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Species associations during the succession of wood-inhabiting fungal communities

FUNGAL ECOLOGY 2014年第0期11卷 17-28页

作者： Ottosson, Elisabet Norden, Jenni Dahlberg, Anders Edman, Mattias Jonsson, Mari Larsson, Karl-Henrik Olsson, Jorgen Penttila, Reijo Stenlid, Jan Ovaskainen, Otso Swedish Univ Agr Sci Dept Forest Mycol & Plant Pathol Uppsala Bioctr SE-75007 Uppsala Sweden Univ Oslo Dept Biosci Microbial Evolut Res Grp NO-0316 Oslo Norway Univ Oslo Nat Hist Museum NO-0318 Oslo Norway Mid Sweden Univ Dept Nat Sci SE-85170 Sundsvall Sweden Swedish Univ Agr Sci Swedish Species Informat Ctr SE-75007 Uppsala Sweden Finnish Forest Res Inst FI-01301 Vantaa Finland Swedish Univ Agr Sci Dept Wildlife Fish & Environm Studies SE-90183 Umea Sweden Univ Helsinki Dept Biosci Metapopulat Res Grp FI-00014 Helsinki Finland

We studied fungal succession in decaying wood by compiling time-series data of fruit body observations. We tested the hypothesis that the presence of a primary species affects the probability of a succeeding species occurring later on the same log. Significant associations were detected for 15 species pairs;these were consistent with earlier findings on co-occurrence patterns in single time surveys. We used enrichment analysis to test if species with particular life-history attributes were more often associated with the occurrence of a succeeding species, or vice versa. White rot fungi and fungi abundant as mycelia were more often associated with the occurrence of succeeding species, compared to brown rot fungi and species with low mycelial abundance. Our results indicate that certain primary species cause priority effects and non-random co-occurrence patterns in the field. These successional patterns are likely to be connected both with substrate modification and species interactions. (C) 2014 Elsevier Ltd and The British Mycological Society. All rights reserved.

关键词： Boreal forest Colonization Community ecology Enrichment analysis Fungal succession Life-history traits linear regression model Norway spruce Priority effects Wood-inhabiting fungi

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Aggregation level matters: evidence from french electoral data

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QUALITY & QUANTITY 2014年第2期48卷 923-938页

作者： Russo, Luana Beauguitte, Laurent 98 Rue Univ F-75007 Paris France

This paper, issued from the Cartelec project, raises a methodological issue regarding ecological inference. Studying abstention in two recent French elections in the Parisian agglomeration, a linear regression is launched on three different levels of aggregation: from the finest one (polling station), through cities, to electoral districts (circonscriptions). Tests on multicollinearity clearly indicate that employing the finest level of aggregation allows more variables to be significant, enhances the explanatory power of the model, and improves the collinearity amongst the dependent variables.

关键词： Abstention Ecological inference linear regression model Multicollinearity Parisian agglomeration Political geography

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Confidence intervals for low dimensional parameters in high dimensional linear models

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JOURNAL OF THE ROYAL STATISTICAL SOCIETY SERIES B-STATISTICAL METHODOLOGY 2014年第1期76卷 217-242页

作者： Zhang, Cun-Hui Zhang, Stephanie S. Rutgers State Univ Piscataway NJ 08854 USA Columbia Univ New York NY USA

The purpose of this paper is to propose methodologies for statistical inference of low dimensional parameters with high dimensional data. We focus on constructing confidence intervals for individual coefficients and linear combinations of several of them in a linear regression model, although our ideas are applicable in a much broader context. The theoretical results that are presented provide sufficient conditions for the asymptotic normality of the proposed estimators along with a consistent estimator for their finite dimensional covariance matrices. These sufficient conditions allow the number of variables to exceed the sample size and the presence of many small non-zero coefficients. Our methods and theory apply to interval estimation of a preconceived regression coefficient or contrast as well as simultaneous interval estimation of many regression coefficients. Moreover, the method proposed turns the regression data into an approximate Gaussian sequence of point estimators of individual regression coefficients, which can be used to select variables after proper thresholding. The simulation results that are presented demonstrate the accuracy of the coverage probability of the confidence intervals proposed as well as other desirable properties, strongly supporting the theoretical results.

关键词： Confidence interval High dimension linear regression model p-value Statistical inference

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Investigating Defect Prediction models for Iterative Software Development When Phase Data is Not Recorded Lessons Learned

Investigating Defect Prediction Models for Iterative Softwar...

