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101.
Scheidegger C Vo H Koop D Freire J Silva C 《IEEE transactions on visualization and computer graphics》2007,13(6):1560-1567
While there have been advances in visualization systems, particularly in multi-view visualizations and visual exploration, the process of building visualizations remains a major bottleneck in data exploration. We show that provenance metadata collected during the creation of pipelines can be reused to suggest similar content in related visualizations and guide semi-automated changes. We introduce the idea of query-by-example in the context of an ensemble of visualizations, and the use of analogies as first-class operations in a system to guide scalable interactions. We describe an implementation of these techniques in VisTrails, a publicly-available, open-source system. 相似文献
102.
Learning vector quantization with training data selection 总被引:2,自引:0,他引:2
Pedreira CE 《IEEE transactions on pattern analysis and machine intelligence》2006,28(1):157-162
In this paper, we propose a method that selects a subset of the training data points to update LVQ prototypes. The main goal is to conduct the prototypes to converge at a more convenient location, diminishing misclassification errors. The method selects an update set composed by a subset of points considered to be at the risk of being captured by another class prototype. We associate the proposed methodology to a weighted norm, instead of the Euclidean, in order to establish different levels of relevance for the input attributes. The technique was implemented on a controlled experiment and on Web available data sets. 相似文献
103.
We consider weighted finite transducers over arbitrary groups, that is finite transducers having a counter in which, at any
step, a value of the group is stored but no information regarding the content of this counter is available until the computation
is finished. The computation is valid if the counter value is the neutral element of the group. We generalize here some results
from [8] and [17].
Received: 28 January 2001 / 5 June 2001 相似文献
104.
Juan Carlos Gomez Erik Boiy Marie-Francine Moens 《Knowledge and Information Systems》2012,31(1):23-53
This paper reports on email classification and filtering, more specifically on spam versus ham and phishing versus spam classification,
based on content features. We test the validity of several novel statistical feature extraction methods. The methods rely
on dimensionality reduction in order to retain the most informative and discriminative features. We successfully test our
methods under two schemas. The first one is a classic classification scenario using a 10-fold cross-validation technique for
several corpora, including four ground truth standard corpora: Ling-Spam, SpamAssassin, PU1, and a subset of the TREC 2007
spam corpus, and one proprietary corpus. In the second schema, we test the anticipatory properties of our extracted features
and classification models with two proprietary datasets, formed by phishing and spam emails sorted by date, and with the public
TREC 2007 spam corpus. The contributions of our work are an exhaustive comparison of several feature selection and extraction
methods in the frame of email classification on different benchmarking corpora, and the evidence that especially the technique
of biased discriminant analysis offers better discriminative features for the classification, gives stable classification
results notwithstanding the amount of features chosen, and robustly retains their discriminative value over time and data
setups. These findings are especially useful in a commercial setting, where short profile rules are built based on a limited
number of features for filtering emails. 相似文献
105.
106.
Ting Wang Christine Chevallereau Carlos F. Rengifo 《Robotics and Autonomous Systems》2012,60(7):962-977
This paper presents a stable walking control method for a 3D bipedal robot with 14 joint actuators. The overall control law consists of a ZMP (zero moment point) controller, a swing ankle rotation controller and a partial joint angles controller. The ZMP controller guarantees that the stance foot remains in flat contact with the ground. The swing ankle rotation controller ensures a flat foot impact at the end of the swinging phase. Each of these controllers creates 2 constraints on joint accelerations. As a consequence, the partial joint angles controller is implemented to track only 10 independent outputs. These outputs are defined as a linear combination of the 14 joint angles. The most important question addressed in this paper is how this linear combination can be defined in order to ensure walking stability. The stability of the walking gait under closed loop control is evaluated with the linearization of the restricted Poincare map of the hybrid zero dynamics. As a result, the robot can achieve an asymptotically stable and periodic walking along a straight line. Finally, another feedback controller is supplemented to adjust the walking direction of the robot and some examples of the robot steered to walk along different paths with mild curvature are given. 相似文献
107.
