Results of TC-1 boost pump icing tests in the space power facility

A series of tests were conducted in the space power facility to investigate the failure of the Centaur oxidizer boost pump during the Titan/Centaur proof flight February 11, 1974. The three basic objectives of the tests were: (1) demonstrate if an evaporative freezing type failure mechanism could have prevented the pump from operating, (2) determine if steam from the exhaust of one of the attitude control engine could have entered a pump seal cavity and caused the failure, and (3) obtain data on the heating effects of the exhaust plume from a hydrogen peroxide attitude control engine

Periodic solutions for a class of nonlinear partial differential equations in higher dimension

We prove the existence of periodic solutions in a class of nonlinear partial differential equations, including the nonlinear Schroedinger equation, the nonlinear wave equation, and the nonlinear beam equation, in higher dimension. Our result covers cases where the bifurcation equation is infinite-dimensional, such as the nonlinear Schroedinger equation with zero mass, for which solutions which at leading order are wave packets are shown to exist.Comment: 34 page

A search for variable white dwarfs in large area time domain surveys: a pilot study in SDSS Stripe 82

We present a method to reliably select variable white dwarfs from large area time domain surveys and apply this method in a pilot study to search for pulsating white dwarfs in the Sloan Digital Sky Survey Stripe 82. From a sample 400 high-confidence white dwarf candidates, we identify 24 which show significant variability in their multi-epoch Stripe 82 data. Using colours, we further selected a sample of pulsating white dwarf (ZZ Ceti) candidates and obtained high cadence follow up for six targets. We confirm five of our candidates as cool ZZ Cetis, three of which are new discoveries. Among our 24 candidates we also identify: one eclipsing binary, two magnetic white dwarfs and one pulsating PG1159 star. Finally we discuss the possible causes for the variability detected in the remaining targets. Even with sparse multi-epoch data over the limited area of Stripe 82, we demonstrate that our selection method can successfully identify various types of variable white dwarfs and efficiently select high-confidence ZZ Ceti candidates.Comment: Accepted for publication in MNRAS, 14 pages, 11 figure

Resummation of perturbation series and reducibility for Bryuno skew-product flows

We consider skew-product systems on T^d x SL(2,R) for Bryuno base flows close to constant coefficients, depending on a parameter, in any dimension d, and we prove reducibility for a large measure set of values of the parameter. The proof is based on a resummation procedure of the formal power series for the conjugation, and uses techniques of renormalisation group in quantum field theory.Comment: 30 pages, 12 figure

Localized exciton-polariton modes in dye-doped nanospheres: a quantum approach

We model a dye-doped polymeric nanosphere as an ensemble of quantum emitters and use it to investigate the localized exciton-polaritons supported by such a nanosphere. By determining the time evolution of the density matrix of the collective system, we explore how an incident laser field may cause transient optical field enhancement close to the surface of such nanoparticles. Our results provide further evidence that excitonic materials can be used to good effect in nanophotonics.Comment: 16 pages, 4 figure

Power computation for the triboelectric nanogenerator

We consider, from a mathematical perspective, the power generated by a contact-mode triboelectric nanogenerator, an energy harvesting device that has been well studied recently. We encapsulate the behaviour of the device in a differential equation, which although linear and of first order, has periodic coefficients, leading to some interesting mathematical problems. In studying these, we derive approximate forms for the mean power generated and the current waveforms, and describe a procedure for computing the Fourier coefficients for the current, enabling us to show how the power is distributed over the harmonics. Comparisons with accurate numerics validate our analysis

Stratigraphy, sedimentation and structure of the upper Cherokee and lower Marmaton (Pennsylvanian) rocks of Bates County, and portions of Henry and Vernon Counties, Missouri

The major purpose of this dissertation is to describe in detail the stratigraphy of the upper Cherokee and lower Marmaton groups of the Middle Pennsylvanian, Desmoinesian Series in a portion of western Missouri. The stratigraphy of the upper Cherokee and lower Marmaton groups in areas of Kansas west of the project area has been studied by several workers. The most recent contributions have been by Jewett in 1941 and 1945, and by Howe in 1956. Detailed geological mapping also has been completed under the direction of the Missouri Geological Survey in areas to the east of the project area. Most of the work in this area has been in Henry and Johnson Counties and was done by students from the State Universities of Iowa and Missouri. (Henderson, 1956; Smart, 1957; Hover, 1958; Carver, 1959; and Kinsley, 1960). By comparison, very little detailed stratigraphic work has been done in the intervening area of western Missouri where this study is centered. Minor objectives in the order of decreasing importance are (1) to correlate units across the area (2) to describe briefly the major structural features (3) to attempt to determine to what degree, if any, structure has affected sedimentation. This investigation may serve as an example of the feasibility of combining three somewhat complimentary approaches to the study of Pennsylvanian strata - stratigraphy, sedimentation and structure --Abstract, pages 1-2

School/business partnerships : a case study in an urban area.

Advancing technology demands workers who are equipped with the higher-order cognitive skills of analysis and problem-solving. Opportunities for upward mobility are increasingly reserved for those who possess the ability to learn how to learn. Recent studies have shown, however, many of our students do not master these higher-order skills, and they graduate unprepared to meet the challenges of the changing workplace. Although traditional vocational education attempts to prepare students for work, high school shops are devoid of the vitality of real-life worksites. If vocational students became interns in their field, they would have the opportunity to serve as apprentices in the types of real-world problem-solving and decision-making systems they will enter as adult citizens. In order to create this environment for hands-on experiences, I initiated a school/business collaboration between the Culinary Arts Department of a large, urban vocational/technical high school and a large food services organization and reported the outcome of my efforts in the form of a case study. Throughout the process of establishing the partnership, I kept detailed fieldnotes and journals, which later provided the basis for analysis and assessment of the collaborative experience. Through interviews with student interns, the director of food services in the partner corporation, the culinary arts teacher, and the coordinator of cooperative education, I have attempted to examine the school/business partnership program from several viewpoints. Student interns reported their experience in the corporation made them feel independent and mature. Their supervisor noted employees enjoyed taking the students under their wings. The Culinary Arts teacher and co-op coordinator agreed the partnership program cultivated essential life skills in student participants. Analysis of the project from the perspective of Dewey, Rousseau, or Pestalozzi, leads to the conclusion that apprenticeship-type programs, through their experiential nature, can contribute to the development of the kinds of cognitive and personal skills sought by employers in the 1990s. Although school/business partnerships cannot be regarded as cure-alls for the problems in our schools, they can provide young people with opportunities to develop values and skills through meaningful activities in internship or apprenticeship programs. For a summary of the lessons I have learned from this particular partnership, please see the first page of the appendix