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9th International Conference on Evaluation of Novel Approaches to Software Engineering (ENASE)

作者： Aydin, Anil Tarhan, Ayca Hacettepe Univ Comp Engn Ankara Turkey

ISBN: (纸本)9789897580307

One of the biggest problems that software organizations encounter is specifying the resources required and the duration of projects. Organizations that record the number of defects and the effort spent on fixing these defects are able to correctly predict the latent defects in the product and the effort required to remove these latent defects. The use of reliability models reported in the literature is typical to achieve this prediction, but the number of studies that report defect prediction models for iterative software development is scarce. In this article we present a case study which predicts the defectiveness of new releases in an iterative, civil project where defect arrival phase data is not recorded. We investigated linear regression model and Rayleigh model one of the statistical reliability model that contain time information, to predict the module level and project level defectiveness of the new releases of an iterative project through the iterations. The models were created by using 29 successive releases for the project level and 15 successive releases for the module level defect density data. This article explains the procedures that were applied to generate the defectiveness models and the lessons learned from the studies.

关键词： Defect Prediction Iterative Software Development Rayleigh model linear regression model Lessons Learned

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linear regression for Automatic Image Annotation 9

Linear regression for Automatic Image Annotation

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9th IEEE International Conference on Computer Science and Education (ICCSE)

作者： Zhang, Ning Shenyang Radio & Televis Univ Coll Informat Engn Shenyang 110003 Liaoning Peoples R China

ISBN: (纸本)9781479929511

Automatic image annotation is an effective technology to enhance the performance of image retrieval. In order to annotate image accurately, we introduce a novel annotation method based on regression models. Firstly, with different independent views, both the visual and the textual modalities are efficiently represented in a continuous vector space form, and are named by the visual blob vector and the semantic description vector, respectively. Then, instead of mining the association probability model between images and keywords, the task of annotation is reformulated into fitting a rigorous mapping construction between the visual blob vectors and the semantic description vectors using a method based on least squares estimation. Compared with the previous annotation methods, the merits of the proposed method are conceptually simple, computationally efficient, scalable for huge amount of images and do not require any priori knowledge about images and keywords for modeling the task of annotation. With a highly accurate approximation function, the experimental results demonstrate the improvement of annotation performance.

关键词： Automatic image annotation linear regression model Association probability model

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A Spatial Scan Statistic on Trends

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JOURNAL OF STATISTICAL THEORY AND PRACTICE 2014年第2期8卷 176-191页

作者： Luo, Jun DigitCompass LLC 3338 N Chatham Rd F Ellicott City MD 21042 USA

Spatial scan statistics have been widely researched for detecting geographic clusters of heterogeneous rates. This article explores a relevant field of detecting clusters of different relationships of quantities, for instance, trends of logarithmic values of age-adjusted rates over a period of time. The proposed method distinguishes itself by detecting geographic clusters with higher trends of rates. A typical problem is whether the curves of logarithmic values of age-adjusted rates of geographic units are parallel (i.e., have the same slopes or trends). If not, then where are the clusters with higher trends? A likelihood ratio is employed for deriving a spatial scan statistic that is proposed for (1) evaluation of global geographic heterogeneity of trends and (2) detecting clusters of high trends. The method is illustrated on trends of cancer mortality rates of states in the United States. The data used in this article are publicly available at http://***/seerstat/.

关键词： Spatial scan statistic Trend linear regression model Likelihood ratio Heterogeneity Geographic unit Cluster detection

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A revisit to efficient forecasting in linear regression models

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JOURNAL OF MULTIVARIATE ANALYSIS 2013年第1期114卷 161-170页

作者： Shalabh Indian Inst Technol Dept Math & Stat Kanpur 208016 Uttar Pradesh India

This paper deals with the improved forecasts for the values of the study variable in linear regression models utilizing the minimum risk approach. It considers the simultaneous forecasting of actual and average values of the study variable and reports the performance properties of the classical unbiased forecasts and two biased forecasts with respect to the criteria of the bias vector, mean squared error matrix and forecast risk, employing the small disturbance asymptotic theory. (C) 2012 Elsevier Inc. All rights reserved.

关键词： linear regression model Simultaneous forecasting Least squares estimator Stein-rule estimator Small disturbance asymptotic theory Minimum risk approach

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A Bayesian Approach for Estimation of linear-regression LPV models 53

A Bayesian Approach for Estimation of Linear-Regression LPV ...

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53rd IEEE Annual Conference on Decision and Control (CDC)

作者： Golabi, Arash Meskin, Nader Toth, Roland Mohammadpour, Javad Qatar Univ Coll Engn Dept Elect Engn POB 2713 Doha Qatar Eindhoven Univ Technol Dept Elect Engn Control Syst Grp Dept NL-5600 MB Eindhoven Netherlands Univ Georgia Complex Syst Controls Lab Coll Engn Athens GA 30602 USA

ISBN: (纸本)9781467360906

In this paper, a Bayesian framework for identification of linear parameter-varying (LPV) models with finite impulse response (FIR) dynamic structure is introduced, in which the dependency structure of LPV system on the scheduling variables is identified based on a Gaussian Process (GP) formulation. Using this approach, a GP is employed to describe the distribution of the coefficient functions, that are dependent on the scheduling variables, in LPV linear-regression models. First, a prior distribution over the nonlinear functions representing the unknown coefficient dependencies of the model to be estimated is defined;then, a posterior distribution of these functions is obtained given measured data. The mean value of the posterior distribution is used to provide a model estimate. The approach is formulated with both static and dynamic dependency of the coefficient functions on the scheduling variables. The properties and performance of the proposed method are evaluated using illustrative examples.