This paper addresses the problem of obtaining 3d detailed reconstructions of human faces in real-time and with inexpensive
hardware. We present an algorithm based on a monocular multi-spectral photometric-stereo setup. This system is known to capture
high-detailed deforming 3d surfaces at high frame rates and without having to use any expensive hardware or synchronized light
stage. However, the main challenge of such a setup is the calibration stage, which depends on the lights setup and how they
interact with the specific material being captured, in this case, human faces. For this purpose we develop a self-calibration
technique where the person being captured is asked to perform a rigid motion in front of the camera, maintaining a neutral
expression. Rigidity constrains are then used to compute the head’s motion with a structure-from-motion algorithm. Once the
motion is obtained, a multi-view stereo algorithm reconstructs a coarse 3d model of the face. This coarse model is then used
to estimate the lighting parameters with a stratified approach: In the first step we use a RANSAC search to identify purely
diffuse points on the face and to simultaneously estimate this diffuse reflectance model. In the second step we apply non-linear
optimization to fit a non-Lambertian reflectance model to the outliers of the previous step. The calibration procedure is
validated with synthetic and real data. 相似文献
108.
Arturo J. Fernández Carlos J. Pérez-González 《Computational statistics & data analysis》2012,56(3):719-731
Assuming that the probability of obtaining a defective unit in a production process, p, is not constant, a versatile methodology is presented for determining optimal failure-censored reliability sampling plans for log-location-scale lifetime models. The optimization procedure to decide the acceptability of a product is usually sufficiently accurate for the most widely used parametric lifetime models, such as the Weibull and lognormal distributions, and fairly robust to small deviations in the prior knowledge. Moreover, lower and upper bounds on the optimal sample size, and the corresponding acceptance constants, are derived in closed-forms. The proposed approach extends the traditional sampling plans to those cases in which appreciable prior information on p exists, and also allows the analyst the flexibility to delimitate the range of p and to incorporate into the reliability analysis prior impartiality between the producer and the consumer. In addition, the practitioners may achieve substantial savings in sample size, better information on the production process and better assessment of the true producer and consumer risks. An example related to the acceptability of a certain kind of gyroscope is included for illustrative purposes. Various practical prior distributions are considered to describe the random fluctuations in the proportion defective. 相似文献
109.
A class of Lyapunov functions is proposed for discrete-time linear systems interconnected with a cone bounded nonlinearity. Using these functions, we propose sufficient conditions for the global stability analysis, in terms of linear matrix inequalities (LMI), only taking the bounded sector condition into account. Unlike frameworks based on the Lur’e-type function, the additional assumptions about the derivative or discrete variation of the nonlinearity are not necessary. Hence, a wider range of cone bounded nonlinearities can be covered. We also show that there is a link between global stability LMI conditions based on this new Lyapunov function and a transfer function of an auxiliary system being strictly positive real. In addition, the novel function is considered in the local stability analysis problem of discrete-time Lur’e systems subject to a saturating feedback. A convex optimization problem based on sufficient LMI conditions is formulated to maximize an estimate of the basin of attraction. Another specificity of this new Lyapunov function is the fact that the estimate is composed of disconnected sets. Numerical examples reveal the effectiveness of this new Lyapunov function in providing a less conservative estimate with respect to the quadratic function. 相似文献
110.
Antonio Fernández-Caballero María T. López José Carlos Castillo 《Expert systems with applications》2012,39(4):4032-4043
In this paper text segmentation in generic displays is proposed through learning the best binarization values for a commercial optical character recognition (OCR) system. The commercial OCR is briefly introduced as well as the parameters that affect the binarization for improving the classification scores. The purpose of this work is to provide the capability to automatically evaluate standard textual display information, so that tasks that involve visual user verification can be performed without human intervention. The problem to be solved is to recognize text characters that appear on the display, as well as the color of the characters’ foreground and background. The paper introduces how the thresholds are learnt through: (a) selecting lightness or hue component of a color input cell, (b) enhancing the bitmaps’ quality, and (c) calculating the segmentation threshold range for this cell. Then, starting from the threshold ranges learnt at each display cell, the best threshold for each cell is gotten. The input and output data sets for testing the algorithms proposed are described, as well as the analysis of the results obtained. 相似文献