نتایج جستجو برای: field effects

تعداد نتایج: 2246129  

Journal: :Management Science 2012
Peter Demerjian Baruch Lev Sarah McVay

W propose a measure of managerial ability, based on managers’ efficiency in generating revenues, which is available for a large sample of firms and outperforms existing ability measures. We find that our measure is strongly associated with manager fixed effects and that the stock price reactions to chief executive officer (CEO) turnovers are positive (negative) when we assess the outgoing CEO a...

2001
William S. Cleveland Lorraine Denby Chuanhai Liu

We describe an approach to building models for data with random effects. The modeling includes both random location effects and random scale effects. The approach consists of a sequence of steps. In each step, model building tools based on certain statistics are used to study the structure of the data and identify or check an aspect of the model; the results of most of the steps are used explic...

Journal: :iranian journal of medical physics 0
seyed ali saiedi zadeh ms.c. in occupational hygiene , tehran university of medical sciences, tehran, iran parvin nassiri professor, occupational health dept., tehran university of medical sciences, tehran, iran hojjat zeraati assistant professor, epidemiology and biostatistics dept.,tehran university of medical sciences, tehran, iran rahmatollah jahangiri assistant professor, school of medicine, army university of medical sciences, tehran, iran

introduction: it has been reported that cardiovascular effects are among the possible health effects of being exposed to extremely low frequency electromagnetic fields (elf emss). material and methods: this study has been conducted to evaluate the long term effects of exposure to magnetic and electric fields on electrocardiogram signal changes. nine power transmission posts having different vol...

پایان نامه :وزارت علوم، تحقیقات و فناوری - دانشگاه تربیت مدرس - دانشکده منابع طبیعی 1391

in this study, the effects of oleothermal modification on physical and mechanical peroperties of fir wood (abeis sp.) blocks were examined. at first, some blocks of fir wood with 5 × 20 × 120 cm dimensions were prepared. the blocks were treated in soybean oil. the effects of 3 factors such as treatments temperature (180and 200 °c), holding time (12 and 15 h) and initial moisture content of wood...

Effects of the uniform transverse magnetic field on the transient free convective flows of a nanofluid with generalized thermal transport between two vertical parallel plates have been analyzed. The fluid temperature is described by a time-fractional differential equation with Caputo derivatives. Closed form of the temperature field is obtained by using the Laplace transform and fractional deri...

2011
Ovi Bachmann Bernhardt Messner Richard Messnarz

Functional safety standards (ISO 26262, IEC 61508) require a safety life cycle which demands additional design and engineering tasks to be managed. This paper addresses how the existing FMEAs have to be extended and refocused to address and overview signal paths throughout the system. The safety standards require to classify signals with a SIL (Safety Integrity Level) and the higher the SIL the...

2010
R. Harald BAAYEN Petar MILIN

Reaction times (rts) are an important source of information in experimental psychology. Classical methodological considerations pertaining to the statistical analysis of rt data are optimized for analyses of aggregated data, based on subject or item means (c.f., Forster & Dickinson, 1976). Mixedeffects modeling (see, e.g., Baayen, Davidson, & Bates, 2008) does not require prior aggregation and ...

2009
John D. Kloke Joseph W. McKean

Rank-Based methods for iid linear models have been developed over the past 30 years. However, little work has been done in the area of mixed models. In this paper, we discuss a transformation approach to modeling a particular mixed model: one with an arbitrary number of fixed effects and covariates but only one random effect. Discussion of the asymptotic theory is given and the results of a sim...

Journal: :J. Multivariate Analysis 2012
James O. Chipperfield David G. Steel

This paper considers the problem of estimating fixed effects, random effects and variance components for the multi-variate random effects model with complete and incomplete data. It also considers making inference about the fixed and random effects, a problem which requires careful consideration of the choice of degrees of freedom to use in confidence intervals. This paper uses the EM algorithm...

2010
Barry L. Bayus Tarun Kushwaha Raffaele Conti Susan Cohen

Several organizations have developed online crowdsourcing platforms that tap into the “wisdom” (creative ideas for new products and services) of a large “crowd’ of non-experts (consumers). The crowdsourcing model seems very attractive because consumers are intrinsically motivated to freely contribute their creative ideas, but little is known about the effectiveness of these approaches. Two year...

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