Designing, constructing, and testing an X-ray polarimeter

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011.Cataloged from PDF version of thesis.Includes bibliographical references (p. 24).X-ray astronomy has been an important field since its birth 50 years ago. However, Xray polarization measurements have been almost non-existent, especially when compared to the amount of polarimetry being performed in the other bands of the spectrum. One method of filtering a specific energy of polarized X-rays involves reflecting these X-rays off of a correctly tuned multilayer mirror at a specific grazing angle. A design for a small spacecraft incorporating this type of instrument has been proposed, but the effectiveness of using multilayer mirrors as polarization filters has never been tested in a laboratory setting. A design for using an existing X-ray beamline as a means of testing this method was developed. The necessary modifications to both the source and detector end were made, but due to an inability to completely eliminate small misalignments in the system, the full tests of the multilayer mirrors could not be performed. Further research could be performed to identify and correct the cause of the misalignments and continue the evaluation of the multilayer mirrors as a polarimeter.by Kevin P. Jenks.S.B

Direct shear testing of UO₂ sphere-pac nuclear reactor fuel

The design, development, and utilization of a direct shear test apparatus is presented in this thesis. The effectiveness of the device for determining the friction angle stress state parameter is studied. Two materials, alumina and uranium dioxide, were tested. Alumina microspheres were employed in the initial experiments to simulate the behavior of the sphere-pac material. The results of the initial tests justified the use of the mechanism to study the shear strength of uranium dioxide microspheres. Experimental results for the alumina were compared with independent test results and found to be comparable for a similar method of data reduction. However, a preferred method of data reduction is presented which shows a more conservative friction angle value for extrapolation purposes. The experimental results for uranium dioxide are presented and confirmed the adaptability of the direct shear device for friction angle determination

Formalizing Mathematical Knowledge as a Biform Theory Graph: A Case Study

A biform theory is a combination of an axiomatic theory and an algorithmic theory that supports the integration of reasoning and computation. These are ideal for formalizing algorithms that manipulate mathematical expressions. A theory graph is a network of theories connected by meaning-preserving theory morphisms that map the formulas of one theory to the formulas of another theory. Theory graphs are in turn well suited for formalizing mathematical knowledge at the most convenient level of abstraction using the most convenient vocabulary. We are interested in the problem of whether a body of mathematical knowledge can be effectively formalized as a theory graph of biform theories. As a test case, we look at the graph of theories encoding natural number arithmetic. We used two different formalisms to do this, which we describe and compare. The first is realized in ${\rm CTT}_{\rm uqe}$, a version of Church's type theory with quotation and evaluation, and the second is realized in Agda, a dependently typed programming language.Comment: 43 pages; published without appendices in: H. Geuvers et al., eds, Intelligent Computer Mathematics (CICM 2017), Lecture Notes in Computer Science, Vol. 10383, pp. 9-24, Springer, 201

One in the Hand Worth Two in the Bush? Reproductive Effort of Young Males Is Not Affected by the Presence of Adult Males

Reproduction is a costly endeavor, and most large, long-lived, and iteroparous mammals exhibit conservative life-history tactics wherein an individual may forego or abandon a reproduction event for the sake of survival. Nevertheless, risks and benefits associated with reproduction are not equal across males and females, nor across their life. Whereas expenditure for females is associated with rearing young (e.g., lactation), expenditure for males occurs with securing mating opportunities. Young males may be more successful when dominant males are lacking, but it is less clear whether—and at what cost—young males will expend effort when those opportunities arise. We designed an experiment to quantify reproductive effort (e.g., food intake, somatic loss [body mass and fat]) of male white-tailed deer (Odocoileus virginianus) to better understand the reproductive ecology of male ungulates, with an emphasis on determining how adult males (≥4.5 years old) affect timing and extent of reproductive effort expended by yearling males (1. 5 years old). Food intake, hormone levels, body mass, and somatic loss during rut were similar between yearling males that interacted with adult males and those that did not. Somatic loss by all males was greatest during peak estrus of females, but forage intake relative to metabolic body mass for yearling males was nearly twice that of adult males. Testosterone levels were lower for yearling than adult males early in rut and were related negatively to forage intake. Whereas adult males lost 20% (23.5 kg) of body mass and 31% (5.3 percentage points [ppt]) of body fat during the rut, yearling males lost 12% (9.3 kg) of body mass and 22% (4.7 ppt) of body fat. Reproductive effort by young males was not influenced by the presence of adult males, though young males expended less reproductive effort than adults. Instead, reproductive allocation occurred in a state-dependent manner, where pre-season levels of somatic reserves dictated reproductive effort, regardless of age. Like female ungulates, male deer displayed risk sensitive reproductive allocation wherein current reproductive allocation occurred as a function of resources garnered during the prior season and were expended in a way that should have avoided over-investing and creating a tradeoff between reproduction and survival

Dune restoration as a mitigation strategy for the management of coastal hazards

This is a slideshow presented at the conference Conserv-Vision: the next 50 years, held at Hamilton, New Zealand, 2007

Lateral Earth Pressure at Rest and Shear Modulus Measurements on Hanford Sludge Simulants

This report describes the equipment, techniques, and results of lateral earth pressure at rest and shear modulus measurements on kaolin clay as well as two chemical sludge simulants. The testing was performed in support of the problem of hydrogen gas retention and release encountered in the double- shell tanks (DSTs) at the Hanford Site near Richland, Washington. Wastes from single-shell tanks (SSTs) are being transferred to double-shell tanks (DSTs) for safety reasons (some SSTs are leaking or are in danger of leaking), but the available DST space is limited

"Driven to distraction?" Children's experiences of car travel

This is an Author's Accepted Manuscript of an article published in volume, 4, issue 1, pages 59-76 in Mobilities 2009. Copyright @ 2009 Taylor & Francis, available online at: http://www.tandfonline.com/doi/abs/10.1080/17450100802657962.Cars have become increasingly significant features in the lives of many children and adults in the UK and elsewhere. Whilst there is a growing body of research considering how adults experience automobility, that is the increasingly central role of cars within societies, there has been little equivalent research exploring children's perspectives. Drawing upon a variety of methods including personal diaries, photographs, in‐depth interviews and surveys amongst schools within Buckinghamshire and North London, the paper contributes to filling this gap in existing research through exploring how cars are not only journey spaces for children, but are also sites for play, relaxation, homework, companionship, technology and the consumption of commodities. Using a Foucauldian analysis of power, insights into wider familial processes relating to mobility are provided by exploring how cars are sites of conflicting power relations between parents and children. The paper also explores how children's everyday experiences of cars were framed by wider sets of power relations, including car corporations which design and manufacture these spaces, and the role of capital which commodifies everyday activities in cars. In doing so, the paper challenges existing research on automobility for only focusing upon adults' experiences of cars and begins to theorise a more inclusive account of automobility which incorporates children and young people