Results 1 - 10 of 17,396

Pivoted Document Length Normalization

by Amit Singhal, Chris Buckley, Mandar Mitra - SIGIR'96 , 1996
"... Automatic information retrieval systems have to deal with documents of varying lengths in a text collection. Document length normalization is used to fairly retrieve documents of all lengths. In this study, we ohserve that a normalization scheme that retrieves documents of all lengths with similar c ..."
Abstract - Cited by 477 (16 self) - Add to MetaCart
collections, yielding a robust, collectzorz independent normalization technique. We use the idea of pivoting with the well known cosine normalization function. We point out some shortcomings of the cosine function and present two new normalization functions–-pivoted unique normalization and piuotert byte size

Panel Cointegration; Asymptotic and Finite Sample Properties of Pooled Time Series Tests, With an Application to the PPP Hypothesis; New Results. Working paper

by Peter Pedroni , 1997
"... We examine properties of residual-based tests for the null of no cointegration for dynamic panels in which both the short-run dynamics and the long-run slope coefficients are permitted to be heterogeneous across individual members of the panel+ The tests also allow for individual heterogeneous fixed ..."
Abstract - Cited by 529 (13 self) - Add to MetaCart
fixed effects and trend terms, and we consider both pooled within dimension tests and group mean between dimension tests+ We derive limiting distributions for these and show that they are normal and free of nuisance parameters+ We also provide Monte Carlo evidence to demonstrate their small sample size

Ideal spatial adaptation by wavelet shrinkage

by David L. Donoho, Iain M. Johnstone - Biometrika , 1994
"... With ideal spatial adaptation, an oracle furnishes information about how best to adapt a spatially variable estimator, whether piecewise constant, piecewise polynomial, variable knot spline, or variable bandwidth kernel, to the unknown function. Estimation with the aid of an oracle o ers dramatic ad ..."
Abstract - Cited by 1269 (5 self) - Add to MetaCart
Shrink mimics the performance of an oracle for selective wavelet reconstruction as well as it is possible to do so. A new inequality inmultivariate normal decision theory which wecallthe oracle inequality shows that attained performance di ers from ideal performance by at most a factor 2logn, where n

Brain magnetic resonance imaging with contrast dependent on blood oxygenation.

by S Ogawa , T M Lee , A R Kay , D W Tank - Proc. Natl. Acad. Sci. USA , 1990
"... ABSTRACT Paramagnetic deoxyhemoglobin in venous blood is a naturally occurring contrast agent for magnetic resonance imaging (MRI). By accentuating the effects of this agent through the use of gradient-echo techniques in high fields, we demonstrate in vivo images of brain microvasculature with imag ..."
Abstract - Cited by 648 (1 self) - Add to MetaCart
be used to provide in vivo real-time maps of blood oxygenation in the brain under normal physiological conditions. BOLD contrast adds an additional feature to magnetic resonance imaging and complements other techniques that are attempting to provide positron emission tomographylike measurements related

Loopy belief propagation for approximate inference: An empirical study. In:

by Kevin P Murphy , Yair Weiss , Michael I Jordan - Proceedings of Uncertainty in AI, , 1999
"... Abstract Recently, researchers have demonstrated that "loopy belief propagation" -the use of Pearl's polytree algorithm in a Bayesian network with loops -can perform well in the context of error-correcting codes. The most dramatic instance of this is the near Shannon-limit performanc ..."
Abstract - Cited by 676 (15 self) - Add to MetaCart
modification to the update rules in that we normalized both ..\ and 1r messages at each iteration. As Pearl Nodes were updated in parallel: at each iteration all nodes calculated their outgoing messages based on the incoming messages of their neighbors from the pre vious iteration. The messages were said

MonoSLAM: Realtime single camera SLAM

by Andrew J. Davison, Ian D. Reid, Nicholas D. Molton, Olivier Stasse - IEEE Transactions on Pattern Analysis and Machine Intelligence , 2007
"... Abstract—We present a real-time algorithm which can recover the 3D trajectory of a monocular camera, moving rapidly through a previously unknown scene. Our system, which we dub MonoSLAM, is the first successful application of the SLAM methodology from mobile robotics to the “pure vision ” domain of ..."
Abstract - Cited by 490 (26 self) - Add to MetaCart
an active approach to mapping and measurement, the use of a general motion model for smooth camera movement, and solutions for monocular feature initialization and feature orientation estimation. Together, these add up to an extremely efficient and robust algorithm which runs at 30 Hz with standard PC

Layered depth images

by Steven J. Gortler, Li-wei He, Michael F. Cohen , 1997
"... In this paper we present an efficient image based rendering system that renders multiple frames per second on a PC. Our method performs warping from an intermediate representation called a layered depth image (LDI). An LDI is a view of the scene from a single input camera view, but with multiple pix ..."
Abstract - Cited by 456 (29 self) - Add to MetaCart
In this paper we present an efficient image based rendering system that renders multiple frames per second on a PC. Our method performs warping from an intermediate representation called a layered depth image (LDI). An LDI is a view of the scene from a single input camera view, but with multiple

Policy gradient methods for reinforcement learning with function approximation.

by Richard S Sutton , David Mcallester , Satinder Singh , Yishay Mansour - In NIPS, , 1999
"... Abstract Function approximation is essential to reinforcement learning, but the standard approach of approximating a value function and determining a policy from it has so far proven theoretically intractable. In this paper we explore an alternative approach in which the policy is explicitly repres ..."
Abstract - Cited by 439 (20 self) - Add to MetaCart
proportional to the gradient: where α is a positive-definite step size. If the above can be achieved, then θ can usually be assured to converge to a locally optimal policy in the performance measure ρ. Unlike the value-function approach, here small changes in θ can cause only small changes in the policy

Learning Decision Lists

by Ronald L. Rivest , 2001
"... This paper introduces a new representation for Boolean functions, called decision lists, and shows that they are efficiently learnable from examples. More precisely, this result is established for \k-DL" { the set of decision lists with conjunctive clauses of size k at each decision. Since k ..."
Abstract - Cited by 427 (0 self) - Add to MetaCart
This paper introduces a new representation for Boolean functions, called decision lists, and shows that they are efficiently learnable from examples. More precisely, this result is established for \k-DL" { the set of decision lists with conjunctive clauses of size k at each decision. Since

Surface Reconstruction by Voronoi Filtering

by Nina Amenta, Marshall Bern - Discrete and Computational Geometry , 1998
"... We give a simple combinatorial algorithm that computes a piecewise-linear approximation of a smooth surface from a finite set of sample points. The algorithm uses Voronoi vertices to remove triangles from the Delaunay triangulation. We prove the algorithm correct by showing that for densely sampled ..."
Abstract - Cited by 405 (11 self) - Add to MetaCart
surfaces, where density depends on "local feature size", the output is topologically valid and convergent (both pointwise and in surface normals) to the original surface. We describe an implementation of the algorithm and show example outputs. 1 Introduction The problem of reconstructing a
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