关键词： linear parameter-varying systems system identification Bayesian method Gaussian process linear regression model

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Flux based pedestrian flow estimation in occluded scenes

Flux based pedestrian flow estimation in occluded scenes

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IEEE International Symposium on Broadband Multimedia Systems and Broadcasting (BMSB)

作者： Lu, Xiaowei Yang, Hua Su, Hang Wu, Shuang Shanghai Jiao Tong Univ Inst Image Commun & Network Engn Shanghai Key Lab Digital Media Proc & Transmiss Shanghai 200030 Peoples R China

ISBN: (纸本)9781479916542

Pedestrian flow estimation is a vital issue in video surveillance. Inspired by fluid mechanics we proposed to model the pedestrian flow as time-dependent fluid, and estimate the pedestrian flow using flux. Firstly, optical flow is used to construct the motion vector field. Then, we compute the inside and outside flux components within fixed areas to estimate the pedestrian flow in different direction. In addition, we propose an edge-interval algorithm to estimate the occlusion index, which contribute to the flux. Consequently, the pedestrian flow is estimated using linear regression by combining the flux and occlusion index within a specific area. Experiments on PETS2009 and real videos, which include the occluded scenes, elucidate the good performance in pedestrian flow estimation.

关键词： pedestrian flow estimation flux occlusion index linear regression model

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Ambulatory impedance pneumography device for quantitative monitoring of volumetric parameters in respiratory and cardiac applications 41

Ambulatory impedance pneumography device for quantitative mo...

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41st Computing in Cardiology Conference (CinC)

作者： Mlynczak, Marcel C. Niewiadomski, Wiktor Zylinski, Marek Cybulski, Gerard P. Warsaw Univ Technol Fac Mechatron Inst Precis & Biomed Engn Boboli 8 PL-02575 Warsaw Poland Polish Acad Sci Mossakowski Med Res Ctr Warsaw Poland

ISBN: (纸本)9781479943463

Aims: The estimation of respiratory flow and volume parameters is difficult to perform and uncomfortable for the patient during long-term monitoring outside the clinical environment. It is also hard to perform during sleep due to the usage of a facemask. The impedance pneumography (IP) device allows monitoring of breathing activity, estimates the respiratory rate and provides the quantitative measurements of the static and dynamic respiratory parameters, e.g. tidal volume (TV) or peak expiratory flow (PEF). A miniaturized, Holter-type impedance pneumography device, Pneumonitor, with analog output and intrinsic digital memory, was designed and constructed. The system allows long-term assessment of ventilation by measuring changes in thoracic impedance using the tetrapolar method. Methods: The Artificial Patient module was used to check the stability of the amplitude and frequency of the application current (sinusoidal, 100kHz, 250 mu A) and to calibrate the measurements obtained by the IP device by finding the transfer function between voltage and impedance. Impedance values obtained by the IP device from patients were compared those from another bioimpedance measuring device in different electrode placement configurations in patients (for cardiac and respiratory applications). The volume-related impedance signal was also compared with the volume signal calculated from pneumotachometry (PNT). These measurements were conducted in a group of 12 young, healthy volunteers (8 male). Results: The comparison of impedance values from the IP device with those from another one bioimpedance measuring showed high agreement in all tested electrode configurations. High values of determination coefficients (R-2), describing the fit of the linear regression model relating corresponding IP and PNT signals, varied in the range of 0.934 to 0.997 (average: 0.985). However, the differences between average tidal volume parameters (calculated for each subject) derived from IP and PNT are s

关键词： biomedical electrodes biomedical measurement cardiology electric impedance imaging medical signal processing patient monitoring physiological models pneumodynamics regression analysis Holter-type impedance pneumography device ambulatory impedance pneumography device artificial patient module bioimpedance measuring device breathing activity monitoring cardiac activity analysis cardiac applications dynamic respiratory parameters electrode placement configurations impedance pneumography signals linear regression model long-term ventilation assessment pneumonitor pneumotachometry signals respiratory activity analysis respiratory applications respiratory flow estimation static respiratory parameter tetrapolar method thoracic impedance volume-related impedance signal Diseases IP networks Impedance Impedance measurement Lungs Monitoring Voltage measurement

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