Different approaches have been proposed to link high cycle fatigue properties to thermal measurements under cyclic loadings, usually referred to as "self-heating tests." This paper focuses on two models whos...
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Different approaches have been proposed to link high cycle fatigue properties to thermal measurements under cyclic loadings, usually referred to as "self-heating tests." This paper focuses on two models whose parameters are tuned by resorting to self-heating tests and then used to predict high cycle fatigue properties. The first model is based upon a yield surface approach to account for stress multiaxiality at a microscopic scale, whereas the second one relies on a probabilistic modelling of microplasticity at the scale of slip-planes. Both model identifications are cost effective, relying mainly on quickly obtained temperature data in self-heating tests. They both describe the influence of the stress heterogeneity, the volume effect and the hydrostatic stress on fatigue limits. The thermal effects and mean fatigue limit predictions are in good agreement with experimental results for in and out-of phase tension-torsion loadings. In the case of fatigue under non-proportional loading paths, the mean fatigue limit prediction error of the critical shear stress approach is three times less than with the yield surface approach. (C) 2010 Elsevier Ltd. All rights reserved.
Background: e-status is a web-based tool able to generate different statistical exercises and to provide immediate feedback to students' answers. Although the use of Information and Communication Technologies (ICT...
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Background: e-status is a web-based tool able to generate different statistical exercises and to provide immediate feedback to students' answers. Although the use of Information and Communication Technologies (ICTs) is becoming widespread in undergraduate education, there are few experimental studies evaluating its effects on learning. Method: All of the students (121) from an introductory course for statistics in dentistry were randomly assigned to use the tool with one of two 6-problem sets, known as types A and B. The primary endpoint was the grade difference obtained in the final exam, composed of two blocks of questions related to types A and B. The exam evaluator was masked to the intervention group. Results: We found that the effect of e-status on the student grade was an improvement of 0.48 points (95% Cl: 0.10-0.86) on a ten-point scale. Among the 94 students who actually employed e-status, the effect size was 0.63 (95% Cl: 0.17-1.10). Conclusions: It is feasible to formally assess the learning effect of an innovative tool. Providing e-status exercises to students has a direct effect on learning numerical operations related to statistics. Further effects on higher cognitive levels still have to be explored. (C) 2010 Elsevier Ltd. All rights reserved.
An argument may be considered sound ("admissible" or "RSA-compliable" in informal logic) if it is well-formed and fulfills a number of reasonable semantic criteria. When agents exchange arguments, ...
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ISBN:
(纸本)9781607506195
An argument may be considered sound ("admissible" or "RSA-compliable" in informal logic) if it is well-formed and fulfills a number of reasonable semantic criteria. When agents exchange arguments, not all incoming arguments are sound. This paper formulates two results. First, it gives lower bounds for the verification rate of incoming arguments, given an estimate of the percentage of incoming sound arguments and a predefined tolerance of error. Second, it prescribes what percentage of incoming arguments must be verified if there is no prescribed error tolerance, but there is a tradeoff between cost of verification and cost of error.
Since the publication of the first edition in 1994, this book has attracted constant interests from readers and is by now regarded as a standard reference for the theory of Dirichlet forms. For the present second edit...
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ISBN:
(数字)9783110218091
ISBN:
(纸本)9783110218084
Since the publication of the first edition in 1994, this book has attracted constant interests from readers and is by now regarded as a standard reference for the theory of Dirichlet forms. For the present second edition, the authors not only revised the existing text, but also added some new sections as well as several exercises with solutions. The book addresses to researchers and graduate students who wish to comprehend the area of Dirichlet forms and symmetric Markov processes.
The material covered in this book involves important and non-trivial results in contemporary probability theory motivated by polymer models, as well as other topics of importance in physics and chemistry. The developm...
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ISBN:
(数字)9781470413842
ISBN:
(纸本)9780821848203
The material covered in this book involves important and non-trivial results in contemporary probability theory motivated by polymer models, as well as other topics of importance in physics and chemistry. The development carefully provides the basic definitions of mutual intersection and self-intersection local times for Brownian motions and the accompanying large deviation results. The book then proceeds to the analogues of these concepts and results for random walks on lattices of $R^d$. This includes suitable integrability and large deviation results for these models and some applications. Moreover, the notes and comments at the end of the chapters provide interesting remarks and references to various related results, as well as a good number of exercises. The author provides a beautiful development of these subtle topics at a level accessible to advanced graduate students.
Markov processes are among the most important stochastic processes for both theory and applications. This book develops the general theory of these processes and applies this theory to various special examples. The in...
