A high voltage power supply for the AE-C and D low energy electron experiment

A description is given of the electrical and mechanical design and operation of high voltage power supplies for space flight use. The supply was used to generate the spiraltron high voltage for low energy electron experiment on AE-C and D. Two versions of the supply were designed and built; one design is referred to as the low power version (AE-C) and the other as the high power version (AE-D). Performance is discussed under all operating conditions

Fast and Robust Recursive Algorithms for Separable Nonnegative Matrix Factorization

In this paper, we study the nonnegative matrix factorization problem under the separability assumption (that is, there exists a cone spanned by a small subset of the columns of the input nonnegative data matrix containing all columns), which is equivalent to the hyperspectral unmixing problem under the linear mixing model and the pure-pixel assumption. We present a family of fast recursive algorithms, and prove they are robust under any small perturbations of the input data matrix. This family generalizes several existing hyperspectral unmixing algorithms and hence provides for the first time a theoretical justification of their better practical performance.Comment: 30 pages, 2 figures, 7 tables. Main change: Improvement of the bound of the main theorem (Th. 3), replacing r with sqrt(r

A power conditioning system for radioisotope thermoelectric generator energy sources

The use of radioisotope thermoelectric generators (RTG) as the primary source of energy in unmanned spacecraft is discussed. RTG output control, power conditioning system requirements, the electrical design, and circuit performance are also discussed

Two Algorithms for Orthogonal Nonnegative Matrix Factorization with Application to Clustering

Approximate matrix factorization techniques with both nonnegativity and orthogonality constraints, referred to as orthogonal nonnegative matrix factorization (ONMF), have been recently introduced and shown to work remarkably well for clustering tasks such as document classification. In this paper, we introduce two new methods to solve ONMF. First, we show athematical equivalence between ONMF and a weighted variant of spherical k-means, from which we derive our first method, a simple EM-like algorithm. This also allows us to determine when ONMF should be preferred to k-means and spherical k-means. Our second method is based on an augmented Lagrangian approach. Standard ONMF algorithms typically enforce nonnegativity for their iterates while trying to achieve orthogonality at the limit (e.g., using a proper penalization term or a suitably chosen search direction). Our method works the opposite way: orthogonality is strictly imposed at each step while nonnegativity is asymptotically obtained, using a quadratic penalty. Finally, we show that the two proposed approaches compare favorably with standard ONMF algorithms on synthetic, text and image data sets.Comment: 17 pages, 8 figures. New numerical experiments (document and synthetic data sets

The sociology of a city in transition: Boston 1980-2000

ABSTRACT This dissertation examines the years 1980-2000 as a sociologically transformative period in Boston's history. The guiding research question is how organized politics and the policies that emerged responded to racial conflict, inequality and economic development, and wholesale change in the city's economic base during this period. The policies of the three governing regimes--the end of Kevin H. White's sixteen-year term, Raymond L. Flynn's nine years in office, and the beginning of Thomas M. Menino's twenty-year mayoralty--are analyzed in the content of these domains to identify the outcomes of several policy agendas that have helped shape life in Boston today. This analysis is in the context of urbanization and urbanism, viewed through the lenses of urban regime, growth machine coalition, progressive city, and government communalism theories. The study utilizes retrospective autoethnography linked with interviews and archival data research. The study found that during the end of the mayoral administration of Kevin White, Boston was in turmoil politically and racially. Political contests centered on growing poverty and inequality and racial unrest in the city. The election of 1983 was a "critical election" both because an African American was in the final runoff and because the two finalists repudiated the growth machine coalition and the racial politics of the past. Flynn's election began the populist transformation of economic policies in Boston to heal racial divisions. After he resigned to become Ambassador to the Vatican, the urban regime of Thomas Menino left intact many of the redistributive policies Flynn enacted; however, it also gradually returned to the growth machine coalition model of economic development, fueling the greatest class and income inequality in Boston's history. In the final analysis, both the policies of each urban regime and the activities of the religious, cultural, business, and neighborhood organizations that comprise city life changed the city in sociologically significant ways. This is the story of Boston 1980-2000, the role of its three mayors during that period, and how the city entered the twenty-first century with its physical decline in part reversed but with issues of race and class remaining significant touchstones

Stratospheric constituent measurements using UV solar occultation technique

The photochemistry of the stratospheric ozone layer was studied as the result of predictions that trace amounts of pollutants can significantly affect the layer. One of the key species in the determination of the effects of these pollutants is the OH radical. A balloon flight was made to determine whether data on atmospheric OH could be obtained from lower resolution solar spectra obtained from high altitude during sunset