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Centroid

About: Centroid is a research topic. Over the lifetime, 4110 publications have been published within this topic receiving 53637 citations. The topic is also known as: barycenter (geometry) & geometric center of a plane figure.


Papers
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Journal ArticleDOI
TL;DR: In this paper, the authors prove rigorously that the Fisher-Bhattacharyya mapping does not map the random genetic drift process or its diffusion approximation into one with radial symmetry, and that the initial state of an evolving ensemble can only be unbiasedly estimated from the means of a sample if we weight by the proper divergence times.
Abstract: It has been conjectured that a certain transformation of gene frequency space due to Fisher and Bhattacharyya will map the random genetic drift process, or its diffusion approximation, into one with radial symmetry. This paper proves rigorously that the Fisher-Bhattacharyya mapping does not do this. This implies that the initial state of an evolving ensemble can only be unbiasedly estimated from the means of a sample if we weight by the proper divergence times. If the ensemble is known not to have begun at the centroid of frequency space, the estimate of the initial state vector is not simply the arithmetic average, as symmetry analysis of the Christoffel velocity field shows.

11 citations

Journal ArticleDOI
TL;DR: This paper proves that the energy centre of symmetric window function is the coordinate origin in discrete spectrum analysis and the correction formula of frequency, amplitude and phase can be obtained using this character.
Abstract: This paper proves that the energy centre of symmetric window function is the coordinate origin in discrete spectrum analysis. The correction formula of frequency, amplitude and phase can be obtained using this character. Simulation demonstrates that this method can correct averaged power spectrum directly with simple algorithm and fast processing speed, and the interference of negative or narrow interval frequencies has little influence on correction precision. This method is suitable for all kinds of symmetric window. But it is not suited with dense frequencies signal or continuous spectrum.

11 citations

Journal ArticleDOI
TL;DR: Experimental results show that the system can be used for the high-precision real-time measurement of hole on motorcycle frame and the proposed method can not only improve the measurement speed and precision, but also reduce the measurement error.
Abstract: A high-precision vision detection and measurement system using mobile robot is established for the industry field detection of motorcycle frame hole and its diameter measurement The robot path planning method is researched, and the non-contact measurement method with high precision based on visual digital image edge extraction and hole spatial circle fitting is presented The Canny operator is used to extract the edge of captured image, the Lagrange interpolation algorithm is utilized to determine the missing image edge points and calculate the centroid, and the least squares fitting method is adopted to fit the image edge points Experimental results show that the system can be used for the high-precision real-time measurement of hole on motorcycle frame The absolute standard deviation of the proposed method is 0026 7 mm The proposed method can not only improve the measurement speed and precision, but also reduce the measurement error

11 citations

Journal ArticleDOI
TL;DR: This paper proposes a new measurement model using a skew normal distribution and a variational Bayesian approach is derived to recursively estimate the kinematic state, and the extension through convergent iterations, and shows that the proposed algorithms outperform the existing random matrix methods when measurement distributions are skewed.
Abstract: For extended object tracking, the random matrix approach is a computationally efficient framework that is capable of estimating the kinematic state, and extension of the object jointly, and thus is gaining momentum in recent years. Existing random matrix approaches have an underlying assumption that scatter centers are symmetrically distributed around the centroid. In many real scenarios, however, they are often distributed on particular portions of the object since these parts reflect more radar energy, and measurement distributions over an object are skewed. To effectively describe such a phenomenon, this paper proposes a new measurement model using a skew normal distribution. Based on the proposed model, a variational Bayesian approach is derived to recursively estimate the kinematic state, and the extension through convergent iterations. The resultant algorithm inherits the simplicity of the random matrix approach. To cope with the possible abrupt change of kinematic state, extension, and measurement distribution over an object (especially the skewness) when a target maneuvers, a multiple model approach is presented in the information theoretic interacting multiple model framework. Effectiveness of the proposed algorithms is evaluated using simulated data, and real experimental data. Results show that the proposed algorithms outperform the existing random matrix methods when measurement distributions are skewed.

11 citations

Journal ArticleDOI
Seogjoo Jang1
TL;DR: The formulation of path-integral centroid dynamics is extended to the quantum dynamics of density operators evolving from general initial states by means of the nonequilibrium projection operator technique and it is shown that the new formulation provides a basis for applying the method ofcentroid dynamics to nonequ equilibrium situations and that it allows the derivation of new formal relations.
Abstract: The formulation of path-integral centroid dynamics is extended to the quantum dynamics of density operators evolving from general initial states by means of the nonequilibrium projection operator technique. It is shown that the new formulation provides a basis for applying the method of centroid dynamics to nonequilibrium situations and that it allows the derivation of new formal relations, which can be useful in improving current equilibrium centroid dynamics methods. A simple approximation of uniform relaxation for the unprojected portion of the Liouville space propagator leads to a class of practically solvable equations of motion for the centroid variables, but with an undetermined parameter of relaxation. This new class of equations encompasses the centroid molecular-dynamics (CMD) method as a limiting case, and can be applied to both equilibrium and nonequilibrium situations. Tests for the equilibrium dynamics of one-dimensional model systems demonstrate that the new equations with appropriate choice of the relaxation parameter are comparable to the CMD method.

11 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023492
20221,001
2021184
2020202
2019269
2018271