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ISBN:
(数字)9781470411756
ISBN:
(纸本)9780821849491
Markov processes are among the most important stochastic processes for both theory and applications. This book develops the general theory of these processes and applies this theory to various special examples. The initial chapter is devoted to the most important classical example—one-dimensional Brownian motion. This, together with a chapter on continuous time Markov chains, provides the motivation for the general setup based on semigroups and generators. Chapters on stochastic calculus and probabilistic potential theory give an introduction to some of the key areas of application of Brownian motion and its relatives. A chapter on interacting particle systems treats a more recently developed class of Markov processes that have as their origin problems in physics and biology.
This is a textbook for a graduate course that can follow one that covers basic probabilistic limit theorems and discrete time processes.
The summation of two harmonic voltage vectors at same frequency is only certain if their amplitudes and phase angles are well known. Therefore, there are many cases where the difference of phase angles between harmoni...
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ISBN:
(纸本)9781424472444
The summation of two harmonic voltage vectors at same frequency is only certain if their amplitudes and phase angles are well known. Therefore, there are many cases where the difference of phase angles between harmonic voltage vectors is unknown. In calculation of the steady state rating of the a.c. harmonic filter equipment, algebraic summation method is often used in determining maximal harmonic level. This summation law is very conservative as it may result in high cost of equipment ratings. Actually, a compromise should be made in taking into account the equipment safety and the risk of overrating as well as excessive costs. Based on uniform distribution of difference in phase angles, the paper provides an algorithm to calculate the probability upon which the magnitude of summation vector of two harmonic voltages may exceed a given value. This result may be applied in passive harmonic filter design in order to cut down the excessive over cost, and may be served as harmonic assessment guidance used in evaluating and setting grid power quality commitment.
This paper introduces an automated tool named Stochastic Quality Function Deployment (SQFD) system, which measures the quality performance of a Design/Build (D/B) contractor. SQFD integrates stochastic simulation mode...
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This paper introduces an automated tool named Stochastic Quality Function Deployment (SQFD) system, which measures the quality performance of a Design/Build (D/B) contractor. SQFD integrates stochastic simulation modeling and analysis techniques into traditional QFD to deal efficiently with the uncertainties in the input data, to support the quality performance measurement that is involved in multi-attribute and multi-participant decision-making, and to predict the variability in the output. D/B construction owners who are in the process of selecting a D/B firm for a project would benefit from SQFD, because the system allows an owner to expeditiously assess the quality performance of potential D/B firms in their bidding list. An example in D/B contractor evaluation is presented to illustrate the functioning of the system. This quantitative method is a significant contribution to the field of quality performance measurement, because (1) SQFD is totally automated, (2) SQFD's reliability is higher than conventional QFD, and (3) SQFD efficiently deals with uncertainties in multi-attribute and multi-participant decision-making, and therefore generates more accurate results. The system helps to improve the D/B project bidding system. (C) 2008 Elsevier B.V. All rights reserved.
A suite of impact experiments was conducted to assess spatial variability in the dynamic properties of tantalum, on length scales of tens of microns to a few millimeters. Two different sample types were used: tantalum...
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A suite of impact experiments was conducted to assess spatial variability in the dynamic properties of tantalum, on length scales of tens of microns to a few millimeters. Two different sample types were used: tantalum processed to yield a uniform refined grain structure (grain size similar to 20 mu m) with a strong axisymmetric (111) crystallo-graphic texture, and tantalum processed to yield an equiaxial structure with grain size similar to 42 mu m. Impact experiments were conducted loading the samples to stress levels from 6 to 12 GPa, which are well above the Hugoniot Elastic Limit (HEL), then pulling the sample into sufficient tension to produce spall. These stress levels were specifically chosen to investigate the spall behavior of tantalum at levels ranging from the incipient spall stage to significantly above the spall strength, focusing on microstructural phenomena. A recently developed spatially resolved velocity interferometer known as the line-imaging VISAR allowed the point-to-point variability of the spall strength to be determined. Specifically, we have been able to determine in real time the nucleation and growth of void defect structures that lead to the eventual spallation or delaminating of the plate. Experiments indicate that the nucleation and growth process is time-dependent and heterogeneous since a time-dependent distribution of defects is measured. This strongly suggests that the spall strength of the material is not a single-valued function. When fitted to Weibull failure statistics, the results indicate a similar mean value and variability for the spall strength of both types of tantalum. The spatial dependence of the material distension of the spalled tantalum is also deduced, in the approximation of uniaxial strain. (C) 2009 Elsevier Ltd. All rights reserved.
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