A Fast Gradient Method for Nonnegative Sparse Regression with Self Dictionary

A nonnegative matrix factorization (NMF) can be computed efficiently under the separability assumption, which asserts that all the columns of the given input data matrix belong to the cone generated by a (small) subset of them. The provably most robust methods to identify these conic basis columns are based on nonnegative sparse regression and self dictionaries, and require the solution of large-scale convex optimization problems. In this paper we study a particular nonnegative sparse regression model with self dictionary. As opposed to previously proposed models, this model yields a smooth optimization problem where the sparsity is enforced through linear constraints. We show that the Euclidean projection on the polyhedron defined by these constraints can be computed efficiently, and propose a fast gradient method to solve our model. We compare our algorithm with several state-of-the-art methods on synthetic data sets and real-world hyperspectral images

Robust Near-Separable Nonnegative Matrix Factorization Using Linear Optimization

Nonnegative matrix factorization (NMF) has been shown recently to be tractable under the separability assumption, under which all the columns of the input data matrix belong to the convex cone generated by only a few of these columns. Bittorf, Recht, R\'e and Tropp (`Factoring nonnegative matrices with linear programs', NIPS 2012) proposed a linear programming (LP) model, referred to as Hottopixx, which is robust under any small perturbation of the input matrix. However, Hottopixx has two important drawbacks: (i) the input matrix has to be normalized, and (ii) the factorization rank has to be known in advance. In this paper, we generalize Hottopixx in order to resolve these two drawbacks, that is, we propose a new LP model which does not require normalization and detects the factorization rank automatically. Moreover, the new LP model is more flexible, significantly more tolerant to noise, and can easily be adapted to handle outliers and other noise models. Finally, we show on several synthetic datasets that it outperforms Hottopixx while competing favorably with two state-of-the-art methods.Comment: 27 page; 4 figures. New Example, new experiment on the Swimmer data se

Evaluation of primary rumen epithelial cell culture techniques in sheep

Objectives of this study were to determine if the number of cells incubated in primary rumen epithelial cell cultures affects production rates of metabolites and to standardize reporting criteria by obtaining an optimum mode of data expression. Epithelial tissue was excised from five Suffolk x Dorset crossbred sheep and subjected to serial tryptic digestion to isolate cells. Isolated cells were incubated for 90-minutes in 25 mM propionate and 10 mM butyrate at concentrations of 0.5, 1, 5,10, 20 and 40-million cells per flask (total vol. = 3mL). Production of acetoacetate (AcAc), β-hydroxybutyrate (β-HBA), lactate (LAC) and pyruvate (PYR) were measured. Data were expressed as either cell number, cell dry matter or cell total protein alone or per epithelial wet tissue weight, body weight (BW) or metabolic BW to generate twelve different forms of data expression. Coefficients of variation were calculated for all 12 modes of expression. Expressing data per cell number resulted in the lowest variation (P \u3c .01) and data adjusted for metabolic BW had less variation than BW. Acetoacetate concentrations were largest at 0.5-million cells/flask (P \u3c .05) and there were no differences between 1, 5,10 and 20 and only 40 differed from 0.5 and 5-million cells/flask. β-HBA concentrations were largest at 1 and 5-million cells/flask. However, 1 and 5 only differed significantly (P \u3c .05) from 20 and 40-million cells/flask. Lactate and PYR concentrations were largest at 1-million cells/flask, but no significant differences were found. Ratios of β-HBA:AcAc were below one for the 0.5-million cells/flask indicating low mitochondrial redox potentials (P \u3c .05). A suggested range of rumen epithelial cells to include in incubations is 5 to 20-million/flask. This range will minimize the potential for altered metabolite production caused by incubating large cell quantities as well as the experimental error associated with using low cell numbers. When rumen tissue is taken from animals of the same species, size and stage of development, data adjusted by cell number is preferred. However, it is recommended that metabolic BW, cell protein and cell dry matter be included to facilitate future comparison between laboratories and species

Intelligence/Electronic Warfare (IEW) direction-finding and fix estimation analysis report. Volume 2: Trailblazer

An analysis of the direction finding (DF) and fix estimation algorithms in TRAILBLAZER is presented. The TRAILBLAZER software analyzed is old and not currently used in the field. However, the algorithms analyzed are used in other current IEW systems. The underlying algorithm assumptions (including unmodeled errors) are examined along with their appropriateness for TRAILBLAZER. Coding and documentation problems are then discussed. A detailed error budget is presented

Oxygen sorbent

The present invention discloses a novel and unique family of agents which reversibly binds molecular oxygen at room temperature

Wind-Tunnel Calibration and Correction Procedures for Three-Dimensional Models

Detailed methods are presented for determining the corrections to results from wind-tunnel tests of three-dimensional models for the effects of the model-support system, the nonuniform air flow in the tunnel, and the tunnel walls or jet boundaries. The procedures for determining the corrections are illustrated by equations and the required tests are discussed. Particular attention is given to the parts of the procedures dealing with drag measurements. Two general methods that are used for determining and applying the corrections to force tests are discussed. Some discussion is also included of the correction procedures to be used for wake survey tests. The methods described in this report apply only to tests at subcritical speeds. (author

Low-Thrust Assisted Angles-Only Navigation

Tradition spacecraft proximity operations require large and expensive on-board sensors and significant ground support. Relative angle measurements can be obtained from small, simple, and inexpensive on-board sensors, but have not traditionally been used for proximity operation because of difficulty generating rang information. In this thesis it is shown that useful relative range data can be generated provided that the spacecraft is experiencing a small continuous thrust such as would be provided by a low-thrust propulsion system

Finding genetic elements that head to the autistic phenotype

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal