other metals. The purpose of this thesis project is to encapsulate tungsten powder within copper, then scale up the process to produce bulk amounts of the material in a batch process. The particles will be encased using an electroplating method, that has been vi turned into a semi-autonomous process for the ease of producing bulk powder. While electroless deposition has previously shown positive results for attaining a uniform coating, making it a semi-batch process for bulk material would have an extreme cost in comparison to electrolytic deposition. The tungsten particles have been successfully enclosed in copper by electrolytic deposition in this set of experimentation using an HF electro-etch pretreatment and ultrasonic agitation during electroplating. Further experimentation will include improved methods of stirring and transferring powder, as the transfer takes too long between the etch and the onset of plating and the stirring method is bulky and reduces the area that can be efficiently plated on.

Spanish settlers brought the precursor to the bassoon, el bajón, to Mexico in the late sixteenth century. Documentation of the bassoon was intermittently from the sixteenth century on, the current playing traditions were not established until the second half of the twentieth century. Bassoon education in Mexico flourished in the 1970's because several bassoonists became expatriates, and chose to live and work in Mexico for the entirety of their careers. Two major pedagogues, Lazar Stoychev and Jerzy Lemiszka paved the way for the current Mexican bassoon community. This dissertation presents a selective lineage of bassoonists who have held positions in major Mexican orchestras and universities since the mid-twentieth century. The purpose of this study is to recognize the contributions these players and teachers have given to the bassoon world. In recent years, Mexican bassoonists have commissioned hundreds of works for the bassoon and this significant achievement has placed the Mexican bassoon community in an upward trajectory. To place these players in proper historical context, a brief history of classical music institutions in Mexico since the sixteenth century is given. This dissertation documents the history and pedagogy of recent bassoonists in Mexico via a cohesive family tree.

As the bassoon has evolved over time, the music written for the instrument has evolved around it, and was many times the catalyst for its evolution. Bassoon music of the seventeenth through early twentieth centuries has defined much of the curricula for bassoon studies, and has established how we consider and experience the bassoon. We experience, write, and consume music in vastly different ways than just a generation ago. Humans use technology for the most basic of tasks. Composers are using the technology of our generation to compose music that is a reflection of our time. This is a significant aspect of art music today, and bassoonists are barely participating in the creation of this new repertoire. Performance practice often considers only the musical score; interactive electronic music regularly goes beyond that. The combination of technological challenges and inexperience can make approaching electroacoustic music a daunting and inaccessible type of music for bassoonists. These issues require a different language to the performance practice: one that addresses music, amplification, computer software, hardware, the collaboration between performer and technology, and often the performer and composer. The author discusses problems that performers face when rehearsing and performing interactive electroacoustic works for bassoon, and offers some solutions.

This paper uses the concept of mimesis to clarify the debate concerning the representation of reality in music. Specifically, this study defines the audio reality effect and the three main practices of realism as a way of understanding mimetic practices in multiple artistic media, in particular regarding the multimedia works of the "Landscape series." After addressing the historical debates concerning mimesis, this study develops a framework for the understanding of mimesis in sound by addressing the writings of Weiss, Baudrillard, Barthes, Deleuze, and Prendergast and by examining mimetic practices in 19th-century European painting and multimedia performance works. The audio reality effect is proposed as a meaningful translation of Roland Barthes' literary reality effect to the sonic realm. The main trends of realist practice are applied to electroacoustic music and soundscape composition using the works and writings of Emmerson, Truax, Wishart, Risset, Riddell, Smalley, Murray Schafer, Fischman, Young, and Field. Lastly, this study mimetically analyzes "2 seconds / b minor / wave" by Michael Pisaro and Taku Sugimoto and the works of the "Landscape series" in order to demonstrate the relevance of mimesis for understanding current musical practice.

This dissertation considers the use of orchestra bells as a solo instrument. I use three examples taken from chamber literature (Drumming by Steve Reich, Why Patterns? by Morton Feldman, and Ave by Franco Donatoni) to demonstrate uses of the instrument in an ensemble setting. I use six solo, unaccompanied orchestra bell pieces (Twelve Bell Canons by Robert Morris, Katarynka by Marta Ptaszyńska, Over by Stuart Saunders Smith, A Little Suite and an Encore Tango by Will Ogdon, Breaks Through by Lafayette Gilchrist, and Bells for New Orleans by Roscoe Mitchell) to illustrate the instrument’s expressive, communicative ability. In the discussion of each piece, I include brief background information, the composer’s musical language in the piece and performance considerations. I interviewed composers of these solo works to complete the research for this document to discuss their musical language and their thoughts on writing for solo orchestra bells.

In comparing oratorio traits across history, three aspects of oratorio were found to be particularly applicable to the creation of "Deborah: A Chamber Oratorio in One Act." These aspects were: the selection of topic and the creation or adaptation of text; the differences between recitative and aria, in form and function; and the level of stylistic diversity within a given work.