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1,327 results on '"Zhang Zhengjun"'

102. Discussion of 'Estimating the historical and future probabilities of large terrorist events' by Aaron Clauset and Ryan Woodard

Author

Cui, Qiurong, Rohe, Karl, and Zhang, Zhengjun

Subjects
Statistics - Applications
Abstract

Discussion of "Estimating the historical and future probabilities of large terrorist events" by Aaron Clauset and Ryan Woodard [arXiv:1209.0089]., Comment: Published in at http://dx.doi.org/10.1214/13-AOAS614F the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org)

Published
2014
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123. Intrinsically Weighted Means of Marked Point Processes

Author

Malinowski, Alexander, Schlather, Martin, and Zhang, Zhengjun

Subjects
Mathematics - Probability, 60G55, 37A50, 37A30
Abstract

For a non-stationary or non-ergodic marked point process (MPP) on $\R^d$, the definition of averages becomes ambiguous as the process might have a different stochastic behavior in different realizations (non-ergodicity) or in different areas of the observation window (non-stationarity). We investigate different definitions for the moments, including a new hierarchical definition for non-ergodic MPPs, and embed them into a family of weighted mean marks. We point out examples of application in which different weighted mean marks all have a sensible meaning. Further, asymptotic properties of the corresponding estimators are investigated as well as optimal weighting procedures., Comment: 25 pages

Published
2012

129. Two-Way Truncated Linear Regression Models with Extremely Thresholding Penalization.

Author

Teng, Hao Yang and Zhang, Zhengjun

Subjects
*REGRESSION analysis, *DATA analysis
Abstract

This article introduces a new type of linear regression model with regularization. Each predictor is conditionally truncated through the presence of unknown thresholds. The new model, called the two-way truncated linear regression model (TWT-LR), is not only viewed as a nonlinear generalization of a linear model but is also a much more flexible model with greatly enhanced interpretability and applicability. The TWT-LR model performs classifications through thresholds similar to the tree-based methods and conducts inferences that are the same as the classical linear model on different segments. In addition, the innovative penalization, called the extremely thresholding penalty (ETP), is applied to thresholds. The ETP is independent of the values of regression coefficients and does not require any normalizations of regressors. The TWT-LR-ETP model detects thresholds at a wide range, including the two extreme ends where data are sparse. Under suitable conditions, both the estimators for coefficients and thresholds are consistent, with the convergence rate for threshold estimators being faster than n . Furthermore, the estimators for coefficients are asymptotically normal for fixed dimension p. It is demonstrated in simulations and real data analyses that the TWT-LR-ETP model illustrates various threshold features and provides better estimation and prediction results than existing models. for this article are available online. [ABSTRACT FROM AUTHOR]

Published
2024
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130. Ag–Au Nanorods for the Diagnosis of Cervical Cancer by Label-Free Serum Surface-Enhanced Raman Scattering.

Author

Zhao, Zhengyuan, Wang, Weipeng, Guo, Rong, Zhao, Xiaofeng, Xie, Xin, Xu, Tongzhou, Zheng, Yuanhao, Xie, Zheng, Liu, Zhanyu, Han, Wenling, Wang, Wei, Luo, Wei, Chen, Guoqiang, and Zhang, Zhengjun

Abstract

Developing cancer screening methods, particularly by Surface-enhanced Raman scattering (SERS) of serum samples, is crucial for early cancer diagnosis, given SERS's high biocompatibility and comprehensive spectra fingerprints. However, development of SERS as a cancer diagnostic tool is impeded by the lack of a high-quality serum database and robust, adaptable diagnostic models. In our study, we optimized SERS active Ag–Au nanorods and serum pretreatment to obtain high-quality spectra from 215 women's serum samples and then normalized the spectra to create a reliable serum database. Quadratic discriminant analysis (QDA) of this database could classify cancer patients from healthy individuals with an accuracy of 91.2%. By the kernel density estimation (KDE) algorithm on QDA scores, we calculated the probability distribution function (PDF) for two groups with which the diagnostic accuracy was significantly enhanced, exemplified by a 139/143 accuracy rate at 90% probability decision threshold. Notably, both PDF and QDA models can be refined iteratively with an increase in database increment. Our findings underscore the potential of label-free serum SERS in noninvasive cancer screening, particularly for distinguishing cervical cancer patients from healthy individuals. [ABSTRACT FROM AUTHOR]

Published
2024
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140. Quotient correlation: A sample based alternative to Pearson's correlation

Author

Zhang, Zhengjun

Subjects
Mathematics - Statistics Theory, 62H20, 62H15, 62G10, 62G20, 62G32, 60G70 (Primary)
Abstract

The quotient correlation is defined here as an alternative to Pearson's correlation that is more intuitive and flexible in cases where the tail behavior of data is important. It measures nonlinear dependence where the regular correlation coefficient is generally not applicable. One of its most useful features is a test statistic that has high power when testing nonlinear dependence in cases where the Fisher's $Z$-transformation test may fail to reach a right conclusion. Unlike most asymptotic test statistics, which are either normal or $\chi^2$, this test statistic has a limiting gamma distribution (henceforth, the gamma test statistic). More than the common usages of correlation, the quotient correlation can easily and intuitively be adjusted to values at tails. This adjustment generates two new concepts--the tail quotient correlation and the tail independence test statistics, which are also gamma statistics. Due to the fact that there is no analogue of the correlation coefficient in extreme value theory, and there does not exist an efficient tail independence test statistic, these two new concepts may open up a new field of study. In addition, an alternative to Spearman's rank correlation, a rank based quotient correlation, is also defined. The advantages of using these new concepts are illustrated with simulated data and a real data analysis of internet traffic., Comment: Published in at http://dx.doi.org/10.1214/009053607000000866 the Annals of Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical Statistics (http://www.imstat.org)

Published
2008
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