13,576 research outputs found

    Rodeo: Sparse Nonparametric Regression in High Dimensions

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    We present a greedy method for simultaneously performing local bandwidth selection and variable selection in nonparametric regression. The method starts with a local linear estimator with large bandwidths, and incrementally decreases the bandwidth of variables for which the gradient of the estimator with respect to bandwidth is large. The method--called rodeo (regularization of derivative expectation operator)--conducts a sequence of hypothesis tests to threshold derivatives, and is easy to implement. Under certain assumptions on the regression function and sampling density, it is shown that the rodeo applied to local linear smoothing avoids the curse of dimensionality, achieving near optimal minimax rates of convergence in the number of relevant variables, as if these variables were isolated in advance

    Species Profiles: Life Histories and Environmental Requirements of Coastal Fishes and Invertebrates (Pacific Southwest): Black, green, and red abalones

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    All abalones belong to the genus Haliotis sensu latu, family Haliotidae. The 75 species known worldwide (Booloot ian et, al. 1962) are anatomically similar and all are adapted for attachment to hard substrates. Seven species are widely distributed along the coast of California (Cox 1962; Mottet 19781, of which several are important in the comercial and sport fisheries of the Pacific Southwest. (PDF has 19 pages.

    Automated fiber placement composite manufacturing: The mission at MSFC's Productivity Enhancement Complex

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    Automated fiber placement is a manufacturing process used for producing complex composite structures. It is a notable leap to the state-of-the-art in technology for automated composite manufacturing. The fiber placement capability was established at the Marshall Space Flight Center's (MSFC) Productivity Enhancement Complex in 1992 in collaboration with Thiokol Corporation to provide materials and processes research and development, and to fabricate components for many of the Center's Programs. The Fiber Placement System (FPX) was developed as a distinct solution to problems inherent to other automated composite manufacturing systems. This equipment provides unique capabilities to build composite parts in complex 3-D shapes with concave and other asymmetrical configurations. Components with complex geometries and localized reinforcements usually require labor intensive efforts resulting in expensive, less reproducible components; the fiber placement system has the features necessary to overcome these conditions. The mechanical systems of the equipment have the motion characteristics of a filament winder and the fiber lay-up attributes of a tape laying machine, with the additional capabilities of differential tow payout speeds, compaction and cut-restart to selectively place the correct number of fibers where the design dictates. This capability will produce a repeatable process resulting in lower cost and improved quality and reliability

    Determinants of Student Retention of Microeconomic Concepts

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    In this study, we examine a variety of individual, institutional, and course-specific factors that influence students' retention of concepts from the microeconomics principles course. Students in 15 upper-division courses in the SUNY-Oswego economics department completed a survey instrument and the TUCE exam at the beginning of the Spring 1999 semester. A regression analysis is used to examine the effect of principles course characteristics on student recall (as measured by TUCE score), controlling for student demographic and ability characteristics. Among the factors examined are the impacts of large-class instruction, writing-intensive curricular, and the time interval since the completion of the principles course. The results suggest that students who have completed a writing-intensive introductory microeconomics course perform significantly less well on the TUCE exam at the start of their upper-division courses than do students who participated in classes that relied on multiple-choice examinations.TUCE; class size; writing requirements; economic education; student performance; multiple choice exams

    Impacts of Energy Development on Secondary Labor Markets: A Study of Seven Western Counties

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    This study attempts to determine key characteristics of these secondary workers in seven counties of four states, and the implications that the results of these surveys have on planning for socioeconomic impact management.Labor and Human Capital, Resource /Energy Economics and Policy,

    Sparse Additive Models

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    We present a new class of methods for high-dimensional nonparametric regression and classification called sparse additive models (SpAM). Our methods combine ideas from sparse linear modeling and additive nonparametric regression. We derive an algorithm for fitting the models that is practical and effective even when the number of covariates is larger than the sample size. SpAM is closely related to the COSSO model of Lin and Zhang (2006), but decouples smoothing and sparsity, enabling the use of arbitrary nonparametric smoothers. An analysis of the theoretical properties of SpAM is given. We also study a greedy estimator that is a nonparametric version of forward stepwise regression. Empirical results on synthetic and real data are presented, showing that SpAM can be effective in fitting sparse nonparametric models in high dimensional data

    Spacecraft Systems Working Group report

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    Issues addressed include: definition of user/commercial/government needs by function; criteria for prioritization of needs; overall criteria for technology assessment; system configuration drivers (key trade studies); space infrastructure interface; and cost drivers (pros and cons of standardization, manufacturing, test, serviceability, and supportability)
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