Probabilistic Analysis of Large-Scale Composite Structures Using the IPACS Code

An investigation was performed to ascertain the feasibility of using IPACS (Integrated Probabilistic Assessment of Composite Structures) for probabilistic analysis of a composite fan blade, the development of which is being pursued by various industries for the next generation of aircraft engines. A model representative of the class of fan blades used in the GE90 engine has been chosen as the structural component to be analyzed with IPACS. In this study, typical uncertainties are assumed in the level, and structural responses for ply stresses and frequencies are evaluated in the form of cumulative probability density functions. Because of the geometric complexity of the blade, the number of plies varies from several hundred at the root to about a hundred at the tip. This represents a extremely complex composites application for the IPACS code. A sensitivity study with respect to various random variables is also performed

Change in Academic Motivation at WPI

This project analyzed the change in academic motivation for 200 students from WPI based on data obtained from the Wabash National Study of Liberal Arts Education (WNS). This report identified factors which influence a student\u27s change in academic motivation and examined the validity of the Academic Motivation Scale in the WNS. Academic motivation decreased over freshman year in these 200 students. It decreased further in the 17 students who retook the scale in 2011. Male students were more likely to decrease in academic motivation than female students. There was a relationship between the change in academic motivation and student-faculty interactions. Intrinsic motivation in the 200 students had a significantly greater decrease than extrinsic motivation

Hearing in cetaceans : from natural history to experimental biology

Author Posting. © The Author(s), 2012. This is the author's version of the work. It is posted here by permission of Elsevier for personal use, not for redistribution. The definitive version was published in Advances in Marine Biology 63, edited by Michael Lesser, :197-246. Academic Press (Elsevier), 2013. ISBN: 9780123942821. doi:10.1016/B978-0-12-394282-1.00004-1Sound is the primary sensory cue for most marine mammals, and this is especially true for cetaceans. To passively and actively acquire information about their environment, cetaceans have perhaps the most derived ears of all mammals, capable of sophisticated, sensitive hearing and auditory processing. These capabilities have developed for survival in an underwater world where sound travels five times faster than in air, and where light is quickly attenuated and often limited at depth, at night, and in murky waters. Cetacean auditory evolution has capitalized on the ubiquity of sound cues and the efficiency of underwater acoustic communication. The sense of hearing is central to cetacean sensory ecology, enabling vital behaviors such as locating prey, detecting predators, identifying conspecifics, and navigating. Increasing levels of anthropogenic ocean noise appears to influence many of these activities. Here we describe the historical progress of investigations on cetacean hearing, with a particular focus on odontocetes and recent advancements. While this broad topic has been studied for several centuries, new technologies in the last two decades have been leveraged to improve our understanding of a wide range of taxa, including some of the most elusive species. This paper addresses topics including how sounds are received, what sounds are detected, hearing mechanisms for complex acoustic scenes, recent anatomy and physiology studies, the potential impacts of noise, and mysticete hearing. We conclude by identifying emerging research topics and areas which require greater focus.In compiling this review, TAM was supported by the John E. and Anne W. Sawyer Endowed Fund and the Penzance Endowed Fund

Atomic layer deposition and properties of refractory transition metal-based copper-diffusion barriers for ULSI interconnect

textRefractory transition metals have played an important role in the manufacturing of microelectronic devices for interconnect applications including metal contacts, adhesion layers, and diffusion barriers. The diffusion barrier application has become crucial for the integration of copper as the choice conductor in ultra-large scale integrated (ULSI) circuit interconnect. The refractory metal tantalum has been used commercially in previous ULSI technology generations, and atomic layer chemical vapor deposition (ALD) processes for this metal are highly desired for its use in future generations. This dissertation presents surface chemistry and film growth investigations exploring tantalum ALD and an investigation of barrier film adhesion to relevant interconnect surfaces. In-situ surface analysis techniques including X-ray photoelectron spectroscopy (XPS) and temperature programmed desorption (TPD) were used to study the fundamental adsorption behavior of TaCl5, which was used in the first reported Ta ALD process, on a polycrystalline Ta surface. Based upon these results and those of recently published works, a TaF5/Si2H6 precursor chemistry for Ta ALD was proposed. In this method, alternating half-reactions, which, in this case, are the reaction of TaF5 with a Si2H6-treated surface (the TaF5 halfreaction) and the reaction of Si2H6 with a TaF5-treated surface (the Si2H6 halfreaction), are used sequentially and repetitively to deposit a film. The adsorption and half-reactions of these precursors in the range of 303 to 523 K on polycrystalline Ta were studied in ultra-high vacuum using XPS, TPD and secondary ion mass spectrometry. These half-reactions were subsequently used in practice to deposit thin Ta films in a specially designed, research-scale ALD reactor. This is the first non-plasma enhanced method reported to deposit Ta by ALD. Finally, the adhesion properties of similar tungsten carbide thin films to SiO2 and candidate low-permittivity dielectric substrates was characterized by the four-point bend delamination technique.Chemical Engineerin

The Contribution Of The Melanin Pathway To Overall Body Pigmentation Changes During Ontogenesis Of Periplaneta Americana

Pigmentation is one of the most diverse and distinguishable features of insect morphology. The most prominent colors observed in insects are black or brown, whose production is attributed to the melanin pathway. At present, though, the contribution of this pathway to overall body pigmentation throughout ontogenesis is still lacking. To address this question we examined the roles of four key melanin genes (TH, DDC, ebony, and aaNAT), in embryonic and post-embryonic development of Periplaneta americana. Our results show show that while the melanin pathway plays no role during the earliest nymphal stages, it is required during the later stages of development. In addition, each of the four genes contributes in a distinct way to generate full body or region specific pigmentation patterns. Overall, these findings bring novel insight into the insect pigmentation mechanisms and establish Periplaneta as a suitable model for future melanin studies